Digital hologram watermarking by embedding Fresnel-diffracted watermark data

Since holograms are very costly content, security against holograms is very important. Hologram watermarking has been researched for a long time as a security solution for the digital hologram distributed on the network as the hologram is digitized. We deal with a digital watermarking for digital hologram contents as ownership protection tool. Since holograms have different optical characteristics from natural images, a watermarking technique using these characteristics should be needed. We therefore selected Fresnel diffraction for this property. Both of the host holograms and the watermarks are diffracted more than once for each. The results are refracted to concentrate the diffracted data into the localized regions of the transformed plane so that the region occupied one region among them. From this process, we change and select the region of the watermark. We experimented our scheme with various test images for various attacks on data-manipulating attack and geometric attack. It is apparently recognizable for eye inspection. From the results, we expect the proposed watermarking scheme to be an appropriate solution for protecting the ownership of holograms.