| 摘要 |
PURPOSE:To record an information signal in an excellent way at the inner and outer circumference of a disk by providing a clocked loop controlled based on a monitor output so as to change the laser luminous quantity accurately independently of temperature. CONSTITUTION:The luminous quantity of a beam 11 of a laser 10 driven by a current from an adder circuit 9 is monitored by a monitor diode 12, the obtained electric signal is amplified by a DC amplifier 13 and fed to a differential amplifier 7. The amplifier 7 outputs a signal having a level in response to the level difference of both output signals of a DA amplifier and the amplifier 13, supplies the signal to the laser 10 through the adder circuit 9 to control the DC component of the luminous quantity of the beam 11. On the other hand, the luminous quantity is controlled so that the beam 11 is increased in response to the level of the output DC signal of the DA converter 5 in terms of AC as the beam 11 moves toward the outer circumferential direction of the disk 1, the luminous quantity is changed accurately without being affected by temperature and an information signal is recorded excellently. |
