Tracking error correction apparatus utilizing phase difference

Abstract

Disclosed herein is an optical information reproducing apparatus having a phase difference tracking system which is free from an influence of a tangential phase difference of output signals from a photodetector. The photodetector comprises first through fourth photocells which are respectively disposed at first through fourth quadrants defined by a first straight line parallel to an information track image and a second straight line perpendicular to the first straight line. Output signals of the first and second photocells are delayed for a specified time by respective first and second delaying circuits. Output signals of the first delaying circuit and the third photocell are added by a first adder, and output signals of the second delaying circuit and the fourth photocell are added by a second adder. A phase comparator produces a tracking error signal from a phase difference between output signals of the first and second adders. Alternatively, a first phase comparator produces a phase difference between the output signals of the first and second photocells, and/or a second comparator produces a phase difference between the output signals of the third and fourth photocells. At least one of output signals of the first and second comparator is used for producing a tracking error signal.