Patent ID: 8111595

Claim:
An optical disc recording and playback apparatus comprising: an optical pickup performing an operation for recording and playing back signal information into and from an optical disc; an optical element allowing a light beam irradiated onto an optical disc by the optical pickup to be split into a main beam and sub-beams on both sides of the main beam and supplying the beams to the optical disc; an optical detector detecting return light from the optical disc; a control circuit performing tracking using a differential push-pull method when information pits or recording marks within the track control error signal do not exist, and performing tracking by comparing a differential push-pull track error signal and a phase difference track error signal to determine which one has a larger signal amplitude and selecting the one with the larger signal amplitude when information pits or recording marks within the track control error signal exist; and a computation circuit detecting a track control error signal by a phase difference method and a differential push-pull method by using the detection signal from the optical detector and also detecting a wobble signal, wherein the optical detector includes a four-division light-receiving element detecting return light of the main beam by light-receiving areas divided at least in a direction tangent to the tracks of the optical disc and in the radial direction of the optical disc, and two two-division light-receiving elements, disposed on both sides of the four-division light-receiving element, detecting return light of the sub-beams by the light-receiving areas divided at least in the direction tangent to the tracks, the computation circuit includes normalization means normalizing a pit playback signal from each light-receiving area in the four-division light-receiving element of the optical detector to a fixed value, and computes the wobble signal and a track control error signal by the phase difference method by using the normalized pit playback signals, the computation circuit computes the wobble signal by detecting the presence of information pits or recording marks previously formed on the optical disc and by sampling only the detected information pits or only the detected recording marks in the signal received by the four-division light-receiving element, and the detected recording marks exclude spaces between the detected recording marks or between the detected information pits.