Burroughs, Inc.

Gilbert Y Chan

Robert L Hazel

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.

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Agoura, CA, United States of America

Gilbert Y Chan