Development of Non-contact Method for Measuring Shape of Specular Surfaces.

Research Project

Project/Area Number	06650463
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	計測・制御工学
Research Institution	Toyohashi University of Technology
Principal Investigator	MIYAKE Tetsuo Toyohashi University of Technology, Production Systems Engineering, Associate Professor, 工学部, 助教授 (60239366)
Project Period (FY)	1994 – 1995
Project Status	Completed (Fiscal Year 1995)
Budget Amount *help	¥1,500,000 (Direct Cost: ¥1,500,000) Fiscal Year 1995: ¥300,000 (Direct Cost: ¥300,000) Fiscal Year 1994: ¥1,200,000 (Direct Cost: ¥1,200,000)
Keywords	Shape measurement / Active vision / Non-contact / Specular surfaces / 3次元画像計測
Research Abstract	In this research, we developed a new technique for obtaining shape of specular surfaces. To get normal directions over a whole surface of the object, we developed a 5 degrees of freedom vision system. This system has 3 straight moving stages that perpendicularly intersect each other, and 2 rotary tables. A CCD camera is mounted on the one of the tables and a point light source is located on the optical axis of the camera. As the axis can be positionaed at an arbitrary point and oriented in an arbitrary derection, reflected light by the surface emitted from the source can always be detected at the center of the image plane of the camera. On that condition, because the normal direction of the surface coincides with the axis, the information about the shape can be obtained. We made experiments using a flat mirror and a steel ball with radius 75mm. About the mirror, the maximum error between reconstructed shape and an ideal plane was 12mum. The radius of the reconstructed sphere, obtained from the measurements of the ball repeated mine times were scattered between 73.7mm and 75.1mm, and its average value was 74.4mm. On the other land, the average distance between each reconstructed point and the surface of the calculated sphere was 49mum and its standard deviation was 14mum. Judging from the experimental result, the characteristic of the shape as a plane or a sphere is reconstructed correctly. Multiple causes for the error are considered. To improve the inadequate parts of the system and to measure an arbitrary shape ober a wide range is the subject for a future study.