Patent ID: 7916418

Claim:
A method for controlling a rotation velocity of an optical disc, the method comprising the acts of: a first signal-generation, comprising generating a first periodic signal within a first frequency range via a first sensor; a first control, comprising controlling the rotation velocity of a motor controlling the rotation of the optical disc within a first velocity range, the rotation velocity control depending on the first periodic signal; a second signal-generation, comprising generating a second periodic signal within a second frequency range via a second sensor, the second periodic signal chosen such that: a constant ratio exists between a first frequency of the first periodic signal and a corresponding second frequency of the second periodic signal, independent of the rotation velocity of the motor; and a constant phase difference exists between a phase of the first periodic signal and a corresponding phase of the second periodic signal, independent of the rotation velocity of the motor; a calibration, comprising controlling the motor at a calibration rotation velocity within the first velocity range depending on the first periodic signal, the calibration velocity being chosen such that the corresponding calibration second frequency of the second periodic signal falls within the second frequency range; a mapping, comprising determining a relation between the second periodic signal and the first periodic signal at the calibration rotation velocity; and a second control, comprising controlling the motor at a desired rotation velocity outside the first velocity range depending on the second periodic signal and the determined relation between the second periodic signal and the first periodic signal.