| 摘要 |
PURPOSE:To unnecessitate a work with which the output of a light receiving means is made constant by adjusting volumes at the time of an assemblage by providing the light receiving means for monitoring a laser beam in the optical path of the laser beam and providing a light quantity limiting means for limiting the quantity of the laser beam entering to the light receiving means. CONSTITUTION:A laser beam L from a laser light source 11 reflects at the plane 14a of a beam splitter 14 and passes a circular aperture 100 and is received by a front photodetector 15 being a light beam monitoring means. The aperture 100 allows only the center part of the beam of the laser beam L to pass to the front photodetector 15 and the peripheral part of the beam of the laser beam L is cut by the peripheral part of the aperture 100 in an optical system supporting part 42. Thus, in a case that the power of the laser beam L is constant, effects of the beam intensity distribution and the shape of the laser beam L are eliminated and a constant output from the front photodetector 15 can be obtained. |
