| 摘要 |
<p>In the inspection of cylindrical objects, particularly O-rings, the object (2) is translated through a field of view and a linear light trace (6) is projected on its surface. An image of the light trace is projected on a mask, which has a size and shape corresponding to the size and shape which the image would have if the surface of the object were perfect. If there is a defect, light will pass the mask and be sensed by a detector positioned behind the mask. Preferably, two masks (14, 16) and associated detectors (18, 20) are used, one mask being convex, to pass light when the light trace falls on a projection from the surface and the other concave, to pass light when the light trace falls on a depression in the surface. The light trace may be either dynamic, formed by a scanned laser beam (7), or static, formed by such a beam focussed by a cylindrical lens. Means are provided to automatically keep the illuminating and receiving systems properly aligned.</p> |
