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A detailed investigation has been made of the unusual characteristics of the angular distribution of surface scattering from velvet in the visual region. We present a novel method in which samples of velvet fabric are wrapped around a right-circular cylinder so that reemitted radiance can be measured by a digital CCD camera. This setup makes it relatively simple to acquire a large set of bidirectional reflection distribution function (BRDF) samples. The study reveals that, apart from the grazing specular lobe and an anisotropic backscattering peak near 50 degrees , the overall BRDF's are rather uniform across the whole angular span of observation. Attempts are made to relate these scattering characteristics to the physical and the geometrical structure of velvet.

Surface speckle pattern intensity distribution resulting from laser light scattering from a rough surface contains various information about the surface geometrical and physical properties. A surface roughness measurement technique based on the texture analysis of surface speckle pattern texture images is put forward. In the surface roughness measurement technique, the speckle pattern texture images are taken by a simple setup configuration consisting of a laser and a CCD camera. Our experimental results show that the surface roughness contained in the surface speckle pattern texture images has a good monotonic relationship with their energy feature of the gray-level co-occurrence matrices. After the measurement system is calibrated by a standard surface roughness specimen, the surface roughness of the object surface composed of the same material and machined by the same method as the standard specimen surface can be evaluated from a single speckle pattern texture image. The robustness of the characterization of speckle pattern texture for surface roughness is also discussed. Thus the surface roughness measurement technique can be used for an in-process surface measurement.

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