JP2000011410A - Object lens actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a moving magnet type object lens actuator having a high driving sensitivity. SOLUTION: This actuator 70 for driving an object lens is provided with a supporting body 51 supporting the object lens 50 and a supporting mechanism 58 movably supporting the supporting body 51. Magnets 56a-56b are mounted on the supporting body 51. Moreover, a couple of magnetic materials 60a, 60b are arranged so as to be opposed to the magnets while being spaced from the magnets 56a-56d, and magnetic gap areas M1, M2 are formed including the magnets. And, driving coils 61a-61d, 63a, 63b, and 64a-64d are arranged, of which some are located within the magnetic gap areas, and the others are located projectingly from the magnetic gap areas in the direction opposite to the disk.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens actuator in an optical device for recording an information signal on an optical disk or the like as an optical information recording medium or reproducing the recorded information signal. The present invention relates to an objective lens actuator having high actuator drive sensitivity.

[0002]

2. Description of the Related Art In an optical device such as an optical disk device for recording an information signal on an optical disk or reproducing the recorded information signal by irradiating a signal recording surface of a rotating optical disk with a light beam, the information signal is recorded on the optical disk. An optical head is used as a means for recording (writing) and reproducing (reading).

This optical head comprises a light source such as a semiconductor laser element, an optical element such as a collimator lens and a beam splitter, an objective lens, a photodetector and the like, and converts a light beam emitted from the light source into a collimator lens or a beam. The light is guided to an objective lens via an optical element such as a splitter, is focused on the recording surface of an optical disk by the objective lens, and a light beam reflected by the recording surface is detected by a photodetector to record and reproduce information signals. Is configured to do so.

Here, the objective lens is generally driven by an objective lens actuator to be displaced and driven by an electromagnetic driving force in two axial directions of an optical axis direction (focusing direction) and a direction orthogonal to the optical axis direction (tracking direction). It has become. As a result, the light beam is focused on the recording surface of the optical disk, and the recording track can be accurately scanned. The movable range of a general objective lens by an objective lens actuator that drives only the objective lens is either an optical head with an integrated optical system or an optical head with a separated optical system in which only the optical system is separated and fixed. ± 0.6mm in focusing direction, ± 0.4 in tracking direction
mm.

[0005] Japanese Patent Application Laid-Open No. 4-57226 discloses that
A moving magnet type actuator that drives the entire optical head integrated with an optical system is disclosed.

Here, the moving magnet type actuator is an actuator having a configuration in which a magnet is arranged on a movable portion side on which an objective lens and the like are mounted, and a drive coil is arranged on a fixed portion side. Conversely, a moving coil type actuator is an actuator having a configuration in which a drive coil is arranged on a movable unit side on which an objective lens or the like is mounted, and a magnet is arranged on a fixed unit side.

In the case of the conventional moving magnet type actuator described in the above publication, the movable range is ± 0.6 mm in the focusing direction and ± 0.6 mm in the tracking direction.
About 0.4 mm is required.

A conventional moving magnet type actuator will be described with reference to FIGS.
FIG. 15A is a front view of a conventional moving magnet type actuator, FIG. 15B is a sectional view taken along line AA of FIG. 15A, and FIG. 16 is an exploded perspective view.

As shown in FIGS. 15A, 15B and 16, the lens holder 2 mounts the objective lens 1 on the disk 11.
It is held to face. The lens holder 2 is movably supported by metal wires 4a to 4d on a fixing member 8 on a base 9.

[0010] Magnets 3a and 3b are attached to the lens holder 2 on both sides with the objective lens 1 interposed therebetween.
Magnetic yokes 5a and 5b are provided so as to face the magnets 3a and 3b at a distance from the magnets 3a and 3b. The magnetic yokes 5a, 5b are mounted on a base 9. Thus, the magnetic yokes 5a and 5b form a so-called open type magnetic circuit (see FIG. 19) together with the magnets 3a and 3b, and form a magnetic gap region. The magnetic yoke 5
a and 5b are provided with tracking coils 6a and 6b and focusing coils 7a and 7b, as shown in FIG.
Each is wound.

As shown in FIG. 15B, the optical unit 10 is provided below the objective lens 1, and forms a semiconductor laser as a light source and a light emitted from the semiconductor laser through a mirror 12. And a half mirror, and a photodetector for detecting a focus error signal, a tracking error signal, and an information signal on a recording medium. At the time of recording and reproduction, the emitted light from the semiconductor laser incorporated in the optical unit 10 is shaped, enters the objective lens 1 by the mirror 12, is reflected by the disk 11, and then is detected again in the optical unit 10. And a focus error signal, a tracking error signal, and an information signal are detected.

The optical unit 10, together with the objective lens 1, the lens holder 2, the magnets 3b, 3b and the mirror 12, is a so-called movable part.

Next, with respect to the conventional moving magnet type actuator as described above, the objective lens 1 is moved in the focus direction in order to correct a focus shift due to the warp or vertical movement of the disk 11 and a tracking shift due to eccentricity or the like. F, an operation of driving in two axes in the tracking direction T will be described.

Lens holder 2 with objective lens 1 attached
Is supported by the fixing member 8 by the four metal wires 4a to 4d arranged in parallel to each other as described above. The driving in the focus direction F is performed by magnets 3a and 3b mounted on the lens holder 2, magnetic yokes 5a and 5b mounted on the base 9, and a focusing coil 7a wound on the magnetic yokes 5a and 5b. , 7b are obtained by the translational movement of the lens holder 2 holding the objective lens 1 via the metal wires 4a to 4d.

On the other hand, driving in the tracking direction T is performed by winding around magnets 3a and 3b mounted on the lens holder 2, magnetic yokes 5a and 5b mounted on the base 9, and magnetic yokes 5a and 5b. Focusing coils 6a, 6
b is obtained by the translational movement of the lens holder 2 holding the objective lens 1 via the metal wires 4a to 4d by the electrokinetic converter made of b.

The entire actuator is accessed and driven by a motor in an access direction Ac (the same direction as the tracking direction T) on the optical disk.

[0017]

However, in the structure of the conventional moving magnet type actuator as described above, in accordance with the surface deflection acceleration and eccentric acceleration of the disk,
There is a problem that it is difficult to obtain the actuator drive sensitivity of the movable part including the objective lens and the like. Here, the actuator drive sensitivity means the acceleration of the movable unit per unit current flowing through the drive coil.

In recent years, optical disk devices have been increasing in speed (higher transfer rate), becoming more portable, more personalized, and more mobile, and the actuators used therein have been further downsized (especially thinner). And higher speeds are required. However, if the number of rotations of the disk is increased or the actuator is made thinner, it becomes more difficult to obtain the required drive sensitivity.

On the other hand, it has been generally said that it is generally difficult to increase the driving sensitivity of a moving magnet type actuator compared to a moving coil type actuator. Therefore, most of the actuators of the optical disk device are of the moving coil type.

However, in order to further increase the speed of the optical disk device, it is necessary to further increase the control band, and for that purpose, it is necessary to increase the secondary resonance frequency of the actuator movable section. However, it is difficult for the moving coil type actuator to increase the secondary resonance frequency of the actuator movable section. Therefore, attention has been paid to adopting a configuration of a moving magnet type actuator, that is, a high driving sensitivity of a moving magnet type actuator, which has been said to be difficult to increase in driving sensitivity, has been expected.

In addition, a moving coil type actuator requires a plurality of lead wires for supplying a drive current to a drive coil disposed in a movable portion, but a moving magnet type actuator does not require such a lead wire. There is. The lead wire of the moving coil type actuator has contributed to the side resonance that adversely affects the vibration characteristics of the moving coil type actuator.

In general, a moving magnet type actuator is easier to reduce the thickness than a moving coil type actuator, and it is easy to obtain good frequency characteristics over a wide band.

Further, in the moving coil type actuator, the temperature of the movable portion rises due to the heat generated by the drive coil disposed in the movable portion, and the positional relationship between the optical unit and the objective lens is destroyed by the thermal distortion of the lens holder, so that the optical stability is improved. However, this problem can be avoided by the moving magnet type actuator.

In the process leading to the present invention, the present inventor examined in detail why the conventional moving magnet type actuator could not realize high drive sensitivity. The details of the study will be described below with reference to FIGS.

FIG. 17 is a schematic view of the magnetic circuit near the focusing coil 7a of the conventional moving magnet type actuator viewed from the focusing direction.

The magnet 3a is mounted on the lens holder so that the N pole faces the magnetic yoke 5a.

The magnetic flux 31 exits from the N pole of the magnet 3a and returns to the S pole of the magnet 3a itself via the magnetic yoke 5a. Here, the directions of the current flowing through the focusing coil 7a are indicated by arrows 32, 33, 34, and 35.

When a Lorentz force is generated in the current portion of the focusing coil 7a indicated by the arrow 32, the actuator movable portion is driven in the focusing direction by the reaction force.

However, when the Lorentz force is generated in the current portion indicated by the arrow 32, the Lorentz force is also generated in the current portion of the focusing coil 7a indicated by the arrows 33, 34, and 35, and the latter Lorentz force is The direction is opposite to the Lorentz force generated in the current portion indicated by the arrow 32. That is, the focus driving force generated in the effective length portion (32) of the focus drive coil indicated by the arrow 32 is changed to the portions (33, 34, 3) other than the focus drive coil effective length.
5) has been reduced. For this,
With the conventional moving magnet type actuator configuration, high drive sensitivity cannot be realized.

The tracking driving force can be similarly explained. FIG. 18 shows a tracking coil 6a of a conventional moving magnet type actuator.
It is the schematic which looked at the magnetic circuit of the vicinity from the tracking direction.

The magnetic flux 41 exits from the north pole of the magnet 3a and returns to the south pole of the magnet 3a itself via the magnetic yoke 5a. Here, the directions of the current flowing through the tracking coil 6a are indicated by arrows 42, 43, 44, and 45.

The tracking coil 6a indicated by the arrow 42
When the Lorentz force is generated in the current portion, the actuator movable portion is driven in the tracking direction by the reaction force.

However, when the Lorentz force is generated in the current portion indicated by the arrow 42, the Lorentz force is also generated in the current portion of the tracking coil 6a indicated by the arrows 43, 44, and 45. The direction is opposite to the Lorentz force generated in the current portion indicated by the arrow 42. That is, the focus driving force generated in the effective length portion (42) as the tracking drive coil indicated by the arrow 42 is
Parts other than the effective length of the tracking drive coil (43, 4
4, 45) has been reduced. SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and has an objective lens driving actuator compatible with recent high speed (high transfer rate), portable, personalized, and mobile optical disk devices. It is an object of the present invention to provide a moving magnet type objective lens actuator having high drive sensitivity in order to realize a reduction in size, thickness, and speed of the camera.

[0034]

SUMMARY OF THE INVENTION The present invention provides a holder for holding an objective lens, a support mechanism for movably supporting the holder, a magnet provided on the holder, and a magnet spaced from the magnet. Is provided so as to face the
A magnetic material forming a magnetic gap region together with a magnet, and a drive coil partially disposed in the magnetic gap region and the other portion protruding from the magnetic gap region in a direction opposite to the disk. This is an actuator for driving an objective lens.

According to the present invention, since the other portion of the drive coil (the drive coil portion other than the effective length of the drive coil) is disposed so as to protrude from the magnetic gap region in the direction opposite to the disk, it is disposed in the magnetic gap region. The driving force due to the Lorentz force generated in the part (the driving coil effective length part) that was generated is used in
Is extremely reduced, and high driving sensitivity of the moving magnet type objective lens driving actuator can be realized.

According to the present invention, there is provided a holding member for holding an objective lens, a supporting mechanism for movably supporting the holding member, and at least one of the holding members provided on one side with opposite poles facing outward. A set of magnets, a magnetic body that is provided to face the set of magnets at a distance from the set of magnets, forms a closed magnetic circuit with the set of magnets, and forms a magnetic gap region; And a drive coil at least partially disposed in the gap region.

According to the present invention, a magnetic circuit in which a magnetic body and a set of magnets are closed forms a magnetic circuit, so that a high driving sensitivity of a moving magnet type objective lens driving actuator can be realized.

[0038]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 is a perspective view showing a configuration of a moving magnet type objective lens actuator according to the present invention, FIG. 2 is a plan view thereof, FIG. 3 is a side view thereof, and FIG. 4 is a front view thereof.

The objective lens actuator 70 of the present embodiment includes a lens holder 51 for holding the objective lens 50.
This is a device for driving the (holding body) in four axial directions of a focusing direction 52, a tracking direction 53, a radial tilt direction 54 (disc radial tilt), and a tangential tilt direction 55 (disc tangential tilt).

The objective lens actuator 70 is mounted on an optical disk 71 (information recording medium, FIG.
Objective lens 50 for condensing the light beam incident on the
Lens holder 5 for holding the lens so as to face the disc 71
1 is provided. The lens holder 51 is configured as a rectangular parallelepiped having a substantially square planar shape.

The lens holder 51 is fixed to a fixing member 58 (supporting mechanism) by a pair of elastic supporting members 59a and 59b which are bent at a right angle, whereby the focusing direction 52 and the tracking direction 5 are set.
3 and is pivotally movable in two orthogonal tilt directions of an optical axis 57 of the objective lens 50, ie, a radial tilt direction 54 (disc radial tilt) and a tangential tilt direction 55 (disc tangential tilt). It is freely supported.

Also, at the four corners of the lens holder 51,
As shown in FIGS. 1 and 2, four magnets 56a,
Two pairs 56b, 56c and 56d are mounted on both sides of the lens holder 51 with the objective lens 50 interposed therebetween, and one side of the lens holder 51 (the side of the fixing member 58).
And two magnets 56c and 56d on the other side (opposite to the fixing member 58).
Are the opposite poles of the lens holder 5
1 (the fixing members 58 in the magnets 56a and 56b).
Direction).

Also, corresponding to the magnets 56a and 56b and 56c and 56d of each set, each magnet set 56
A pair of magnetic bodies 60a and 60b are provided so as to be opposed to the sets 56a and 56b and 56c and 56d of each magnet at intervals from a and 56b and 56c and 56d. For this reason, the magnetic body 60a forms a closed (closed magnetic circuit type) magnetic circuit MC together with the magnets 56a and 56b as shown in FIG. 2, and forms a magnetic gap region M1 as shown in FIG. On the other hand, the magnetic body 60b forms a similar closed magnetic circuit MC together with the magnets 56c and 56d as shown in FIG. 2, and forms a magnetic gap region M2 as shown in FIG.

Various driving coils, that is, focusing coils 61a, 61b, 61c, 61d, and a tracking coil correspond to each of the pair of magnetic gap regions M1 and M2 formed by the pair of magnetic bodies 60a and 60b. Coil 62a, 62b, radial tilt coil 63
a, 63b and tangential tilt coil 64
a, 64b, 64c, 64d, focusing coils 61a, 61b, 61c, 61d, tracking coils 62a, 62b, radial tilt coils 63a, 63b, and a tangential tilt coil 6
4a, 64b, 64c, 64d, a predetermined current is arbitrarily applied to each of the focusing coils 61a, 64b, 64c, 64d.
a, 61b, 61c, 61d, tracking coil 6
2a, 62b, radial tilt coils 63a, 63b
And tangential tilt coils 64a, 64b,
A predetermined Lorentz force is generated in each of the magnets 64c and 64d, and the reaction force is simultaneously generated by the magnets 56a, 56b and 56d.
c, 56d, the lens holder 5
1 can be arbitrarily moved in the desired four axis directions.

In the present embodiment, as shown in FIG. 3, tangential tilt coils 64a, 64b,
64c, 64d are adhered to the magnetic bodies 60a, 60b, and the tangential tilt coils 64a, 64b, 64
Radial tilt coils 63a and 63b are adhered to c and 64d, and focusing coils 61a, 61b, 61c and 61d are attached to the radial tilt coils 63a and 63b.
Are adhered, and the focusing coils 61a, 61b,
Tracking coils 62a and 62b are provided at 61c and 61d.
Is glued.

The tangential tilt coils 64a, 64b, 64c, 64d, the radial tilt coils 63a, 63b, and the focusing coil 61
As shown in FIG. 3, a, 61b, 61c, and 61d have only a part (drive coil effective length part) arranged in the magnetic gap region M1, M2, and other parts (drive coil parts other than the drive coil effective length). Are protruded from the magnetic gap regions M1 and M2 in the direction opposite to the disk 71.
The reason why the direction of the projection is opposite to the disk is to avoid physical interference with the disk 71.

Next, the operation of the present embodiment having the above configuration will be described.

The objective lens actuator 70 of the present embodiment comprises focusing coils 61a, 61b, 61
c, 61d, tracking coils 62a, 62b, radial tilt coils 63a, 63b or tangential tilt coils 64a, 64b, 64c, 64.
d is given an arbitrary current, so that the focusing coils 61a, 61b, 61c, 61
d, a predetermined Lorentz force is generated in each of the tracking coils 62a, 62b, the radial tilt coils 63a, 63b, or the tangential tilt coils 64a, 64b, 64c, 64d.

When a Lorentz force is generated in each drive coil, the reaction force is simultaneously applied to each of the magnets 56a, 56b, 5
6c and 56d, the lens holder 51 is arbitrarily moved in a desired direction.

Here, the tangential tilt coils 64a, 64b, 64c, 64d, the radial tilt coils 63a, 63b, and the focusing coil 61
As for a, 61b, 61c and 61d, only a part (drive coil effective length part) is arranged in the magnetic gap area M1, M2, and the other parts (drive coil parts other than the drive coil effective length) are magnetic gap areas M1, M2. And the disk 71 is arranged to protrude in the opposite direction to the disk 71, so that the Lorentz force generated in the effective length of the drive coil is not weakened by the Lorentz force generated in other portions, and high drive sensitivity can be obtained.

Further, each of the magnetic bodies 60a and 60b, each set of magnets 56a and 56b, and
6d form a closed magnetic circuit MC, so that higher drive sensitivity can be obtained.

As described above, according to the present embodiment, the tangential tilt coils 64a, 64b, 64
c, 64d, radial tilt coils 63a, 63b and focusing coils 61a, 61b, 61c, 6
1d is arranged such that a part thereof is disposed in the magnetic gap regions M1 and M2, and the other part protrudes from the magnetic gap regions M1 and M2 in a direction opposite to the disk 71. For this reason, the Lorentz force generated by the Lorentz force generated in one portion (the driving coil effective length portion) disposed in the magnetic gap regions M1 and M2 is generated in the other portion (the driving coil portion other than the driving coil effective length). The degree of reduction by force is extremely small, and the driving sensitivity can be significantly increased.

According to the present embodiment, each magnetic body 6
Oa, 60b, each set of magnets 56a, 56b, and magnets 56c, 56d form a closed magnetic circuit MC, so that drive sensitivity can be further enhanced.

FIGS. 5 and 6 show the results of the magnetic field analysis of the present embodiment as an aid to the effect of the present embodiment. FIG. 5 shows the magnets 56a, 56 according to the present embodiment.
FIG. 9B is an analysis result of the magnetic flux 66 generated in the model coil 65 when the model coils 65, 56c, 56d and the magnetic bodies 60a, 60b are modeled and the model coil 65 is arranged in the magnetic gap regions M1, M2. FIG. 6 is a magnetic field analysis result obtained by enlarging one side portion of the model coil 65 of the magnetic field analysis result shown in FIG.

Next, the magnet is arranged in the same manner as in the conventional objective lens actuator shown in FIGS. 15 and 16, and the entire drive coil is arranged in the magnetic gap region. The other structure is the same as that of the present embodiment. A conventional type objective lens driving actuator 15 is
It is considered as a comparative object to the present embodiment.

Such an objective lens actuator 15
Is shown in FIG. In addition, in the objective lens driving actuator 15, as shown in FIG. 19, an open magnetic circuit MO is formed.

The following table shows the results of analysis of the average magnetic flux density generated at each drive coil position for the objective lens actuator 15 and the objective lens actuator 70 of the present embodiment.

[0058]

[Table 1] From these magnetic field analysis results, the objective lens actuator 70 of the present embodiment shows that the driving force due to the Lorentz force generated in the driving coil effective length portion (part) disposed in the magnetic gap regions M1 and M2 is It can be seen that the degree of decrease by the Lorentz force generated in the drive coil portion (other portion) other than the effective length is extremely small. That is, according to the present embodiment, the driving sensitivity is significantly improved.

In the present embodiment, focusing coils 61a, 61b, 61c, 61d, tracking coils 62a, 62b, radial tilt coils 63a, 63b, and tangential tilt coils 64a, 64b, 64c, 64d. Although it is directly or indirectly fixed to the magnetic members 60a and 60b as a so-called flat coil, it goes without saying that the configuration of the drive coil and the magnetic circuit can be variously modified without departing from the gist of the present invention.

For example, the tracking coils 62a, 62
2b, only the magnetic members 60a and 60b are provided as shown in FIG.
The configuration wound around b may be used. Alternatively, only the radial tilt coils 63a and 63b may be wound around the magnetic bodies 60a and 60b as shown in FIG. Further, only the tracking coils 62a and 62b and the radial tilt coils 63a and 63b are
The configuration wound around a and 60b may be used.

In short, what is important in the present invention is that, in order to improve the drive sensitivity of the objective lens actuator 70, the drive force generated in the drive coil effective length portion is controlled so that the portion other than the drive coil effective length is not reduced. The drive coil portion (other portion) other than the effective coil length is changed to a substantial magnetic gap region M in the focusing direction of the magnetic circuit.
1. To protrude from M2 to the opposite side of the disk in the focusing direction.

In this embodiment, the focusing coils 61a, 61b, 61c, 61d, the tracking coils 62a, 62b, the radial tilt coils 63a, 63b, and the tangential tilt coils 64a, 64b, 64c, 64d. Is a flat, flat coil that is not bent. The reason that each drive coil is a flat flat coil that is not bent is that if the drive coil is bent, cracks will be generated in the coil bent portion, and disconnection of the coil or short-circuit of the coil will occur.

Next, the configuration of an objective lens actuator according to a second embodiment of the present invention is shown in FIGS.

FIG. 7 is a perspective view of the objective lens driving actuator 75 of the present embodiment, FIG. 8 is a plan view thereof, FIG. 9 is a side view thereof, and FIG. 10 is a front view thereof.

As shown in FIGS. 7 to 10, the objective lens actuator 75 of the present embodiment has the same structure as that of FIG. 1 except that a reflection mirror 68 is provided between protruding portions (other portions) of the drive coil. To the first embodiment shown in FIG. In the second embodiment, the same parts as those in the first embodiment shown in FIGS. 1 to 4 are denoted by the same reference numerals, and detailed description is omitted.

In order to guide the light beam 67 emitted from the optical system (not shown) to the objective lens 50,
It is conventionally known that the reflection mirror 68 is provided on the opposite side of the disk (not shown) (the lower side of 68 in the figure). However, in the configuration shown in FIGS. Dead space around 68,
The drive coil portion (other portion) other than the effective length of the drive coil is used to project from the substantial magnetic gap regions M1 and M2 to the opposite side of the disk in the focusing direction. That is, in the objective lens actuator 75 of the present embodiment, the driving sensitivity is greatly improved without increasing the thickness in the focusing direction as a conventional optical head.

Next, an objective lens driving actuator according to a third embodiment of the present invention will be described.

FIG. 11 is a perspective view showing a configuration of an objective lens driving actuator according to the third embodiment, FIG. 12 is a plan view thereof, FIG. 13 is a side view thereof, and FIG. 14 is a front view thereof. As shown in FIGS. 11 to 14, the objective lens driving actuator 80 of the present embodiment
The lens holder 51 for holding the focusing direction 5
This is a device that is driven only in two axis directions of the tracking direction 2 and the tracking direction 53.

In the objective lens actuator 80 of the present embodiment, the lens holder 51 integrally has support member mounting portions 81a and 81b protruding in the tracking direction 53, and the support member mounting portions 81a and 81b are perpendicular to each other. The lens holder 51 is fixed to the fixing member 58 (supporting mechanism) by four linear elastic supporting members 69a, 69b, 69c, 69d instead of the bent supporting member, so that the lens holder 51 is in the focusing direction 52 and the tracking direction. 53 movably supported.

The objective lens actuator 80 is
Focusing coils 61a, 61 as drive coils
b, 61c, 61d and the tracking coil 62a,
62b only. As shown in FIGS. 12 and 13, focusing coils 61a, 61b, 61c,
61d is adhered to the magnetic bodies 60a, 60b, and the tracking coils 62a, 62b are adhered to the focusing coils 61a, 61b, 61c, 61d. Then, the focusing coils 61a, 61b, 61c,
61d is only a part of the magnetic gap region M1, M2
And the other portions are arranged to protrude from the magnetic gap regions M1 and M2 in a direction opposite to the disk 71.

Other configurations are the same as those of the first embodiment. In the third embodiment, the same parts as those in the first embodiment shown in FIGS. 1 to 4 are denoted by the same reference numerals, and detailed description is omitted.

In the present embodiment, a predetermined current is arbitrarily applied to each of the focusing coils 61a, 61b, 61c, 61d or the tracking coils 62a, 62b, so that the focusing coil 6
A predetermined Lorentz force is generated in each of 1a, 61b, 61c, 61d or the tracking coils 62a, 62b, and at the same time, the reaction force is generated by the magnets 56a, 56b.
Since it occurs in each of b, 56c, and 56d, the lens holder 51 can be arbitrarily moved in a desired biaxial direction.

According to the present embodiment, a part of the focusing coils 61a, 61b, 61c, and 61d (the effective length of the drive coil) is within the magnetic gap region M1,
M2, and other portions (drive coil portions other than the effective length of the drive coil) protrude from the magnetic gap regions M1, M2 in the direction opposite to the disk 71, and therefore are disposed in the magnetic gap regions M1, M2. The driving force due to the Lorentz force generated in the part (the driving coil effective length part) is changed to the other part (the driving coil part other than the driving coil effective length)
The degree of reduction by the Lorentz force generated in the above becomes extremely small, and the drive sensitivity can be increased.

Also in this embodiment, the focusing coils 61a, 61b, 61c, 61d and the tracking coils 62a, 62b are directly or indirectly fixed to the magnetic members 60a, 60b as so-called flat coils. However, it goes without saying that the configurations of the drive coil and the magnetic circuit can be variously modified without departing from the gist of the present invention. For example, the tracking coil 62
a and 62b are the magnetic members 60 as shown in FIG.
The configuration wound around a and 60b may be used.

In this embodiment, the focusing coils 61a, 61b, 61c, 61d and the tracking coils 62a, 62b are flat, flat, unfolded coils. The reason that each drive coil is a flat flat coil that is not bent is that if the drive coil is bent, cracks will be generated in the coil bent portion, and disconnection of the coil or short-circuit of the coil will occur.

Further, the objective lens actuator 80 of this embodiment can be provided with a reflection mirror similarly to the second embodiment shown in FIGS. 7 to 11. In this case, the unused space around the reflection mirror 68 generated by the reflection mirror 68, that is, the dead space can be effectively used, so that the thickness in the focusing direction as the optical head is not increased, The drive sensitivity of the actuator can be greatly improved.

[0077]

As described above, according to the present invention,
Since the other part of the flat-shaped drive coil that is not bent (the drive coil part other than the effective length of the drive coil) is arranged to protrude from the magnetic gap area in the direction opposite to the disk, it is arranged in the magnetic gap area. The driving force due to Lorentz force generated in one part (drive coil effective length part) is different from that in other parts (drive coil part other than the drive coil effective length)
The degree of decrease is extremely small due to the Lorentz force generated in the above, and it is possible to realize high driving sensitivity of the moving magnet type objective lens actuator.

Further, according to the present invention, a magnetic circuit in which a magnetic body and a set of magnets are closed forms a magnetic circuit, so that a high driving sensitivity of a moving magnet type objective lens actuator can be realized.

Therefore, in recent years, the speed of the optical disk device has been increased,
It is possible to provide a moving magnet type objective lens actuator having high driving sensitivity, capable of realizing miniaturization, thinning, and high speed in response to portability, personalization, and mobility.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of an objective lens actuator according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a configuration of the objective lens actuator according to the first embodiment of the present invention.

FIG. 3 is a side view showing a configuration of the objective lens actuator according to the first embodiment of the present invention.

FIG. 4 is a front view showing the configuration of the objective lens actuator according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a magnetic field analysis result of the objective lens actuator according to the first embodiment of the present invention.

FIG. 6 is an enlarged view of one side portion of the drive coil as a result of the magnetic field analysis shown in FIG. 5;

FIG. 7 is a perspective view illustrating a configuration of an objective lens actuator according to a second embodiment of the present invention.

FIG. 8 is a plan view showing a configuration of an objective lens actuator according to a second embodiment of the present invention.

FIG. 9 is a side view illustrating a configuration of an objective lens actuator according to a second embodiment of the present invention.

FIG. 10 is a front view showing a configuration of an objective lens actuator according to a second embodiment of the present invention.

FIG. 11 is a perspective view illustrating a configuration of an objective lens actuator according to a third embodiment of the present invention.

FIG. 12 is a plan view showing a configuration of an objective lens actuator according to a third embodiment of the present invention.

FIG. 13 is a side view illustrating a configuration of an objective lens actuator according to a third embodiment of the present invention.

FIG. 14 is a front view showing a configuration of an objective lens actuator according to a third embodiment of the present invention.

15A is a front view of a conventional moving magnet type actuator, and FIG. 15B is a cross-sectional view taken along line AA of FIG.

FIG. 16 is an exploded perspective view showing a configuration of a conventional moving magnet type actuator.

FIG. 17 is a schematic diagram showing a magnetic circuit in the vicinity of a focus drive coil of a conventional moving magnet type actuator viewed from a focus direction.

FIG. 18 is a schematic diagram showing a magnetic circuit in the vicinity of a tracking drive coil of a conventional moving magnet type actuator viewed from a tracking direction.

FIG. 19 is a perspective view showing a conventional type objective lens driving actuator assumed to explain the effects of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Objective lens 2 Lens holder 3a, 3b Magnet 4a, 4b, 4c, 4d Metal wire 5a, 5b Magnetic yoke 6a, 6b Tracking coil 7a, 7b Focus coil 8 Fixing member 9 Base 10 Optical unit 11 Disk 12 Mirror 15 Objective lens actuator 31 Flow of magnetic flux 32, 33, 34, 35 Direction of flowing current 40 Tracking drive coil 41 Flow of magnetic flux 42, 43, 44, 45 Direction of flowing current 50 Objective lens 51 Lens holder 52 Focusing direction 53 Tracking direction 54 Radial tilt direction (disk radial direction tilt) 55 Tangential tilt direction (disk tangential direction tilt) 56a, 56b, 56c, 56d Magnet 57 Optical axis 58 Fixing member 59a, 59b Supporting member 60a, 60 Magnetic body 61a, 61b, 61c, 61d Focusing coil 62a, 62b Tracking coil 63a, 63b Radial tilt coil 64a, 64b, 64c, 64d Tangential tilt coil 65 Model coil 66 Magnetic flux 67 Light beam 68 Reflecting mirror 69a 69b, 69c, 69d Supporting members 70, 75, 80 Objective lens actuator 71 Disk

Claims (4)

[Claims] 1. A holder for holding an objective lens provided facing an information recording medium which can be arranged at a predetermined position, a support mechanism for movably supporting the holder, and provided on the holder. A magnet, a magnetic body that forms a magnetic gap region with the magnet, a drive coil partly disposed in the magnetic gap region, and another portion protruding from the magnetic gap region in a direction opposite to the disk, An objective lens actuator comprising: 2. The objective lens actuator according to claim 1, wherein the other portion of the drive coil projects in a direction perpendicular to the disk. 3. The magnet is provided on both sides of the holder with the objective lens as a center. A pair of the magnetic materials is provided for each of the magnets with the objective lens as a center. A pair is arranged corresponding to each of a pair of magnetic gap regions formed by the pair of magnetic bodies, and a reflection mirror is provided between other protruding portions of the pair of drive coils. The objective lens actuator according to claim 1. 4. A holder for holding an objective lens provided opposite to an information recording medium that can be arranged at a predetermined position, a support mechanism for movably supporting the holder, and one side of the holder. At least one set of magnets provided with poles opposite to each other, a magnetic body forming a closed magnetic circuit together with the set of magnets and forming a magnetic gap region, and at least a part disposed in the magnetic gap region An objective lens actuator, comprising: