Non-contact 3D edge profile measurement for die and mould model surface

The purpose of this study is to develop a more efficient measuring method of 3D edge profile with high accuracy for free-form surface including die and mould model shapes. In this paper, we propose a new method of 3D edge profile measurement by means of optical ring image sensor. Optical ring image sensor has more advantages than the others because it detects as not a light spot but a ring image of the reflected light from a target point. We note that the intensity of optical ring image changes in the edge. The differences between the intensities of ring images in the plane and the edge are represented by cross correlation coefficient, which is used as measuring parameter to detect the 3D edge profile of a master model. We propose the two-step measurement for detecting the edge profile, first the edge area for re-measuring which may include the edges extracted by rough measurement, and second the measuring path of the sensor is decided by the shape of edge areas so that it may cross the edges certainly. Finally, we estimate the edge positions, namely the edge profile using the cross correlation coefficients is obtained by fine measurement along the measuring sensor paths.