| 摘要 |
A light receiving device 12 that receives reflected light condensed by a light receiving condenser means 14 has two first and second electrodes 15, 16 provided on a light receiving surface at prescribed intervals along a baseline that connects a light emitting device 11 with the light receiving device and a resistive region 21 provided between the two electrodes. An electric charge generated at the incident position of light incident on the light receiving surface of the light receiving device 12 becomes a photo current and outputted from the first and second electrodes 15, 16 via the resistive region 21 . The resistance value of the resistive region 21 of the light receiving device 12 is distributed so as to be roughly inversely proportional to a distance from the optical axis of the light receiving condenser means 14 to the incident position of a light spot on the light receiving surface.
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