JPS62154334A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To reduce the gap of a magnetic circuit and to improve magnetic flux density by providing a coil for focus control and a magnetic circuit facing a coil for track control separately, and eliminating a coil holder. CONSTITUTION:A coil 10 for focus control is attached to the cylindrical part 3b concentric with the cylindric bearing 3a of a lens holder 3, and coils 11a, 11b for track control are attached to left and right sides of the lens holder. The coil 10 for focus control is placed in the magnetic path formed of a permanent magnet 17 for focus control and a yoke 18 for focus control. Coils 11a, 11b for track control are placed in a magnetic path consisting of permanent magnets 19a, 19b for track control and yokes 20a, 20b for track control. By applying desired current to the coil 10 for focus control, the lens holder 3 is slid in the direction of the arrow mark A to adjust the focal length of an objective lens 1. The lens holder 3 is rotated in the direction of the arrow mark B, and controls the track by rotating the objective lens 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] 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.

[Prior Art] FIGS. 7 to 10 show a conventional objective lens driving device. In the figures, (1) is the objective lens, and (2) is the objective lens drive device.
is a counterweight, (3) is a lens 11 having a cylindrical bearing (3a), and (4) is a lens holder (3).
The bearing (3a) or the support shaft (5) holds the lens holder (3) so that it can slide freely in the axial direction of arrow A in Figure 8 and rotatably in the direction of arrow B in Figure 9. support rubber, (
6a), (6b) are permanent magnets, (7a), (7b) are B
- Ri, (8) is support! r14) and permanent magnets (6a), (6
b) Yoke that also serves as a holding base, (9) is the support rubber (5)
(10) is a focus control coil, (11a>,
(11b), (11c), (11d> are the coils for track control, (12a), (12b) are the fixing screws that hold the support rubber (5) on the fixing base (9), (]3 ) is a cover, and (4) is a coil holder.

Next, the operation will be explained. Focus control coil (10
) by applying a desired current to the lens holder (3).
slides in the direction of arrow A to perform focus control. Also, track control coils (11a), (11b), (11c)
, (11d), the lens holder (3) rotates in the direction of arrow B and is fixed at a position a certain distance away from the support shaft (4). Track control is performed by rotating the objective lens (1).

[Problem to be solved by the invention] Since the conventional objective lens driving device is configured as described above, the focus control coil (10), the track control coil (11a), (1l b>, MlG> , (11d)
are permanent magnets (6a), (6b) and yoke (7a)
, (7b), and (8), permanent magnets (6a) and (6b) cannot be placed around the entire circumference, and a portion must be cut out. . This is a track control coil (11a>, (11b>, (1
1c), (11d> are rectangular, so if you try to use the same magnetic circuit as the focus control coil (10), the track control coils (11a), (1l b), (11c)
), (11d>) can only be placed in the magnetic path.

For this reason, the entire circumference of the focus control coil (10) cannot be used, resulting in poor usage efficiency.

Also, track control coils (11a), (11b), (11c), (11d) are placed above the focus control coil (10).
Since it is attached, the top of the magnetic circuit needs to be tightened. That is, as shown in FIG. 10, the gap H of the magnetic circuit is determined by the coil holder (14), the focus control coil (10), and the track control coil (11a), so it is inevitable to make the gap of the magnetic circuit large. Is it necessary? Therefore, in order to obtain the necessary magnetic flux density, it is necessary to increase the volume of the permanent magnet, which increases costs and makes it difficult to downsize.

Furthermore, track control coils (11a), (llb), (11C), (lid) are placed above the focus control coil (10).
) has the problem of requiring precision and being difficult to assemble, since it is desired to make the gears and tabs as small as possible.

This invention was made to solve the above-mentioned problems, and an object of the present invention is to provide an objective lens drive device with high drive efficiency.

[Means for Solving the Problems 1] The objective lens driving device according to the present invention is provided with separate magnetic circuits facing the focus control coil and the track control coil, and improves the focus 11 control drive rate. In order to achieve this, the coil holder that holds the focus control coil was eliminated, the gap in the magnetic circuit was made as small as possible, and the effective magnetic flux density was increased.

[Effect 1] The magnetic circuit facing the focus control coil in this invention is provided separately and independently from the magnetic circuit facing the track control coil, and the coil holder for holding the focus control coil is eliminated. The only factor that determines the gap in the magnetic circuit is the focus control coil, which greatly improves the magnetic flux density and improves the driving efficiency of the objective lens driving device.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1st
The figure is a plan view showing an objective lens driving device according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line I-I in FIG.
4 is a partial sectional view showing the relationship between the gap in the magnetic circuit and the focus control coil. FIG. 5 is an exploded perspective view showing the assembly of the lens holder and the focus control coil. FIG. 6 is a partial perspective view showing a lens holder and a focus control coil, and the same parts as in FIGS. 7 to 10 are given the same reference numerals.

In Figures 1 to 3, the lens holder (3) equipped with the objective lens (1) and counterweight (2) is
It is supported by a support rubber fixing pin (15) via a support rubber (5), and this support rubber fixing pin (15) is attached to a fixing base (16).
) is maintained.

Further, the lens holder (3) has a focus control coil (10) attached to the cylindrical portion (3b) concentric with the cylindrical bearing (3a), and track control coils (11a) on the left and right sides. (11b) is removed, and the focus control coil (10) is composed of a focus control permanent magnet (17) and a focus control yoke (18) which are provided on the fixed side.
The track control coils (11a) and (11b> are permanent magnets for track control <19a> and (19b)) provided on the fixed side.
It is arranged in a magnetic path formed by the track control yokes (20a) and (20b).

By applying a desired current to the focus control coil (10), the lens holder (3) rotates in the direction of arrow A to adjust the focal length of the objective lens (1). Further, by applying a desired current to the track control coils (11a>, (11b>), the lens holder (3) rotates in the direction of arrow B, and the objective lens (1) is rotated to perform track control. do.

The focus control permanent magnet (17) and the track control permanent magnets (19a) and (19b) each include a ring magnet magnetized in the radial direction and a left and right bipolar magnet. Therefore, as shown in FIG. 4, the focus control coil (10) is the only factor that determines the gap H' in the magnetic circuit, making it possible to minimize the gap in the magnetic circuit.

Further, as shown in FIG. 5, a notch is also provided in the lens holder (3b) to ensure a space for drawing out the focus control coil wire (10) and for applying adhesive.

Further, when the lens holder (3b) is made of a plastic material, the focus control coil (10) is formed by integral molding.

[Effect of the invention 1 As described above, according to the present invention, the thickness of the coil holder that holds the focus control coil is set to be less than or equal to the thickness of the focus control coil, so that the gear of the magnetic circuit can be used for focus control. Since it is determined only by the coil, it can be made extremely small, the magnetic flux density can be significantly improved, and the objective lens driving device can be made smaller and its cost can be reduced.

Further, when the coil holder is made of a plastic material, the focus control coil is molded into a single piece, thereby simplifying the assembly.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an objective lens driving device according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line I-I in FIG. 1,
Figure 3 is an exploded perspective view of the main parts, Figure 4 is a partial sectional view showing the relationship between the magnetic circuit gap and the focus control coil, and Figure 5 is an exploded perspective view showing the assembly of the lens holder and focus control coil. , FIG. 6 is a partial perspective view showing the integral molding of a lens holder and a focus control coil, FIG. 7 is an exploded perspective view of a conventional objective lens drive device, and FIG. 8 is a sectional view of its assembled state.
FIG. 9 is an exploded perspective view of a part of the magnetic circuit, and FIG. 10 is a partial sectional view showing the relationship between the gear and the coil of the magnetic circuit. In the figure, (1) is an objective lens, (3) is a lens holder, (4) is a support shaft, (10) is a focus control coil, and (1) is a support shaft.
1a>, (11b) is a track control coil, (17)
, (18) is a magnetic circuit for focus control (permanent magnet, yoke)
, (19a>, (19b), (20a), and (20b) are magnetic circuits for track control (permanent magnet, yoke). In the figures, the same reference numerals indicate the same or equivalent parts. Agent Patent attorney Masuo Oiwa (2 others) Figure 1: t4%'m Ila, I
lb: l-lami/11th mte coil 3; Shin χ
Water Luk 19a, 19b: Permanent AF+4: Top axis
20o, 20b: 3-ri Fig. 2 17: Eternal stone Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8

Claims (2)

[Claims] (1) A lens holder that is rotatably and axially movably fitted onto a support shaft and holds a lens having an optical axis parallel to the axial direction of the support shaft; In an objective lens drive device, the objective lens drive device includes a drive device that drives in an axial direction, and drives the lens holder to control track deviation and defocus of a light spot focused on a disk via the lens, In order to reduce the size of the drive device and improve drive efficiency, the focus control coil as the drive device is joined to the lens holder only at an end of the focus control coil, and the focus control coil is joined to the lens holder. An objective lens drive device characterized by having a part cut out. (2) The objective lens driving device according to claim 1, wherein the lens holder and the focus control coil are integrally molded.