Communications: electrical – Digital comparator systems
Patent
1974-11-27
1976-06-15
Fears, Terrell W.
Communications: electrical
Digital comparator systems
350 35, G11C 1304, G11C 1144
Patent
active
039640329
ABSTRACT:
A wideband holographic information storage system records Fourier holograms on film in rapid succession, each hologram storing 128 bits of data. The hologram fringe pattern is held stationary by varying the reference beam frequency to track the variations of frequency of the signal beam that are caused by acousto-optic modulation of the signal beam. Holograms are successively recorded in adjacent positions by scanning a light beam across a photosensitive film with a rotating polygonal mirror, the recording light beam being wide enough to cover two facets of the mirror so as to achieve nearly 100% scanning duty cycle. During readout, a readout light beam is steered to compensate for prismatic deflection effects caused by variations in thickness of the film. The direction of the output beam is maintained constant despite a scanning motion of the incident readout beam, by reflecting the output beam a second time from a different facet of the polygonal mirror to compensate the rotational component of beam motion. Clocking of output data is self-synchronized, based upon modulation signals. Acoustically caused defocusing of the light beam is optically corrected. Methods are employed to reduce crosstalk.
REFERENCES:
patent: 3531184 (1970-09-01), Adler
patent: 3799652 (1974-03-01), Torguet
Fears Terrell W.
Harris Corporation
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