Patent ID: 8098556

Claim:
An optical disc drive comprising: a motor for rotating an optical disc; an optical system for irradiating the optical disc with a light beam; a moving mechanism for moving the optical system along the radius of the optical disc; a focus control section for controlling movement of the optical system perpendicularly to the optical disc, thereby focusing the light beam onto a storage layer of the optical disc; and a tilt control section for measuring the tilt quantities of the storage layer at multiple different radial locations on the optical disc based on focus drive values for the respective radial locations when the focus control section focuses the light beam there, wherein when the tilt control section does not measure a tilt quantity, the motor rotates the optical disc at mutually different rotational frequencies at a first radial location and a second radial location that is different from the first radial location, and wherein when the tilt control section measures a tilt quantity, the motor keeps the rotational frequency of the optical disc constant at both of the first and the second radial locations, and the tilt control section uses a first and a second focus drive values that have been obtained at the first and the second radial locations.