LOOP GAIN ADJUSTER FOR TRACKING SERVO LOOP

摘要

PURPOSE:To execute exact peak hold regardless of the size of eccentricity in a track by holding a relative speed constant between an objective lens and the track. CONSTITUTION:A CPU 8 calculates the amplitude value (detected p-p value) of a track error signal TES. The detected p-p value is compared with a p-p value, which is stored to a ROM 11 in advance, to be a reference (reference p-p value) and the output value of a D/A converter 12 is increased and decreased. Then, the gain of a variable gain amplifier 3 is adjusted by a gain control part 14. When the gain adjustment of the variable gain amplifier 3 is finished and a tracking servo loop is in a closed state, the output of the variable gain amplifier 3 is supplied to an objective lens control part 4 and the objective lens is controlled by the output signal. Then, the track is exactly followed up. Thus, regardless of the size of the eccentricity in the track, the peak hold can be exactly executed.