Patent ID: 6185167
Filing Date: 2001-02-06
Classification: G11B

Abstract:
An optical head comprising:a light-emitting element;a plurality of light-receiving elements;an objective that converges light from said light-emitting element onto asurface of an information-recording medium;a diffraction element located in an optical path between said light-emitting element and said objective to spatially divide a luminous flux into a plurality of luminous fluxes to guide the plurality of luminous fluxes to said plurality of light-receiving elements, said luminous flux reflected by said information-recording medium; andsignal generation means for generating a focus error signal and a tracking error signal;wherein said diffraction element has six areas divided by a first parting line substantially parallel to a direction of information tracks of said information-recording medium and second and third parting lines substantially orthogonal to the first parting line, andsaid signal generation means (1) generates said focus and tracking error signals based on detection signals from said light-receiving elements resulting from luminous fluxes passing through two of said six areas, said two areas located between said second and third parting lines and (2) generates an offset correction signal correcting an offset caused by movement of said objective based on detection signals from said light-receiving elements resulting from luminous fluxes passing through four of said six areas, said four areas located outside said second and third parting lines.