Patent ID: 7031248

Claim:
An apparatus for generating push-pull signals, used in an optical-disk apparatus having a photo-detector for photo-detecting, a light beam reflected from a recording surface of an optical disk having formed spiral-shaped or concentric-shaped tracks in at least a first photo-detecting region and a second photo-detecting region which are divided into two parts by a dividing line in the direction corresponding to the tangential direction of the tracks, the signals consisting of a first photo-electric converting signal from said first photo-detecting region and a second photo-electric converting signal from said second photo-detecting region, comprising: a first signal-adjusting circuit configured to adjust said first photo-electric converting signal at a first gain; a second signal-adjusting circuit configured to adjust said second photo-electric converting signal at a second gain; gain-determining means configured to select one of an amplitude and an average level of an output signal of said first signal-adjusting circuit as a first determining value and selecting the amplitude or the average level which corresponds to said first determining value from one of an amplitude and an average level of an output signal of said second signal-adjusting circuit as a second determining value, and determining, based on said first determining value and said second determining value, at least one of said first gain and said second gain such that a predetermined noise component level contained in the output signal of said first signal-adjusting circuit and a predetermined noise component level contained in the output signal of said second signal-adjusting circuit are almost equal to each other; and a difference-signal generating circuit configured to generate a difference signal between the output signal of said first signal-adjusting circuit and the output signal of said second signal-adjusting circuit.