Burroughs, Inc.

Robert L Hazel

Gilbert Y Chan

Edward V LaBudde

John E Kammerud

An optical memory system is disclosed employing laser beams for reading and writing data in an optical disk. The system incorporates a specially designed spatial combining and separating device which functions to combine a writing laser beam with a plurality of reading laser beams in a manner so as to permit the combined beams to be precisely focused on the disk. The spatial combining and separating device also functions to separate the reading laser beams from the writing laser beam after they are reflected from the disk in a manner so as to prevent the higher intensity writing beam from interfering with the proper detection of the lower intensity reading beams.

Laser optical memory system having beam combining and separating

Focus detecting apparatus is disclosed which is useful, for example, in an optical storage system for detecting the quality of focusing of a laser beam on the surface of an optical medium. For focus detection purposes, the reflected beam is collected and separated into two beams which are applied to first and second photosensitive elements, respectively. Focus detection is achieved based on determining the difference between the diameters of the beams incident on the photosensitive elements which are located so that the diameters of the beams applied thereto are indicative of the quality of focusing of the beam on the surface.

Focus detection and control apparatus for maintaining accurate focusing

An optical storage system is disclosed having improved spatial combining and separating apparatus along with improved focus detection and control apparatus. The spatial combining and separating apparatus functions to precisely combine a writing laser beam with a reading beam prior to focusing on an optical medium, and also functions to separate the reading and writing beams after reflection from the medium in a manner so as to prevent interference therebetween. The improved focus detecting and control apparatus employs a portion of the reflected reading beam to derive two beams which are applied to first and second photosensitive elements, respectively. Focus detection is achieved based on determining the difference between the diameters of the beams incident on the photosensitive elements which are located so that the diameters of the beams applied thereto are indicative of the quality of focusing of the beam on the surface.

Optical memory system providing improved focusing control and improved

Optical apparatus is disclosed for spatially combining and/or separating a plurality of reading and writing laser beams as required, for example, in an optical memory system. The apparatus includes a spatial combining and separating device comprising a thin transparent element which is provided with reflective and anti-reflective coatings and an appropriately located opening in a manner so as to permit the original and reflected writing beams to pass through the device without change in direction while the original and reflected reading beams are reflected from the device in predetermined directions.

Beam combining and separating apparatus useful for combining and

An optical storage system is disclosed having improved focus detecting and controlling apparatus which is responsive to a reading laser beam reflected from an optical medium so as to provide a focus error signal having a high gain in the immediate vicinity of the in-focus position along with a wide capture range. Focus detection is achieved based on determining the difference between the diameters of the beams applied to a pair of photosensitive elements located so that the diameters of the beams applied thereto are indicative of the quality of focusing of the reading beam on the optical medium.

Optical memory system providing improved focus detection and control by

A three beam laser optical system comprising a writing beam and two reading beams all incident on the same track of a rotating disk optical recording medium. One of the reading beams is incident on the track ahead of the writing beam so as to serve as a read-before-write beam, while the other reading beam is incident on the track behind the recording beam so as to serve as a read-after-write beam. The read-before-write beam is used during the recording of data to provide an advance indication as to whether there is previously recorded data ahead of the writing beam, in which case the recording operation is interrupted to prevent an overwrite error. The read-after-write beam is used during recording to check the accuracy of the recording operation.

Three beam optical memory system

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 first and second track following optical holes which are elongated in the direction of the track and disposed on opposite sides of the track center line in a staggered relationship along the track. Traversal of these track following holes by the reading beam produces a reflected beam which varies in a manner dependent upon the accuracy of positioning of the beam relative to the track center line. Up-down integration circuitry responsive to this reflected beam is used to produce a track following signal which is applied to a radial position control motor for maintaining the beam precisely on the track center line.

Optical memory system providing track following

An apparatus for preformatting each track of an optical disk with spaced header patterns using a plurality of overlapping, individually modulated writing laser beams arranged in a line perpendicular to the track. All of the writing laser beams are derived from a single multi-line laser so as to provide high positioning stability, and adjacent beams are chosen to have different wavelengths in order to prevent the deleterious effects of coherent interference between the overlapping beams. A specific header pattern is provided on a single pass by turning on different ones of the writing beams during specific time periods as each header recording area is traversed. A laser read-after-write beam is additionally provided to permit immediate verification of the recorded header pattern.

Apparatus for preformatting an optical disk

A method for preformatting each track of an optical disk with spaced header patterns using a plurality of overlapping, individually modulated writing laser beams arranged in a line perpendicular to the track. All of the writing laser beams are derived from a single multi-line laser so as to provide high positioning stability, and adjacent beams are chosen to have different wavelengths in order to prevent the deleterious effects of coherent interference between the overlapping beams. A specific header pattern is provided on a single pass by turning on different ones of the writing beams during specific time periods as each header recording area is traversed. A laser read-after-write beam is additionally provided to permit immediate verification of the recorded header pattern.

Methods of preformatting an optical disk

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.

Optical memory system providing improved focusing control

A preformatted optical recording disk for use in an optical data storage system in which a laser beam of predetermined frequency is focused on the disk. The disk comprises a substrate having reflective, dielectric and absorbing layers deposited in a manner so as to establish an anti-reflection condition for an incident laser beam. The disk is preformatted by recording optical holes in the absorbing layer so as to form one or more tracks wherein each track includes a plurality of headers positioned at predetermined locations along the track. Each header comprises a plurality of optical holes constructed and arranged so as to constitute predetermined embedded timing, track following and focusing data on the disk for use by an optical data storage system.

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Thousand Oaks, CA, United States of America

Robert L Hazel