Patent ID: 7859967

Claim:
An optical disk drive for scanning an optical disk, the optical disk drive comprising: an optical source for generating an incident beam; an objective lens arranged to be driven by a focus actuator with a focus offset; a sensor for sensing a reflected beam produced by the optical disk upon receiving the incident beam, and for producing a sensor output signal; a processor arranged to: receive the sensor output signal from the sensor, derive at least a first and a second characteristic from the sensor output signal, the second characteristic being different from the first characteristic, determine first values of the first characteristic as a function of a plurality of values of the focus offset, determine second values of the second characteristic as a function of a plurality of values of the focus offset, determine from the first values a first optimal focus offset at which the first characteristic is optimal, determine from the second values a second optimal focus offset at which the second characteristic is optimal, obtain a first spherical aberration correction value from a pre-determined function, repeat the determination of the first optimal focus offset and the determination of the second optimal focus offset when the first spherical aberration correction value is applied to a spherical aberration correction actuator, obtain a second spherical aberration correction value from said pre-determined function, and a spherical aberration correction controller arranged to apply the second spherical aberration correction value to the spherical aberration correction actuator.