| 摘要 |
PURPOSE:To prevent moving force from becoming weak in a high frequency range by raising a voltage applied to a moving means when it is judged from the detection result of a current quantity detecting means that a current quantity is small. CONSTITUTION:When a signal is supplied from a phase compensating circuit 24 to the inverted input terminal of a differential amplifier 35, the differential amplifier 35 applies a voltage corresponding to the supplied voltage value to coils 17a and 17a, so that an objective 14 moves. Then, when the signal supplied from the phase compensating circuit 24 becomes high in frequency owing to the surface waving of an optical disk 1, currents flowing through the coils 17a and 17a decrease in value and the voltage value at a point alpha decreases. The decrease in voltage value is fed back (negatively) to the inverted input terminal of the differential amplifier 35 through a resistance 34. Consequently, the voltage value which is outputted by the differential amplifier 35, i.e. applied to the coils 17a and 17a increases and the frequency characteristic of a driver 25 extends up to a high frequency range, thereby preventing the driving force (moving force) of the objective driving circuit 17 from becoming weak.
|
