ABSTRACTSpatial light modulators (SLM) are examined from the viewpoint of miniaturization and optical correlation systems. The structure and behavior of a silicon-chip active-matrix-addressed ferroelectric liquid-crystal SLM is presented. Theresponse of an amorphous-silicon optically addressed nematic liquid crystal SLM is reported. 1. INTRODUCTION Practical optical processing systems are designed for compactness and stability. The optical correlator is an example of engineering progress in two-dimensionalprocessing. We are developing miniature spatial light modulators (SLM) which will facilitate the development of compact and lightweight correlators.1Electronically addressed SLMs (EASLM) provide a programmable correlation filter, and also the input scene, with theaid of a TV camera. The alternative EASLM technologies are essentially: magneto-optic, deformable-mirror, andliquid-crystal. Magneto-optic devices are inherently current addressed and therefore difficult to integrate with silicon.This consideration determines the lower limit on device total volume and power consumption.2 Deformable-mirrordevices have been integrated with silicon electronics, but the phase/amplitude characteristics are not optimum forcorrelator applications.3 Compactness, speed, and enhanced correlatorperformance canbe achievedby integrating liquidcrystals and silicon-chip technology.46The voltage-controlled birefringence of nematic liquid crystals (NLC) can provide continuous phase modulation, or, inconjunction with polarizers, a combination ofamplitude andphase modulation.7 In correlatorapplications, a ternary-statedevice having phase modulation states and a zero amplitude state is desirable.8 NLC devices can achieve theseternary states with the additional complication of waveplates; however, the subkilohertz response speed of NLC devicesis inadequate for correlation-filter applications. Ferroelectric liquid crystals (PLC) provide the necessary filter-planeresponse speed. Moreover, the FLC device is based on rotation of the optic axis, which can readily provide the requiredternary-state filter.911