| Digital holography is a novel holography technique which is based on conventional holography and synthesizes electronics technique, computer technique and image processing techniques. In digital holography, holograms are captured by a CCD camera instead of the conventional photo plates and the recorded wavefronts are then reconstructed by a computer digitally. The digital holography can be conveniently treated in mathematics. It has short exposure time, no wet post-processing, and therefore it can perform real-time acquirement and processing of images.In this thesis, the recording and reconstruction of digital holograms have been studied both theoretically and experimentally. Mathematical representations for three kinds of reconstruction algorithms (Fresnel integral, convolution and Fourier transform) of digital hologram are deduced based on the diffraction theory. Numerical algorithms have been programmed according to the representations of the discrete mathematics and the processes of recording and reconstruction of digital hologram are simulated by computer. According to the spectrum separating condition and the sampling theorem, the range of angle between reference beam to object beam, the maximum size of object which can be recorded by CCD and minimum recording distance in off-axis digital holography have been analyzed in details. The relationship between the recording distance and the resolution of reconstructed image are discussed. Numerical results show that the resolution and space-bandwidth product of reconstructed image are decreased with the increase of the recording distance when the digital holograms are reconstruct by the algorisms of Fresnel integral or Fourier transformation, and have no change when reconstructed by convolution method. Off-axis Fresnel digital holograms and lensless Fourier holograms are recorded experimentally and reconstructed by the three above algorithms. The results of reconstructions are in accordance with theoretical analyses.
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