Optical pattern processing utilizing nematic liquid crystals

This paper describes a new type of optical processing based on the dynamic scattering effect in liquid crystals. It is possible to realize a binary spatial filter with nematic liquid crystals and to control the optical modes by voltage signals. A two-dimensional Walsh function is used for extracting properties of the input patterns. The realization of an 8 x 8 Walsh function filter with nematic liquid crystals is demonstrated. The contrast ratio is over 30 to 1. The variation in transparency is within +/-3%. Experimental results show that it is possible to extract the properties of handwritten characters by detecting the intensity of light transmitted through both the input pattern and the liquid crystal filter.