A stable servo control method and device for variation of light quantity

The present invention relates to a gain control method and apparatus of the magneto-optical disc servo apparatus for detecting an optical signal. A focus servo control method for a magneto-optical disk, a servo control method for stable to light amount variation according to the present invention performs the focus control and tracking control by using the operation in the optical detection output the focus error signal and a tracking error signal composed of a plurality of photodiodes in a photodiode of at least two photodiodes of the light quantity detection signal is added to a dividing calculation process, the focus error signal for generating a sum signal to the island signal divides the focus error signal generated in the in constituting the optical detector the first for generating the division process, the second dividing process and the division of the focus error signal and the actuator by use of said dividing the tracking error signal for generating the tracking error signal, a tracking error signal is divided into in the island-signal focusing servo and tracking servo Performing is characterized in that it comprises a servo execution. According to the present invention, when in spite of changes in the light intensity value of the optical signal detected by the magnetic disk, and regulates the jungpok diagram of a control system, to control the control device in a stable range, and in particular, in the case where the light quantity value variation is large, there is an effect that it is possible to stabilize the servo control system to prevent oscillation of the servo device.