The invention relates to the field of laser ranging and can be used in systems for detecting optical and optoelectronic (OE) surveillance equipment in natural conditions and their identification. Before sounding, natural background radiation signals are received, in which the spectral distribution of radiation is measured and the ratio between the intensities of the spectral components at three selected wavelengths is determined. Laser radiation beams are generated at these wavelengths with a beam intensity ratio corresponding to the intensity ratio of the spectral components in the received background radiation. A total beam of laser radiation is formed and reflected laser radiation is probed and received at three wavelengths and in a wide spectral band. The levels of received optical signals are measured and the values ​​of retroreflection indicators are determined for three wavelengths and for a wide band of wavelengths. Based on the indicated values, a spectral portrait of the retroreflectivity index is formed, which is used to detect and recognize optical and OE surveillance equipment. The technical result is to increase the probability of detection and recognition of optical and OE devices and surveillance equipment and determine their belonging to known classes of OE devices. 2 n. and 4 salary f-ly, 1 ill.

Drawings for RF patent 2524450

The invention relates to optical and laser ranging, observation systems in the optical range and quantum electronics.

The invention can be used in surveillance systems to detect optical and optoelectronic (OE) devices and surveillance and aiming equipment, as well as to determine the type of detected optical and OE equipment and their identification.

There is a known method for detecting optical and optoelectronic devices according to RF patent No. 2133485, which consists in probing a controlled volume of space with scanned pulsed laser radiation, receiving optical signals from a given range, converting received signals into a video signal, threshold selection of received signals, probing a volume of space with a fixed frequency, encoding the emitted sequence of laser pulses, detecting an alarm signal. The disadvantages of this method include the low probability of correct detection of funds optical type with simple threshold processing (selection) of a received signal at a fixed wavelength from a controlled volume of space, as well as the impossibility of determining whether a detected optical device belongs to a specific class of optoelectronic type devices, i.e. recognition of the detected object. The second disadvantage of this detection method is its own vulnerability in relation to optical means of detection and recognition of an external observer, because when probing a controlled volume of space (CVS) with pulsed laser radiation at a fixed wavelength, the device implementing the method unmasks itself and can be detected and identified by an external observer searching for and monitoring the radiation irradiating the location of the detection means of this potential third-party observer.

There is a known method for detecting the eyes of people and animals according to RF patent No. 2223516 dated February 10, 2004, which includes irradiating the located volume of space with pulsed scanned radiation in the wavelength range 450-700 μm and determining the eyes by the ratio of the intensities of reflected radiation at two wavelengths - 1 and 2. The disadvantages of this method include the low reliability of the results obtained, the low probability of correctly determining the presence of a given object, and the short range. These disadvantages are due to the lack of determination and compensation of background radiation, which in real conditions can completely change the ratio between the received radiation by 1 and 2, especially with broadband probing radiation. Another disadvantage of this method is its limited application, which excludes the possibility of its use for detection and recognition of a wide class of optical and OE devices.

As a prototype, a method for detecting optical and optoelectronic surveillance equipment was selected according to RF patent No. 2278399.

This method includes probing a controlled volume of space (VSV) with scanned pulsed laser radiation (PL) at a fixed wavelength, receiving the LR reflected from the VSV from a given range, converting the received LR into an electrical signal and threshold processing of the generated electrical signal, generating an alarm signal - a detection signal object based on threshold processing, determining the range to a detected object, receiving signals of natural background radiation from the COP, changing the repetition rate of LR, generating a difference video signal from LR signals and natural background radiation signals and its threshold processing, generating a composite video signal and its conversion into an optical signal for operator observation.

The disadvantages of the prototype method include the low probability and efficiency of correct detection of devices and surveillance equipment optical-electronic type, as well as the impossibility of recognizing detected objects and determining their belonging to OE devices of the corresponding class. These disadvantages are due to the fact that the actual detection of an object - an OE-type device - is carried out through simple threshold processing of the received reflected signal from the COP, i.e. based on exceeding the received pulse signal of a certain set level. In this case, the signal reflected from the OPC, exceeding a fixed threshold, can also be received from a number of objects of natural origin that do not belong to OE-type devices, because the level of the reflected signal at a certain fixed wavelength of laser radiation cannot be used as a reliable criterion for whether a detected object belongs to OE-type devices. Various additive manipulations with the level of background radiation and the formation of difference signals also do not lead to an increase in the probability of correct detection of OE-type devices and means.

As a prototype for a device that implements the method, a device that implements the prototype method was selected.

The new technical result achieved is to increase the probability of detection and recognition of optical and optoelectronic devices and surveillance equipment and determine their belonging to known classes of OE devices. An additional positive effect is also achieved - reducing the possibility of detection of the proposed device by external observers, incl. OE-type detection means.

The specified technical result is achieved as follows.

1. In a method including probing a controlled volume of space (CVS) with scanned pulsed laser radiation (LP) at wavelength 1, receiving reflected LR signals and signals of natural background radiation from the VCR, converting the received LR into an electrical signal, its threshold processing and range determination before the detected OESN,

reception of natural background radiation signals from the COP is carried out before probing the COP, in the received natural background radiation from the COP the spectral distribution of radiation is measured, in the measured spectral distribution the ratio between the intensities W 1 , W 2 , W 3 of the main spectral components of the color gamut of the visible wavelength range is determined, at wavelength 1 and at two additional wavelengths 2, 3, corresponding to the intensities W 1, W 2, W 3 and collectively forming white optical radiation, pulsed LR beams are generated at wavelengths 1, 2, 3 with the beam intensity ratio P 1 , P 2 , P 3 , corresponding to the relationship between the intensities W 1 , W 2 , W 3 of the main spectral components in the spectral distribution of background radiation from the OPC, the total LR beam is formed by optical summation of the beams at wavelengths 1 , 2 , 3 , and it is measured spectral distribution is compared with the spectral distribution of natural radiation from the OPC and adjusted until the ratios of the spectral components of the total LR beam and natural background radiation from the OPC are equal at wavelengths 1, 2, 3, then the OPC is probed with the formed LR beam and received at wavelengths 1, 2, 3 and in a wide spectral band = 3 - 1, after converting the received LR into electrical signals and their threshold processing, the levels of the received optical signals of the LR are measured, the values ​​of the retroreflectivity indicators (SRV) are determined for three wavelengths and for the DA band, using them, a spectral portrait of the PSV of the detected OESN is formed and compared with the PSV data bank; based on the comparison, the final detection of the OESN is carried out and the determination of its belonging to a known type of OESN is carried out (recognition of the OESN).

2. Determination of retroreflectivity indicators (RSI) P i for each of the wavelengths of laser radiation i (i=1, 2, 3) used for illumination of the controlled space (CSC) is carried out in accordance with the following formula:

,

where E i is the level of the received optical signal reflected from the COP at wavelength i (1=1, 2, 3) of the probing COP LI;

The amount of energy (power) of the probing COP LR at wavelength i;

Ni is the divergence of the LR beam at wavelength i (flat angle);

L - measured range to the detected object;

D pr - diameter (actual) of the receiving lens of the device implementing the method;

OMT is the transmission value of the optical-mechanical path of the implementing device;

Atm is the transmission value of the atmospheric path at the corresponding wavelength i.

3. Determination of the retroreflectivity index (RSI) P for a wide band of wavelengths = 3 - 1 probing LR is carried out in accordance with the following formula:

,

where E is the level of the received optical signal reflected from the COP, recorded by the broadband photodetector of the device implementing the method, in a wide wavelength band = 3 - 1;

P is the total amount of energy (power) of the laser probing the COP ;

Ср, , atm ср - averaged over wavelengths 1, 2, 3 the values ​​of the divergence of the laser, the transmission of the optical-mechanical path and the transmission of the atmosphere.

4. In a device for detecting optical and optoelectronic surveillance equipment, containing a scanning unit sequentially placed on the optical axis, a first laser generator operating at the first wavelength 1, a first lens, the optical input of which is connected via an optical mirror to the optical input of the scanning unit, the first a photodetector, the optical input of which is connected to the optical output of the first lens through a first optical filter, a first lens and a second optical mirror, a first information processing unit, the input of which is connected to the output of the first photodetector, a second lens, the optical axis of which is parallel to the optical axis of the scanning unit, an electrical input which is connected to the first information processing unit, the second and third laser generators, three controllable optical filters, an optical combiner, an optical spectrum analyzer, four photoreceiving units, a second information processing unit, a recognition unit, first and second folding mirrors, three photodetectors, three optical filters are introduced , four translucent mirrors and four optical mirrors, as well as four fiber-optic light guides, while the optical input of the optical spectrum analyzer is connected to the optical output of the second lens, the optical output of the optical spectrum analyzer is connected through fiber-optic light guides to the inputs of four photoreceiving units, the outputs of which are connected to to the second information processing unit, the optical input of the optical adder through three controllable optical filters, the translucent and optical mirrors are connected to the corresponding optical outputs of the first, second and third laser generators, the output of the optical adder is connected to the optical input of the scanning unit, and through the first folding mirror, two optical mirrors and the second folding mirror are optically connected to the optical input of the optical spectrum analyzer, the optical output of the first lens is optically connected to the newly introduced second, third and fourth photodetectors through three translucent mirrors, three lenses and three optical filters, the outputs of the second, third and fourth photodetectors are connected to the inputs a first information processing unit, the outputs of which are connected to the recognition unit and a second information processing unit, the outputs of which are connected to the control inputs of the first, second and third laser generators, the first, second and third controlled filters and the first and second folding mirrors.

5. The optical spectrum analyzer is made on the basis of an optical diffraction grating.

6. The recognition unit is made on the basis of a digital electronic computer containing a data block of values ​​of reference portraits of spectral retroreflection indicators (SRV).

Figure 1 shows a block diagram of a device that implements the proposed method, where the following elements are indicated.

1 - Laser generator operating at wavelength 1 (LG)

2; 3 - Laser generators operating at wavelengths 2 and 3

4; 5; 6 - Controllable optical filters

7 - Optical combiner

8 - Scanning block

9 - First lens

10; eleven; 12; 13 - Photodetectors

14; 15; 16; 17 - Lenses

18 - First information processing block

19 - Second lens

20 - Optical spectrum analyzer

21; 22; 23; 24 - Photoreceiving units (FP)

25 - Second information processing block

26 - Translucent mirror

27; 28; 29 - Optical mirrors

30 - First folding mirror

31 - Control unit for the second folding mirror

32 - Control unit for the first folding mirror

33 - Second folding mirror

34; 35 - Optical mirrors

36; 37; 38 - Translucent mirrors

39 - Optical mirror

40; 41; 42; 43 - Optical filters

44 - Recognition block

45 - controlled volume of space (CVS)

46 - optical-electronic device (OED)

47; 48; 49; 50 - fiber optical light guides.

In the restrictive part of the claims for the device there are elements that are essentially and functionally common with the elements of the prototype device, but have different names:

The first information processing unit, the functions of which in the prototype are performed by a video signal processing unit;

The first lens included in the prototype video camera;

The scanning unit, which in the prototype is part of the laser and provides probing of the COP with pulsed laser radiation.

In this case, the second information processing unit is newly introduced and performs new feature processing optical signals from the output of the optical spectrum analyzer 20 (Fig. 1).

The operating principle of the method is as follows.

Using the scanning unit 8 (see Fig. 1), the COP 45 is probed with pulsed LR simultaneously at three wavelengths 1, 2, 3 generated by laser generators (LG) 1, 2, 3. The scanning unit is controlled by signals coming from first information processing block 18.

Before probing the COP LI, the spectral distribution of background radiation from the COP 45 is measured. To do this, using the second lens 19 directed at the COP, natural background radiation is continuously received. The received background radiation is fed to the input of an optical spectrum analyzer 20, which generates the spectral distribution of the received radiation in the form of, for example, a spatial optical distributed signal.

Individual spectral components of the generated spectral spatial distribution with the help of fiber light guides 47÷50 are supplied from the output of the optical spectrum analyzer 20 to the inputs of photodetector blocks 21÷24, which record the levels of background radiation from the COP at wavelengths 1 2 3 - photodetector blocks 21÷23, as well as The level of total background radiation is recorded in the spectral range = 3 - 1 (photodetector unit - 24). Information about the levels of the spectral distribution of background radiation at the specified wavelengths is supplied to the input of the second information processing unit 25. The spectral distribution of background radiation from the COP 45 is measured at three fixed wavelengths 1 2 3, which are selected corresponding to the main components of the color gamut of the visible wavelength range, namely: 1 - corresponds to the wavelength of red, 2 - to the wavelength of green, 3 - to the wavelength of blue. Accordingly, 1 =0.7 µm, 2 =0.54 µm, 3 =0.43 µm.

Currently, laser radiation sources exist for these wavelengths. In the second information processing block 25, based on the signal intensity levels from the outputs of photodetector units 21, 22, 23, the ratio between the intensities W 1 , W 2 , W 3 of the spectral components of background radiation at selected wavelengths 1 2 3 , respectively, is determined. Next, at the moments of generation of laser radiation using laser generators pos. 1, 2, 3, the ratio between the intensities of the generated laser pulses is established, respectively, at wavelengths 1 -P 1 (laser generator 1 in Fig. 1); 2 -P 2 and 3 -P 3, corresponding to the relationship between the intensities of the spectral components at the corresponding wavelengths 1 2 3 in the measured spectral distribution of background radiation from the controlled volume of space KOP 45. In this case, the following relationship is established between the magnitudes (intensities) of laser pulses generated laser generators 1, 2, 3 at wavelengths 1 2 3: P 1 P 2 P 3 and intensities W 1 , W 2 , W 3 of spectral components of background radiation at wavelengths 1 2 3:

The values ​​of laser pulses generated by laser generators pos. 1, 2, 3 are controlled by commands from the second information processing unit 25, received by the laser generators, and generated based on measurements of laser radiation levels from laser generators using photoreceiving units 21-24. Next, optical summation of three laser pulses is carried out - beams of laser radiation generated by laser generators pos. 1, 2, 3 in Fig. 1 using an optical adder 7, which receives laser radiation from the outputs of these laser generators. The generated total laser radiation at the output of the optical combiner 7 contains spectral components at three wavelengths 1 2 3 in a ratio corresponding to the ratio of the spectral components in the background radiation of the COP 45.

Next, the spectral distribution of the generated total beam of laser radiation from the output of the optical combiner 7 is measured and compared with the measured spectral distribution of background radiation from the controlled volume of space. To do this, using the first and second folding mirrors 30 and 33, the generated radiation from the output of the optical combiner 7 is supplied to the input of the optical spectrum analyzer 20, which generates a spatial spectral distribution, which is then recorded at wavelengths 1 2 3 by means of photodetecting units 21-23. Blocks 21-23 similarly record the spectral distribution of background radiation from the COP 45. Block 24 records the total level of radiation in a certain selected wavelength range = 3 - 1. In the second information processing block 25, the spectral distribution of the total LR beam P 11 , P 21 , P 31 is registered (taking into account the attenuation in the optical elements 7, 28, 29, 30, 33, 20, through which the formed LR passes). Next, the measured distribution of intensities (pulse amplitudes) is compared with the previously measured and stored in information block 25 spectral distribution of the intensity of background radiation W 1, W 2, W 3 from KOP 45. Based on the results of this comparison, the spectral beam of the LR is corrected until equality of the ratios of the spectral components is achieved P 11 , P 21 , P 31 at the output of the optical combiner 7 to the ratios of the spectral components W 1 , W 2 , W 3 in the measured spectral distribution of background radiation from the COP 45.

The correction is carried out using controlled optical filters 4, 5, 6, which receive control signals from the output of the second information processing unit 25, separately for each wavelength 1 2 3. The transmission of controlled filters 4, 5, 6 is adjusted separately for each wavelength until the following equality is precisely achieved:

As a result of the correction of the spectral distribution of the generated total beam, a beam of laser radiation is formed at the output of the optical combiner 7 at three fixed wavelengths 1 2 3, forming a color gamut white light, the spectral distribution of which at the main wavelengths 1 2 3 exactly corresponds to the spectral distribution (composition) of these wavelengths in the background radiation from the COP. The laser beam intensities P 1 , P 2 , P 3 formed as a result of this correction at the corresponding wavelengths 1 2 3 , measured by photodetector blocks 21-23, as well as the value P in the spectral range measured by block 24, are stored in the second information processing block 25 .

As a result, in the information processing unit 25 the following values ​​of energy (or power) of pulses of LI beams P ni generated by laser generators and reduced to the output of scanning unit 8 are stored:

, i=1, 2, 3; 1 =( 1 ; 2 ; 3 ;),

where i is the corresponding correction factor for each wavelength i, connecting the amount of energy (power) of LR E i at the corresponding wavelength i, measured in FP blocks 21÷24, with the amount of LR energy at the output of scanning unit 8, i.e. with the amount of LR energy (power) emitted in the direction of KOP 45. These measured values ​​will be further used to determine the parameters of the spectral portrait of the retroreflection indicators of the detected object - OEP position 46 in KOP 45. Correction coefficients i are fixed technical parameters of the device and are determined by the corresponding coefficients transmission j of optical mirrors, scanning unit 8 and spectrum analyzer 20, fiber light guides 47÷50 at the corresponding wavelengths:

,

where j is the transmission of the corresponding optical element of the corresponding position in figure 1 at wavelength i. For example, 8 is the transmission of the scanning unit 8. The transmission of the mirrors 28, 29 is chosen to be small enough to attenuate the radiation from the output of the optical adder 7 to the sensitivity level of the photodetector units 21-24. Next, this formed total LR beam is supplied to the scanning unit 8, with the help of which the controlled volume of space is probed with scanned pulsed radiation at three wavelengths 1 2 3 simultaneously. At this stage, the folding mirror 30 does not participate in the operation of the optical channel. Next, optical radiation reflected from the COP 45 is received using the first lens 9 and the received radiation is converted into electrical signals by means of photodetectors pos. 10-12 (Fig. 1), each of which operates at a corresponding wavelength 1 2 3 . Photodetector pos. 13 registers radiation in a wide spectral band = 3 - 1. In front of each of the photodetectors, pos. 10-12, spectral narrow-band filters (for example, interference) are installed for the corresponding wavelength 1 - 3, pos. 40-43. An optical filter 43 of neutral type with a wide bandwidth is installed in front of the photodetector 13. Next, the electrical signals from the outputs of photodetectors 10-13 enter the first information processing block 18, in which threshold processing of each of the electrical signals is carried out for the corresponding fixed wavelengths 1 ÷ 3 (photodetectors 10-12), as well as the signal from the output of the photodetector 13 for a wide spectral band = 3 - 1. Threshold processing consists of comparing the level (amplitude) i of the pulse signal from the corresponding photodetector 10-13 with the threshold level Pi set for a given wavelength i = 1, 2, 3, or with the threshold level P set for a wide spectral reception band. The decision to detect an object in the form of a glare optical or optical-electronic device is first made provided that the established threshold level is exceeded for at least one of the wavelengths 1, 2 or 3 at the output of one of the photodetectors pos. 10-12, or when the established threshold level is exceeded P signal from the output of photodetector 13, operating in a wide spectral reception band:

The establishment of threshold levels i in each of the spectral receiving channels at wavelengths 1, 2, 3 is carried out before receiving radiation reflected from the COP 45, and also setting the threshold level P in the total spectral channel with a wide spectral band of receiving radiation = 3 - 1, registered photodetector 13.

Threshold levels are set in accordance with the sensitivity of the used photodetectors pos. 10-13, operating at the indicated discrete wavelengths 1, 2, 3, and in a wide range - photodetector 13. Threshold levels are set programmatically in the first information processing block 18 in accordance with the following conditions :

where K 1 is the required signal-to-noise ratio, which to ensure, for example, the probability of correct detection p=0.99 is chosen equal to K 1 =3; - sensitivity of the photodetector at wavelength i i=1, 2, 3, or photodetector 13 operating in a wide spectral range.

This sensitivity is presented here in the form of the power level (or energy) of pulsed light radiation at the input of the photodetector 11-13 at the corresponding wavelength i or in the wavelength range at which an electrical signal is formed at the output of the photodetector, equal in amplitude to the intrinsic noise level w of this photodetector , i.e. the signal-to-noise ratio equal to unity is realized.

After preliminary detection of an object in any of the spectral channels i, or in the broadband reception channel (FP 13), the distance L to the detected object is measured in accordance with the standard procedure for determining the range by the delay time of 1 reception pulse relative to the moment of emission of the laser pulse of the COP probing 45:

where C is the speed of light.

Next, in each of the spectral receiving channels 1, 2, 3 (FP 10-13), the level of the received optical signal E i is measured relative to the sensitivity level corresponding to the FP pos. 1-13, expressed in energy units.

To do this, in the first information processing block 18, when registering electrical signals from the outputs of the FP 10-13, the level (amplitude) of the electrical signal E Ei from the output of each FP 10-13 is determined by digitization and the ratio K PNi - signal/noise is determined for each spectral receiving channel , equal to the ratio , where E defi is the level of the intrinsic noise signal of a given FP 10-13, stored in block 18, corresponding to the energy (power) level of the input optical signal for this FP, equal to , i.e. the level of energy sensitivity of a given FP. Next, the level of the received optical signal at the input of the PD E i and E is determined by the formula:

where in the last formula the level of the input signal in the broadband reception channel (FP 13) is determined.

retroreflectivity indicators (RES) Pi for a given detected object, the signal from which exceeded the set threshold level in one or more reception channels (1 ÷ 3,).

Measurement of retroreflection indicators i=1, 2, 3, P i is carried out in the first information processing block 18 based on the specified measured values ​​of the levels of the received signal in each of the four receiving channels (FP 10-13), based on measurements, as well as using values ​​of the levels of laser pulse signals generated by laser generators 1-3 and measured by photoreceiving units pos. 21-24 (P 1, P 2, P 3). Between the first and second information processing blocks there is a constant exchange of information along the communication line connecting them.

The measured values ​​of the retroreflectivity indicators (RES) at three wavelengths, as well as the RSV for a wide spectral band P, form a certain spectral portrait (P i ; P ) of the RSV of the reflected signal from the COP for a given fixed position of the sighting axis of the scanning unit 8 and a fixed point in time, at which received reflected pulses of optical radiation, the electrical signals from which at the outputs of the FP 10-13 exceeded the established threshold levels in the first information processing block 18.

This obtained spectral portrait of the retroreflectivity indicators (RES) P i , P is used further for more accurate detection and final determination of the presence in the COP 45 of an optical or optoelectronic type device (for a given position in space of the sighting axis of the scanning unit 8). In this case, the resulting spectral portrait of the PSV allows one to determine whether the detected optoelectronic device belongs to a certain class of optical devices, for example, to determine the presence of an optoelectronic observation device with a television camera, an optical sight, or the presence of an observer with binoculars or a stereo scope.

The indicated OE devices and observation devices have significantly different spectral portraits of PSV in the visible or near-IR range. To recognize a detected object in the COP 45 based on the measured spectral portrait of the PSV (P i ; P ), information about the value of the PSV from the output of the first information processing unit 18 is sent to the input of the recognition block 44, where the received and measured spectral portrait of the PSV (P i ; is compared). P) with a data bank of spectral portraits of PSV various types optical and optical-electronic devices. Based on the comparison results, it is determined whether the detected optical or OE device belongs to the corresponding class of optical devices of a known type.

Information about the comparison results is transmitted to the consumer and displayed on the display of block 44. At this point, the cycle of probing the COP 45 and the detection and identification of optical and OE devices located in the COP is completed.

The determination of the spectral portrait of the retroreflection indicators is carried out in the first information processing block 18 as follows.

The determination of PSV P i is carried out on the basis of the well-known laser ranging formula, which determines the relationship between the energy (power) of pulsed laser radiation generated by a laser generator at the corresponding wavelength i and emitted in the direction of the COP 45, with the energy value E i of the received pulse radiation from the COP at the corresponding wavelength i and a number of parameters characterizing the propagation medium, the reflecting object in the COP, as well as a number of geometric and optical parameters of the receiving channels of the device implementing the method:

where ni is the divergence of the laser at wavelength i coincides with the divergence of the laser at the output of the corresponding laser generator (1, 2, 3), which is known from the passport data for the laser generators used, positions 1, 2, 3, or can be obtained from measurements;

L is the range to the reflecting object in KOP 45;

S about - the area of ​​the object that effectively reflects the LR at wavelength i with the divergence of the inverse radiation pattern about and the reflection coefficient at wavelength i negative;

D pr - diameter of the receiving lens pos. 9 of Fig. 1 in the receiving device that implements the method;

P is the total transmittance of laser radiation at wavelength i, including the following components:

P = OMT · atm, where

OMT is the transmission of the optical-mechanical path of a device that implements the method in Fig. 1 in the transmitting and receiving parts of the device (provided that the measurements of the energy of the laser pulses emitted and received from the object do not take into account the transmission of the optical-mechanical path. Otherwise, OMT = 1).

Atm is the transmittance of the atmospheric path in the forward and backward propagation of probing laser radiation at a distance to the object L.

This atmospheric transmittance at double distance to object 2L is determined in accordance with the following evaluation formula:

Where is the atmospheric weakening indicator?

L MDB - meteorological visibility range, determined from known meteorological tables.

Thus, in the presented laser ranging formula (8), along with the parameters reflecting the characteristics of the object, all other parameters are known or determined and measured as a result of the operation of the device implementing the method: L - measured range to the object; , E i - measured powers (energies) (3) in the emitted and received laser pulse at wavelengths i, i=1, 2, 3,

The value L MDB is entered a priori by the operator based on known tables and based on a visual assessment of atmospheric conditions and time of day during the period of operation of the device implementing the method. Photodetectors pos. 10-13 in Fig. 1 record the energy (level) of received pulsed LR signals reflected from the COP at the corresponding LR wavelengths, as well as in a wide band of wavelengths, and convert the level of these signals into electrical form. In electrical form, information about the levels of received LI signals comes from the outputs of photodetectors 10-13 to the inputs of the first information processing unit 18.

In formula (8) the quantity

by definition, is an indicator of the retroreflection of an object observed and illuminated by laser radiation at wavelength i. All components included in this value (10) are determined by the object’s own reflective characteristics. Hence, based on formula (8), the measured parameters L, E i, . and known parameters ni , D pr, OMT and parameter atm, determined by formula (9), determine the spectral indicator of retroreflection PSV for each of the used wavelengths i i = 1, 2, 3, in accordance with the following relation for P i obtained from formulas (8-10):

where atm from formula (9).

For a wide spectral range of wavelengths = 3 - 1, the value of the retroreflectivity index PSV=P is determined based on the following formula (11-2), in which instead of E i we substitute the value E of the energy (power) of the LR pulse recorded by the broadband photodetector pos. 13 in the range ; as a quantity of energy (power) ; as quantities; OMT and atm substitute their wavelength-averaged sr values; OMT Wed; atm avg.

The set of measured values ​​of the spectral indicators of retroreflection for three wavelengths and the total band form a spectral portrait of the retroreflectivity indicator (P )P i for one act of illuminating an element (observed point) of KOP 45 with three-wave probing radiation.

Thus, in the first information processing block 18, for each LR pulse emitted and received from the COP 45 at three wavelengths, the value of the retroreflection indicators of the PSV at the corresponding wavelengths i is determined from the set of wavelengths (i) of laser radiation with which the COP is probed, and for a wide band.

Based on the obtained values ​​of the set of values ​​of the retroreflectivity index, a spectral portrait of the PSV is formed for one act of probing the COP with laser radiation at three wavelengths for one specific fixed direction in space of the sighting axis of the scanning unit 8. The resulting value of the spectral portrait of the PSV is entered into the memory of the first information processing unit 18. Next, the scanning unit 8 switches (directs) its sighting axis to another (neighboring) point in space (KOP 45), which is illuminated with three-wave laser radiation, receives the radiation reflected from the KOP, measures the levels of the reflected and received signals at wavelengths 1 ÷ 3 and determines the spectral portrait of the PSV according to formulas (11), (11-2), the values ​​of which are entered into the memory of the first information processing block 18. Thus, as a result of probing the COP LI at three wavelengths for each direction in space from the location of the device implementing the method, towards the CPC and for each point of the (local) observation zone of the CPC, the value of the spectral portrait of the PSV is measured and formed (if at this point the received signal at at least one wavelength i exceeds the detection threshold set in block 18). The operation of comparing the measured spectral portraits of the PSV with the database in the recognition block 44 allows for a more accurate detection of optical and OE type devices that have specific values ​​of the spectral portrait of the PSV, as well as to recognize the detected optical-electronic device - to determine its belonging to a specific class of optical devices, the reference values ​​of the spectral portraits of PSV which are stored in the database - in the memory block of the recognition unit 44.

Comparison of the measured spectral portrait of the PSV is carried out as follows.

An element-by-element comparison of the values ​​of the retroreflectivity index in the measured spectral portrait of the PSV and in the reference spectral portrait of the PSV is carried out separately for each of the three wavelengths i i=1÷3 and range , and a difference spectral portrait is formed

where is the value of the retroreflectivity index of a certain reference spectral portrait of a reference optical-electronic device for a fixed wavelength i, is the reference value of PSV for the range.

Next, based on the measured difference spectral portrait R (12), the correspondence parameter F between the measured spectral portrait and the reference spectral portrait is determined using the formula:

Next, the specified comparison of the measured spectral portrait of the PSV is carried out for all reference spectral portraits of the PE stored in the database - the memory block of the recognition unit 44, and the values ​​of the difference portraits R i (12) and the matching parameters F j (13) are formed for each of the standards in block 44 database (j=1÷N).

In this case, an array of compliance values ​​is formed (F j ; j=1÷N) (14).

Next, from the generated array of compliance values ​​(14), from one to three values ​​F j are selected, having the minimum value from all other F j values ​​of the measured array F j (14). In this case, the specified three minimum values ​​of compliance are determined: F j =min(F j j=1÷N) (15) j=ja 1 ; ja 2 ; ja 3, which are used to judge whether the detected optical-electronic device belongs to the corresponding class of optical-electronic devices.

In the proposed method for detecting optical and optoelectronic means, probing of the KOP 45 is carried out simultaneously at three wavelengths 1 ÷ 3. In this case, LR at three wavelengths is formed in the visible wavelength range, and the wavelengths are selected corresponding to the main components of the color gamut of the visible range, ensuring that the observer perceives the total long-wave radiation (1, 2, 3) as white radiation. In this case, the wavelengths of three laser generators (items 1÷3) and their initial intensities are equal to the following values:

The laser generator (LG) position 1 of Fig. 1 generates red radiation (R) with a wavelength 1 =0.7 μm with a luminous flux intensity in one pulse LI P 1, for example, equal to one lumen (lm).

Laser generator pos. 2 generates green radiation (G), with wavelength 2 = 0.5 μm and luminous flux intensity P 3 = 4.59 in conventional units, for example lumens, relative to the LG laser pos. 1, generating red radiation 1 colors.

LG position 3 generates blue radiation (B) with wavelength 3 =0.43 microns and luminous flux intensity in the indicated units relative to the radiation of LG position 1, equal to P 3 =0.06. This specified relationship between the light fluxes P i i=1, 2, 3 generated by LGs 1÷3 is initial and is established by selecting the appropriate pumping levels of the used LGs. In this case, the indicated ratio between the intensities of the light fluxes of the LG P 1:P 2:P 3 =P R:P G:P B =1:4.59:0.06 ensures the perception of the total light flux (total laser pulse) as white radiation. It should be noted that the perception of the total emitter as white will occur when observing this radiation both by an observer with passive observation, for example, using binoculars, and when receiving (observing) the total radiation using optoelectronic means with a broadband spectral photodetector in the visible range. The indicated ratio of LG radiation intensities and wavelengths was chosen in accordance with the well-known colorimetric theory of mixing spectral colors.

According to the proposed method, when generating laser radiation at three wavelengths by three different laser beams 1÷3, the ratio between the intensities of the generated laser beams P 1 , P 2 , P 3 is established, corresponding to the measured ratio between the intensities W 1:W 2:W 3 of the spectral components on the specified selected three wavelengths 1, 2, 3 in the measured spectral distribution of background radiation from the controlled volume of space. In this case, the pumping level of LG 1÷3 has already been pre-selected in accordance with the standard ratio of the intensities of color radiation in a three-color colorimetric system color scheme.

Therefore, when performing this operation, only a slight adjustment of the pumping level of LG 1-3 is carried out until a ratio between the intensities of the generated laser beams is obtained in the first approximation corresponding to the measured ratio between the intensities W 1:W 2:W 3 of the spectral components in the measured background radiation from the COP 45. Subsequent correction of the spectral distribution of the total light flux using controllable light filters 5, 6, 4 makes it possible to ensure exact correspondence of the spectral distribution of the generated total three-wavelength radiation to the spectral distribution of the natural measured background radiation at the specified main (color) wavelengths. The use of three-wavelength radiation with a spectral distribution corresponding to the spectral distribution of natural background radiation from the COP for probing a controlled volume of space 45 provides the following advantages of the proposed method.

Background radiation from the COP, when received by photodetectors 10, 11, 12, operating in spectral regions with average wavelengths 1, 2, 3, does not introduce distortions into the ratio of the intensities (levels) of received optical signals in the corresponding spectral reception channels, since in these channels reception level of background radiation is proportional to the level of radiation from the backlight of the COP at the corresponding wavelengths and, accordingly, to the level of the received optical signal reflected from the COP. In this case, when recording radiation reflected from the COP, the ratio between the levels of received optical signals (radiations) at different wavelengths 1, 2, 3 does not change depending on the levels of background radiation at these wavelengths 1, 2, 3, but is determined only by the parameters (characteristics ) spectral portrait of retroreflection indicators at 1, 2, 3 from the detected object, which allows for more accurate recognition and detection of optical-electronic devices (OED) at different levels of background radiation at different times of the day.

It should be noted that the level of background irradiance and its spectral composition - the ratio between the main (basic) spectral components - vary significantly depending on the height of the Sun above the horizon, time of day, etc. (see, for example, p. 283, table 15 - color temperature of natural light depending on the height of the Sun above the horizon). Therefore, the proposed method for detecting OEP using OPC probing with a three-wavelength LR with a spectral distribution corresponding to the spectral distribution of background natural radiation allows for high precise measurement(determination) of the spectral portrait of the retroreflectivity index at any time of the day, regardless of the nature and spectral distribution of natural external background radiation. The reduction in the influence of the distribution of background radiation when recording the received optical signal reflected from the COP at three wavelengths can be demonstrated as follows.

The recorded optical signal in electrical form at the outputs of photodetectors 10, 11, 12 J i i=1, 2, 3 can be represented in the following form:

,

where P u1, P u2, P u3 are the intensities of laser radiation for illuminating the COP, generated by laser generators and emitted at the corresponding three wavelengths, 1, 2, 3, are conversion coefficients relating the level (amplitude) of emitted laser pulses with the magnitude of the received signal in accordance with relation (8), and also taking into account the sensitivity and transfer characteristics of photodetectors; e 1 , e 2 , e 3 - the level of natural background radiation at the corresponding wavelength of the LR (i=1, 2, 3), presented in the form of an electrical (noise) signal at the output of the corresponding photodetector pos. 10-13 in Fig.1.

The value i i=1÷3 contains the value of the measured PSV (11), as well as a number of known parameters determined by the design of the device implementing the method, for example, the diameter of the lens 9.

In accordance with the measured level of the spectral distribution of background radiation and the intensities P u1, P u2, P u3, the values ​​of J 1,2,3 (16) can be represented in the following form:

,

where n 2 , n 3 are known and measured in block 25 values ​​of the relationships between the spectral components in the background radiation: W 1:W 2:W 3 =e 1:n 2 e 1:n 3 e 1, obtained by accepting the value e 1 per unit of reference (baseline background level) when determining the relationships between the spectral components of background radiation: . W 1:W 2 =1:n 2

Accordingly, we have similar relationships for the intensity of LG radiation P ui i=1, 2, 3, established in the same proportions as W 1:W 2:W 3. From relations (17) it is clear that with an increase in the background component, for example, at the second wavelength by n 2 times relative to the background component at the first wavelength, the intensity level of the illuminating COP LR at this second wavelength also increases by n 2 times and the effect of changing the level the background to the ratio of the measured received signals at the first and second wavelengths is reduced or eliminated, thus, automatic compensation for changes in the background level is realized by a corresponding increase in the intensity level of the illuminating COP 45 LI at this wavelength. The signal-to-noise ratio (background) in (17) is the same for all three wavelengths (with equal values ​​of 1 = 2 = 3), therefore, background radiation will introduce the same errors in the measurement of the levels of incoming signals and in the measured PSV at all three wavelengths , and will not introduce additional errors in the ratio of the measured PSV values ​​at three wavelengths, which is important for obtaining reliable information about the PSV spectral portrait.

With the same parameters of the reflective characteristics of the object at three wavelengths 1 = 2 = 3 (test object), we have the ratio J 1:J 2 equal , independent of the level of background radiation e 1 , e 2 , e 3 , changing during the day. Likewise . Let us recall here n 2 and n 3 are the measured relative values ​​of the background components at the second and third wavelengths relative to the background component at the first wavelength, taken as unity (as the base level of the background value), e 1 , e 2 , e 3 - background levels at the corresponding wavelengths 1, 2, 3, presented in electrical signals recorded at the outputs of the corresponding photodetectors pos. 10-13.

Thus, the measurement of the relationships between the quantities 1, 2, 3 when receiving and recording the optical signal reflected from the COP is ensured in the proposed method with a decrease in the influence of the natural spectral distribution of background radiation from the CPC in effect at the time of PSV measurements. It should be noted that the measurement of the spectral distribution of background radiation from the COP using an optical spectrum analyzer 20 and photodetecting units 21-24 is carried out in the region of selected wavelengths 1, 2, 3, in some spectral subranges 1, 2, 3, and wavelengths 1 ÷ 3 located in the middle of these ranges. In the first information processing block 18, after recording electrical signals J i (17) from the outputs of photodetectors 10÷12, compensation is carried out for additive background components e 1 , e 2 , e 3 in the recorded electrical signals J i . To do this, the level of the background component e 2 is determined (estimated), which is the most intense spectral component of natural background radiation at wavelength 2 (G - green). The level of this background component is assessed using an optical spectrum analyzer 20 and a corresponding photodetector unit 22 operating at wavelength 2 . In this case, as noted earlier, the photodetector unit 22 evaluates the level W 2 of natural background radiation at wavelength 2 in a certain range. Information about this value W 2 of the level of background illumination at wavelength 2 , representing a certain average value of the background at 2 over a certain averaging time, enters the first information processing block 18, where, based on the value of W 2, an average estimate of the value of the background component e 2 is formed (at 2), which in block 18 is calculated based on the available information about the spectral sensitivity band of the photodetector 11 by 2 or the bandwidth of the interference spectral filter 44. The actual sensitivity of the photodetector 11, as well as information about the diameter of the receiving first lens 9 and the transmittance of the optical path at wavelength 2 are available in block 18. Next, the actual compensation of the background component in the recorded signal J 2 is carried out by subtracting in the first information processing block 18 from the value J 2 the obtained estimate of the background component, the background components are carried out on the basis of the obtained estimate of the average value of the background component for wavelength 2 based on the following ratios:

where n 2 and n 3 - in accordance with (17), as indicated, are known and previously measured in block 25 values ​​of the relationships between the spectral components in the measured natural background radiation. In a similar way, background compensation is carried out in the signal recorded at the output of the photodetector 13, operating in a wide spectral band.

Compensation of background radiation in the recorded signals J i makes it possible to increase the accuracy of determining the distribution of the spectral portrait of the PSV and to carry out a more accurate determination of whether the detected OE device belongs to a specific class of similar devices.

An important advantage achieved as a result of the implementation of the proposed method is ensuring the secrecy of the operation of the proposed OES detection device. This is ensured by the fact that, as stated above, the perception of radiation probing the COP by an external third-party observer is realized as a short flash of white color, coinciding in spectral sensation with background natural radiation in a controlled volume of space, operating at the corresponding moment in time of observation and operation of the detection device at a specific time of day and height above the horizon of natural sources of radiation - the Sun or the Moon. Therefore, the radiation of the proposed device will be perceived by an external observer as a random glare from a passive reflector - glass or a metal object reflecting natural background radiation, and the operation of the device as an active detection probing laser complex will not be detected. Similarly, reconnaissance OES with broadband optical photodetectors will perceive the radiation of the proposed device as a reflection of a natural light source from a passive reflector, and not as the work of a laser probing complex. Consequently, when operating the proposed method and the device that implements it, the secrecy of the device’s operation is ensured at any time of the day and at the height of the natural light source above the horizon.

The database of the recognition unit 44 stores reference spectral portraits of the PSV of various OE devices and the observer's OES, obtained experimentally (or calculated) for various basic (main) spectral wavelengths 1 - 3 of the visible range and a wide band of wavelengths, obtained for various heights above horizon of natural light sources for different times of day or different seasons of the year (summer, winter, etc.). In this case, as noted, recognition of the type of OE device is carried out both on the basis of the formation of a difference portrait of spectral PSV, and on the basis of comparison of the relationships between individual spectral components of the PSV in the measured spectral portrait of the PSV from the detected object of the OE device and in the reference PSV from the database block 44 data.

3 - for one measurement - one reading of the received level of the reflected optical signal from the COP, recorded by photodetector 13. This measured PSV from the signal from photodetector 13 (integrated PSV) together with the spectral portrait of PSV at wavelengths 1, 2, 3 allows for more accurate identification detected object 46 KOP, as an OE device of the corresponding known type (class) of optical devices.

The proposed device for detecting OE devices is implemented on the basis of standard blocks and assemblies. The first and second information processing blocks 18, 25 are made on the basis of standard electronic computers (PCs) and are equipped with special software that ensures registration and processing of incoming electrical signals from the outputs of photodetectors and photoreceiving units, measurement of the levels of corresponding electrical signals, generation of threshold levels and performing other operations on incoming signals in accordance with the above method operations. In addition, the second information processing unit 25 controls the operation of laser generators and controlled filters, as well as controls the installation of the first and second folding mirrors in the optical path. The first information processing unit 18 also controls the operation of the scanning unit 8 and generates the electrical control signals necessary to control the scanning unit.

The recognition unit pos. 44 is a specialized electronic computer (PC) and carries out determination (calculation) according to the given formulas of the retroreflective indicators (RES) of the observed and detected objects in the OPC for three wavelengths, determination (calculation) of the RSV (in the band ) and formation of a portrait of the PSV, as well as recognition of a detected object by comparing its measured PSV values ​​and the values ​​of the reference PSV stored in special memory registers of the recognition unit 44.

The optical spectrum analyzer 20 can be made on the basis of any known optical spectral device (spectrograph), for example, on the basis of a high-resolution diffraction grating. Photodetecting units pos. 21-24 register the intensities of the spectral distribution of natural background radiation from the COP, received by lens 19, at fixed wavelengths 1, 2, 3, as well as in a wide spectral range. The outputs of the optical spectrum analyzer 20 are optically connected to photoreceiving units 21-24 using fiber-optic light guides 47-50. The first and second folding mirrors 30, 33 are mechanically connected to control units 32, 31, which are, for example, stepper motors controlled by software from an information processing unit. The scanning unit 8 is made on the basis of a controlled acousto-optical cell, or on the basis of a reflective mirror, rotated using a stepper motor controlled by signals from the first information processing unit 18.

Thus, illuminating the COP 45 with laser radiation simultaneously at several wavelengths makes it possible to realize the following advantages: 1. Provides measurement of the PSV of an object observed in the COP at several wavelengths. 2. Provides a spectral portrait of the PSV of an object, which increases the probability of detecting and recognizing an object in the COP, increases the reliability of classifying the detected object as a known class of OE devices, reduces the influence of background radiation on the values ​​of the measured PSV and more accurately measures the PSV, which increases the probability of detection and recognition of OESN. Measuring PSV in a wide range of wavelengths makes it possible to obtain additional information about the reflective characteristics of the observed object, obtained directly by one photodetector, which complements the information obtained by individual narrow-spectrum photodetectors and together provides an increase in the probability of recognition of OE devices in real conditions.

Information sources

RF Patent No. 2133485 dated 07.1998 “Method for detecting optical and optoelectronic devices.”

RF Patent No. 2223516 dated 07.2002 “Method for detecting the eyes of people and animals.”

RF Patent No. 2278399 dated June 16, 2004 “Method for detecting optical and optoelectronic surveillance equipment and a device for its implementation” (prototype).

Handbook of laser technology, ed. A.P. Napartovicha, M.: Gosenergoizdat, 1991.

Signals and interference in laser ranging. V.M. Orlov et al., ed. V.E. Zueva, M.: Radio and communications, 1985.

V.V. Sharonov “Light and Color”, M.: Gosfizmatlit, 1961.

M. Born, E. Wolf “Fundamentals of Optics”, M.: Nauka, 1973

RF Patent No. 2380834 dated June 23, 2008

CLAIM

1. A method for detecting optical and optoelectronic surveillance equipment (OESN), including probing a controlled volume of space (VSV) with scanned pulsed laser radiation (LI) at wavelength 1, receiving reflected LR signals and signals of natural background radiation from the VSV, converting the received LR into the electrical signal, its threshold processing, OESN detection and range determination,

characterized in that the reception of natural background radiation signals from the COP is carried out before probing the COP, in the received natural background radiation from the COP the spectral distribution of radiation is measured, in the measured spectral distribution the ratio between the intensities of W 1, W 2, W 3 spectral components is determined at wavelength 1 and at two additional wavelengths 2, 3, corresponding to the intensities W 1, W 2, W 3, pulsed LR beams are generated at wavelengths 1, 1, 1, i. 1, registered by a broadband photodetector of the device implementing the method; 1, 2, 3 values ​​of LR divergence, transmission of the optical-mechanical path and transmission of the atmosphere.

4. A device for detecting optical and optoelectronic surveillance equipment, containing a scanning unit placed sequentially on the optical axis, a first laser generator operating at the first wavelength 1, a first lens, the optical input of which is connected via an optical mirror to the optical input of the scanning unit, a first photodetector , the optical input of which is connected through the first optical filter, the first lens and the second optical mirror to the optical output of the first lens, the first information processing unit, the input of which is connected to the output of the first photodetector, the second lens, the optical axis of which is parallel to the optical axis of the scanning unit, the electrical input of which connected to the first information processing unit, characterized in that the second and third laser generators, three controlled optical filters, an optical combiner, an optical spectrum analyzer, four photodetector units, a second information processing unit, a recognition unit, first and second folding mirrors, three photodetectors, three optical filters, four translucent mirrors and four optical mirrors, as well as four fiber-optic light guides, wherein the optical input of the optical spectrum analyzer is connected to the optical output of the second lens, the optical output of the optical spectrum analyzer is connected through fiber-optic light guides to the inputs of four photoreceiving units, outputs which are connected to the second information processing unit, the optical input of the optical adder through three controllable optical filters, the translucent and optical mirrors are connected to the corresponding optical outputs of the first, second and third laser generators, the optical output of the optical adder is connected to the optical input of the scanning unit, and through the first folding mirror, two optical mirrors and a second folding mirror are optically connected to the optical input of the optical spectrum analyzer, the optical output of the first lens is optically connected to the newly introduced second, third and fourth photodetectors through three translucent mirrors, three lenses and three optical filters, the outputs of the second, third and fourth photodetectors are connected to the inputs of the first information processing unit, the outputs of which are connected to the recognition unit and the second information processing unit, the outputs of which are connected to the control inputs of the first, second and third laser generators, the first, second and third controlled filters and the first and second folding mirrors.

5. The device according to claim 4, characterized in that the optical spectrum analyzer is made on the basis of an optical diffraction grating.

6. The device according to claim 4, characterized in that the recognition unit is made on the basis of a digital electronic computer containing a data block of the values ​​of reference portraits of spectral retroreflectivity indicators (SRV).

Photogrammetry– (photos-light, gramma-recording, metreo-measurements) scientific discipline related to the determination of geometric parameters (shapes, dimensions of spatial position and other properties of objects from their image)

Remote sensing– obtaining information about an object from measurements taken at a distance from the object, i.e. without direct contact with it.

Benefits of remote sensing data:

Digital type of information

Objectivity and reliability

Visibility

Efficiency

Regularity and frequency of information receipt

Variety of resolutions and types of shooting

Possibility of studying slow and transient processes

Disadvantages of remote sensing data:

Presence of geometric, radiometric and other distortions

Information oversaturation

Presence of white spots

Remote sensing methods:

Passive

The imaging system records either the solar energy reflected by the object or the object’s own radiation

Active

The imaging system emits a signal from its own energy source, and then records the part of it reflected by the object.

Filming systems

Classification of filming systems:

Depending on the receiver there are:

Photographic image

The image is formed optically on photographic film, and the visible image is obtained after photochemical processing (developing and printing)

Digital image

The radiation receiver is a matrix or line of CCDs (charge-coupled devices)

By image acquisition method:

Passive

1. Photographic

   Optical-mechanical scanning systems

   Optical-electronic scanning systems

Active

1. Radar survey systems

   Laser scanner imaging systems

Photographic shooting systems

In photographic SS, the image is formed almost instantly, according to the laws of central projection.

Classification of cameras:

Single-objective

Multi-objective

Panoramic

By viewing angle:

Narrow angle (τ< 50°)

Normal (50°< τ < 90°)

Wide angle (90°< τ < 110°)

Ultra wide angle (τ > 110°)

By focal length:

Short focal length (f< 100 мм)

Normal (100 mm< f < 300мм)

Long focal length (f > 300 mm)

Optical-mechanical scanning systems

Optical-mechanical scanner– contains only 1 technical element (sensor), which allows you to measure the brightness of a small area (pixel) of the earth’s surface

A rotating mirror scans a strip of terrain, which makes it possible to record the brightness of a whole number of pixels on the earth's surface in a short period of time, i.e. to form an image line.

The next line of the image is formed by the movement of the media.

If a single sensor is replaced with a ruler, a multi-channel image can be obtained.

The thermal component of radiation can be obtained using a semi-transparent mirror.

Optical-electronic scanning systems

The image constructed using optical-electronic scanners is projected onto a linear or matrix array of CCDs.

Radio locating scanner systems

The mutual impulse from the transmitter installed on the carrier is emitted by a directional antenna, forming a fan-shaped beam in the vertical plane.

Part of the reflected energy is recorded by a receiver installed in the same place as the transmitter. As a result, signals are generated that control the brightness of the light spot of the cathode ray tube. The combination of such spots forms a line of the radar image, and the time it takes for the signal to travel determines the distance to the object.

Wavelength ranges:

X stripe (𝜆=2.4 – 3.8 cm)

C strip (𝜆=3.8 – 7.5 cm)

L strip (𝜆=15 – 30 cm)

Laser filming systems

Laser– light amplification by means of stimulated emission, i.e. this is a device that converts pump energy into the energy of a monochromatic and narrowly directed radiation flux.

Single shots

E– object plane (terrain plane)- A horizontal plane passing through any point in the terrain

S– photographing point (projection center)

n– Plane of best image

So′ - main beam

f – focal length– distance from S to o′

p– image plane

o- the main melancholy of the photo

a, b– small image of points A and B

O– Point on the ground corresponding to the main point

Bunch of rays– the set of all projecting rays

Main beam- Beam coinciding with the optical axis of the camera

N f – photographing height– distance from the photographing point S to the object plane E.

–basic formula for determining scale

n– nadir point– the point of intersection of a plumb line drawn through the photographing point and a plumb line

N– a point on the terrain corresponding to the nadir point

α° - total angle of inclination of the image

With -zero distortion point– the point of intersection of the bisector of the angle of inclination of the image and the plane of the image

WITH– point on the ground corresponding to the point of zero distortion

Tt– base line– line of intersection of plane E and plane p

Q – main vertical plane– vertical plane passing through the main beam

Vv – main vertical– line of intersection of the plane of the main vertical and the plane of the image

V.V. – shooting direction line– line of intersection of the object plane and the plane of the main vertical (Q and E)

E′ -actual horizon plane- horizontal plane drawn through the photographing point

ii – actual horizon line– line of intersection of the real horizon plane and the p plane.

I – main vanishing point– point of intersection of the actual horizon and the main vertical VV

qq – main horizontal line– a straight line in the image plane drawn through the main point perpendicular to the main vertical

h c h c – zero distortion line– a straight line in the image plane passing through the point of zero distortion parallel to the main horizontal line qq.

SCANNERS AND SCAN

The source material for creating graphic compositions can be found in existing graphic files. However, please remember that some of them are subject to copyright protection and therefore cannot be freely copied. You can also create your own works “from scratch” using the drawing tools of graphic editors. But then you need both artistic abilities and computer drawing skills. There is another effective way to create computer graphics. It is based on the use of scanners or digital cameras. Good cameras are quite expensive, but scanners are successfully conquering the consumer goods market and are quite affordable. Using a scanner, you can enter into your computer pictures from newspapers, magazines, books and photographs, either entirely or in parts, which will serve as building material for future compositions. You can create sketches and blanks first on paper, and then enter them into the computer using a scanner and modify them using graphic editors. Finally, a scanner is simply irreplaceable when you need to turn a printed paper document into a text document so that you can open it in a text (rather than a graphics) editor (for example, MS Word) for viewing and editing.
A scanner is a device for entering images into a computer. Source images (originals) are usually located on opaque (paper) or transparent (slides, film) media. Usually these are drawings, photographs, slides and/or texts, but there can also be three-dimensional objects. Essentially, a scanner is a device that takes optical information available to our vision and first converts it into electrical form and then converts it into a digital form suitable for input into a computer. Thus, the process of scanning an original consists of digitizing it. The digitized image (in the jargon - “scan”) can later be processed on a computer using a graphics editor (for example, Photoshop) if it is a drawing, or using a character recognition program (for example, FineReader) if it is text.
There are many models of scanners, differing in both technical characteristics and capabilities, as well as in price. It’s not at all a fact that you need the most powerful and most expensive scanner. Beginners, as a rule, have difficulty choosing a scanner model and, subsequently, using it. A mistake in choosing a scanner results either in the fact that you underpaid a little, or you overpaid too much. When choosing a scanner, you should proceed from the tasks that you are going to solve with its help. Scanners can be used for routine office tasks, home photo collecting and professional graphics work. For Web design, for example, you can get by with the cheapest scanners. But for jobs that are ultimately intended for printing, you may need a more powerful device.
To navigate among the many parameters of scanners, you should understand what they practically affect and what they depend on. In this chapter we will try to help resolve these problems. First you need to get a general understanding of the principles of construction and operation of scanners. This is not at all difficult and does not require much time, but it is very important. Then you should understand the basic parameters (technical characteristics) and master several typical techniques for using scanners. Finally, you need to learn how to correct scanned images in graphics and other editors.

How scanners are designed and work

For office and home tasks, as well as for most computer graphics work, the so-called flatbed scanners. Various models of this type are more widely available on sale than others. Therefore, let's start by considering the principles of construction and operation of scanners of this particular type. Understanding these principles will provide a better understanding of the technical characteristics that go into choosing scanners.
A flatbed scanner is a rectangular plastic case with a lid. Under the cover there is a glass surface on which the original is placed to be scanned. Through this glass you can see some of the insides of the scanner. The scanner has a movable carriage on which a backlight lamp and a mirror system are installed. The carriage moves through the so-called stepper motor. The lamp light is reflected from the original and, through a system of mirrors and focusing lenses, enters the so-called matrix, consisting of sensors that produce electrical signals, the magnitude of which is determined by the intensity of the light incident on them. These sensors are based on light-sensitive elements called charge coupled devices(CCD, Couple Charged Device - CCD). More precisely, an electrical charge is generated on the surface of the CCD that is proportional to the intensity of the incident light. Next, you just need to convert the value of this charge to another electrical quantity- voltage. Several CCDs are located side by side on one line. The electrical signal at the output of the CCD is an analog quantity (i.e., its change is similar to the change in the input quantity - light intensity). Next, the analog signal is converted into digital form, followed by processing and transmission to a computer for further use. This function is performed by a special device called analog-to-digital converter(ADC, Analog-to-digital Converter - ADC). Thus, at each step of moving the carriage, the scanner reads one horizontal strip of the original, divided into discrete elements (pixels), the number of which is equal to the number of CCDs on the line. The entire scanned image consists of several such stripes.

Rice. 119. Diagram of the design and operation of a flatbed scanner based on a CCD (CCD): the lamp light is reflected from the original and, through an optical system, hits a matrix of photosensitive elements, and then to an analog-to-digital converter (ADC)

Color scanners now typically use a three-row CCD matrix and illuminate the original with calibrated white light. Each row of the matrix is ​​designed to perceive one of the basic color components of light (red, green and blue). To separate colors, they use either a prism, which splits a beam of white light into colored components, or a special CCD filter coating. However, there are color scanners with a single-row CCD matrix, in which the original is illuminated in turn by three lamps of basic colors. Single-row, triple-illuminated technology is considered obsolete.
Above we described the principles of construction and operation of so-called single-pass scanners, which scan the original in one carriage pass. However, three-pass scanners are still found, although no longer commercially produced. These are scanners with a single-row CCD matrix. In them, with each pass of the carriage along the original, one of the basic color filters is used: for each pass, information is removed from one of the three color channels of the image. This technology is also outdated.
In addition to CCD scanners based on a CCD matrix, there are CIS (Contact Image Sensor) scanners that use photocell technology. Photosensitive matrices made using this technology perceive the reflected original image directly through the scanner glass without the use of optical focusing systems. This made it possible to reduce size and weight flatbed scanners more than doubled (up to 3-4 kg). However, such scanners are only good for extremely flat originals that fit tightly to the glass surface of the working field. In this case, the quality of the resulting image significantly depends on the presence of extraneous light sources (the CIS scanner cover must be closed during scanning). In the case of volumetric originals, the quality leaves much to be desired, while CCO scanners give good results for volumetric (up to several cm in depth) objects.
Flatbed scanners can be equipped with additional devices, such as a slide adapter, automatic document feeder, etc. Some models are provided with these devices, but others are not.
Slide adapter (Transparency Media Adapter, TMA) is a special attachment that allows you to scan transparent originals. Transparent materials are scanned using transmitted rather than reflected light. In other words, the transparent original must be between the light source and the photosensitive elements. The slide adapter is a mounted module equipped with a lamp that moves synchronously with the scanner carriage. Sometimes they simply illuminate a certain area of ​​the working field evenly so as not to move the lamp. Thus, the main purpose of using a slide adapter is to change the position of the light source. "
If you have a digital camera ( digital camera), then the slide adapter, more likely, you don't need it.
If you scan transparent originals without using a slide adapter, you need to understand that when the original is irradiated, the amounts of reflected and transmitted light are not equal to each other. So, the original will miss some of the incident color, which will then be reflected from the white coating of the scanner lid and pass through the original again. Some of the light will be reflected from the original. The ratio between the parts of transmitted and reflected light depends on the degree of transparency of the original area. Thus, the light-sensitive elements of the scanner matrix will receive light that has passed through the original twice, as well as light reflected from the original. The repeated passage of light through the original weakens it, and the interaction of the reflected and transmitted beams of light (interference) causes distortion and side video effects.
An automatic feeder is a device that feeds originals into the scanner, which is very convenient to use when streaming images of the same type (when you do not need to frequently reconfigure the scanner), for example, texts or drawings of approximately the same quality.
In addition to flatbed ones, there are other types of scanners: manual, sheet-fed, drum, slide, for scanning barcodes, high-speed for streaming documents.
Handheld Scanner is a portable scanner in which scanning is carried out by manually moving it over the original. The principle of operation of such a scanner is similar to that of a tablet scanner. The width of the scanning area is no more than 15 cm. The first scanners for widespread use went on sale in the 80s of the 20th century. They were manual and allowed scanning of images in shades of gray. Nowadays such scanners are not easy to find.
Sheet or roller scanner(Sheetfed Scanner) - a scanner in which the original is pulled past a stationary linear CCD or CIS matrix; a type of such a scanner is a fax machine.
Drum scanner(Drum Scanner) - a scanner in which the original is fixed on a rotating drum, and photomultipliers are used for scanning. In this case, a dot area of ​​the image is scanned, and the scanning head moves along the drum very close to the original.
Slide scanner(Film-scanner) is a type of flatbed scanner designed for scanning transparent materials (slides, negative films, X-rays, etc.). Usually the size of such originals is fixed. Note that some flatbed scanners have a special attachment (slide adapter) designed for scanning transparent materials (see above).
Barcode Scanner(Bar-code Scanner) - a scanner designed for scanning product barcodes. According to the principle of operation, it is similar to a hand-held scanner and is connected to a computer or to a specialized trading system. If you have the appropriate software, any scanner can recognize barcodes.
High-speed scanner for working with documents(Document Scanner) is a type of sheet-fed scanner designed for high-performance multi-page input. Scanners can be equipped with input and output trays with a capacity of over 1000 sheets and input information at speeds in excess of 100 sheets per minute. Some models of this class provide two-sided (duplex) scanning, backlighting the original in different colors to cut out the colored background, compensation for background heterogeneity, and have modules for dynamic processing of different types of originals.
So, a flatbed scanner is best for home and office use. If you want to do graphic design, then it is better to choose a CCD scanner (based on a CCD matrix), since it allows you to scan three-dimensional objects. If you plan to scan slides and other transparent materials, you should choose a scanner that has a slide adapter. Usually the scanner itself and the slide adapter that goes with it are sold separately. If you cannot purchase a slide adapter at the same time as the scanner, you can do so later if necessary. It is also necessary to determine the maximum sizes of scanned images. Currently, the standard format is A4, corresponding to a regular sheet of writing paper. Most household scanners are designed specifically for this format. Scanning drawings and other design documents typically requires A3 size, which corresponds to two A4 sheets joined along the long side. Currently, the prices of scanners of the same type for A4 and A3 formats are getting closer. It can be assumed that originals that do not exceed the A4 format will be better processed by a scanner oriented to the A3 format.
The parameters listed above do not exhaust the entire list, but at this stage of our consideration we can only use them for now. When choosing a scanner, three aspects are decisive: a hardware interface(connection method), optical-electronic system And software interface c (the so-called TWAIN module). Next we will look at them in more detail.

Connecting the scanner to a computer

Scanning results data is transferred in digital form from the scanner to a computer for subsequent processing and/or storage as files. Scanners can connect to your computer in a variety of ways. In other words, they may have different hardware interface.
One of the most common is the SCSI interface. It is provided by a special board (adapter, card) inserted into the expansion connector (slot) on the computer motherboard. You can connect not only a scanner with a SCSI interface to this board, but also other devices (for example, hard drives). So, the SCSI interface is provided by a separate device that you may already have on your computer. Almost all flatbed scanners with a SCSI interface are equipped with a truncated modification of the SCSI board, to which only the scanner can be connected. Thus, if your computer does not have a SCSI adapter, but there is a free suitable slot on the motherboard, then there will be no fundamental problems connecting the scanner. The SCSI interface is reliable and provides fast data transfer. However, a board may need to be installed. To do this, remove the cover when the computer is turned off. system unit computer and install an interface board in one of the free and suitable slots. The details are quite clearly described in the scanner manual.
In addition, there are flatbed scanners that have their own interface board, which, in addition to data transmission, provides electrical power to the scanner from the computer system unit. In this case, power will be supplied to the scanner only when the scanning program is started. Please keep in mind that the scanner's interface card may fit into an ISA slot or a PCI slot on the computer's motherboard. Therefore, before choosing such a scanner, you should find out whether your computer has a free suitable slot.
If you often have to move the scanner, connecting it to one computer or another, then the methods described above may seem inconvenient: each time you need to turn off the computer, remove the cover, remove or install the interface board. On the other hand, all this trouble, with appropriate skill, requires only 5 - 10 minutes.
There are scanners that connect to a USB port (universal serial bus) of a computer. This is the most convenient and fastest interface that does not require installing the board into the system unit, and sometimes even turning off the computer. The USB port not only provides data exchange between the computer and an external device connected to it, but also powers the device from the system power supply. However, this is not true for all devices. Some of them are equipped with their own power supplies and then, as a rule, when connecting them with a cable to a computer, the latter has to be turned off. In any case, before connecting the scanner to the USB port, you should find out from the included manual how exactly this is done. In addition, you need to keep in mind that USB ports are not available on older computer models (the first Pentium and earlier).
Many flatbed scanner models connect to the parallel port (LPT) on your computer that you would normally connect to your printer. In this case, the scanner is connected via a cable directly to the LPT port, and the printer is connected to an additional connector on the scanner body. This interface is slower than the ones described above. To connect the scanner to the LPT port, you do not need to remove the cover of the system unit, but you still need to turn off the computer during this operation.
Generally speaking, scanners with any of the interfaces discussed above can be used to work with graphics. However, we give preference to SCSI and USB interfaces based on considerations of reliability, speed and ease of use.

Main characteristics of the optical-electronic scanner system

Let's consider the main characteristics of the scanner's optical-electronic system: resolution, color depth, bit depth, optical density and high-resolution area.

Permission

Resolution or scanner resolution- a parameter characterizing the maximum accuracy or degree of detail in the representation of the original in digital form. Resolution is measured in pixels per inch(pixels per inch, ppi). Resolution is often indicated in dots per inch (dpi), but this unit of measurement is traditional for output devices (printers). When talking about resolution, we will use ppi. There are hardware (optical) and interpolation resolutions of the scanner.

Hardware (optical) resolution

Hardware/optical Resolution is directly related to the density of photosensitive elements in the scanner matrix. This is the main parameter of the scanner (more precisely, its optical-electronic system). Usually the horizontal and vertical resolution is specified, for example, 300x600 ppi. You should focus on a smaller value, i.e., horizontal resolution. The vertical resolution, which is usually twice the horizontal resolution, is ultimately obtained by interpolation (processing the results of direct scanning) and is not directly related to the density of the sensitive elements (this is the so-called double step resolution). To increase the scanner resolution, you need to reduce the size of the photosensitive element. But as the size decreases, the element’s sensitivity to light is lost and, as a result, the signal-to-noise ratio deteriorates. Thus, increasing resolution is a non-trivial technical challenge.

Interpolation resolution

Interpolated Resolution - image resolution, obtained as a result of processing (interpolation) of the scanned original. This artificial resolution enhancement technique usually does not result in an increase in image quality. Imagine that the actually scanned pixels of the image are moved apart, and “calculated” pixels are inserted into the resulting gaps, similar in some sense to their neighbors. The result of such interpolation depends on its algorithm, but not on the scanner. However, this operation can be performed using a graphic editor, for example, Photoshop, and even better than the scanner's own software. Interpolation resolution, as a rule, is several times higher than the hardware resolution, but practically this means nothing, although it may mislead the buyer. A significant parameter is the hardware (optical) resolution.
The scanner's technical data sheet sometimes simply indicates the resolution. In this case, we mean hardware (optical) resolution. Often both hardware and interpolation resolutions are specified, for example, 600x 1200 (9600) ppi. Here 600 is the hardware resolution, and 9600 is the interpolation resolution.

Line visibility

Line detectability is the maximum number of parallel lines per inch that are reproduced by the scanner as separate lines (without sticking together). This parameter characterizes the scanner's suitability for working with drawings and other images containing many small details. Its value is measured in lines per inch (Ipi).

What scanner resolution should you choose?

This question is asked most often when choosing a scanner, since resolution is one of the most important scanner parameters, on which the ability to obtain high-quality scanning results significantly depends. However, this does not mean that you should strive for the highest possible resolution, especially since it is expensive.
When developing scanner resolution requirements, it is important to understand the general approach. A scanner is a device that converts optical information about the original into digital form and, therefore, digitizes it. At this stage of consideration, it seems that the finer the sampling (the greater the resolution), the less loss of the original information. However, the scanned results are intended to be displayed using some output device, such as a monitor or printer. These devices have their own resolution. Finally, the human eye has the ability to smooth out images. In addition, printed originals produced by printing or a printer also have a discrete structure (printed raster), although this may not be noticeable to the naked eye. Such originals have their own resolution.
So, there is an original with its own resolution, a scanner with its own resolution, and a scanning result, the quality of which should be as high as possible. The quality of the resulting image depends on the set resolution of the scanner, but up to a certain limit. If you set the scanner resolution to be higher than the native resolution of the original, then the quality of the scanning result, generally speaking, will not improve. We don't mean to say that scanning at a higher resolution than the original is useless. There are a number of reasons when this needs to be done (for example, when we are going to enlarge the image for output to a monitor or printer, or when we need to get rid of moire). Here we draw attention to the fact that improving the quality of the resulting image by increasing the scanner resolution is not unlimited. You can increase the scanning resolution without improving the quality of the resulting image, but increasing its volume and scanning time.
We will talk about choosing the scanning resolution many times in this chapter. Scanner resolution is the maximum resolution that can be set when scanning. So how much resolution do we need? The answer depends on what images you want to scan and what devices you want to output to. Below we provide only approximate values.
If you are going to scan images for subsequent display on a monitor screen, then a resolution of 72-l00ppi is usually sufficient. For output to a regular office or home inkjet printer - 100-150 ppi, to a high-quality inkjet printer - from 300 ppi.
When scanning texts from newspapers, magazines and books for subsequent processing with optical character recognition (OCR) programs, a resolution of 200-400 ppi is usually required. For display on a screen or printer, this value can be reduced several times.
For amateur photographs, 100-300 ppi is usually required. For illustrations from luxury typographic albums and booklets - 300-600ppi.
If you are going to enlarge the image for display on a screen or printer without losing quality (sharpness), then the scanning resolution should be set with some reserve, i.e. increase it by 1.5-2 times compared to the above values.
Advertising agencies, for example, require high-quality scanning of slides and paper originals. When scanning slides for printing in 10x15 cm format, you will need a resolution of 1200 ppi, and in A4 format - 2400 ppi.
Summarizing the above, we can say that in most cases, a scanner hardware resolution of 300 ppi is sufficient. If the scanner has a resolution of 600 ppi, then this is very good.

Color depth and bit depth

Color depth, as we discussed in Chapter 1, is determined by the number of colors that can be transmitted (represented), or the number of digits (bits) of a digital code containing a description of the color of one pixel. One is related to the other by a simple formula:

Number of colors = 2 Number of bits

In the scanner, the electrical analog signal from the matrix of photosensitive elements is converted into a digital signal using an analog-to-digital converter (ADC). A digital signal that carries information about the color of pixels is characterized by its bit depth, i.e., the number of binary digits (bits) that encode information about the color of each pixel. The ADC and the quality of the scanner's light-sensitive elements determine the color depth it can provide. Today, all color flatbed scanners for general use provide at least 24-bit color depth (8 bits for each of the three basic color components). In terms of the number of colors, this is 2 24 = 16,777,216, which is quite enough. At the same time, there are scanners with 30-bit and 36-bit color representation (10 and 12 bits, respectively, for each component). In reality, you will work with 24-bit color, but with a larger ADC, having redundant information, you can color correct the image over a larger range without losing quality. Scanners with greater color depth (bit depth) allow you to preserve more shades and color gradations in dark colors. In addition, the low-order bits of the ADC output code usually fluctuate (contain conversion errors). The larger the bit depth of the ADC, the less the impact of conversion errors on the final result.

Optical density

Concept optical density(Optical Density) refers primarily to the original being scanned. This parameter characterizes the ability of the original to absorb light; it is designated as D or OD. Optical density is calculated as the decimal logarithm of the ratio of the intensities of incident and reflected (in the case of opaque originals) or transmitted (in the case of transparent originals) light. The minimum optical density (D min) corresponds to the lightest (transparent) area of ​​the original, and the maximum density (D max) corresponds to the darkest (least transparent) area. The range of possible optical density values ​​is between 0 (perfectly white or completely transparent original) and 4 (black or completely opaque original).
Typical optical densities for some types of originals are shown in the following table:

The dynamic range of a scanner is determined by the maximum and minimum values ​​of optical density and characterizes its ability to work with various types of originals. The dynamic range of a scanner is related to its bit depth (bit color depth): the higher the bit depth, the greater the dynamic range and vice versa. For many flatbed scanners, mainly those intended for office work, this parameter is not specified. In such cases, it is considered that the optical density value is approximately equal to 2.5 (typical value for office 24-bit scanners). For a 30-bit scanner this parameter is 2.6-3.0, and for a 36-bit scanner it is 3.0 and higher.
As dynamic range increases, the scanner is better able to convey gradations of brightness in very light and very dark areas of the image. On the contrary, with insufficient dynamic range, image details and smooth color transitions in dark and light areas are lost.

High resolution area

Some flatbed scanners may use an optional high-magnification lens. For this case, the technical data sheet indicates the dimensions of the part of the scanner’s working field in which scanning can be carried out with a resolution increased several times. This high resolution area(High Resolution Area, HRA) is usually much smaller than the working field.

Scanner software

The scanner software consists of two parts: a software interface and a graphics application package. The software interface provides control of the scanner, as well as its connection with third-party graphics programs. This is the so-called TWAIN module or scanner driver. It is said that TWAIN is an acronym for Toolkit Without An Interesting Name. Essentially, the TWAIN specification is an application programming interface standard for peripheral devices, including scanners. All manufactured scanners, digital cameras, and other data input peripherals must be TWAIN compatible. The TWAIN standard is supported by almost all graphics programs. IN Windows composition 98 and later versions include the TWAIN module. However, it is still recommended to install the TWAIN module supplied with the scanner (as is the best way to install the device manufacturer's driver).
By connecting the scanner to your computer and installing the TWAIN module, you get the opportunity to call the scanning procedure from a graphics program, for example, Photoshop, MS PhotoEditor, ACDSee, FineReader and many others. IN various programs Scan commands are called differently: Import>TWAIN, Acquire, Scan etc. B graphic editor Photoshop scanning command is selected in the menu File>Import (File>Import), in ACDSee - File>Acquire.
The TWAIN module has a user interface (dialog box) that allows you to configure scanning parameters. Appearance and the composition of the parameters of this module may be different, since scanner software manufacturers are limited only by the TWAIN standard itself, and no one is stopping them from improving the user interface. At the same time, there is a standard set of parameters that are present in all interfaces: selection of scanning mode and area, resolution, contrast, brightness, etc.
In addition to the TWAIN module in software The scanner usually includes some kind of, usually very modest in capabilities, graphics editor and, possibly, an optical character recognition (OCR) program. If you already have reputable programs installed on your computer, for example, the Photoshop graphics editor and the OCR FineReader system, then you do not need the additional software that comes with the scanner.
Note that there are scanners with their own software interface, different from TWAIN. In this case, the scan result is saved in a graphic format file (for example, TIFF), which can then be opened for viewing and editing in a graphics editor.

Scanning

Now that you have solved the problem of choosing a scanner, you can begin the fun part - scanning images, text, and even large objects to enter this information into the computer.

Configuring Basic Scan Settings

Let's look at the basic scanning parameters that can be configured using GUI TWAIN module. To be specific, we took as an example the interface of the MFS 1200SP scanner from Mustek. This is a single-pass CCD-based color flatbed scanner with an optical resolution of 600 ppi and an interpolation resolution of 9600 ppi, a color depth of 30 bits, connected to a computer via a SCSI adapter or its own interface board; A4 format; weight 1 kg. We, the authors of the book, have been using this scanner with pleasure for the last five years.
One typical way of working is to call the scanner dialog box from an application program, for example, from a graphics editor or OCR system. In this case, the scanning result will be immediately loaded into the editor, which is very convenient, since it is rare to do without at least slight correction of the scanned image. Note that some scanners turn on automatically when called from an application program, while others require a special switch to first turn on the power.

Rice. 120. Dialog box of the Mustek MFS 1200SP scanner

In Photoshop, the scanner is called by the command File> Import (File> Import)> Scanner_name. This opens the scanner's dialog box (the interface of its TWAIN module). In addition, another window may immediately open to preview the image and select the scan area.
If it does not open automatically, click the Prescan button in the scanner dialog box.
So, the scanner dialog box is on the monitor screen. Therefore, the scanner is installed on a computer and communicates with a graphics application program. Now you can start the actual scanning. Open the scanner lid, place the original (image down) on the work area (glass), close the lid and click on the Prescan button in the dialog box. As a result, the original scanned at a low resolution will appear in the preview window. This is a rough sketch of the original. The final scan has not yet been completed. Now you can select the scanning area, i.e. the area of ​​the original that you need. To do this, use the mouse to move and/or resize the frame that is visible in the background of the sketch. For more precise positioning of the frame, you can use the arrow keys while holding down the key . To scan a specified area of ​​the original using the current settings, click the Scan button. The scanner dialog box displays the image dimensions in the selected measurement units (pixels, cm, mm, or inches) as well as in kilobytes. As a result, the scanned image will be loaded into a new graphic editor window. You can process it if necessary and then save it in a graphics file (see Chapter 3). However, before scanning, do you usually adjust the settings? to get the result with the desired quality.
When setting parameters, they most often try to find a compromise between the quality of the resulting image (scan), its volume and scanning time. Typically, improving quality comes with an increase in memory footprint and time. The time investment becomes quite noticeable if you need to scan many originals in a row, for example, several dozen photographs or magazine pages. Scanning with a large resolution margin results in large amounts of memory and disk space. For example, a color photograph measuring 4x6 inches (approximately 10x15 cm) when scanned at 600 ppi will require more than 25 MB. Such large images are slow to process.
There are two main approaches to choosing scanning parameters. The first is that the quality of the result should be determined primarily by the characteristics of output devices and materials (monitor, printers of various types, printing equipment, printing on newsprint or coated paper, etc.). According to this approach, it is not worth creating a very high-quality image if its output will be produced by devices with low characteristics (“not the horse’s feed”). However, when changing the type of output device, it often turns out that you need to rescan the image, but with different parameter values. This approach is typical for office work, but is often used by designers. According to the second approach, when scanning you should obtain the maximum possible graphic information about the original, and only then process it in the editor in relation to the type of output device. The motto of this approach is: “what we have can always be abandoned.” This approach is used when it is not known in advance where and how the image will be used. It is typical, first of all, for designers.

Selecting a scan mode

First, you must select a Scan Mode that matches the type of original and/or the desired result. Typically, you can select the following modes:

• Color. Color image represented in RGB model
• Gray or Grayscale (in shades of gray). Images with smooth grayscale transitions
• Artline (Custom lines). Black and white image without halftones
• Halftone. A black and white image formed by regularly spaced dots of varying sizes or strokes (printed raster)

Basically, you can select any of the available scanning modes, regardless of the source image (original). For example, you can scan grayscale originals in color mode, and conversely, color originals can be scanned in grayscale mode. Choosing the best mode depends on both the original and your purpose. The mode characteristics in the list above serve primarily as guidelines for beginners. Experienced scanners easily select a mode depending on what they are dealing with and what they want to get. But they gained their experience from many experiments. We advise you to follow this path. Here are some general guidelines.

Rice. 121. Artline type image

Selecting scan resolution

The scanner, as noted above, has a resolution determined by its design features. It can be hardware (optical) or interpolation (reconstructed by computational means). Resolution is the maximum characteristic determined by the technical features of the scanner. However, when scanning an image, you can freely choose at what resolution it should be done in this particular case. Set resolution scanning may be less than or equal to the hardware (optical) resolution of the scanner, but may also exceed it. In the latter case, we can only talk about interpolation resolution. When the interpolation scanning resolution is set, in addition to the hardware itself, software conversions are used. The latter can be good or bad: it all depends on the conversion algorithm and the source image.
The quality of the resulting image, the amount of memory it occupies, and the scanning speed depend on the choice of scanning resolution. The quality of the image is, first of all, its clarity and smooth color transitions. In other words, a good scan should not look noticeably worse than the original.
The lower the resolution, the smaller the volume and time spent on scanning and vice versa. However, the quality of the result is more complicated. An analogy with the choice of a fishing net suggests itself here. Which net to choose - small or large mesh - depends on the size of the fish you want to catch. A scanner is a device that extracts information contained in an image. You cannot obtain more information than was in the original, but its description can be made redundant. Redundant descriptions of graphic information usually result in excessively large volumes of corresponding files. Ideally, we need to configure the scanner to extract as much as possible from the original graphic information, or at least not less than necessary.
The ability to choose the right scanning resolution comes with experience. However, experiments can be streamlined so that experience comes faster. For simplicity, images can be divided into two main types: photographs and drawings. Photography-type images (photographs, paintings, etc.) are characterized by a large number of shades and the smoothness of their transitions, and drawings (posters, drawings, engravings, etc.) are characterized by a relatively small number of shades, the presence of contours and increased contrast. Thus, the class of photographs includes not only photographs, and the class of hand-drawn graphics includes not only images created with a pencil, brush or pen. Sometimes there are images that are difficult to confidently attribute to one type or another. In this case, try this and that. Next, take several pictures of each type and scan them at different resolutions. Start with a minimum value of 72 ppi, increasing it in some increments to the optical resolution of the scanner. During the experiment, two resolution values ​​need to be fixed:

• starting from which the image quality becomes acceptable;
• from which the image quality remains virtually unchanged.

By averaging the data for each image type, you will get the resolution value you should set the first time you try to scan. When scanning, the situation is approximately the same as when using a professional camera, when you need to manually set the shutter speed, aperture and focal length (sharpness). An experienced photographer quickly assesses the subject and sets the necessary parameters for his camera. However, a professional will take several photographs of the same subject using slightly different camera settings. Likewise, scanning often requires multiple attempts.
When setting the scanning resolution, you should also consider whether the image will be enlarged when displayed on a monitor screen or when printed. As the size increases (i.e., when stretched), image quality, generally speaking, may deteriorate. In this case, an image is created with a certain amount of resolution. So, if you plan to enlarge the picture twice, then the resolution should be twice as large as what was sufficient for the original dimensions. On the other hand, if you intend to display a reduced image on a monitor or print, then perhaps the resolution should be reduced accordingly. Small images should have low resolution. This situation often arises in Web design, where the same image is often presented in two versions: small (thumbnail, thumbnail) - with low resolution, and large - with high resolution.
If your computer has a large enough memory and the time spent on scanning is not critical for you, then we can recommend setting the resolution equal to the hardware (optical) resolution of the scanner. Then, if necessary, the resolution of the resulting image can be reduced using a graphics editor. In Photoshop, this is done using the Image>Image Size command. However, increasing the resolution using a graphics editor does not improve image quality. When the resolution is reduced (downsample), pixels are removed from the image and, thus, the amount of graphic information is reduced. As the resolution increases, the graphics editor adds pixels, using some interpolation algorithm (taking into account the values ​​of neighboring pixels) to calculate their values.

Rice. 123. Window for setting image sizes and resolution in Photoshop

Generally speaking, it is better to optimize the final image using a powerful graphics editor such as Photoshop. Working with graphics from the point of view of a designer (artist) usually occurs in the space of a graphics editor, and not in scanner software. But this does not mean that the scanner software (TWAIN interface) should be forgotten forever. Although they were designed primarily to allow the user to work with the scanner without depending on their existing graphics software package, they can sometimes be used effectively even before Photoshop shows its full power.
The following table provides an example of the memory consumption of scanning a 4x4 inch (11x11 cm) image in various modes and resolutions.

Image type	Image volume at different resolutions
	100 ppi	150 ppi	300 ppi	600 ppi
Color	469 KB	1 MB	4.12 MB	16.5 MB
Gray	156 KB	352 KB	1.37 MB	5.5 MB
Artline	19.5 KB	44 KB	175 KB	703 KB

To conclude our conversation about scanning resolution, let us recall the circumstances that must be additionally taken into account when choosing a resolution. Firstly, if the scanned image is intended to be printed using a laser or inkjet printer, then the set resolution may be 3-4 times less than the printer resolution. This is true primarily for color or halftone (grayscale) images. For Artline or Halftone images, the scanning resolution should be set to the same as the printer resolution if possible. For example, if you have a regular inkjet printer with a resolution of 300 ppi, then... Try scanning the image at 75 ppi first. If the result is unsatisfactory, increase the scanning resolution by 2 times. Secondly, resolution often needs to be changed when scanning images from high-quality print media. The reason for this is the so-called moire - the effect of the interaction of several periodic structures (in this case, discrete scanning structures and a printed raster). Often this optical side effect is eliminated by choosing a higher scanning resolution. Moire suppression will be discussed in more detail below. Thirdly, when choosing the initial and, if necessary, subsequent scanning resolution values, you should strive to ensure that the selected resolution is a multiple of the scanner’s optical resolution divided by a whole power of two:

Set resolution = Optical resolution: 2 i, where i = 0, 1,2, 3,...

For example, if the scanner's optical resolution is 600 ppi, then the scan resolution set should be as close as possible to 600, 300, 150, 75 ppi. This choice helps to achieve the greatest clarity of the scanning result.

Image tone correction

Scanner software usually allows you to set tone correction parameters - brightness, contrast, gamma and others (for example, black and white levels). Being able to configure these settings before scanning is very important.
It is especially useful to adjust the black and white levels if the original is low-contrast and sluggish, that is, there are no areas of high and very low brightness, and all the graphic information is concentrated in the midtones. In such cases, white and black sheets of paper are placed next to the original, and the scanning area is selected to capture these special attachments. Later they can be removed from the scan result using a graphic editor. This technique allows you to correct the result automatic settings levels of black and white that the scanner produces during preliminary scanning.
If the scan result is too dark or light, then it is better to adjust the gamma parameter (if, of course, there is such an opportunity) than brightness and contrast. Recall that gamma affects the midtones of an image, leaving the darkest and lightest pixels unchanged, i.e., maintaining the boundaries of the pixel brightness range. In other words, image correction using the gamma parameter is more gentle.

Rice. 124. Window for setting tone parameters of the MFS I200SP scanner from Mustek

When tonal correction is carried out before the final scan, it should be remembered that it is done to configure the scanner in order to extract as much graphic information from the original as possible. A large amount of graphic information is not always expressed in the form of a bright and contrasting image. In the case of photographs, for example, the contrasting scanning result that beginners usually strive for is most often due to losses in the original information. If you intend to further process the image in the editor, then you should not overincrease the brightness and contrast using the scanner software, since this can result in the loss of fine details in dark and very light areas.
Please note that your scan settings are retained until you change them again. To restore the default settings, click the Reset button, or to view the results of your settings in a preview window, click the Preview button.
The scanning result can be corrected if necessary in a graphic editor, for example, Photoshop. Usually this cannot be avoided, unless we are talking about rough scanning with fax quality.

Fighting moire

It is not uncommon for images scanned from printed originals that were created using a printing method to have a fine grid pattern appear. Moreover, it is usually more noticeable the higher the quality of the original. This effect is called moire. Essentially, moire is an interference pattern resulting from the combination of a typographic screen with other regular structures, such as the pixel structure of the screen and the discrete scanning process. Take two combs with different tooth frequencies, place them on top of each other and look in transmitted light, moving one comb slightly relative to the other. The observed optical effect is what is called an interference pattern.

Rice. 125. Model illustrating the mechanism of moiré occurrence

Graphic elements with a periodic structure (such as microphone or mosquito nets, checkerboard patterns, parallel or radiating lines) can also cause moire. Moiré can also occur on line art. But still with most likely it appears when scanning printed images.

Rice. 126. A fine grid in the image, especially in its bright areas - moiré

So, moire can appear if the original has a printed raster, and the scanning resolution is close to a multiple of the lineature of the printed raster. This most often happens when the selected resolution is close to the lineature itself. Lineature (spatial frequency - screen frequency) is measured as the number of lines per inch (Ipi). This is a characteristic, first of all, of printing devices and, secondly, of images obtained on them. Newspapers usually have a lineature of 85 Ipi, high-quality printing - 133 Ipi, premium quality - 300 Ipi (there are few lineature options).
Before scanning a printed original, it is useful to know its lineature and select a scanning resolution that is slightly (5-10%) different from it. However, in practice, if you do not know the lineature of the print or do not want to waste time figuring it out, choose a scanning resolution that is simply 1.5-2 times larger than the expected lineature. For example, when scanning newspaper-quality originals, the resolution is set to 100-170ppi; when scanning high-quality print images - more than 200 ppi. Sometimes it is recommended to scan at the maximum (optical) resolution of the scanner. This is quite consistent with the general idea of ​​combating moire by choosing the appropriate resolution. Additionally, this tip is very good for high-quality typographic prints. By following it, you simultaneously achieve maximum clarity and get rid of moire. If in this case the moire does not disappear, try to slightly change (reduce) the resolution. However, we should not forget that when choosing a resolution, other criteria must be taken into account (clarity, volume, time, need for enlargement).
Another way to combat moire is to tilt the original slightly, 5-15 degrees. However, its subsequent alignment using a graphic editor can again lead to the appearance of moire. For some pictures this technique is quite acceptable.
Most scanner software dialog boxes have a command (filter) specifically designed to suppress moire. It can be called differently: Descreen, Demoire pattern, etc. However, they should be used with caution, since they reduce the clarity of the image (be careful not to throw out the baby with the bathwater!). However, a technique based on blurring the image and then restoring clarity in a graphics editor is used quite often. In Photoshop, to remove moire, you first add monochromatic noise to the image (Filter menu), then apply a Gaussian blur (Gaussian Blur filter), and finally restore clarity using the Sharpen or Unsharp Mask filter.
We have already noted in this chapter that moire is more likely to occur on high-quality printed originals than on acceptable-quality images on newsprint due to something called dot gain (ink bleeding). However, often even on poor paper the printed raster is clearly visible. Inkjet printers use random raster technology, which virtually eliminates the appearance of moire.
So, the risk of moire appearing when scanning printed prints is very high. Moire is not a scanner defect, but a manifestation of the natural interaction of light with regular structures along the path of its passage (in optics there is a section specifically devoted to the passage of light through gratings). Moire can be suppressed by choosing the appropriate resolution, as well as by using blur filters at the scanner or graphics editor software level. You can also reduce the size of the image to make the moire less noticeable.

Newton's rings

When scanning films (transparent originals), so-called Newton's rings appear. This is concentric rainbow interference. They arise when scanning warped films and, mainly, as a result of reflection of light in many tiny droplets of moisture located on the surface of the film. Experienced scanners note that Newton's rings appear more often in late autumn and winter. Therefore, use special frames for films, and also dry them (for example, with a regular hairdryer) before scanning. When drying, it is necessary, of course, to ensure that the emulsion is not damaged due to overheating.

Scanning photos

In practice, photographs are most often scanned. Here we will talk about scanning photographs taken using conventional cameras and printed on photographic paper. The average computer user purchases a scanner mainly for this purpose. Color photographs taken sometime in the 70s and 80s fade quickly. They cannot stand any comparison with photographs from the early 20th century. For example, we have magnificent examples of prints from 1905. Over time, they have experienced only some mechanical damage (scratches, paper bends), but the remaining fragments delight in their clarity. Modern photographic prints will probably retain graphic information for 20-25 years. That's why The best way Save your home photo archive securely and for a long time - scan pictures and record them on magnetic media or laser disks.
When scanning photographs taken using conventional cameras and printed on photo paper, problems with moire, as a rule, do not arise. The choice of resolution is determined only by the required clarity (sharpness), as well as the size of the image. If you are going to increase it when displaying or printing, then the scanning resolution should be selected with some margin. We have already talked about this several times.
Ordinary amateur photographs are scanned, as a rule, at a resolution of 75-150 ppi if they are intended to be displayed on a monitor screen. For printing, the resolution should be set approximately equal to the printer resolution. The scanning result has to be slightly processed in a graphics editor (adjust brightness, contrast, color balance, etc.). If we are going to send scanned photographs by email to someone who knows how to work with graphics, then most often we do not do the processing, hoping that the recipient will do it as he needs. Thus, we send it the original graphical information. In Web design, on the contrary, it is necessary to process the scan result so that it looks appropriate and takes up as little disk space as possible (loads into the browser faster).
One of the main problems with scanning prints on photo paper is the so-called “shadow gaps”. In other words, the scanner is unable to capture detail in the dark areas of the image. This problem occurs due to the insufficient dynamic range of optical density of inexpensive office scanners. Try printing your photos in a softer developer or on less contrasting paper. If the photo has not lost its black color saturation, and the detail in the shadows has improved, then you are on the right track. Particularly difficult is scanning images taken in the so-called low key, when the main halftone transitions are concentrated in the shadow area (dark areas). It is precisely these photographs, taken at night in the light of a flash or during the day in dim lighting, that are very often created as works of art, and not as photographic documents. Such photos are usually preferred in Web design. In this case you may have to choose one of two possible solutions:

• print photos as usual, and then increase the contrast of dark areas in a graphics editor (Curves and Levels tools in Photoshop);
• print photos lighter and softer than usual (this moves the shadow areas into a more favorable range for the scanner), and then increase the overall contrast of the image in a graphics editor (Levels and Brightness/Contrast tools in Photoshop).

Scanning volumetric objects

A rich source of source material for artistic compositions is scanning three-dimensional objects. But not all scanners can do this with acceptable quality. CCD scanners (i.e. scanners based on a CCD matrix) can do this, but CIS scanners cannot. Although the depth (third dimension) of three-dimensional originals achievable by the scanner does not exceed a few centimeters, the resulting effect can be very interesting. However, we will immediately warn you that attempting to scan your face will most likely lead to eye burns and loss of vision.
When scanning large objects, you usually have to remove the cover, which allows access to light from external sources. This may degrade the image quality. Therefore, use a white or black cloth to cover the item being scanned.
The most difficult objects for the scanner to detect are objects that are too dark and very shiny. Details in dark objects are difficult to highlight. In the case of shiny objects, you need to choose their location in such a way as to reduce unnecessary glare. This applies, in particular, to books with gold embossing. However, gold pieces on book covers usually appear dark when scanned rather than shiny. To correct this, the plane of the book is placed at a certain angle to the plane of the scanner's working field. To do this, you can place something under some corner of the book, for example, a match or a CD box.
The following figures show examples of borderline cases of scanning three-dimensional objects - a model of a steam locomotive and a clock. The clock image was not processed in a graphics editor. But the image of the locomotive had to be, as they say, “extracted” in Photoshop, since the original was made of black matte plastic, which does not reflect light well. Of course, to improve the reflective properties, we could moisten the locomotive with vegetable or machine oil, but we didn’t, because we still needed it, and, moreover, we didn’t want to inadvertently stain the glass of the scanner’s working field.

Rice. 127. The black plastic remote control is a difficult original for a scanner due to its weak reflective properties.

Rice. 128. The watch is in a shiny metal case. The glare is quite acceptable

The average scanning object in terms of reflective properties is a printed circuit board. Such images can be used, for example, as illustrations of books and articles.

Rice. 129. Network card scanned at 300ppi without special settings scanner and image processing in a graphic editor

You can experiment with using a mirror when scanning three-dimensional objects. The scanning object is placed on the glass of the working field, and above it, at a certain angle, is a mirror. The result must contain, in addition to the object, its mirror image.

Scanning texts

In practice, you often have to enter information into a computer from text documents, for example, from books; magazines and newspapers. To speed up this process, scanners are used. However, the result of scanning, generally speaking, is simply a graphic image (drawing), although it contains letters (drawn). If you saved it in a graphic format file, you can then open it only in an editor or graphics viewer. Although it is in principle possible to edit texts in a graphic editor, in practice, of course, no one does this (besides, an image of a text is not a text from a computer’s point of view; it will have to be edited as a drawing). In addition, storing text information in graphic format files is the height of wastefulness in using disk space. Text information along with illustrative graphics are scanned to be transmitted optical character recognition (OCR) program, for example FineReader or CunieForm.

Rice. 130. FineReader main window

With the help of an OCR program, the scan result will be divided into text and pictures (if any) and can be saved in a file format accessible to text or spreadsheet editors, for example, MS Word or MS Excel.
You can scan first Text Document and save the result in a graphic format file, such as JPEG or TIFF, and then open it in an OCR program and perform character recognition. But you can do it differently: scan directly from the OCR program, and then perform recognition. We prefer this way. By the way, many OCR programs allow scanning and recognition using one command. However, in the case where you scan many fragments and only recognize some of them, it is better to separate these processes.
Modern OCR programs cope with the situation when the original is not placed very straight on the scanner's working field. This is convenient because you can just casually toss the originals onto the work area without worrying too much about their alignment. However, we do not advise you to abuse this opportunity.
Some OCR programs require that the text document be scanned in Artline mode. Reputable and modern OCR programs will not burden you with this limitation.
If the original is just text without graphics, then you need to scan it in Artline or Gray modes. Artline mode is typically used for high-quality prints of text without illustrations, such as those produced using a laser or inkjet printer. The scanning resolution is selected depending on the font size. For font sizes 12 pt or less, the resolution in Artline mode is set to about 400-450 ppi. For larger fonts, the resolution can be reduced to 200-300 ppi. Gray mode requires 8 times more memory per pixel than Artline mode. However, when scanning texts in this mode, you can set a lower resolution than in Artline mode - approximately 150-300 ppi, depending on the size and typeface of the font. If the amount of memory occupied and scanning time are not critical for you, then we recommend choosing the Gray mode. When scanning documents that contain pictures in addition to text, you should select the Gray mode (or Color if you want to obtain color images of pictures). These scanning modes provide more graphical information about the original, which is important for high-quality character recognition.
The OCR program uses dictionaries when recognizing text in a graphic image. different languages, which allows it to correct scanning defects. However, OCR errors still remain. Before initiating the actual recognition, review the scan result. First of all, you should pay attention to the quality of display of letters such as “e” and “s”, “k” and “n”, “l” and “p”, “i” and “1”, “r” and “r” " If there are many cases of mutual substitution in the listed pairs of letters, it is better to repeat the scan at a higher resolution. If the recognition result contains too many errors, we also recommend repeating the scanning procedure at a higher resolution.
If you have to scan many pages from text information of approximately the same quality, it is advisable to first slowly select the correct scanning parameters. This can be done by experimenting on a small fragment of the document. Having selected the optimal parameter values, you can then put scanning and recognition on stream. Scanner and OCR software usually have a special command that sets the batch mode (Buth mode).

SCANNING OPTICAL - ELECTRONIC IMAGING SYSTEMS (SCANERS)

Scanning filming systems (scanners) differ from others primarily in the principle of image construction, which is constructed by line-by-line scanning (viewing) of the area.

Scanning systems use various types of electromagnetic radiation receivers: thermal (thermoelectric) and photonic (photoelectric). Thermal ones operate on the basis of converting thermal energy into an electrical signal; in photonic systems, the signal level is determined by the number of absorbed photons. The most widely used are scanners in which CCD lines (devices with a charging mixture) serve as receivers. Different types of sensors have different spectral sensitivities and cover the spectral range from the visible zone to the far infrared zone. The choice of radiation receiver and its spectral sensitivity depends on the spectral interval of the survey.

Structurally, the scanner consists of an optical system, photoelectronic converters, and an image receiving and recording device. With the help of scanners, an image is formed consisting of many individual, sequentially obtained image elements - pixels within stripes (lines, scans). Pixel size determines the detail (terrain resolution) of the image.

Scanning of the area is carried out in one direction due to the forward movement of the aircraft (satellite), and in the other (perpendicular to the flight line) due to the rotation or oscillation of the prism (mirror). The oscillatory movement of the prism (mirror) in combination with the movement of the aircraft (satellite) provides continuous sequential coverage of a certain strip of terrain, the size of which depends on the aperture (the active opening of the optical system of the lens) of the scanner and the flight altitude of the aircraft or satellite. The width of the strip of terrain being photographed is determined by the scanning angle of the scanner, and the linear resolution of the terrain (scan width, pixel size) is determined by the instantaneous viewing angle. For overview scanners, the scanning angle reaches, while for highly informative (detailed) scanners, it is less. Accordingly, the instantaneous angle of view is set from several degrees to tenths of a minute. The scanning angle and instantaneous viewing angle, respectively, the shooting range and terrain resolution, are interdependent quantities. The higher the resolution, the narrower the shooting band. So, when shooting from space at a resolution of 1-2 km. They record a strip of terrain of several thousand kilometers, and with a resolution of 20-50 m, the width of the survey strip does not exceed 100-200 km.

Optical-mechanical scanners can be single-channel or multi-channel (2 or more). Typically, scanners operating in the visible and IR ranges (0.5 - 12 microns) are used to photograph the earth's surface. The result of radiation registration when shooting using the optical-mechanical scanning method is a matrix of multidimensional vectors. Each vector displays a certain elementary area (pixel) on Earth, and each of its components corresponds to one of the spectral channels.

When shooting in the visible and near-IR ranges (0.4 - 3 microns), photoelectric radiation detectors are used, and in the middle and far-IR ranges (3 -12 microns) - thermoelectric radiation detectors. Photoelectric receivers include electronic devices whose operation is based on external (vacuum photocells, photomultipliers) and internal (semiconductor photoresistors, photodiodes, etc.) photoelectric effects. Thermoelectric detectors are based on thermionic emission; they respond to absorbed radiation through heating the sensitive element, which allows them to record IR thermal radiation in a wide spectral range. Thermoelectric receivers include bolometers, radiation thermoelements (thermocouples), etc. Thermal imaging is carried out with scanning radiometers at night and during the day.

Scanners are equipped with several sensors that allow them to obtain images simultaneously in different spectral channels. The information obtained during the scanning process is transmitted in the form of a digital image via a radio channel to a receiving point or recorded on board on a magnetic medium. The shooting materials are transferred to consumers in the form of recordings on magnetic media, for example on CD disks, with subsequent visualization at the image processing sites.

In terms of their geometric properties and local resolution, scanner images obtained by first-generation camera systems were inferior to photographs. However, the high sensitivity of scanner radiation detectors makes it possible to perform imaging in narrow (several tens of nanometers) spectral intervals, within which the differences between some natural objects are more clearly expressed. There is no “noise” in the digital data obtained using scanners, which inevitably appears when photographing and darkroom processing of film materials.

The main method of converting paper documents into electronic form is scanning graphic image scanner.

Scanner

universal And special.

Universal scanners provide input of text and graphic information in color or black and white format. Among the universal scanners, the following types stand out:

· Hand scanner– the simplest type of scanners, which gives the least quality image. This type of scanner has no moving parts and scanning is done by manually moving the scanner over the surface of the document. Their disadvantage is a very narrow scanning bandwidth (a standard sheet of paper has to be scanned in several passes), as well as high requirements for the scanning process itself.

· Sheet-fed scanner– allows you to scan a standard size sheet of paper in one operation. The design is similar to a fax machine: the original is pulled in by special rollers (like in a printer) and scanned as it moves past a stationary photosensitive matrix. While providing high quality scanning, these scanners do not allow you to process books and magazines without separating them into separate pages.

· Flatbed scanner– most universal device, suitable for most tasks and allowing you to scan any documents (single sheets, books, magazines, etc.). Under the scanner cover there is a transparent base on which the document is placed. The scanning unit moves along the document inside the scanner body. The duration of scanning a standard typewritten sheet ranges from one to several seconds. Flatbed scanners provide the best quality and maximum convenience when working with paper documents.

Many models of flatbed scanners have the ability to install an automatic document loader from a stack, as well as connect a slide module that “digitizes” slides and negative films for professional photography or printing tasks.

Special types of scanners are designed to perform special functions. These include the following:

· Drum scanners provide the highest scanning resolution. The original is fixed to the drum using special clamps or lubricant, and scanning is carried out by line-by-line movement of the lens along the drum rotating at a speed of about 1000 revolutions per minute. The use of a halogen light source, the luminous flux from which is concentrated on a pinpoint area of ​​the drum, eliminates the influence of interference and processes the entire range of originals with the highest quality.

· Form scanners - special scanners for entering information from completed forms. This is a type of sheet-fed scanner. Using such devices, data is entered from questionnaires, questionnaires, and ballot papers. Scanners of this type do not require high resolution, but very high performance. In particular, for scanners of this type, the feeding of paper sheets into the device is automated.

· Bar scanners - a type of hand-held scanners designed to read barcodes from product labels in stores. Bar scanners allow you to automate the process of calculating the cost of purchases. They are especially convenient in retail premises equipped with electronic communications and making payments to customers using electronic means of payment ( credit cards, smart cards, etc.).

· Slide scanner- a specialized version of a flatbed scanner designed for digitizing slides and negative films for professional photography or printing tasks. The slide or film is inserted into the receiving slot and moves between the backlight and the lens. The parameters of the output image are sufficient for a photo album or printing reproduction.

Despite such a variety of types of scanners, the design and principles of their operation are largely similar. As an example, let's look at how a flatbed scanner works, simplified structural scheme which is shown in Fig. 10.

The main elements of a flatbed scanner are:

· substrate(cover) – covers the original from which scanning is performed. It is made of black material that absorbs the visible part of the spectrum as much as possible in order to prevent the appearance on the resulting image of all kinds of glare of light reflected from objects placed behind the original;

·
glass, on which the scanned original is placed;

· LED matrix– a set of sensors (photosensitive elements) arranged in one line for black and white scanning or in three lines for color scanning in one pass. Charge-coupled devices are used as photosensitive elements ( CCD – CCD –Charge Coupled Device). The main purpose of the matrix CCD– divide the luminous flux into three components (red, green and blue) and convert the light level into a voltage level;

· optical system– consists of a lens and mirrors (or prism) and is designed to project the light flux reflected from the scanned original onto an LED matrix that separates color information. Typically a single focusing objective (or lens) is used that projects the full width of the scanning area onto the full width of the CCD;

· lamp– a light source located on a moving carriage and illuminating the page being scanned. Modern models use cold cathode lamps ( Cold Cathode Lamp), providing a luminous flux of a given intensity and having increased durability characteristics. Focused on professional work with color, the scanners contain self-calibration circuits based on the intensity of the light flux from the lamp and maintaining the stability of the light flux when temperature changes;

· stepper motor– provides movement optical block, which includes a lamp, optical system and LED matrix;

· signal amplification unit– amplifies analog voltages from the outputs of the CCD matrix, carries out their correction and processing;

· analog-to-digital converter (ADC) – converts analog voltages into digital code;

· scanner controller– ensures the reception of commands from the computer and the issuance of received digital codes to it.

The scanning process is quite simple. The original (sheet of document, unfolded book, etc.) is placed on transparent fixed glass and covered with a lid. When a scanning command is sent from the computer, the lamp turns on and the scanning carriage with the optical unit begins to move along the sheet. Bright light from the lamp falls on the scanned original, and then, reflecting from it, the light flux is focused optical system and goes to the signal receiver - a CCD matrix, which separately perceives the red, green and blue components of the spectrum. The analog voltages obtained at the output of the CCD matrix, proportional to the spectral components, are amplified and fed to an analog-to-digital converter, which performs digital encoding. From the ADC, information comes out in a binary form “familiar” to the computer and, after processing in the scanner controller, through the interface with the computer it enters the scanner driver - usually the so-called TWAIN- a module with which application programs already interact.

! To see how a flatbed scanner works, put on headphones and run double click mouse over this picture:

Main parameters and characteristics of scanners:

1. Scan Resolution (Scanning Resolution) characterizes the value of the most small parts images transmitted during scanning without distortion. Usually measured in dpi (dot per inch) - the number of individually visible dots per inch of the image. There are several types of resolution specified by the scanner manufacturer.

· Optical resolution is determined by the density of elements in the CCD array and is equal to the number of elements in the CCD array divided by its width. It is the most important parameter of the scanner, determining the detail of the images obtained with its help. In mass models of flatbed scanners it is usually equal to 600 or 1200 dpi. Scanning should always be performed at a multiple of optical resolution to minimize interpolation distortion.

· Mechanical resolution determines the positioning accuracy of the carriage with the CCD ruler when moving along the image. Mechanical resolution is usually 2 times greater than optical resolution.

· Interpolation resolution obtained by 16x software magnification of the image. It carries absolutely no additional information about the image in comparison with the real resolution, and in specialized packages the scaling and interpolation operation is often performed better than by the scanner driver.

2. color depth, or bit depth (Color Depth) characterizes the number of bits used to store information about the color of each pixel. Black and white scanners have one bit, monochrome scanners usually have 8 bits, and color scanners have at least 24 bits (8 bits to store each of the RGB color components of a pixel). The number of colors reproduced by a 24-bit scanner (8 bits per channel) is 2 24 = 16,777,216. More advanced scanners may have a bit depth of 30 or 36 (10 or 12 bits per channel). Moreover, their internal bit depth may be higher than the external one: “extra” bits are used to perform color correction of the image before transferring it to a computer, although this practice is mainly typical for cheap models. Professional and semi-professional scanners also have external bit depths of 30, 36, 42 bits or higher.

3. Optical Density Range (Optical Density Range) is the dynamic range of the scanner, which is largely determined by its bit depth. It characterizes the scanner’s ability to correctly transmit images with large or very small variations in brightness (the ability to scan “a photo of a black cat in a dark room”). Calculated as the decimal logarithm of the ratio of the intensity of the light incident on the original to the intensity of the reflected light, and is measured in OD(Optical Density) or simply D: 0.0 D corresponds to perfect white, 4.0 D corresponds to perfect black. For a scanner, this range depends on the bit depth: for a 36-bit scanner it does not exceed 3.6 D, for a 30-bit scanner - 3.0 D. Scanned images usually have a range of up to 2.5 D for photographs and 3.5 D for slides . Cheap 24-bit flatbed scanners have a dynamic range of 1.8-2.3 D, good 36-bit ones - up to 3.1-3.4 D.

4. Scan area size. For flatbed scanners, the most common formats are A4 and A3, for roll scanners - A4, and for hand-held scanners, the scanning area is usually a strip 11 cm wide.

5. Matching the colors of the original image to its digital copy. Today, one of the most common color accuracy management systems is that based on profiles. International Color Consortium (ICC), describing the features of color rendering various devices. The process of creating an ICC profile is based on scanning a specially made test table and comparing the results obtained with the standard. Based on the results, the device characteristics that are taken into account by the driver and applications are determined. Expensive scanner models use special software and hardware systems for color calibration.

6. Driver quality. All modern scanners communicate with Windows applications using a software interface TWAIN, however, the set of functions provided by the driver may vary; it should definitely be clarified when choosing a scanner. The most important among them are:

· the ability to preview an image with a choice of scanning area and number of colors;

· ability to adjust brightness, contrast and non-linear color correction;

· the ability to suppress moire when scanning images with a printed raster;

· the possibility of simple image transformations (inversion, rotation, etc.);

· network scanning capability;

· possibility of automatic correction of contrast and color rendering modes;

· the ability to operate the scanner (in combination with a printer) in copier mode;

· color calibration capabilities for both the scanner and the entire system;

· Batch scanning capabilities;

· the ability to fine-tune filters and color correction parameters.

7. Quantity and quality of software included with the scanner. Traditionally, image processing software is supplied with scanners ( Adobe PhotoDeluxe or Photoshop LE, ULead Photo Impact etc.) and an optical text recognition program ( OCR - Optical Character Recognition). The software package usually includes two such programs: English ( Xerox TextBridge or Caere OmniPage Pro) and an OCR program designed to recognize Russian texts - one of the versions FineReader production ABBY Software.

High-quality professional and semi-professional flatbed scanners are produced by companies Agfa, Linotype-Hell, Microtek(a number of models are known under the NeuHouse OEM logo), Umax; Equipment designed for mass users is produced by companies Artec, Epson, Genius, Hewlett-Packard, Mustek, Plustek, Primax and etc.

For various types of scanners in table. 3 shows typical values ​​of these parameters.

Table 3. Parameter values ​​for the main types of scanners

The following interfaces are currently used to connect scanners:

· own (Proprietary) scanner developer interface, used in early models of flatbed and hand-held scanners and was a specialized board on a bus ISA, which required a driver to operate;

· With EPP parallel port (LPT, or ECP) the youngest models in the families of flatbed scanners are produced various manufacturers. Scanners with such an interface, as a rule, have mediocre characteristics and are designed to perform simple work;

· SCSI interface is a standard for connecting high-quality and high-performance devices, ensures cross-platform compatibility of the scanner and its low dependence on changing the operating system. SCSI scanners usually come with a SCSI bus card ISA, although such a scanner can also be connected to full-featured SCSI controllers on the bus PCI. Most 30- and 36-bit scanners with a resolution of 600 dpi and higher are available with this interface;

· USB interface is an interface for connecting scanners, actively recommended by the specifications PC98 And PC99. Convenience of a single interface for different devices and fairly high throughput have led to the fact that most scanners for non-professional use are produced with this interface.

For data entry in three-dimensional modeling and computer-aided design systems (CAD, or CAD/CAM - Computer-Aided Design/Modeling) is used Graphics tablet (Digitizer – digitizer)- an encoding device that allows you to enter a two-dimensional, including multicolor, image into a computer in the form of a raster image.

The graphics tablet includes a special pointer (pen) with a sensor. Its own controller sends impulses along a grid of conductors located under the surface of the tablet. Having received two such signals, the controller converts them into coordinates transmitted to the PC. The computer translates this information into coordinates of a point on the monitor screen corresponding to the position of the pointer on the tablet. Drawing tablets are sensitive to pen pressure, converting this data into line thickness or shade.

A serial port is usually used to connect a tablet. Common parameters are a resolution of about 2400 dpi and high sensitivity to pressure levels (256 levels). Graphic tablets and digitizers are produced by companies CalComp, Mutoh, Wacom and others.

For handwritten information input devices, the same operating scheme is typical, only the entered letter images are additionally converted into letters using special program recognition, and the size of the input area is smaller. Pen input devices are more often used in subminiature computers PDA (Personal Digital Assistant) or HPC (Handheld PC), which do not have a full keyboard.

CONCLUSIONS

1. Keyboard is the main device for inputting information into a PC. It is a set of mechanical sensors that sense pressure on the keys and close a certain electrical circuit. The two most common types of keyboards are: mechanical and with membrane switches.

All keys are divided into groups: alphanumeric keys, intended for entering texts and numbers; cursor keys(this group of keys can also be used to enter numeric data, view and edit text on the screen); special control keys(switching registers, interrupting program operation, printing screen contents, rebooting the PC OS, etc.); function keys, widely used in service programs as control keys.

The most common standard for symbol key layout is the layout QWERTY (YTSUKEN), which can be reprogrammed to another if desired.

2. A convenient tool for controlling the cursor is a device called mouse. The vast majority of computer mice use optical-mechanical principle of displacement coding. In laptop PCs, a trackball, touchpad, and trackpoint are used instead of a mouse.

3. Used to visually display information video system computer, including monitor(display), video adapter And software(video system drivers). Monitor (display) is a device for visually displaying text and graphic information on a kinescope screen (cathode ray tube - CRT) or liquid crystal screen (LCD screen).

TO basic parameters of monitors include: monitor frame rate, line frequency, video signal bandwidth, image formation method, monitor screen phosphor grain size, monitor resolution, monitor screen size.

Video adapter(video card, video controller) is an internal PC device designed to store video information and display it on the monitor screen. It directly controls the monitor, as well as the process of displaying information on the screen by changing the horizontal and vertical scanning signals CRT monitor, brightness of image elements and color mixing parameters.

4. Printers (printing devices)– devices for outputting data from a computer, converting ASCII information codes into corresponding graphic symbols (letters, numbers, signs, etc.) and recording these symbols on paper.

Printers differ from each other in various ways: chromaticity– black and white and color; By way of forming symbols– character printing and character synthesizing; By operating principle– matrix, thermal, inkjet, laser; By printing method– percussive, unaccented; By ways to form strings– serial, parallel; By carriage width– with a wide (375-450 mm) and narrow (250 mm) carriage; By print line length– 80 and 132-136 characters; By character set– up to the full set of ASCII characters; By print speed; By resolution.

5. The main method of converting paper documents into electronic form is scanning- technological process that results in the creation graphic image a paper document, like a “digital photograph” of it. Scanning is carried out using a special device called scanner.

Scanner is an optical-electronic-mechanical device that is designed to convert the visual image of a paper document into graphic file, preserving raster image source document and transferred to a computer for subsequent processing (recognition, editing, etc.).

According to their purpose, scanners are divided into universal(hand, sheet and flatbed) and special(drum scanners, form scanners, bar scanners, slide scanners).

The main characteristics of scanners: scanning resolution (optical, mechanical and interpolation), color depth (bit depth), range of optical densities, size of the scanning area, color matching of the original image to its digital copy, quality of drivers and included software.