JPH0515133A - Driving device for objective lens - Google Patents

Abstract

PURPOSE:To increase the seek driving force of the title device so as to make the inter-track moving speed of the device faster by providing a movable body which is positioned in a magnetic gap between the first and second permanent magnets, seeking coil provided on the movable body, and focusing coil which moves an objective supporting body. CONSTITUTION:An objective 25 is fitted to a lens holder 24 and a focusing coil 32 which makes focusing operation by driving the holder 24 in the direction parallel with the optical axis of the lens 25 is fitted to the side section of the holder 24. The lens 25 and coil 32 are supported by a movable body 22 through the holder 24. In addition, the movable body 22 is positioned in the first gap formed of the first and second permanent magnets 11 and 12. The movable body 22 is supported by guide rails 21 through a ball bearing 23 and movable in the radial direction of disks. The driving force of this objective driving device is increased by generating driving forces for seeking at two points of each seeking coil 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device provided in an optical disk reproducing or recording / reproducing device, and more particularly to an objective lens driving device in a separation type optical head.

[0002]

2. Description of the Related Art Generally, in an optical disk device, two types of coils and a magnetic circuit for moving an objective lens in two directions, a focus direction and a tracking direction, are used for recording / reproducing / erasing information on / from an optical disk, and It further has one type of magnetic circuit for seeking the objective lens to an arbitrary position in the radial direction of the disk.

Further, in recent years, an objective lens driving device such as Japanese Patent Laid-Open No. 3-23523 is proposed in which the total weight is reduced for the purpose of shortening the access time, and the driving in the focusing direction and the seek operation are performed by a common magnetic circuit. Has been done.

FIG. 4 shows a perspective view of a conventional example disclosed in Japanese Patent Laid-Open No. 3-23523. In the conventional apparatus shown in FIG. 4, the objective lens support (hereinafter referred to as a lens holder) is focused in the focusing direction by utilizing the magnetic flux generated between the permanent magnets provided on both sides of the movable body and the inner yokes facing the permanent magnets. Are driving to. Therefore, the focusing coil attached to the lens holder must be inserted into those magnetic gaps, and the lens holder extends in a direction orthogonal to the tracking direction of the disk, becomes large, and the inner yoke is inserted. It was necessary to make a through hole, and the structure was weak.

Therefore, as shown in FIG. 3A, since the lens holder is large in size and has a through hole, which is a structural defect, the resonance frequency thereof is limited to 10 and several KHz, and the focus can be constructed by a simple control means. Narrow the control frequency range.

That is, as a result, the number of revolutions of the disk that can be actually used is limited to a low level, and there is a problem in the original purpose of high-speed accessibility.

In order to solve such a problem, FIG.
An objective lens driving device shown by is proposed.

In this objective lens driving device, since the objective lens supporting body having the focusing coil is arranged in the single magnetic gap, the lens holder can be made smaller than the conventional device and the focus control frequency range can be widened. It is possible.

[0009]

However, as shown in FIG.
In the objective lens driving device indicated by (3), since the magnetic gap is large, the magnetic flux density generated is low, and it is difficult to generate a force particularly required for high-speed seek operation.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of these problems, and an object thereof is to provide an objective lens driving device which is excellent in dynamic characteristics and is capable of high-speed seek operation.

It is a further object of the present invention to provide, in an objective lens driving device, first and second permanent magnets arranged opposite to each other and a first yoke and a first yoke which respectively support the first and second permanent magnets. A movable body disposed in a first magnetic gap formed by a second yoke and the first and second permanent magnets, and a movable body provided on the movable body and wound with the first and second permanent magnets and the yoke. Rotating first and second seek coils, an objective lens support movably provided on the movable body, and the first magnetic gap provided on the support and moving the objective lens support in the focusing direction. A focusing coil disposed inside and a second magnetic gap that is disposed so as to face the first and second yokes and has one side of the first and second seeking coils positioned therein. It is achieved by having a permanent magnet.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The objective lens driving device of the present invention will be described in detail with reference to the embodiments shown in FIGS.

FIG. 1 is a perspective view of the first embodiment, and FIG. 2 is a sectional view of a magnetic circuit.

In FIG. 1, reference numeral 25 denotes an objective lens which is attached to the lens holder 24. A focusing coil 32 for driving the lens holder 24 in a direction parallel to the optical axis to perform a focusing operation is attached to a side portion of the lens holder 24, and one side of the rectangular coil is shown in FIG. Is placed in the first magnetic gap of the device and operates. The first magnetic gap is formed by the permanent magnets 11 and 12 arranged to face each other. The permanent magnets 11 and 12 are supported by the side surfaces 1a and 2a of the back yokes 1 and 2, respectively.

Further, the objective lens 25 and the focus coil 32 are supported by the movable body 22 by the leaf spring 26 via the lens holder 24. The movable body 22 is also arranged in the first magnetic gap. The leaf spring 26 is a parallel leaf spring that is deformable in a direction parallel to the optical axis of the objective lens 25. Each of the seek coils 31 mounted on the movable body 22 has a first magnetic gap formed by the permanent magnet 11 and the permanent magnet 12 and a back yoke 1 that supports the permanent magnet 11 and a back yoke that supports the permanent magnet 12. Two
Of the permanent magnets 1 arranged to face the lower surfaces 1b and 2b, respectively.
3 and 14 and a second magnetic gap having a magnetic field direction different from the magnetic field direction of the first magnetic gap. It has been turned. The permanent magnets 13 and 14 are connected by a single yoke.

The movable body 22 is supported by the guide rail 21 via a ball bearing 23 and is movable in the radial direction of the disk.

At this time, when the polar arrangement of the permanent magnets is arranged as shown in FIG. 2A, the magnetization vector between the back yokes 1 and 2 becomes horizontal to the surface orthogonal to the optical axis of the objective lens, and the seek coil is used. The magnetic circuit resistance of the magnetic circuit that applies the magnetic field to 31 is the smallest, and the magnetic flux density of each gap is the maximum,
Further, the leakage magnetic flux can be suppressed to a minimum, which is particularly effective for a magneto-optical recording type device utilizing thermomagnetic recording.

As described above, in the objective lens driving device of the present invention, in each of the wound seek coils 31, two seek gaps are formed to locate one side of the wound coil therein, and seek is performed. Since the driving force for use in generating is generated at two places, the driving force at the time of seek is increased as compared with the conventional device shown in FIG.

3A and 3B show the dynamic characteristics of the focus control of the conventional objective lens driving device and the focus control of the objective lens driving device of the present invention. Figure 3
It can be seen that the objective lens driving device of the present invention has a higher structural resonance frequency of the lens holder. That is, it can be seen that the focus controllable band is wide.

(Other Embodiments) As the construction of the magnetic circuit, as shown in FIG. 2 (b), the focus coil uses the surface magnetic flux of the permanent magnet, or as shown in FIG. 2 (c), the magnetization vector has a horizontal straight line. How to line up.

Further, FIG. 2 (d) having a structure in which FIGS. 2 (b) and 2 (c) are combined is also possible.

The magnet polarity is the best in the embodiment of the present invention in which the magnetization vector circulates, as shown in FIG. 2A, but the magnets 13 and 14 facing the back yoke may have opposite polarities. ..

Although the magnetic circuit for tracking has not been mentioned in the above-mentioned embodiment, the magnetic circuit for seek may be used for tracking.
It is also possible to provide a galvanometer mirror that is fixed to the device and is removed from the movable body as in the disclosed device. (Fig. 2 (c))

[0024]

As described above, in the objective lens moving device according to the present invention, since the objective lens holder can be downsized, not only can the frequency band used for focusing be improved and recording / reproduction of a disc rotating at high speed can be achieved. The driving force in the seek direction can be increased and the movement between tracks can be performed at high speed.

Therefore, it is possible to provide an optical disk device capable of higher data transfer and faster data access.

[Brief description of drawings]

FIG. 1A is a perspective view showing an embodiment of an objective lens driving device of the present invention. 1B is a perspective view showing details of the magnetic circuit shown in FIG. 1A.

FIG. 2a is a cross-sectional view of the magnetic circuit shown in FIGS. 1a and 1b. b is a cross-sectional view showing another embodiment of the magnetic circuit. c is a sectional view showing another embodiment of the magnetic circuit. FIG. 3D is a sectional view showing another embodiment of the magnetic circuit.

FIG. 3A is a diagram showing a dynamic characteristic of a conventional objective lens driving device. FIG. 5B is a diagram showing the dynamic characteristics of the objective lens driving device of the present invention.

FIG. 4A is a perspective view showing a configuration of a conventional objective lens driving device. 4b is a sectional view of FIG. 4a.

FIG. 5 is a perspective view showing the configuration of another conventional objective lens driving device.

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[Procedure amendment]

[Submission date] October 11, 1991

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

Claims (1)

Claim: What is claimed is: 1. A first and a second permanent magnet, which are arranged to face each other, and a first yoke, a second yoke, and a first yoke which respectively support the first and second permanent magnets. A movable body disposed in a first magnetic gap formed by a second permanent magnet and first and second windings provided on the movable body and winding the first and second permanent magnets and a yoke. The seek coil, the objective lens support movably provided on the movable body, and the focusing provided on the support and in the first magnetic gap for moving the objective lens support in the focusing direction. A coil and a third permanent magnet that faces the first and second yokes and forms a second magnetic gap in which one side of the first and second seeking coils is located. Characterized by An objective lens driving device.