14 July 2016 Subjective speckle suppression in laser-based stereo photogrammetry
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Optical Engineering, 55(12), 121713 (2016). doi:10.1117/1.OE.55.12.121713
The use of objective speckles as patterns is of high interest for the ongoing development of stereo photogrammetry. The depth of focus of the projected speckle patterns, which can be found to be several meters, can hardly be matched by other projection principles. On the downside, the use of coherent light leads to subjective speckles generated by the rough surface of the object under test. This effect decreases the accuracy under which objects can be reconstructed. We show how laser-based stereo photogrammetry can be adjusted to increase the measurement accuracy of three-dimensional (3-D)-surface measurements while preserving the advantages of speckles projection. Therefore, we present a method to decrease the contrast of subjective speckles in the images by pixel-wise shifting the cameras orthogonally to their viewing direction and back shifting the taken images numerically, accordingly. This leads to an increase in 3-D-reconstruction quality, as seen in a decrease in standard deviation, peak-to-valley value and in an increase in the number of reconstructed points for measured test objects.
© 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)
Andreas W. Stark, Eugene Wong, Daniel Weigel, Holger Babovsky, Thomas Schott, Richard Kowarschik, "Subjective speckle suppression in laser-based stereo photogrammetry," Optical Engineering 55(12), 121713 (14 July 2016). https://doi.org/10.1117/1.OE.55.12.121713

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