Patent ID: 7180838
Filing Date: 2007-02-20
Classification: G11B

Abstract:
1. An optical pickup apparatus for recording/reproducing with respect to a disc, comprising: a light source module which emits a light beam, wherein the light source module includes a first light source and a second light source that emit first and second light beams having different wavelengths and are formed into a single module; a first grating which divides the first light beam emitted from the first light source and transmits the second light beam emitted from the second light source; a second grating which transmits the first light beam emitted from the first light source and divides the second light beam emitted from the second light source; a beam splitter which reflects or transmits the light beam emitted from the light source module; an objective lens which focuses the light beam passing through the beam splitter onto the disc; and a photodetector which receives and detects the light beam reflected by the disc, wherein the photodetector comprises a first photodetector which detects the first light beam and a second photodetector which detects the second light beam, the first and second gratings divide the corresponding first and second light beams into three beams of the first light beam and three beams of the second light beam, and the first photodetector comprises a main photodetector having a main four-division structure and sub-photodetectors, each having a sub four-division structure, arranged at both sides of the main photodetector, the first photodetector detects a tracking error detection signal (TES) and a focusing error detection signal (FES) with respect to the disc, using a differential push-pull (DPP) method and a differential astigmatism method, respectively, using the four detection signals of the main photodetector and the eight detection signals of the sub-photodetectors, and the TES and FES satisfy the following relationships: where A, B, C and D correspond to detection signals of the main photodetector, I