| 摘要 |
<p>PURPOSE:To avoid complex process and cost rise, and reduce malfunction caused by in-phase inputs by arranging a plurality of light receiving parts and light shielded light-receiving parts at point-symmetric positions. CONSTITUTION:A plurality of light receiving parts 12a, 12b which are not subjected to light shielding, and the same number of light-shielded light receiving parts 13a, 13b as the light receiving parts 12, 12b are arranged at point- symmetric positions. Signals from the light receiving part 12a, 12b are synthesized and delivered to an amplifying circuit 14. On the other hand, signals from the light-shielded light receiving parts 13a, 13b also are similarly synthesized and delivered to the amplifying circuit 14. The respective signals are amplified, compared and output. Noise signal input in a photo detector is divided into four portions by the light receiving parts, and output signals of equal quantity generate on the light receiving parts 12a, 12b and on the light-shielded light receiving parts 13a, 13b, on account of the point-symmetric arrangement. As a result, the signals from the light receiving part 12a, 12b and signals from the light-shielded light receiving parts 13a, 13b are cancelled each other out by the amplifying circuit 14, so that malfunction caused by noise signal does not occur.</p> |
