| 摘要 |
PURPOSE:To control a laser output to a prescribed value without receiving the influence of a returning light by taking out one part of two beams, whose wavelength is different, to be outgoing from a semiconductor laser, photo- detecting only one beam through a filter and controlling the output of the laser. CONSTITUTION:Two beams 21 and 22, whose wavelength is different, are outgoing forward from a semiconductor laser 1 and the beams 21 and 22 are inputted to a collimator lens 6 and caused to be parallel lights. Then, the beams are separated into a beam to be reflected by a splitter 7 and to go to an optical disk 9 and a beam to transmit through the splitter 7. Out of the two beams which transmit through the splitter 7, only the light of the low output beam is transmitted through a color filter 11 and only the beam of the low output is photo-detected by a photo-detecting element 12. A control part 13 compares the output of the photo-detecting element 12 with a reference value and a current to be proportional with an error signal flows to the laser 1. Thus, the light emitting power of the laser 1 can be controlled to the prescribed value. |
