Abstract

The use of color information in image recognition has important applications in machine vision. Based on the high wavelength selectivity of reflection holograms, holographic filters for multiple wavelengths that can be independently written- in and read-out are proposed for correlation of color images. The correlator can work either in joint-transform correlator form or in VanderLugt filter form. For dynamic operation, a color LCTV can be used as the input spatial light modulator, a piece of photorefractive crystal as the recording medium, and a white light laser with three wavelengths as the coherent light source. The optical system is achromatic and the thickness of the crystal should be less than the focal depth of the Fourier transform lens. Experimental demonstrations and theoretical analysis of the correlator are presented.

© 1989 Optical Society of America