| 摘要 |
PURPOSE:To efficiently lead a signal light to a photodetector and to detect the signal of good SN ratio by providing a means which intercepts the external light, close around the exit face of a photoconductor which transmits optical information and the detecting face of the photodetector. CONSTITUTION:Optical information is emitted at a prescribed angle from an e it face 1a of a photoconductor 1 to a photodetecting face 2b of a photodetecor 2. A filter 7 is slightly inclined to the optical axis and is arranged to eliminate noise light mixed in the signal light. A light shielding means 8 is provided on th outside of the exit range between the exit face 1a and the detector 2 to intercept the light from the external, and gaps among the phtotoconductor 1, the filter 7, the detector 2, and the light shielding means 8 are closed with a filler 9. Thus, the noise light from the external is cut off to detect the signal light with a good SN ratio.
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