High-performance FLC display as a spatial light modulator for optical signal processing

TLDR: In this article, a transmissive ferroelectric liquid crystal display (FLCD) with high performance is presented, which will be operated as an SLM in an optical pattern recognition system using incoherent optical spatial frequency analysis (OSFA).

Abstract: Optical computing and signal processing is a growing field of scientific research and now more and more entering into industrial applications. Therefore, fast switching spatial light modulators (SLMs) are needed for displaying and filtering processed information. In this paper we present a transmissive ferroelectric liquid crystal display (FLCD) with high performance which will be operated as an SLM in an optical pattern recognition system using incoherent optical spatial frequency analysis (OSFA). The layout and the manufacturing process of the display have been designed especially for the requirements of SLMs in optical systems. The matrix is consisting of a square matrix of 512 columns by 512 rows with a spatial resolution of 508 dpi. An additional black aperture diaphragm of 1 mm is introduced around the active area in the switching plane of the FLC. The display is passively addressed with a multiplex driving scheme using the intrinsic bistability of the FLC. Each pixel of the display represents a switchable half wave plate, resulting in binary amplitude or phase modulated pictures dependent on the polarizer settings. Using an FLC with a high spontaneous polarization and a high pretilt at the substrate surfaces, we obtain excellent contrast ratios of 100:1 and a very high switching speed based on a row address time of less than 7.5 microseconds allowing frame rates up to 500 pictures/sec.