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Speckle-noise-reduction method of projecting interferometry fringes based on power spectrum density.

The fringe projection technique plays an important role in surface inspection, due to its noncontact, full-field acquisition and high resolution. When using projecting interferometry fringes, one of the basic problems encountered is the speckle noise existing in the fringe pattern. In this paper, a novel method is proposed to reduce the speckle noise based on power spectrum density (PSD) thresholding, which consists of three steps: first, PSD is calculated according to the frequency spectrum obtained by Fourier transform; second, a filter is constructed by a PSD thresholding to filter the frequency content of the speckle noise; and finally inverse Fourier transform is used to obtain the noise-reduction image. Experimental results prove the feasibility and effectiveness of the presented method.