Patent ID: 6728035
Filing Date: 2004-04-27
Classification: G02B,G11B

Abstract:
An optical device comprising:a light-emitting element for irradiating light onto an information recording medium; a diffraction grating for splitting light emitted from said light-emitting element into a plurality of beams, the diffraction grating comprising a non-grating region; a focusing member for focusing the beams that have been split by the diffraction grating onto the information recording medium; a holographic element for splitting each of the plurality of beams after they have been reflected from the information recording medium into light for obtaining a reproduction signal for reproducing an information signal recorded on the information recording medium and light for obtaining a tracking error signal; and a photodetector for receiving each of the light that has been split by the holographic element and detecting the reproduction signal and the tracking error signal; wherein all or a portion of the light that has passed through the non-grating region enters the focusing member; light that has passed through the non-grating region is used as a main beam for recording/reproducing an information signal on/from the information recording medium, and +1-order and/or âˆ’1-order diffraction light generated in the diffraction grating is used as a sub-beam for detecting a tracking error signal.