OPTICAL FOCUS DRIVE ASSEMBLY AND METHOD FOR DETECTING FLUCTUATION IN FOCUS SENSITIVITY

摘要

PROBLEM TO BE SOLVED: To provide a stable focus controller which decreases the fluctuations in focus control by the fluctuations in the sensitivity of an error signal and to manufacture a stable pickup free of the fluctuations in the sensitivity by providing a method for detecting the fluctuations in the sensitivity of the error signal of the pickup to be used. SOLUTION: This device has a focus gain regulating circuit 115 which detects the gain of the focus control system and regulates the gain of the focus control system so as to make this gain constant, a focus gain regulating value memory circuit 117 which saves the focus gain regulating value of the output of the focus gain regulating circuit when the balance value in focus error detection is changed at prescribed intervals and a focus gain regulating value switching circuit 118 which changes over the focus gain regulating value according to the output of the focus gain regulating circuit 114. The factors for the fluctuations in the focus control by the fluctuations in the focus error signal of the pickup to be used are decreased, by which the focus control is stabilized.