| 摘要 |
PURPOSE:To rise the power of a semiconductor laser from the reproducing power to the recording power in high speed, by stabilizing the reproducing power through power control at the time of reproduction and by overlapping the recording electric current on the reproducing electric current just before the recording at the time of recording. CONSTITUTION:When a signal is to be reproduced, gate circuits 2 and 7 are closed and gate circuits 3 and 8 are opened. The optical output of a semiconductor laser 1 is monitored by a photodetector 12 and a laser driving electric current I1 is controlled by a power controlling circuit 11 thus, the power control is performed. When a signal is to be recorded, the gate 8 is closed and the gate 7 is opened. When the signal to be recorded is in the section ''1'', the gate 2 is closed and the gate 3 is opened and an electric current I1+I2 flows to the laser 1, and, when the signal is in the section ''0'', the gate 3 is closed and the gate 2 is opened and an electric current I3 flows to the semiconductor laser 1. When the electric currents I1, I2, and I3 are set so as to satify the following formule: I1+I2>I3 and I1 I2, a laser beam having a power which is necessary for recording is irradiated upon the disk only when the signal to be recorded is in the section ''1'', and, therefore, recordings by 1- and 0-bit are realized. |
