Dynamic information storage or retrieval – Dynamic mechanism subsystem – Specified detail of transducer assembly support structure
Reexamination Certificate
1998-03-03
2001-01-16
Cao, Allen T. (Department: 2754)
Dynamic information storage or retrieval
Dynamic mechanism subsystem
Specified detail of transducer assembly support structure
Reexamination Certificate
active
06175546
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to optical pickup (read/write head) for optical disc drives, and more particularly, to a curved-beam supporting structure for used on the objective-lens driving unit (actuator) of an optical pickup to support the focusing and tracking movements of the actuator.
2. Description of Related Art
Optical discs are a mass storage medium that can store a large amount of digital data thereon, which can be read by using optical disc drives. An optical disc drive is provided with an optical pickup (read/write head) for reading the data stored on an optical disc. During read operation, the optical pickup should be capable of focusing a laser beam precisely on the target track where the data to be read out are located. An objective lens is used for the focusing purpose. A driving unit (or called actuator) is used to move the objective lens in various directions during the focusing and tracking operations to bring the laser beam into focused and tracked condition. Defocusing and mistracking of the laser beam are usually caused by deviations and oscillations of the optical disc being read. The actuator should have the following features: (1) high sensitivity; (2) good dynamic characteristics, such as the capability to maintain stable operation in high-frequency regions; and (3) compact in size and low in manufacturing cost.
In the optical pickup, a supporting structure is used to support the actuator in such a manner that the actuator can freely move in both the focusing and tracking directions. A conventional type of supporting structure for the optical pickup actuator includes four parallel oriented straight beams to support the focusing and tracking movements of the optical pickup actuator, such as the one disclosed in the U.S. Pat. No. 4,842,392 “OBJECTIVE LENS DRIVING UNIT” to Nakamura. This patent discloses a parallel-beam supporting structure which is characterized in that the center of the driving force is coincident with the center of weight of the moving parts of the actuator. One drawback to the conventional parallel-beam supporting structure, however, is that it can cause the actuator to suffer from resonance that are caused by internal electromagnetic reaction forces. This drawback would cause the servo control for the focusing and tracking operations to be unstable.
SUMMARY OF THE INVENTION
It is therefore an objective of the present invention to provide a curved-beam supporting structure which is capable of supporting both the focusing and tracking movements of an optical pickup actuator used in an optical disc drive.
It is another objective of the present invention to provide a curved-beam supporting structure which can prevent the resonance that would otherwise be caused by the electromagnetic reaction force in the prior art when operating in the high-frequency regions.
In accordance with the foregoing and other objectives of the present invention, a new supporting structure is provided for supporting the focusing and tracking movements of an optical pickup actuator in an optical disc drive. The optical pickup has an objective lens supported by a lens holder. The supporting structure of the invention includes the following constituent parts: a voice-ring motor yoke for supporting the actuator; and at least four curved beams made of metal, including a first curved beam, a second curved beam, a third curved beam, and a fourth curved beam, all of which are mounted between the yoke and the lens holder and oriented in perpendicular to both the tracking and focusing directions of the actuator, the first and second curved beams being mounted on one side of the actuator and the third and fourth curved beams being mounted on the other side of the actuator, the first and third curved beams being arranged farther away from the yoke than the second and fourth curved beams. The curved design of the beams can reduce the rigidity of these beams in the radial direction of the actuator.
REFERENCES:
patent: 5761183 (1998-06-01), Ikegame
patent: 5933405 (1999-08-01), Song
patent: 6018509 (2000-01-01), Itoh et al.
patent: 6-162538 (1994-06-01), None
Cao Allen T.
Industrial Technology Research Institute
Knobbe Martens Olson & Bear LLP
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