JP2656081B2 - Objective lens drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device, and controls, for example, a track shift and a focus shift of an optical spot focused on an information recording surface of an optical disk. Playback device,
The present invention relates to an objective lens driving device which can be particularly preferably used for a recording device or a recording / reproducing device.

[Conventional technology]

As a conventional objective lens driving device, there is one shown in FIG. 6 to FIG.

In the figure, (1) is an objective lens, (2) is a counterweight, and (3) holds the objective lens (1) and the counterweight (2), and has a movable bearing (3a) and a focus control coil bobbin ( 3b). A support shaft (4) supports the lens holder (3) rotatably and slidably in the axial direction via the movable bearing (3a). (5) is a damper for holding the lens holder (3), (6) is a permanent magnet for focus control, (7a) and (7b) are permanent magnets for track control,
(8) is a yoke that also serves to hold the support shaft (4) and the focus control permanent magnet (6), (9a) and (9b) are track control yokes, (10) is a focus control coil, and (11a). (11b) is a track control coil, (12a) and (12b) are dampers (5)
Is fixed to the damper fixing pin, (13) is a fixing stand that supports the damper fixing pins (12a) and (12b) upright,
(14) is a dustproof cover. The track control permanent magnets (7a) and (7b) and the track control yoke (9a)
(9b) and the track control coils (11a) and (11b) constitute a track control drive device. Also,
Focus control permanent magnet (6) and focus control yoke (8)
And the focus control coil (10) constitute a focus control drive device.

In the objective lens driving device having the above-described configuration, the lens holder (3) is supported on the support shaft (4) via the cylindrical movable bearing (3a), so that the lens holder (3) is supported by the support shaft (4). 8), that is, slidably supported in the direction of arrow B in FIG. 8, and rotatably supported about the support shaft (4) in the direction of arrow A in FIG. . Here, by passing a desired current through the focus control coil (10), the lens holder (3) can be moved in the direction of arrow B to perform focus control on a recording medium (not shown). ,
The objective lens (1) is located at a predetermined distance from the support shaft (4)
Is fixed to the lens holder (3), a desired current is applied to the track control coils (11a) and (11b), and the objective lens (1) is rotated in the direction of arrow A to perform track control. Can be performed.

[Problems to be solved by the invention]

The conventional objective lens driving device is configured as described above. The movable bearing (3a) and the support shaft (4) have a gap of, for example, about 10 μm. Therefore, assuming that the length of the movable bearing (3a) is about 5 mm, the objective lens (1) may be inclined at a maximum of about ± 2 mrad as shown in FIGS. 9 (a) and 9 (c). The inclination of the objective lens (1) is one of the causes of deteriorating the reliability of the optical spot.
This is a problem that must be improved in order to increase the recording density of an optical disk device or the like. In addition, the above-mentioned gap is a non-linear element of the objective lens driving device, like friction, and is one of the factors that deteriorate the responsiveness of the objective lens driving device.

However, the above-mentioned gap is a value determined from the mechanical accuracy of the movable bearing (3a) and the support shaft (4), and is indispensable for machining. Therefore, it is very difficult to reduce the size of the gap in order to solve the problem caused by the gap.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide an objective lens driving device which is less affected by a gap, has good responsiveness, and can improve recording density.

[Means for solving the problem]

An objective lens driving device according to the present invention includes a lens holder for holding an objective lens, and the lens holder movably supported in the optical axis direction of the objective lens and rotatably supported in a plane perpendicular to the optical axis. A support shaft made of a magnetic material,
A driving device for driving the lens holder in the optical axis direction and a direction perpendicular to the optical axis direction; and a permanent magnet disposed between the lens holder and the support shaft.

[Action]

In the objective lens driving device of the present invention, the permanent magnet and the support shaft form a magnetic circuit independent of the drive device, and the magnetic force generated by the magnetic circuit presses the lens holder in a direction perpendicular to the support shaft. The operation is the same as when the gap between the support shaft and the lens holder is substantially zero.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a partial sectional view for explaining an embodiment of the present invention. In the figure, reference numeral (15) denotes a permanent magnet, which is a lens holder (3), and accordingly, a movable bearing (3a).
The lens holder (3) is installed in a resin molded form so that a preload due to magnetic attraction force is applied between the lens holder (4) and the support shaft (4). Here, as the material of the support shaft (4), a magnetic material such as iron is used. Also, in this case,
The permanent magnet (15) and the support shaft (4) constitute a magnet device (16). Note that the members denoted by the same reference numerals as those in the conventional example indicate the same or corresponding members as those in the conventional example, and thus the description thereof will be omitted.

The above embodiment is configured as described above, and thus operates as shown in FIG. That is, as shown in FIG. 2 (a), since a magnetic attraction force acts on the movable bearing (3a) and the support shaft (4), the two are always in contact on a certain line. There is no backlash and the objective can be maintained both when the lens holder (3) moves downward as shown in FIG. 2 (a) and when it moves upward as shown in FIG. 2 (c). The lens (1) does not tilt as in the conventional device shown in FIG. Therefore, a highly reliable optical spot can be obtained, and the recording density can be improved.
Also, since there is no backlash, an objective lens driving device having good responsiveness can be obtained.

FIG. 3 shows a second embodiment according to the present invention. In this embodiment, the preload permanent magnets (15a) and (15b) are provided on the upper and lower surfaces of the lens holder (3). It goes without saying that this configuration also has the same effect as the first embodiment.

4 and 5 show a third embodiment according to the present invention. FIG. 4 is a partial sectional view, and FIG. 5 is a detailed view of a main part thereof. In the figure, (15) is a preload permanent magnet, and (16a) and (16b) are movable bearings. In this embodiment, as shown in FIG. 5, the movable bearings (31a) and (31a)
Since b) is provided on the upper end surface and the lower end surface of the lens holder (3), respectively, compared with the first and second embodiments,
The contact area between the movable bearings (31a) (31b) and the support shaft (4) can be made very small. Therefore, the movable bearing (31a) (31b)
The frictional force between the shaft and the support shaft (4) can be reduced, and the same effects as those of the first and second embodiments can be obtained.
Further, an objective lens driving device having good responsiveness can be obtained. The movable bearing (31a) (3
In the case of 1b), it is preferable that the movable bearings (31a) and (31b) are provided with a taper from both upper and lower surfaces in order to eliminate an operation effect due to a snag of an edge portion or the like.

In each of the above embodiments, a permanent magnet (15) is provided on the lens holder (3), a magnetic material is used as the support shaft (4), and the magnet device (15) is provided by the permanent magnet (15) and the support shaft (4). 16)
However, the present invention is not limited to these, and it is sufficient that the lens holder (3) is pressed (including suction) in a predetermined direction with respect to the support shaft (4). In this sense, the permanent magnet (15) may be fixedly provided on the support shaft (4), and the magnetic material attracted by the permanent magnet (15) may be provided on the lens holder (3).

Further, even if permanent magnets are provided on both the support shaft and the lens holder and the attracting force between different poles or the repulsive force between the same poles is used, this is not a problem.

Further, the biasing direction of the lens holder (3) with respect to the support shaft (4) is not limited to the above embodiment.

It goes without saying that various changes and modifications are possible within the spirit of the present invention.

〔The invention's effect〕

As described above, according to the present invention, a lens holder for holding an objective lens, the lens holder is movably supported in the optical axis direction of the objective lens, and is rotatably supported on an inner surface orthogonal to the optical axis. A supporting shaft, a driving device for driving the lens holder in a direction perpendicular to the optical axis direction and a direction perpendicular to the optical axis direction, and a permanent magnet disposed between the lens holder and the supporting shaft. The play between the movable bearing and the support shaft and the inclination of the objective lens during operation can be eliminated with a simple structure, and there is an effect that an objective lens driving device capable of improving responsiveness and improving recording density can be obtained.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a first embodiment of the present invention, and FIG. 2 is a view for explaining the operation of the first embodiment. FIG. 3 is a partial sectional view showing a second embodiment of the present invention, and FIGS. 4 and 5 are views for explaining the third embodiment, and FIG. 4 is a partial sectional view. FIG. 5 is a detailed view of a main part. 6 to 9 are views for explaining an example of a conventional objective lens driving device. FIG. 6 is an exploded perspective view and FIG.
FIG. 8 is a partial plan view, FIG. 8 is a partial cross-sectional view, and FIG. 9 is a diagram for explaining the operation state. In the figure, (1) is an objective lens, (3) is a lens holder, (4) is a support shaft, and (16) is a magnet device. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. A lens holder for holding an objective lens, a support shaft for movably supporting the lens holder in the direction of the optical axis of the objective lens and for rotatably supporting the lens holder in a plane perpendicular to the optical axis. An objective lens driving device comprising: a driving device for driving the lens holder in the optical axis direction and a direction perpendicular to the optical axis direction, wherein the objective lens driving device records and reproduces information on an optical disk via the objective lens. A permanent magnet is arranged between the lens holder and the support shaft made of a magnetic material, and the permanent magnet and the support shaft form a magnetic circuit independent of the driving device, and are generated by the magnetic circuit. An objective lens driving device, wherein a magnetic force presses the lens holder in a direction perpendicular to the support shaft.