| 摘要 |
<p>In the device disclosed, a light source (14) emits light (15) parallel to the plane of the object. The light (15) skims, or is slightly shaded in cross-section by, the surface of the object, and is incident on an optoelectric sensor (16). The light source (14) produces a light beam (15) of elliptical or circular cross-section. The sensor (16) is divided into two parts, one region (33) of which is closer to the surface of the object in the direction of the normal (41) and the other region of which (32) is farther from the surface in the direction of the normal (41). The region nearer the surface serves as a sensing region (33) and the region farther from the surface serves as a reference region (32) of the sensor (16). Both regions (32, 33) measure the intensity of the respective incident light beam (15).</p> |
