Proceedings PaperImaging Properties Of Random Phase Diffusers For Coherent Imaging Systems
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A number of coherent systems exist for whichillp would be desirable to illuminate an object with a beam of randomly modulated phase. Usually for this purpose we put together the object and random phase diffuser, e.g. ground glass, at its back side. In the case of uniformly illuminated trivial object whose amplitude transmittance equals unity we observe in the image plane intensity fluctuations which correspond to some extent to the random relief of illuminating wavefront. By imaging properties of random phase diffuser we mean statistical propoerties of these fluctuations, especially their average contrast. In this work we consider imaging properties of diffusers which are set in the wide-band imaging system for which ratio, point spread function area divided by autocorrelation area of diffuser complex transmittance, is less than unity. We derive the formulae which describe intensity fluctuation in the image plane in terms of phase distribution and its first and second spatial derivatives in the object plane. Above formulae are derived for the low-pass filtering, particular case of high pass filtering, and for the case of not perfect image focusing. Then we employ these formulae for calculation the average contrast of noise pattern in the image plane when photographically formed strong diffuser with small standard deviation of surface roughness (≈ 0.58λ) is used.