| 摘要 |
PURPOSE:To obtain a focusing error signal detecting device in which a few amount of fluctuation of a gain due to the dispersion of a modulation factor of a disk, etc., and a small amount of servo noise are generated, by eliminating the frequency component of an information signal by a detection circuit. CONSTITUTION:The output of a quarter optical detector 1 is current-voltage- converted by an operational amplifier 2 and a resistor 4, and an operational amplifier 3 and a resistor 5. And an envelope corresponding to the bright level of each optical detector output by the detection circuit whose time constant at the time of detecting is decided by an ideal diode 8, a resistor 10, and a capacitor 12, and the detection circuit whose time constant at the time of detecting is decided by an ideal diode 9, a resistor 11, and a capacitor 13. And it is subtracted at a subtractor 6, and gain adjustment is applied by a variable resistor 7, then, a focusing signal is outputted. In such a way, it is possible to obtain the error signal detector in which a few amount of leakage of the frequency component of the information signal, and a few amount of fluctuation of the gain due to the dispersion of the modulation factor of the disk, etc., and a small amount of servo noise are generated.
|
