Research On The Quality Of Reconstructed Image Of Digital Holography

Digital holography is created by the combination of optical holography, photo-electronic imaging technique and computer technique. In digital holography, the recording and reconstruction theory of traditional optical holography is followed, the holograms are directly recorded on the CCD instead of the traditional holographic plate, optical reconstruction is replaced by computer digital reconstruction. The holographic full process including recording, storage, processing, reconstruction and analysis is entirely digital, so new method is added to the application and development of holography. In many small aperture 3-D measuring field, such as 3-D profilometry, deformation measurement, micro-stress measurement, particle field monitoring, cell viewing, micro-circuit examination etc, digital holography can develop its advantages and achieve applications.At the present stage, under the limit of the performance and technological level of CCD, studying the methods of eliminating the zero-order diffraction and conjugate images and improving the resolution and signal-to-noise ratio of the reconstructed image are the critical and burning problems. The research on these subjects will promote development of the information optics theory.In this paper, on the basis of an overview of the historical development and fundamental principle of holography, the development situation and related technique are briefly introduced. The recording and reconstruction theory of digital holography is introduced in detail, the mathematic model of the theory is also built. The conditions of digital hologram recording and reconstructed images separating, the factors that influence the resolution of reconstructed images are analyzed particularly.Based on theoretic analysis, computer simulation and optical experiment, this paper focus on the following aspects mostly:(1) The digital image processing methods such as spatial differential operator processing, spectrum filtering, mean value of hologram subtraction and reference and object beams value subtraction are introduced. Then prove and compare their efforts on filtering the zero-order diffraction and conjugate images.(2) By means of the research on the recording condition of digital holography, the main factors that influence the resolution of reconstructed images are definite. Begin with these factors, synthetic aperture digital holography based on image matching technology has been proposed. The experimental results prove that synthetic aperture technology is an effective means to overcome the problem of CCD, it is not only able to record large-sized objects, but also can significantly improve the resolution of the reconstructed digital holographic images.