There is much need for three-dimensional measurements of the specular objects in industrial fields. We have developed a method to measure wetting angle of molten solder, whose surfaces are remarkably specular, for evaluating the solderability of solder materials. This paper presents a method for measuring the angle of the specular surface direction with high accuracy and speed. The method detects the surface direction by the property of specular reflection at the surface using a set of light sources coded by the brightness ratio for high speed measurements. The surface direction at each point is obtained from the geometry of the specular reflection light source which is identified from the ratio of reflection light intensity. The wide dynamic range vision sensor, which we have developed previously, is employed to increase the number of identifiable light sources for accurate direction measurements. The effectiveness of the proposed method was confirmed by applying it to solder wetting angle measurements.
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