Dynamic information storage or retrieval – Dynamic mechanism subsystem – Specified detail of transducer assembly support structure
Reexamination Certificate
1999-08-02
2002-06-11
Klimowicz, William (Department: 2652)
Dynamic information storage or retrieval
Dynamic mechanism subsystem
Specified detail of transducer assembly support structure
C029S469000, C029S896930, C029S527100, C264S251000
Reexamination Certificate
active
06404728
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and method for driving an objective lens used to record/reproduce information with reference to an optical disk, such as a CD (Compact Disk), a CD-RW (CD-ReWritable), a DVD-ROM (Digital Versatile Disk Read Only Memory) and a DVD-RAM (DVD-Random Access Memory).
In recent years, there is an increasing demand for flat-type optical disk recording/reproducing apparatuses (optical disk apparatuses). To provide such apparatuses, very strict requirements are imposed on the design of an objective lens driving apparatus which is used for recording/reproducing information with reference to an optical disk.
For example, in the case of an objective lens driving apparatus suitable for use in a ½-size optical disk having a height of 12.7 mm, the distance between the surface of the optical disk and the bottom surface of the objective lens driving apparatus must be shorter than 7.3 mm. Since the objective lens driving apparatus is installed in a restricted space, such as the space in a jacket-size apparatus or the space in a note book-included apparatus, the size of the objective lens driving apparatus is restricted in the horizontal direction as well.
In addition to the above, the objective lens driving apparatus is required to satisfy the requirements of a DVD disk, the integration density of which is seven times higher than that of an CD.
In the DVD optical system, the objective lens driving apparatus has to be very small in size and yet it must be provided with an acceleration generating function so as to ensure reliable data reproduction even when the disk is rotating fast. The objective lens driving apparatus must be also provided with such frequency characteristics as will satisfy wide-band servo specifications, because the waving and eccentricity of the disk occur at higher frequencies due to the fast rotation of the disk.
A CD system (CD×1) and a DVD system (DVD×1) will be compared with each other. (The “×1” is a standard transfer speed for audio CDs.)
(1) Number of Rotations
CD×1: 3.3 to 8.3 Hz
DVD×1: 9.6 to 23.1 Hz
(2) Allowable Limit Values in Focusing Direction
{circle around (9)} Waving Amount (Rotation Synchronization)
CD×1: ±0.5 mm
DVD×1: ±0.3 mm
{circle around (2)} Waving Acceleration
CD×1: 10 m/s
2
DVD×1: 8 m/s
2
{circle around (3)} Allowable Residual Error
CD×1: ±1 &mgr;m
DVD×1: ±0.23 &mgr;m
(3) Allowable Limit Values in Tracking Direction
{circle around (1)} Eccentricity (Rotation Synchronization)
CD×1: ±70 &mgr;m
DVD×1: ±35 &mgr;m
{circle around (2)} Eccentricity Acceleration
CD×1: 0.4 m/s
2
DVD×1: 1.1 m/s
2
{circle around (3)} Allowable Residual Error
CD×1: ±0.1 &mgr;m
DVD×1: ±0.022 &mgr;m
{circle around (4)} Allowable Tilt of Objective Lens
CD×1: ±5 mrad
DVD×1: ±2 mrad
As can be understood from the above comparison, the characteristics regarding the waving and eccentricity of the DVD system are improved; their figures are 0.5-0.6 of those of the CD system. In spite of this, however, the allowable residual error of the DVD system is less than ¼ of that of the CD system. This means that, due to the use of the servo system adopted, the accuracy required of the DVD system is twice as high as that of the CD system. Therefore, the high-frequency characteristic of the objective lens driving system must be expanded double, and the oscillation system including a secondary resonating unit and the electromagnetic driving system must be greatly improved, accordingly. When the rotating speed of a disk is increased, the electromagnetic driving system is required to use power with remarkably high efficiency, since the acceleration increases in proportion to the square of the number of rotations.
In the CD system, the allowable tilt of the objective lens can be realized without imposing severe restrictions on the manufacture of the CD system. In the DVD system, however, the allowable tilt of the objective lens cannot be easily realized and poses a lot of problems in the manufacture of the system, particularly when mass production of systems is considered. If the objective lens tilts, the parallelism of the objective lens to the surface of the optical disk is adversely affected. If this happens, an RF signal derived from a reflected beam from the disk decreases in level in accordance with an increase in the tilt angle, so that the reproduction or recording of data with reference to the optical disk may not be executed.
BRIEF SUMMARY OF THE INVENTION
As described above, the transition to the DVD system requires an objective lens driving apparatus which is highly sensitive, covers a wide frequency range and hardly tilts, and which can be provided in a very restricted space. However, such an objective lens driving apparatus cannot be easily designed by utilizing the structure of the conventional CD system or the conventional manufacturing system. In other words, the conventional technology regarding the CD system is not very useful in producing the required objective lens driving apparatus.
Accordingly, an object of the present invention is to provide an objective lens driving apparatus which is highly sensitive, covers a wide frequency range and hardly tilts, which can be provided in a very restricted space and which has such a structure as enables further enhancement in performance. Another object of the present invention is to provide a method for manufacturing the objective lens driving apparatus.
[I] According to the first aspect of the present invention, there is provided a method for manufacturing an objective lens driving apparatus comprising: a lens holder which holds an objective lens and is driven in a focusing direction and a tracking direction with reference to the optical disk; at least two wires having first ends secured to the lens holder and controlling posture of the lens holder; and a wire holder to which second ends of the wires are fixed, the method comprising the steps of: preparing a first integrally molded member including the lens holder and the wire holder which are connected together by a holder connecting frame to be removed after assembly; preparing second integrally molded member each including the wires which are suspended from a wire holding frame to be removed after assembly; positioning the second integrally molded members relative to the first integrally molded member such that the first ends of the wires are connected to the lens holder and the second ends of the wires are connected to the wire holder; and removing the wire holding frame and the holder connecting frame.
With this structure, since the lens holder and the wire holder are prepared as one integrally molded member, the wires can be attached to them in such a manner that the positional relationships which they have immediately after they are molded are maintained. Moreover, since the wires suspended by the wire holding frame are prepared as integrally molded members, the wires, even though they are thin, can be easily assembled without damage.
According to one embodiment, the wires, the lens holder and the wire holder are positioned relative to one another by bringing the holder connecting frame into contact with the wire holding frame.
[II] According to the second aspect of the present invention, there is provided an objective lens driving apparatus incorporated in an optical disk apparatus which is for recording or reproducing information from an optical disk, the objective lens driving apparatus comprising: a lens holder which holds an objective lens and is driven in a focusing direction and a tracking direction with reference to the optical disk; at least two wires having first ends secured to the lens holder and controlling posture of the lens holder; and a wire holder to which second ends of the wires are fixed, the wires being suspended by a wire holding frame which is to be removed after assembl
Kawakami Hiroshi
Murayama Tomohiro
Shinozuka Hiroshi
Tateishi Taizo
Wakabayashi Tomomi
Kabushiki Kaisha Toshiba
Klimowicz William
Pillsbury & Winthrop LLP
LandOfFree
Apparatus and method for driving objective lens does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method for driving objective lens, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method for driving objective lens will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2917947