| 摘要 |
PROBLEM TO BE SOLVED: To simplify the positioning work of a photodetector and an optical fiber and to optically couple them with inexpensive constitution by totally reflecting light made incident on the inside of a spherical lens from the tip surface of the optical fiber and making it incident on the light receiving surface of the photodetector. SOLUTION: The tip surface of the optical fiber 2 and the light receiving surface 5 of the photodetector 4 are brought into contact with the surface of the spherical lens 3, and the light made incident on the inside of the lens 3 from the tip surface of the optical fiber 2 is totally reflected to be made incident on the light receiving surface 5 of the photodetector 4. In order to totally reflect the light made incident on the lens 3 inside the lens 3, the angleθ1 of the tip surface of the optical fiber 2 is set to satisfyθ1 <=90 deg. - 'the total reflection angle inside the lens 3'. In order not to restore the light repeatedly totally reflected inside the lens 3 to an incident surface, an incident angle must be set to that the locus of the repeatedly totally reflected light may not be a regular polygon.
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