Patent ID: 7206266
Filing Date: 2007-04-17
Classification: G11B

Abstract:
1. An optical pickup comprising: at least one light source; at least one light splitting device which splits light from the light source into a main beam and four or more sub beams symmetrical with respect to the main beam, which are then emitted on an optical data storage medium, wherein the four or more sub beams include two first sub beams located close to the main beam and two second sub beams located away from the main beam; and at least one photodetecting device, which receives the main and sub beams reflected off the optical data storage medium; wherein where phase differences between the two first sub beams and between the two second sub beams are PH1 and PH2, respectively, the first and second sub beams are emitted on the optical data storage medium so that PH1 and/or PH2 satisfy Equations (1) and/or (2) given below, respectively, and a tracking error signal is detectable by a differential push-pull (DPP) method using the main beam and the two first sub beams and the main beam and the two second sub beams for ±R/RW and RAM type optical data storage media, respectively: