Patent ID: 7952966

Claim:
A tracking apparatus for an optical information reproduction apparatus comprising: a photoelectric detector comprising a light-receiving cell divided into at least four areas by a parting line substantially parallel to a direction in which mapping of an information track of a recording medium on which information is optically recorded extends and by a parting line substantially perpendicular to the parting line, wherein a far-field pattern of a light spot converged on the recording medium is formed across the divided light-receiving cell; an arithmetic unit for receiving an output of the photoelectric detector and outputting at least a pair of arithmetic signals so that a tracking phase difference can be detected; a phase comparator for detecting a phase difference between the output signals of the arithmetic unit; an absolute value detector for detecting an absolute value of an output signal of the phase comparator; a level detector for generating and outputting a signal that indicates whether or not a convergence position of the light spot is located off an information track of the recording medium by detecting an over-threshold frequency of an output signal of the absolute value detector becoming larger than a predetermined value; a sensitivity detector for detecting and outputting sensitivity of the level detector by observing a signal output from the level detector; and a controller for adjusting detection conditions of the level detector so that the output of the sensitivity detector is a predetermined value, wherein the controller adjusts the detection conditions of the level detector so that, in the duty ratio, a length of an “H” level indicating that the light spot is positioned between information tracks is shorter than a length of an “L” level indicating that the light spot is positioned on an information track.