JP2000090456A - Objective lens driving device and optical disk device - Google Patents

Abstract

(57) Abstract: The present invention provides an objective lens driving device that achieves a high thrust while reducing the thickness of the objective lens driving device, thereby providing an optical disk device capable of high-speed response. The purpose is to do. In order to achieve the above object, a magnetic body is arranged in a portion surrounded by a focusing coil and a tracking coil, and two surfaces facing both the focusing coil and the tracking coil are arranged in a magnetic circuit. According to the objective lens driving device of the present invention, the ratio of the effective coil length that generates an effective thrust to the entire length of the coil is increased, the thrust is improved, and the thickness of the objective lens driving device is reduced. Can be provided. By using the objective lens driving device, it is possible to provide an optical disk device capable of high-speed response.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device, and more particularly to an objective lens driving device for driving an objective lens for condensing light on a recording surface of an optical disk in a focusing direction and a tracking direction, and using the same. The present invention relates to an optical disk device.

[0002]

2. Description of the Related Art A conventional objective lens driving device for an optical disk is disclosed, for example, in Japanese Patent Application Laid-Open No. Hei 8-77586.

In order to provide an objective lens driving device having a small magnetic flux leakage into a space, the above publication discloses a holder having an objective lens attached thereto, a magnet attached to the holder, and a magnetic material. A yoke having a winding portion and a bent portion, a coil wound around the winding portion of the yoke, a fixing member, and a support mounted between the holder and the fixing member for movably supporting the holder with respect to the fixing member. The yoke has a base for attaching the yoke and the fixing member, and the yoke is formed into a substantially U-shape by winding the coil after winding the coil, and both ends of the U-shape of the yoke are formed by magnets. The configuration is such that it is arranged to face both poles.

[0004]

However, in the above-described conventional configuration, only one surface located between the magnet and the yoke generates an effective thrust among the wound coils, and Effective use is not always enough.

In view of the foregoing, the present invention provides an objective lens driving device that increases the ratio of the effective coil length that generates an effective thrust to the entire length of the coil, improves the thrust, and reduces the thickness. The purpose is to provide. It is another object of the present invention to provide an optical disk device capable of high-speed response using the objective lens driving device.

[0006]

In order to achieve the above object, a permanent magnet is arranged on an outer yoke side, which constitutes a driving device for moving an objective lens or the like for condensing light on a recording surface of an optical disk, An inner yoke is provided between the outer yokes, and a focusing coil is wound in a substantially rectangular cylindrical shape around the axis parallel to the optical axis of the objective lens so as to surround the inner yoke, and the tracking coil is parallel to the radial direction of the optical disc. The inner yoke is wound so as to surround the inner yoke in a substantially rectangular cylindrical shape around a center axis.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing the configuration of an objective lens driving device according to the present invention. FIG. 2 is a component perspective view showing a focusing coil and a tracking coil, and an inner yoke and an outer yoke.

In FIG. 1, the objective lens driving device 12 is configured as follows. An objective lens 1 for condensing light on a recording surface of an optical disc as an information recording medium is held by a lens holder 2. The lens holder 2 is movably supported by a fixing member 7 via a support 6.
Although not shown in the figure, the fixing member 7 is fixed to a case constituting the disk device, or to a base member supporting a drive mechanism and a disk drive device as shown in FIG. Note that the lens holder 2 is only supported by the support body 6 and other members are not supported, and are in a state of floating inside.

The magnetic circuit 2 includes a permanent magnet 8, an outer yoke 9 made of a magnetic material, a yoke extension 10, and an inner yoke 11 also made of a magnetic material. As shown in FIG. 2, the yoke extension portion 10 is
Are provided on both sides toward the objective lens 1 in a hole formed in the lower part of the hole so as to extend parallel to the optical axis of the objective lens. An inner yoke 11 is attached to the yoke extension 10.

The lens holder 2 includes an inner yoke 1
A focusing coil 3 and a tracking coil 4 are provided so as to surround the periphery of the reference numeral 1. The permanent magnet 8
The focusing coil 3 and the tracking coil 4 are attached to the outer yoke 9 so as to face each other with the focusing coil 3 and the tracking coil 4 interposed therebetween.

The focusing coil 3 includes the objective lens 1
Around an axis parallel to the optical axis. The tracking coil 4 is wound around an axis parallel to the radial direction of the optical disc so as to be in contact with the center of the side surface of the focusing coil 3.

FIG. 3 illustrates an example of an optical pickup using the objective lens driving device 12 of the present invention.

The optical pickup comprises an optical system 21 and an objective lens driving device 12. The optical system 21 includes a light source such as a semiconductor laser, a light detector that receives light reflected from the optical disk 22 and detects a focusing error signal, a tracking error signal, and a reproduction signal, a lens, a diffraction grating, and the like. FIG. 3 shows a configuration in which the light from the optical system is bent using the rising mirror 23 to reduce the thickness of the device.

The operation of the objective lens driving device configured as described above will be described.

First, the optical disk 22 is driven to rotate by a motor (not shown). In this state, the optical pickup is moved to a predetermined position to read out information. When the objective lens 1 is moved in the focusing direction, which is the optical axis direction of the objective lens 1, a drive current corresponding to the moving direction and the moving amount is applied to the focusing coil 3. The objective lens 1 is driven in the focusing direction by an electromagnetic force generated by the action of the drive current and the magnetic flux from the permanent magnet 8. Similarly, by applying a drive current to the tracking coil 4, the objective lens 1 is driven in a tracking direction that is a radial direction of the optical disc 22.

The magnitude of the thrust generated at this time is a product of the magnitude of the effective magnetic flux acting on the coil, the length of the coil on which the effective magnetic flux acts, and the magnitude of the drive current according to Fleming's law. Therefore, in order to increase the generated thrust, the magnetic flux, the effective length of the coil, or the drive current may be increased. However, in order to increase the magnetic flux, it is necessary to increase the size of the permanent magnet 8,
This increases the size of the device and increases the cost. In addition, increasing the drive current increases power consumption, which is also undesirable. Therefore, increasing the ratio of the effective coil length where the effective magnetic flux acts on the entire coil length is an effective method for improving the thrust.

FIG. 4 shows the flow of magnetic flux in the objective lens driving device of the present invention. FIG. 5 shows the flow of magnetic flux in the conventional objective lens driving device. 4 and 5, in order to facilitate the description, the permanent magnet 8, the inner yoke 11, the yoke extension 10, the outer yoke 9, the focusing coil 3,
Only the tracking coil 4 is shown, and the objective lens 1, the lens holder 2, the support 6, and the fixing member 7 are not shown.

First, in the conventional configuration shown in FIG. 5, if the magnetic pole of the permanent magnet 108 is an N pole on the coil side, the permanent magnet 1
08 from the opposing focusing coil 10
3 and flow toward the tracking coil 104,
It returns to the permanent magnet 108 through the yoke 109. When the direction of the magnetic poles is reversed, the direction in which the magnetic flux flows is only reversed, and either direction is acceptable.

Here, the thrust acting on the coil will be considered. Among the focusing coil 103 and the tracking coil 104, the part that receives an effective magnetic flux is a part located in a space between the permanent magnet 108 and the yoke 109. The other parts do not generate a thrust, or generate a reverse force if there is a leakage magnetic flux from the yoke 109. In this case, the ratio of the effective coil is the length of the side located between the permanent magnet 108 and the yoke 109 with respect to the sum of the lengths of the four sides of the focusing coil 103 and the tracking coil 104. Therefore, the effective coil ratio is at most about 0.4.

On the other hand, in the configuration of the present invention shown in FIG. 4, when the magnetic pole of the permanent magnet 8 is the N pole on the coil side, the magnetic flux from the permanent magnet 8 flows toward the inner yoke 11 facing the Then, it returns to the permanent magnet 8 through the yoke extension portion 10 and the outer yoke 9. The orientation of the magnetic pole may be either as described above. In this case, since the inner yoke 11 is located in a portion surrounded by the focusing coil 3 and the tracking coil 4, the magnetic flux from the opposing permanent magnets 8 can be absorbed by the inner yoke 11, and the permanent magnet 8 and the inner yoke Located between 11,
The two opposing surfaces of both the focusing coil 3 and the tracking coil 4 are portions that receive an effective magnetic flux.

That is, the ratio of the effective coil is determined by the sum of the lengths of the two sides located between the permanent magnet 8 and the inner yoke 11 with respect to the sum of the lengths of the four sides of the focusing coil 3 and the tracking coil 4. Become. Since two of the four sides can be used effectively, the ratio of effective coils can be easily set to 0.4 or more, and the thrust can be improved.

Further, in the configuration of the present invention, since the tracking coil 4 is wound so as to be in contact with the center of the side surface of the focusing coil 3, the focusing coil 3 is wound.
The tracking coil 4 can use the portion where the magnetic flux flowing from the permanent magnet 8 to the inner yoke 11 is the largest, and the magnetic flux can be used efficiently.

Further, as shown in FIGS. 6 and 7, an upper yoke 13 made of a magnetic material is provided so as to be joined to the outer yoke 9 and the inner yoke 11.
Although the weight increases, more magnetic flux from the permanent magnet can be used, and the thrust can be improved. In FIG. 7, the permanent magnet 8, the outer yoke 9, the yoke extension 10, the inner yoke 1
1, only the upper yoke 13 is shown.

Further, in the objective lens driving device of the present invention, as shown in FIG. 2, an opening 14 larger than the tracking coil 4 is provided below the outer yoke 9 to move the objective lens 1 downward in the focusing direction. When this is done, the tracking coil 4 and the outer yoke 9 do not come into contact with each other. Thereby, the lower limit of the operating range in the focusing direction can be set to the lower surface of the plate-shaped portion below the outer yoke. Therefore, the objective lens driving device can be made thin.

[0026]

According to the present invention, an inner yoke made of a magnetic material is disposed in a portion surrounded by a focusing coil and a tracking coil, and two surfaces facing both the focusing coil and the tracking coil are disposed in a magnetic circuit. Accordingly, it is possible to provide an objective lens driving device in which the ratio of the effective coil length that generates an effective thrust to the entire length of the coil is increased, the thrust is improved, and the thickness is reduced. Further, by using the objective lens driving device, it is possible to provide an optical disk device capable of high-speed response.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an objective lens driving device of the present invention.

FIG. 2 is a diagram showing a configuration of a coil and a yoke in the objective lens driving device of the present invention.

FIG. 3 is a diagram showing a configuration of an optical pickup including the objective lens driving device of the present invention.

FIG. 4 is a diagram showing a flow of a magnetic flux in the objective lens driving device of the present invention.

FIG. 5 is a diagram showing a flow of a magnetic flux in a conventional objective lens driving device.

FIG. 6 is a diagram showing another configuration of the objective lens driving device of the present invention.

FIG. 7 is a diagram showing another configuration of the objective lens driving device of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Objective lens, 2 ... Lens holder, 3 ... Focusing coil, 4 ... Tracking coil, 6 ... Support, 7
... fixing member, 8 ... permanent magnet, 9 ... outer yoke, 10
... Yoke extension part, 11 ... Inner yoke, 12 ... Object lens driving device, 13 ... Upper yoke, 14 ... Opening part,
Reference numeral 21 denotes an optical system, 22 denotes an optical disk, 23 denotes a rising mirror, 103 denotes a focusing coil, 104 denotes a tracking coil, 108 denotes a permanent magnet, and 109 denotes a yoke.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideo Suenaga 1st Kitano, Makino, Mizusawa City, Iwate Prefecture Inside Hitachi Media Electronics Co., Ltd. Inside Media Electronics (72) Inventor Fumihito Meguro 2-12-12 Nukii-Minamicho, Koganei-shi, Tokyo (72) Inventor Yo Iijima 21-28-202 Tokiwadaira Futaba-cho, Matsudo-shi, Chiba F-term (reference) 5D118 AA11 DC03 EA02 EB13 EC04 ED07 ED08 FA29

Claims (7)

[Claims] An objective lens for condensing light on a recording surface of an optical disk as an information recording medium; a lens holder for holding the objective lens; and a lens holder for connecting the lens holder to an optical axis of the objective lens and the optical disk. A support for movably supporting in a radial direction, a fixing member for fixing the support, a focusing coil and a tracking coil attached to the lens holder, and facing each other so as to sandwich the focusing coil and the tracking coil. In an objective lens driving device including a permanent magnet and an outer yoke and an inner yoke made of a magnetic material forming a magnetic circuit with the permanent magnet, the focusing coil is arranged around an axis parallel to an optical axis of the objective lens. Wound around the inner yoke in a substantially rectangular cylindrical shape, and An objective lens driving device, wherein a locking coil is wound around the inner yoke in a substantially rectangular cylindrical shape around an axis parallel to a radial direction of the optical disk. 2. An objective lens for condensing light on a recording surface of an optical disc as an information recording medium, a lens holder for holding the objective lens, and a lens holder for connecting the lens holder to an optical axis of the objective lens and the optical disc. A support for movably supporting in a radial direction, a fixing member for fixing the support, a focusing coil and a tracking coil attached to the lens holder, and facing each other so as to sandwich the focusing coil and the tracking coil. In an objective lens driving device comprising a permanent magnet, an outer yoke and an inner yoke made of a magnetic material constituting a magnetic circuit with the permanent magnet, the focusing coil and the tracking coil are each constituted by one, and the focusing is performed. The coil is parallel to the optical axis of the objective lens. The tracking coil is wound in a substantially rectangular tube shape around an axis parallel to the radial direction of the optical disk, and the focusing coil and the tracking coil face each other. An objective lens driving device, wherein a surface is disposed between the permanent magnet and the inner yoke. 3. The objective lens driving device according to claim 1, wherein an upper yoke made of a magnetic material is provided so as to be joined to the outer yoke and the inner yoke. Drive. 4. The objective lens driving device according to claim 1, wherein a distance between the permanent magnet and the inner yoke with respect to a sum of lengths of four sides of the focusing coil. The ratio of the sum of the lengths of the two sides of the focusing coil is 0.4 or more, and the sum of the lengths of the four sides of the tracking coil is between the permanent magnet and the inner yoke. The objective lens driving device, wherein the ratio of the sum of the lengths of the two sides of the located tracking coil is 0.4 or more. 5. The objective lens driving device according to claim 1, wherein the tracking coil is provided at a center of each of two surfaces of the focusing coil parallel to a radial direction of the optical disk. An objective lens driving device, which is wound and fixed so as to be in contact with each other. 6. The objective lens driving device according to claim 1, wherein an opening larger than the tracking coil is provided below the actor yoke. Lens drive. 7. An optical disk device comprising: an optical disk for recording information; a motor for rotating the optical disk; and an optical pickup movably provided to face a recording surface of the optical disk. An objective lens for condensing light on a surface, a lens holder for holding the objective lens,
A support for movably supporting the lens holder in the optical axis direction of the objective lens and in the radial direction of the optical disc, a fixing member for fixing the support, and a focusing coil mounted on the lens holder; The tracking coil is wound around an inner yoke made of a magnetic material in a substantially rectangular cylindrical shape about an axis parallel to the optical disk, and the tracking yoke is formed into a substantially rectangular cylindrical shape about an axis parallel to the radial direction of the optical disk. Permanent magnets wound around and attached to each other so as to sandwich the focusing coil and the tracking coil,
An optical disc device comprising: an outer yoke made of a magnetic material supporting the permanent magnet; a light source that emits laser light; and an optical system including a photodetector that receives reflected light from the optical disc.