Short Seeks in Optical Disk
Original Publication Date: 1988-Mar-01
Included in the Prior Art Database: 2005-Feb-14
Optical disk having extremely high radial track densities are subject to minute run out or eccentricity T4 errors. Such run out can cause several tracks to radially pass a sensing transducer or lens during each disk rotation. Such run out can be used to advantage in short seeks. In an arrangement wherein a fine actuator is mounted for motion on a coarse actuator, the coarse actuator is locked to the profile of the run out while the fine actuator seeks the target track as if the disk track is perfectly circular. The above procedure is useful when the eccentricity is causing the track to apparently move away from the lens. When the target track is apparently moving toward the lens and the run out is large, then the coarse actuator is put in a stop-lock position such that no track following occurs nor is any profiling used.