Proceedings PaperSignal processing for reduction of speckle noise in light-stripe systems
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Nontactile range sensors based on the lightstripe triangulation method are now widely accepted in production and quality control due to their speed and accuracy. However, some problems show up when extracting contour data due to the speckles induced by coherent lighting. Analyses have shown that the nature of this error is Gaussian, regardless of the nearly multiplicative nature of the speckle noise in the image data itself. Proceeding on this assumption, several approaches to eliminate this error and increase the subjective image quality will be shown in this paper. From a simple FIR-filter with a reectangular pulse response over a better adapted Gaussian pulse response FIR to finally a logarithmic-Gaussian FIR that takes the multiplicative nature of the noise into account, visual results and error reduction are discussed. The additional memory and processing power requirements are minimal since the pulse response of the filters is quite short and the logarithmic/exponential calculations can be performed on a look-up-table basis.