PURPOSE: To judge the position of a gate precisely in a short time by a method wherein an image detection means is installed in the axial direction of a lens and reflected light from the lens is taken into as an image.
CONSTITUTION: A ring illumination 8 is arranged around a lens 1, a slit 9 is formed in a direction perpendicular to the axis of the lens 1 of the illumination 8, and a light irradiation means is formed. The lens 1 is irradiated uniformly with light 16 by the light irradiation means. In addition, a CCD camera 11 which is equipped with a close-up lens 10 is arranged at the upper part of the lens 1, and an image detection means is formed. Then, an image which is taken into by the image detection means is binary-coded by an image processor, a binarized image is compared with a mask pattern which has been computed in advance, and the image, of a flaw along the difference in level of the lens or of an object other than the lens, which is not required to detect a gate is removed. In succession, a linear image is erased, the image in an area within a definite range is judged as a gate on the basis of a residual image, and the position of the gate is found.
YAMAMOTO YUICHI
HIRAYAMA YASUHIRO
KAKEBE TAKESHI
