| 摘要 |
PURPOSE:To eliminate the noises included in a laser output within a signal band of an optical disk, by providing a series resonance circuit having a resonance frequency within a signal band of the optical disk in parallel to a semiconductor laser element which is driven with a fixed level of optical output. CONSTITUTION:An LCR series resonance circuit 14 which functions as a noise filter circuit is set in parallel to a semiconductor laser 11 which is driven by a constant optical output driving circuit 13. Then the resonance frequency fO is set at the center frequency of the signal band of an optical disk. The impedance of the filter circuit 14 is sufficiently reduced with the frequency fO, and therefore both ends of the laser 11 are short-circuited. As a result, the component near the frequency fO is quickly reduced and elminated among the noise type optical output fluctuations due to the light returned from the optical disk. |
