| 摘要 |
PURPOSE:To prevent the incidence of a return beam to a light source from a photodetector for detecting light quantity and to prevent the incidence of a light beam to the side end surface of the photodetector. CONSTITUTION:A focus lens 5 and a photodiode 7 are set on the beam waist positions of the beams 3a, 3b respectively. Further, the photodiode 7 is arranged so that whose light receiving surface is inclined in a direction perpendicular to the beam direction of the beam 3b for detecting light quantity, and this device is adjusted so that a reflected beam 3c from the light receiving surface of the beam 3b for detecting light quantity is not incident on a semiconductor laser light source 1 again. Further, this device is adjusted so that a part of the light receiving surface of the photodiode 7 is off from the beam position of the beam 3b for detecting light quantity. |
