JPH0682471B2 - Objective lens drive - Google Patents

Description

The present invention relates to an objective lens driving device, and more particularly to controlling track deviation and defocusing of a light spot focused on an information recording surface of an optical disc. The present invention relates to an objective lens driving device of a reproducing device or a recording / reproducing device.

[Prior Art] FIGS. 5 to 7 show a conventional objective lens driving device. FIG. 5 is an exploded perspective view, FIG. 6 is a longitudinal sectional view in an assembled state, and FIG. 7 is a lens holder part. FIG.

In the figure, (1) has an objective lens, (2) has a counterweight, (3) has a cylindrical bearing (3a), and the objective lens (1) and the counterweight are placed at symmetrical positions of the bearing (3a). The lens holder for holding (2), (4) the bearing (3a) of the lens holder (3) is slidable in the axial direction of arrow A in FIG. 6 and rotatable in the direction of arrow B in FIG. A support shaft fitted to the support shaft, (5) supporting rubber for holding the lens holder (3), (6a) and (6b) permanent magnets, (7a),
(7b) is a yoke, (8) is a spindle (4) and a permanent magnet (6
a), a yoke also serving as a holding base for (6b), (9) a fixed base for the supporting rubber (5), and (10) a focus control attached to the lens holder (3) concentrically with the bearing (3a). Coil for
(11a), (11b), (11c), (11d) are track control coils attached to the outer periphery of the focus control coil (10) via an electric insulating layer (not shown), (12a), (12b) Is a fixing screw for attaching the support rubber (5) to the fixing base (9), (13) is a cover, and (14) is a coil holder for holding the coil.

Next, the operation will be described. By supplying a desired current to the focus control coil (10), the lens holder (3) slides in the direction of arrow A to perform focus control.

In addition, the track control coils (11a), (11b), (11
By supplying a desired current to c) and (11d), the lens holder (3) rotates in the direction of arrow B and is fixed at the position of the lens holder (3) which is a predetermined distance from the support shaft (4). The objective lens (1) is rotated to perform track control.

[Problems to be Solved by the Invention] Since the conventional objective lens driving device is configured as described above, the focus control coil and the track control coil are attached to the lens holder that is the movable portion via the coil holder. It is a moving coil system that is used, and it is necessary to draw a coil wire from the moving part and hold it on the fixed part.

Therefore, the drawn coil wire moves due to the above control operation, and a cutting accident or the like is likely to occur. To prevent this accident such as disconnection, the coil wire should be relayed once to a sturdy lead wire on the moving part, but a sturdy lead wire may disturb the control operation, so there is a large restriction on the selection of the lead wire. Will be given. Further, the pulling out work is a delicate work, and there is a problem that the assembling workability is deteriorated.

The present invention has been made to solve the above problems and eliminates the need for a coil lead wire from a movable portion,
An object of the present invention is to obtain an objective lens driving device which is free from accidents such as breakage of lead wires, has high reliability, and is easy to assemble.

[Means for Solving Problems] In the objective lens driving device according to the present invention, the control coil is arranged on the fixed side and the permanent magnet is arranged on the movable side.

[Operation] In the objective lens driving device according to the present invention, by disposing the control coil on the fixed side, the coil lead wire from the movable part is unnecessary, the control operation by the lead wire is not adversely affected, and the lead wire disconnection accident occurs. As a result, reliability and assembly workability are significantly improved.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. First
1 is a plan view of an objective lens driving device according to an embodiment of the present invention, FIG. 2 is a vertical sectional view taken along line II-II of FIG. 1, FIG. 3 is a perspective view showing a driving portion, and FIG. 4 is a track. It is a schematic diagram for demonstrating the operation | movement by control.

In the figure, (21) has an objective lens, (22) has a cylindrical bearing portion (22a) near the center, and this bearing portion (22a)
A lens holder that fixedly holds the objective lens (21) at a position more eccentric by a predetermined distance, and (23) is concentric with the bearing (22a) below the lens holder (22), and
A ring-shaped permanent magnet fixedly held in a ring portion (22b) provided with a gap (22c), (24) an actuator base that is a fixed portion, and (25) an actuator base (24). The lens holder (22) has a bearing portion (22a) slidably mounted in the center of the lens holder (22) in the axial direction of arrow A in FIG. 2 and rotatable in the direction of arrow B in FIG. The attached support shafts (26a) and (26b) are located outside the permanent magnet (23) and fixedly arranged on the actuator base (24) with a desired gap provided between the support shaft and the permanent magnet. The A / F yoke (27) is disposed between the permanent magnet (23) and the A / F yokes (26a) and (26b), and a desired gap is provided between the permanent magnet (23) and the A / F yokes (26a) and (26b). Focus control coils provided on the inner surfaces of the F yokes (26a) and (26b), (28a) and (28b)
Is located outside the focus control coil (27) and the A / F yoke (2
6A) and (26b) are fixedly arranged on the actuator base (24) so as to be sandwiched between them, and the U-shaped A / T yokes (29a) and (29b) are A / T yokes (28a). , (28b) is a coil for track control wound in the center.

Next, the operation will be described. Since the focus control coil (27) is arranged in the magnetic field formed by the permanent magnet (23) and the A / F yokes (26a) and (26b), a desired current is supplied to the focus control coil (27). The lens holder (22) slides in the direction of arrow A to control the focus of the objective lens (21).

Next, by applying a desired control current I to the track control coils (29a) and (29b), the A / T yokes (28a) and (28
A magnetic field H is generated in b). This magnetic field H is applied to the A / T yoke (28
Both ends (28a) facing the permanent magnet (23) of (a) and (28b)
Since the directions of a), (28ab), (28ba), and (28bb) are different, an imbalance of the magnetic flux density is generated in the permanent magnet (23). Due to this imbalance in magnetic flux density, the permanent magnet (23) rotates about the support shaft (25), and the lens holder (22) moves in the direction of arrow B.
The objective lens (21) is track-controlled by rotating in the direction.

In the magnet movable type objective lens driving device in which the permanent magnet is movable as in the above embodiment, a plastic magnet having a small specific gravity is used as the permanent magnet in order to reduce the mass and the moment of inertia of the movable portion as much as possible. Is preferred.

[Advantages of the Invention] As described above, according to the present invention, the control coil is arranged in the fixed portion and the permanent magnet is arranged in the movable portion. Therefore, a coil lead wire from the movable portion is completely unnecessary. As a result, there is no adverse effect on the control operation of the objective lens driving device due to the lead wire, there is no fear of a disconnection accident or the like due to the control operation, and reliability and assembling workability are improved.

[Brief description of drawings]

1 is a plan view showing an objective lens driving device according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view taken along line II-II of FIG. 1, and FIG. 3 is a perspective view showing a driving portion of FIG. 4 and FIG. 4 are schematic views for explaining the operation in the track control of the objective lens driving device according to the present invention, FIG. 5 is an exploded perspective view showing a conventional objective lens driving device, and FIG. 6 is its assembled state. FIG. 7 is a longitudinal sectional view, and FIG. 7 is an exploded perspective view of the movable holder portion. In the figure, (21) is an objective lens, (22) is a lens holder, (23) is a permanent magnet, (25) is a spindle, (26a), (26
b) is the first fixed yoke (A / F yoke), (27) is the first fixed coil (focus control coil), and (28a) and (28b) are the second fixed yoke (A / T yoke). , (29a), (29b) are second fixed coils (track control coils). In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (3)

[Claims] 1. A lens holder, which holds an objective lens having an optical axis parallel to and axially fitted to be rotatable and axially movable about an axis, and to rotate and drive the lens holder in the axial direction. And a drive device for controlling a track shift and a focus shift of a light spot focused on an optical disk through the objective lens, the cylindrical outer peripheral portion and the inner peripheral portion being concentric with the axis. And a permanent magnet provided on the lens holder with different magnetic poles, and wound in a cylindrical shape concentric with the permanent magnet so that a current flows in a direction perpendicular to the axis line. A first fixed coil disposed on the outer periphery with a gap of a predetermined distance from the permanent magnet; and a first fixed coil having an arc coaxial with the permanent magnet and being symmetrical with respect to the axis. First A first fixed yoke and a substantially U-shaped second fixed yoke that are arranged in close contact with the outer periphery of the fixed coil;
By the second fixed coil wound around the fixed yoke of
An objective lens driving device comprising the driving device. 2. The second fixed yoke is sandwiched by the first fixed yoke around the outer periphery of the first fixed coil so as to be symmetrical with respect to the axis, and has a U-shape. The objective lens driving device according to claim (1), wherein both end faces of the leg are arranged so as to face the support shaft. 3. The objective lens driving device according to claim 1, wherein the permanent magnet is a plastic magnet.