RANDOM-PHASE ENCODING FOR OPTICAL SECURITY

A new optical encoding method for security applications is proposed. T he encoded image (encrypted into the security products) is merely a ra ndom phase image statistically and randomly generated by a random numb er generator using a computer, which contains no information from the reference pattern (stored for verification) or the frequency plane fil ter (a phase-only function for decoding), The phase function in the fr equency plane is obtained using a modified phase retrieval algorithm. The proposed method uses two phase-only functions (images) at both the input and frequency planes of the optical processor leading to maximu m optical efficiency. Computer simulation shows that the proposed meth od is robust for optical security applications. (C) 1996 Society of Ph oto-Optical Instrumentation Engineers.