3 October 2001 Applications of Fresnel diffraction from phase objects
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It is shown that when a part of a wave-front bears a sharp change in its phase, the Fresnel diffraction becomes noticeable. To change the phase sharply, one can reflect the wave-front from a step or transmit it through a transparent medium having a sharp change in its thickness or refractive index. The visibility of the corresponding diffraction fringes depends on the amount of phase change and can be varied from zero to one. Since the phase change can be accomplished by various means, the effect renders to measure phase change, refractive index change, displacement, and so on. Here, the change of visibility is the measurement criterion, therefore the fluctuations of the source intensity do not affect the measurement precision. In this paper Fresnel diffraction from one dimensional step, circular step, and single strip are studied, and some of its applications are briefly discussed.
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Mohammad Taghi Tavassoly, Mohammad Taghi Tavassoly, Ahmad Darudi, Ahmad Darudi, Hamid Reza Khalesifard, Hamid Reza Khalesifard, Seyed Mohammad Reza Sadat Hosseini, Seyed Mohammad Reza Sadat Hosseini, } "Applications of Fresnel diffraction from phase objects", Proc. SPIE 4399, Optical Measurement Systems for Industrial Inspection II: Applications in Production Engineering, (3 October 2001); doi: 10.1117/12.445579; https://doi.org/10.1117/12.445579

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