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The ProFX and Taurus laser video projectors display large video images using lasers as a light source. Full color images are produced on any surface up to 30 feet across in high contrast. Even larger images are possible with a fully darkened environment. The focus of the image is crisp over an extremely large depth of field, thus allowing for clear images on screens that have irregular surfaces.
The ProFX is a video only projector and the Tauru is a projector that produces simultaneous video and conventional laser light show effects. Either units is 29 inches wide, 51 inches tall, 70 inches long and weighs 1200 lbs. They use 208 VAC three phase power, 125 amps per phase and require 5 gallons per minute of cooling water. The image emerges from the top of the unit and is directed to the screen(s) by a computer controlled steering mirror.
Full color laser video projection requires red, green and blue laser beams. The green and blue beams are produced by argon ion lasers and the red beam is produced with an argon pumped dye laser or 1 or 2 mixed gas "White Light" lasers. Specific frequencies of color are precisely produced in order to project a proper color balanced picture. The three beams are modulated using acousto-optic modulators according to the decoded incoming video signal. The three modulated beams are then combined into a single beam and then scanned into a raster video image. The horizontal scanning is accomplished using a rotating polygon mirror and the vertical line displacement is by a galvo driven mirror in sync with the incoming video vertical sync pulses. Different lenses in the final path allow for different fixed image sizes or different zoom lenses are available for real-time control of image size during projection. Optical and electronic systems allow for inverted images, left-to -right reversal for rear projection and variable image aspect ratios from 4:3 to greater than 16:9.
Light Production
Color video signals are produced by using red, blue and green. With the ProFX and Taurus projectors, the same is true, but the three colors are created with laser light produced by one or two Argon Ion lasers or one or two mixed gas lasers. The lasers use custom dichroic filters and custom electronics to produse the proper red, green and blue lines for video projection. The blue and red lines, in particular, are different than conventional colors seen in laser light shows due to video requiremnets for proper color and white balance.
Light Modulation
Once the proper red, green and blue beams are produced, each must be modulated with its correctly decoded video signal. This is done with one acousto-optic modulator for each beam. An acousto-optic modulator operates by the interaction of a very high frequency sound wave traveling through a crystal material. The laser beam passes through this crystal at approximately 90 degrees to the traveling sound wave. The sound wave is varied by the incoming video signal causing distortions in the crystal and the light diffracts off the variations as if they were, in effect, a solid diffraction grating. The angle at which the light is deflected is very small and different for each color and the light is only deflected when a video signal is present. The electronic circuitry of the projector supplies the individual red, green and blue signals to the modulators in response to the video input.
Beam Combination
The three modulated beams are combined into one beam by special optics for horizontal scanning by the polygon line scanner. The input to the polygon scanner is now a single laser beam, in effect, a very intense white laser beam (comprised of red, blue and green) that is modulated with both chroma and luminance information.
Scanning
This combined beam is reflected off a rotating polygon mirror spinning faster than 30,000 rpm. This produces a horizontally diverging fan of light. This horizontal fan is then collimated by a first relay lens into a "ribbon" of light which is then focused into a spot by a projection lens onto the vertical scanning mirror. This vertical scanning mirror is swept in the vertical plane by a galvo which is precisely in sync with the vertical sync pulses. The process of scanning produces a raster scanned picture deflecting the beam horizontally and vertically, perfectly timed, to place the individual video pixel information at the precise locations in the picture frame.
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Linden Laser Systems 2615 State Highway 13 Lampe, MO 65681
