Patent ID: 6804180
Filing Date: 2004-10-12
Classification: G11B

Abstract:
An optical head assembly comprising:a light source; an objective lens which focuses transmitted light from said light source onto an optical recording medium; a photodetector adapted to receive reflected light from the optical recording medium, wherein said photodetector has light receiving elements, each light receiving element individually receiving light components of the reflected light directed to regions on one side in the tangential direction of the optical recording medium, the regions being on both sides in the radial direction of the optical recording medium; light components of the reflected light directed to regions on the other side in the tangential direction of the optical recording medium, the regions being intermediate in the radial direction of the optical recording medium; light components of the reflected light directed to regions on one side in the tangential direction of the optical recording medium, the regions being intermediate in the radial direction of the optical recording medium; and light components of the reflected light directed to regions on the other side in the tangential direction of the optical recording medium, the regions being on both sides in the radial direction of the optical recording medium; and a signal processing circuit for use in generating a focus error signal, a tracking error signal, and a playback signal, in response to the outputs of said photodetector, wherein said signal processing circuit comprises a tilt signal generating unit for generating a tangential tilt signal according to a difference between a sum of the outputs of the light receiving elements that receive the light components of the reflected light directed to the regions on one side in the tangential direction of the optical recording medium, the regions being on both sides in the radial direction of the optical recording medium and the light components of the reflected light directed to the regions on the other side in the tangential direction of the optical recording medium, the regions being intermediate in the radial direction of the optical recording medium, and a sum of the outputs of the light receiving elements that receive the light components of the reflected light directed to the regions on one side in the tangential direction of the optical recording medium, the regions being intermediate in the radial direction of the optical recording medium and the light components of the reflected light directed to the regions on the other side in the tangential direction of the optical recording medium, the regions being on both sides in the radial direction of the optical recording medium, the tangential tilt signal being indicative of an amount of tilt of the optical recording medium in the tangential direction with respect to said objective lens.