| 摘要 |
<p>PURPOSE:To enable the detection of displacement of an object in a wide range, by employing a light receiving element with a relatively small light receiving area. CONSTITUTION:This apparatus is equipped with a light receiving element 2a for detection and a light receiving element 2b for monitoring, while an opening plate 3' is arranged with an opening section between a light emitting element 1 and the light receiving element 2a. The light receiving element 2b is arranged at such a position that light from the light emitting element 1 will not be intercepted with the opening plate 3'. When the opening plate 3' having the opening is at the position X1, a luminous flux with the center angle theta1 is incident on the light receiving element 2a. When the opening plate 3' moves to the position X2, the center angle theta2 of the luminous flux incident on the light receiving element 2a will be larger than the center angle theta1. Thus, the photocurrent of the light receiving element 2a changes according to the size of the center angle and the output of the light receiving element 2a is amplified with an operational amplifier. Then, the displacement of the opening plate 3' having the opening can be detected as electrical signal.</p> |
