Dynamic optical information storage or retrieval – Dynamic mechanism optical subsystem – Transducer carriage or actuator
Reexamination Certificate
2002-03-21
2004-10-05
Ometz, David (Department: 2653)
Dynamic optical information storage or retrieval
Dynamic mechanism optical subsystem
Transducer carriage or actuator
C720S675000
Reexamination Certificate
active
06802071
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an optical pickup supporting device for use in an optical disc.
Generally, an optical pickup supporting device comprises a sheet metal base (chassis) having a generally plate-like shape, a main guide shaft mounted to the base in parallel to a plate surface of the base, and a sub guide shaft mounted to the base in parallel to both of the plate surface of the base and the main guide shaft.
When an optical pickup is driven by a drive mechanism, the optical pickup is guided by the main and the sub guide shafts in a tracking direction.
In order to meet various demands, such as a greater recording capacity of the optical disc and a higher access speed for the optical disc, it is required for an optical disc drive to have a high-accuracy mechanism. As one approach to achieve such a high-accuracy mechanism, it is proposed to improve the dimensional accuracy of components or parts of the optical disc drive. Practically, however, it is difficult to produce the parts of the optical disc drive with a higher dimensional accuracy than that achieved at present. Therefore, the above-mentioned approach can be carried out merely by producing the parts with the dimensional accuracy achieved at present and by selecting those parts which meet higher-accuracy criteria. In this event, the ratio of failed products, which are out of criteria and are not selected, is increased at the stage of parts production. This results in an increase in manufacturing cost of the optical disk drive.
In view of the above, attention is turned to another approach capable of realizing the high-accuracy mechanism without improving the dimensional accuracy of the parts. In this context, proposal is made of a method of adjusting mounting positions of the parts so as to allow dimensional inaccuracy to some extent.
As one of the parts mounting positions to be adjusted in the optical disc drive, there is an elevation angle position of each of the guide shafts for guiding the optical pickup used in the optical disc drive. The elevation angle position of the guide shaft is given by an elevation angle of the guide shaft, i.e., an angle in a vertical plane with respect to the plate surface of the base.
If the above-mentioned elevation angle position is not adjusted to an appropriate value, a laser beam emitted from the optical pickup cannot properly irradiate a data reproducing/recording surface of the optical disc. Specifically, an optical axis of the laser beam emitted from the optical pickup is inclined with respect to a principal surface of a disc table for supporting and rotating the optical disc. This phenomenon is called a skew error. Alternatively, the laser beam is not focused upon the data reproducing/recording surface of the optical disc.
In this connection, at least the main guide shaft is held and fixed on the base so that the elevation angle of the main guide shaft is adjustable by an elevation angle adjusting mechanism with respect to the plate surface of the base.
On the other hand, the sub guide shaft is not a driven part of the optical pickup which is driven by the drive mechanism but is a structure for guiding and supporting those parts following such driven part. Therefore, the sub guide shaft may not be provided with the above-mentioned elevation angle adjusting mechanism.
Next, description will be made about several existing optical pickup supporting devices.
A first existing optical pickup supporting device comprises main and sub guide shafts for guiding an optical pickup in cooperation with each other so that the optical pickup is moved in a predetermined direction. The sub guide shaft is made of resin and is attached to a sheet metal base by a so-called outsert molding.
A second existing optical pickup supporting device comprises a sheet metal base having first and second plate surfaces (upper and lower surfaces) and main and sub guide shafts arranged above the upper surface of the base for guiding an optical pickup in cooperation with each other so that the optical pickup is moved in a predetermined direction. Each of the main and the sub guide shafts is held and fixed on the upper surface of the base so that its elevation angle position (i.e., an elevation angle in a vertical plane along a thickness direction of the base) with respect to the upper surface of the base is adjustable. The optical pickup supporting device includes a pair of supporting units for supporting the main and the sub guide shafts, respectively. Each of the supporting units comprises a cylindrical cam member made of resin and rotatably attached to the upper surface of the base by outsert-molding, a holder made of resin and attached to the base to hold the main or the sub guide shaft, and a torsion spring attached to the base for pressing a peripheral surface of an end portion of the main or the sub guide shaft arranged above the base so that the guide shaft is urged towards the upper surface of the base. The cam member is provided with a spiral groove formed on its outer peripheral surface. The spiral groove receives the end portion of the main or the sub guide shaft. When the cam member is rotated, the end portion of the main or the sub guide shaft inserted in the spiral groove is moved upward or downward under the urging force of the torsion spring. Thus, the elevation angle position of the main or the sub guide shaft is adjusted.
A third existing optical pickup supporting device comprises a sheet metal base having first and second plate surfaces (upper and lower surfaces) and main and sub guide shafts arranged above the upper surface of the base. The main and the sub guide shafts serve to guide an optical pickup in cooperation with each other so that the optical pickup is moved in a predetermined direction. Each of the main and the sub guide shafts is held and fixed on the upper surface of the base so that its elevation angle position (i.e., an elevation angle in a vertical plane along a thickness direction of the base) with respect to the upper surface of the base is adjustable. The optical pickup supporting device comprises a pair of supporting units for supporting the main and the sub guide shafts, respectively. Each of the supporting units comprises a male screw engaged with a female thread portion formed in the base, a bent portion formed on the base for holding the main or the sub guide shaft, and a compression spring attached to the base for pressing a peripheral surface of an end portion of the main or the sub guide shaft arranged above the base so that the guide shaft is urged away from the upper surface of the base. The male screw has a flange portion formed at its end. The end portion of the guide shaft is held between the flange portion of the male screw and the compression spring. When the male screw is rotated, the end portion of the main or the sub guide shaft is moved upward or downward under the urging force of the compression spring. Thus, the elevation angle position of the main or the sub guide shaft is adjusted.
The first optical pickup supporting device has a metal part (the base) and a resin part (the sub guide shaft). Furthermore, the outsert molding is necessary to form the sub guide shaft on the base. Therefore, the number of steps is increased and the production cost is inevitably becomes high. In addition, it is relatively difficult to injection mold the sub guide shaft with high dimensional accuracy. Furthermore, because a major part of the sub guide shaft is arranged on the upper surface of the base, only a small space is left on the base to arrange other parts of the device. The above-mentioned structure is therefore disadvantageous in view of the reduction in thickness (height) of the optical disc drive.
The second existing optical pickup supporting device requires a large number of component parts and has a metal part (the base) and a resin part (the cam member). Furthermore, it is relatively difficult to injection mold the groove of the cam member with high dimensional accuracy. In addition, many component parts of the device are arranged on
Kirii Atsushi
Saito Ryuichi
Watanabe Takashi
Frishauf Holtz Goodman & Chick P.C.
Mitsumi Electric Co. Ltd.
Ometz David
LandOfFree
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