Patent ID: 6064637
Filing Date: 2000-05-16
Classification: G11B

Abstract:
A focusing and tracking method for use on an optical drive to control the focusing and tracking of a read/write head, comprising the steps of:generating a laser beam;guiding the laser beam to an optical disc;focusing the laser beam on the optical disc;guiding the reflected light from the optical disc to a double-focal-length device that includes a single lens having a first focusing portion to focus a first part of the reflected light at a first focus point, and having a second focusing portion to focus a second part of the reflected light at a second focus point that is different than the first focus point;guiding the light passing through said double-focal-length device to a photo detector having a central zone and a peripheral zone;said central zone being disposed to receive the first part of the reflected light so as to obtain a focusing error signal therefrom, said focusing error signal being subsequently used for feedback control of the focusing of the laser beam until the laser beam is focused precisely on the optical disc, andsaid peripheral zone being disposed to receive the second part of the reflected light so as to obtain a tracking error signal therefrom, said tracking error signal being subsequently used for feedback control of the tracking of the laser beam until the laser beam is spotted on the target track on the optical disk.