| 摘要 |
PURPOSE:To bring a focus under stable servocontrol and to perform the quantity of light so that the amplitude of a disk reproducing signal is constant by providing a control circuit for the quantity of light of a light emission part and a gain control circuit for the circuit. CONSTITUTION:When the focus is brought under servocontrol, the light quantity control circuit 8 inputs a fixed value to a driving circuit 7 for a light source 5 to turn on the light source 5, and the gain control circuit 12 for a pickup position control circuit sets the gain of the focus servocontrol to a normal value. If the servocontrol is a failure at this time, the circuit 12 switches the gain of the focus servocontrol and the control is performed; and the circuit 8 starts controlling the quantity of light emission of the light source 5 after the focus is brought under the control so that the amplitude of the reproducing signal is constant. Then, the control over the quantity of light is settled, and then the gain switched by the circuit 12 is returned to the normal value. Consequently, the focus is brought under stable servocontrol and the quantity of light is controlled so that the amplitude of the disk reproducing signal is constant. |
