Patent attributes
A deviation amount of a top position of a convex surface of a protruding portion formed on a flat member and a deepest position of a concave surface on the back side of the convex surface, is obtained in XY-coordinates in a plane parallel to an extension plane of the flat member. An annular image obtained by illuminating the concave surface is photographed, and the XY-coordinates of the deepest position of the concave surface are obtained based on the image thus obtained. Regarding the convex surface, the X-coordinate and the Y-coordinate of the top position of the convex surface are respectively obtained by a front camera having an image taking optical axis parallel to the extension plane of the flat member and a side camera having an image taking optical axis parallel to the plane and perpendicular to the image taking optical axis of the front camera, and the deviation amount and deviation direction are obtained based on their respective XY-coordinates obtained.
