From Event: SPIE Optical Engineering + Applications, 2018
One of the problems of interferometric methods is the difficulty of measuring surface shape with sharp boundaries due to the wavelength-limited dynamic range of the measurement. To circumvent this limitation multiwavelength methods or techniques based on hologram capturing at the different tilt of the illumination beam are applied. In this work we examine the performance of the digital holographic interferometry with multi-inclination illumi- nation in the numerical and real experiments. Lensless implementation of the technique implies the wavefront propagation by numerical algorithms. In this regard the speckle scattering in the Fresnel diffraction area caused by surface roughness and the impact of distance from the object to the registration plane are analyzed. Since shape measurement is based on the calculation of phase difference for the wavefronts recorded with tilt of the object illuminating beam, the requirements to preciseness of measurements of the angle of incidence of this beam are considered. The algorithm of the inclination angle determination are developed. The performance of noise suppression techniques, namely sine-cosine and BM3D methods are considered for high noisy conditions, when the phase distributions are formed by reflecting object with a great roughness and height differences.
Nikolay V. Petrov, Vladislav A. Skobnikov, Igor A. Shevkunov, Andrei V. Belashov, and Alexander V. Fedin, "Features of surface contouring by digital holographic interferometry with tilt of the object illumination," Proc. SPIE 10749, Interferometry XIX, 1074906 (Presented at SPIE Optical Engineering + Applications: August 21, 2018; Published: 18 August 2018); https://doi.org/10.1117/12.2321207.
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