Recently, there has been considerable interest in the application of combined phase/amplitude encryption to the field of optical pattern recognition based security systems, due to the high level of security that it offers1. We have developed a new phase-only encryption technique based in principle on a phase-coding method which uses a generalization of the Zernike phase contrast technique, but breaks the small-phase-angle limitation of Zernike's method2. This phase-coding technique for image formation, in which the spatial average value of an input phase modulated image is combined with a pre-estimated phase retardation produced by a phase contrast filter, has been demonstrated experimentally3. In this paper we describe an extension of our phase-coding method4 and its application in an experimental system for the decryption and visualization of phase encrypted images using commercially available Parallel-Aligned Liquid Crystal Spatial Light Modulators (PAL-SLM) supplied by Hamamatsu Photonics5.

Date Published: 19 July 1999
PDF: 2 pages
Proc. SPIE 3749, 18th Congress of the International Commission for Optics, (19 July 1999); doi: 10.1117/12.354745

Published in SPIE Proceedings Vol. 3749:
18th Congress of the International Commission for Optics
Alexander J. Glass; Joseph W. Goodman; Milton Chang; Arthur H. Guenther; Toshimitsu Asakura, Editor(s)