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METATRON LASER PROJECTOR: WHITE PAPER MAY 1997
Technology has advanced so that it is now possible to design an Electronic Cinema laser projector that creates an image that is potentially better than motion picture film. For a projector to meet standard film specifications, the old way of designing laser projectors has to be rethought. The Metatron Laser Projector is designed to adapt for these film standards as well as the ultimate in computer imaging, thus designing for the future feature market.
The basic premise is that lasers are the light source of choice for projection of electronic
images. Gas lasers have been developed that are smaller and more efficient. Laser light is coherent and polarized. White random arc light, which is the choice of other projectors, is thrown away when it is polarized: Xenon (Hughes) and Metal Halide (Ampro)--Barco, NEC, Eidephor, etc. These arc lamps are short lived and fade over time. The picture is reduced as the lamp decays, thus causing uneven fading in color saturation. Our small frame gas lasers have a life of over 6000 hours. To be most efficient, the lasers are not run at full power. The light out put remains the same, until the tube is replaced; thus the color can be always kept at the same intensity. Thus lasers, as a source of light, are the best vehicle for a projector that is run many hours a day and in installations where projectors need to be color matched. Also solid-state lasers in green and red are becoming more powerful and cost effective. Blue power is not sufficient yet, so gas lasers are the most efficient at this time.
If the coherence and polarization is kept in the laser beam, the laser light is capable of producing images that have infinite depth of focus (IDF), thus being in focus along any line. This opens the door to a whole new concept in visual images. The image is automatically in focus on all areas of a dome, on water screens, or any irregular surface. Because of the high contrast and infinite focus, dimensional images (the stereo 3D) can be rethought. The image keeps its clarity and color, as long as the light ambiance is right, for huge installations. This is possible only with the projector architecture suggested in this paper. Other arc lamp projection and laser projectors that do not keep laser coherence need to be calibrated for a certain distance to be in focus on a flat screen.
The design architecture suggested in this paper produces images with higher contrast and provides the full color spectrum. Full spectrum color allows a more saturated film like appearance. You are not sacrificing contrast for brightness. Keeping the Laser coherence allows images to keep the IDF for curved screen projection. Laser lines scan evenly down the screen, the edges of the screen are as crisp and bright as in the curved center.
Since the assumption is that laser projection is state of the art, the next step is to look at the art of laser projection design and decide what specifications are needed to create a projector that has film quality images, is user friendliness, efficient and not costly.
I am the owner of laser projectors that were designed (over $80 million contract) for the Air Force command control war rooms. These projectors are the state of the art for laser projection. There were no patents applied for on this art. These projectors were used for over three years at the MAC and SAC Air Force bases. They ran 24 hours a day and always had to be up to military specification. I also received the intellectual property (optic design, studies, and electronics) on this technology. These studies greatly helped in determining the next most proficient design. Also having the 8 projectors from the Strategic Air Force command center in Omaha allowed me to have hands on experience and do upgrades that proved concept for the next evolution.
Others have attempted to write laser patents. One of the first patents that was issued for laser projection was for the Cavendish Projector (an English Patent). This patent was
then turned over to Advanced Laser Projection, Inc. Texas (5136426). Their system is not high definition, uses red dye lasers and Coherent argon lasers (Projector sells for over $200,000). The basic premise was to design a video projector based on the NTSC color standard, which uses an orange red at 610 NM. Red dye lasers are used because the nanometers in the red can be controlled. Dye lasers are inefficient and not user friendly.
Another laser patent also stressing 610 NM. orange was issued to Sony; 1993 (Tamada: 5,255,082), based on NTSC, PAL, or HDTV color standards. They create red with mixed white light (krypton for the red). They pull out a yellow beam to bring the Krypton red 647 NM down to 610 NM. This is inefficient and reduces brightness (more optic stations, more gas). Sony has not attempted to go into the laser projection business, probably because the premise of their patent does not work.
I believe that the basic premise of using 610 NM. red (NTSC/HDTV standard) is limiting, as discussed later. Samsung offered to back us and have access to the military intellectual property. The deal was not made and they have now introduced a laser projector based on the military projector. Acoustic optic modulators are used and the projector is not light efficient.
These specifications need to be addressed for digital projector to replace film projection:
1. Stable wide color spectrum: film comparable: at least 16 million colors.
2. The projector must be able show over 1500 lines of resolution. The higher the horizontal scan rate--Kilohertz (kHz), the better the resolution. The vertical Scan rateóis stated in Hertz (Hz). Both kHz and Hz must be high in specification.
3. The picture must have film quality sharpness, which is stated in bandwidth (MHz). The higher the numbers, the sharper the image. Sharpness can also be measured by contrast ratio. A film quality image must have a contrast ratio of at least 600 to 1, thus a superior gray scale, with the ability to project pure white and black blacks. The projector must have chip capability to image enhance all inputs, line doubling any feed 1000 horizontal resolution or less. A large projected high contrast image must not have artifacts, visible scan lines or pixels. There must be no shadow lag caused by fast action.
4. User friendliness for different feeds: the projector being downward compatible, accepting a variable scan rate between 2000 lines (horizontal resolution) as well as low end 425 lines or any other signal in between. (Adjusting to the input signals with horizontal scanning frequencies ranging from 15 kHz to 105 kHz).
5. The ability to put in enough brightness to illuminate motion picture screens of any size with motion picture quality brightness, uniformly covering the screen with light.
6. The image size of the picture is adjustable for any size projection i.e. (16/9 or 4: 3)
7. The projector is modular for quick changes of dysfunctional parts, upgradeable, and few moving parts (solid state) as feasible.
8. The projector has built in capability of creating perfect alignment with other Metatron projectors, not only with upper, lower and side edging but also with color matching. (Example: 6 projectors matched for a 180 ft. dome).
9. Two or more signal channels should be available so separate feeds can be placed through the projector at the same time for a stereo affect. Also the image enhancement chip should create even edges in the image for sharpened 3D fusion.
10. There should be an efficient use of the laser light, meaning less optics in the train and not throwing away light to keep polarization.
What is often forgotten is that the eye, when seeing an image, takes all aspects into consideration: --contrast ratio, color saturation, and brightness. The viewer wants to see an image, which is closest to nature. If the image sacrifices contrast for brightness, the picture appears flat, like a huge television screen, losing the motion picture quality image.
The reason many of the patents for laser projectors use red dye lasers is because the red considered with the most luminosity to the human eye is about 590-610 NM. This is a more orange red (NTSC red standard) probably set not because of luminosity, but because the television phosphors did not have the capacity for deeper red when the standard was set in the 30ís. The patents call for 610 NM. orange red, because they feel that red mixed with green and blue will produce a brighter image. This is because their basic architecture design is light inefficient. Thus they compensate by using color to make the image brighter to the eye. They forsake the broader bandwidth of color that is available in computer monitors and film.
A krypton laser is 647 NM red is a deeper red than the 610 NM, which is orange. Sonyís patent by stressing the NTSC based luminance chart suggests bringing the krypton to nearer 610 NM. by mixing in yellows. This avenue also is inefficient in the fact that the yellow lines have to be created with additional gas. The red dye laser is the ultimate inefficiency in the fact that it takes many watts of argon power to pump the dye laser. Also the dye is considered carcinogenic and is under OCHA control.
As stated, our purpose is to have an image as close to the natural color spectrum as possible. We thus use the krypton 647 NM red when we mix the colors. Yes, the orange has more luminosity for NTSC but the broader color spectrum mixed picture is much more pleasing to the eye. We also throw an even amount of red into our mixture, with equal amounts of green, and blue for a film quality color producing a perfect white in our color bars. I had the advantage of dye lasers in the military projectors, so I could test the mixes by changing the red. I found that the best color mix was in fact with dye that was comparable to the 647 NM. red: Krypton. Thus I have discovered that krypton can be mixed with argon blue and green lines for full spectrum color. Full spectrum happens when the edges of the color chart are contained in the mix. Thus I donít agree with the Texas patent and Sony patent that the red has to be 610 nm.
I have also found that color balance can be calibrated by using a mix of the secondary colors (cyan, magenta, and yellow) to produce white, the RGB color balance adjusted accordingly. Also if the red (without other mixtures) looks too red, for the viewer, the software can be adjusted to add a little green or blue to get the customers desired red. Thus this solution also gives more control to the feature director. Our combined laser beams produce colors beyond the NTSC or HDTV color standard. The mixture of our colors is comparable to film colors because of the greater color spectrum.
Optical imaging has made leaps in digital processing. This is shown most significantly in the film to digital and back to film process in a variety of new scanners made by Kodak, Philips, Rank, IBM etc. in the fact that they keep optimal color spectrum with high contrast and resolution. Needed is a projector, which can reproduce this digital imaging, without the back to film process. The Metatron Laser Projector is able to reproduce these images. By leaving behind the orange red 610 NM formula previously proposed for laser projection, our color spectrum is more like colors produced by the sun. We found that deep reds and purples, deep blues and honey yellows are cut from the color spectrum when 610 NM. red is used (see color charts) creating a flat enlarged NTSC television image. Deep red roses are orange. The deep scarlet football uniforms appear orange. The Metatronís full color spectrum allows fully saturated filmic images.
The Laser projector patents (Sony-Texas, and all red dye or add yellow patents) stress on using the orange red is because they need more brightness in their images, because under their configurations they do not obtain the light efficiency, and thus brightness needed (RF modulation, dye lasers, and many optic stations reduce efficiency) Also these projectors use Spectra Physics or Coherent lasers which are bulky and inefficient (more power and water) and have noisy power supplies creating an image with electronic interference artifacts. We have created laser tubes and power supplies, which answers the specifics needs of laser projection.
We have addressed, in order to obtain brightness, clarity and efficiency, the old laser projector paradigm, that states that it is impossible to have more than 60% light efficiency. We have created a new way of modulation that increases bandwidth and does not reduce the light flow.
The modulation for the military laser projectors as well as other laser projectors is based around acoustic optic modulation (AOMís), which uses RF signals for creating the video feeds. In our measurements we found that using AOMís reduced our light output by at least 20 - 30%. There is not a high end AOM built that has more than 60% efficiency. With the optic stations, polygon and galvo, the efficiency is reduced more. Testing the electric-optic-modulator as a substitution for the AOMís, we found that the most effective material still does not have the frequency quotient for the rapid modulation that is needed for the ultimate film quality image, thus reducing the bandwidth, which causes the picture to appear less bright.
The only other available modulation that I was able to locate was liquid crystal. It was assumed by all experts that by using liquid crystal, that we would loose the infinite focus capabilities that was so imperative to the Metatron projector. Even though the experts said that laser and liquid crystal would not work with brightness, film clarity, and most important, infinite focus, I did tests anyway to find another modulation to substitute for the lack of bandwidth and light loss of AOMs.
My finding in the first tests was that there was little light loss with lasers reflected off a light valve (liquid crystal with the image mirror reflected) instead of going directly through a liquid crystal display. The picture stability remained, if the right formula is used. Most important in my tests I found that laser light reflected off a light valve did not reduce the infinite focus. Laser light interacting with liquid crystal even seemed to excite the quality of light (reflective). I have not found any studies or verification of this excitement or acknowledgment of this capability in any technical papers.
Laser light is naturally polarized and coherent. Liquid crystal spatial light modulators (light valves) need polarized light to function. Arc lamps light needs to be polarized to work with light valves. Lasers are coherent and polarized so it is a natural match to use lasers with liquid crystal light valves. The laser scanning on the light valve does not disrupt the laser coherence and polarization, thus keeping the IDF of the image.
Other light sources used in projectors (Hughes, Ampro, Barco) such as metal halide and xenon lamps have to be polarized. Polarizing white arc light takes many optics. Half the arc lamp light is thrown out, greatly reducing light efficiency. Lasers do not loose beam quality, brightness or infinite focus if the right optic train is used to keep polarization.
Many optics are needed in the AOMs modulation method. Each optic takes away 1% of the light. AOM's are point specific, the laser beam needing to be reduced optically to hit the exact spot on the AOM to be most efficient. Also only the video signal in the laser beam is used and other parts of the beam are thrown away. Then there needs to be an optic to expand the beam after the AOM. The new architecture that I suggest using a spatial light modulator is optically simplified for more light efficiency by 10 fold.
A light valve allows the broadband modulation needed for film quality images. To create the image, we use the inherent advantages of a reflective light valve image with the CRT or another imaging device. CRTs are chosen to create the image, in the fact that they are the state of the art for the telecine industry. The CRT provides at least 2000 lines of resolution and has the open architecture to go beyond 2000 lines. The light valve we use provides the broadband and resolution needed for a good image.
Dr. Bleha of Hughes/JVC invented the light valve at Hughes in the 1970ís. He is supportive of my approach. He states that in their tests the light valve can accept resolution up to 4000 lines. In other words it is not resolution limited. I am choosing to work with JVC because that is the only light valve that I could locate that has the abilities needed for the best image. Also using CRTs and light valves allows open architecture for the next steps needed in the art of laser projectors (higher resolution and greater band width). This configuration also adjusts to variable feeds so any feed can be accepted up to 2000 lines at this juncture. I feel that the industry will discover that their SMPTE call for 1150 Ė1250 lines resolution is limited, when 2000 line resolution is available.
High-end film to digital back to film scanners use CRT imaging. We, however, want to keep the options open for other imaging devices to be modulated. We could create the picture with a horizontal polygon and vertical scanner (this method is used in our military projector). This image assembly creates the best image capable so far with the military projector (Evaluated by Worldview). To use this assembly as the imager, part of the gas laser could be directed to create the small image to be modulated by the light valve, or solid-state lasers could be used. Flat-panel liquid crystal variants (LCDs), field-emission displays, or other image generating devices (active matrix liquid crystal displays, electro-luminescent (AMEL) displays or micro-electromechanical (MEM) displays) and be used for creating the image to be modulated. Ultimately the new imaging chips that generate high-count solid-state pixels will probably be best.
One of the advantages of this architecture is that the imager does not have to be bright. We use infrared CRTs in our projector. The light valve responses best to this frequency. One configuration of imager and light valve or 3 could be used depending on the brightness of the image needed. If 3 are used the color is produced by using red, green and blue separately and then combining. If one imager and light valve are used the R, G, B are sequenced down the front of the light valve to produce the color.
The imaging chip is just now coming into its own and there are no real manufacturers of these chips at a high enough pixel count to substitute for the classic CRT imager. CRTs are off the shelf and create the high quality picture needed.
We use custom-made ceramic small frame laser tubes as our light source (krypton tube (2.5 watts) and an argon tube (12 watts blue and green). This will produce motion picture brightness on a 20-foot screen. For larger installations that need more power we multiplex. These small frame lasers are lighter than the commercial tubes, take less water, and are built with Beryllium Oxide (BEO), which does not take as much cooling. The tubes have a longer life than Spectra Physics and Coherent glass tubes. The tubes are 34 inches long and have a 3-inch diameter and, as stated above, can be multiplexed for more wattage. Also larger white light lasers can be used for the large installations. At this point the white lasers do not have a long life, and have to be constantly watched to make sure the ratio of krypton to the argon gas is correct. Thus white light lasers are best used in short events, so they can be recharged. White lasers are advancing on color stabilization, but in the mean time, our argon and krypton tubes run continually for more than 6000 hours without having the gas refilled, allowing a stable color image.
Eventually the smaller consumer market projector with one light valve and an imaging chip can be built with this architecture when solid-state lasers are available. As stated the best images has at least a 105 kHz horizontal capability. In contrast the military projector scanned the horizontal lines with a polygon. The polygon was 48 sided and was able to rotate at 42,000 - 46,000 RPMís which provided 1125 \ 1350 lines of resolution. In order to go over a 2000 line resolution, we could use a 96 faceted polygon or a much faster motor. However the speed of the motor for the polygon, even at 96 facets pushes the technology and is mechanical, thus making the projector less solid state based. The AOMs did not allow the high horizontal band width needed to take advantage of the new multiplex addressing from the computer graphics and scanning world that creates the best images (projectors now convert the high band width to a lower bandwidth for projection). Galvos are efficient for the vertical lines, but that still keeps us in the mechanical moving part world. With the new architecture, there is the capability of producing over 2000 lines. That means that we could line double HD. That capability is being worked with now. Higher horizontal resolution high definition 1124 can be image enhanced and line doubled with upgraded image enhancement chips.
The most advanced AOM's still limited our light efficiency and our modulation frequency. The industry needs a digital image that is film like, not a big TV. For film quality, needed is at least a 90Mhz (-3 dB) bandwidth. The AOM's or the EOM material does not give a high enough modulation frequency to give the highest in bandwidth. All the laser projection patents I have looked at are either limited by polygon spin, AOM's or EOM's, thus limiting brightness, contrast ratio, bandwidth and resolution.
By using an active matrix liquid crystal with over 2.4 million pixels as a transmisive device or liquid crystal or liquid crystal/polymer mixture as a reflective device (light valve) and the right optics, it is possible to retain over 80% brightness efficiency, over 600-1 contrast and very high bandwidth. The imaging technology is now pushing into new capabilities that make this possible (more pixels to create a high-resolution picture). Also by taking advantage of clocking and field-sequential imaging, we are able to manipulate electronically the picture size. Since laser projection has infinite focus, which is retained with the light valve, often users wish to project on to a certain object, such as a statue in the distance, without changing the projection lens. Electronic pixel control allows us to project on the statue and then shift to a large screen with the same size image, adjusted (a preset program for immediate shift from one size to another for specialized installations).
Further, as stated earlier, by using Liquid crystal for modulation in a reflective device, any of the known image writing devices can produce the image to be reflected and amplified, CRT, active-matrix crystal displays (AMLCDs), Electro-luminescent (AMEL), or solid state chips. Also the state of the art imaging with a polygon and galvo or other mirror scanning can be used to write the picture on the back of the light valve.
Because the nature of laser light is a polarized coherent beam that means that the beam can be directed. I found that instead of flooding the light valve, as is done with white arc lamps, a scanned laser beam can be synchronized with the modulation in the liquid crystal produced by the image. It would be impossible to reduce arc lamp light to an evenly spread line to accomplish the same.
The beam is made into a line by a line generator optic. This optic has to generate a line that has evenly distributed laser light to project an even light field. A galvo (only moving part) sweeps the generated laser line across the light valve and thus the viewerís screen. Artifacts appear if the beam is not evenly spread. The galvo is also used as a steering mirror for the laser light when it is scanning on the light valve in sync with the modulation of the imager (CRT scan) to save on optic surfaces. This reduces the optic train even more for the light efficiency of the system. In the tests as stated it seems that the light valve actually amplified the laser light. Also the modulation is a much higher bandwidth than is possible with AOMís.
It is also my premise that when laser light is applied to liquid crystal, the photoconductors increases the light conductivity. Maybe it is because of the natural polarization of the laser light that stimulates the liquid crystal in a way we do not understand to enhance the laser light out put. Or maybe the explanation is that the laser light causes an electric field to develop in the liquid crystal corresponding to the intensity of light. Laser light stimulates the electric field considerably more than other light sources in that it is illuminated polarized light.
1. The Metatron projector makes use of the multiple colored polarized coherent spread laser beams to produce a full colored projected image.
2. The colored laser beams are each optically spread to create uniform small-elongated beams (laser beam line generated).
3. The laser line is directed to a galvo, which is synchronized with the aperture cycle of the light valve and CRT. The liquid crystal material spatially modulates the image produced by the CRT.
4. More brightness is achieved in the projected image because the laser beam is optimally placed where the scanned information is written on the light valve. The laser light is thus used efficiently.
5. Arc lamps only have the ability to flood the light valve, thus reducing the contrast with light bleeding into the black off position of the light valve.
6. The generated laser has even distribution of light that is scanned on the light valve to be evenly dispersed on the screen or object.
7. This eliminates laser diffraction or artifacts that might come from flooding the light valve with lasers (laser light is precise and shows any defects).
8. The CRT image is analog so that the modulated image is smooth with no scanned lines or pixels.
9. The modulated polarization of each of the scanned laser lines is converted
to modulated intensity by means of a polarization cube of wave plate.
10. The modulated laser beams are optically combined to produce a multicolored full color image (one light valve configuration or three).
CREATING THE IMAGE:
1. The image can be created using the classic polygon galvo approach, galvo rotating cube, or other mirror scanning systems. This however is limited in the fact that rotation of the polygon is not fast enough to produce the high resolution that I believe is needed for images that look like film. Also this is an expensive approach and not user friendly.
In the configuration I suggest, the liquid crystal device would modulate the raster created image (not AOMís). Going directly through a liquid crystal panel is possible (transmisive). The electronic grids in the panel, however, create artifacts in a large laser projected picture. Thus I suggest using the light valve where the image is reflected with a mirror and not using a tranmissive method.
A very good image is created with a many faceted polygon and a fast galvo. This configuration would also produce a scan much like the CRT scan. Infrared laser diodes would be used and the color would be still produced by polarized spread laser beams. The imager, scanned color spread laser beams would all be synchronized with the liquid crystal modulation. I feel, however, it is better to remain with solid state imaging (CRT, imaging) instead of using moving mirrors and motors.
In final analysis the most important part of this equation is this: synchronizing the laser with the scan of the imager and modulation produces the more light efficiency. The scanned laser line creates the colored image. If the image is produced by the classic polygon galvo approach then the image is modulated in the light valve. This in fact would create a good image, but is costly and limited as stated above. When fast field sequential pixel clock new imaging devices are created better imaging will be available. CRTs produce the best images now.
Whether optical, electro-optical or mechanical imaging device is used, the importance for brightness is that the imaging device is switched synchronously with the display. This process of using laser scanned laser light produces at least a 4 times brighter image than with the flood method. All the light is going to one line scan that is thus directed to the screen. Thus all the light is in each line scan instead of wasted on a flood. With a flood the light is dispersed so only a portion of the light goes to the screen.
2. REFLECTIVE APPROACH: CRT
The input digital image is directed into one or three high definition CRT's, or other high definition imaging device. The image is addressed to a photoconductor and modulated. The colors are created by red, green and blue laser light. The laser light can be white and then separated and sequenced on one valve. The laser light can be separate R, G, B or secondary cyan, magenta and yellow (also produce white). These 3 beams can be sequenced down one light valve or directed separately to 3 light valves. The beams can be sequences on one light valve and will not need combining. This will be best for the consumer and theatrical market. If three separate light valves are used, the images are combined before going through the output lens. Three light valves offer more brightness and are used for larger installations or screens.
The advantage of a reflective imager (mirror overlays the underlying circuit elements) is that there are no aberrations in the projected image from the electronics. The high end Barco system uses the transmissive device. The image is good, but on closer view the electronics from the liquid crystal device shows in the screen. Also the laser projector suggested allows a much higher contrast image because the light is not bleeding into the black in the liquid crystal as it would with a light flood.
The LCD, CRT, or other imager can be black and white in the fact that the lasers are creating the color with this method. The liquid crystal light valves designed for green, red and blue can be used. The higher the pixel count in the imager, the more film like the picture. The one valve configuration is probably better when solid-state lasers are available. This optimal process is the basic platform in the patent for less bright applications. Three CRT light valve configurations will be used, which produces more light for larger screen applications.
This projector can accept any input: NTSC, PAl, SECAM video, and 1280 X 1024 images. This creates compatibility with VGA/Macintosh, Sun, Hewlett-Packard, and Silicon Graphics workstations. 4000 by 3000 resolution images can be created, when the CRT or other imager is capable. thus creating an even better image. The design we use reduces mirror stations and eliminates the AOMs thus creating a 70%-80% light efficiency. When using the liquid crystal for modulation, there appears to be an amplification of the light. Laser light is already polarized so a polarizing filter does not have to be used as in other light sources, which reduces the light output.
Laser light that still possesses its coherence and polarization does not lose its potency as it travels through space. Arc lamp light and non-coherent laser light loses its strength when it travels through space. Thus the brightness of our scanned line on the screen is still vivid when it hits the screen. Thus not as much laser power is required for brightness. My estimation is that one watt of white laser light is needed for an 8 by 12 screen, 6 watts are needed for a 20 by 24 screen and 16 watts of white light are needed for a 60 by 64 ft. screen. This is probably underestimated. 8 watts of white light can project a motion picture image brightness image on an IMAX dome. An amplifying lens is used (magnifying) if a short throw is needed. This introduces a whole new area in physics as using infinite depth of focus laser light is explored.
Best for our application is that since the coherent laser light keeps its power through space, we do not need over kill out put lenses as other projectors need. We do not move the light with magnifying lenses. Thus we use a simple out put lens that costs less than $5000. This saves a great fortune, because the other projectors often need a lens costing over $30,000 to get their image on a 20-foot screen. Also a simple output lens is a lot more light efficient that an over kill lens needed by other projectors.
SPECKLE EFFECT AND INFINITE FOCUS:
The modulation gives an evenly spread picture which has infinite focus. Also by mixing laser light and liquid crystal the speckle effect that usually is prevalent in laser projection is greatly reduced. Of course using the right screen material also greatly reduces speckle.
DESIGN REDUCES MOVING PARTS EXCEPT FOR GALVO:
The image size is adjusted through electrically manipulating the picture. This configuration reduces the mirror stations, in comparison to other laser projection techniques. Using liquid crystal as a modulating device reduces the need to pinpoint the beam to a small area by using a beam compressor, then beam expand the laser beam (as optically done with AOMís). By using the LCD or CRT or other imagers for creating the picture, the mechanical driven scanning mirrors are eliminated. The laser projector becomes more modular and solid state. The only moving parts are the galvos we use to scan on the modulation openings. The set scan rate would be at low frequency (60 cycles). Galvos are designed to run at much higher frequencies. In fact 180 scans per second is still moderate for the galvo technology. For years galvos have been tested in many applications and are very stable mechanically. In fact galvos were used in the military projectors. The military projector we still have running ran for 24 hours a day, 7 days a week for 3 years in the SAC war room in Omaha. We still use that same galvo and have never had to adjust or replace it. I state this to show that even though a moving part, galvos are very stable for a user friendly and long lasting application as the one moving part in this laser projector architecture I suggest.
LIQUID CRYSTAL FORMULAS:
Liquid crystal contains all the variations including active-matrix (AMLCDs), Polymer LC (PLC) and Ferroelectric LC (FLC). As the superior speed of FLCs mature, these devices used in our displays will enhance even further the specifications of the state of the art. In other words we will be able to modulate at much higher frequencies. We will want at least 180 scans per second for the stereo imaging. Also this higher scan rate would be best for the full color sequenced image with the single light valve. Dr. Bleha has stated that the Hughes/JVC light valve can handle this modulation, but we have not tested that aspect as of yet.
Edge matching is built into the projector in order to match all sides of the image for aligning two or more projected images in a continuous screen. This is especially necessary for dome environments where 3 or more projectors are matched for a seamless image. Matching the colors for each projector, and synchronization of each projector so it presents a seamless image has previously been an almost impossible task. Other projectors have problems in matching colors, because their lamps are at various stages of decay, thus putting out different color intensities. Matching colors in a dome environment becomes a nightmare with these technologies. This alignment and color match can also be used for large Cinerama screens and other large installations other than domes.
ENHANCEMENT CHIP: BEST SIGNAL THROUGH: DIGITAL PROCESSING:
By using three major processing procedures, the final image is enhanced and doubled.
QD Technology developed this enhancement technology. They have been working in conjunction with Metatron developing the signal processing that is needed for this form of projection.
1. The first separates luminance and chrominance while maintaining all available resolution. Advanced signal processing techniques are used that remove artifacts, dot crawl, Moirť patterns and cross color bleeding, while enhancing the Chroma signal and detecting motion in the field.
2. This processing doubles the lines by interpolating a new line between each pair of lines in a field, producing progressive line fields per second. This process uses proprietary processing techniques to interpolate both luminance and chrominance, providing smooth step free edges. Adaptive processing is performed on a line-by-line basis. When motion is detected in the picture the system adapts between vertical and temporal interpolation.
3. The final processing enhances the luminance and provides 1050 line output adapting its processing on a sample by sample basis. The ability to also line double 1000 lines is being developed. Thus a HD feed can look better translated up to 2000 lines.
The above processing allows control over edge matching stability, the control over color hue and saturation, and matching brightness and contrast. When we were demonstrating the military projector (polygon and galvo) and projected a line doubled 525 horizontal resolution images using the classic off the shelf line doubler, we could actually count the scan lines on a 60 foot screen If line doubled 1050 lines of resolution are projected on such a big screen, the lines were still obvious. The line doublers on the market do not take into account the high contrast ability of laser images. Thus we worked to develop QD box. This processing was developed to fill in the line sequences so the laser projected scan lines are not apparent on large image formats. Also this processing, because of the edge enhancement, improves the 3D fusing by the brain for stereographic imaging. In the light valve modulated system that we suggest, the liquid crystal smoothes the images and we do not see lines, but the QD box still provides important massaging of the image, especially with lower resolution images.
The projector can be built to take two or more feeds, so a computerized program that flashes two or more sets of information with a shift for imaging, so auto stereo can be implemented. Thus the auto stereo can be rethought due to the holographic possibilities that IDF provides. Combining different captured angles of the image also produces the auto stereo experience if the IDF is taken into account. Also different shifts that can be done with color, phase modulation or using different sequenced screens for the always-focused image produce auto stereo effects. The QD box with the image enhancement gives support to the best in stereographic viewing.
1. Laser projector uses argon and krypton small frame lasers
2. Krypton 647 NM red; Argon 514 NM green; and Argon 473 NM blue
3. Laser projector can use argon/krypton mixed gas white ion laser
4. Laser projector can use solid state or diode pumped lasers
1. Separate RGB beams are vertically scanned to synchronize with modulation
2. Image is created with CRTs (or other imaging device)
4. Image is modulated with a light valve
5. Beam combined with prism, dichroic mirrors or filters; directed to out put lens
1. Argon and krypton small frame lasers used
2. Argon optically split for blue and green beams
3. Three beams optically spread into line
4. Galvos direct beam to light valve
5. Polarizing beam splitter used to direct beams to light valve
6. Images merged with dichroics
7. Simple out put lens used (infinite depth of focus does not need complicated lens)
METATRON LASER PROJECTOR (consumer)
1. Solid state lasers produce RGB
2. The lasers are synchronized down face of light valve with a galvo.
3. One CRT or other imager
4. A simple output lens is used.
The Metatron Laser projector uses custom made smaller laser tubes for images up to 20 ft. by 24 ft. We multiplex two krypton tubes at 2.5 watts each for five watts of red and one argon tube which produces 3 watts of blue and 3.5 watts of green (some cyan green discarded). That gives us 9 watts of white light that can produce at least a 30 by 34 foot screen of motion picture brightness. When a picture size over 40 ft. is desired with motion picture brightness, we are now using large frame krypton and argon lasers for 14 watts of white. Also we can use multiplexed small frame lasers for such an installation. We need 6 Ė 8 watts of each color for at least a 10,000-lumen picture on a 24-foot screen.
The images are very clear on a huge screen (60 by 80 feet). For the replacement of a IMAX or OMNIMAX image, it would be best that the imager and light valve or spatial light modulator be at least 2000 lines of resolution. Using the QD Technology image enhancement box to double the lines (laser player or beta feed) for the 1300 lines of resolution creates a good image on the larger screen. We know of no other digital projection system, which is able to create such a large image with the picture brightness, contrast, and imaging. The cost of such a projector is comparable to the Hughes 300 models. Other large screens, which are low resolution, also are much more expensive. LED screens are very bright, but are low resolution and very expensive. They, however, do not demand upkeep.
The Hughes 12 K provides a great picture that is 40 feet. We use their high-end light valves and their CRT. We are able to get a comparable picture, which has infinite focus, better color saturation, better contrast that can project on a larger surface. Our projector, at this time, thus far surpasses anything on the market for large screen video projection.
A patent is being written which includes using the full spectrum colors (649 nm red), one or three light valves with any imager, synchronizing the sync of laser scan, imager and modulation of the light valve, and retaining the infinite depth focus of the laser. The prototype alpha projector has been build to prove concept and can be demonstrated. Also we have a comprehensive solid-state laser patent, which was granted in 1994. This is for a digital projector using continuous wave solid-state lasers. The patent also suggests that solid-state lasers can be used to modulate the image, which has not been explored so far in the industry.