TRACKING APPARATUS FOR OPTICAL INFORMATION REPRODUCTION APPARATUS

摘要

A tracking apparatus for an optical information reproduction apparatus includes the following: a photoelectric detector (1) in which a far-field pattern of a light spot converged on a recording medium is formed across a divided light-receiving cell; an arithmetic unit (2) for outputting at least a pair of arithmetic signals from the output of the photoelectric detector (1); a phase comparator (4) for detecting a phase difference between the output signals of the arithmetic unit (2); an absolute value detector (8) for detecting an absolute value of the output signal of the phase comparator (4); a level detector (9) for generating a signal that indicates whether or not a convergence position of the light spot is located off an information track by detecting a predetermined number of times or more the output signal of the absolute value detector (8) has become larger than a predetermined value; a sensitivity detector (10) for detecting and outputting the sensitivity of the level detector (9) by observing the output signal of the level detector (9); and a controller (11) for adjusting the detection conditions of the level detector (9) so that the output of the sensitivity detector (10) is a predetermined value.