INCOHERENT OPTICAL CORRELATORS AND PHASE-ENCODING OF IDENTIFICATION CODES FOR ACCESS-CONTROL OR AUTHENTICATION

We show how phase-only filters can be used in incoherent optical corre lators for security applications such as access control, identificatio n, or authentication. As a specific example, a biometric signature, a fingerprint, ii; encoded in a phase-only representation. The phase enc oding is accomplished with the method of generalized projections onto constraint sets implemented by an iterated Fourier transform algorithm . The operation of an incoherent optical security system using both a phase-only filter generated with the generalized projections algorithm and a phase-only matched filter is simulated. The results demonstrate that the selected access pattern was accepted while a false pattern w as rejected by the security system and that better recognition and dis crimination performance was attained with the phase-only filter produc ed by the generalized projections algorithm. (C) 1997 society of Photo -Optical Instrumentation Engineers.