| 摘要 |
PURPOSE:To make effective corrections of a laser light-emission output by detecting and correcting variation of less than a wobbling frequency of that in laser power current which does not correspond to information on a reflected beam, a focus shift and tracking shift. CONSTITUTION:Variation in power current of semiconductor laser 2 is detected through low-pass filter 13 and then fed back to power supply 1. Low-pass filter 13 allows only a signal of a band lower than both wobblind frequencies for focous control and tracking to pass. Since variation, less than wobbling freqeuncies, of that in laser currant which does not corresponds to information, a shift in focus and that in tracking is corrected, it never becomes hard to detect a signal due to a great fall in signal level and no influence upon the detection of a focus signal and tracking signal is exerted, so that a laser light-emission output can effectively be corrected. |
