| 摘要 |
PURPOSE:To detect the position of an object correctly regardless of its surface condition by arranging in dispersion a plural pair of a light emitting element and a light receiving element opposite each other across the object around and centrally of the object. CONSTITUTION:A plural pair of a light emitting element 14 and a light receiving element 15 is arranged across a portion 13 to detect of an object 11 like wafer. The light from a light emitting element group 31 is reflected or scattered by the portion 13 to detect, and its average strength is detected by a light receiving element group 32. A position whereat the strength is maximized does not depend on the surface condition of the portion 13. Thus the position of the portion 13 to detect can correctly be detected. |
