JP2002157762A - Objective lens driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an objective lens driver whose number of components can be decreased by integrating a tracking coil and a tracking magnet used to apply tracking control to an objective lens into one. SOLUTION: The objective lens driver is provided with a base 2 to which a spindle 5 is formed, a lens holder 4 that is slidably placed to the spindle and holds an objective lens 3 at one end, a couple of focusing coils 14 that are placed opposite to the lens holder 4, a couple of focusing magnet 7 provided to the base 2, the tracking coil 16 placed opposite to the mount position of the objective lens 3 of the lens holder 4 and the tracking magnet 9 provided to the base 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an objective lens driving device for displacing an objective lens in a focusing direction and a tracking direction.

[0002]

2. Description of the Related Art Conventionally, an optical pickup device used for recording / reproducing an optical disk has an optical pickup provided with a semiconductor laser for emitting a light beam and a photodetector for receiving a return light beam reflected on a signal recording surface of the optical disk. A block unit and an objective lens driving device for condensing a light beam emitted from a semiconductor laser and moving an objective lens for irradiating a signal recording surface of an optical disc in a tracking direction or a focusing direction are provided.

For example, as shown in FIG. 17, an objective lens driving device 101 includes a base 10 on which a support shaft 102 is formed.
And a lens holder 105 which holds the objective lens 104 at one end and is slidable in a focusing direction which is an optical axis direction of the objective lens 104 and a tracking direction which is a rotation direction about the support shaft 102. And The objective lens driving device 101 includes a pair of focusing coils 106 and 106 attached to the lens holder 105 so as to face each other.
A pair of tracking coils 107, 107 mounted opposite to each other, a pair of focusing magnets 108, 108 disposed on the base 103 so as to face the pair of focusing coils 106, 106, and a pair of focusing magnets 108, 108 on the base 103. Tracking coils 107, 107
And a pair of tracking magnets 109, 109 disposed so as to face each other. Further, on the other end side of the lens holder 105, the objective lens 1 around the support shaft 102 is provided.
A balancer 111 for balancing the weight with the balance 04 is provided. Further, the lens holder 105 has a neutral iron piece 1 at the center of each of the coils 106, 106, 107, 107 for holding a neutral position of the lens holder 105 made of a magnetic material in the focusing and tracking directions.
12, 112, 113 and 113 are provided.

[0004] The objective lens driving device 101 uses the driving current supplied to the focusing coils 106 and 106 and the magnetic field formed by the focusing magnets 108 and 108 to move the lens holder 105 to the objective lens 10.
4 in the direction of the optical axis to control the focusing of the objective lens 104.
The lens holder 105 is rotated about the support shaft 102 by the drive current supplied to the power supply 07 and the magnetic field formed by the tracking magnets 109, 109 to perform tracking control of the objective lens 104. Then, the objective lens driving device 101 includes the focusing coils 106, 1
06 and the tracking coils 107, 107 when the drive current is not supplied, the neutral iron pieces 112, 112, 11
3, 113 are magnets 106, 106, 107, 1
07, the neutral position of the objective lens 104 in the focusing and tracking directions is maintained.

The objective lens driving device 101 as described above
The lens holder 105 is supported by the support shaft 102, the focusing coils 106, 106 and the tracking coils 107, 107 are respectively disposed on the lens holder 105 so as to face each other, and further, are opposed to the objective lens 104. A balancer 111 is provided. Therefore,
The objective lens driving device 101 has a weight balance with respect to the support shaft 102, has excellent seismic resistance in the tracking direction, can prevent the tilt of the objective lens 104 with respect to the disk, and has a lens holder formed by an elastic arm such as a leaf spring. It is possible to prevent the lens holder 105 from moving downward by its own weight as compared with the objective lens driving device supported by the base.

[0006]

However, such an objective lens driving device 101 has a lens holder 105.
In addition, a total of four coils are provided, a pair of focusing coils 106, 106 and tracking coils 107, 107, and a balancer 111 is provided to balance the weight with the objective lens 104.
It has been difficult to further reduce the size and weight. The objective lens driving device 101 includes a coil 106,
The number of parts such as 107, magnets 108, 109, balancer 111, etc. increases, which not only complicates the assembly work,
It is also difficult to reduce costs.

SUMMARY OF THE INVENTION An object of the present invention is to provide an objective lens driving device capable of reducing the number of parts and reducing the size by using one tracking coil and one tracking magnet for performing tracking control of the objective lens. To provide.

Another object of the present invention is to provide a tracking drive section at a position opposite to the objective lens mounting position of the holder to balance the weight so that the holder holding the objective lens can be smoothly moved in the focusing direction and the tracking direction. It is an object of the present invention to provide a movable objective lens driving device.

It is another object of the present invention to supply power to a focusing coil and / or a tracking coil by a long flexible printed circuit board so as not to hinder focusing control and tracking control. An object of the present invention is to provide a lens driving device.

[0010]

In order to solve the above-mentioned problems, an objective lens driving device according to the present invention comprises a base having a support shaft formed in the optical axis direction of the objective lens, and a support shaft having the objective lens mounted on the support shaft. A holder that is slidably provided in the optical axis direction and a rotation direction about the support shaft, and that holds an objective lens at one end and at least a pair of first coils provided on one of the base and the holder And a first driving unit, which is provided opposite to the first or second pair of magnets provided on one of the base and the holder, and is provided opposite to each other with the support shaft interposed therebetween, and drives the holder in the optical axis direction of the objective lens. And a second coil provided on one of the base and the holder, and a second magnet provided on the other of the base and the holder, and are opposed to one end holding the objective lens and the support shaft therebetween. Provided that the other end comprises a holder, a second driving unit which rotates around the support shaft.

Here, the objective lens and the second driving section are:
The weight is set such that the moments are balanced with the support shaft as a fulcrum.

Also, a pair of the first coil and / or the second
The coil is supplied with a drive current via a printed wiring board in response to a signal from an external circuit, and the printed wiring board is formed so that the movable end side is curved with respect to the fixed end side. It is curved.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an objective lens driving device to which the present invention is applied will be described with reference to the drawings.

The objective lens driving device 1 is mounted on an optical pickup device, and displaces an objective lens in a focusing direction and a tracking direction in order to perform focusing control and tracking control. Specifically, as shown in FIGS. 1, 2, and 3, the objective lens driving device 1 includes a base 2 serving as a fixed portion and a lens holder 4 holding an objective lens 3 serving as a movable portion with respect to the base 2. Prepare.

A support shaft 5 is erected on the base 2 substantially perpendicular to the base 2. That is, this support shaft 5
It is provided upright in the optical axis direction of the objective lens 3. Further, first magnet attachment pieces 6, 6 for attaching the focusing magnets 7, 7 are formed opposite to each other at both ends in the long side direction of the base 2 in a bent manner. The first magnet attachment pieces 6 and 6 also function as yokes, and have substantially rectangular focusing magnets 7 and 7 attached thereto. These focusing magnets 7,
As shown in FIG. 3, the focusing magnet 7 is divided into two parts in the horizontal direction.
It is magnetized so as to form a pole, and the lower side is magnetized so as to form an S pole on the inside and an N pole on the outside. The other focusing magnet 7 is magnetized so that the upper side faces the focusing coil and forms the S pole and the outer side forms the N pole, and the lower side forms the N pole and the outer side forms the S pole. It is magnetized. As described above, the focusing magnets 7, 7 can efficiently generate a driving force in the focusing direction by changing the magnetization direction between the upper side and the lower side in accordance with the direction in which the current flows through the focusing coil opposed thereto. Like that.

The focusing magnets 7, 7
May be magnetized in the opposite direction to the above-described example. That is,
One of the focusing magnets 7 is magnetized so that the upper side faces the focusing coil and the outer side is an S pole and the outer side is an N pole, and the lower side is an N pole and the outer side is an S pole.
The other focusing magnet 7 is magnetized so that the inside facing the focusing coil is an N pole and the outside is an S pole,
The lower side is magnetized so that the inside is an S pole and the outside is an N pole.

By the way, as shown in FIG. 4A, when the surfaces of the two focusing magnets 7, 7 facing the focusing coil are the same magnetic pole, for example, the upper side is an N pole and the lower side is an S pole. The leakage magnetic flux indicated by the middle arrow bends in the vertical direction, and particularly the upwardly bent leakage magnetic flux flows toward the optical disk D mounted on the disk table constituting the disk rotation drive mechanism. In the objective lens driving device 1 to which the present invention is applied, as shown in FIG. 4B, the opposing surfaces of the pair of focusing magnets 7 have different magnetic poles. The surface facing the focusing coil is magnetized so that the upper side is the north pole and the lower side is the south pole, and the surface of the other focusing magnet 7 facing the focusing coil is the upper side is the south pole and the lower side is the north pole. I do. As a result, the leakage magnetic flux indicated by the arrow in the figure flows linearly, and as shown in the example of FIG.

At one end of the base 2 in the short side direction,
As shown in FIG. 1 and FIG.
The second magnet mounting piece 8 for mounting the second magnet is bent. The second magnet attachment piece 8 also functions as a yoke, and has a substantially rectangular tracking magnet 9 attached thereto. As shown in FIG. 1, the tracking magnet 9 is vertically divided into two parts. One side is magnetized so that the inside is an N pole and the other side is an S pole, and the other side is an S pole. It is magnetized so that the outside becomes the N pole. As described above, the tracking magnet 9 changes the direction of magnetization on one side and the other side in accordance with the direction of current flow of the tracking coil opposed thereto, so that the driving force in the tracking direction can be efficiently generated. I have to.

The tracking magnet 9 may be magnetized in a direction opposite to the above-described example. That is, the tracking magnet 9 is magnetized so that one side has an S pole on the inside and an N pole on the outside, and the other side has an N pole on the inside.
It is magnetized so that it has no pole and the outside is an S pole.

As shown in FIGS. 1 and 2, the lens holder 4 is attached to the base 2 so as to be movable in the axial direction of the support shaft 5 and in the direction of rotation. This lens holder 4
The whole is molded in a substantially rectangular shape from a material having high rigidity and low frictional resistance such as a liquid crystal polymer so as to slide smoothly on the support shaft 5, and a cylindrical portion 11 is formed in a substantially central portion. ing. The cylindrical portion 11 is provided with an insertion hole 12 through which the support shaft 5 is inserted. The insertion hole 12 is formed such that the length in the longitudinal direction is shorter than the height of the support shaft 5 and moves in the axial direction. Have to be able to. When the support shaft 5 is inserted into the insertion hole 12, the cylindrical portion 11 can support the support shaft 5 during the focusing control of the objective lens 3.
, And is rotated about the support shaft 5 during tracking control of the objective lens 3. The support shaft 5
A lubricant may be applied to the surface of the support member 5 and / or the surface of the insertion hole 12 in order to make the cylindrical portion 11 easily slide on the support shaft 5.

A lens mounting portion 13 for mounting the objective lens 3 is opened at the tip side of the lens holder 4. The objective lens 3 is attached to the lens attachment portion 13 by press fitting or the like. Then, the lens mounting portion 13 is arranged as shown in FIG.
As shown in (1), the objective lens 3 is held so that the optical axis of the attached objective lens 3 is substantially perpendicular to the signal recording surface of the optical disc D.

On both sides of the lens holder 4 in the long side direction, a focusing coil 1 wound in a substantially rectangular shape is provided.
4, 14 are provided. The focusing coils 14 are adhered to the side surface of the lens holder 4 by, for example, an ultraviolet-curing adhesive or the like. When the lens holder 4 is mounted on the base 2, the focusing coils 14, 14 are opposed to the focusing magnets 7, 7 at a predetermined interval. Since the focusing coils 14 and 14 are provided at positions facing each other with the support shaft 5 interposed therebetween, they are provided at positions where the distance between the support shafts 5 is equal, and the number of windings is the same and the mass is equal. Is provided.

As shown in FIGS. 1 to 3 and 5, the focusing of the lens holder 4 on which the objective lens 3 is mounted is provided on both sides of the lens holder 4 inside the focusing coils 14 and 14 in the long side direction. Iron pieces 15, 1 for maintaining a neutral position in the tracking and tracking directions
5 is attached. The neutral iron pieces 15 and 15 are formed of a magnetic material, and the focusing magnets 7 and 7
By being disposed in the magnetic field formed by the focusing magnets 7, the focusing magnets 7, 7 become magnetically attracted portions. These neutral iron pieces 15, 15 are disposed so that the distance from the support shaft 5 is the same so that the attraction force to the focusing magnets 7, 7 is the same.

The neutral iron pieces 15 and 15 are attached to both long sides of the lens holder 4 so that the focusing direction is the longitudinal direction, and the circumferential surface R1 is turned around the lens holder 4 shown in FIG. It is formed so as to have a curvature smaller than that of the moving trajectory R2.

That is, as shown in FIG. 6A, when the neutral iron pieces 15, 15 are formed of a member having a curvature larger than the rotation locus R2 of the lens holder 4, for example, a substantially rectangular plate-like body, 6B, the side edges of the neutral iron pieces 15, 15 are magnetically attracted to the focusing magnets 7, 7, and the neutral position of the lens holder 4 in the tracking direction, as shown in FIG. Cannot be held.

Objective lens driving device 1 to which the present invention is applied
As shown in FIG. 1, the neutral iron pieces 15, 15
Is constituted by a rod-shaped member having a smaller curvature than the rotation locus R2 of the lens holder 4 shown in FIG.
Even when the lens holder 4 rotates in the tracking direction, the side edges of the neutral iron pieces 15, 15 are not magnetically attracted to the focusing magnets 7, 7, and the magnetic attraction is provided at the center of the focusing magnets 7, 7 in the tracking direction. Is done. Thus, the lens holder 4 rotates about the support shaft 5 and can accurately maintain the neutral position in the tracking direction.

In the focusing direction, the neutral iron pieces 15, 15 formed to be longer than the focusing direction, the tracking direction, and attached with the focusing direction as the longitudinal direction, have the highest magnetic flux density of the focusing magnets 7, 7. The magnets are magnetically attracted to the center of the focusing magnets 7 in the focusing direction. As a result, the lens holder 4 moves along the support shaft 5 and can accurately maintain the neutral position in the focusing direction.

FIGS. 1 and 2 show a side surface of the lens holder 4 opposite to the lens mounting portion 13 with the cylindrical portion 11 interposed therebetween.
As shown in FIG. 1, a tracking coil 16 wound in a substantially rectangular shape is provided. This tracking coil 16
Is adhered to the side surface of the lens holder 4 by, for example, an ultraviolet-curable adhesive. When the lens holder 4 is attached to the base 2, the tracking coil 16 faces the tracking magnet 9 with a predetermined interval.
Since such a tracking coil 16 is provided at a position facing the objective lens 3 with the support shaft 5 interposed therebetween, the tracking coil 16 is provided so as to balance the moment with the objective lens 3. For example, the tracking coil 14 has the same distance from the support shaft 5 to the objective lens 4 and the distance from the support shaft 5 to the tracking coil 16 and determines the mass such as the number of windings.

As shown in FIG. 7, the focusing coils 14, 14 and the tracking coils 16, 16
In other words, the conductor may be wound around the coil engaging pieces 18 and 19 provided on the side wall of the lens holder 4 and attached to the side wall.

As shown in FIG. 2, a projection 21 for preventing the objective lens 3 and the optical disk D from directly contacting each other is provided on the lens holder 4 as shown in FIG.
Is provided. The projection 21 is formed to be higher than the top of the second surface of the objective lens 3 on the optical disk D side. As a result, even when the optical disk D mounted on the disk table of the disk rotation drive mechanism is shaken due to vibration or the like, the protrusion 21 contacts the objective lens 3 and damages the objective lens 3. To prevent sticking.

By the way, as shown in FIGS. 1 and 2, the base 2 is used to supply a driving current to each of the focusing coils 14, 14 and the tracking coil 16.
Is provided with a printed wiring board 22 having flexibility. As shown in FIG. 8, the printed wiring board 22 includes a board main body 23 attached to the bottom surface of the base 2.
A first lead-out portion 24 having a connecting portion 24a to which at least one focusing coil 14 is connected is provided at a distal end portion, and a connecting portion 25a to which at least the other focusing coil 14 is connected is provided at a distal end portion. It comprises a second lead-out section 25 and a third lead-out section 26 provided with a connecting section 26a connected to an external focusing servo circuit, tracking servo circuit, or the like, provided at the tip end.
The first lead-out part 24 and the second lead-out part 25 are formed to be elongated so as to be substantially parallel to each other, and bend and deform not only in the thickness direction but also in the force applied in the width direction. It is formed to be easy.

The printed wiring board 22 has a first
And the second deriving units 23 and 24 are connected to the tracking coil 16.
The substrate body 23 is fixedly attached to the lower surface of the base 2 on the side. Then, the first and second deriving units 23, 2
4 is approximately 360 from the base end on the fixed end side to the top end side.
°, it is bent and deformed into a substantially spiral shape, and the tip end side is locked to the lens holder 4. Thereby, the first derivation unit 24 and the second derivation unit
Constitutes a curved portion. One of the focusing coils 14 is connected to the connection part 24a of the first lead-out part 24 by solder or the like, and the other focusing coil 14 is connected to the connection part 25a of the second lead-out part 25 by solder or the like. Is done. Furthermore, the connection part 24a of the first lead-out part 24 and / or the connection part 25a of the second lead-out part 25
Is connected to the tracking coil 16 by soldering or the like.

When power is supplied to the focusing coils 14, 14 and the tracking coil 16 from the outside in this manner, the substrate main body 23 fixed to the base 2, which is a fixed portion, is used.
The focusing coils 14, 14 attached to the lens holder 4 as the movable part and the tracking coil 16 are connected by a curved part formed by elongated first and second lead-out parts 24, 25. The spring component can be removed from the first and second deriving sections 24 and 25, and the focusing control and the tracking control can be accurately performed.

Next, the operation of the objective lens driving device 1 configured as described above will be described with reference to the drawings.
First, when the optical disk D is not irradiated with the light beam, the driving current is not supplied to the focusing coils 14 and 14 and the tracking coil 16. Therefore, as shown in FIGS. 1 and 2, the lens holder 4 is configured such that the neutral iron pieces 15, 15 have magnetic attraction in the direction of the center of the focusing magnets 7, 7 having the highest magnetic flux density of the focusing magnets 7, in the focusing direction. Is held at the neutral position in the focusing direction. Further, as shown in FIG. 1, in the lens holder 4, the neutral iron pieces 15, 15 are magnetically attracted in the direction of the center of the focusing magnets 7, 7 in the tracking direction, and the neutral position in the tracking direction is maintained.

Next, focusing control of the objective lens 3 will be described. As shown in FIG. 9, when the objective lens 3 is displaced in the direction of arrow A in FIG.
A drive current according to the first focusing servo signal is supplied. Then, the lens holder 4 holding the objective lens 3 is moved to the magnetic field formed by the focusing magnets 7 attached to the first magnet attachment pieces 6 of the base 2 and the focusing coil 14 attached to the lens holder 4. , 14 generates a driving force in the direction of arrow A in FIG.
Are moved in the same direction along the axis, and accordingly, the objective lens 3 held in the lens holder 12 is also moved in the same direction.

Further, as shown in FIG.
When displacing in the direction of arrow B in FIG.
A drive current according to the second focusing servo signal is supplied. Then, the lens holder 4 generates a driving force in the direction of arrow B in FIG. 10 by the action of the magnetic field formed by the focusing magnets 7 and the driving current supplied to the focusing coils 14, 14, and the support shaft 5. Is moved in the same direction along with the lens holder 1.
The objective lens 3 held by 2 is also moved in the same direction.

The focusing coils 14, 14
When the power supply to the lens is stopped, the lens holder 4
The magnetic attraction of the focusing magnets 7, 15 toward the center of the focusing magnets 7, 7 in the focusing direction allows
It moves along the support shaft 5 and returns to the neutral position in the focusing direction.

Next, the tracking control of the objective lens 3 will be described. As shown in FIG. 11, when the objective lens 3 is displaced in the direction of arrow C in FIG. 16 is supplied with a drive current according to the first tracking servo signal. Then, the lens holder 4 holding the objective lens 3 was supplied with power to the magnetic field formed by the tracking magnet 9 attached to the second magnet attachment piece 8 of the base 2 and the tracking coil 16 attached to the lens holder 4. Due to the action with the drive current, a drive force is generated in the direction of arrow C in FIG.
11 in the direction of arrow C in FIG.
The objective lens 3 held by the lens holder 12 is also rotated in the same direction.

When the objective lens 3 is displaced in a direction indicated by an arrow D in FIG.
A drive current corresponding to the tracking servo signal is supplied. Then, the lens holder 4 generates a driving force in the direction of arrow D in FIG. 12 by the action of the magnetic field formed by the tracking magnet 9 and the driving current supplied to the tracking coil 16, and the lens holder 4 is rotated about the support shaft 5. Pivot in the direction
Along with this, the objective lens 3 held by the lens holder 12 is also rotated in the same direction.

When the power supply to the tracking coil 9 is stopped, the lens holder 4 causes the neutral iron pieces 15, 15 to be magnetically attracted to the center of the focusing magnets 7, 7 in the tracking direction. It rotates to the center and returns to the neutral position in the tracking direction.

The objective lens driving device 1 as described above differs from the conventional objective lens driving device 100 in that the objective lens 3
The tracking coil 16 is disposed at a position facing the
Since only one tracking magnet 9 and one tracking coil 16 are provided as a drive unit for controlling the weight of the objective lens 3 and for performing tracking control of the objective lens 3, the number of coils and magnets can be reduced. In addition, the balancer 111 can be eliminated. Further, the objective lens driving device 1 includes a neutral iron piece 1
Since only the focusing coils 14 and 14 are attached to the focusing coils 14 and 14 but not to the tracking coil 16 side, the number of neutral iron pieces can be reduced. As described above, in the objective lens driving device 1, since the number of components is reduced, the overall size can be reduced,
The weight can be reduced, the assembly can be easily performed, the assembly cost can be reduced, and the production efficiency can be improved.

Further, in the objective lens driving device 1, as shown in FIG. 4, the surface of one of the focusing magnets 7 facing the focusing coil has an upper N-pole and a lower S-pole, and the other focusing magnet 7 has a lower S-pole. By setting the surface facing the focusing coil to the S pole on the upper side and the N pole on the lower side, it is possible to eliminate the leakage magnetic flux flowing to the optical disk D side. Therefore, particularly when the objective lens driving device 1 is used in an optical pickup device for a magneto-optical disk, it is possible to prevent the magnetic flux from adversely affecting the magneto-optical disk, and to improve the recording / reproducing characteristics of the magneto-optical disk. Deterioration can be prevented.

Further, the substrate main body 23 fixed to the base 2 as a fixed part, and the focusing coils 14, 14 and the tracking coil 16 attached to the lens holder 4 as the movable part are elongated first and second elongated parts. Derivation unit 24,
Since they are connected by the curved portion constituted by 25, the spring component can be removed from the first and second lead-out portions 24 and 25, and the focusing control and the tracking control can be accurately performed.

Next, another example of the objective lens driving device 1 to which the present invention is applied will be described with reference to the drawings. Note that the same members as those of the above-described objective lens driving device 30 are denoted by the same reference numerals, and the details are omitted.

As shown in FIG. 13, this objective lens driving device 30 is formed by forming a neutral iron piece by bending a flat plate into a semi-circular arc shape, so that the objective lens driving device 1 using two neutral iron pieces described above. The feature is to reduce the number of parts.

As shown in FIG. 13, the neutral iron piece 31 is formed by bending a substantially rectangular flat plate made of a magnetic material and forming a substantially U-shape as a whole. This neutral iron piece 3
Numeral 1 is formed so as to be curved so as to have the same curvature as the outer peripheral surface of the cylindrical body 11 provided on the lens holder 4. That is, as shown in FIG.
Is formed so that the curvature is smaller than the rotation locus R2 of the lens holder 4. Such a neutral iron piece 31
As shown in FIGS. 14 and 15, the focusing magnets 7 are attached to the outer peripheral surface of the cylindrical body 11 in the magnetic field by an adhesive or the like. At this time, the neutral iron piece 31
In order to prevent magnetic attraction by the tracking magnet 9,
It is attached so as to cover the cylindrical body 11 approximately 180 ° from the objective lens 3 side, and at a neutral position in the tracking direction,
The side edge parallel to the optical axis of the objective lens 3 is positioned so as to face the focusing coils 14. Further, since the neutral iron piece 31 is attached to the tubular body 11,
The distance from the support shaft 5 is the same, and the focusing magnets 7, 7 are magnetically attracted by the same attractive force.

The focusing control of the objective lens 3 of the objective lens driving device 30 using such a neutral iron piece 31 will be described. As shown in FIG.
When the optical disc D is displaced in the direction of arrow A in FIG. 15, a driving current corresponding to the first focusing servo signal is supplied to the focusing coils 14. Then, the lens holder 4 generates a driving force in the direction of arrow A in FIG. 15 by the action of the magnetic field formed by the focusing magnets 7 and the driving current supplied to the focusing coils 14, 14, and the support shaft 5. Are moved in the same direction along the axis, and accordingly, the objective lens 3 held in the lens holder 12 is also moved in the same direction. Further, as shown in FIG. 15, when the optical disc D is displaced in the direction of arrow B in FIG. 15, which is separated from the optical disc D, a drive current corresponding to the second focusing servo signal is supplied. Then, the lens holder 4 generates a driving force in the direction of arrow B in FIG. 15 by the action of the magnetic field formed by the focusing magnets 7 and the driving current supplied to the focusing coils 14, 14, and the support shaft 5. Are moved in the same direction along the axis, and accordingly, the objective lens 3 held in the lens holder 12 is also moved in the same direction.

The focusing coils 14, 14
When the power supply to the lens is stopped, the lens holder 4
1 is magnetically attracted to the center of the focusing magnets 7, 7 in the focusing direction, so that the spindle 5
To return to the neutral position in the focusing direction.

Next, the tracking control of the objective lens 3 will be described. As shown in FIG. 14, when the objective lens 3 is displaced in the direction of arrow C in FIG. 16 is supplied with a drive current according to the first tracking servo signal. Then, the lens holder 4
14 generates a driving force in the direction of arrow C in FIG. 14 by the action of a magnetic field formed by the tracking magnet 9 and a driving current supplied to the tracking coil 16, and
, And the objective lens 3 held by the lens holder 12 is also rotated in the same direction.
When the objective lens 3 is displaced in a direction indicated by an arrow D in FIG. 14 orthogonal to a recording track provided on the optical disc D, a drive current corresponding to the second tracking servo signal is supplied to the tracking coil 16. Then
The lens holder 4 generates a driving force in the direction of arrow D in FIG. 12 by the action of the magnetic field formed by the tracking magnet 9 and the driving current supplied to the tracking coil 16, and moves in the same direction about the support shaft 5. The objective lens 3 held by the lens holder 12 is also rotated in the same direction.

When the power supply to the tracking coil 9 is stopped, the lens holder 4 is moved around the support shaft 5 by the magnetic attraction of the neutral iron piece 31 toward the center of the focusing magnets 7, 7 in the tracking direction. It rotates and returns to the neutral position in the tracking direction.

The objective lens driving device 30 as described above includes:
Since the neutral iron piece 31 is composed of one member,
The number of parts can be reduced.

The neutral iron piece 31 may be configured as shown in FIG. This neutral iron piece 32 is a neutral iron piece 15
Similarly, the peripheral surface R1 is formed by bending a rod-shaped member having a smaller curvature than the rotation locus R2 of the lens holder 4 shown in FIG. Suctioned parts 34, 34 which are 180 ° opposite to each other with arc-shaped part 33.
It is composed of Such a neutral iron piece 32
The arc-shaped portion 33 is engaged with a mounting groove provided on the upper end surface of the cylindrical portion 11, and is attached so that the sucked portions 34, 34 face the focusing coils 14, 14. Even with such a neutral iron piece 32, the above-described neutral iron piece 3
As in the case of 1, the number of parts can be reduced.

As described above, with respect to the objective lens driving devices 1 and 30 to which the present invention is applied, the focusing magnets 7 and 7 and the tracking magnet 9 are provided on the base 2 side which is the fixed unit side, and the lens holder 4 side which is the movable unit side. Although the example in which the focusing coils 14 and 14 and the tracking coil 16 are provided has been described, the present invention, on the contrary, provides the focusing magnets 7 and 7 and the tracking magnet 16 on the lens holder 4 side which is the movable portion side. Alternatively, the focusing coils 14 and 14 and the tracking coil 9 may be provided on the base 2 side which is the fixed portion side.

The objective lens driving devices 1 and 30 to which the present invention is applied are applied not only to optical pickup devices for magneto-optical disks but also to optical pickup devices used for read-only optical disks and phase-change optical disks. You can also.

[0055]

According to the objective lens driving apparatus according to the present invention, the holder is provided at the position facing the objective lens, and the second driving portion which rotates around the support shaft is provided. Since the weight is balanced, the number of coils and magnets can be reduced, and a balancer for maintaining a weight balance with the conventionally used objective lens can be eliminated. Therefore, in the objective lens driving device according to the present invention, since the number of parts is reduced,
The overall size and weight can be reduced, assembling can be easily performed, assembly costs can be reduced, and production efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a plan view of an objective lens driving device to which the present invention is applied.

FIG. 2 is a side view of the objective lens driving device.

FIG. 3 is a sectional view of the objective lens driving device.

FIG. 4 is a diagram for explaining leakage magnetic flux.

FIG. 5 is a perspective view of a neutral iron piece.

FIG. 6 is a diagram illustrating the operation of the objective lens driving device when the neutral iron piece is formed of a rectangular flat plate.

FIG. 7 is a diagram illustrating another example of a method of attaching a focusing coil and a tracking coil.

FIG. 8 is a plan view of a flexible printed wiring board for supplying a driving current to the focusing coil and the tracking coil.

FIG. 9 is a cross-sectional view showing a state where the objective lens is displaced in a direction approaching the optical disc.

FIG. 10 is a cross-sectional view showing a state where the objective lens is displaced in a direction away from the optical disc.

FIG. 11 is a plan view showing a state in which the objective lens is rotated to one side around a support shaft.

FIG. 12 is a plan view showing a state in which the objective lens is turned to the other side around a support shaft.

FIG. 13 is a perspective view illustrating another example of the neutral iron piece.

14 is a plan view of an objective lens driving device using the neutral iron piece shown in FIG.

15 is a sectional view of the objective lens driving device shown in FIG.

FIG. 16 is a perspective view showing still another example of a neutral iron piece.

FIG. 17 is an exploded perspective view illustrating a conventional objective lens driving device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Objective lens drive device, 2 bases, 3 objective lenses, 4 lens holders, 5 support shafts, 6 first magnet mounting pieces, 7 focusing magnets, 8 second magnet mounting pieces, 9 tracking magnets, 11
Cylindrical part, 12 insertion hole, 13 objective lens mounting part, 14
Focusing coil, 15 Neutral iron piece, 16 Tracking coil, 21 Projection, 22 Printed wiring board, 23 Substrate body, 24 First derivation part, 25 Second derivation part, 26 Third derivation part

Claims (4)

[Claims] A base having a support shaft formed in the optical axis direction of the objective lens; and a base provided on the support shaft so as to be slidable in the optical axis direction of the objective lens and in a rotational direction about the support shaft. And a holder for holding the objective lens at one end, at least a pair of first coils provided on one of the base and the holder, and at least a pair of first coils provided on the other of the base and the holder A first drive unit, comprising a first magnet, provided opposite to each other with the support shaft interposed therebetween, and configured to drive the holder in the optical axis direction of the objective lens; and one of the base and the holder And a second magnet provided on the other of the base and the holder. The other end faces the one end holding the objective lens with the support shaft interposed therebetween. An objective lens driving device comprising: a second driving unit provided on an end side and configured to rotate the holder around the support shaft. 2. The objective lens driving device according to claim 1, wherein the weight of the objective lens and the second drive unit are set such that the moments of the objective lens and the second drive unit are balanced about the support shaft. 3. The pair of first coils and / or second coils.
The coil of (1) is supplied with a drive current via a printed wiring board in accordance with a signal from an external circuit, and the printed wiring board is formed so that a movable end side is curved with respect to a fixed end side. The objective lens driving device as described in the above. 4. The objective lens driving device according to claim 3, wherein the printed wiring board is curved in a substantially spiral shape.