Transformed phase mask and photoanisotropic material in optical correlators applied for security verification

A security verification method using a transform phase mask as an optical mark bonded to a document or some other object is pro- posed. This mask consists of separated and shifted fragments of a ref- erence phase mask. Both masks are entered into an optical correlator as input and reference images. We consider the model of autocorrelation peaks produced and of feature vectors formed in a classical joint trans- form correlator. We propose to use a reversible photoanisotropic mate- rial in the frequency domain of a joint transform correlator. We show that such a material can be used in optical security devices. The joint trans- form correlator experimental setup containing the photoanisotropic ma- terial is designed and the optimum exposures of material to produce autocorrelation peaks are found. © 1999 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(99)01101-0)