This paper reviews the operation of the hybrid field-effect liquid crystal light valve (LCLV) and summarizes the performance useful for real-time coherent optical data processing. The light valve is basically a high resolution optical-to-optical image converter. The device embodies a CdS photoconductor, a CdTe light-absorbing layer, a dielectric mirror, and a biphenyl liquid crystal layer sandwiched between indium-tin-oxide transparent electrodes deposited on optical quality glass flats. The input image is directed onto the photoconductor to reduce the impedance of the photoconductor, thereby switching the ac voltage that is impressed across the electrodes onto the liquid crystal to activate the device. The ac operation ensures long operating life for the device. The liquid crystal is operated in a hybrid field-effect mode. It utilizes the twisted nematic effect to create a dark off-state (voltage off the liquid crystal) and optical birefringence to create the bright on-state. The liquid crystal modulates the phase of the coherent readout light. By an additional analyzer, an intensity modulation is created. The current performance of the light valve is reported with the present performance for resolution, interharmonic distortion, signal-to-noise ratio, contrast ratio, and response time.

Date Published: 4 December 1979
PDF: 3 pages
Proc. SPIE 0201, Optical Pattern Recognition, (4 December 1979);

Published in SPIE Proceedings Vol. 0201:
Optical Pattern Recognition
David P. Casasent, Editor(s)