Fourier-Transformed Digital Holography And Its Application In Information Hiding

Fourier-transformed digital holography is a digital holography that uses the Fourier transformation characteristics of lens, a charge coupled device (CCD) camera for hologram recording and a numerical method for hologram reconstruction. It is a new imaging technique that combines optical holography, computer technology, electronic technology and digital image processing techniques.This paper presents the concept and underlying theory of Fourier-transformed digital holography, its experiment and its applications in information hiding.(1) Basic recording and reconstruction theory of Fourier-transformed digital holography is described. The reconstruction algorithms of Fourier-transformed digital holography and Fresnel-transformed digital holography are compared.(2) The experiment is designed. The results of the experiment are recorded. The digital image processing techniques are used to remove the zero-order diffraction, the conjugate image and the noise. Due to the intensive light at the focal plane, defocusing technique is used to improve the recording condition. Different digital holograms of different defocus distances are recorded. Corresponding similarity ratio and peak signal-to-noise ratio are calculated. The optimal defocus distance is acquired according to the maximum similarity ratio and peak signal-to-noise ratio under the condition of this experiment. The object size increases properly. The reconstruction image can still be acquired, although the quality of the image is degraded.(3) Based on the characteristics of the holography, its application in information hiding is researched. A blind audio watermark embedding algorithm by a holographic technique is proposed. The process of constructing and reconstructing a digital hologram are described on the basis of the theory of Fourier optics and simulated by the computer. The watermark, in the form of Fourier-transformed digital hologram, is embedded into the audio signal by quantification process. Experimental results show that the...