A new electro-optic light valve, based on the Pockels effect in a KD2PO4 crystal addressed by photoconduction, is described. At the present stage, the picture exhibits a resolution of 20 lp/mm (line pairs/mm), a very uniform contrast of 40/1, and an extensive grey scale; the writing time is less than 10 μsec. The device allows image addition and image subtraction and can be used as an input device in optical coherent processors.
Laboratoires d'Electronique et de Physique App1iqui.e 3 , avenue Descartes 94450 Limeil Br6vannes (France)
ABSTMCTThe scanning limitations of rms responding liquid crystal devices due to the lack of sharpness of the transmittance characteristic can be overcome in the case of the twisted nematic configuration. Indeed, it is possible to obtain a linear output polarization from an electrically excited cell, and then to decrease the transmittance level of the non selected dots without altering the optical efficiency for the selected dots by rotating the output polarizer perpendicularlyto the transmitted vibration. A 64 x 64 element matrix display using a biphenylcompound has been constructed and operated in the transmissive mode. The contrast ratio obtained with a duty factor equal to 1/128 corresponding to a 128 line display is 20:l. The address and the information pulses respectively applied to the lines and the columns are V1 = 12.4 V and v2 = f 1.1 v.
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