| 摘要 |
<p>PURPOSE:To improve the transfer efficiency of light emitted from a light emitting element by a constitution wherein light emitted from the light emitting element is reflected from the reflecting surface on a concave surface and condensed so that the incident angle on the light receiving surface of a light emitting optical fiber is within the maximum incident angle of the light emitting optical fiber. CONSTITUTION:When a material to be detected 30 is positioned so as to face a projecting surface 18b and a light receiving surface 28a, a photodetector 21 transmits an electric signal. When the material to be detected 30 is not present, the photodetector 21 does not transmit the electric signal. Therefore, the presence or absence and the like of the material to be detected 30 can be positively detected based on the presence or absence of the electric signal from the photodetector 21. A concave reflecting surface 15 is formed so that the incident angle of the light, which is reflected from the concave reflecting surface 15, on a projecting surface 18a of a light emitting optical fiber 18 is within the maximum incident angle of the optical fiber 18. Therefore, the incident light into the light receiving surface 18a of the light emitting optical fiber 18 does not leak to the outside from the side surface of the light emitting optical fiber 18.</p> |
