| 摘要 |
PURPOSE:To deal with even the low output area of output characteristics of a semiconductor laser which has polygonal characteristics by switching and controlling of the by-pass current of a semiconductor laser driving circuit. CONSTITUTION:When the output current Io of a light quantity detector 3 corresponding to a polygonal point becomes equal to the total output current Ipd of the light quantity detector 3, a converted voltage generated by a resistance 7 is applied to an input of a comparing circuit 8 at any time so that it attains to a threshold value Ew. Therefore, when the output of the comparing circuit 8 is '0' while the converted voltage of the resistance 7 is below the threshold value Ew, a multiplexer 93 is triggered with the signal '0' and switched to the side of a low-current attenuator 91. Similarly, when the converted voltage of the resistance 7 is below the threshold value Ew. The output of the comparing circuit 8 is '1' and the multiplexer 93 is triggered to the side of a high- current attenuator 92. Consequently, the light output of the semiconductor laser during reproduction is made constant and a desired light output for recording is obtained over the entire light output range. |
