Optical Information Processiong Technology In Robust Digital Watermarking

CGH digital watermarking is a new information hiding technique that combined with computer-generated hologram and digital watermarking. The watermark has strong robustness because of non-tear of holograms, etc. It provides new effective means for protect intelligent property, such as image medium, audio medium and video medium, etc. We study the new approach of digital watermarking using CGH based on information optics theory, which in order to acquire a good project and higher robustness than the international typical method.We study the approach of image information hiding based on CGH of phase-only interference holography. The importance of phase in the transformation is analyzed. Instead of the complex amplitude of the traditional Fourier-transformed object wave, the phase-only wave is used to interfere with the reference wave, and a high contrast Fourier-transformed CGH is obtained. Hologram is embedded into host image by discrete-cosine-transform algorithm and encrypted by the security key. The original information is retrieved by reconstruction of optics or computer-generated hologram with the security key. Theoretical analysis and simulation experiments show that the algorithm has more robustness to image lossy compression, cropping and filtering, comparing with the algorithm based on general computer-generated hologram.In the next part of the dissertation, a new approach of digital watermarking based on phase retrieval algorithm and computer-generated hologram is proposed. The watermarking image is transformed into virtual object wave after phase retrieval algorithm. Then use the virtual object wave take the place of traditional Fourier- transformed object wave. It interfered with the reference wave to form Fourier- transformed computer-generated hologram and the contrast is 100% in theory. Theoretical analysis and numerical experiments show that the algorithm has more robustness and practical value. We proposed a new approach of Fourier CGH digital watermarking with nonlinear amplitude limiting based on information optics,which realizes better robustness. The amplitude and phase are extracted on the basis of traditional Fourier transform holography. Binary Fourier hologram was formed by nonlinear amplitude limiting algorithm when the phase information as input function and the amplitude information transferred into a bias function. Because the binary hologram has stronger anti-interference property than the normal hologram, the digital watermarking obtains much better robustness. To improve the watermark's resistance to compression, hologram is embedded in the frequency domain through discrete cosine transform. Theoretical analysis and numerical experiments show that the algorithm has more robustness under the situation that reduce initial watermark accuracy within limits, comparing with the algorithm based on traditional Fourier CGH watermarking.A new approach of information hiding technology based on phase retrieval algorithm and nonlinear amplitude limiting is proposed. The secret information is encoded into a pure phase by phase retrieval algorithm, and using parallel wave as the carrier. Then we obtain binary hologram by nonlinear amplitude limiting model. The theoretical derivation formula is given. The hologram contains more original image information than the hologram getting from average nonlinear amplitude limiting model and improves the diffraction efficiency when reconstruction, and which greatly improves the robustness of the technology. Hologram is encrypted by security key and embedded into host image in the frequency domain by the basic principles of JPEG and bipolar quantization algorithm. Information extraction does not require the participation of original image. It can be extracted with the security key and the secret information is retrieved by digital reconstruction. Theoretical analysis and experiments on standard test images show that the algorithm has more robustness and practical value to a variety of image processing operations comparing with the algorithm based on general digital holography.A new approach of audio watermarking by use of phase retrieval algorithm and computer-generated hologram is proposed. The watermarking image is transformed into virtual object wave after phase retrieval algorithm. It interferes with the reference wave to form high contrast Fourier-transformed CGH. And the hologram is embedded into audio signal by quantification process and discrete-cosine-transform .The watermark can be extracted without the original audio signal and the security key provides a good security. Numerical experiments show that the algorithm is robust against common signal manipulations and attacks, such as lossy compression, re-sampling, low pass filter, noise, and so on.