Talaria was the brand name of a large-venue
video projector
A video projector is an image projector that receives a video signal and projects the corresponding image onto a projection screen using a lens system. Video projectors use a very bright ultra-high-performance lamp (a special mercury arc l ...
from
General Electric
General Electric Company (GE) was an American Multinational corporation, multinational Conglomerate (company), conglomerate founded in 1892, incorporated in the New York (state), state of New York and headquartered in Boston.
Over the year ...
introduced in 1983.
Light from a
Xenon arc lamp
A xenon arc lamp is a highly specialized type of gas discharge lamp, an electric light that produces light by passing electricity through ionized xenon gas at high pressure. It produces a bright white light to simulate sunlight, with applications ...
was modulated by a
light valve consisting of a rotating glass disc that was continuously re-coated with a viscous oil. An
electron beam
Since the mid-20th century, electron-beam technology has provided the basis for a variety of novel and specialized applications in semiconductor manufacturing, microelectromechanical systems, nanoelectromechanical systems, and microscopy.
Mechani ...
similar to the one in a
cathode ray tube
A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms on an oscilloscope, a ...
traced a
raster on the surface of the coated glass, deforming the surface of the oil. Where the oil was undisturbed, the light would be reflected into a light trap. The raster traced into the oil formed a
diffraction grating
In optics, a diffraction grating is an optical grating with a periodic structure that diffraction, diffracts light, or another type of electromagnetic radiation, into several beams traveling in different directions (i.e., different diffractio ...
.
The basic unit was monochrome (PJ7000 line). Color display is accomplished in one of two ways:
The single lens color projector (PJ5000 line) use
dichroic
In optics, a dichroic material is either one which causes visible light to be split up into distinct beams of different wavelengths (colours) (not to be confused with dispersion), or one in which light rays having different polarizations are ab ...
filters to separate the white light of the xenon bulb in two channels, Green and Magenta.
RGB color separation and processing is obtained using vertical
wobbulation of the electron beam on the oil film to modulate the green channel and sawtooth modulation is added to the horizontal sweep to separate and modulate Red and Blue channels. The optical system used in the Talaria line is a
Schlieren optic like an
Eidophor, but the color extraction is much more complex.
Two units (MLV) or three units (3LV) are stacked one atop the other, each one devoted to a single color (3LV).
In early models (PJ5000), the light source was a 650 watt xenon bulb (sealed beam) similar to the units in modern 35mm film projectors, and produced 250 lumens at a 75:1 contrast ratio.
[ ] The later 3LV model produced as much as 3500 lumens at a 250:1 contrast ratio.
The later LV series had an optional "Multiple Personality" (MP) module that would allow the projector to display various resolutions and scan rates produced by computers of the time. It could produce an 8,000 lumen image onto a 15 foot by 20 foot screen from 64 feet away.
See also
*
Comparison of display technology
References
{{Thermionic valves
Projectors