Judging by the statistics, this topic is of interest to many readers and I will be happy to continue it.

Today, as I promised, we will talk about LCD technology, or rather 3LCD (I’ll tell you why below).

If we turn to the great and terrible Wiki, the history of the emergence of LCD projectors goes back to the 70-80s of the last century, when a certain American inventor Gene (Eugene) Dolgoff (judging by the name and surname of a Native American) began developing and bringing to life the design of LCD- a projector capable of competing with the then “God” of projectors - a device based on a CRT (cathode ray tube).

Accordingly, the first LCD projectors contained a single LCD matrix, similar to those used in televisions. The advantage of this scheme was its simplicity. But in fact, a drawback immediately emerged - with an increase in the power of the light source, which was necessary to increase the luminous flux, and as a result of the image brightness, the LCD panel began to overheat. The result of “working on the mistakes” was the appearance in 1988 of a technology called 3LCD, and in 1989, 3 companies Epson, InFocus and Sharp released the first projectors based on it.

What did the engineers come up with, and where did the name 3LCD come from?

How a 3LCD projector works. To form an image, a 3LCD projector is equipped with a system of lenses, dichroic mirrors and three LCD matrices. It all works like this. Light from the source (in the case of an LCD projector, this is always a lamp, since the only prototype of an LCD LED projector presented by Epson was never released to the masses) falls on the so-called dichroic mirrors installed in the optical unit. These mirrors (filters) transmit light of one of the colors (light in a certain spectrum) and reflect the rest of the light. Passing through a system of mirrors, the light is divided into 3 main components R, G, B (red, green and blue), each of the colors falls on the LCD matrix intended for it.

The matrices themselves installed in the LCD projector are monochrome (i.e., they form a black and white image). They work in the same way as in LCD TV, i.e., unlike a DLP chip, they do not reflect, but transmit light, and when high magnification, figuratively, represent a lattice, where the rods carry control channels, and the voids between the rods are pixels - image points.

These same pixels can close and open, thereby transmitting or not transmitting light (or partially transmitting it). When light of one of the colors hits the matrix, the LCD panel forms an image of that color and sends it to the prism, where the images of the three colors are combined into a full-color image, which is then sent through the lens to the screen. Hence the name 3LCD. I hope the description is clear, but if not, watch the video that clearly describes my tirade.

This scheme, as usual, has its advantages and disadvantages.

Due to the fact that the image is formed inside the projector and appears on the screen already “blended”, and not displayed in colors, it is believed that the image from LCD projectors is less straining on the eyes. There were even studies conducted in Japan on this topic, and they seemed to prove this fact, but I don’t have any evidence of this, nor any evidence to the contrary. But the fact remains that in LCD and LCOS projectors the image is projected onto the screen in full color; in single-matrix DLP projectors it is a sequence of color images put together in the brain.

One of the advantages that follows from the paragraph above is the absence of the “rainbow effect”, which I talked about in the post about DLP projectors. It cannot exist here as such.

The next positive point in the three-matrix system is the constancy and high brightness of the color image. I have already told you that when it comes to office DLP projectors, manufacturers use the white segment in the color wheel to increase brightness, which spoils color rendition. In the case of an LCD projector, light is also absorbed by the system components, but in the end, in terms of efficiency when outputting a color image, LCD projectors are more profitable, and the quality of their color rendering does not depend on the brightness of the projector.

The disadvantages of LCD projectors are called lack of convergence, low level black and low contrast, the so-called Screen door effect and “matrix burn-in”.

Ignorance. In fact, this deficiency occurs quite rarely. It consists of the appearance of colored outlines of objects in the image. The fact is that, as you already know, the projector uses three matrices, each of which is responsible for its own color. If these matrices are not installed accurately enough in relation to each other, then a picture of one color will “shift” slightly in relation to images of other colors, then, for example, you can see a blue outline to the right of the object, and a red outline to the left. Fortunately, manufacturers of LCD projectors very precisely adjust the position of the panels, despite their tiny size (imagine the size of the pixels in them!), so this misalignment usually does not exceed half a pixel (such an outline can only be seen when you come close to the screen, and this is absolutely does not affect the image in any way). But of course there are cases when the lack of convergence can be 2, 3, or more pixels. In this case, the user has a direct route to the service or to the seller.

Contrast and black level. DLP projectors, which appeared in 1996, made a splash in terms of black color and contrast, and from the first days, fans of this technology and manufacturers of DLP projectors actively promoted this advantage over the “oldies” represented by LCD devices. Indeed, you could see the difference in black between DLP and LCD projectors with the naked eye. Where Malevich’s “Black Square” looked really close to black on a DLP projector, LCD projectors produced outright grayness. Manufacturers of LCD matrices began modifying their panels, and today, about ten generations of these devices have changed (DMD chips have replaced 4 generations). And one of the things that improved from generation to generation was black level and contrast. Today we can state that in home theater projectors, the best representatives of the LCD camp are not inferior to, and sometimes even superior to, their “DLP friends” in terms of contrast and black level. In the office sector and in education, the gap in numbers and viewing in the dark remains, but firstly, it is no longer so noticeable, and secondly, black color and contrast during presentations in ambient light conditions are not so important, because black on white In principle, there is no screen in the light and cannot be.

Screen door effect. This favorite item of ardent “DLPers” made me happy even at a time when monitors were square, and one could only dream of a 720p projector. Screen door effect is the so-called “grid effect”. The thing is that the distance between the pixels of the DMD chip, LCD chip and LCOS chip is different. This is related to chip control: in LCOS and DMD, the operation of individual pixels is controlled “from behind” the chip, while with “transmission” LCD technology this is not possible, and to control the cells of the chip it is necessary to lay control channels between them. Thus, the distance between the pixels in the LCOS panel is minimal, and the usable area of ​​the chip is maximum. In LCD, on the contrary, the minimum of the three technologies is the useful area of ​​the chip and the maximum distance between the image points. DLP is in between.

Despite the fact that projector resolutions are increasing, some DLP projector manufacturers continue to insist that when viewing an image from an LCD projector, a grid can be seen on the screen. If you sit close to the screen, I agree with this. But if you look at the image from an adequate distance... With SVGA resolution on a screen 2 meters wide, we have a pixel measuring 2.5 mm, and the distance between them is slightly less than a millimeter, and if desired, and at a distance of up to 3 meters from the screen, the grating can be seen . With XGA resolution, the pixel size becomes less than 2 mm, with WXGA - 1.5 mm, with FullHD - 1 mm. What pixels and grids are we talking about? Of course, you can see the pixels on Retina iPhone display...With a magnifying glass! But the viewer looks not at the pixels, but at the picture, and here, with normal content quality, you don’t notice any pixels.

"Burnout of matrices." Have you ever seen a yellow image on a projector? No, not in the sense of the yellow lemon in the picture, but the whole image, which smacks of yellow! There could be three reasons for such an incident.

Cigarette smoke. Often in bars there are projectors hanging. If smoking is allowed in the room where the projector hangs, after some time after installation the projector begins to turn yellow.

It's all about cigarette smoke and the tars it contains. As they settle on the optical components of the projector, they turn into a yellow coating, which makes the image yellow and reduces brightness. And no matter what technology is used (some manufacturers of DLP projectors claim that they have a sealed optical unit, so this problem does not concern them; resin settles everywhere, including on the lens) - sooner or later the image will fade and turn yellow. But cleaning the optics from this muck is still a problem, so in a bar it is better to isolate the projector from smokers as much as possible.

Incorrect setting. Everything here is trivial - for example, it’s set too low Colorful temperature and voila, the image is too warm.

And finally, “matrix burnout” in an LCD projector. Specifically, the degradation of the polarizer of the LCD panel, which is responsible for the formation of the blue component of the image, as a result of which the image does not receive enough blue color and, as a result, yellowness appears.

At one time, TI (Texas Instruments), a manufacturer of DMD chips and the main opponent of LCD manufacturers in the market, conducted a study that showed that degradation occurs after 3000 hours. It’s just that the conditions under which these studies were carried out seem very controversial. They took the most compact ones, which means they were intended for traveling mobile presentations, projectors and launched them around the clock. Manufacturers of such equipment never claim that it is designed for round-the-clock operation, and mobile projectors in general are usually used no more than 3-4 hours a day.

Under normal operating conditions, degradation occurs much later - this time. 3000 hours is 3 years of daily (on weekdays) four-hour presentations is two. Since the experiment was carried out, and it was carried out, if my memory serves me correctly, in 2004-2005, a lot of water has passed under the bridge and 5 generations of LCD panels have changed - that’s three. Today, I would no longer pay attention to such statements.

For reference: at home, I’ve been using an LCD projector for 5 years now - it’s not like yellowness has appeared, I haven’t even changed the lamp yet (this is about the fear of users that the lamp needs to be changed often)!

And finally, let's get back to the good stuff. Another significant advantage of LCD projectors is lens shift. Of course, a lens shift system can be installed in virtually any projector (regular sizes), but only in “entry” level LCD projectors it is present, while in DLP and LCOS mills, these will be devices in a different price range. Why did I use quotation marks? Because today the most affordable FullHD projector with lens shift costs about 50 thousand rubles.

I have already spoken about “Lens Shift” more than once, including in the previous article in the series about DLP projectors, but let me remind you once again what it is. If the projector has a lens shift (Lens Shift) or, as it is also called “Lens Shift,” this means that the projector has a lens system that allows you to move the image without moving the projector itself. The shift can be vertical and horizontal. Vertical lens shift has a larger range than horizontal one and is much more common (until recently, it was only found in mid-level DLP projectors, and horizontal was added to models top level). What is its function? To simplify the installation of the projector. Imagine a situation where it is not possible to install the projector in the center of the screen, but there is a lens shift. In this case, the projector is installed, for example, to the left of the screen, and the picture is shifted to the right by a wheel, lever or button on the case or remote control (depending on the projector model). Accordingly, lens shift can be manual (wheel) or motorized (button). Unlike simply rotating or tilting the projector, lens shifting does not create keystone distortion, requiring electronic correction to distort the original image. An example of how manual lens shift works is shown in the video.

The thing is super convenient!

Well, that seems to be all I wanted to tell you about 3LCD projectors. If you forgot something, comments are welcome.

The next article in this series will focus on LCOS. Don't switch

All projectors, as well as screens, lamps, mounts and other accessories are in mine.

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SXRD is a new imaging technology in projection devices from Sony

Sony Corporation announced the development of the SXRD (Silicon X-tal1) Reflective Display device. It is a liquid crystal panel designed for use in multimedia projectors, which provides a contrast ratio of more than 3000:1 with high image clarity corresponding to the full HDTV standard (1920 H x 1080 V).

The excellent image quality produced by the SXRD panel is achieved due to the large number of pixels within the image area. Size of each individual element images and inter-element gap were brought to the minimum possible values. Combination of completely new Silicon Driving Circuit technology and new Silicon Wafer Process Technology ( technological process on a silicon lattice), combined with another new technology Liquid Crystal Device (liquid crystal device) made it possible to increase the number of image elements to 2,000,000, placed with a pitch of 9 microns and a gap of only 0.35 microns. Compared to high-temperature liquid crystals of polycrystalline silicon, the gain in element density was 2.4 times, and the inter-element gap was reduced by 10 times. Based on these advances, very high quality images were obtained, with clarity that was previously simply unattainable in projection devices with a fixed number of elements. The result is excellent cinematic quality and very good image uniformity, which completely eliminates the "grid grain" effect hitherto seen in LCD projectors.

Also, in the Sony SXRD device, instead of using twisted nematic liquid crystals, Sony used materials called Vertically Aligned Liquid Crystal. These new technical solutions truly deliver fast response times of just 5 milliseconds and extremely high panel contrast levels of up to 3000:1 - approximately three times higher than traditional LCD projectors.

Silicon X-tal Reflective Display ) companies

D-ILA® is an officially registered trademark of JVC, which means that this product uses an original design based on a display made using LCoS technology, a mesh polarizing filter and a mercury lamp. D-ILA implies a three-chip LCoS solution. You can also often find the abbreviation HD-ILA - D-ILA technology with Full HD resolution.

SXRD™ is a registered trademark of Sony for products made using LCoS technology

Principle of technology

The operating principle of a modern LCoS projector is close to 3LCD, but unlike the latter, it does not use transmissive LCD matrices, but reflective ones (this LCoS is related to DLP technology).

General diagram of a three-chip LCoS-based projector.

On the semiconductor substrate of the LCoS crystal there is a reflective layer, on top of which there is a liquid crystal matrix and a polarizer. When exposed to electrical signals, the liquid crystals either close the reflective surface or open, allowing light from an external directional source to be reflected from the mirror substrate of the crystal.

Like LCD projectors, LCoS projectors today use only three-chip circuits based on monochrome LCoS matrices. Just like in 3LCD technology, three LCoS crystals, a prism, dichroic mirrors and red, blue and green filters are used to form a color image.

In the late 90s, at the dawn of technology, JVC offered single-chip solutions based on LCoS color matrices. In them, the light flux was divided into RGB components directly in the matrix itself using an HCF filter. Hologram Color Filter - holographic color filter ). This technology is called SD-ILA(English) single D-ILA). Philips also developed single-matrix solutions.

But single-chip LCoS projectors have not become widespread due to a number of disadvantages: threefold loss of luminous flux when passing through the filter, which also imposed limitations due to matrix overheating, low color rendering quality, and a more complex production technology for color LCoS chips.

Story

background of the technology

The background to the emergence of LCoS technology begins in the 60-70s of the 20th century. And, like many other technologies, including DLP, it originated from military orders.

In 1972, the LCLV (eng. Liquid Cristal Light Valve - liquid crystal optical modulator ). For the first time, LCLV technology was used to display information on big screens V command centers US Navy Department. Back then, these devices could only display static information.

The development of technology continued and the term English. Liquid Crystal Light Valve was replaced by English. Image Light Amplifier (ILA) as more suitable.

ILA differs from D-ILA in that the liquid crystals are controlled by a photoresist that is exposed to a modulating beam generated by a cathode ray tube.

In the early 90s, Hudges and JVC decided to join forces to work on ILA technology. September 1, 1992 became official date formation of the Hughes-JVC Technology Corp. joint venture.

The first commercial projector based on ILA technology was demonstrated by JVC in 1993. Over 3,000 of these projectors were sold during the 1990s.

The use of a cathode ray tube as an image modulator in ILA devices imposed restrictions on the resolution, size and cost of the device and required complex alignment of optical paths. Therefore, JVC continues to research to create a fundamentally new reflective matrix that would solve these problems while maintaining the advantages of the technology. And in 1998, the company demonstrates the first projector made using D-ILA technology, in which the image-modulating device in the form of a “CRT beam - photoresist” bundle is replaced with CMOS control elements implemented in the semiconductor structure of the substrate - hence the name of the “direct drive ILA” technology. - ILA with direct control. Sometimes D-ILA is deciphered as “digital ILA”, this is not entirely correct, but it also correctly reflects the essence of the changes in D-ILA technology from analog device-controlled (CRT) ILA.

There was also an intermediate, also digital, technology between ILA and D-ILA, which was not widespread - FO-ILA, - where is the control cathode-ray tube was replaced by a bundle of fiber-optic light guides (Fiber Optic), which transmitted a modulating signal from the surface of a monochrome monitor.

first wave

second wave and disappointments

Philips

Despite multi-million dollar plans, Philips is winding down LCoS production by the end of 2004.

Intel

In January 2004, at CES, Full HD captured its significant share, making LCoS technology mainstream. However, by the end of 2004, Intel announced the winding down of this project.

The main reason for this was most likely not technological problems (although LCoS chips are much more complex in production than CMOS chips - processors), but the lack of market prospects - by this time it had already become clear that the FullHD TV market would be captured by more technologically advanced and cheaper LCD TVs. And the market for projection TVs and projectors themselves is too small to justify the investment.

Intel spent 5 years and $50 million on LCoS technology. investment

Sony

Sony demonstrated the first SXRD projector (based on a proprietary chip) in June 2003. In the next year Sony announced a projection TV based on SXRD technology. By 2008, the company stopped producing all projection TVs, including models based on SXRD technology.

But the company did not abandon the production of projectors. Today Sony produces installation projectors with a resolution of 4096x2160 (based on the 4K-SXRD chip) and an aperture of up to 11,000 ANSI lumens

Advantages and disadvantages of technology

Benefits Defined technological capabilities LCoS compared to competing 3LCD and DLP technologies:

• Greater coefficient of useful filling of the working space of the matrix. Since in LCoS the control elements are placed behind the reflective layer, they do not interfere with the passage of light, unlike translucent LCD matrices, which reduces the “mesh” of the image and minimizes the “comb effect”. The distance between matrix elements is only a few tens of micrometers and the fill factor (the ratio of the total working area of ​​pixels to the total area of ​​the matrix) for LCoS exceeds this figure for both LCD and DLP projectors.

• LCoS chips are more resistant to powerful radiation than DLP and LCD matrices. This makes it possible to make the most powerful installation projectors using LCoS technology.

• LCoS is ahead of LCD and DLP in terms of maximum available resolution.

• Deeper blacks and higher contrast than 3LCD projectors.

• The response time of LCoS matrix liquid crystals is less than the crystals used in translucent matrices in 3LCD technology.

• LCoS inherits the advantages of 3LCD technology over single-chip DLP projectors - no flicker and no “rainbow effect”.

LCoS based projectors

Despite the players' disappointments mass market, LCoS technology continues to attract interest from manufacturers and consumers.

Projectors based on it are positioned in the highest quality segment and in the professional field of application - ultra-high resolution projectors for cinemas.

Today, projectors using LCoS technology (D-ILA, SXRD) are produced by Canon, LG, Barco, CrystalView, DreamVision.

Simply put, a projector is a box that contains a lamp and a lens. But a lamp + lens is more of a spotlight than a projector - there needs to be something in the path of the light that forms the image. Once upon a time this was a film:

Think of overhead projectors: the user manually inserts film between the lamp and the lens, and we essentially have the same image-forming principle as today:

• the black section of the film tries to block the light,
• white areas of the film are transparent and transmit light,
• translucent areas can be colored, coloring the image on the screen.

This technology has the same image shortcomings that still worry us to one degree or another when choosing a projector.

1. The film tries to block black, but it doesn't do it well - there's a problem with contrast and black level.
2. Brightness limited lamp and the ability of the entire system, including the film, to withstand heat. The image is dim.
3. The image has undesirable shade due to the characteristics of the film and lamp, its “color temperature”.
4. If the filmstrip is in color, then the colors are unsaturated and it is not always clear how exactly they should look according to the author’s idea - the limitations of the film.

The main difference between a modern multimedia projector is that instead of a film, a certain matrix is ​​used, which is constantly updated, drawing new picture at least 60 times per second.

How is a color image formed?

However, the matrix has nothing to do with color formation. The matrix produces a monochrome image. If you shine white through it, it will be black and white, if you shine red through it, it will be black and red.

Since any sRGB color can be obtained by mixing red, green and blue, any color image can be obtained by superimposing black-red, black-green and black-blue on top of each other.

Below is the famous color photograph restored by the Americans from three black and white cards of Prokudin-Gorsky (taken before 1917):

They say that the black and white cards correspond to the red, green and blue components of the image. Americans need to trust-but-verify - I check in Photoshop, substituting one card on the red channel, another on the green, and a third on the blue:

They say the truth. So, if the white color is transparent, and we shine a flashlight of the correct color through each photo, then, by combining the three images on the screen, we will get our color photo.

All projectors use this principle: a matrix of streams of light in red, green and blue colors creates three images that overlap each other and give us a color image on the screen.

Sometimes more than three are combined, but three is enough.

Three-matrix and single-matrix projectors

Perhaps this is the main difference in projector technology. There are two ways to superimpose the mentioned red, green, blue images on top of each other: simultaneous overlay and sequential overlay

Simultaneous overlay is carried out in three-matrix projectors: red, green and blue streams pass through separate matrices, and then are combined, and the finished color image goes on the screen.

Three-matrix approach using the example of 3LCD technology

Using 3LCD technology as an example, it looks like this:

1. White light came out of the lamp.
2. Came to the filter, divided into red and blue.
3. Red passed through matrix No. 1, resulting in a red image.
4. The blue is divided into green and blue.
5. Green went to matrix No. 2, blue - to matrix No. 3.
6. We have three images that are superimposed on each other - we get one color one.
7. The color image disappeared onto the screen.

When applying “one by one”, the projector only needs one matrix - first red is supplied to it, then green, then blue, and the projector draws on the screen first red, then green, then blue image.

Single-matrix approach using the example of “1-DLP” technology
Please note: DLP matrix... mirror (more on this later)

This happens very quickly and, just as we do not see the individual spokes of a rotating bicycle wheel, we do not see individual color images on the screen, but see the result of their combination - a finished color image, although formed not in a projector, but “in the viewer’s head.”

In both cases we get a color image. Now regarding the pros and cons of the single-matrix and three-matrix approaches.

1. Price. Three matrices are more expensive than 1 matrix. 1 matrix is ​​cheaper than 3.
2. Efficiency. A three-matrix projector works with red, green and blue at any given time, while a single-matrix projector only works with one color(the rest is thrown away). A three-matrix projector has a noticeably higher efficiency in using lamp light.
3. Reduction of matrices. When there are three matrices, it is difficult to perfectly match each other, but single-matrix projectors do not have this problem - if the optics do not fail, then every pixel on the screen will be sharp, clearly defined.
4. Undesirable visual effects(artifacts). No matter how often the color images on the screen of a single-matrix projector change, conditions will arise when the eye recognizes and highlights these individual colors. This happens especially often in dynamic, contrasting dark scenes, when the gaze runs across the screen. There are many such situations, for example, in The Dark Knight. The eye twitched - a colored trail was visible for a split second behind the bright object. It is called " rainbow effect" or "color separation effect".

Please note that formally all this has nothing to do with LCD or DLP technologies. However, it just so happened that the most widespread, most budget part of the projectors is presented single matrix DLP And three-matrix LCD(3LCD) projectors that inherit all the pros/cons of the single-matrix and three-matrix approaches.

Separately, it is worth touching on the issue about efficiency, since it is not immediately clear what follows from the greater efficiency of using lamp light. Let's say you take a 190 W lamp and put it in a budget projector. A more efficient projector will be able to make the most of that 190W more brightness, or the same brightness with less lamp load, extending its resource. The advantage here is on the side of three-matrix technology, so single-matrix projectors have a tradition of having a bright image mode, in which the maximum brightness corresponds to a similar three-matrix projector, but only on white, and the colors are much duller than they should be. Most often this is done as follows: instead of creating a color image from red, green, blue, white (transparent) is also added:

The images show the color wheel of a single-matrix projector with a transparent segment

In other words, one of the components of the image is black and white, obtained not by mixing colors, but “dumbly” by transmitting lamp light onto the screen bypassing filters. However, these methods are used where the combination of cost and high brightness is important. For example, for office projectors this is suitable for displaying documents, but a home theater projector does not need high brightness - such projectors use an RGBRGB (six-segment) color wheel:

By repeating the full cycle of colors twice per turn, the visibility of the “rainbow effect” is also reduced.

LCD and DLP

If we consider the matrices directly, the LCD (LCD) matrix is ​​most reminiscent of the above-mentioned overhead projector film, since it works " into the light", getting in the way of the light flow. The task of each pixel is to block the light or let it pass further.

The DLP matrix does not work for transmission, but according to the reflective principle. Each of its pixels is a microscopic mirror, which, when rotated, reflects light onto the screen, or, in a deflected position, throws it onto the light absorber.

Overall, the mirrors do an excellent job cutting off unnecessary light, therefore a DLP matrix (“DMD” chip) can give noticeably greater contrast than an LCD matrix (other things being equal). Of course, contrast depends not only on the matrix, but as it becomes more expensive, it is possible to achieve higher contrast levels (take LCD projectors such as the EH-TW9200/9300 - huge contrast!). However, the bottom line is that we are talking about the advantage of DLP projectors in terms of contrast and black level.

Light path in a DLP projector: lamp-color wheel-mirror-matrix-...

LCD technology is found almost exclusively in a three-matrix configuration (Epson 3LCD), the vast majority of DLP projectors are single-matrix, and in expensive segments (some installation projectors, luxury home and cinema projectors) three-matrix DLP technology is present.

"Mosquito net effect"

Supposedly, another advantage of DLP technology is less interpixel space.

The fact is that an LCD matrix operating in transmission mode requires drawing contours to each pixel, and these contours can only pass between pixels - this results in some unused space between them. The advantage of DLP matrices is that the mentioned contours go under the mirrors, although the very need to change the position of the mirrors also creates a certain inter-pixel gap. As a result, 3LCD projectors tend to have slightly more noticeable inter-pixel spacing than DLP projectors.

LCoS, incl. D-ILA, SXRD, 3LCD Reflective

True, the latter deny that they are LCoS...

As we move into more expensive projector segments, LCoS (liquid-on-silicon) technology is emerging. Many manufacturers call it by their own name. Sony - “SXRD”, JVC - “D-ILA”, Epson - “Reflective 3LCD”, or “Reflective 3LCD”. Well, the latter captures the essence quite accurately.

This technology is an attempt to combine the advantages of LCD and DLP technologies. Liquid crystal matrices located on the mirror surface transmit light twice through themselves, better cutting off black (high contrast), while they do not have moving elements, and the control circuits are located under the mirrors, which allows for smaller interpixel space than both LCD and DLP .

The mentioned technologies are found only in a three-matrix configuration. The color formation scheme is similar to 3LCD, with the only difference being that LCoS matrices reflect light rather than transmit it through themselves:

Light source: lamps and lampless projectors

Comparing a modern digital projector with an overhead projector, we talked about the matrices that replaced film, and now it’s time to talk about the lamp.

Classic light source - mercury lamps. Depending on the type of lamp and load level, the resource of such a lamp ranges from 3000 to 5000 hours at maximum brightness. How is a resource counted? As far as I know, until the calculated moment the lamp brightness drops by 50%. This is the first drawback of lamps - a gradual decrease in brightness.

Lasers and LEDs are another matter! Resource - 20,000 or even 30,000 hours! The brightness also gradually decreases, but more linearly and over the same period.

And there are also xenon lamps - they have a shorter lifespan than mercury lamps, but they have their advantages.

Spectral radiation of xenon and mercury lamps

As a result, a significant disadvantage of mercury lamps is that the light they emit contains too much green. This means that the excess green color, which carries a significant portion of the light energy, must be cut off and discarded so that the green, red and blue are in the correct proportions and when mixed produce the correct white color (neutral, without tints). However, there is an agreement that brightest mode projector, noticeable loss in color rendering is acceptable. Thus, in the brightest picture mode, the picture takes on a slightly greenish tint.

For example, according to my observations, the most pronounced greenish tint in the brightest mode- DLP projectors with an RGBRGB color wheel, followed by 3LCD projectors, then DLP projectors with a transparent segment - somehow they manage to achieve a fairly neutral white. But the problem here is that when switching from the brightest mode to the most accurate, we in any case improve color rendition and cut off excess green using matrices projector, and then suddenly it turns out that by removing the excess green, we got a significant drop in brightness, but the black color did not change, it is the same for the bright and precise modes! The brightness decreased, but black remained, which means the contrast decreased as much as the brightness decreased - up to two times! So it goes. Switched to the precise mode designed for darkness and lost contrast... just great!

In this sense, xenon lamps have more even characteristics, although they are used very rarely and on expensive projectors.

Another strange problem with mercury lamps - for some reason they prevent most projectors from displaying 100% correct sRGB green color- Necessarily A little turns yellow.

Well, it is obvious that the lamps heat up and require powerful active cooling, which not only increases the size of the projector, but also increases its noise. Also, the lamps take some time to reach full power and, depending on the projector, it may take some time before turning off the power - the lamp needs to cool down.

With light emitting diodes (LEDs) the situation is different: LEDs can be extremely compact and allow you to create extremely miniature projectors, but ironically they have a problem with the brightness of the green LED, so the brightness of an LED projector is usually quite limited. A significant advantage of LEDs is the ability to have a very narrow emission spectrum, that is, a very rich, pure color. In this regard, from RGB (red, green, blue) LEDs it is possible to achieve a wider color gamut than the sRGB standard (used in Blu-ray, HDTV, for the Internet, etc.).

Yes, LEDs and lasers are not lamps that the user can easily pick up and replace. These light sources are highly integrated into the design of the projector, into its “optical engine”. Let's see why. There are many ways to use LEDs and lasers. So,

Semiconductor sources lights in the projector and their options:

1. White LEDs. This is similar to a lamp - we have white LEDs, their glow is divided into red, green and blue, like lamps... This is rare in practice.

2. RGB LEDs. We initially have three colored light sources - no need to separate anything - compactness! In addition, you can achieve high color saturation. Often used in miniature projectors in combination with single-array DLP technology.

Illustration of the operation of an RGB LED projector from NEC

3. Blue laser + yellow phosphor. Popular with expensive home laser projectors (JVC, Epson, Sony?). A blue laser gives a blue color, a second blue beam activates a yellow phosphor, and this yellow then divided into red and green. Below is an example of use with LCoS technologies:

Epson LS10000 schematic

The scheme is approximately the same for JVC

And here is an example of use with single-matrix DLP technology (BenQ):

4. LED laser projectors(“hybrid projectors”). Casio is actively used. So we want RGB LED projector, but you need to replace the dim green LED with something. Instead of a green LED, we install a blue laser (a green laser is expensive), which activates a green phosphor. We get a brightness close to lamp projectors (and, by the way, a similar green tint in bright mode).

Hybrid projector diagram from the Casio website.
The phosphor wheel must rotate to allow blue to pass through,
or produce green!

5. RGB laser projector. All on top level: excellent colors, high brightness, high price, large size.

Illustration of the NEC RGB laser projector design
It is noted that the pipes are made of fiber optics

Among the qualities of laser projectors used in practice are flexible and smooth control of the light source with the possibility of complete blackout in dark movie scenes, or limiting the brightness of the projector, leading to an increase in laser life. If the projector uses an array of lasers, then even after their service life has expired, the lasers will fail one by one, and not all at once, which in the worst case will lead to a gradual decrease in brightness.

However, when talking about laser and LED projectors, we have to admit that 20,000 and 30,000 hours are numbers related to the light source itself, and the design may contain other elements that may have a completely different resource. As a result, it is useful to look at the official manufacturer's warranty period...

As for phosphors, they obviously have their own characteristics when it comes to color rendering. As a rule, in practice, the color saturation of a phosphor is much less than what can be achieved from a laser/LED.

Is it possible to get a wide color gamut from a lamp projector?

I guess, yes. To get a wider color gamut You need to use color filters to cut off unnecessary parts of the spectrum. Actually, if we can isolate red from white, then why not isolate a purer red? True, light losses will increase, but who counts them when it comes to expensive projectors?

It is the third most common after DLP and 3LCD (LCD) technologies, but occupies a significantly smaller market share.

Synonyms for LCoS are the abbreviations D-ILA (English. Direct Drive Image Light Amplifier) by JVC and SXRD (eng. Silicon X-tal Reflective Display) by Sony. D-ILA is an officially registered trademark of JVC, which means that this product uses an original design based on an LCoS display technology, a mesh polarizing filter and a mercury lamp. D-ILA implies a three-chip LCoS solution. You can also often see the abbreviation HD-ILA. SXRD is a registered trademark of Sony for products made using LCoS technology.

Principle of technology

The operating principle of a modern LCoS projector is close to 3LCD, but unlike the latter, it uses reflective rather than transmissive LCD matrices. Just like DLP technologies, LCoS uses epi-projection instead of the traditional overhead projection found in LCD.

On the semiconductor substrate of the LCoS crystal there is a reflective layer, on top of which there is a liquid crystal matrix and a polarizer. When exposed to electrical signals, the liquid crystals either close the reflective surface or open, allowing light from an external directional source to be reflected from the mirror substrate of the crystal.

Like LCD projectors, LCoS projectors today mainly use three-chip circuits based on monochrome LCoS matrices. Just like in 3LCD technology, three LCoS crystals, a prism, dichroic mirrors and red, blue and green filters are usually used to form a color image.

However, there are single-chip solutions in which a color image is obtained using three powerful color quickly switchable LEDs, sequentially producing red, green and blue light, such solutions are produced by Philips. The power of their light is low.

In the late 1990s, JVC offered single-chip solutions based on LCoS color matrices. In them, the light flux was divided into RGB components directly in the matrix itself using an HCF filter. Hologram Color Filter - holographic color filter). This technology is called SD-ILA (eng. single D-ILA). Philips also developed single-matrix solutions.

But single-chip LCoS projectors have not become widespread due to a number of disadvantages: threefold loss of light flux when passing through the filter, which also imposed limitations due to matrix overheating, low color rendering quality, and a more complex production technology for color LCoS chips.

Story

Background to the emergence of technology

In 1972, the LCLV (Liquid Crystal Light Valve - liquid crystal optical modulator) was invented at the Hughes Research Labs of the Howard Hughes Hughes Aircraft Company, which at that time was the center of the most advanced research in the field of optics and electronics. LCLV technology was first used to display information on large screens in US Navy command centers. Back then, these devices could only display static information.

Technology development continued and the term LCLV was replaced by English. Image Light Amplifier (ILA) as more suitable.

ILA differs from D-ILA in that the liquid crystals are controlled by a photoresist, which is exposed to a modulating beam generated by a cathode ray tube.

In the early 1990s, Hughes and JVC decided to join forces to develop ILA technology. September 1, 1992 became the official date of formation of the Hughes-JVC Technology Corp. joint venture. The first commercial projector based on ILA technology was demonstrated by JVC in 1993. Over 3,000 of these projectors were sold during the 1990s.

The use of a cathode ray tube as an image modulator in ILA devices imposed restrictions on the resolution, size and cost of the device and required complex alignment of optical paths. Therefore, JVC continues research to create a fundamentally new reflective matrix that would solve these problems while maintaining the advantages of the technology. In 1998, the company demonstrated the first projector made using D-ILA technology, in which the image-modulating device in the form of a “CRT beam - photoresist” bundle was replaced with CMOS control elements implemented in the semiconductor structure of the substrate - hence the name “direct drive ILA” technology » - ILA with direct control. Sometimes D-ILA is deciphered as “digital ILA”, this is not entirely correct, but it also correctly reflects the essence of the changes in D-ILA technology from analog device-controlled (CRT) ILA.

There was also an intermediate, also digital, technology between ILA and D-ILA, which was not widespread - FO-ILA - where the control cathode ray tube was replaced by a bundle of fiber-optic light guides (Fiber Optic), which transmitted a modulating signal from the surface of the monochrome monitor.

First wave

Second wave

Philips

Sony

Sony demonstrated the first SXRD projector (based on a proprietary chip) in June 2003. The following year, Sony announced a projection TV based on SXRD technology. By 2008, the company stopped producing all projection TVs, including models based on SXRD technology. But the company did not abandon the production of projectors. Today Sony produces projectors for large installations and digital cinema with a resolution of up to 4096×2160 (based on the -SXRD chip) and an aperture ratio of up to 21,000