| 摘要 |
PURPOSE:To obtain a wide band ALPC circuit capable of obtaining reproduced signals of low noise and of a high S/N by performing a control by a closed loop to the light output of a semiconductor laser. CONSTITUTION:The output of a light emitting semiconductor 5 is converted to current by a photodetecting means 1 in which a phase rotation is not present in a wide band and converted to voltage by a current to voltage converting means 2 in which the phase rotation is not present based on a command signal. A light quantity error signal is obtained by comparing the voltage with a reference light quantity signal in a subtracter 100. The phase of the light quantity error signal is compensated by a 1st low-pass filter or a phase delaying means 13 consisting of an integrator, further, phases rotated at the consisting elements 1, 2 are invallidated by a phase advancing means 4. Thus, the laser power is always maintained at a prescribed value in the wide band by instructing the increase/decrease of the outputting light of the semiconductor laser 5 with the command signal while making the output of the phase advancing means 4 to be the command signal for the semiconductor laser 5. |
