Computer-generated hologram marked by correlated photon imaging.

The computer-generated hologram (CGH) has been studied for many applications. In this paper, CGH is watermarked by correlated photon imaging. An input image is encoded into two cascaded phase-only masks by using the CGH principle. Subsequently, two different marks are independently encoded into one-dimensional (1D) intensity points by using correlated photon imaging (or ghost imaging), and the recorded 1D intensity points are embedded into the extracted phase masks for optical watermarking. During the decoding, the input is recovered by using two watermarked phase masks. To verify copyright of the recovered input image, information embedded in two phase-only masks is retrieved and used to decode the hidden marks. The decoded marks do not visually render clear information due to only a few measurements and, instead, are authenticated. It is illustrated that the quality of the recovered input image is high, and a different imaging approach can be applied in the CGH system for optical watermarking. The proposed approach provides a promising strategy for optical information security.