Photoactivated liquid crystal light valves

CdS photoconductive films have been combined with both nematic and nematic/cholesteric liquid crystal mixtures to produce a broad class of photoactivated light valve devices. These devices span a spectrum of applications that includes: 1) real-time projection display; 2) image storage projection display; and 3) real-time inputs for optical data processing. The work reported here is a development on earlier results in which ZnS and selenium were used as photoconductors. Among other advantages the new devices are far more sensitive than the earlier devices, and (as opposed to ZnS) can be activated with visible light (0.510 µm). The projection cells act as high level light intensifiers. Intensification ratios of 10⁴have been observed. The cells used for optical data processing transfer spatially distributed information from noncoherent to coherent light beams. Coherent light efficiencies of 92% have been observed. Typical performance figures for these cells are: Projection Cell Coherent Light Cell Resolution 60 lines/mm 35 lines/mm Write Beam Intensity 0.12 mW/cm²Sensitivity 0.015 mJ/cm²-- Excitation Time 150 msec 15 msec Turn-Off Time 1-2 sec (erase) 120 msec (decay) Storage Time Months Contrast Ratio 10:1 500:1 Cell construction, device characteristics, and performance will be discussed for each of the three classes of device.