All types and types of optical drives: their characteristics and which ones exist? Optical disk: what is it and all its characteristics? What layers does an optical disc consist of?

External memory

Optical discs

Optical (laser) discs are currently the most popular storage media. They use the optical principle of recording and reading information using a laser beam.

Information on a laser disk is recorded on a single spiral-shaped track, starting from the center of the disk and containing alternating sections of depressions and protrusions with varying reflectivity.

When reading information from optical disks a laser beam installed in the disk drive falls on the surface of the rotating disk and is reflected. Since the surface of the optical disk has areas with different reflection coefficients, the reflected beam also changes its intensity (logical 0 or 1). The reflected light pulses are then converted into electrical pulses using photocells.

In the process of recording information on optical discs, various technologies are used: from simple stamping to changing the reflectivity of areas of the disc surface using a powerful laser.

There are two types of optical discs:

CDs (CD - Compact Disk, CD), on which up to 700 MB of information can be recorded;

DVDs (DVD - Digital Versatile Disk, digital universal disk), which have a significantly larger information capacity (4.7 GB), since the optical tracks on them are thinner and are placed more densely.
DVDs can be double-layered (8.5 GB capacity), with both layers having a reflective surface that carries information.
In addition, the information capacity of DVDs can be further doubled (up to 17 GB), since information can be recorded on two sides.

Currently (2006), optical discs (HP DVD and Blu-Ray) have entered the market, the information capacity of which is 3-5 times greater than the information capacity of DVDs due to the use of a blue laser with a wavelength of 405 nanometers.

Optical disk drives are divided into three types:

• No recording option- CD-ROM and DVD-ROM
  (ROM - Read Only Memory, read-only memory).
  CD-ROM and DVD-ROM discs store information that was written to them during the manufacturing process. It is impossible to write new information to them.
• Write once and read many times -
  CD-R and DVD±R (R - recordable, recordable).
  On CD-R and DVD±R discs, information can be written, but only once. Data is written to the disk using a high-power laser beam, which destroys the organic dye of the recording layer and changes its reflective properties. By controlling the laser power, alternating dark and light spots are obtained on the recording layer, which, when read, are interpreted as logical 0 and 1.
• Rewriteable- CD-RW and DVD±RW
  (RW - Rewritable, rewritable). On CD-RW and DVD±RW discs, information can be written and erased many times.
  The recording layer is made of a special alloy, which can be heated into two different stable states of aggregation, which are characterized by different degrees of transparency. When recording (erasing), the laser beam heats a section of the track and transfers it to one of these states.
  When reading, the laser beam has less power and does not change the state of the recording layer, and alternating areas with different transparency are interpreted as logical 0 and 1.

Key characteristics of optical drives:

disk capacity (CD - up to 700 MB, DVD - up to 17 GB)

data transfer rate from the media to RAM- measured in fractions of speed
150 KB/sec for CD drives (the first CD drives had this speed of reading information) and
1.3 MB/sec for DVD drives (This was the reading speed of the first DVD drives)

Currently, 52-speed CD drives are widely used - up to 7.8 MB/sec.
CD-RW discs are written at a lower speed (for example, 32x).
Therefore, CD drives are marked with three numbers “read speed X CD-R write speed X CD-RW write speed” (for example, “52x52x32”).
DVD drives are also marked with three numbers (for example, "16x8x6"

access time - the time required to search for information on a disk, measured in milliseconds (for CD 80-400ms).

If the storage rules are observed (stored in cases in an upright position) and used (without causing scratches or contamination), optical media can retain information for decades.

Additional information about disk structure

The industrially produced disc consists of three layers. An information pattern is applied to the base of the disc, created from transparent plastic by stamping. For stamping, there is a special prototype matrix for the future disk, which extrudes tracks on the surface. Next, a reflective metal layer is sprayed onto the base, and then a protective layer of thin film or special varnish is applied on top. Various drawings and inscriptions are often applied to this layer. Information is read from the working side of the disk through a transparent base.

Recordable and rewritable CDs have an additional layer. For such discs, the base does not have an information pattern, but between the base and the reflective layer there is a recording layer, which can change under the influence of high temperature. When recording, the laser heats up specified areas of the recording layer, creating an information pattern.

A DVD disc may have two recording layers. If one of them is performed using standard technology, then the other is translucent, applied lower than the first and has a transparency of about 40%. To read double-layer discs, complex optical heads with variable focal length are used. The laser beam passing through translucent layer, first focuses on the inner information layer, and after finishing reading it, refocuses on the outer layer.

What can be a carrier of information? Something on which everything we need to remember can be preserved, for human memory is short-lived. Our ancestors left important data on the ground, on stone, on wood, and on clay until paper appeared. This turned out to be material that meets the most important requirements for a storage medium. It was light, durable, convenient for notes and compact.

It is these requirements that modern storage media – optical(these are CDs or laser discs). True, at the transition stage (from the beginning of the 20th century), between paper and disks, magnetic tape helped us a lot. But her time is over. Today, the most convenient and reliable container and storage of information are disks.

How to put information on disk? We have known the concept of “recording a cassette” for decades. Now we are also talking about disks. Only this process has become much simpler and cheaper.

Today we will talk about optical storage media: device, recording technology, main differences.

CD-Rs were the very first recordable optical media. They only had the ability to record once. The data was saved when the working layer was heated by a laser, causing its chemical reaction (at t? = 250? C). At this moment, dark spots form in the heating areas. This is where the concept of “burning” comes from. On DVD-R discs“burning” occurs in a similar way.

The situation is slightly different with CD, DVD and Blu-ray discs that have a rewriting function. Such dark dots do not form on their surface, because the working layer is not a dye, but a special alloy, which is heated by a laser to 600? C. Then, the areas of the disk surface exposed to the laser beam become darker and have reflective properties.

On this moment, in addition to CD discs, which can be considered pioneers in the range of optical media, discs such as DVD and Blu-ray appeared. These types of disks are different from each other. For example, capacity. A Blu-ray disc can hold up to 25GB of data, a DVD can hold up to 5GB, and a CD can only hold up to 700MB. The next difference is the way data is read and written in Blu-ray drives. A blue laser is responsible for this process, the wavelength of which is one and a half times less than that of a red CD laser or DVD drives. That is why on the surface of Blu-ray discs, which is equal in area to other types of discs, it is possible to record information many times larger.

formats laser discs

The three types of laser discs listed above can also be classified according to their formats:

1. CD-R discs, CD-RW - identical in size (up to 700; sometimes 800MB, but such discs are not readable by all devices). The only difference is that CD-R is a one-time recordable disc, and CD-RW is reusable.

2. Discs DVD-R format, DVD+R, as well as DVD-RW - they differ only in the ability to rewrite DVD-RW discs multiple times, but otherwise the parameters are the same. 4.7 GB is the capacity of a standard DVD disc and 1.4 GB is the capacity of a DVD with a diameter of 8 cm.

3. DVD-R DL, DVD+R DL – double-layer discs that can hold 8.5GB of information.

4. Formats BD-R - Blu-ray discs are single-layer, with a capacity of 25 GB and BD-R DL - Blu-ray discs are double-layer, with a capacity of 2 times more.

5. Formats BD-RE, BD-RE DL Blu-ray discs – rewritable, up to 1000 times.

Discs with “+” and “-” signs are a relic of format disputes. Initially, it was believed that “+” (for example, DVD+R) was the leader for the computer industry, and “-” (DVD-R) was the quality standard for consumer electronics. Nowadays, almost all equipment easily recognizes discs of both formats. None of them have any obvious advantages over each other. The materials for their production are also identical

what are optical discs

The disc itself, which is used at home to record information, is no different in size from industrially produced discs. The structure of all optical media is multilayer.

• The basis of each is a substrate. It is made of polycarbonate, a material resistant to various external influences environment. This material is transparent and colorless.
• Next comes the working layer. For recordable and rewritable discs, it differs in its composition. For the former, it is an organic dye, for the latter, it is a special alloy that changes the phase state.
• Then comes the reflective layer. It serves to reflect the laser beam and may contain aluminum, gold or silver.
• The fourth is a protective layer. Only CD and Blu-ray discs are covered with a protective layer, which is a hard varnish.
• The last layer is the label. This is the name given to the top layer of varnish that can quickly absorb moisture. It is thanks to this that all ink that falls on the surface of the disc during the printing process dries quickly.

process of transferring information to disk

Now a drop of scientific theory. All optical storage media have a spiral-shaped track running from the very center to the edge of the disk. It is along this path that the laser beam records information. The spots formed when “burning” with a laser beam are called “pits”. The areas of the surface that remain untouched are called "lands". In binary language, 0 is pit and 1 is land. When the disc starts playing, the laser reads all the information from it.

“Pits” and “lands” have different reflectivity, therefore, the drive easily distinguishes all dark and light areas of the disk. And this is the same sequence of ones and zeros inherent in all physical files. Gradually, it became possible to increase the accuracy of focusing thanks to the development of technologies that reduced the wavelength of the laser beam. Now, on the same disk area as before, you can place a much larger amount of information, because the distance between the laser and the working layer directly depends on the wavelength. Shorter wave - shorter distance.

ways to burn discs

Recording during the industrial production of discs is called stamping. In this way, discs with recordings of music, films, computer games. All the information that gets onto the disk during stamping consists of many tiny indentations. Something similar happened when gramophone records were made.

• Recording a disc at home occurs using a laser beam. It is also called “burning” or “cutting”.

organization of the recording process on optical storage media

Stage 1. Media type recognition. We loaded the disc and wait for the recorder to provide information about the appropriate recording speed and the most optimal laser beam power.

Stage 2. The program that controls the recording makes requests to the recorder about the type of media used, the amount of free space and the speed at which the disc should be burned.

Stage 3. We indicate all the necessary data requested by the program and compile a list of files that require writing to disk.

Stage 4. The program transfers all data to the recorder and monitors the entire burning process.

Stage 5 The recorder sets the power of the laser beam and starts the recording process.

Even for media of the same format, the recording quality can differ radically. In order for the recording quality to be high, you should pay attention to the speed specified in the recording. Exists " Golden Rule"—fewer errors at lower speeds and vice versa. The recorder itself, namely its model, also plays a significant role.

signature on optical discs

It is advisable to immediately sign a disk on which some information appears, in order to avoid confusion. This can be done in different ways:

• printing text on blanks, the surface of which is varnished and allows you to print texts and images using an MFP with a special tray.
• using a recorder, supported by special technologies that apply text and a single-color image to a special surface. The cost of such disks can be 2 times higher than the cost of simple disks;
• signature made independently by hand (with a special marker);
• LabelTag technology – text is applied directly to the disk working surface. The inscription may not always be legible;
• stickers printed separately on any of the printers. Their use is not encouraged, because... they can damage the surface of the disc and come off during playback.

storage duration of optical storage media

On the labels of new disks you can see a period indicating how long data can be stored on this medium. Sometimes this figure corresponds to 30 years. In reality, such a period is almost impossible. During its existence, the disk can be subject to various impacts and damage. If it was recorded at home, its shelf life is reduced even further. Only ideal storage conditions will allow you to keep all the data on the disks safe and sound.

CD(Compact Disc) is an optical storage medium in the form of a plastic disk with a hole in the center, the process of writing/reading information to/from which is carried out using a laser. CDs are becoming faster and cheaper. Information is recorded on a CD using an industrial method. The most widely used are 5-inch CDs with a capacity of 670 MB. Their characteristics are completely identical to regular music CDs. Data on the disk is written in the form of a spiral (unlike a hard drive, on which the data is arranged in the form of concentric circles). From a physics point of view, the laser beam determines the digital sequence of ones and zeros recorded on the CD, in the form of microscopic pits (pits) on its spiral. Today, with a computer with a CD burner, you can make a disc in less than an hour.

DVD(Digital Versatile Disk, formerly Digital Video Disk), i.e. multi-purpose digital disk- a type of CD that stores from 4.7 to 17 GB of information, which is quite enough for a full-length film. This volume can satisfy any manufacturer of computer games and encyclopedias, the production of which usually required several CD-ROMs, causing inconvenience for the user. The DVD-ROM specification considers disks and DVD technology as a means of storing computer data with enormous capacity. The DVD-Video specification, around which so many copies were broken, only provides for the recording of full-length film programs with high image quality, multi-channel sound and international settings. The DVD-Audio specification considers a standard for recording only audio, assuming, however, significantly higher quality, multi-channel and the ability to place more than 74 minutes on the same disc. music, but also a variety of related information. It becomes clear that the rapid decline in prices for DVD devices may lead to the displacement of CD drives in the near future, even if old media are used. There are four types of DVDs based on their data structure:

• DVD-video - contains films (video and sound);
• DVD-Audio - contains audio data High Quality(much higher than on audio CDs);
• DVD-Data - contain any data;
• mixed content.

BD(Blu-ray - English blue ray - blue ray and disc - disk) - an optical media format used for recording and storing digital data, including high-definition video with increased density. The Blu-ray standard was jointly developed by the BDA consortium. new technology There were dramatic changes in the logical structure of the disk, cost and other parameters. The wavelength of the blue laser was shortened to 405 nm, which made it possible to position the beam much more accurately, and therefore place data on the disk with greater density. The shorter wavelength of the blue-violet laser allows you to store more information on 12 cm discs of the same size as a CD/DVD. BD is a new generation product, the most progressive, meeting the “requirements of our time” than CDs and DVDs.

16. Personal computers. Device. Main characteristics.

Computer- This electronic device, designed to work with information, namely introduction, processing, storage, output and transmission of information. In addition, a PC is a single entity of two entities - hardware and software (which is reflected in the following diagram).

According to the definition of a computer, the components of a computer can be divided into devices that perform specific functions related to information.

A data carrier in the form of a plastic or aluminum disk, intended for recording and/or playback of sound (CD), images (video), alphanumeric information, etc. using a laser beam. Recording density St. 108… … Big Encyclopedic Dictionary

A disk containing digital data readable using optical technology. [GOST 25868 91] Equipment topics. periphery processing systems information EN optical disk...

OPTICAL DISK, in computing, a compact storage device consisting of a disk on which information is written and read using a laser. The most common type is CD ROM. Audio CDs also represent... ... Scientific and technical encyclopedic dictionary

A data carrier in the form of a plastic disk designed for recording and playing back sound (CD), images (video disc), alphanumeric information, multimedia (CD ROM, DVD), etc. using a laser beam. The first optical... ... Encyclopedia of technology

Data carrier in the form of a disk made of transparent material (glass, plastic, etc.) with metallization. layer, on which microscopy, recesses (pits) are formed using digital optical recording, collectively forming spiral or annular... ... Big Encyclopedic Polytechnic Dictionary

A storage medium intended for recording and/or reproducing information using focused laser radiation. It consists of a rigid (usually optically transparent) base, on which a photosensitive or reflective layer is applied and... ... encyclopedic Dictionary

147 optical disk: A disk containing digital data read using optical technology Source: GOST 25868 91: Peripheral equipment for information processing systems. Terms and Definitions … Dictionary-reference book of terms of normative and technical documentation

According to GOST 25868–91, “Peripheral equipment for information processing systems. Terms and Definitions” – a disk containing digital data read using optical technology... Records management and archiving in terms and definitions

A storage medium intended for recording and/or reproducing information using focused laser radiation. It consists of a rigid (usually optically transparent) base, on which a photosensitive or reflective layer is applied and... ... Natural science. encyclopedic Dictionary

Blu Ray Discs (BD) are a new generation of storage media for storing high-definition video (HDTV) and high-density data. The Blu Ray standard was jointly developed by a group of consumer electronics and computer companies... Technical Translator's Guide

Books

• , Kuzmenko Galina. IN textbook the content side of the manifestation of the psychological and pedagogical skill of a trainer in the development of social and emotional intelligence in a system of significant qualities is presented...

Information carriers – material that is intended for recording, storage and subsequent reproduction of information.

Storage medium - a strictly defined part of a specific information system, used for intermediate storage or transmission of information.

Storage medium is the physical environment in which it is recorded.

The media can be paper, photographic film, brain cells, punched cards, punched tapes, magnetic tapes and disks or computer memory cells. Modern technology offers more and more new types of storage media. They use the electrical, magnetic and optical properties of materials to encode information. Media are being developed in which information is recorded even at the level of individual molecules.

All computer media are divided into:

1. Perforated – have a paper basis, information is entered in the form of punches in the corresponding row and column. The volume of information is 800 bits or 100 KB.

2. Magnetic media – they are used as flexible magnetic disks and cassette magnetic tapes.

3. (compact discs) is a metallized plastic compact disc, 120 mm in diameter and 1.2 mm thick. On one of its sides there is a reflective aluminum layer, which is coated with a protective varnish to prevent damage. Information is recorded and read by a laser beam on a path running in a spiral from the center.

Optical storage media– (compact discs) is a metallized plastic disc with a diameter of 120 mm. And 1.2mm thick. On one of its sides there is a reflective aluminum layer, which is coated with a protective varnish to prevent damage. Information is recorded and read by a laser beam on a path running in a spiral from the center.

Types of optical disks:

1. CD-ROM (Compact Disk Read Only Memory) – a compact disc without the ability to record information.

2. CD-R (Compact Disk Recordable) – a CD with the ability to record information once.

3. CD-RW (Compact Disk Rewritable) – a CD with the ability to record information multiple times.

4. DVD (Digital Versatile Disk) – a digital multilayer disk for recording large amounts of information (up to 18 GB).

ADVANTAGES: Reliability. Ability to record large amounts of information. Wear-free.

Compact Disk (CD) is a disc with a diameter of 120 mm (4.75 inches) or 80 mm (3.1 inches) and a thickness of 1.2 mm. The depth of the stroke is 0.12 µm, the width is 0.6 µm. The strokes are arranged in a spiral, from the center to the periphery. The stroke length is 0.9–3.3 µm, the distance between the tracks is 1.6 µm. Compact discs are made up of three to six layers. A standard five-inch disc can contain 650–700 MB of information, 74–80 minutes of high-quality stereo sound with a sampling rate of 44.1 kHz and a digitization depth of 16 bits, or a huge amount of audio in MP3 format. Three-inch disks hold about 180 MB of information. Sometimes there are disks called “business cards”. By appearance and they resemble a business card in size, but are actually three-inch disks, cut on both sides. Such a CD can store from 10 to 80 MB.

In the late 1970s, Sony and Philips began jointly developing a single standard for optical storage media. Philips created the laser player, and Sony developed the technology for recording on optical media. At the suggestion of Sony Corporation, the disc size was 12 cm, because... this volume made it possible to record Beethoven’s Ninth Symphony in its entirety. In 1982, in a document called the Red Book, a standard for processing, recording and storing information on laser disks was published, as well as the physical parameters of the disk, i.e.: 1. Physical size of the disk. 2. Disk structure and data organization. 2. Recording data in a single stream from the center to the periphery. 3. Read data at a constant linear velocity (Constant Linear Velocity, CLV).

All data on the disk is divided into frames. Each frame consists of 192 bits for music, 388 bits for modulation and error correction data, and one control bit. 98 frames make up one sector. Sectors are combined into a track. A maximum of 99 tracks can be recorded on a disc.

During recording and reading of information, when the laser beam moves from the center to the periphery, the rotation speed of the disk is ↓. This is necessary to ensure that the same amount of information can be read and written in the same amount of time. Therefore, without the use of CLV technology, when playing, for example, musical works, the performance speed would change.

Due to relatively small size laser discs, compared to vinyl records, they were called compact discs, or abbreviated CD (Compact Disk). The first CDs were designed for recording and playing music and could store up to 74 minutes of high-quality stereo sound. The standard for such discs was called CD-DA (Compact Disk Digital Audio).

With the development of the computer industry, a need arose for technology that allows storing on CDs not only digital audio, but also various data. Computer programs could not fit on floppy disks, and the volumes user files became more and more.

In 1984, a standard called the Yellow Book was published. Sony and Philips companies reorganized the structure of CDs and began to use new error correction codes - EDC (Error Detection and Correction) and ECC (Error Correction Code). The main unit of data placement was the sector. One sector contains: 12 bytes for synchronization, 4 bytes for headers, 2048 bytes for user data and 288 bytes for error correction. CAV (Constant Angular Velocity) technology was developed to read computer data. CAV technology allows you to read information from a disk faster than CLV technology, since the data flow increases as the laser beam moves from the center to the periphery. Modern CD drives support both technologies. Computer laser disks were called CD-ROM - Compact Disk ReadOnly Memory (literally, “read-only memory on CDs”). In the late 1990s, the CD drive became a standard component of any computer and the vast majority of programs began to be distributed on CDs.

The consumer market was rapidly expanding, production volumes were increasing, and the largest manufacturers began developing technology that allows the user to independently record any information on a CD. In 1988, Tajio Yuden released the world's first CD-R (Compact Disk Recordable). The biggest challenge faced by CD recorder designers is finding highly reflective materials. Tajio Yuden successfully completed the task. The gold-cyanine alloy they used to make these drives had a reflectivity of over 70%. The same company developed a method for applying an active organic layer to the surface of a disk, as well as a technology for dividing the disk into tracks.

DVDs, DVD-R, DVD-RW, CD, CD-R, and CD-RW are manufactured by various companies: AMD, Amedia, Digitex, HP, Imation, MBI, Memorex, Philips, Smartbuy, Sony, TDK, Verbatim.

DVD structure.

In December 1995, 10 companies united in the DVD Consortium officially announced the creation of a single unified standard - DVD. The abbreviation DVD first stood for Digital Video Disc, but later its meaning was changed to Digital Versatile Disc. The disc was fully compatible with the Red Book and Yellow Book standards. DVD is identical in appearance to CD, but allows you to record information that is 24 times larger in volume, that is, up to 17 GB. This became possible thanks to changes in the physical characteristics of the disk and the use of new technologies. The distance between the tracks was reduced to 0.74 μm, and the geometric dimensions of the pits were reduced to 0.4 μm for a single-layer disk and 0.44 μm for a double-layer disk. The data area has increased, the physical sizes of sectors have decreased. A more efficient error correction code, RSPC (Reed Solomon Product Code), was used, and more efficient bit modulation became possible. DVD technology provides a huge number of formats and four types of designs in two sizes. A disc of this standard can be either single-sided or double-sided. There can be one or two working layers on each side.

Burning single-layer DVDs is similar to burning CDs, but burning dual-layer discs is significantly different from the process described earlier.

Double-layer discs of types DVD-2 and DVD-9 have two working layers for recording information. These layers are separated using a special translucent material. To perform its function, such a material must have mutually exclusive properties: reflect the laser beam well when reading the outer layer and at the same time be as transparent as possible when reading the inner layer. At the request of Philips and Sony corporations, 3M created a material that meets the following requirements: having a reflectivity of 40% and the necessary transparency. DVDs are 0.6mm thick. For physical compatibility with CDs, a 0.6 mm thick polycarbonate backing was additionally glued onto the DVD.

The CD specification does not provide any copy protection mechanism - discs can be freely copied and played. However, starting in 2002, various Western record companies began attempting to create copy-protected CDs. The essence of almost all methods comes down to deliberately introducing errors into the data written to the disk, so that on a household CD player or music center The disc played, but not on the computer. The result is a game of cat and mouse: such discs are not readable on all household players, but on some computers they are readable, it turns out software, allowing you to copy even protected discs, etc. The recording industry, however, does not give up hope and continues to test more and more new methods.

There are also magneto-optical disks : FLOPTICAL = FLOPPY (floppy disk) + OPTICAL.

The surface of the magneto-optical disk is covered with a special material, the properties of which change under the influence of temperature and magnetic fields. All these disks differ from each other in diameter and number of working surfaces. The volume of information is up to 10 GB.