JP2001256660A - Optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup, capable of controlling (or preventing) the optical axis of an objective lens from tilting from a reference axis. SOLUTION: The optical pickup 1 is provided with a damper base, an actuator composed of a fixing part 5a and a movable part 5b and four suspension wires. The fixing part 5a is composed of a U-shaped yoke 51 and a pair of magnets 52 joined to it, and the movable part 5b is composed of a lens holder, an objective lens, a pair of tracking coils 55a, 55b and a focusing coil 56. When the movable part 5b is maximum displaced toward at least one end side in the optical axis direction and is maximum displaced toward the other end side, absolute values of electromagnetic force F1, F5 exerting on sides 551, 555 of the tracking coils 55a, 55b are constituted as so to differ from the absolute values of electromagnetic force F3, F7 which act on sides 553, 557.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an optical pickup.

[0002]

2. Description of the Related Art An optical pickup is mounted on various optical disk devices (devices for recording and / or reproducing optical disks) provided (connected) to a personal computer or the like.

The optical pickup has a lens holder, a damper base for supporting the lens holder movably via four suspension wires, and a yoke provided with a magnet (permanent magnet). .

The lens holder supports an objective lens, and is provided with a tracking coil and a focusing coil wound in a substantially rectangular shape.

FIGS. 7 to 9 are front views schematically showing a magnet, a tracking coil, and a focusing coil of a conventional optical pickup, respectively.

For convenience of explanation, as shown in FIGS.
Assuming an X-axis, a Y-axis, and a Z-axis (XYZ coordinate system) orthogonal to each other, the radial direction (tracking direction: radial direction) of the optical disc (not shown) mounted with the X-axis direction and the Y-axis direction Is the longitudinal direction (tangential direction) of the suspension wire, and the Z-axis direction is the reference axis direction (focusing direction). The direction of the reference axis is an ideal direction of the optical axis of the objective lens.

When current does not flow through each of the pair of tracking coils 120a, 120b and focusing coil 130 of optical pickup (optical head) 100, a lens holder (objective lens) not shown
It is located at the reference position shown in FIG. Note that the magnetic flux (magnetic field) from the magnet 110 is directed from the front side to the back side of the paper in FIGS. 7 to 9.

A pair of tracking coils 120a, 120
When the current i1 (direction is indicated by an arrow in the figure) flows through the tracking coils 120b, the electromagnetic forces F11, F12, F13, and F14 are applied to the sides 121, 122, 123, and 124 of the tracking coil 120a on the right side in FIG. (Directions are indicated by arrows in the figure) act on the respective sides 125, 126, 127 and 128 of the tracking coil 120b on the left side in FIG. 7 to generate electromagnetic forces F15, F16 and F17, respectively.
And F18 (directions are indicated by arrows in the figure) act.

In this case, the electromagnetic force F11 acting on the side 121 of the tracking coil 120a and the electromagnetic force F13 acting on the side 123 have opposite directions and have the same absolute value, and therefore cancel each other.

On the other hand, the magnetic flux is applied to the entire side 124 while the magnetic flux is applied to only a part of the side 122. Therefore, the absolute value of the electromagnetic force F12 acting on the side 122 and the side 124 The absolute value of the electromagnetic force F14 acting on the
> | F12 |, and these electromagnetic force F12 and electromagnetic force F1
The resultant force of 4 is a force directed to the right side in FIG.

Similarly, the electromagnetic force F15 acting on the side 125 of the tracking coil 120b and the electromagnetic force F17 acting on the side 127 have opposite directions and have the same absolute value, and therefore cancel each other.

On the other hand, the magnetic flux is applied to the side 126 entirely, while the magnetic flux is applied to only a part of the side 128. Therefore, the absolute value of the electromagnetic force F16 acting on the side 126 and the side 128 The absolute value of the electromagnetic force F18 acting on the
> | F18 |, and these electromagnetic force F16 and electromagnetic force F1
The resultant force of 8 is a force directed to the right side in FIG.

As a result, the lens holder is displaced (moved) rightward in FIG. 7, and the positional relationship between the magnet 110 and the tracking coils 120a, 120b and the focusing coil 130 is as shown in FIG. In addition,
The amount of displacement (movement) of the lens holder to the right in FIG.

As shown in FIG. 8, when a current i2 (direction is indicated by an arrow in the drawing) flows through the focusing coil 130, an electromagnetic force F19 (in the direction shown in FIG. 8) directed upward in FIG. (Indicated by the middle arrow). The electromagnetic force F19 acts on a position (point) 160 that is apparently intermediate in the X-axis direction of the magnet 110 in the focusing coil 130 and intermediate in the optical axis direction of the objective lens in the focusing coil 130.

In this case, the lens holder is positioned at the reference position (FIG. 7).
8) to the right side in FIG.
0 does not match the center of gravity G of the lens holder,
From the left side of FIG. Therefore, the electromagnetic force F
Numeral 19 acts not on the center of gravity G of the lens holder but on a position 160 that is apparently leftwardly separated from the center of gravity G to the left in FIG.

Due to the electromagnetic force F19, the lens holder is displaced upward in FIG. 8 and is rotated clockwise in FIG. 8 by a predetermined amount (predetermined angle) about the center of gravity G, so that the magnet 110 and the tracking coils 120a, The positional relationship between the focusing coil 120b and the focusing coil 130 is as shown in FIG. That is, the lens holder is displaced from the reference position (see FIG. 7) to the upper right in FIG. 9, and the optical axis 140 of the objective lens is inclined with respect to the reference axis 150 in the clockwise direction in FIG. .

Similarly, when the lens holder is displaced from the reference position (see FIG. 7) to the lower right, upper left, and lower left in FIG. 9, the optical axis 140 of the objective lens is set to the reference axis 150, respectively.
With a predetermined angle.

However, when the optical axis 140 of the objective lens is tilted with respect to the reference axis 150, the optical axis 140 and the light beam incident on the objective lens become non-parallel, thereby causing aberration and causing the characteristics of the optical pickup (for example, , Recording / reproducing characteristics).

If the inclination angle (inclination angle) β of the optical axis 140 of the objective lens becomes large, it may not be possible to perform recording or reproduction.

[0020]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical pickup capable of suppressing (or preventing) the optical axis of an objective lens from inclining from a reference axis.

[0021]

This and other objects are achieved by the present invention which is defined below as (1) to (5).

(1) A tracking coil, a focusing coil, an objective lens, a lens holder supporting the tracking coil, the focusing coil and the objective lens, and the lens holder being displaceable via a plurality of suspension wires. An optical pickup comprising a supporting damper base, a yoke, and a magnet mounted on the yoke, wherein the lens holder is at least displaced at least toward one end in the optical axis direction of the objective lens. In the tracking coil, at least a part of the portion of the tracking coil where the electromagnetic force in the optical axis direction of the objective lens acts is located outside the magnet in the optical axis direction from one end of the magnet in the optical axis direction of the objective lens. The lens holder is located at least the other end of the objective lens in the optical axis direction. When the maximum displacement toward the side,
At least a part of the tracking coil on which the electromagnetic force in the optical axis direction of the objective lens acts is located outside the magnet in the optical axis direction from the other end of the magnet in the optical axis direction of the objective lens. An optical pickup characterized in that the optical pickup is configured to:

(2) A tracking coil, a focusing coil, an objective lens, a lens holder supporting the tracking coil, the focusing coil and the objective lens, and the lens holder being displaceable via a plurality of suspension wires. An optical pickup having a damper base to be supported, a yoke, and a magnet installed on the yoke, wherein a surface of the tracking coil at one end in the optical axis direction of the objective lens is
In the same direction, the surface of the magnet beyond the one end of the objective lens in the optical axis direction, and the surface of the tracking coil on the other end side in the optical axis direction of the objective lens is in the same direction. An optical pickup, wherein the lens holder is displaced within a range exceeding the other end in the optical axis direction.

(3) A tracking coil, a focusing coil, an objective lens, a lens holder supporting the tracking coil, the focusing coil and the objective lens, and the lens holder being displaceable via a plurality of suspension wires. An optical pickup comprising a supporting damper base, a yoke, and a magnet mounted on the yoke, wherein the lens holder is at least displaced at least toward one end in the optical axis direction of the objective lens. And when the displacement is maximized toward the other end, the absolute value of the electromagnetic force acting on the tracking coil toward the one end in the optical axis direction of the objective lens and the absolute value of the electromagnetic force toward the other end. An optical pickup characterized in that it is different from the above.

(4) A tracking coil, a focusing coil, an objective lens, a lens holder supporting the tracking coil, the focusing coil and the objective lens, and the lens holder being displaceable via a plurality of suspension wires. An optical pickup including a supporting damper base, a yoke, and a magnet installed on the yoke, wherein the lens holder is arranged such that the lens holder is positioned from a reference position with respect to an optical axis direction of the objective lens and an optical axis of the objective lens. When the lens holder is displaced in the vertical direction, when the lens holder is displaced maximally toward at least one end in the optical axis direction of the objective lens and when displaced maximally toward the other end, The focusing coil attempts to incline the optical axis of the objective lens in a predetermined direction from a reference axis. The tracking coil is configured such that an electromagnetic force is applied to the tracking coil so as to tilt the optical axis of the objective lens from a reference axis in a direction opposite to the predetermined direction. Optical pickup.

(5) When the lens holder is located at a reference position in the optical axis direction of the objective lens, a portion of the tracking coil on which the electromagnetic force in the optical axis direction of the objective lens acts is the magnet. The optical pickup according to any one of (1) to (4), wherein the optical pickup is configured not to protrude from both ends of the objective lens in the optical axis direction in the optical axis direction.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical pickup according to the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.

FIG. 1 is a plan view showing an embodiment of the optical pickup of the present invention, FIG. 2 is a sectional view taken along line AA in FIG. 1, and FIGS. FIG. 3 is a front view schematically showing a magnet, a tracking coil, and a focusing coil of the optical pickup.

For convenience of explanation, as shown in FIGS.
Assuming an X-axis, a Y-axis, and a Z-axis (XYZ coordinate system) orthogonal to each other, the radial direction (tracking direction: radial direction) of the optical disc (not shown) mounted with the X-axis direction and the Y-axis direction Is the longitudinal direction (tangential direction) of the suspension wire, and the Z-axis direction is the reference axis direction (focusing direction). The direction of the reference axis is an ideal direction of the optical axis of the objective lens.

As shown in FIG. 1, an optical pickup (optical head) 1 includes a damper base 4 and an actuator 5
And four suspension wires (suspension springs) 7.

The optical pickup 1 is installed (mounted) on an optical disk device (device for recording and / or reproducing information on an optical disk) (not shown) so as to be able to reciprocate in the radial direction of the mounted optical disk.

In the present invention, an optical disk is a CD,
CD-ROM, CD-R, CD-RW, DVD, DVD
-ROM, DVD-R, DVD-RAM, DVD-RW
In addition to ordinary optical disks (optical disks in a narrow sense), the concept includes a magneto-optical disk.

The actuator 5 is composed of a fixed part 5a and a movable part 5b. The fixing portion 5a includes a U-shaped yoke 51 and a pair of magnets (permanent magnets) 52, 52 joined to the yoke 51.

The yoke 51 includes a pair of tracking coils 55a and 55b and a focusing coil 5 described later.
6, and a pair of magnets 52, 52 are provided with tracking coils 55a, 55b.
And a common magnet corresponding to the focusing coil 56.

As shown in FIGS. 1 and 2, each of the magnets 52 has a flat plate shape.
The shape of the surface 521 facing (opposing) the tracking coils 55a and 55b and the focusing coil 56 is
Each is a substantially rectangle (square). The dimensions of the two magnets 52 are equal.

One of these magnets 52 is joined to the inner surface of one of the pair of side walls 512 and 513 of the yoke 51 and the other is connected to the other side wall 5.
13 is joined to the inner surface.

The magnets 52 are arranged such that the right side in FIG. 1 has an S pole and the left side has an N pole.

As shown in FIG. 2, a predetermined gap is provided between the bottom surface 511 of the yoke 51 and the lower surface of each magnet 52 in FIG.

As shown in FIGS. 1 and 2, the magnet 52 and the yoke 51 (fixed portion 5a) are arranged such that the short sides 522 and 523 of the magnet 52 are aligned with an optical axis 541 (Z axis) of the objective lens 54 described later. Are arranged inside the lens holder 53, which will be described later, such that the long sides 524 and 525 (surface 521) are perpendicular to the suspension wire 7 (Y axis).

The movable part 5 b of the actuator 5 is set on the lens holder 53 having the lens support part 531, the objective lens (condensing lens) 54 supported by the lens support part 531 of the lens holder 53, and the lens holder 53. And a pair of tracking coils 55a and 55b and a focusing coil 56.

The lens support 531 is provided with a lens holder 53
1 is formed at an intermediate portion of the lens holder 53 in the X-axis direction. That is, the objective lens 54 is located at the right end in FIG. 1 of the lens holder 53 and at the middle of the lens holder 53 in the X-axis direction.

Further, the focusing coil 56 is provided as shown in FIG.
It is wound in a substantially square shape clockwise.

The focusing coil 56 is provided inside the lens holder 53. The side 561 of the focusing coil 56 is connected to the side wall 51 of the yoke 51.
2 and the side wall 513.

The tracking coils 55a and 55a
5b are each wound in a substantially rectangular shape.

In this case, the tracking coil 55a
2, the tracking coil 55b is wound clockwise.
Are wound counterclockwise in FIG. 2 and are electrically connected.

The tracking coils 55a and 5a
5b are inside the lens holder 53, respectively.
It is installed on the right side of the focusing coil 56 in FIG. Then, the tracking coils 55a and 55b
Are arranged between the side walls 512 and 513 of the yoke 51, respectively. The tracking coil 55
a and the tracking coil 55b are juxtaposed in the X-axis direction.

The tracking coil 55a and the tracking coil 55b have the same configuration except that the winding directions of the coils are reversed.

The movable part 5b is attached to the damper base 4,
It is displaceably supported via four suspension wires 7. Each suspension wire 7 includes a tracking coil 55a, 55b and a focusing coil 5
It also functions as an electric wire (conductor) for energizing 6.

In this case, the movable part 5b (the objective lens 54)
Is set (adjusted) so that the optical axis 541 of the objective lens 54 is parallel to the reference axis (Z axis) in a state where power is not supplied to any of the tracking coils 55a and 55b and the focusing coil 56.

By energizing the tracking coils 55a and 55b, the tracking coils 55a and 55b
The movable portion 5b is displaced (moved) in the X-axis direction, that is, in the radial direction (tracking direction: radial direction) of the loaded optical disk.

When the focusing coil 56 is energized, an electromagnetic force acts on the focusing coil 56, whereby the movable portion 5b moves in the Z-axis direction (reference axis direction), that is, in the optical axis direction of the objective lens 54. (Focusing direction).

The optical pickup 1 has a not-shown laser diode (light emitting portion) for emitting a laser beam for irradiating the optical disc, and a not-shown photodiode (light receiving portion) for receiving reflected light from the optical disc. .

In the present invention, the relative relationship between the pair of magnets 52, 52 of the optical pickup 1 and the pair of tracking coils 55a, 55b, or the pair of magnets 52, 52, and the pair of tracking coils 5
The relative relationship between 5a and 55b and the focusing coil 56 is set as follows.

The configuration of each of the magnets 52 is the same, and the configuration of each of the tracking coils 55a and 55b is the same except for the winding direction of the coils. And the relative relationship between one of the magnets 52, one of the tracking coils 55a, and the focusing coil 56 will be described.

In the present invention, as shown in FIG.
When the b (lens holder 53) is at least displaced toward the upper side in FIG. 3 (one end in the optical axis direction of the objective lens 54), the electromagnetic force of the tracking coil 55a in the optical axis direction of the objective lens 54 On which is acting (side 551)
At least a portion of the magnet 52 is located above the long side 524 of the magnet 52 (one end of the magnet 52 in the optical axis direction of the objective lens 54) in FIG. 3 (outside the magnet 52 in the optical axis direction), as shown in FIG. , Movable part 5b (lens holder 5)
When 3) is at least displaced toward the lower side in FIG. 4 (the other end in the optical axis direction of the objective lens 54), the electromagnetic force of the tracking coil 55a in the optical axis direction of the objective lens 54 acts. At least a part of the portion (side 553) to be formed is located below (in the optical axis direction of the magnet 52 outside) the long side 525 of the magnet 52 (the other end of the magnet 52 in the optical axis direction of the objective lens 54). It is configured to be.

In other words, in other words, in the present invention, as shown in FIG. 3, the upper surface 550 of the tracking coil 55a in FIG. 4 in the direction (the optical axis direction end of the objective lens 54 of the magnet 52) and, as shown in FIG. 4, the lower side of the tracking coil 55a in FIG.
(a) Surface 559 of the other end of the objective lens 54 in the optical axis direction)
However, the movable portion 5b (the lens holder 53) is configured to be displaced in the same direction as the range exceeding the long side 525 of the magnet 52 (the other end of the magnet 52 in the optical axis direction of the objective lens 54).

In other words, in the present invention, as shown in FIG. 3, the movable portion 5b (lens holder 53) is at least upwardly in FIG. 3 (one end of the objective lens 54 in the optical axis direction). When the displacement is limited, and as shown in FIG.
When the movable portion 5b (lens holder 53) is displaced at the maximum toward at least the lower side in FIG. 4 (the other end of the objective lens 54 in the optical axis direction), the tracking coils 55
a and the absolute value of the electromagnetic force directed to the upper side in FIG. 3 and FIG. 4 (one end in the optical axis direction of the objective lens 54) and the tracking coil 55a, and to the lower side in FIG. 3 and FIG. The absolute value of the electromagnetic force toward the other end of the lens 54 in the optical axis direction) is different from the absolute value of the electromagnetic force.
The absolute value of the electromagnetic force acting on the side 551 of “a” is different from the absolute value of the electromagnetic force acting on the side 553 of the tracking coil 55a.

In other words, in the present invention, the movable part 5
b (lens holder 53) moves the objective lens 54 from the reference position.
3 and when displaced in a direction (X-axis direction) perpendicular to the optical axis 541 of the objective lens 54, and as shown in FIG.
3) is displaced at the maximum toward at least the upper side in FIG. 3 (one end side of the objective lens 54 in the optical axis direction), and FIG.
As shown in (5), when the movable portion 5b (lens holder 53) is displaced at the maximum toward at least the lower side in FIG. 4 (the other end of the objective lens 54 in the optical axis direction), the focusing coils 56 An electromagnetic force acts to incline the optical axis 541 of the objective lens 54 from the reference axis (Z axis) in a predetermined direction, and the optical axis 541 of the objective lens 54 moves from the reference axis (Z axis) to the tracking coil 55a. It is configured such that an electromagnetic force for inclining in a direction opposite to a predetermined direction acts.

Here, the "reference position" refers to the tracking coils 55a and 55b and the focusing coil 56.
Means the position of the movable part 5b (lens holder 53) when no current is flowing through each of them, that is, the position shown in FIG.

In the present invention, as shown in FIG. 5, when the movable part 5b (lens holder 53) is located at the reference position in the optical axis direction of the objective lens 54, the objective lens 54 of the tracking coil 55a Of the magnet 52 does not protrude in the optical axis direction from both ends of the magnet 52 in the optical axis direction, that is, the side 551 of the tracking coil 55a is longer than the long side 524 of the magnet 52. 5 does not protrude upward, and the side 553 of the tracking coil 55a is
It is preferable that it is configured not to protrude upward in FIG.

Here, the "reference position in the optical axis direction" refers to the position of the movable part 5b (lens holder 53) when no current flows through the focusing coil 56.

The same applies to the other magnet 52 and the other tracking coil 55b.

Such an optical pickup 1 is, for example,
This is achieved by setting the length L1 of each magnet 52 in the Z-axis direction to a predetermined value.

The length L1 of each magnet 52 in the Z-axis direction
Is preferably set to be equal to, slightly shorter than, or slightly longer than the length L2 of the tracking coils 55a, 55b in the Z-axis direction. Equal to L2, or
More preferably, it is set slightly longer than L2.

Next, the operation of the optical pickup 1 will be described. As shown in FIG. 5, the tracking coils 55a and 55b and the focusing coil 5 of the optical pickup 1
When no current flows through each of the movable parts 5b
The (objective lens 54) is located at the reference position shown in FIG.

When the tracking coils 55a and 55b are energized, an electromagnetic force acts on the tracking coils 55a and 55b, whereby the movable portion 5b moves in the X-axis direction, that is, in the radial direction of the loaded optical disk (tracking direction: radial). Direction).

When the focusing coil 56 is energized, an electromagnetic force acts on the focusing coil 56, whereby the movable portion 5b moves in the Z axis direction (reference axis direction), that is, in the optical axis direction of the objective lens 54 (optical axis direction). In the focusing direction).

Here, a case where the movable portion 5b is displaced to the upper right in FIG. 5 will be representatively described.

As shown in FIG. 6, the tracking coil 5
A current i1 (direction is indicated by an arrow in the drawing) flows through each of 5a and 55b, and a current i2 flows through the focusing coil 56.
When a direction (indicated by an arrow in the figure) flows, a predetermined electromagnetic force acts on each of the tracking coils 55a and 55b and the focusing coil 56, whereby the movable portion 5b is displaced to the upper right in FIG. Is held.

That is, as shown in FIG. 6, when a current i1 (direction is indicated by an arrow in the drawing) flows through the tracking coils 55a and 55b, respectively,
Electromagnetic forces F1, F3, and F4 (directions are indicated by arrows in the figure) act on the respective sides 551, 553, and 554 of 5a, and the respective sides 55 of the tracking coil 55b.
Electromagnetic forces F5, F6, F7 and F8 (directions are indicated by arrows in the figure) act on 5, 556, 557 and 558, respectively. Since no magnetic flux hits the side 552 of the tracking coil 55a, no electromagnetic force is generated.

In this case, the magnetic flux impinges on all sides 556 of the tracking coil 55b, while the side 558
, The magnetic flux is applied to only a part of the magnetic field, the absolute value of the electromagnetic force F6 acting on the side 556 and the absolute value of the electromagnetic force F8 acting on the side 558 are | F6 |> | F8 | The resultant force of the forces F6, F8 and F4 is a force directed to the right side in FIG.

As a result, the movable portion 5b is displaced to the right in FIG. 6, and the magnet 52 and the tracking coil 55 are displaced.
FIG. 6 shows the positional relationship between the a, 55b and the focusing coil 56 in the X-axis direction. The amount of displacement (movement) of the movable portion 5b to the right in FIG.

The current i is applied to the focusing coil 56.
When 2 flows (the direction is indicated by an arrow in the figure), an electromagnetic force F9 (the direction is indicated by an arrow in the figure) acts on the side 561 of the focusing coil 56 toward the upper side in FIG.

This electromagnetic force F9 is apparently the X of the magnet 52 on the side 561 of the focusing coil 56.
Focusing coil 5 which is intermediate in the axial direction and
Acts on the middle position (point) 6 in the optical axis direction of the objective lens on the side 561 of 6.

In this case, since the movable portion 5b is displaced L from the reference position (see FIG. 5) to the right in FIG.
6 does not coincide with the center of gravity G of the movable portion 5b.
It is spaced L to the middle left. For this reason, the electromagnetic force F9 is not apparently moved from the center of gravity G of the movable portion 5b but from the center of gravity G in FIG.
It acts on the position 6 separated by L on the middle left side.

Accordingly, the electromagnetic force F9 is divided into a force for displacing the movable portion 5b upward in FIG. 6 and a force F30 for rotating the movable portion 5b clockwise in FIG.

The movable portion 5b of the electromagnetic force F9 is
The movable portion 5b is displaced upward in FIG. 6 by the force displaced upward in the middle, and the magnet 52 and the tracking coil 5 are displaced upward.
The positional relationship between the focusing coils 5a and 55b and the focusing coil 56 in the Z-axis direction is as shown in FIG.

In this case, a part of the side 551 of the tracking coil 55a is separated from the long side 524 of the magnet 52 in FIG.
Since it is located on the upper middle side, the magnetic flux that strikes the side 551 is smaller (smaller) than the magnetic flux that strikes the side 553, and the absolute value of the electromagnetic force F1 acting on the side 551 and the absolute value of the electromagnetic force F3 acting on the side 553 The value is | F3 |> | F1 |, and the resultant force of these electromagnetic forces F1 and F3 is a force directed upward in FIG.

Similarly, the side 5 of the tracking coil 55b
6 is located above the long side 524 of the magnet 52 in FIG. 6, the magnetic flux hitting the side 555
The absolute value of the electromagnetic force F5 acting on the side 555 and the absolute value of the electromagnetic force F7 acting on the side 557 are | F7 |> | F5 | The resultant force of F7 is a force directed downward in FIG.

From the resultant force of the electromagnetic forces F1 and F3 and the resultant force of the electromagnetic forces F5 and F7, a force F20 for rotating the movable portion 5b counterclockwise in FIG.

Since the directions of the force F20 and the force F30 are opposite to each other, they are canceled or the force F20 is canceled.
As a result, the force F30 decreases.

Therefore, whether the optical axis 541 of the objective lens 54 is parallel to the reference axis (Z axis) on the XZ plane,
Alternatively, the reference axis (Z axis) of the optical axis 541 of the objective lens 54
Can be made relatively small.

Here, the larger the amount of displacement of the movable portion 5b toward the upper side in FIG. 6, the larger the side 561 of the focusing coil 56.
Although the absolute value of the electromagnetic force F9 acting on the tracking coil 55a is large and the absolute value of the force F30 is large, the larger the amount of displacement of the movable portion 5b in FIG. 6 from the long side 524 of FIG.
Many parts are located on the upper middle side, and the absolute value of the force F20 is large. That is, the force F20 increases or decreases in accordance with the increase or decrease in the force F30.

As a result, even when the movable portion 5b is located at an arbitrary position in the Z-axis direction,
The optical axis 541 of the objective lens 54 and the reference axis (Z axis) may be parallel or the inclination angle (tilt angle) of the optical axis 541 of the objective lens 54 with respect to the reference axis (Z axis) may be relatively small. it can.

Hereinafter, although the description is omitted, similar to the above,
Even when the movable portion 5b is displaced from the reference position (see FIG. 5) to the lower right, upper left, and lower left in FIG. 6, the optical axis 541 of the objective lens 54 and the reference axis (Z
) Can be parallel to each other, or the inclination angle (tilt angle) of the optical axis 541 of the objective lens 54 with respect to the reference axis (Z axis) can be made relatively small.

At the time of recording (writing data) or reproducing (reading data), a laser beam is emitted from the laser diode of the optical pickup 1. This laser beam
The light is condensed by the objective lens 54 so as to have a predetermined beam diameter, and is irradiated on a rotating optical disk.

The reflected light from the optical disk is
The light is condensed by the objective lens 54, received by the photodiode, and photoelectrically converted. The signal from the photodiode is input to a predetermined circuit and processed.

As described above, according to the optical pickup 1, the movable portion 5b (objective lens 54) is moved in the radial direction (tracking direction) of the optical disk and the objective lens 5
4, the optical axis 541 of the objective lens 54 when displaced (moved) in the optical axis direction (focusing direction) is the reference axis (Z axis).
Can be suppressed (or prevented) from inclining,
Thus, the objective lens 54 can maintain an appropriate posture. That is, when the objective lens 54 is displaced in the radial direction of the optical disk and in the direction of its optical axis, it is possible to prevent deterioration of characteristics of the optical pickup (for example, recording / reproducing characteristics).

Thus, recording and reproduction can be reliably performed on the optical disk, and particularly, recording and reproduction can be reliably performed on the optical disk of high density recording such as DVD (digital video disk). Can be.

Although the optical pickup of the present invention has been described based on the illustrated embodiment, the present invention is not limited to this, and each component may have any configuration having the same function. Can be replaced by

For example, in the present invention, a magnet (permanent magnet) may be provided on only one of the pair of opposed side walls of the yoke.

[0092]

As described above, according to the optical pickup of the present invention, the light of the objective lens when the lens holder (objective lens) is displaced (moved) in the radial direction of the optical disk and in the optical axis direction of the objective lens. Can prevent (or prevent) the axis from tilting from the reference axis,
The objective lens can maintain a proper posture.

Thus, recording and reproduction can be reliably performed on the optical disk, and particularly, recording and reproduction can be surely performed on the high density recording optical disk such as a DVD (digital video disk). Can be.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of an optical pickup of the present invention.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is a front view schematically showing a magnet, a tracking coil, and a focusing coil of the optical pickup shown in FIG.

FIG. 4 is a front view schematically showing a magnet, a tracking coil, and a focusing coil of the optical pickup shown in FIG. 1;

FIG. 5 is a front view schematically showing a magnet, a tracking coil, and a focusing coil of the optical pickup shown in FIG. 1;

FIG. 6 is a front view schematically showing a magnet, a tracking coil, and a focusing coil of the optical pickup shown in FIG. 1;

FIG. 7 is a front view schematically showing a magnet, a tracking coil, and a focusing coil of a conventional optical pickup.

FIG. 8 is a front view schematically showing a magnet, a tracking coil, and a focusing coil of a conventional optical pickup.

FIG. 9 is a front view schematically showing a magnet, a tracking coil, and a focusing coil of a conventional optical pickup.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical pickup 4 Damper base 5 Actuator 5a Fixed part 5b Movable part 51 Yoke 511 Bottom surface 512, 513 Side wall 52 Magnet 521 Surface 522, 523 Short side 524, 525 Long side 53 Lens holder 531 Lens support part 54 Objective lens 541 Optical axis 55a , 55b Tracking coil 550, 555 surface 551-558 side 56 Focusing coil 561 side 6 position 7 Suspension wire 100 Optical pickup 110 Magnet 120a, 120b Tracking coil 121-128 side 130 Focusing coil 140 Optical axis 150 Reference axis 160 Position G center of gravity

Claims (5)

[Claims] 1. A tracking coil, a focusing coil, an objective lens, a lens holder for supporting the tracking coil, the focusing coil and the objective lens, and a displaceably supported lens holder via a plurality of suspension wires. Pickup having a damper base, a yoke, and a magnet mounted on the yoke, wherein the lens holder is at least displaced at least toward one end in the optical axis direction of the objective lens. At least a part of the tracking coil, on which the electromagnetic force in the optical axis direction of the objective lens acts, is located outside the magnet in the optical axis direction from one end of the magnet in the optical axis direction of the objective lens. And the lens holder is at least on the other end side in the optical axis direction of the objective lens. When the maximum displacement occurs in the tracking coil, at least a part of the portion of the tracking coil on which the electromagnetic force in the optical axis direction of the objective lens acts is more than the other end of the magnet in the optical axis direction of the objective lens. An optical pickup characterized by being configured to be located outside the magnet in the optical axis direction. 2. A tracking coil, a focusing coil, an objective lens, a lens holder that supports the tracking coil, the focusing coil and the objective lens, and a displaceable support of the lens holder via a plurality of suspension wires. An optical pickup having a damper base, a yoke, and a magnet mounted on the yoke, wherein the surface of the tracking coil on one end side in the optical axis direction of the objective lens has the magnet in the same direction. And the other surface of the tracking coil on the other end side in the optical axis direction of the objective lens is in the same direction as the other end of the magnet coil in the optical axis direction of the objective lens. Light, characterized in that the lens holder is configured to be displaced in a range beyond the end. Kkuappu. 3. A tracking coil, a focusing coil, an objective lens, a lens holder that supports the tracking coil, the focusing coil and the objective lens, and a displaceable support of the lens holder via a plurality of suspension wires. An optical pickup having a damper base, a yoke, and a magnet mounted on the yoke, wherein the lens holder is at least displaced at least toward one end in the optical axis direction of the objective lens; and When the displacement is maximized toward the other end, the absolute value of the electromagnetic force acting on the tracking coil toward one end in the optical axis direction of the objective lens and the absolute value of the electromagnetic force toward the other end are calculated. An optical pickup characterized by having different configurations. 4. A tracking coil, a focusing coil, an objective lens, a lens holder for supporting the tracking coil, the focusing coil and the objective lens, and a displaceably supporting the lens holder via a plurality of suspension wires. An optical pickup having a damper base, a yoke, and a magnet installed on the yoke, wherein the lens holder is positioned from a reference position with respect to an optical axis direction of the objective lens and an optical axis of the objective lens. When the lens holder is displaced in the vertical direction and the lens holder is displaced at a maximum toward at least one end of the objective lens in the optical axis direction and when the lens holder is displaced at a maximum toward the other end, the focusing is performed. The coil attempts to tilt the optical axis of the objective lens in a predetermined direction from a reference axis. An optical pickup, wherein a magnetic force acts on the tracking coil, and an electromagnetic force acts to tilt the optical axis of the objective lens from a reference axis in a direction opposite to the predetermined direction. . 5. When the lens holder is located at a reference position in the optical axis direction of the objective lens, a portion of the tracking coil where the electromagnetic force in the optical axis direction of the objective lens acts is a part of the magnet. The optical pickup according to claim 1, wherein the optical pickup is configured not to protrude in the optical axis direction from both ends of the objective lens in the optical axis direction.