Optical: systems and elements – Lens – With support
Reexamination Certificate
2000-08-28
2001-09-11
Mack, Ricky (Department: 2873)
Optical: systems and elements
Lens
With support
C359S814000, C359S824000
Reexamination Certificate
active
06288853
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a so-called shaft sliding type optical pickup device.
A related shaft sliding type optical pickup device is disclosed in Japanese Patent Publication No. 6-79383B. In such an optical pickup device; a lens holder holding an objective lens is attached rotatably and slidably to a support shaft mounted on a frame and a driving coil is attached to the lens holder and a member on one of sides of the frame, and a magnet is fixed to a member on the other side opposite to the driving coil in a radial direction. A control current is sent in a proper timing with respect to the driving coil. Consequently, the whole lens holder including the objective lens is controlled and moved in a focusing direction (an axial direction) and a tracking direction (a rotating direction).
In such a related shaft sliding type optical pickup device, a magnet for focusing and a magnet for tracking are required. In the related device described, a single magnet
1
is polarized and magnetized (double-pole magnetized) in the focusing direction (vertical direction) and the tracking direction (transverse direction) as shown in FIG.
5
.
On the other hand, a magnetic piece
2
is attached to the lens holder opposite to the magnet
1
as shown in
FIG. 6
, for example. The magnetic piece
2
is provided in a magnetic circuit using the magnet
1
. Thus, a magnetic spring structure is constituted. Consequently, the objective lens is held in each of neutral positions in the focusing direction and the tracking direction.
Such a related device has two kinds of magnets
1
, that is, a magnet for focusing and a magnet for tracking. Therefore, driving coils should be provided to face the magnets, respectively. For this reason, a reduction in a size and thickness is impeded. On the other hand, in the case in which two kinds of magnets are shared as a single magnet, the arrangement of the magnetic piece becomes a problem.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an optical pickup device capable of obtaining an excellent magnetic spring structure also in the case in which two kinds of magnets are shared as a single magnet.
In order to achieve the above object, according to the present invention, magnetic pieces are provided in the vicinity of both edge portions in the focusing direction of the magnet respectively. Thus, the lens holder is held in the neutral position in which the magnetic attractions for both magnetic pieces are balanced. On the other hand, the magnetic pieces are provided in the almost central portion of the magnet in the tracking direction (rotating direction). Therefore, the magnetic piece is attracted by a magnetic attraction and is held in the almost central portion of the magnet which is the closest to the magnet in the locus of the tracking movement (rotation) of the magnetic piece.
In particular, when the magnetic piece on one of the sides gets out of the facing region of the magnet and the magnetic piece on the other side enters an facing region on the central side of the magnet during a control operation in the focusing direction, a great magnetic attraction acts on the magnetic piece on one of the sides which gets out of the facing region of the magnet. Consequently, the whole lens holder is stably returned to a neutral position by the action force. The lens holder cannot be returned to the neutral position only by the magnetic piece on the other side which enters the facing region on the central side of the magnet.
In order to attain the advantageous effect, preferably, each of the magnetic pieces is arranged such that an end portion thereof in the focusing direction is almost coincident with the end portion in the focusing direction of the magnet when the lens holder is held in the neutral position.
Alternatively, each of the magnetic pieces is arranged such that a central portion thereof in the focusing direction is almost coincident with the end portion in the focusing direction of the magnet when the lens holder is held in the neutral position.
If each of the magnetic pieces is arranged so as to face the magnet within a whole control movement range in the focusing direction, the return force into the neutral position is always maintained to be almost equal. Therefore, it is possible to obtain a very stable focusing control operation.
If it is configured that an interval of the magnetic pieces in the focusing direction is determined in accordance with a desired magnetic spring characteristic, it is possible to easily obtain an appropriate configuration corresponding to various conditions of the device to be used.
REFERENCES:
patent: 4687296 (1987-08-01), Terayama et al.
patent: 5182738 (1993-01-01), Yoshikawa
patent: 5815328 (1998-09-01), Makita
patent: 5901133 (1999-05-01), Miyamae et al.
patent: 5920437 (1999-07-01), Shirotori
patent: 3-104026-A (1991-05-01), None
patent: 6-79383 (1994-10-01), None
Kabushiki Kaisha Sankyo Seiki Seisakusho
Mack Ricky
Sughrue Mion Zinn Macpeak & Seas, PLLC
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