ALL-OPTICAL SUBTRACTED JOINT TRANSFORM CORRELATOR WITH A HOLOGRAPHIC INTERFEROMETER

A new, to our knowledge, subtracted joint transform correlator (SJTC) is proposed that has no digital processing in a computer. All processi ng for obtaining correlation signals between an object and multiple re ference patterns were treated optically by use of a joint transform co rrelator with a holographic interferometer similar to the Mach-Zehnder one. The joint power spectrum of the reference patterns was subtracte d from that of the input image (the object pattern plus the reference patterns), and the spurious correlation signals between the different reference patterns were removed. Because of the optical parallel compu tations of the Fourier spectra and the subtraction, the real-time SJTC is possible to achieve by use of only an optical system. An experimen tal arrangement of the system and system performances of the shift-inv ariant characteristics and discriminability are described. The results show the good performance of this system. (C) 1997 Optical Society of America.