| 摘要 |
PROBLEM TO BE SOLVED: To exatly monitor a light beam of a light source without expanding the scale of a device, complicating the assemblage nor being affected by a returned light. SOLUTION: This device comprises a semiconductor laser 11, a signal detecting element 14 and a monitoring photodetector 13, the light beam from the semiconductor laser 11 is converged on a recording medium, a reflected light beam from the recording medium is detected by a signal detecting element 14 and the light beam of the light source is monitored by the monitoring photodetector 13. In this case, the semiconductor laser 11, the signal detecting element 14 and the monitoring photodetector 13 are arranged in a light source unit 20, an element 29, for sending a part of the light beams from the semiconductor laser to the monitoring photodetector 13 in an optical path different from that of the reflected light beam from the recording medium in the optical path from the semiconductor laser to the recording medium, is provided. |
