Watermarking of reconstructed wavefronts

Abstract

A technique for digital watermarking of object wavefronts in conjunction with a multiple plane phase retrieval technique is proposed. Digital watermarking of wavefronts obtained via digital holography is initially reviewed. In the holographic technique, the watermark is encrypted by double random-phase encoding and superimposed with a single host hologram. The host object wavefront is reconstructed numerically and the watermark is then recovered using double random-phase decoding of the watermarked host pattern. In the proposed watermarking-phase retrieval technique, the host object wavefront is plotted at axially-displaced planes. The watermark function is propagated and superimposed with the corresponding host wavefront. The host object wavefront is reconstructed using the conventional iterative phase retrieval method and the watermark is finally recovered by double random-phase decoding. The advantage of the multiple plane encoding process is the enhanced security of the watermark.