JPH03100933A - Lens driving device - Google Patents

Abstract

PURPOSE:To prevent sliding and rotating characteristic from being degraded by worn particles and foreign materials mixed between a support shaft and a bearing, to hardly receive the influence of air viscosity when the band of a servo characteristic is made high, and to stablize the servo characteristic by providing a groove in the support shaft or the bearing. CONSTITUTION:The base of operation is same as normal operation and by the flow of a control current to a coil 10 for focus control, a lens holder 3 is driven in a focus control direction (A direction) along a support shaft 5. Then, the control current is caused to flow to coils 11a and 11b for track control and the holder 3 is turned around the support shaft 5 as a center and driven in a track control direction (B direction). Thus, in this method, a groove part 4a is newly provided in a bearing 4 and the worn particles or dust X to be generated by the frictional force of the support shaft 5 and the bearing 4 goes into the groove part 4a and is discharged from a sliding part 4b to an external part. Even when the support shaft 5 and the bearing 4 are driven at high speed with the clearance of several microns, the influence of the air viscosity is hardly received by the groove part 4a.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a lens driving device, and is particularly suitable for improving the controllability of a lens for forming a light spot used in an optical head in an optical information recording/reproducing device. The present invention relates to a lens driving device.

[Prior Art] FIG. 6 is an exploded perspective view of a conventional lens driving device. In the figure, (1) is an objective lens for forming a laser beam spot on an optical information recording medium (not shown);
3) is a lens holder for holding an objective lens (1), which has a cylindrical bearing (4) in its center and is slidably and rotatably held by a support shaft (5).

Here, the clearance between the support shaft (5) and the bearing (4) causes the objective lens to tilt with respect to the optical axis, deteriorating the optical characteristics, so it is designed to be as small as possible without deteriorating the sliding and rotation characteristics. has been done. (2) is a counterweight for balancing the objective lens (1) on the lens holder (3) and the support shaft (5), and (6) is a support that elastically holds the lens holder (3). Rubber, (7) is a permanent magnet for focus control to slide the lens holder (3) in the direction of the arrow along the spindle (5), (8a) and (8b) are the lens holder (3). A truck is rotated in the direction of arrow B around the support shaft (5) @ Goyo Mizuku magnet, (9) is the support shaft (
5) and a focus control yoke that holds the focus control permanent magnet (7), (10) is attached to the lens holder (3) and is attached to the lens holder (3) by the magnetic force between the focus control permanent magnet (7). focus control coils (11a), (flb) that apply a driving force in the focus control direction along the support axis (5) to the objective lens (1) and, as a result, move the objective lens (1) in the focus control direction;
gives the lens holder (3) a rotational force about the support shaft (5) by the magnetic force acting between the track control permanent magnets (8a) and (8b), and as a result, the objective lens (1)
(12a), (12b) are track control yokes that adhesively fix track control permanent magnets (8a), (8b), (13a), (13b), (13c)
, (13d) is a track control yoke (12a),
Support rubber (6) that is integrally molded with the fixing base (14) and holds the lens holder (3) together with (12b)
The supporting rubber mounting part (15) is the fixing base (14) that fixes the
This is a hole through which the laser beam is guided to the objective lens (1).

The operation of the above configuration will now be described.

Now, when the objective lens (1) is out of focus with respect to an optical recording medium (not shown), a control current corresponding to the amount of defocus is supplied to the focus control coil (1o) from the defocus detection means (not shown). Ru. As a result, a magnetic force acts between the focus control coil (10) and the focus control permanent magnet (7), and the lens holder (3) moves in the direction of the arrow along the support shaft (5), that is, the objective lens ( 1) It is slidably driven in the focus control direction. The focus of the objective lens (1) is then optimally controlled.

On the other hand, when the objective lens (1) causes a track deviation with respect to an optical recording medium (not shown), the track control coil (lla) is detected by a track deviation detection means (not shown).
A control current corresponding to the amount of track deviation is supplied to (llb). As a result, the track control coil (lla),
(llb) and a track control yoke (12a),
Track control permanent magnet (8) attached to (12b)
A magnetic force acts between a) and (8b), and the lens holder (
3) is rotationally driven in the direction of arrow B around the support shaft (5). The objective lens (1) is then driven in the track control direction to optimally control the track.

The support rubber (6) elastically supports the lens holder (3), and when the focus control coil (10) is turned off, the lens holder (3) returns to the neutral state in the focus control direction. hold a dispute. On the other hand, when the track control coils (lla) and (flb) are de-energized, the lens holder (3) is rotated to return to the neutral state in the track control direction and held.

As described above, a light beam from a light emitting device (not shown), such as a semiconductor laser, on the hole (15) side is formed into a spot on an optical information recording medium (not shown) through the objective lens (1) which is focus-controlled and track-controlled. and optically write or read information.

[Problems to be Solved by the Invention] Since the conventional objective lens drive device is configured as described above, the support shaft (5) and the bearing (4) are moved by sliding and rotating the lens holder (3). There was a risk that the sliding and rotational characteristics would deteriorate due to abrasion powder adhering between the two or foreign matter getting mixed in. Also, when increasing the bandwidth of the servo characteristics,
Due to the increased circumferential speed, the viscosity of the air that exists in the minute clearance between the support shaft (5) and the bearing (4) is affected,
The problem was that stable servo characteristics could not be obtained.

Purpose of the Invention The present invention was made to solve the above-mentioned problems, and it prevents deterioration of sliding and rotational characteristics due to abrasion powder and foreign matter mixed between the spindle and the bearing, and also prevents the spindle from deteriorating. It is an object of the present invention to provide a lens driving device that can obtain stable high-band servo characteristics by making it less susceptible to the influence of air viscosity existing in minute clearances between bearings.

[Means for Solving the Problems] A lens driving device according to the present invention holds an objective lens, has a bearing in the center, and is slidably and rotatably fitted to a support shaft via the bearing. a fixed base on which the support shaft is erected, and driving means for rotating and moving the holder up and down in the axial direction, and driving the lens holder;
An objective lens driving device capable of controlling track deviation and defocus of a spot focused on a disk via the objective lens, which has a groove formed in at least the support shaft or bearing.

[Function] According to the lens driving device of the present invention, by the above means, abrasion powder and foreign matter mixed between the spindle and the bearing enter the groove and are removed from the sliding portion, thereby preventing deterioration of sliding rotation characteristics. can be prevented. Furthermore, since the bearing is provided with grooves, even if the circumferential speed increases, the bearing is less susceptible to the effects of air viscosity, and stable high-band servo characteristics can be obtained.

[Example] Hereinafter, an example of the present invention will be described based on FIGS. 1 to 3. FIG. 1 is an exploded perspective view of an objective lens driving device according to an embodiment of the present invention, FIG. 2 is a plan view of FIG. 1,
FIG. 3 is a partially enlarged view of the support shaft and bearing portion of FIG. 1.

In the figure, the bearing (4) has a straight shallow groove on its inner surface, and its outer periphery is adhesively fixed to the center of the lens holder (3). Here, the bearing (4) and the support shaft (5) are precisely machined, and the clearance between the support shaft (5) and the bearing (4) in the sliding portion (4b) is several microns. The bearing (4) also has a groove (4b) adjacent to the sliding part (4b).
4a) is formed.

The rest of the configuration is the same as the conventional configuration shown in FIG. 6, so a description thereof will be omitted.

Next, the operation will be explained. The basic operation in one embodiment is the same as in the conventional case, and the focus control coil (1
By applying a control current to the lens holder (0), the lens holder (
3) is driven in the sliding direction, that is, the focus control direction (direction A) along the support shaft (5). On the other hand, a track control coil (11a).

By applying a control current to (llb), the lens holder (3) rotates around the support shaft (5).

That is, it is driven in the track control direction (direction B).

By being driven in the focus control direction and the track control direction as described above, frictional force acts on the support shaft (5) and the bearing (4), producing friction powder.

However, as shown in FIG.
) is removed to the outside. In addition, the support shaft (5) and bearing (4)
) with a clearance of a few microns, even when driven in the focus control direction and track control direction at high speed.
Since the groove portion (4a) is provided, it is less susceptible to the influence of air viscosity, and the sliding and rotation characteristics are not adversely affected.

In the above embodiment, the bearing (4) has a straight groove, but as shown in the cross section of FIGS. It goes without saying that a spiral groove (Fig. b), a T-shaped groove (Fig. 0), etc. may be provided.

In addition, as shown in Figure 5, the support shaft side has an arc-shaped straight groove (Figure a), a circumferential groove (Figure b), and a spiral groove (Figure 0).
(Fig.) or a dogleg-shaped groove (Fig. d) may be added.

Furthermore, the above-mentioned grooves may be provided on both the support shaft and the bearing.

[Effects of the Invention] As described above, according to the present invention, since the groove is provided on the support shaft or bearing, it is possible to prevent deterioration of sliding and rotational characteristics due to abrasion powder and foreign matter mixed between the support shaft and the bearing. Even if the servo characteristics are made to have a high bandwidth, stable servo characteristics can be obtained regardless of the influence of air viscosity.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of a lens driving device according to an embodiment of the present invention, FIG. 2 is a plan view of FIG. 1, and FIG. 3 is a portion of a support shaft and bearing portion according to an embodiment of the present invention. Enlarged view, 4th
5 and 5 are views showing other embodiments, and FIG. 6 is an exploded perspective view showing a conventional lens driving device. In the figure, (1) is the objective lens, (2) is the counterweight, (3) is the lens holder, (4) is the bearing, (4) is the
(a) is a groove, (4b) is a sliding part, (5) is a support shaft, (7) is a permanent magnet for focus control, (8a). (8b) is a permanent magnet for track control, (9) is a yoke for focus control, (10) is a coil for focus control, (lla),
(llb) is a track control coil, (12a),
(12b) is a track control yoke, and (13) is a fixed base. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] a lens holder that holds an objective lens, has a bearing in the center, and is slidably and rotatably fitted to a support shaft via the bearing; a fixing base on which the support shaft is erected; An objective lens comprising a driving means for rotating the holder and moving the holder up and down in the axial direction, and driving the lens holder to control the track deviation and defocus of the spot focused on the disk via the objective lens. A lens driving device characterized in that the driving device has a groove formed in at least the support shaft or the bearing.