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Improvement of topography measurement using denoising approach in Fourier digital holographic microscopy

This paper proposes an improvement of the measurement method of focusing high gradient microobjects of small and large radius of curvature. The measurement process is carried out in a Fourier digital holographic microscope with spherical illumination, which ensures maximum usage of numerical aperture of the optical system. The interference pattern is the result of interference between the deformed, quasi-spherical object and spherical reference waves. The noise influence on the phase measurement is analyzed and minimized with block-matching 3-D (BM3D) filtering method. The accurate shape reconstruction of the object and localization of the imaging reference plane are provided by (1) the aberration compensation procedure, and (2) the calibration procedure. To obtain the final shape, the Local Ray Approximation approach is used. In this work an effective BM3D method was applied in the process of the reconstruction of the object beam, improving accuracy of the measurement method. The validation of our approach is presented for spherical objects of large radius of curvature and high gradient of shape.