Abstract

We report here novelty filters using three kinds of optically addressed spatial light modulators (OASLMS) composed of amorphous silicon photosensers and ferroelectric liquid-crystal (FLC) light modulators. These novelty filters are based on polarization modulation of the OASLMs.¹ The first novelty filter is constructed by placing a photovoltaic-transmission-mode OASLM between two polarizers. The optic axis of the liquid crystal in the OFF state and the transmission axes of the two polarizers are aligned in parallel. When an intensity-modulated lightbeam is incident upon the OASLM, the beam passes through the second polarizer before the device can respond to the signal. After the OASLM responds to the optical signal, the optic axis of the FLC rotates by 45°, thus rotating the polarization of the input light by 90°, causing it to be blocked by the second polarizer. Therefore, a novelty filtering of the input is obtained at the output. The second novelty filter uses two OASLMs with an externally applied voltage. The two OASLMs are connected by an ac power supply such that they are alternatively turned ON when they are illuminated by a light beam. The third novelty filter uses an OASLM with a special alignment of the FLC. This system performs novelty filtering by using the charge spreading property of the OASLM.

© 1990 Optical Society of America