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Phase object exists widely in nature, such as biological cells, optical components, atmospheric flow field and so on. The
phase detection of objects has great significance in the basic research, nondestructive testing, aerospace, military
weapons and other areas. The usual methods of phase object detection include interference method, grating method,
schlieren method, and phase-contrast method etc. These methods have their own advantages, but they also have some
disadvantages on detecting precision, environmental requirements, cost, detection rate, detection range, detection
linearity in various applications, even the most sophisticated method-phase contrast method mainly used in
microscopic structure, lacks quantitative analysis of the size of the phase of the object and the relationship between the
image contrast and the optical system. In this paper, various phase detection means and the characteristics of different
applications are analyzed based on the optical information processing, and a phase detection system based on optical
filtering is formed. Firstly the frequency spectrum of the phase object is achieved by Fourier transform lens in the
system, then the frequency spectrum is changed reasonably by the filter, at last the image which can represent the phase
distribution through light intensity is achieved by the inverse Fourier transform. The advantages and disadvantages of the
common used filters such as 1/4 wavelength phase filter, high-pass filter and edge filter are analyzed, and their phase
resolution is analyzed in the same optical information processing system, and the factors impacting phase resolution are
pointed out. The paper draws a conclusion that there exists an optimal filter which makes the detect accuracy best for any
application. At last, we discussed how to design an optimal filter through which the ability of the phase testing of optical
information processing system can be improved most.
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