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31 December 2003 Optimized visualization of phase objects with semiderivative real filters
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There is a need for a frequency-domain real filter that visualizes pure-phase objects with thickness either considerably smaller or much bigger than 2π rad and gives output image irradiance proportional to the first derivative of object phase function for a wide range of phase gradients. We propose to construct a nonlinearly graded filter as a combination of Foucault and the square-root filters. The square root filter in frequency plane corresponds to the semiderivative in object space. Between the two half-planes with binary values of amplitude transmittance a segment with nonlinearly varying transmittance is located. Within this intermediate sector the amplitude transmittance is given with a biased antisymmetrical function whose positive and negative frequency branches are proportional to the square-root of spatial frequencies contained therein. Our simulations show that the modified square root filter visualizes both thin and thick pure phase objects with phase gradients from 0.6π up to more than 60π rad/mm.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Arkadiusz Sagan, Marek Kowalczyk, and Tomasz Szoplik "Optimized visualization of phase objects with semiderivative real filters", Proc. SPIE 5182, Wave-Optical Systems Engineering II, (31 December 2003);

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