Patent ID: 8023371

Claim:
An optical drive for reading or writing an optical disc by means of a laser beam, the optical disc comprising: a first area with a first frequency which corresponds to a pre-recorded HFM-groove expected on the optical disc, a second area with a second frequency which corresponds to a wobble frequency of a wobbled groove expected on the optical disc and a third area with a third frequency which corresponds to a HF frequency of data expected on the optical disc, wherein the first, second and third frequencies are different from each other and characteristic of the respective first, second and third areas of the optical disc, wherein each of said first, second and third frequencies are associated with a reading and/or writing position of the laser beam, control means ( 12 ) and at least three PLL units wherein the control means are adapted to control the three PLL units to try to lock on to a different one of the first, second and third frequencies, and, wherein the control means are arranged to indicate to the optical drive the reading and/or writing position of the laser beam based on a change in obtained locks indicating the occurrence of a transition between areas of the optical disc with different characteristic frequencies.