| 摘要 |
PROBLEM TO BE SOLVED: To restrain the projection light of an optical fiber from entering the optical fiber again as return light by being reflected partially by a lens or photodetector. SOLUTION: The projection light 1A of the optical fiber 1 is made incident on the lens 2, which converges the projection light 1A on a photodetector 3. The optical axis 11 of projection of the optical fiber 1 and the axis 31 of photodetection of the photodetector 3 are arranged in parallel to each other. The optical axis 11 of projection and the axis 31 of photodetection are arranged opposite a center axis 21, and the optical fiber 1 and photodetector 3 are arranged where the reflected light 3A of the photodetector 3 is not made incident on the lens 2 again, thereby restraining the return light. |
