JP2939137B2 - Objective lens drive - Google Patents

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.

[0002]

2. Description of the Related Art Conventionally, as an optical recording / reproducing apparatus, for example, in an optical disk apparatus using an optical disk as a recording medium, an optical pickup is used to write and read information signals to and from the disk. . In this optical pickup, an objective lens driving device for accurately focusing a laser beam on information pits of a disk is used. Various types of this objective lens driving device are known.
FIG. 4 shows one disclosed in Japanese Patent Publication No. 34-34.

In FIG. 1, reference numeral 1 denotes a lens holder. The lens holder 1 is supported so as to be rotatable around a fixed shaft 7 and movable along the shaft 7. An objective lens 2 is attached to the lens holder 1 with its optical axis parallel to the axis 7. The lens holder 1 also has
A balancer 8 is fixed to the opposite side of the objective lens 2 about the axis 7. A pair of focusing driving coils 4 and tracking driving coils 3 are fixed to the outer peripheral surface of the lens holder 1 at symmetrical positions with respect to the shaft 7.

The shaft 7 is fixed to the bottom of an outer yoke 9 as a fixing member. The outer yoke 9 is formed in a fan shape on both sides with the shaft 7 interposed therebetween, and the outer peripheral edge of the fan shape is bent at a right angle and rises so as to face the coils 3 and 4. An arc-shaped magnet 6 is fixed to the inner surface of the rising portion of the outer yoke 9. As shown in FIG. 5, the magnet 6 has a groove 6c formed in a middle portion in a direction parallel to the shaft 7 (focusing direction). The focusing magnet 6a and the tracking magnet 6a are separated from the groove 6c. It is divided into a magnet part 6b. The focusing magnet portion 6a is polarized and magnetized so that the N and S poles are aligned in the direction of the axis 7 (the upper pole in the figure is the S pole and the lower pole is the N pole), while the tracking magnet portion 6b is the same as that of the focusing magnet portion 6a. The N and S poles are formed in the circumferential direction by being polarized and magnetized in a direction (tracking direction) perpendicular to the magnetization direction (N pole on the focusing drive coil 6a side, S pole on the other side). .

Since the magnets 6 are arranged in pairs at symmetrical positions with respect to the shaft 7, when the magnets 6 are deployed in the tracking direction, they become as shown in FIG. That is, the polarization magnetization of one focusing magnet (for example, the one on the left side in the figure) is the same as that of the other focusing magnet (for example, the one on the right side in the figure) in the focusing direction (the upper side in the figure). S
The pole and the lower side are the N pole), and the polarization magnetization polarity of one tracking magnet (for example, the one on the left side in the figure) is the same as that of the other tracking magnet (for example, the right side in the figure) in the tracking direction. (The north pole is shown on the left side and the south pole is shown on the right side).

As shown in FIG. 6, the focusing drive coil 4 is formed in a horizontally long rectangular shape, and is disposed such that its long side faces each magnetic pole of the focusing magnet portion 6a. . Further, the tracking drive coil 3 is formed to be a vertically long rectangle, and is disposed such that its long side faces each magnetic pole of the tracking magnet section 6b.

As shown in FIG. 4, an inner yoke 5 is provided on the bottom surface of the outer yoke 9 so as to project from the paper surface toward this side. Like the outer yoke 9, the inner yoke 5 is formed in a fan shape on both sides of the shaft 7, and the outer peripheral edge of the fan shape is bent at a right angle and rises. The rising portion is opposed to the magnets 6a and 6b with the coils 3 and 4 interposed therebetween. As described above, the inner yoke 5, the driving coils 3, 4, the magnet 6, and the outer yoke 9 are respectively arranged along an arc centered on the shaft 7, and a substantially closed magnetic path passing therethrough is formed in this order from the inside. Have been.

When a drive power is supplied to the focusing drive coil 4, a thrust is generated by the drive current and the magnetic flux in the magnetic circuit, and the objective lens 2 moves in the direction of the optical axis together with the lens holder 1. When a focusing operation is performed and a drive current is supplied to the tracking drive coil 3, a thrust is generated by the drive current and the magnetic flux in the magnetic circuit, and the objective lens 2 moves in the tracking direction together with the lens holder 1. A tracking operation is performed.

As shown in FIGS. 4 and 6, the outer peripheral edge of the sector of the lens holder 1 is located at a position facing the center (central portion) of the magnetic pole of the focusing magnet portion 6a in the direction of the shaft 7. A long magnetic piece 10 is fixed to the objective lens 2 by generating a two-dimensional restoring force in a focusing direction and a tracking direction by a magnetic attraction force of a focusing magnet 6a acting on the magnetic piece 10. Can be held at a neutral point (stationary neutral position) when not driven.

[0010]

Here, when a driving current is applied to the focusing drive coil 4 to perform focusing control, the focusing drive coil 4
A magnetic flux is generated in a direction perpendicular to the plane of the paper in FIG. 6, and can be driven in the focusing direction. However,
The same magnetic flux is affected by the tracking magnets 6b facing diagonally and laterally, and a thrust (attraction or repulsion) in the tracking direction is generated for the focusing drive coil 4. Here, the polarization magnetizing polarity of the tracking magnet 6b is the same in the tracking direction for both the tracking magnets 6b, 6b as described above (see FIG. 7), so that the thrust is the same direction in the tracking direction. Therefore, there is a problem that the so-called crosstalk occurs and the servo becomes unstable.

The magnetic piece 10 is in a magnetic circuit formed by the focusing magnet 6a and the inner yoke 5, and has a polarity opposite to that of the focusing magnet 6a. Accordingly, when the lens is moved in the focusing direction, it is affected by the tracking magnet 6b facing diagonally and horizontally, so that during focusing control, a thrust is applied in the same tracking direction as described above, and the servo becomes more unstable. Would.

Therefore, the present invention cancels out (neutralizes) the magnetic influence of the tracking magnet on the tracking direction during the focusing control and eliminates the thrust in the tracking direction, thereby stabilizing the servo and improving the reliability. An object of the present invention is to provide an objective lens driving device.

[0013]

According to a first aspect of the present invention, in order to achieve the above object, an objective lens driving device is polarized and magnetized in a focusing direction on one of a lens holder holding an objective lens and a fixing member. A focusing magnet and a tracking magnet that is arranged in parallel with the focusing magnet in the tracking direction and polarized and magnetized in the tracking direction, and on the other hand, a focusing drive coil and a tracking drive coil,
With arranging a pair at a time, respectively, by respectively opposite the drive coil and a magnet between the driving coil and the magnet with each other and tracking for the focusing, the for each <br/> drive coil, it faces the said drive coil the magnet
In the objective lens driving device configured to drive the lens holder in the focusing direction and the tracking direction by applying currents in the directions corresponding to the magnetization polarities of the pair of focusing magnets, respectively.
The polarization adhesion pole of Judges, the Ru varied in該分pole direction
In both cases, a pair of focuses with different polarization magnetization polarities
Focusing drive facing each of the magnets
Check that the direction of energization of the moving coil is
It is characterized in that it is made different in accordance with the polarization magnetization polarity of the unit.

In order to achieve the above-mentioned object, the objective lens driving device of the second means includes, in addition to the first means, a magnetic circuit including a focusing magnet, and the objective lens is driven to a neutral point by magnetic attraction. Magnetic piece to hold the
It is characterized in that it is provided to face the focusing magnet.

[0015]

According to the objective lens driving device of the first means, if one of the pair of focusing magnets or the pair of tracking magnets has different polarization magnetization polarity in the polarization direction, At the time of the focusing control, the thrust in the tracking direction generated on one of the focusing driving coils due to the magnetic influence of one of the tracking magnets and the magnetic force of the other tracking magnet due to the magnetic influence of the other tracking magnet. The thrust in the tracking direction generated for the focusing drive coil is directed in the opposite direction, and the thrust in the tracking direction during the focusing control is canceled.

According to the objective lens driving device of the second means, in addition to the function of the first means, the polarization magnetization polarity of either one of the pair of focusing magnets or the pair of tracking magnets is changed. ,
If different in the polarization direction, during focusing control, due to the magnetic effect of one of the tracking magnets, the thrust in the tracking direction generated on one of the adjacent magnetic pieces, and the magnetic effect of the other tracking magnet, The thrust in the tracking direction generated for the other magnetic piece that is close to the other will be in the opposite direction,
The thrust in the tracking direction during the focusing control is offset.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a magnet used in an objective lens driving device according to an embodiment of the present invention, and FIG. 2 is a diagram in which the magnet shown in FIG. 1 and the magnet shown in FIG. 5 are applied to the objective lens driving device shown in FIG. FIG. 5 is a diagram showing an inner peripheral surface of the magnet in a case where the inner peripheral surface is developed in a circumferential direction.

In the objective lens driving device of this embodiment, a magnet 16 as shown in FIG. 1 is fixed to the inner surface of one rising portion of the outer yoke 9. As shown in the drawing, the magnet 16 has a groove 16c formed in a direction parallel to the axis 7 (focusing direction) at an intermediate portion. The focusing magnet 16a and the tracking magnet 16a are separated from the groove 16c. Magnet part 1
6b. The focusing magnet portion 16a is polarized and magnetized so that the N and S poles are arranged in the direction of the axis 7 and the upper side in the drawing is the N pole and the lower side is the S pole.
On the other hand, the tracking magnet portion 16b is arranged such that the N and S poles are arranged in a direction (tracking direction) perpendicular to the magnetizing direction of the focusing magnet portion 16a, and the left side in the drawing is the N pole and the right side is the S pole. Polarized and magnetized.

A magnet 6 similar to that described with reference to FIG. 5 of the prior art is provided on the inner surface of one of the rising portions of the outer yoke 9 which is located symmetrically with respect to the axis 7 of the other rising portion.
Has been fixed. Note that other configurations are the same as those described in the related art, and thus description thereof is omitted here to avoid duplication.

Therefore, when the inner peripheral surfaces of the magnets 6 and 16 are developed along the circumferential direction, they are as shown in FIG.

That is, the tracking magnet 6
The polarization magnetization polarities of b and 16b are the same in the polarization direction (tracking direction), but the polarization magnetization polarities of the focusing magnets 6a and 16a are different in the polarization direction (focusing direction). .
Further, in FIG. 2 (the same applies to FIG. 3 hereinafter), since the polarization magnetized polarities of the focusing magnets are different from those of the focusing magnets 16a and 6a, the focusing drive coils 4 and 4 facing the focusing magnets 16a and 6a are different from each other. The direction of the current is also different, so that the polarity of the magnetic flux formed by the focusing drive coil is different.

Here, at the time of the focusing control, as described in the related art, due to the magnetic influence of the one tracking magnet 16b, the one focusing driving coil 4 (obliquely opposed to the side) is disposed. Although a thrust in the tracking direction is generated, if one thrust in the tracking direction is generated, for example, in the right direction in FIG. 1 (clockwise direction in FIG. 4), the magnetic force of the other tracking magnet 6b causes The other thrust in the tracking direction that is generated with respect to the other focusing driving coil 4 that is provided nearby is generated in the left direction in FIG. 1 (counterclockwise direction in FIG. 4). That is, one of the tracking magnets 16b
And the other thrust generated by the magnetic effect of the other tracking magnet 6b face in the opposite direction in the tracking direction.

As described above, in the present embodiment, during focusing control, the thrust in the tracking direction generated on the focusing drive coil due to the influence of the tracking magnet can be canceled (neutralized). As a result, the servo is stabilized and reliability can be improved.

Further, as described in the prior art, the magnetic piece 10 is also provided with one of the tracking magnets 16.
due to the magnetic influence of b
A thrust in the tracking direction is generated on one of the magnetic pieces 10, and a thrust is generated in the tracking direction on the other magnetic piece 10 located close by the magnetic influence of the other tracking magnet 6 b. In the same manner as described above, since the tracking direction is opposite to the tracking direction, the thrust in the tracking direction generated on the magnetic piece due to the influence of the tracking magnet can be canceled (neutralized) during the focusing control. Therefore, the servo is stabilized and the reliability can be improved.

That is, in this embodiment, during the focusing control, the thrust in the tracking direction generated on the focusing drive coil and the magnetic piece due to the influence of the tracking magnet can be canceled (neutralized). As a result, the servo is stabilized and reliability can be improved.

FIG . 3 shows another embodiment .
The polarization magnetization polarities of the racking magnets are matched in the polarization direction (tracking direction), and the polarization magnetization polarities of the focusing magnets are opposite to each other in the polarization direction (focusing direction).
This shows an example in which the directions are different.

Even with this configuration, the thrust in the tracking direction generated on the focusing drive coil and the magnetic piece due to the influence of the tracking magnet can be canceled (neutralized) during the focusing control. It goes without saying because it is possible to obtain the same effect as in the embodiments.

Although the invention made by the inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the invention. Needless to say, for example, in the above embodiment, the drive coils 3 and 4 are mounted on the lens holder 1 and the magnets 6 are mounted on the outer yoke 9 as a fixing member in order to reduce the weight of the lens holder as a movable part. , 16 are fixed, but the magnets 6, 16 may be fixed to the lens holder 1, and the drive coils 3, 4 may be fixed to the outer yoke 9, respectively.

Further, in the above embodiment, an example of application to an objective lens driving device having a magnetic piece 10 for holding the objective lens 2 at a neutral point when not driven is described. Needless to say, the present invention can be similarly applied to an objective lens driving device having no configuration.

[0030]

As described above, the objective lens driving device according to the first aspect of the present invention makes the polarization magnetized polarities of a pair of focusing magnets different in the polarization direction, and performs one of the two at the time of focusing control. Thrust in the tracking direction generated by one of the focusing drive coils due to the magnetic influence of the tracking magnet,
Due to the magnetic effect of the other tracking magnet,
Since the thrust in the tracking direction generated with respect to the other focusing drive coil that is located nearby is directed in the opposite direction, and the thrust in the tracking direction at the time of focusing control is configured to cancel, the servo is stabilized, Reliability can be improved.

Further, the objective lens driving device according to the second aspect of the present invention
In addition to the first aspect, in a magnetic circuit including a focusing magnet, a magnetic piece for holding the objective lens at a neutral point by magnetic attraction is provided to face the focusing magnet, and a magnetic piece is provided at the time of focusing control. Due to the magnetic effect of one tracking magnet, the thrust in the tracking direction generated on one of the adjacent magnetic pieces and the magnetic effect of the other tracking magnet on the other adjacent magnetic piece. Since the generated thrust in the tracking direction is directed in the opposite direction to offset the thrust in the tracking direction during the focusing control, the servo is stabilized and reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view of a magnet used in an objective lens driving device according to an embodiment of the present invention.

FIG. 2 is a diagram in which the inner peripheral surface of the magnet shown in FIG. 1 and the magnet shown in FIG. 5 are developed along the circumferential direction when the magnet is applied to the objective lens driving device shown in FIG. is there.

FIG. 3 is a diagram showing an inner peripheral surface of the magnet when the magnet is applied to the objective lens driving device shown in FIG. 4 in an expanded manner along a circumferential direction.

FIG. 4 is a plan view of an objective lens driving device showing an example of the prior art.

FIG. 5 is a perspective view of the magnet in FIG. 4;

FIG. 6 is a front view of a coil and a magnetic piece in FIG. 4;

FIG. 7 is a diagram showing an inner peripheral surface of the magnet in FIG. 4 developed in a circumferential direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lens holder 2 Objective lens 3 Tracking drive coil 4 Focusing drive coil 6a, 16a Focusing magnet 6b, 16b Tracking magnet 9 Fixing member 10 Magnetic piece N, S Polarization polarity

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A 1-312743 (JP, A) JP-A 1-317234 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 7/09-7/095

Claims (2)

(57) [Claims] 1. A focusing magnet polarized in a focusing direction on one of a lens holder holding an objective lens and a fixed member, and a focusing magnet arranged in parallel with the focusing direction in the tracking direction. A pair of a tracking driving coil and a pair of tracking driving coils are arranged on the other side, and a pair of the focusing driving coil and the tracking driving coil are arranged on the other side. It was opposed respectively, for the respective drive coils, facing the said drive coil Ma
An objective lens driving device configured to drive the lens holder in a focusing direction and a tracking direction by passing currents in directions corresponding to the magnetization polarities of the gnets, respectively. the polarization adhesive magnetic polarity, Rutotomoni varied in該分pole direction, they polarizable adhesion pole different pair of Ma for focusing
Focusing drive coil facing each of the gnets
The direction of current flow to the focusing magnet
An objective lens driving device characterized in that the objective lens driving device is made different in accordance with the polar magnetization polarity . 2. The objective lens driving device according to claim 1, wherein a magnetic piece for holding the objective lens at a neutral point by magnetic attraction is provided in the magnetic circuit including the focusing magnet. An objective lens driving device provided to face a magnet.