| 摘要 |
PURPOSE:To control the intensity level of reflected luminous flux to be always constant by reflecting a laser beam projected from a laser light source from a recording medium, diffracting the beam by a diffraction grating and controlling the intensity of the laser beam based on the intensity level of the reflected luminous flux. CONSTITUTION:The titled device 21 is provided with a collimator lens 23 collimating the light projected from a semiconductor laser 22 of a laser light source, the collimated luminous flux is collected on a recording medium 24, a beam spot is formed to fetch the reflected luminous flux onto an objective lens 25. The fetched reflected luminous flux is diffracted from the diffraction grating 26. On the other hand, the reflected luminous flux diffracted by the grating 26 is received, and converted into an electric signal by a reflected luminous flux intensity detector 27 and a photodetector 28. In response to the output from the detector 27, the intensity of the laser beam projected from the laser light source is controlled by a controller 29. Thus, the intensity level of the reflected luminous flux is made always constant. |
