| 摘要 |
PURPOSE:To attain automatic focusing without causing nonlinear servo operation by using a monitor output signal generated in an optical sensor arranged to receive directly part of the output of a laser light so as to control the operating timing of the servo system with a laser caused by the self-coupling effect. CONSTITUTION:An emitted beam 3 from a laser 2 is collected by an internal objective lens through a deflection mirror 4 and an automatic focus mechanism 5 and the objective lens is moved so that the focus is placed on an optical disk face 6 at all times. In receiving a maximum return light from the light beam reflected from a disk 6 to the laser 2 by a circuit 8 controlling an output signal 7a generated in a light sensor 7 arranged so as to receive the part of the output of the laser light directly, the output level of the output signal 7a of a monitor 7 generated by the self-coupling effect of the laser is detected by the control circuit 8. The signal 9 is fed to a timing signal generating circuit 10 to generate an operation start point timing signal 11 of the servo system to turn on/off the switch 12 thereby using the drive circuit 13 to drive the objective lens.
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