Optical pickup device

Details Optical pickup device Optical pickup device

1999-06-23

2001-11-13

Epps, Georgia (Department: 2873)

Optical: systems and elements

Lens

With support

C359S814000, C359S824000, C369S044150

Reexamination Certificate

active

06317277

ABSTRACT:

This invention claims the benefit of Japanese Patent Application No. 10-177730, filed on Jun. 24, 1998, which is hereby incorporated by reference.
FIELD OF THE INVENTION
The present invention relates to an optical pickup device, and more particularly, to a structure of an actuator of an optical pickup device used in an optical disk drive player or recorder.
DESCRIPTION OF THE RELATED ART
Conventionally, optical pickup devices have been used for reading information recorded in pit patterns on an optical disc. A pickup device of this kind includes a laser source for emitting a light beam, a beam splitter that splits the light beam, an objective lens that focuses a light beam from the beam splitter to an optical disc surface, and a photo detector that receives the light beam reflected from the disc surface. In order to pick up pit patterns recorded on a disc surface, it is necessary to perform a focusing and a tracking operation. Therefore, the pickup device is usually equipped with an actuator, a part of which is flexibly supported with respect to a base by suspension, and on which driving coils are attached to give magnetic force in both focusing and tracking directions, i.e., directions of the focusing and the tracking operation. The actuator includes a lens holder on which the objective lens is mounted, suspension supports, focusing and tracking coils, and a magnetic circuit.
FIG. 4
shows an example of a conventional optical pickup device. In the pickup device of
FIG. 4
, a lens holder
101
, on which an objective lens
102
is mounted, has a ring-shaped flange
101
a
. The lens holder
101
is flexibly supported by two pairs of suspension spring bars
103
, which are positioned in parallel on both sides of the holder
101
. For each pair of suspension spring bars
103
, one end of the suspension spring bars is attached to the holder
101
, while the other end is attached to a bank
104
a
of an actuator base
104
, such that all of the suspension spring bars form parallel lines.
The lens holder
101
with the flange
101
a
has a hole in which a focusing coil
105
and a pair of tracking coils
106
are attached. The focusing coil
105
has a tube shape with rectangular cross section. One side of the focusing coil is fixed on the inside wall of the hole, and a pair of planar tracking coils
106
are glued onto the opposite side of the focusing coil
105
.
A magnet
107
and a yoke
108
are placed on the actuator base
104
and form a magnetic circuit to give magnetic flux to the focusing coil
105
and the tracking coils
106
. This magnetic circuit is surrounded and protected by the flange
101
a.
In order to avoid undesirable movement of the pickup, such as rolling, a driving plane and the center of mass of the moving portion of the actuator should be as close as possible, ideally identical. However, in the conventional pickup of
FIG. 4
, because the lens is placed far from the driving plain, the flange gets bigger in an opposite direction with respect to the driving plain to balance the weight of the lens.
Accordingly, the prior art pickup device has a problem in that the actuator is large and heavy, thus making the pickup unduly large and heavy. Because of its size and weight, it is difficult to suppress undesirable movement. Because the driving plane is not close to the center of mass, the actuator causes the pickup to roll when it moves. A compact and lightweight optical pickup device is therefore difficult to realize because of the substantial size of the actuator.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to an optical pickup device that obviates one or more of the problems due to limitations and disadvantages of the related art.
It is an object of the present invention to solve the aforementioned problems by providing an optical pickup device with a compact actuator that minimizes the size and weight of the optical pickup device.
Additional features and advantages of the invention will be set forth in the description which follows and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, an optical pickup device of the present invention includes a holder which contains an objective lens and a hole, the holder being supported flexibly to a base; a focusing coil and a tracking coil that are partially attached to the hole; and a magnetic circuit which gives magnetic flux to the focusing and the tracking coils being placed in the hole; wherein the focusing and the tracking coils have magnetically fluxed and unfluxed portions, and wherein the magnetically unfluxed portions are positioned on the opposite side of the lens with respect to the fluxed portion.
In another aspect, an optical pickup device includes a holder that contains an objective lens and a hole, the holder being supported flexibly to a base; a bobbin on which wires are wound to form a focusing coil and a tracking coil, the bobbin being attached to the holder; and a magnetic circuit which gives magnetic flux to the focusing and the tracking coils; wherein the focusing and the tracking coils have magnetically fluxed and unfluxed portions, and wherein the magnetically unfluxed portions are positioned on the opposite side of the lens with respect to the fluxed portion.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.


REFERENCES:
patent: 5446721 (1995-08-01), Sekimoto et al.
patent: 5521762 (1996-05-01), Tomiyama et al.

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