| 摘要 |
PURPOSE:To obtain the stable output of a semiconductor laser by a method wherein a decision circuit to output a current correcting signal according to the time at the off time of the semiconductor laser and a current correcting circuit to apply correction to a driving current on the basis of this current correcting signal are provided. CONSTITUTION:A decision circuit 10 times a time (tau) between a time when a video signal is turned off and a time when the following video signal arrives and when the time (tau) is shorter than the set time (to), a current correcting signal of 'L' is outputted and when the time (tau) is longer than the set time (to), a current correcting signal of 'H' is outputted. Now, when the currernt correcting signal of 'H' is outputted from the decision circuit 10, a driving current corrected by a current correcting circuit 9 flows to an LD 1. Thereby, the value of the driving current to be outputted from the current correcting circuit 9 is set in such a way that the amount of light of the LD 1 is held at a value in the vicinity of a Vref. As a result, the output fluctuation due to the heat characteristic of a semiconductor laser is eliminated and the output of the semiconductor laser can be stabilized. |
