Optical security validation using Michelson interferometer

We propose an improved interference-based encoding that is suitable for security validation application. Two random phase masks are designed by a specific iterative phase retrieval algorithm; they serve as the system phase lock and the authentication key. In the validation process, two-beam interference is implemented using the two masks with a classical Michelson interferometer; the phase lock is fixed on one interference arm, and the authentication key is presented on another moveable arm, which can output two recognizable images by moving a certain distance. Without the correct authentication key, the secret image cannot be recognized even knowing the system lock. As a result, the validation result can be simply determined by checking the interference outputs. Numerical simulations are performed to demonstrate the validity and security of the proposed optical validation method. (C) 2015 Optical Society of America