Optical memory system having improved positioning and focusing control circuitry.

摘要

An optical storage system employing a laser beam which is directed and focused onto an optical disk for reading and/or writing data in a track of the disk. Positioning control is achieved by providing for track following and track seeking using a plurality of interactive servo-loops. Proper focusing is maintained using focusing control circuitry which produces a focus error signal that is applied to a focus motor. This focusing control circuitry is able to return the objective lens assembly to its in-focus position so long as the objective lens assembly remains within a predetermined capture range. In the event that the objective lens assembly is outside of this capture range, a waveform generator is enabled which produces a correction signal that causes the focus motor to move the objective lens assembly back within the capture range with a velocity and for a time period sufficient to permit the focusing control circuitry to regain control and return the objective lens assembly to its in-focus position.