Abstract

Classical optical correlators are known to be very sensitive to distortions, such as scaling and rotation. Various invariant systems have been studied and reported based on the conventional spatial filtering technique. In this paper, we have investigated the feasibility of implementing an invariant system based on optical joint transform architecture. A polar-log coordinate transformation is used as the technique to retain scaling and rotation invariances. This transformation is achieved through the Fourier transform of a universal mask from a computer generated hologram and the power spectra of input objects. An energy compensating process is employed to accommodate size variations from input objects and the nonlinear weight factor caused by the coordinate transform mask. The dynamic range of the proposed system is evaluated and compared with those obtained from conventional approaches. A method of preserving shift in variance and the phase information of input objects in the system has also been studied and suggested. Results verifying the proposed system are presented.

© 1992 Optical Society of America