| 摘要 |
PURPOSE:To obtain a follow-up controlling device which is so stable that a servo system can work completely, by giving the synchronous wave detection to the frequency component correlated with the position deviation period between a follow- up part and a part to be followed up and then eliminating the frequency component through a filter. CONSTITUTION:When the information track of an optical disk 7 is followed up by a spot condensed through a condenser lens 3, the reflected light polarized by a half mirror 4 is converted into an electric signal by a photodetector 8 to be applied to a tracking signal generating circuit 20. The circuit 20 produces a signal of wobbling frequency fw through an oscillator 18 to give a minute vibration to a wobbler 5 and at the same time applies the tracking signal to a tracking mirror 6 to control the angle of rotation. The signal f2 of the oscillator 18 is supplied to a phase comparator 11 via a phase shifter 17 to be compared with the signal given from the photodetector 8 in terms of the phase. The comparator 11 detects the signals of frequencies fw and 2fw correlated with the position deviation period between the condenser spot and the information track. These signals are eliminated through a notch filter 50 and supplied to the mirror 6 to ensure a stable servo operation. |
