Laser Video Projector
A laser video projector is a device that a video signal and converts the signal to a modulated laser beam to project moving images. It works either like the electron beams of a Cathode Ray Tube television or CRT which reads the whole picture a dot at a time and modulates a high frequency laser directly, or like that of a DLP which spreads optically as it modulates the laser and reads the image a single line at a time. Laser video projection can produce the widest range of colors compared to all other available display technology today.
The history of laser video projectors dates back to the 1970s when the first theatre laser projector was built with a Spectra-Physics design which had 164 ion lasers. Designers discovered the use of special output mirrors for simultaneous lasing of green, red, yellow, and blue wavelengths. The beam that this created was seen by the eyes as white in color. This beam was then subjected to a high refractive-index prism that enabled separation of the colors blue and red for about two degrees of between each shade. That was when laser projection technology was discovered.
The first laser projector was very big, especially if one compares it to the present day technology. It was enclosed in a relay rack cabinet that was about six feet tall and two and a half feet squared. An aluminum plate that was half an inch in thickness divided the cabinet from the laser projector. A four feet long laser head was fixed on one side of the plate vertically pointing the laser head downward.
The laser beam was then reflected to the other side of the plate. White laser beam was focused onto a piece of glass or quarts to refract the beam into different directions and different colors. The four refracted beams of different shades of colors were then reflected through acousto-optic modulators that can control the intensity of the beams electronically.
The first picture produced the by the first laser projector was not very much defined. With the many advancements of technology since then, laser projection is how the foundation of any graphic system.
Today's laser video technology takes the video signal and introduces it to the laser beam with the use of an acousto-optic modulator or an AOM. This uses a crystal that refracts images to separate the beam at certain angles. The beam passes through the crystal at specific angles of the AOM crystal and a piezoelectric element converts the video signal into vibrations in the crystal to produce a diffraction grating effect. Diffraction grating splits light into several beams causing the beams to travel in different directions thereby creating a wide range of colors.
A rotating polygonal mirror that rapidly rotates enables the laser beam to have horizontal refresh modulation. A curved mirror causes the beam to reflect onto a galvanometer- mounted mirror that enables the vertical refresh modulation.
It is now possible to project videos on any type of projection surface. Contrasts, color space, and sharpness are now higher than that of other projection technologies. Laser video projectors give lower luminous flux output compared to conventional projectors.
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