JPH03113731A - Objective lens driver - Google Patents

Abstract

PURPOSE:To realize sliding-rotating operation by applying variable pre-load in a direction intersecting the direction of the axial line of a supporting shaft at right angles to the vicinity of the center of gravity of a lens holder. CONSTITUTION:A cylindrical movable shaft bearing 23 is fitted to the supporting shaft 24, and the lens holder 25 is supported freely slidably in the longitudinal direction of the supporting shaft 24, i.e., in the direction of an arrow mark B, and simultaneously, freely turnably in the direction of the arrow mark A around the supporting shaft 24. Further, a pre-loading coil 37a is arranged in a magnetic circuit installed at a fixed side and constituted of pre-loading permanent magnets 35a, 35b and a pre-loading yoke 34a, and by flowing a definite current in this coil 37a, it receives force in the direction of the arrow mark C. The force caused in the coil 37a acts upon the vicinity G of the center of gravity of the movable part. Thus, even if focus control operation is executed, the lens holder 25 operates without causing inclination, and an objective lens 21 also operates as being kept in a state that it intersects a disk surface always at right angles.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to an objective lens driving device, particularly a reproduction device that controls track deviation and defocus of a light spot focused on an information recording surface of an optical disk. The present invention relates to an objective lens driving device for a device or a recording/reproducing device.

[Conventional technology]

As a conventional objective lens driving device, there is one shown in FIGS. 7 to 9, which is called an axial sliding rotation type. 7 to 9, (1) is an objective lens, (2) is a counterweight, (3) is a lens holder having a movable bearing (3a) and a focus control coil bobbin (3b), and (4) is a lens holder having a movable bearing (3a) and a focus control coil bobbin (3b).
) is a support shaft coated with Teflon-based resin as a lubricant, and a movable bearing (3a) is fitted therein so as to be rotatable in the rotational direction and slidable in the axial direction. (5) is a damper that holds the lens holder (3). (6) is a permanent magnet for focus control. (7a) and (7b) are permanent magnets for track control. (8) is a support shaft (4) and a focus control magnet. Permanent magnet (6)
(9a), (9b) are track control yokes, (10) are focus control coils, (9a) and (9b) are track control yokes, (10) are focus control coils, (
11a) (llb) is a track control coil, (15)
is a damper fixing bin for fixing the damper (5), (16
) is a fixed stand on which the damper fixing bin (15) is erected and supported.

In the objective lens drive device having the above configuration, the cylindrical movable bearing (3a) is fitted to the support shaft (4), so that the lens holder (3) is moved in the longitudinal direction of the support shaft (4), that is, as shown in FIG. It is supported to be slidable in the direction of arrow B in FIG. 7, and rotatable about a support shaft (4) in the direction of arrow A in FIG. Here, the lens holder (3) can be moved in the direction of arrow B to perform focus control by passing a desired current through the focus control coil (10). Also, the support shaft (4)
Since the objective lens (1) is fixed to the lens holder (3) at a position where it can be moved a predetermined distance, a desired current is applied to the track control coils (ILa) and (llb).
Track control can be performed by rotating the objective lens (1) in the direction of arrow A.

[Problem to be solved by the invention]

Since the conventional objective lens drive device is configured as described above, when the lens holder (3) slides in the direction of arrow B to correct the defocus as shown in FIG.
5) changes the direction of the force, and the support shaft (4) and bearing (3a
), and there is a problem in that the design of the supporting rubber (5) and the dimensional control of the support shaft and bearing require careful attention. Such a tilt results in a tilt of the objective lens (1), leading to deterioration of recording/reproducing characteristics.

This invention was made to solve the above-mentioned conventional problems, and the lens holder is less likely to tilt even when it slides and rotates for focus control and tracking control, and as a result, the objective lens It is an object of the present invention to provide an objective lens driving device which can obtain stable operation without deterioration of recording/reproducing characteristics since there is no inclination of the object.

[Means for Solving 1 Problem] The objective lens drive device according to the present invention provides variable preload near the center of gravity of the lens holder in a direction orthogonal to the axial direction of the support shaft, thereby improving sliding and rotation. This is to ensure smooth operation.

[Effect 1] In this invention, since force is always applied in the direction perpendicular to the support shaft and the support shaft and bearing slide and rotate, the objective lens does not tilt due to focus control or tracking control operations. . Therefore, stable recording/reproducing characteristics can be achieved. Furthermore, since the direction and force of the preload can be varied, the point of contact between the support shaft and the shaft can be changed. For this reason,
The wear points of the lubricant on the spindle can be distributed, making it possible to realize a long-life device.

[Embodiment J] An embodiment of the present invention will be described below with reference to FIGS. 1 to 5. Figure 1 is a plan view, Figure 2 is the line from Figure 1 ■-■
3 is a perspective view of the main part, and FIGS. 4 and 5 are operation explanatory views. In the figure, (21) is an objective lens, (22) is a balancer, (25) is a lens holder having a bearing (23) and holding the objective lens (21), (2
4) is a support shaft coated with Teflon-based resin, and the bearing (23) is fitted therein so as to be rotatable in the rotational direction and slidable in the axial direction. (33) is a damper that holds the lens holder (25). (26) is a permanent magnet for focus control. (27a) and (27b) are permanent magnets for track control. (29) is a support shaft (24) and a focus control magnet. A yoke that also serves as a retainer for the permanent magnet (26), (30) another focus control yoke, (28a) and (28b) a track control yoke, and (31) a focus control coil (3).
2a) and (32b) are track control coils, (37
a), (37b), (37c) are lens holders (25)
Preload coils fixed to (35a), (35b
), (35c) and (36a), (36b), (36c
) are preload magnets, (34a), (34b), (34
c) is a preload yoke, which is fixed to a support stand (not shown).

Next, the operation will be explained. In the objective lens drive device having the above configuration, the cylindrical movable bearing (23) is fitted to the support shaft (24), so the lens holder (25) is attached to the support shaft (24).
) is slidably supported in the longitudinal direction of arrow B in FIG.
4) is rotatably supported around the center. Here, by passing a desired current through the focus control coil (31), the lens holder (25) can be moved in the direction of arrow B to perform focus control. In addition, since the objective lens (21) is fixed to the lens holder (25) at a position a predetermined distance from the support shaft (24), the track control coil (32)
Track control can be performed by turning the objective lens (21) in the direction of arrow A by applying a desired current to a) and (32b).

Further, in the objective lens driving device of the present invention, preload magnetic circuits for preloading are provided at three locations. That is, as shown in Fig. 3, a preload coil (37a) is placed in a magnetic circuit consisting of preload permanent magnets (35a), (36a) provided on the fixed side and a preload yoke (34a), and this coil (37a
) receives a force in the direction of arrow C shown in FIG. The force generated in the preload coil (37a) is arranged so as to act on G near the center of gravity of the movable part. Therefore, even if the focus control operation is performed in the direction of arrow B, the lens holder (25) operates without tilting, and the objective lens (2) provided on the lens holder (25)
1) also always operates perpendicular to the disk surface. The above-mentioned preload acts not only in the direction of arrow C in FIG. 2, but also in the direction of arrow E and in the direction of arrow E as shown in FIG. 4 since preload devices are provided at three locations. Moreover, these preload coils (37a), (37b), (3
The force generated in 7c) is the force generated in coils (37a) and (37b).
, (37c) because it is variable depending on the current value applied to it.
As shown in FIG. 5, the contact point between the support shaft (24) and the bearing (23) can be changed in any direction throughout the gap. Therefore, the locations where the lubricant on the support shaft (24) is worn out can be distributed, and a long-life device can be realized.

FIG. 6 is for explaining another embodiment of the present invention, in which (51a), (51b), (51c)
) are wires, and (52a), (52b), and (52c) are piezoelectric elements. In this embodiment, wires (51a), (51b), extending in three directions from the center of the support shaft (24),
The tip of (51c) is connected to piezoelectric elements (52a), (52b),
(52C), piezoelectric elements (52a), (52b)
By driving (52c), preload can be generated over the entire circumference. In this case as well, the same effects as in the above embodiment can be achieved.

[Effects of the Invention] As described above, according to the present invention, preload can be applied between the support shaft and the bearing in the direction perpendicular to the support shaft, so that sliding and rotation for focus control and track control can be performed. It is possible to prevent the movable part from making unnecessary movements due to movement or disturbance. Furthermore, dimensional control of the support shaft and bearings is relaxed. In addition, since the contact points between the spindle and the bearing can be varied, the wear points of the lubricant on the spindle can be dispersed, resulting in a longer life.

[Brief explanation of drawings]

FIG. 1 is a plan view of an embodiment of the present invention, FIG. 2 is a sectional view taken along the line ■--■ in FIG. 1, FIG. 3 is a perspective view of the preload device shown in FIG. 1, and FIGS. The figure is an operation explanatory diagram, and FIG. 6 is a partial plan view for explaining another embodiment of the present invention.
FIG. 7 is a plan view of a conventional objective lens driving device, FIG. 8 is a sectional view taken along line 1--2 in FIG. 7, and FIG. 9 is a partially exploded perspective view. In the figure, (21) is an objective lens, (22) is a balancer, (23) is a bearing, (24) is a support shaft (25) is a lens holder, (26) is a focus control magnet, (27a), (
27b) is a track control magnet, (28a), (28b)
) is a track control yoke, (29), '(30) is a focus control yoke, (31) is a focus control coil, (32)
a). (32b) is a track control coil, (33) is a damper (34a), (34b), (34c) is a preload yoke, (35a), (35b). (35c), (36a), (36b), (36c) are preload magnets, (37a) (37b) (37c) are preload coils.

Claims (1)

[Claims] (1) A lens holder rotatably and slidably held on a support shaft, an objective lens provided on the lens holder at a position eccentric from the support shaft, and the lens holder slidably and rotated. An objective lens drive device comprising a drive device for focus control and track control of a light spot on an optical information recording medium, wherein a portion of the lens holder is provided so that the lens holder is orthogonal to the axial direction of the support shaft. An objective lens drive device comprising a plurality of preload devices that generate force variable in direction.