Askar KUTANOV^* and Yoshiki ICHIOKA

Department of Material and Life Science, Faculty of Engineering, Osaka University, 2-1, Yamadaoka, Suita, Osaka, 565 Japan

(Received August 25, 1995; Accepted June 3, 1996)

A conjugate image plane correlator with holographic disk memory is proposed. Optical correlation between conjugate images reconstructed from a holographic disk and an input image on liquid-crystal television is executed with the rotation of the disk. Regardless of Fourier hologram recording with the pseudorandom diffuser, it is found possible to take out the diffuser from the original hologram recording scheme using an image reconstruction process and to get correlation signals between input and reconstructed conjugate images in the output plane of a two-lens imaging system. Generation of conjugate replicas with high contrast causes exact matching with an input image which results in high recognition performance for autocorrelation signals. The transfer function of an optical system can be controlled by adjustment of either hologram size or hologram area illuminated with a laser beam. Hence, the output intensity distribution can be adjusted by selecting a proper pupil function and the size of an output pupil defined by the input pupil size and the optical system magnification factor. The real-time character recognition by optical parallel high-speed processing for two-dimensional images with position normalization is demonstrated.

Key words : correlator, conjugate image plane correlator, Fourier hologram, pseudorandom diffuser, holographic disk memory, character recognition.