| 摘要 |
PURPOSE:To ensure a wide-range detection for the subject to be detected, by forming the center part of the condensing optical element such as a convex lens or concave mirror and producing two or more focuses. CONSTITUTION:If the subject 8 to be detected shifts from A to B, the subject 8 is within the irradiating range l1 of the light given from the light emitting element 31 and at the position A. Thus the photodetector 5 receives the reflected light of the element 31. Then the subject 8 is at the overlap position of the irradiating ranges of the light emitting elements 31 and 32, and accordingly the photodetector 5 receives the reflected light of the elements 31 and 32 each. And the photodetector 5 receives the reflected light of the element 32 when the subject 8 is at the position B. Accordingly, the photodetector 5 receives successively the ranges l1, l1 and then l2 and l2 to identify the reflected light. Thus the shift of the subject 8 is decided. In such way, a detection is possible over a wide range. |
