Development of Simultaneous Measurement of 3-D Shapes and Normal Vectors for Specular Objects
Saburo Okada, Masaaki Imade and Hidekazu Miyauchi
Chugoku National Industrial Research Institute, 2-2-2, Hiro-Suehiro, Kure, Hiroshima, 737-0197 Japan
Our research institute developed and built an experimental optical measurement system for specular objects able to simultaneously measure 3-D shapes and normal vectors of surfaces to measure shapes of objects with mirror-finished surfaces and to restore original shapes accurately by inputting measured values in CG and CAD systems. A semiconductor laser spotlight is irradiated on the measured surface vertically or obliquely. Space coordinates of rays reflected on the surface are instantaneously measured at 2 different points in space using optical position sensors rotating at a constant speed. The 3-D coordinates and normal vectors of the reflection point are obtained geometrically. A performance evaluation using a metallic semisphere with a mirror-finished surface showed that the system simultaneously measured 3-D displacement and normal vectors of specular curved surfaces of any angles up to 20 degrees, with maximum error of several degrees in normal vectors and several millimeters in surface shape. The developed system may restore higher quality curved surfaces than conventionally because it reconstitutes curved surfaces using both measured 3-D shape data and normal vector data.
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