| 摘要 |
PURPOSE:To attain detection of deviation without using other sensor by inputting a drive signal of an actuator to an equivalent circuit having equal frequency characteristic as that of the actuator to obtain an electric signal corresponding to the deviation of the actuator. CONSTITUTION:The light beam of a semiconductor 31 is irradiated a recording medium 1 while applying focusing, the returned light is inputted to a photodetector 34, where the signal is converted into an electric signal. The signal is subjected to operation processing b a differential amplifier 41, becomes a track error signal, amplified via a servo amplifier 42, a switch 43 and an actuator drive circuit 44 to activate the actuator 2 and to move an objective lens 33 thereby irradiating the light beam on a prescribed track. The actuator drive signal outputted from the circuit 44 is inputted to an equivalent circuit 5 having an equivalent frequency characteristic as that of the actuator 2 and an electric output corresponding to the deviation of the actuator 2 is generated.
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