Optical memory system providing improved focusing control.

摘要

A laser optical system including a reading beam for reading optical data recorded in one or more tracks of a rotating disk optical recording medium. The disk includes a plurality of preformatted headers spaced along the track wherein each header includes a plurality of spaced focusing optical holes having dimensions chosen based on the diameter of the focused laser beam spot. Traversal of these optical holes by the reading beam produces a reflected beam which varies in a manner dependent upon the quality of focusing of the beam. Peak detection circuitry responsive to this reflected beam is used to produce a high gain focusing signal which is combined with a low gain, high capture range focusing signal provided by a geometric focus detector to derive a precise, offset-free focusing control signal which is applied to a focusing motor to main precise focusing of the beam on the disk.