Abstract: An optical reading apparatus comprises a photodetector having equally divided first, second, third and fourth segments which are arranged in the path of light reflected from an optical recording medium. The first and second segments are aligned in a direction parallel to the track on the medium and the third and fourth segments are aligned in a direction perpendicular to the track. A readout circuit is provided for deriving an output A.multidot.a+B.multidot.b from the outputs of the first, second, third and fourth segments, where A and B represent constants, a represents a summed value of the outputs of the first, and second, third and fourth segments and b represents a summed value of the outputs of the first and second segments.

Abstract: A circuit applicable to an optical disk apparatus or similar optical information storing apparatus for reading out information being stored. A differentiated signal produced by differentiating an analog signal read out is compared with a predetermined threshold value to produce a leading edge level signal and a trailing edge level signal which are respectively the results of comparison performed in a polarity immediately before a peak of the analog signal and a polarity immediately after the peak. The leading edge level signal is delayed by a predetermined period of time and then compared with a peak signal for coincidence. The result of this comparison is further delayed by a predetermined period of time and then compared with the trailing edge level signal for comparison to deliver the result as read out data.