FOCUS SERVO SETTING DEVICE

PROBLEM TO BE SOLVED: To provide a focus servo setting device capable of stably detecting a focus setting point with a simple structure. SOLUTION: The device is equipped with a focus servo loop which is composed of a gain compensation circuit 104, phase compensation circuit 105, optical pickup 102 and an amplifier 106; a switch SW which opens/closes the focus servo loop; a focus error zero cross detection circuit 108 for outputting a signal SI; an oscillator 107; a peak hold part 109; and a plurality of comparators and attenuators. The switch SW closes the focus servo loop with a timing in which the signal SI is outputted.