JPH0689449A - Objective lens drive - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to effectively prevent the lens holder 20 from jumping to the disk side without causing film breakage or wire breakage in the focusing direction drive coil or the like when the focus servo deviates. A possible objective lens driving device is realized. [Structure] A space between a pair of yokes 51a, 51a of a magnetic circuit 50 is covered with a protective plate 60 made of a ferromagnetic material at its upper end surface. Stoppers 62, 62 are horizontally formed at the front end of the protective plate 60 so as to extend toward the front and rear sides. If the lens holder 20 rises excessively when the servo goes off,
The upper surface of the lens holder 20 abuts on the stoppers 62, 62, which prevents the lens holder 20 from floating, that is, protruding toward the disk. At this time, the focus direction drive coil 40
The distance between the stoppers 62, 62 and the upper surface of the lens holder is set so that the F and the tracking direction drive coil 40T do not collide with the protective plate 60.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is directed to irradiating a recording medium such as a magneto-optical disk with a focused light beam to
The present invention relates to an objective lens driving device equipped in an optical pickup device capable of optically recording, reproducing, or rewriting information.

[0002]

2. Description of the Related Art An optical pickup device is equipped with an objective lens driving device for controlling a focusing position of a light beam focused and irradiated on a disk through an objective lens in a focus direction and a tracking direction. FIG. 4 shows a conventional example of this type of objective lens driving device.

The objective lens 90 is mounted on the tip of a lens holder 91 with its optical axis directed in the vertical direction (focusing direction F). The lens holder 91 is elastically supported on the fixed base 92 by four elastic supports 93 so as to be movable in the focus direction F and the tracking direction T. At the rear of the lens holder 91, a focus direction drive coil 94 having a rectangular frame shape is arranged. Further, a flat tracking direction driving coil 95 is arranged adjacent to a part of the focus driving coil 94.

On the other hand, a magnetic circuit 96 is provided on the fixed base 92. The magnetic circuit 96 includes a pair of yokes 97.
It has a and 97a and permanent magnets 97b and 97b, and has a concave shape with the open side facing upward. In the magnetic gap 98 of the magnetic circuit 96, the focus direction drive coil 9 described above is provided.
4 and a part of the tracking-direction drive coil 95 adjacent to this part are arranged. Further, a protective plate 99 made of a ferromagnetic material is bridged between the upper end surfaces of the pair of yokes 97a, 97a.

In such a configuration, when a current is passed through the focus direction drive coil 94, the lens holder 91 moves in the focus direction F together with the focus direction drive coil 94 in accordance with the cooperation with the magnetic circuit 96, that is, Fleming's left-hand rule. The objective lens 90 is levitated and the position of the objective lens 90 is controlled in the focus direction by controlling the current value, whereby focus servo is performed.

When a current is applied to the tracking direction drive coil 95, the lens holder 91 is moved in the tracking direction T in accordance with Fleming's left-hand rule, and tracking control is performed. At this time, the protection plate 99
Suppresses the vibration of the magnetic circuit 96 and closes the magnetic gap 98 that opens upward to reduce the leakage magnetic flux. That is, the magnetic circuit 96 is mechanically and magnetically reinforced by the protective plate 99.

Further, the protective plate 99 has the following functions. That is, in such an objective lens driving device, a control error called servo deviation may occur. When the servo deviates due to the focus servo, the current in the direction to levitate the lens holder 91 remains flowing in the focus direction drive coil 94, and the lens holder 91 jumps out to the disk side and collides with the disk, and both are damaged. Alternatively, the lens driving device itself may be destroyed.

If the protection plate 99 is provided, the focus direction drive coil 94 or the tracking direction drive coil 95 collides with the protection plate 99, and the lens holder 91 is prohibited from floating. That is, the protective plate 99 also has a function of preventing the above-mentioned problems from occurring.

[0009]

However, according to the above configuration, there is a possibility that the coil film may be broken or the coil may be broken due to the collision of the coil with the protective plate 99.

In order to solve this problem, as shown in FIG. 5, a cover 70 for covering the objective lens driving device is used as a stopper. That is, the cover 70 has a lens holder 91 around the upper opening 71.
Of the focus drive coil 94 and the tracking direction drive coil 95 are prevented from colliding with the protective plate 99.

However, in such a structure, it is necessary to raise the upper surface of the cover 70 to the upper limit of the floating of the lens holder 91, and as a result, when it is applied to the disk 80 having the cartridge 81, as shown in FIG. There is a risk that the cover 70 interferes with the cartridge 81.

The present invention is intended to solve the above-mentioned problems of the prior art, and an object thereof is to prevent a coil such as a focus direction drive coil mounted on a lens holder from being cut off or broken. An object of the present invention is to provide an objective lens driving device that can effectively prevent the lens holder from popping out when the servo goes out.

[0013]

An objective lens driving device of the present invention includes a lens holder that is supported so as to be able to float in the focus direction and that holds an objective lens that focuses a light beam and irradiates the recording medium with the focused light. A focus driving coil that can float together with the lens holder, a magnetic circuit that cooperates with the focus driving coil to drive the lens holder in the focus direction, and is fixedly arranged so as to cover the magnetic circuit. , A protective plate that suppresses the vibration of the magnetic circuit and reduces the leakage magnetic flux from the magnetic circuit and a part of the protective plate, and when the lens holder floats excessively, the lens holder contacts the lens holder. , And a stopper for prohibiting the movement thereof, whereby the above object is achieved.

[0014]

If the stopper as described above is provided on a part of the protective plate, the servo deviates in the focusing direction, and when the lens holder rises excessively, the stopper comes into contact with the lens holder and prohibits further movement. Therefore, the focus drive coil and the tracking drive coil that drives the objective lens in the tracking direction come into contact with the protective plate,
The coil coating will not be peeled off or disconnection will occur. Further, there is no problem that the lens holder pops out in the focus direction, the objective lens and the disk collide with each other, and both are damaged.

Moreover, since such a stopper can be continuously provided from the protective plate, the number of parts is increased and there is no fear that the device structure becomes complicated.

[0016]

EXAMPLES Examples of the present invention will be described below.

Example 1 FIG. 1 shows Example 1 of the objective lens driving device of the present invention. The objective lens driving device includes a lens holder 20 that holds the objective lens 10. The lens holder 20 includes a lens holding portion 21 at the tip.
And the coil holding portion 22 at the base are connected in a horizontal direction. The lens holding portion 21 has a block shape, and the coil holding portion 22 has a U-shape. Lens holder 21
, The objective lens 10 is mounted with the optical axis oriented in the vertical direction. The coil holding portion 22 is joined to the lens holding portion 21 on the open side, and is arranged on the horizontal fixed base 30.

The base end of the fixed base 30 projects upward, and the holder support 31 is attached to the projection.
From the holder support 31, two linear upper and lower sides on each side, a total of four linear elastic supports 32 ... Extend to the tip side, and each widened tip is fixed to both side surfaces of the coil holding part 22. ing. Therefore, the coil holding portion 22 includes the four elastic support members 3
The lens holder 20 is elastically supported by 2 so as to be movable in the vertical direction and in the horizontal direction perpendicular thereto.
Can be levitated in the focus direction F and can be moved in the tracking direction T.

Inside the coil holding portion 22 of the lens holder 20, a rectangular frame-shaped focus direction drive coil 4 is provided.
0F and a flat tracking direction drive coil 40T are provided. Tracking direction drive coil 40T
Are arranged along one side surface portion 41 of the focus direction drive coil 40F.

A magnetic circuit 50 is provided on the fixed base 30. The magnetic circuit 50 includes a pair of yokes 51 a, 51 joined to the upper surface of the fixed base 30 with the open side facing upward.
b, and a pair of permanent magnets 52a and 52b joined to the respective facing surfaces of the pair of yokes 51a and 51b,
A magnetic gap 53 is formed between the permanent magnets 52a and 52b. That is, the magnetic circuit 50 has a concave shape with the upper side open as a whole. And the permanent magnet 52
One side surface portion 41 of the focus direction drive coil 40F and a part of the tracking direction drive coil 40T along the side surface portion 41 are disposed between a and 52b.

A protective plate 60 made of a thin plate-shaped ferromagnetic material is provided on the magnetic circuit 50. More specifically,
A protective plate 60 is laid across the upper end surfaces of the pair of yokes 51a and 51b. In addition, a pair of stoppers 62, 6 are provided on the front end of the protective plate 60 toward the front and rear sides.
2 is formed to project horizontally. More specifically, the protective plate 60 is formed by punching and bending a thin plate.
And a pair of stoppers 62, 62 are integrally formed.

With the protective plate 60 attached, the stoppers 62, 62 are located above both sides of the lens holder 21 in the lens holder 20, and the lens holder 2
The distance from the upper surfaces of both side portions of 1 to the stoppers 62, 62 is the distance from the one side surface portion 41 of the focus direction drive coil 40F and the tracking direction drive coil 40T arranged in the magnetic gap 53 of the magnetic circuit 50 to the protective plate 60. Has been made slightly smaller than. Therefore, when the lens holder 20 continues to float in the focus direction, before the one side surface portion 41 of the focus direction drive coil 40F and the tracking direction drive coil 40T collide with the protective plate 60,
The upper surfaces of both sides of the lens holder 21 are stoppers 62, 62.
Clash with. Therefore, the focus direction drive coil 40F
Also, a part of the tracking direction drive coil 40T does not collide with the protective plate 60.

In the objective lens driving device having such a structure, when a current is passed through the focusing direction driving coil 40F in a direction in which the focusing direction driving coil 40F floats, the focusing direction driving coil 40F and the magnetic circuit 50 cooperate with each other to perform Fleming. The lens doll 20 floats in the focus direction F in accordance with the left-hand rule. Therefore, if the value of the current flowing through the coil is controlled, the position of the objective lens 10 is controlled in the focus direction F, and the focus servo is performed. Also,
Similarly, if the current value flowing to the tracking direction drive coil 40T is controlled, the objective lens 10 moves in the tracking direction T
The position is controlled to the position where tracking servo is performed.

At this time, since the magnetic circuit 50 is covered between the open ends by the holding plate 60, it is mechanically strengthened and vibration can be suppressed. Further, since the upper part of the magnetic gap 53 is magnetically shielded by the protective plate 60, the leakage magnetic flux can be reduced.

By the way, in such a lens driving device, when the servo deviates in the focusing direction and the current for moving the lens holder 20 upward continues to flow in the focusing direction driving coil 40F, the lens holder 20 floats excessively. Cause However, the lens holder 2
When 0 rises excessively, both upper surfaces of the lens holding portion 21 of the lens holder 20 collide with the stoppers 62, 62. Therefore, the serious situation that the lens holder 20 jumps up is avoided. Further, when the lens holder 20 floats, the magnetic gap 53 of the magnetic circuit 50 is increased.
The one side portion 41 of the focus direction drive coil 40F and the tracking direction drive coil 40T disposed inside rise up in the magnetic gap 53 and approach the protective plate 60, but before these collide with the protective plate 60, the stopper is provided. 62, 62
This prevents the lens holder 20 from floating. Therefore, the focus direction drive coil 40F and the tracking direction drive coil 40T do not collide with the protective plate 60. Therefore, there is no risk of film breakage or wire breakage.

(Embodiment 2) FIG. 2 shows Embodiment 2 of the lens driving device of the present invention. This lens driving device includes a cover 70.
have. Since this objective lens driving device is also provided with the stoppers 62, 62 similar to the first embodiment as shown in the figure, it is not necessary to use the cover 70 as the stopper. Therefore, the cover 70 is designed so that the upper surface opening 71 is large and the upper surface is sufficiently lowered. Therefore, as shown in FIG. 3, when this lens driving device is applied to the disk 80 having the cartridge 81, it is possible to prevent the cover 70 from interfering with the cartridge 81, unlike the above-mentioned conventional example.

[0027]

According to the objective lens driving device of the present invention described above, a part of the protective plate for mechanically and magnetically strengthening the magnetic circuit is brought into contact with the lens holder that is excessively levitated when the focus servo is out of the range. Since the stopper is provided to prohibit the floating, it is possible to prevent the lens holder from jumping out toward the disc side, and it is possible to reliably prevent the problem that both the objective lens and the disc are destroyed.

Further, since it is possible to prevent a coil such as the focus direction driving coil from coming into contact with the protective plate, there is no problem such as film breakage or wire breakage in the coil.

Further, since the stopper prohibits the lens holder from excessively floating, it is not necessary to use the cover as a stopper even when the cover is used together. Therefore, it can be applied to a disc having a cartridge. As described above, the lens driving device of the present invention has a wide range of applications and is extremely useful.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of an objective lens driving device of the present invention.

FIG. 2 is a perspective view showing a second embodiment of the objective lens driving device of the present invention.

FIG. 3 is a side view showing a usage state of the objective lens driving device according to the second embodiment.

FIG. 4 is a perspective view showing a conventional objective lens driving device.

FIG. 5 is a perspective view showing a conventional objective lens driving device having a cover.

FIG. 6 is a side view showing a usage state of a conventional objective lens driving device with a cover.

[Explanation of symbols]

 10 Objective Lens 20 Lens Holder 21 Lens Holding Section 22 Coil Holding Section 30 Fixed Base 32 Elastic Support 40F Focus Direction Driving Coil 40T Tracking Direction Driving Coil 50 Magnetic Circuit 53 Magnetic Gap 60 Protective Plate 62 Stopper 70 Cover 80 Disc

Front page continuation (72) Inventor Hideo Sato 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation

Claims (1)

[Claims] 1. A device that is supported so as to be able to float in the focus direction,
A lens holder that holds an objective lens that focuses a light beam and irradiates a recording medium with focused light, a focus driving coil that can float with the lens holder, and the lens that cooperates with the focus driving coil. A magnetic circuit for driving the holder in the focus direction, a protective plate fixedly arranged so as to cover the upper part of the magnetic circuit, suppressing vibration of the magnetic circuit and reducing leakage magnetic flux from the magnetic circuit; An objective lens driving device, which is provided on a part of a plate, and which comprises a stopper that abuts on the lens holder and prohibits its movement when the lens holder floats excessively.