The gloss of a metal surface is an important aspect for product quality evaluation. In general, gloss is influenced by specular reflection of light on a metal surface. Therefore, evaluating the specular reflection is almost the same as evaluating the gloss. We propose a method that uses patterned area illumination to evaluate specular reflection. In specular reflection, the angle of incidence equals the angle of reflection. Consequently, when light (ray) of the area illumination, which has a striped pattern, are projected on a glossy metal surface, a striped pattern forms on the reflected image as a mirror-like reflection, and the sharpness of the striped pattern of the image provides information about the specular reflection on the surface. This characteristic is applied to a metal with a hairline surface finish. A hairline surface presents different glossiness at different viewpoints. When the direction of the striped pattern of illumination is changed, the sharpness of striped pattern on the reflected image varies owing to the surface roughness of the hairline finish. Therefore, we can evaluate the glossiness in various directions by rotating the pattern. The rough relationships between gloss evaluation value and surface roughness were indicated in our study. In order to make the relationship between gloss evaluation and surface roughness for the estimation of surface roughness, we had tried the comparison for the gloss evaluation value and the surface roughness. The more precise relationship for seven directions on hairline-finished metal surface was measured. This report describes the results and considers the possibility of estimation of surface roughness by the gloss evaluation value.
The authors have newly proposed and constructed an active free space optics transmission system. It is equipped with a motor driven laser emitting mechanism and positioning photodiodes, and it transmits a collimated thin laser beam and accurately steers the laser beam direction. It is necessary to introduce the laser beam within sensible range of the receiver in advance of laser beam tracking control. This paper studies an estimation method of laser reaching point for initial laser beam alignment. Distributed photodiodes detect laser luminescence at respective position, and the optical axis of laser beam is analytically presumed based on the Gaussian beam optics. Computer simulation evaluates the accuracy of the proposed estimation methods, and results disclose that the methods help us to guide the laser beam to a distant receiver.
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