JP2003045054A - Optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup capable of highly accurately controlling the state of the optical pickup to an optical disk with excellent sensitivity. SOLUTION: The optical pickup 1 is provided with a movable part 11 having an objective lens 4 and also having a focus coil 5 and a tracking coil 6 for finely adjusting the state of the position of the objective lens to the optical disk or the like, supporting wires 7a-7d movably supporting the movable part, a fixed member 8 supporting the supporting wires and permanent magnets 9a-9d attached to a yoke part 17 and arranged at prescribed positions corresponding to the focus coil and the tracking coil. The focus coil 5 is divided into a plurality of small coils 18a-18d and arranged at the prescribed position of the movable part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup that records and reproduces information by focusing light on an optical disk recording surface with an objective lens.

[0002]

2. Description of the Related Art Optical pickups are used in optical disk devices such as optical disk reproducing devices and optical disk recording / reproducing devices. The optical pickup is a device for condensing light such as laser light on a recording surface of an optical disc which is a recording medium to record and reproduce information. The optical pickup is provided with an objective lens for condensing light, and a focus coil and a tracking coil for finely adjusting the position of the objective lens with respect to the optical disc. The focus coil moves the objective lens in the focus direction (direction parallel to the optical axis of the objective lens),
The tracking coil can move the objective lens in the tracking direction of the optical disc (radial direction of the optical disc). As a result, the state of the objective lens with respect to the optical disc, such as the position and posture, is finely adjusted.

[0003]

However, since the number of focus coils provided in the conventional optical pickup is one, the size of the focus coil is increased and the number of windings is increased. As a result, the movable optical pickup is moved. The part was heavy. In addition, since the density of the magnetic flux is small in the parts on both sides of the focus coil when viewed from the permanent magnet side, and the magnetic flux density is low, the magnetic efficiency is reduced. For these reasons, it has been difficult for the conventional optical pickup to control the position and posture of the movable portion with high accuracy and sensitivity. Further, since there is only one focus coil, it is difficult to perform the radial tilt adjustment and the tangential tilt adjustment described later.

The present invention has been made to solve the above problems, and an object thereof is to provide an optical pickup capable of controlling the state of the optical pickup with respect to an optical disc with high accuracy and high sensitivity. .

[0005]

In order to achieve the above object, an optical pickup according to the present invention has an objective lens for condensing light on a recording surface of an optical disc, and a state such as a position of the objective lens with respect to the optical disc. A movable part having a focus coil and a tracking coil for finely adjusting, a support wire for movably supporting the movable part, a fixed member for supporting the support wire, and a yoke part made of a magnetic material, And a permanent magnet arranged at a predetermined position corresponding to the focus coil and the tracking coil. Then, the focus coil is divided into a plurality of small coils and arranged at a predetermined position of the movable portion. The focus coil is preferably composed of four small coils arranged at the four corners of the movable part. In a preferred embodiment, the focus coil includes one small coil in which the first windings are electrically connected and two small coils in which the second winding is electrically connected to each other. It is composed by. The radial tilt of the optical pickup can be adjusted by individually controlling the current flowing through the first winding and the current flowing through the second winding. In another embodiment, the windings of the four small coils are electrically independent from each other, and an individual current is passed through each winding to individually control the operation of each small coil, thereby adjusting the radial tilt of the optical pickup. It is preferable to enable tangential tilt adjustment. Further, a plurality of focus coil yokes forming the yoke portion are provided so as to project, and the focus coil yokes are arranged so as to be inserted into the hollow portions of the focus coil bobbins around which the respective small coils are wound. Preferably. As a specific embodiment, the movable part includes a lens support body provided with an objective lens and a coil support body having a plurality of small coils provided at predetermined positions, and the lens support body is mounted on the coil support body. Are integrated into one. A tracking coil is provided on at least one of the coil support and the lens support.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment according to the present invention will be described below with reference to FIGS. Figure 1
2 is a perspective view of an optical pickup according to an embodiment of the present invention, and FIGS. 2 and 3 are a plan view and an exploded perspective view of the optical pickup, respectively. FIG. 4 is a perspective view showing a movable part of the optical pickup, and FIG. 5 is an exploded perspective view of the movable part shown in FIG.

The optical pickup 1 of the present invention used in the optical disk device is movable by a moving mechanism (not shown) while being controlled in the radial direction of the optical disk as a recording medium. As the optical disc, for example, a CD,
CD-ROM, CD-R, CD-RW, MD, MO, D
VD-ROM, DVD-RAM, DVD-R, DVD-
RW, etc. As shown in FIGS. 1 to 5, the optical pickup 1 has a movable portion 11, support wires 7a to 7d, a fixed member 8 and permanent magnets 9a to 9d. The movable part 11 has an objective lens 4 for condensing light on the recording surface of the optical disc, and a focus coil 5 and a tracking coil 6 for finely adjusting the state of the objective lens 4 with respect to the optical disc, such as position and orientation. is doing. In addition,
For convenience of explanation, the direction parallel to the optical axis B of the objective lens 4 is X.
Direction. The Z direction is the direction orthogonal to the X direction and the tracking direction (radial direction of the optical disk), and the direction orthogonal to the X and Z directions is the Y direction.

The focus coil 5 moves the movable portion 11 in the focus direction (the direction parallel to the optical axis B of the objective lens 4 (X direction)), and the tracking coil 6 moves the movable portion 1
1 can be moved in the tracking direction (radial direction (Z direction) of the optical disc). The movable part 11 is a lens support 2 provided with an objective lens 4.
And a coil support 3 mounted on the lens support 2 with the focus coil 5 arranged at a predetermined position.
By mounting the lens support 2 on the coil support 3, the lens support 2 is integrally formed. Also, the tracking coil 6
Is provided on at least one of the coil support 3 and the lens support 2 (here, on the lens support 2). The lens support 2 and the coil support 3 allow the movable portion 1 to move.
The main body portion 10 is composed of 1. By providing the objective lens 4, the focus coil 5 and the tracking coil 6 on the main body portion 10, the movable portion 11 is configured.

The lens support 2 is integrally formed of a resin material or the like. The objective lens 4 supported by the lens support 2 focuses light such as laser light on the recording surface of the optical disc. The lens supporting body 2 has a pair of tracking coil supporting portions 12 which are arranged 180 degrees apart in opposite directions and are formed so as to slightly project outward. The two tracking coils 6 are attached to the lens support 2 while being supported by the pair of tracking coil support portions 12, respectively. Although the tracking coil 6 is provided on the lens support 2, the coil support 3
(Or may extend over both the lens support 2 and the coil support 3).

The coil support 3 is integrally formed of a resin material having an insulating property and supports the focus coil 5. The coil support body 3 has a substantially rectangular shape in a plan view, and bobbin 21 for focus coil is integrally formed at each of four corner portions 19a to 19d thereof so as to project upward. The four focus coil bobbins 21 each have a rectangular tubular shape having hollow portions 28a to 28d, have substantially the same shape, and are regularly arranged.
The lens support 2 is integrally formed with a plurality of engaging portions 15, and the coil support 3 is also integrally formed with a plurality of engaging portions 16. The engaging portions 15 and 16 are respectively engaged with the engaged portions of the other party, and the engaging portions 15 and 1
It is possible to engage other engaging parts other than 6 with other engaged parts on the other side. As a result, the lens support 2 is positioned at a predetermined position relative to the coil support 3 to form the movable portion main body 10. In addition, the movable part main body 10 of the present embodiment is divided into the lens support 2 and the coil support 3 to be combined into separate parts, but may be combined into one part.

A plurality of (here, four) support wires 7a
7d support the movable part 11 so that movement is possible. The fixing member 8 is fixed to a fixed side such as a case and a base member (not shown) of the optical disk device to support the supporting wires 7a to 7d, and is made of an insulating material in a block shape,
It is formed in a predetermined shape such as a plate shape. The focus coil 5 and the tracking coil 6 are the support wires 7
It is electrically connected to a control circuit (not shown) using a to 7d. The permanent magnets 9a to 9d are attached to a yoke portion (yoke portion) 17 made of a magnetic material, and are arranged at predetermined positions corresponding to the focus coil 5 and the tracking coil 6.

The focus coil 5 includes a plurality of (four in this case) small coils 18a to 18d so that the state of the movable portion 11 (position, posture, etc. of the movable portion 11) can be finely adjusted.
And is arranged at a predetermined position of the movable portion 11. Four small coils 18 forming the focus coil 5
a to 18d are predetermined positions of the coil support 3 (for example,
It is formed by winding a winding wire around the four focus coil bobbins 21 arranged at the four corners 19a to 19d) of the coil support 3. The coil support 3
The four small coils 18a to 18d may be arranged at positions other than the four corners 19a to 19d. The four small coils 18a to 18d are connected to the first winding 20
a Two small coils 1 of which one is electrically connected to the other
8a and 18b can be distinguished from the other two small coils 18c and 18d to which the second windings 20b are electrically connected.

The yoke portion 17 is fixed to a fixed side such as a case or a base member (not shown) of the optical disk device and is integrally formed in a predetermined shape. Yoke part 17
Is a base 25 formed in a rectangular plate shape and attached to the fixed side of the optical disk device, a pair of permanent magnet yokes 26 fixed to the base 25 at substantially right angles and facing each other, and a pair of permanent magnets for permanent magnets. A plurality of (four in this case) focus coil yokes 27 are arranged between the yokes 26. Since the yoke portion 17 is integrally formed, it is easy to manufacture. Four focus coil yokes 27
Are provided so as to project from the base 25, and are arranged in parallel with the permanent magnet yoke 26 and at regular positions. The four focus coil yokes 27 are arranged so as to be inserted into the hollow portions 28a to 28d of the focus coil bobbin 21 around which the four small coils 18a to 18d are wound. As a result, the small coil 18
a to 18d can generate strong magnetism.

Of the four permanent magnets, two permanent magnets 9
The a and 9c are arranged side by side inside one of the permanent magnet yokes 26. The small coil 18a constitutes a magnetic circuit between the focus coil yoke 27 inserted into the hollow portion 28a of the focus coil bobbin 21 and the permanent magnet 9a. The small coil 18c constitutes a magnetic circuit between the focus coil yoke 27 inserted into the hollow portion 28c of the focus coil bobbin 21 and the permanent magnet 9c. The permanent magnets 9b and 9d are arranged side by side inside the other permanent magnet yoke 26. Small coil 1
8b is a hollow portion 28b of the focus coil bobbin 21.
Focus coil yoke 27 and permanent magnet 9 inserted into
A magnetic circuit is formed with b. Small coil 18d
Constitutes a magnetic circuit between the focus coil yoke 27 inserted into the hollow portion 28d of the focus coil bobbin 21 and the permanent magnet 9d. Each of the two tracking coils 6 is wound such that the winding direction is perpendicular to the winding directions of the small focusing coils 18a to 18d. One of the tracking coils 6 is arranged at an intermediate position between the magnetic circuit formed by the small coil 18a and the permanent magnet 9a and the magnetic circuit formed by the small coil 18c and the permanent magnet 9c. The other tracking coil 6 is arranged at an intermediate position between the magnetic circuit formed by the small coil 18b and the permanent magnet 9b and the magnetic circuit formed by the small coil 18d and the permanent magnet 9d. The permanent magnets 9a, 9c and 9b, 9d arranged in parallel, and the opposing permanent magnets 9a, 9b and 9c, 9d are arranged so that their polarities are opposite to each other.

The support wires 7a to 7d are provided on both sides of the movable portion 11 in parallel with the Y direction, two wires each, for a total of four wires. One end of each of the support wires 7a to 7d is the fixing member 8
And the other end is fixed to the movable part 11 side. In this way, the movable portion 11 is attached in a state of being floated in the space between the fixed member 8 and the yoke portion 17 via the support wires 7a to 7d, so that the movable portion 11 is moved or swung to move in that state (position, position, Posture, etc.) can be changed freely. In the movable part 11, the small coils 18a to 18d
The coil support 3 for supporting the
Located on the side. So that the objective lens 4 faces outward
The lens support 2 is located on the side away from the base 25.

The first winding 20a composed of the small coils 18a and 18b, the second winding 20b composed of the small coils 18c and 18d, and the two tracking coils 6 are electrically connected to a control circuit (not shown). Connected to each other.
The electrical connection between these windings and coils and the control circuit may utilize the support wires 7a to 7d and the additional support wire, or may be performed by another method.

By the way, when the track pitch and the information recording density of the optical disk are not so large, control of the posture of the movable portion of the optical pickup 1 is not required to be highly accurate in many cases. However, in the case of an optical pickup used for an optical disc that requires high density of recorded information, so-called tilt adjustment for finely adjusting the inclination of the optical axis B of the objective lens 4 with respect to the optical disc is required in recent years. It's coming. This tilt adjustment includes radial tilt adjustment and tangential tilt adjustment. The radial tilt adjustment is a fine adjustment of the tilt of the optical axis B as shown by an arrow C in a plane (X and Z planes) orthogonal to the recording surface of the optical disc and in the radial direction (radial direction) of the optical disc. It is to be. The tangential tilt adjustment is performed by adjusting the tilt of the optical axis B in a plane (X, Y plane) orthogonal to the recording surface of the optical disc and in the tangential direction (tangential direction) of the track as indicated by an arrow D. It is a fine adjustment.

In order to perform accurate recording and reproduction of recorded information of high density, it is necessary to accurately match the spot condensed by the objective lens 4 with the position of the pit on the recording surface of the optical disc. For that purpose, it is particularly required to perform the radial tilt adjustment with high accuracy. If tangential tilt adjustment is performed in addition to the radial tilt adjustment, information can be recorded and reproduced more accurately. Therefore, in the optical pickup 1 of the present embodiment,
The first winding 20a (that is, the small coils 18a, 18
The radial tilt adjustment of the optical pickup 1 is enabled by individually controlling the current flowing in b) and the current flowing in the second winding 20b (that is, the small coils 18c and 18d).

The optical pickup 1 has an optical system (not shown). This optical system has a light source such as a semiconductor laser that generates laser light, a photodetector, a reflection mirror, a lens, and a diffraction grating. The objective lens 4 is also included in this optical system. The photodetector receives the laser light reflected on the recording surface of the optical disc, detects a reproduction signal, detects the tilt of the recording surface of the optical disc, and also detects a focus error signal, a tracking error signal, and the like.
When controlling the state of the optical pickup 1 (that is, the position, orientation, etc. of the movable portion 11), the detection result regarding the inclination of the recording surface of the optical disc detected by the photodetector is converted into an electric signal by the conversion portion. And outputs it as an electric signal to the control unit. The control unit controls the current flowing through the focus coil 5 and the tracking coil 6 based on the electric signal from the conversion unit. As a result, the movable section 11 moves in the focus direction and the tracking direction, and the position thereof is controlled. When performing the radial tilt adjustment, the control unit controls the first winding 20 based on the electric signal from the conversion unit.
The current flowing through a and the current flowing through the second winding 20b are individually controlled. As a result, the movable portion 11 is moved to the arrow C.
Since it swings in the direction indicated by the arrow to change its posture, the tilt of the optical axis B of the objective lens 4 (the tilt in the direction of arrow C) is finely adjusted. As a result, the radial tilt adjustment of the optical pickup 1 is performed.

When assembling the optical pickup 1, as shown in FIG. 5, the objective lens 4 is attached to the lens support 2, and the two tracking coils 6 each having a winding wound in a predetermined shape in advance, They are attached to the pair of tracking coil supporting portions 12, respectively. On the other hand, in the coil support body 3, of the four focus coil bobbins 21, the first winding 20a is attached to two focus coil bobbins 21.
Is wound to form the small coils 18a and 18b. The first winding 20a of the small coil 18a and the first winding 20a of the small coil 18b are electrically connected. Similarly, the second winding 20b is wound around the other two focus coil bobbins 21 to form the small coils 18c and 18d. The second winding 20b of the small coil 18c and the second winding 20b of the small coil 18d are electrically connected. The winding work of the windings 20a and 20b can be easily performed because there is no restriction on the surrounding space. In this way, the coil support 3 has four small coils 18a-18
d is provided.

Next, the lens support 2 having the objective lens 4 and the tracking coil 6 is mounted on the coil support 3 having the small coils 18a to 18d. The engaging portion 15 of the lens support 2 and the engaging portion 16 of the coil support 3 are
Since they engage with the mating engaged parts respectively, the lens support 2 can be accurately positioned and fixed to the coil support 3. In this way, the movable part 11 shown in FIG. 4 is assembled. After that, as shown in FIGS. 1 and 2, the support wires 7 a to 7 d fixed to the fixing member 8 are fixed to the movable portion 11. Small coils 18a and 18b, small coils 18c and 18d, and two tracking coils 6
Respectively are electrically connected to the control circuit. In this way, the assembly of the optical pickup 1 is completed.

Next, the operation of the optical pickup 1 will be described with reference to FIGS. First, in the optical disk device, the optical pickup 1 is moved to a desired position by the moving mechanism while the optical disk is being rotationally driven by the drive motor. Then, the laser light generated by the optical system is focused on the recording surface by the objective lens 4 to record and reproduce information on the optical disc. Objective lens 4
To move in the focus direction (X direction),
A control current according to the moving direction and the moving amount is uniformly supplied to the small coils 18a to 18d. Then, the movable portion 1 is caused by the electromagnetic force generated by the small coils 18a to 18d.
1 moves in the focus direction (X direction) with respect to the optical disc to finely adjust the position of the objective lens 4. Similarly, if a control current is supplied to the tracking coil 6, the movable portion 1
1 moves in the tracking direction (Z direction) of the optical disc to finely adjust the position of the objective lens 4.

When the tilt adjustment is performed, the current flowing through the first winding 20a of the one small coil 18a, 18b and the current flowing through the second winding 20b of the other small coil 18c, 18d are The control unit controls each individually. As a result, the electromagnetic force generated by the small coils 18a and 18b and the electromagnetic force generated by the small coils 18c and 18d cause the movable portion 11 to swing in the direction indicated by the arrow C to change its posture. The tilt of the optical axis B can be finely adjusted. By doing this, the optical pickup 1
It is possible to adjust the radial tilt of.

As a modified example of this embodiment, the windings are separately wound around the four small coils 18a, 18b, 18c, 18d, and the small coils 18a, 18b, 18 are formed.
It is preferable that the windings of c and 18d are electrically independent from each other, and an individual current is passed through each winding to individually control the operation of each small coil. In this way, the small coil 18
Since the movable portion 11 swings in the directions indicated by the arrow C and the direction indicated by the arrow D by the electromagnetic forces individually generated by a, 18b, 18c, and 18d, the posture thereof is changed.
The objective lens 4 also swings in the arrow C and arrow D directions.
Thereby, the tilt of the optical axis B of the objective lens 4 (the tilt in the arrow C direction and the tilt in the arrow D direction) can be finely adjusted,
Both the radial tilt adjustment and the tangential tilt adjustment of the optical pickup 1 are possible.

In the present embodiment and the modified example, the focus coil 5 is divided into four small coils 18a to 18d and arranged at a predetermined position of the movable portion 11. As a result, the focus coil 5 can be downsized as a whole, the amount of windings can be reduced, the weight of the focus coil 5 can be reduced, and the current supplied to the focus coil 5 can be reduced. Also, the small coil 18a
.About.18d are located respectively near the permanent magnets 9a to 9d as a whole, the magnetic flux M passes through the entire coil so that there is no portion having a small magnetic flux density (FIG. 2), and the magnetic efficiency is improved. Increase. In this way, the small coils 18a-1
The magnetic efficiency of the focus coil 5 composed of 8d is increased,
Moreover, the weight of the movable portion 11 is also reduced. As a result, since the movable portion 11 can be moved at high speed and with high accuracy, the state of the optical pickup 1 with respect to the optical disk (the movable portion 11
Position, posture, etc.) can be controlled with high precision and sensitivity. In the present embodiment, the case where the objective lens 4 is the “lens center type” optical pickup 1 in which the objective lens 4 is arranged substantially in the center of the movable portion 11 has been described.
It may be a “lens offset type” optical pickup in which the objective lens is arranged outside the movable portion. In addition,
In the drawings, the same reference numerals indicate the same or corresponding parts.

[0026]

Since the present invention is configured as described above, the state of the optical pickup with respect to the optical disk can be controlled with high accuracy and sensitivity.

[Brief description of drawings]

FIG. 1 is a perspective view of an optical pickup.

FIG. 2 is a plan view of the optical pickup.

FIG. 3 is an exploded perspective view of the optical pickup.

FIG. 4 is a perspective view showing a movable portion of the optical pickup.

5 is an exploded perspective view of a movable portion shown in FIG.

[Explanation of symbols]

1 Optical pickup 2 lens support 3 coil support 4 Objective lens 5 Focus coil 6 Tracking coil 7a to 7d Support wire 8 fixing members 9a-9d permanent magnet 11 Moving part 17 Yoke 18a, 18b One small coil (small coil) 18c, 18d The other small coil (small coil) 19a to 19d corners 20a first winding 20b second winding 21 Focus coil bobbin 27 Focus coil yoke 28a-28d hollow part

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5D118 AA13 BA01 DC03 EB07 ED05                       EE01 EE03

Claims (6)

[Claims] 1. A movable part having an objective lens for condensing light on a recording surface of an optical disc, and a focus coil and a tracking coil for finely adjusting a state of the objective lens with respect to the optical disc. A supporting wire for movably supporting the movable portion, a fixed member for supporting the supporting wire, and a yoke portion made of a magnetic material, and attached to a predetermined position corresponding to the focus coil and the tracking coil. An optical pickup comprising a permanent magnet, wherein the focus coil is divided into a plurality of small coils and arranged at a predetermined position of the movable portion. 2. The optical pickup according to claim 1, wherein the focus coil is composed of four small coils respectively arranged at four corners of the movable portion. 3. The focus coil comprises one of the two small coils having first windings electrically connected to each other and the other of the two small coils having second windings electrically connected to each other. A small coil is provided, and the radial tilt of the optical pickup can be adjusted by individually controlling the current flowing through the first winding and the current flowing through the second winding. The optical pickup according to claim 1 or 2. 4. The radials of the optical pickup are controlled by electrically separating the windings of the four small coils from each other, and individually controlling the operation of each of the small coils by supplying an individual current to each winding. The optical pickup according to claim 1 or 2, wherein tilt adjustment and tangential tilt adjustment are possible. 5. A plurality of focus coil yokes forming the yoke portion are provided so as to project, and the focus coil yokes are respectively inserted into the hollow portions of the focus coil bobbins around which the small coils are wound. The optical pickup according to any one of claims 1 to 4, wherein the optical pickup is arranged as follows. 6. The movable part includes a lens support body provided with the objective lens and a coil support body provided with the plurality of small coils at predetermined positions, and the lens support body is provided on the coil support body. The optical pickup according to claim 1, wherein the tracking coil is provided on at least one of the coil support and the lens support while being mounted and integrally configured. .