# US 5,347,500 A · Compact optical pickup head with tracking error signal generator

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- Number: US 5,347,500 A
- Document ID: US5347500A
- Status: Granted
- Kind: A
- Application number: 08/159,080
- Filed: 1993-11-29
- Granted: 1994-09-13
- Earliest claimed: 1989-06-21
- Assignees: Sony Corporation
- Inventors: Naoya Eguchi
- Web page: https://patentgrep.com/patent/US5347500A

## CPC

- G11B 7/08564: {using galvanomirrors}
- G11B 7/08582: {Sled-type positioners}
- G11B 7/0927: {for focusing only (G11B7/0937 takes precedence)}
- G11B 7/135: Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)

## Abstract

An optical pickup head apparatus comprises a yoke provided in an opposing relation to a magnet, a movable member having formed therethrough an aperture into which the yoke is inserted and around which a first coil is wound in an opposing relation to the magnet, an object lens supporting device having a pair of leaf springs for supporting the objective lens so that the objective lens can move in the direction parallel to the optical axis thereof and a plurality of second coils of substantially square shape for moving the objective lens in the direction parallel to the optical axis thereof and a tracking control device for rotating a mirror portion so that a beam spot focused on the optical disc by the objective lens follows a track on the optical disc, wherein the objective lens supporting device is secured to the movable member, the movable member is movably supported by the yoke and sides of the second coils which cross the optical axis of the objective lens and the first coil are located within a common magnetic gap.

## Claims

### Claim 1

An optical pickup head apparatus having a tracking error signal generating device for a tracking error signal on the basis of a detected output a photodetecting device and a tracking control device for performing a tracking servo by rotating a mirror in response to the tracking error signal supplied thereto, which apparatus comprises:
a magnet;
yoke means provided in an opposing relation to said magnet;
a movable member having an aperture into which said yoke means is inserted;
a first coil wound around said movable member in opposing relation to said magnet.;
an objective lens having an optical axis; and
objective lens supporting means for supporting said objective lens to be movable in a direction parallel to said optical axis and having a plurality of second coils to move said objective lens in said direction, wherein said supporting means is secured to said movable member, said movable member is supported by said yoke means so that it can freely move in a direction perpendicular to said optical axis, and at least one side of said first and second coils is located within a common magnetic gap;
wherein each of said second coils has four sides and is formed as a substantially square coil of L-letter shape, a pair of sides of each of said second coils being perpendicular to the optical axis of said objective lens and one side of each of said second coils being located within said common magnetic gap.

### Claim 2

An optical head apparatus comprising:
a fixed optical system including a light beam source, a photodetector, and a beam splitter for splitting a light beam emitted from said light beam source, so that a portion of the light beam is irradiated on said photodetector;
a movable optical system having an objective lens, a first coil, a focussing actuator for supporting said objective lens and for moving said objective lens in a direction parallel to an optical axis of said objective lens using at least one of a plurality of second coils, each having four sides and being formed as a substantially square coil of L-letter shape, a pair of sides of each of the plurality of second coils being formed perpendicular to the optical axis of said objective lens, one side of each of the plurality of second coils being formed parallel to the optical axis of the objective lens, a member provided on said actuator, a linear motor including magnets provided to face said first coil and said sides of said plurality of second coils parallel to said optical axis, whereby said sides of said plurality of second coils parallel to said optional axis are within a common magnetic gap formed by said magnets of said linear motor, guiding means for guiding said member in a direction perpendicular to the axis of said objective lens, and a yoke, said movable optical system being provided in a plane that is parallel to the direction perpendicular to the axis of the objective lens and said fixed optical system being provided in said same plane; and
a tracking means provided between said fixed optical system and said movable optical system and including a mirror for changing a path of the light beam emitted from said light beam source and the light beam irradiated on said photodetector.