| 摘要 |
PURPOSE:To limit incident light and to improve detection accuracy by forming the internal wall surface of the gap of at least either of slit apertures provided in front of a light emitting element and a light receiving element slantingly to the optical axis. CONSTITUTION:An enclosure 1 is a case molded out of opaque resin and the light emitting element 2 and light receiving elements 3 are put in this enclosure 1 opposite each other. The wall surface in the gap of the aperture 4 in front of the light emitting element is formed in parallel to the optical axis and the internal wall surface of the gap of the opening part 5 in front of the light receiving element is at 45 deg. to the optical axis. Light from the light emitting element is stopped down by the aperture 5 in front of the light receiving element, so the detection accuracy is improved.
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