Encryption of volume holograms using complementary input images and a binary key

Technical Group members are being offered the option of receiving the Optics in Information Systems Newsletter electronically. An e-mail is being sent to all group members with the web location for this issue, and asking members to choose between the electronic and printed version for future issues. If you are a member and have not yet received this message, then SPIE does not have your correct e-mail address. To receive future issues electronically , please send your e-mail address to: [email protected] with the word OIS in the subject line of the message and the words electronic version in the body of the message. If you prefer to receive the newsletter in the printed format, but want to send your correct e-mail address for our database, include the words print version preferred in the body of your message. While most common implementations of cryptographic techniques are performed via electronic or computer-based algorithms , using parallel optical processing provides ciphered information with extremely-fast decryption speeds. To date, most of the proposed optical cryptographic methods have used classical macro-optical systems. Miniaturizing the optical components allows us to move towards systems that are more realistic for genuine application and potentially enables us to directly interface to microelectronic devices. We have demonstrated the miniaturization of the generalized phase-contrast (GPC) method 1-3 in a pla-nar-integrated micro-optics (PO) platform. 4-6 Implementing optical processes in this way allows coupled light to undergo free-space propagation between integrated micro-optical components. The GPC-PO device is therefore particularly robust and not prone to position tolerances and alignment problems: major issues when using discrete and macro-optical components. In the miniaturized setup, the GPC-based visu-alization of the decrypted pattern is achieved in a folded optical path configuration using the device shown in Figure 1. The mi-cro-lenses of the 4-f lens setup and the phase contrast filter (PCF) at the Fourier plane are integrated into a single optical flat. First, m u l t i p l e-p h a s e-l e v e l diffractive micro-optical elements are fabricated on the top side of a glass substrate using multi-mask lithography. The micro-lenses are then reflection-coated and fabricated using two binary lithographic steps that make up a four-phase-level diffractive optical element. The first micro-lens focuses the beam onto the Fourier plane where the reflection-coated circular PCF is positioned to introduce a π phase shift to the on-axis region of the focused light. The PCF …