G - Physics
11
B
352/32.2
G11B 7/00 (2006.01)
Patent
CA 1125434
ABSTRACT This invention relates to an apparatus and process for writing video information in the form of a frequency modulated signal upon a video disc member and for recovering video information from the video record . The video disc member formed by the writing apparatus is also described. The writing apparatus includes a laser as a source of a laser write beam and a write optical system for directing the stationary laser write beam to a moving video disc member. The video disc member comprises a substrate member carrying a light responsive coating on at least one sur- face. The write optical system focuses the beam to a small spot of light approximately one micron in diameter upon the light responsive layer. The intensity of the focused spot is changeable under the control of a light intensity modulating assembly. This light intensity modu- lator changes the intensity of the write laser beam with respect to a predetermined threshold intensity sufficient to form a first type of indicia in the coating. Circuitry is described for using a triangular frequency modulator for driving the Pockels Cell driver and for obtaining a sinusoidal-shaped light modulation output signal from the linear polarizer. The output from the linear polarizer is adjusted such that the half power point from the polar- izer equals the threshold power level of the material forming the information storage layer. A second harmonic bias circuit is employed for removing the second harmonic intermodulation distortion of the modulated write beam.
336315
Discovision Associates
Gowling Lafleur Henderson Llp
LandOfFree
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