Systematic errors of an optical encryption system due to the discrete values of a spatial light modulator

John T. Sheridan, MEMBER SPIE University College, Dublin College of Engineering, Mathematics and Physical Sciences School of Electrical, Electronic and Mechanical Engineering and Optoelectronic Research Centre and SFI-Strategic Research Cluster in Solar Energy Conversion Belfield, Dublin 4, Ireland E-mail: [email protected] Abstract. An optical implementation of the amplitude encoded double random phase encryption/decryption technique is implemented, and both numerical and experimental results are presented. In particular, we examine the effect of quantization in the decryption process due to the discrete values and quantized levels, which a spatial light modulator SLM can physically display. To do this, we characterize a transmissive SLM using Jones matrices and then map a complex image to the physically achievable levels of the SLM using the pseudorandom encoding technique. We present both numerical and experimental results that quantify the performance of the system. © 2009 Society of Photo-Optical Instrumentation Engineers. DOI: 10.1117/1.3076208