JP2000011407A - Object lens driving device and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an object lens driving device provided with a means for offsetting an unnecessary moment at the time of driving an object lens, and controlling a tilt thereof. SOLUTION: This object lens driving device consists of; a moving part comprising an object lens 13, a magnetic circuit formed of a yoke 17 and a magnet 18, a focus coil 15 which is arranged in this magnetic circuit and slightly moves the object lens 13 in the direction of the focus Z, and a tracking coil 16 which is arranged in the above-mentioned magnetic circuit and slightly moves the object lens 13 in the direction of tracking Y; and a supporting member 21 for supporting the movable part, and is provided with a tracking current supplying means wherein a tracking coil 16 is arranged in the directions of tracking Y and focus Z almost in a same plane, and the tracking coil 16 is made to generate a torque in the opposite direction to that of the focus coil 15 when the movable part moves in the direction of tracking.

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 and an optical disk device using the same, and more particularly to an information recording medium used for an optical disk device such as an optical disk device, a magneto-optical disk device, and a CD-ROM device. The present invention relates to a means for driving an objective lens which optically records information or reads information from an information recording medium.

[0002]

2. Description of the Related Art Conventional objective lens driving devices include, for example,
As shown in JP-A-7-320278,
A plate-shaped magnetic body is arranged on the side of a magnetic circuit composed of a magnetic plate and a magnet, and the distribution of the magnetic flux density in the magnetic gap in the tracking direction is made uniform by the plate-shaped magnetic body, thereby generating a stable driving force. The tilt of the objective lens was suppressed.

Further, as described in Japanese Patent Application Laid-Open No. 7-240031, a moment force caused by a driving force of a focus coil when an objective lens is moved in a tracking direction and in a focusing direction is perpendicular to the tracking direction. The magnetic flux passing through the ineffective wire layer portion of the air-core-shaped tracking coil wound in the plane cancels out the magnetic flux and suppresses the inclination of the objective lens.

[0004]

In an optical disk apparatus, an optical head coarsely moves a mounted objective lens driving device in a radial direction of the optical disk. The objective lens driving device includes a movable section including the objective lens and a support member that supports the movable section, and finely moves the objective lens with respect to the recording medium. The movable part of the objective lens driving device usually includes an objective lens, a magnetic circuit formed by a yoke and a magnet, a focus coil disposed in the magnetic circuit to finely move the objective lens in a focus direction, and disposed in the magnetic circuit. And a tracking coil for finely moving the objective lens in the tracking direction. Regardless of the position in the tracking direction, the drive center of the focus coil
It substantially coincides with the center of force of the magnetic circuit formed by the yoke and the magnet. Therefore, when the objective lens moves in the tracking direction, a difference occurs between the center of gravity of the movable portion and the drive center, and a moment force is generated by the focus coil driving force. Due to this moment force, the objective lens is tilted, and an optical aberration and defocus occur in a spot focused by the objective lens. As a result, there have been problems such as the deterioration of the reproduction signal of the recording medium and the inability to correctly record.

SUMMARY OF THE INVENTION An object of the present invention is to provide an objective lens driving device provided with means for canceling an unnecessary moment when the objective lens is driven and suppressing the tilt of the objective lens, and an optical disk device equipped with the objective lens driving device. is there.

[0006]

In order to achieve the above object, the present invention provides a movable part including an objective lens mounted on an optical head for coarsely moving the optical disk in a radial direction, and a supporting member for supporting the movable part. An objective lens driving device comprising: a movable circuit, an objective lens, a magnetic circuit formed of a yoke and a magnet, a focus coil disposed in the magnetic circuit to finely move the objective lens in a focus direction, and a magnetic circuit An objective lens driving device comprising: a tracking coil that is disposed in the tracking direction to finely move the objective lens in the tracking direction; wherein the tracking coil is a flat-shaped coil that is disposed in substantially the same plane in the tracking direction and the focusing direction; Moment in the direction opposite to the moment force by the focus coil driving force when the camera moves in the tracking direction Suggest objective lens driving device provided with a tracking current supply means for generating a force by the tracking coils.

[0007] The tracking coil has a plurality of upper and lower portions for guiding current parallel to the tracking direction. When the tracking coil moves in the tracking direction, a force acting from a magnetic circuit on the upper invalid line layer and the lower invalid line layer of the tracking coil. Tracking coil utilizing the difference between the two.

When the height hmg of the magnet is in the range of 1 to 10 mm, the height hTR of the tracking coil is equal to the height hmg of the magnet.
It is desirably 0 to 1.5 mm lower than that.

When the height hmg of the magnet is 6 mm or more, the height hmg of the magnet and the height hTR of the tracking coil may be substantially the same.

[0010] The height hmg of the magnet and the height hTR of the tracking coil may be in a relationship of hmg = -21.4 / hTR + 8.8 ± 0.3 mm.

[0011] The tracking coil may be composed of a plurality of flat-shaped coils which are arranged in substantially the same plane in the tracking direction and the focus direction and are supplied with current independently.

The tracking coil has a plurality of upper and lower portions for guiding current parallel to the tracking direction, and is generated between the tracking coil and the support center of the support member when the upper ineffective line layer deviates from the effective portion of the magnetic circuit. The tracking coils may be arranged so as to use the difference.

In order to achieve the above object, the present invention also proposes an optical disk device having any one of the above-described objective lens driving devices mounted on an optical head.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of an objective lens driving device according to the present invention and an optical disk device equipped with the same will be described with reference to FIGS.

FIG. 1 is a perspective view showing a schematic structure of an embodiment of an optical disk apparatus according to the present invention. Here, an optical disk device according to the present invention will be described taking a CD-ROM device as an example. When the compact disk 1 is placed on the disk tray 3, the CD-ROM device sends the disk 1 into the device by a disk loading mechanism (not shown). The disk 1 is magnetically attracted and fixed to the turntable 2 of the spindle motor by the clamper 4 attached to the clamper holder 5.

The disk 1 is rotated at a predetermined rotation speed by a spindle motor, and information is written or information is read by an optical head 9 provided in a unit mechanical chassis 6 disposed below the disk 1. The optical head 9 is fixed to the unit mechanical chassis 6 so as to be able to move roughly in the radial direction of the disk 1 and has an objective lens driving device 10 mounted thereon. The unit mechanical chassis 6 is attached to the mechanical base 7 via anti-vibration legs 8a to 8d made of an elastic member. Outside these mechanisms, a bottom cover 11 and a top cover 12 are attached.

FIG. 2 is a perspective view showing the appearance of an embodiment of the objective lens driving device according to the present invention. Here, the optical axis direction of the objective lens 13, that is, the Z axis is defined as a focus direction, and the disk radial direction, that is, the Y axis is defined as a tracking direction. The objective lens 13 is held by a lens holding member 14 made of a high-rigidity plastic non-magnetic material such as polycarbonate. Air-core shaped focus coil 1
5 is symmetrically disposed on the lens holding member 14 with respect to the ZX plane. In the present invention, the focus coil 1
5, a flat tracking coil 16a, 1
6b are arranged symmetrically with respect to the ZX plane in the same YZ plane. A yoke 17 made of a magnetic material such as iron and magnets 18a and 18b for forming a magnetic field
The magnetic circuit is formed such that the surface where the tracking coils 5 and the tracking coils 16a and 16b exist is a gap. On both sides of the lens holding member 14, small substrates 19a and 19b are arranged symmetrically with respect to the ZX plane, and the supporting member mounting substrate 20
And support members 21a to 21d made of a spring material such as a phosphor bronze wire having a diameter of about 0.1 mm are arranged symmetrically with respect to the ZX plane and the XY plane and parallel to each other, and fixed by soldering or the like. I have.

The objective lens driving apparatus according to the present embodiment has means for making the resultant force almost zero by combining the moment force AF by the focus coil 15 with the moment force TR by the tracking coils 16a and 16b provided with the rotation driving means. ing.

According to the present invention, one side of the focus coil 15 is sandwiched between gaps of a magnetic circuit formed by the yoke 17 and the magnets 18a and 18b for forming a magnetic field, and flat tracking coils 16a and 16b are provided on one side thereof. A structure that is symmetrically arranged with respect to the ZX plane within the same YZ plane has been proposed, and the number of magnets, the shape and number of magnetic circuits,
The method of supporting the movable portion including the objective lens 13 is not limited, so that various variations can be developed without departing from the technical scope of the present invention. Further, an objective lens driving device in which the configuration of the magnetic circuit is rotated by 90 degrees and the functions of the focus coil and the tracking coil are reversed may be adopted.

FIG. 3 shows the principle that when the objective lens 13 is moved by Δy in the tracking direction and Δz in the focusing direction, a moment force AF 23 is generated by the focus coil driving force 22 and the objective lens is tilted. FIG. When a current is applied to the focus coil 15, a focus driving force 22 is generated according to Fleming's law. The drive center 24 is connected to the yoke 17 and the magnets 18a for forming the magnetic field, regardless of the position of the focus coil 15.
18b.
On the other hand, the support center 25 is the support member 21a of FIG.
And moves with the position of the movable part including the objective lens 13 and the focus coil 15. For this reason, a difference is generated between the support center 25 and the drive center 24, and a moment force AF23 is generated with the difference being the arm length and the rotation center as the support center 25. Moment force AF
Due to 23, the movable part including the objective lens 13 and the focus coil 15 is tilted, and the objective lens 13 is tilted. At this time, the difference between the support center 25 and the drive center 24, that is, the length of the arm, is substantially equal to the movement amount Δy in the tracking direction.

FIG. 4 shows a conventional magnetic circuit in which the height hmg of the magnet is sufficiently higher than the movable range hTRa of the tracking coils 16a and 16b in the vertical direction, by moving the objective lens 13 by Δy in the tracking direction and focusing. When the tracking coil 16a is moved by Δz in the direction,
It is a figure showing the state of 16b. Similarly to the focus driving force 22, when a current is applied to the tracking coils 16a and 16b according to Fleming's law, the tracking driving force 2
6 occurs. At this time, the height hmg of the conventional magnet is the movable range hTRa of the tracking coils 16a and 16b in the vertical direction.
Therefore, the magnetic flux density distribution in the vertical direction in the vertical movable range hTRa of the tracking coil is uniform as shown on the right side of FIG. Therefore, there are two upper and lower portions in the figure that guide the current in parallel with the tracking direction of the tracking coil 16a, and the force 28a acting on the upper ineffective line layer 27a and the force 28b acting on the lower ineffective line layer 27b are shown in FIG. In the focus direction, they work in opposite directions, and are equal regardless of the position of the tracking coil 16a, and the focus driving force 29a does not occur. Similarly,
The focus driving force 29b of the tracking coil 16b is not generated. Further, since the force on the other side acts in the tracking direction passing through the support center 25, that is, in the Y direction, no moment force TR30 about the rotation of the support center 25 by the tracking coils 16a and 16b is generated. The objective lens 13 is inclined only by the moment force AF23.

FIGS. 5 to 7 are diagrams showing the principle of suppressing the inclination of the objective lens 13 by using a tracking coil provided with the rotation driving means according to the present invention.

FIG. 5 is a diagram showing the principle of tilt suppression using the difference in the force applied to the upper and lower ineffective line layers 27a and 27b of the tracking coils 16a and 16b as the rotation driving means. Since the force acting on the upper ineffective line layer 27a and the force acting on the lower ineffective line layer 27b of the flat tracking coil 16a also serving as the rotation driving means are opposite to each other in the focus direction according to Fleming's law, In the neutral position, both upper and lower invalid line layer driving forces 28a, 28b
Cancel each other out.

However, if the height hmg of the magnet is made smaller than in the prior art, as shown on the right side of FIG. 5, a distribution occurs in the magnetic flux density in the vertical movable range hTR of the tracking coils 16a and 16b. Therefore, depending on the position of the tracking coil 16a, a difference occurs between the force 28a acting on the upper ineffective line layer 27a and the force 28b acting on the lower ineffective line layer 27b, and a focus driving force 29a is generated. Similarly, for the other tracking coil 16b, the focus driving force 3
0b is generated, and these two focus driving forces 30a,
The moment force TR30 having the support center 25 as the center of rotation is generated by 30b. This moment force TR30
Is a force in a direction opposite to the moment force AF23 by the focus coil 15 described above, so that when the moment force is superimposed, the resultant force can be reduced.

FIG. 6 is a diagram showing the principle of tilt suppression using the difference ΔzTR generated between the support center of the support member and the drive center when the upper ineffective wire layer of the tracking coil deviates from the effective portion of the magnetic circuit. It is. In FIG. 6, the tracking coils 16a, 16a
When a current is passed through b, a tracking driving force 26 is generated. However, when the movable portion including the objective lens 13 moves, the upper ineffective wire layer 27a of the tracking coil 16a deviates from the effective portion of the magnetic circuit. A difference ΔzTR is generated between the center 31 and the support center 25 of the support members 21a to 21d due to the distribution of the magnetic flux density. Accordingly, this difference is defined as the length of the arm, and a moment force TR32 with the support center 25 as the center of rotation is generated. This moment force TR32
Also, since the moment force AF23 is a force in the opposite direction to the moment force AF23 described above, the resultant force can be reduced by superimposing the moment forces.

FIG. 7 is a diagram showing the relationship between the height hmg of the magnet and each moment force. At a position where the movable portion including the objective lens 13 is located, the tracking coil height hTR
Is constant and the height hmg of the magnet is changed, as shown in FIG. 7, the moment force TR tends to increase as the height of the magnet decreases. On the other hand, the moment force AF23 due to the focus coil driving force 22 to be suppressed is substantially constant. Therefore, there is a magnet height hmg at which the moment force AF to be suppressed is equal to the moment force TR used for suppression. If the magnet height hmg is adopted, the resultant force of the moment is eliminated, and the objective lens 13 And an objective lens driving device having no inclination can be realized.

More specifically, when the height hmg of the magnets 18a, 18b is in the range of 1 to 10 mm, the height hTR of the tracking coils 16a, 16b is about 0.5 to 1.5 mm higher than the height hmg of the magnet. make low.

Similarly, the tracking coil is set so that the sum of the two moment forces TR30 (FIG. 5) and 32 (FIG. 6) used for suppression and the moment force AF23 (FIG. 3) to be suppressed is substantially zero. Even if the shapes of 16a and 16b, the total number of turns, and the shapes of magnets 18a and 18b and yoke 17 are optimized, unnecessary moment force can be almost eliminated. For this purpose, the thickness of the magnets 18a and 18b may be changed to change the magnetic flux distribution.

FIG. 8 is a diagram showing the relationship between the magnet height hmg and the tracking coil height hTR where the resultant of the moment forces is zero. Since the magnetic flux density distribution changes depending on the height hmg of the magnet, as shown in FIG. 8, when observing the relationship between the height hmg of the magnet and the tracking coil height hTR where the resultant of the moment force is zero, the magnet When the height hmg is smaller, the tracking height hTR tends to be relatively smaller. When this is represented by an approximate expression, hmg = -21.4 / hTR + 8.8 ± 0.3 mm. A magnet 18 with a height of hmg that satisfies this equation.
When the objective lens driving device is provided with the tracking coils 16a and 16b having the tracking coil height hTR, the inclination of the objective lens 13 can be suppressed. At this time, when the height hmg of the magnet is about 6 mm or more, the height hmg of the magnet and the height hTR of the tracking coil are substantially the same.
TR may be almost the same.

The tracking coil 16a shown in FIG.
The focus driving forces 29a and 29b of the 16b actually have a magnetic flux distribution. Therefore, the absolute amount is | 29a |> | 2.
9b |. Therefore, by changing the current or voltage flowing through the left and right tracking coils 16a and 16b, respectively,
The moment force TR30 can be changed without changing the tracking coil driving force 26. When a plurality of tracking coils are provided and an electric current is applied to each of the tracking coils independently, an objective lens driving device capable of controlling the force acting on the tracking coils and controlling the inclination of the objective lens 13 can be obtained.

[0031]

According to the present invention, the moment force due to the driving force of the focus coil when the objective lens is moved in the tracking direction can be canceled by the moment force due to the driving force of the rotary driving means also serving as the tracking driving force means. Therefore, the inclination of the objective lens can be suppressed to almost zero.

Therefore, with the same configuration as the components of the conventional objective lens driving device, the tilt of the objective lens is suppressed, and a good reproduction signal can be obtained and recorded correctly without increasing the number of components, that is, while keeping the cost unchanged. An objective lens drive is obtained.

Further, the attitude of the objective lens can be controlled by controlling the drive currents of the plurality of tracking coils.

When these objective lens driving devices are mounted on an optical disk device, an optical disk device capable of reading and writing a high-density disk can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic structure of an embodiment of an optical disk device according to the present invention.

FIG. 2 is a perspective view showing an appearance of an embodiment of an objective lens driving device according to the present invention.

FIG. 3 is a diagram showing the principle that when the objective lens is moved by Δy in the tracking direction and Δz in the focus direction, a moment force AF is generated by a focus coil driving force and the objective lens is tilted.

FIG. 4 shows a conventional magnetic circuit in which the height of the magnet is sufficiently higher than the movable range of the tracking coil in the vertical direction when the objective lens is moved by Δy in the tracking direction and Δz in the focusing direction. It is a figure showing the state of a tracking coil.

FIG. 5 is a diagram illustrating a principle of tilt suppression using a difference between forces applied to an upper invalid line layer and a lower invalid line layer of a tracking coil as a rotation driving unit.

FIG. 6 is a diagram illustrating a principle of tilt suppression using a difference ΔzTR generated between the tracking coil and a support center when an upper ineffective line layer of the tracking coil deviates from an effective portion of the magnetic circuit.

FIG. 7 is a diagram showing a relationship between a magnet height hmg and each moment force.

FIG. 8 shows the height h of the magnet when the resultant of the moment force is zero.
FIG. 7 is a diagram illustrating a relationship between mg and a tracking coil height hTR.

[Explanation of symbols]

 Reference Signs List 1 disc 2 turntable 3 disc tray 4 clamper 5 clamper holder 6 unit mechanical chassis 7 mechanical base 8a to 8d anti-vibration leg 9 optical head 10 objective lens driving device 11 bottom cover 12 top cover 13 objective lens 14 lens holding member 15 focus coil 16a , 16b Tracking coil 17 Yoke 18a, 18b Magnet 19a, 19b Small board 20 Support member mounting board 21a to 21d Support member 22 Focus coil drive force 23 Moment force AF 24 Drive center 25 Support center 26 Tracking coil drive force 27a, 27b Invalid line Layer 28a, 28b Driving force 29a, 29b Focus driving force 30 Moment force TR 31 Driving center 32 Moment force TR

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Yoshiaki Yamauchi 502, Kandachicho, Tsuchiura-shi, Ibaraki Pref. Machinery Research Laboratories, Hitachi, Ltd. Inside the Mechanical Research Laboratory (72) Inventor Michio Miura 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Visual Information Media Division, Hitachi, Ltd. (72) Inventor Nobuyuki Maeda No. 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture, Japan Inside (72) Inventor Akio Yabe Totsuka-ku, Yokohama-shi, Kanagawa 292 Yoshidacho Inside Hitachi Image Information System Co., Ltd. (72) Inventor Shozo Saegusa 2880 Kozu, Odawara City, Kanagawa Prefecture F-term, Storage System Division, Hitachi, Ltd. 5D118 AA13 BA01 DC03 EA02 EB15 EC04 EC07 ED02 ED05 ED07 ED08 EE01 EE05 FA29 FB20

Claims (8)

[Claims] 1. An objective lens driving device which is mounted on an optical head for roughly moving an optical disk in a radial direction and includes a movable portion including an objective lens and a support member supporting the movable portion, wherein the movable portion comprises: An objective lens, a magnetic circuit formed by a yoke and a magnet, a focus coil disposed in the magnetic circuit to finely move the objective lens in a focusing direction, and a tracking disposed in the magnetic circuit to finely move the objective lens in a tracking direction. An objective lens driving device including a coil, wherein the tracking coil is a flat coil arranged in substantially the same plane in the tracking direction and the focus direction, and the focus coil when the movable section moves in the tracking direction. A moment force in the opposite direction to the moment force due to the driving force is applied to the tracking coil. An objective lens driving apparatus characterized by comprising a tracking current supply means for generating a. 2. The objective lens driving device according to claim 1, wherein the tracking coil has a plurality of portions for guiding a current parallel to a tracking direction in a vertical direction, and when the tracking coil moves in the tracking direction, the tracking coil becomes ineffective above the tracking coil. An objective lens driving device, characterized in that the objective lens driving device is a tracking coil that utilizes a difference between forces acting on the line layer and the lower invalid line layer from the magnetic circuit. 3. The objective lens driving device according to claim 2, wherein the height hmg of the magnet is in a range of 1 to 10 mm, and the height hTR of the tracking coil is smaller than the height hmg of the magnet. Objective lens driving device characterized by being 1.5 mm lower. 4. The objective lens driving device according to claim 2, wherein the height hmg of the magnet and the height hTR of the tracking coil are within a range of 6 mm or more.
An objective lens driving device, which is substantially the same. 5. The objective lens driving device according to claim 2, wherein the height hmg of the magnet and the height h of the tracking coil are set.
TR: hmg = -21.4 / hTR + 8.8 ± 0.3 mm. An objective lens driving device. 6. The objective lens driving device according to claim 2, wherein the tracking coil is arranged in substantially the same plane in the tracking direction and the focus direction, and is provided with a plurality of flat-shaped coils that are supplied with current independently. An objective lens driving device, comprising: 7. The objective lens driving device according to claim 1, wherein the tracking coil has a plurality of upper and lower portions that guide a current in parallel with a tracking direction, and the upper invalid line layer of the tracking coil has an effective magnetic circuit. An objective lens driving device, characterized in that the objective lens driving device is a tracking coil that utilizes a difference generated between the support member and a support center when the support member deviates from the portion. 8. An optical disk device having the objective lens driving device according to claim 1 mounted on an optical head.