Optical information processing apparatus and method using computer generated hologram

Claim 1

A recognition method for recognizing an object by pattern-matching an image of an object with reference images, said method comprising the steps of: (a) preparing in advance computer generated holograms associated with reference images, said preparing step including, for each of the reference images, the steps of (a1) Fourier-transforming a reference image into first reference complex amplitude information thereof, (a2) coordinate-transforming said first reference complex amplitude information using phase information A(wx, wy) for performing a coordinate transformation from a first coordinate system represented by coordinates (x, y) to a second coordinate system represented by coordinates (u, v) which satisfies ∂u/∂y=∂v/∂x, thereby obtaining second reference complex amplitude information, (a3) Fourier-transforming said second reference complex amplitude information into third reference complex amplitude information, (a4) Fourier-transforming information obtained from an absolute value of said third reference complex amplitude information into fourth reference complex amplitude information, and (a5) forming a complex conjugate of said fourth reference complex amplitude, thereby obtaining a computer generated hologram; (b) displaying an image of an object picked up by an image pick-up device on a first spatial light modulator; (c) optically Fourier-transforming said displayed image into first object complex amplitude information; (d) optically coordinate transforming said first object complex amplitude information by superposing said first object complex amplitude information with said phase information A(wx, wy) on a second spatial light modulator, thereby obtaining second object complex amplitude information; (e) optically Fourier-transforming said second object complex amplitude information into third object complex amplitude information; (f) optically Fourier-transforming information obtained from said third object complex amplitude information into fourth object complex amplitude information, (g) superposing said fourth object complex amplitude information and one of said computer generated holograms associated with the reference images on a third spatial light modulator; and (h) detecting the superposed image to determine whether or not the image of an object coincides with the reference image associated with the one of said computer generated holograms.