Optical Storage Media Focusing Servo
Original Publication Date: 1988-Apr-01
Included in the Prior Art Database: 2005-Feb-15
The optical head of an optical disk drive is focused on the track-containing surface of an optical disk by ANDing the signal received from the focusing detectors and from the tracking detectors. (Image Omitted) The head is controlled to move first toward and then away from the disk, in a cyclic fashion (for example, for five cycles). As a result, a focus signal of minor amplitude is generated each time the head moves through focus on, for example, a surface of the disk's transparent protective cover. However, each time the head moves into a focus position on the disk's track-containing layer, a higher magnitude signal is generated due to this surface's high reflection. At the same time that the head is moved toward and away from the disk, the head is dithered in its orthogonal tracking axis.