Track Step on an Optical Disk
Original Publication Date: 1986-Jul-01
Included in the Prior Art Database: 2005-Mar-09
In an optical disk drive there is a track-following servo which keeps the transducer (laser scanning head) positioned over a single disk track. This servo must also be able to step the transducer to an adjacent track quickly and reliably. It is not feasible to do this under closed-loop control due to instability in the tracking error signal between tracks, and because of imperfections in the disk or in the optics, such as varying track widths, disk defects, and lens off-axis performance, which make the tracking error signal quite variable. Typical open-loop stepping is very unreliable because of the relatively large run out of the disk, compared to the track pitch.