Patent ID: 7272084
Filing Date: 2007-09-18
Classification: G11B

Abstract:
1. An optical disk apparatus comprising: an objective lens configured to focus a main beam and side beams onto an optical disk, the side beams being held in a fixed relationship with respect to the main beam; light-receiving means for receiving return lights of the main beam and the side beams; and signal processing means for processing light detection results of the light-receiving means to generate at least a track-cross signal and a tracking error signal, wherein the fixed relationship is such that, if the track pitch between lands, where a track is formed of a land, or the track pitch between grooves, where a track is formed of a groove, is indicated by P, the side beams scan in positions that are offset with respect to the main beam by approximately (¼+n) P in the radial direction of the optical disk, where n denotes an integer; the light-receiving means includes: at least two side beam light-receiving areas for receiving the return light of the side beams, said at least two side beam light-receiving areas being divided into first and second side beam light-receiving regions by an axis corresponding to the direction in which the track extends, and a main beam light-receiving area for receiving the return light of the main beam, said main beam light-receiving area being divided into third and fourth main beam light-receiving regions by a further axis corresponding to at least the direction in which the track extends; and the signal processing means includes: first subtracting means for generating a differential signal between light detection results obtained from the first and second light-receiving regions to generate the track-cross signal; second subtracting means for generating a differential signal between light detection results obtained from the third and fourth light-receiving regions; band-limiting means for removing a traverse component from the light detection result of a light-receiving region of the first and second side beam light-receiving regions which is a far light receiving region with respect to the third and fourth light-receiving regions; amplifying means for amplifying an output signal of the band-limiting means with a predetermined gain; and computing means for computing an output signal of the amplifying means with respect to an output signal of the second subtracting means so as to be added to the light detection result of the far light-receiving region out of the third and fourth light-receiving regions to generate the tracking error signal.