Hussain, G. and Eason, R.W.
Velocity filtering using complementary gratings in photorefractive BSO
Optics Communications, 86, (2), . (doi:10.1016/0030-4018(91)90543-M).
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We demonstrate a new optical technique for velocity filtering and feature extraction of time varying optical images. The technique exploits the recording of complementary (multiplexed) gratings with a relative phase shift of 180° in a photorefractive material, BSO, via a degenerate four wave mixing (DFWM ) configuration. For experimental parameters, such as grating response time and optimised total input intensity. almost complete subtraction is achieved in the phase conjugate output. When motion occurs in the object plane a bright output image is observed depending on the experimental variables of feature size and velocity. We present results for motion detection of features of various dimensions at a range of speeds in both x and y directions and via Fourier plane observation.
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