JPH09305990A - Optical pickup of optical recorder/reproducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the thrust of the movable part of an optical pickup and reduce the yawing caused by the movement of the movable part. SOLUTION: A movable part (a) is composed of an object lens 1, permanent magnets 4 and an object lens holder 2 by which the object lens 2 and the permanent magnets 4 are held. Yokes 5 are provided so as to have the movable part (a) between them. Focus coils 6 and tracking coils 7 are wound on the yokes 5. Auxiliary yokes 8 made of magnetic material are provided in the neighborhoods of the yokes 5 in order to introduce flux to the outsides of the focus coils 6 and the tracking coils 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup used in an optical recording / reproducing apparatus.

[0002]

2. Description of the Related Art Conventionally, as an optical pickup used in an optical recording / reproducing apparatus, the one described in Japanese Utility Model Laid-Open No. 2-55415 is known. FIG. 16 shows a plan view of a conventional optical pickup, and FIG. 17 shows C in FIG.
A sectional view taken along the line C'is shown.

In these figures, 1 is an objective lens, 2
Is an objective lens holder that holds the objective lens 1, 4 is a permanent magnet disposed on both sides of the objective lens holder 2, and a is a movable part including the objective lens 1, the objective lens holder 2 and the permanent magnet 4. Reference numeral 3 denotes an elastic support member that movably supports the movable portion a, reference numeral 5 denotes a yoke made of a magnetic material that is arranged so as to sandwich the movable portion a and forms a magnetic circuit, and reference numeral 6 denotes the recording medium (for example, the movable portion a). A focus coil wound around a yoke 5 for moving in a focus direction which is a direction perpendicular to an optical disk, and a track 7 wound around a yoke 5 for moving a movable part a in a track direction which is a radial direction of a recording medium. It is a coil.

The operation of the optical pickup configured as described above will be described below.

First, the thrust generated by the permanent magnet 4 is the reaction force of the sum of the electromagnetic force generated by the yoke 5 and the electromagnetic force generated by the focus coil 6 or the track coil 7. As a result, when the movable part a is moved in the focus direction, a predetermined current is passed through the focus coil 6, and when it is moved in the track direction, a predetermined current is passed through the track coil 7, so that each coil is supplied with a predetermined current. An electromagnetic force according to Fleming's left-hand rule and an electromagnetic force due to the imbalance of the magnetic field around the yoke 5 are generated respectively, and the reaction force of the sum of these electromagnetic forces becomes a thrust force to move the movable part a, that is, the optical pickup. Will be moved.

[0006]

In this optical pickup, in order to focus the laser light spot on the optical disk surface, it is required to follow the objective lens with respect to surface wobbling or eccentricity of the optical disk. In that case, Larger thrust is required as the rotation frequency of the disk increases. Further, in order to move the objective lens in a stable manner, it is necessary to reduce the yawing that occurs when the movable part moves.

It is an object of the present invention to improve a magnetic circuit by adding an auxiliary yoke and improve thrust generated in a movable portion. Another object is to reduce the yawing by changing the shape of the yoke or the permanent magnet and to move the objective lens stably.

[0008]

An optical pickup of an optical recording / reproducing apparatus according to the present invention includes an auxiliary member made of a magnetic material for guiding a magnetic flux to the outside of at least one of a focus coil and a track coil near a yoke. The feature is that a yoke is provided. Another feature of the present invention is that another auxiliary yoke, which is independent of the movable portion, is provided in the through hole provided in the objective lens holder. Since the magnetic flux is guided to the outside of the focus coil or the track coil by the auxiliary yoke arranged near the yoke, or the reaction force of the electromagnetic force generated in another auxiliary yoke is applied to the permanent magnet, The imbalance of the magnetic field around the yoke is promoted, the electromagnetic force generated in the yoke and the auxiliary yoke increases, and the thrust generated in the movable portion can be increased even when a constant current is applied. In addition, a focus coil and a track coil are wound around the objective lens holder, a permanent magnet is arranged with the movable portion sandwiched between them, an inner yoke is provided in a through hole provided in the objective lens holder, and an outer yoke is provided outside the permanent magnet. The inner yoke facing the permanent magnet is a curved surface, or
By making the surface of the inner yoke facing the permanent magnet a curved surface, the area with a large magnetic flux density interlinking with the focus coil or track coil is expanded, and the electromagnetic force generated in the coil due to the movement of the movable part is unbalanced. It is possible to suppress and reduce yawing.

[0009]

An optical pickup of an optical recording / reproducing apparatus according to a first aspect of the present invention is provided with an objective lens, an objective lens holder for holding the objective lens, and the objective lens holder. A permanent magnet, an elastic support member for movably supporting a movable portion composed of the objective lens, the objective lens holder, and a permanent magnet, and a yoke that is arranged so as to sandwich the movable portion and forms a magnetic circuit. In an optical pickup of an optical recording / reproducing apparatus including a focus coil and a track coil wound around the yoke, in order to guide a magnetic flux to the outside of at least one of the focus coil and the track coil in the vicinity of the yoke. It is characterized in that an auxiliary yoke made of the magnetic material is disposed. The magnetic flux is guided to the outside of the focus coil or track coil by the auxiliary yoke arranged near the yoke, which promotes the imbalance of the magnetic field around the yoke and the auxiliary yoke, increasing the electromagnetic force generated in the yoke and the auxiliary yoke. However, even when a constant current is applied, the thrust generated in the movable part increases.

An optical pickup for an optical recording / reproducing apparatus according to a second aspect of the present invention is characterized in that, in the first aspect, the auxiliary yoke is integrated with the yoke. The magnetic flux is guided to the outside of the focus coil or the track coil by the auxiliary yoke. However, since the auxiliary yoke is integrated with the yoke, the magnetic flux easily flows toward the auxiliary yoke having a small magnetic resistance, and the yoke and the auxiliary yoke. The unbalance of the magnetic flux around the is further promoted, the electromagnetic force generated in the yoke and the auxiliary yoke is further increased, and the thrust generated in the movable part is further increased even when a constant current is passed.

An optical pickup for an optical recording / reproducing apparatus according to a third aspect of the present invention comprises an objective lens, an objective lens holder for holding the objective lens, and a permanent magnet arranged on the objective lens holder. An elastic support member that movably supports a movable portion composed of the objective lens / objective lens holder and a permanent magnet; a yoke that is disposed so as to sandwich the movable portion to form a magnetic circuit; In an optical pickup of an optical recording / reproducing apparatus including a wound focus coil and a track coil, a through hole is provided between the objective lens of the objective lens holder and the permanent magnet, and the through hole is provided in the through hole. It is characterized in that another auxiliary yoke made of a magnetic material, which is independent of the movable part, is provided. Since the auxiliary yoke arranged near the yoke promotes the imbalance of the magnetic field around the yoke and the auxiliary yoke, an electromagnetic force is generated in another auxiliary yoke and the reaction force is applied to the permanent magnet. The electromagnetic force generated in the yoke and the auxiliary yoke further increases, and the thrust generated in the movable portion further increases even when a constant current is applied.

According to a fourth aspect of the present invention, in the optical pickup of the optical recording / reproducing apparatus according to the third aspect, the shape of the surface of the another auxiliary yoke facing the permanent magnet has the shape of the permanent magnet. It is characterized in that the shape is symmetrical with respect to a plane that passes through substantially the center point and is perpendicular to the focus direction or a plane that passes through the substantially center point of the permanent magnet and is perpendicular to the track direction. Since the shape of another auxiliary yoke is symmetrical with respect to the permanent magnet, it is possible to reduce the generation of unnecessary thrust that causes yawing even when the movable portion moves in the focus direction or the track direction.

According to a fifth aspect of the present invention, in an optical pickup of an optical recording / reproducing apparatus according to the present invention, an objective lens, an objective lens holder for holding the objective lens, a focus coil wound around the objective lens holder, and a track are provided. A coil, an elastic support member that movably supports a movable portion composed of the objective lens, the objective lens holder, a focus coil, and a track coil; a permanent magnet disposed so as to sandwich the movable portion; A through-hole is provided on both outer sides of the objective lens of the objective-lens holder, an inner yoke is provided in the through-hole independently of the movable portion, and an outer yoke is provided outside the permanent magnet. An optical pickup of an optical recording / reproducing apparatus, comprising: an inner yoke and an outer yoke; and a connecting auxiliary yoke arranged to connect the inner yoke and the outer yoke. There in order to reduce the yawing that occurs when moving, is characterized in that the surface facing the permanent magnet of the inner yoke surface. If the surface of the inner yoke that faces the permanent magnet is a flat surface, the area with a large magnetic flux density that links the focus coil or the track coil is narrow, so the electromagnetic force generated in the coil when the movable part moves is The distribution is unbalanced with respect to a plane that passes through the center of gravity of and is perpendicular to the track direction, which causes yawing. On the other hand, as in claim 5, the surface of the inner yoke facing the permanent magnet is a curved surface, so that a region having a high magnetic flux density interlinking with the focus coil or the track coil is expanded. Since the electromagnetic force generated in the coil due to the movement of the movable portion is not imbalanced, yawing can be reduced.

An optical pickup of an optical recording / reproducing apparatus according to a sixth aspect of the present invention is the optical pickup according to the fifth aspect, wherein the permanent magnet of the inner yoke is formed in order to reduce yawing that occurs when the movable portion moves. The surface facing the inner yoke of the permanent magnet is curved instead of the surface facing to the curved surface. Since the surface of the permanent magnet that faces the inner yoke is a curved surface, the area with a high magnetic flux density interlinking with the focus coil or the track coil expands, so that the electromagnetic force generated in the coil by moving the movable part. The imbalance does not occur, and yawing can be reduced.

An optical pickup for an optical recording / reproducing apparatus according to a seventh aspect of the present invention is the optical pickup according to any one of the first to sixth aspects, wherein the yoke and the auxiliary yoke are made of a high resistance material such as ferrite. It is characterized by being. Since the yoke and the auxiliary yoke are made of high resistance material, the eddy current generated in the yoke and the auxiliary yoke due to the temporal change of the magnetic flux is reduced, and the loss of the magnetic energy in the yoke and the auxiliary yoke is reduced, so that the movable The thrust generated in the part a is further increased.

Embodiments of an optical pickup of an optical recording / reproducing apparatus according to the present invention will be described below in detail with reference to the drawings.

[First Embodiment] FIG. 1 is a plan view of an optical pickup of an optical recording / reproducing apparatus according to a first embodiment of the present invention. In FIG. 1, 1 is an objective lens, 2 is an objective lens holder that holds the objective lens 1, 4 is permanent magnets arranged on both sides of the objective lens holder 2, and a is the objective lens 1 and the objective lens holder. A movable part composed of 2 and a permanent magnet 4, 3 is an elastic support for movably supporting the movable part a, 5 is a yoke which is arranged so as to sandwich the movable part a and constitutes a magnetic circuit, and 6 is a movable part. A focus coil wound around the yoke 5 for moving a in a focus direction which is a direction perpendicular to a recording medium (eg, an optical disc), and a yoke 7 for moving the movable portion a in a track direction which is a radial direction of the recording medium. A track coil wound around 5 and an auxiliary yoke 8 arranged near both ends of the yoke 5 and made of a magnetic material for guiding magnetic flux to the outside of the focus coil 6 and the track coil 7.

The operation of the optical pickup configured as described above will be described below.

First, the thrust generated by the permanent magnet 4 is the reaction force of the sum of the electromagnetic force generated by the yoke 5 and the auxiliary yoke 8 and the electromagnetic force generated by the focus coil 6 or the track coil 7. As a result, when the movable portion a including the objective lens 1 is moved in the focus direction which is the vertical direction with respect to the recording medium, a predetermined current is applied to the focus coil 6 to move the movable portion a in the track direction which is the radial direction of the recording medium. When moving the track coil, a predetermined current is applied to the track coil 7 so that an electromagnetic force according to Fleming's left-hand rule is applied to each coil, and the yoke 5 and the auxiliary yoke 8 are affected by the imbalance of the surrounding magnetic field. Electromagnetic forces are generated, respectively, and the reaction force of the sum of these electromagnetic forces becomes thrust, and the movable part a, that is, the optical pickup moves.
In this case, the focus coil 6 and the track coil 7 are provided by the auxiliary yokes 8 arranged near both ends of the yoke 5.
Since the magnetic flux is guided to the outside of the magnet, the imbalance of the magnetic field around the yoke 5 and the auxiliary yoke 8 is promoted, the electromagnetic force generated in the yoke 5 and the auxiliary yoke 8 increases, and even when a constant current is applied, the permanent magnet 4, that is, the thrust generated in the movable portion a is increased.

In the above description, the thrust acting on the movable part is increased when a constant current is applied. However, a smaller current is required to obtain a predetermined thrust, and therefore, light consumption of light is low. It can also be implemented for pickups.

[Second Embodiment] FIG. 2 is a plan view of an optical pickup of an optical recording / reproducing apparatus according to a second embodiment.
FIG. 4 is a perspective view of a yoke and an auxiliary yoke. In FIG. 2, 1 is an objective lens, 2 is an objective lens holder that holds the objective lens 1, 4 is permanent magnets arranged on both sides of the objective lens holder 2, and a is the objective lens 1 and the objective lens holder. A movable part composed of 2 and a permanent magnet 4, 3 is an elastic support for movably supporting the movable part a, 5 is a yoke arranged so as to sandwich the movable part a to form a magnetic circuit, and 6 is a yoke 5. Is a focus coil wound on the yoke 5, 7 is a track coil wound on the yoke 5, and 8 is an auxiliary yoke which is integrated with the yoke 5 and is made of a magnetic material for guiding magnetic flux to the outside of the focus coil 6 and the track coil 7. . The difference from FIG. 1 is that the auxiliary yoke 8 has a yoke 5 as shown in FIG.
It is integrated with. That is, the auxiliary yokes 8 are integrated into the upper and lower end surfaces of the yoke 5, respectively, at four positions on the left and right ends.

The operation of the optical pickup configured as described above will be described below.

First, the thrust generated by the permanent magnet 4 is the reaction force of the sum of the electromagnetic force generated by the yoke 5 and the auxiliary yoke 8 and the electromagnetic force generated by the focus coil 6 or the track coil 7. As a result, when the movable part a including the objective lens 1 is moved in the focus direction, a predetermined current is applied to the focus coil 6, and when it is moved in the track direction, a predetermined current is applied to the track coil 7. An electromagnetic force according to Fleming's left-hand rule is generated in each coil, and an electromagnetic force is generated in the yoke 5 and the auxiliary yoke 8 due to the imbalance of the surrounding magnetic field. Then, the movable part a, that is, the optical pickup is moved. In this case, the magnetic flux is guided to the outside of the focus coil 6 and the track coil 7 by the auxiliary yoke 8. However, since the auxiliary yoke 8 is integrated with the yoke 5, the magnetic flux is smaller in the magnetic resistance of the auxiliary yoke 8. Flow more easily, the imbalance of the magnetic flux around the yoke 5 and the auxiliary yoke 8 is further promoted, the electromagnetic force generated in the yoke 5 and the auxiliary yoke 8 increases, and even if a constant current is applied, the permanent magnet 4, that is, the movable portion. a
The thrust force generated in is further increased.

In the above description, the thrust acting on the movable part is increased when a constant current is passed. However, a smaller current is required to obtain a predetermined thrust, and therefore light with low power consumption is used. It can also be implemented for pickups.

[Third Embodiment] FIG. 4 is a plan view of an optical pickup of an optical recording / reproducing apparatus according to a third embodiment.
FIG. 5 is a sectional view taken along the line AA ′ in FIG. FIG.
In FIG. 5, 1 is an objective lens, 2 is an objective lens holder that holds the objective lens 1, 4 is permanent magnets arranged on both sides of the objective lens holder 2, and b is the objective lens 1 and the objective lens holder. 2 is a movable part including the permanent magnet 4, 3 is an elastic support that movably supports the movable part b, 5 is a yoke that is arranged so as to sandwich the movable part b and forms a magnetic circuit,
6 is a focus coil wound around the yoke 5, 7 is a track coil wound around the yoke 5, 8 is disposed near both ends of the yoke 5, and the focus coil 6 and the track coil 7 are provided.
2a is a through-hole formed between the objective lens 1 and the permanent magnet 4 in the objective-lens holder 2 and 8'is a through-hole 2
It is another auxiliary yoke made of a magnetic material, which is disposed in a and is independent of the movable portion b. What is different from FIG. 1 is that another auxiliary yoke 8'inserted in the through hole 2a of the objective lens holder 2 is added.

The operation of the optical pickup configured as described above will be described below.

First, the thrust generated in the permanent magnet 4 is a reaction force of the sum of the electromagnetic force generated in the yoke 5 and the auxiliary yokes 8 and 8'and the electromagnetic force generated in the focus coil 6 or the track coil 7. As a result, when the movable portion b including the objective lens 1 is moved in the focus direction, a predetermined current is passed through the focus coil 6, and when it is moved in the track direction, a predetermined current is passed through the track coil 7. An electromagnetic force according to Fleming's left-hand rule is generated in each coil, and an electromagnetic force is generated in the yoke 5 and the auxiliary yokes 8 and 8 ′ due to the imbalance of the magnetic field around them, and the reaction force of the sum of these electromagnetic forces is generated. Becomes thrust, and the movable part b, that is, the optical pickup moves. In this case, the auxiliary yokes 8 arranged near both ends of the yoke 5
As a result, the magnetic flux is guided to the outside of the focus coil 6 and the track coil 7, so that the imbalance of the magnetic flux around the yoke 5 and the auxiliary yoke 8 is promoted, and the yoke 5
And the electromagnetic force generated in the auxiliary yoke 8 increases,
An electromagnetic force is also generated in another auxiliary yoke 8 ', and the reaction force is applied to the permanent magnet 4, so that the thrust generated in the permanent magnet 4, that is, the movable portion b is further increased even when a constant current is applied.

In the above description, the thrust acting on the movable part is increased when a constant current is applied. However, a smaller current is required to obtain a predetermined thrust, and therefore light with low power consumption is used. It can also be implemented for pickups.

[Fourth Embodiment] FIG. 6 is a plan view of an optical pickup of an optical recording / reproducing apparatus according to a fourth embodiment. In FIG. 6, 1 is an objective lens and 2 is an objective lens 1.
Objective lens holder 4 for holding the objective lens holder 4
Permanent magnets disposed on both sides of the movable part, b is a movable part composed of the objective lens 1 / objective lens holder 2 and the permanent magnet 4, 3 is an elastic support for movably supporting the movable part b, and 5 is an elastic support. A yoke which is disposed so as to sandwich the movable portion b and constitutes a magnetic circuit, 6 is a focus coil wound around the yoke 5, 7 is a track coil wound around the yoke 5, and 8 is disposed near both ends of the yoke 5. , An auxiliary yoke 2a made of a magnetic material for guiding a magnetic flux to the outside of the focus coil 6 and the track coil 7, a through hole 8a formed between the objective lens 1 and the permanent magnet 4 in the objective lens holder 2. Is another auxiliary yoke made of a magnetic material and arranged in the through hole 2a independently of the movable portion b. The difference from FIG. 4 is that
The shape of the surface of another auxiliary yoke 8 ′ facing the permanent magnet 4 is a surface perpendicular to the focus direction passing through substantially the center point of the permanent magnet 4 or a surface perpendicular to the track direction passing through the substantially center point of the permanent magnet 4. It is symmetric with respect to the plane.

The operation of the optical pickup configured as described above will be described below.

First, the thrust generated by the permanent magnet 4 is a reaction force of the sum of the electromagnetic force generated by the yoke 5 and the auxiliary yokes 8 and 8'and the electromagnetic force generated by the focus coil 6 or the track coil 7. As a result, when the movable portion b including the objective lens 1 is moved in the focus direction, a predetermined current is passed through the focus coil 6, and when it is moved in the track direction, a predetermined current is passed through the track coil 7. An electromagnetic force according to Fleming's left-hand rule is generated in each coil, and an electromagnetic force due to an unbalanced magnetic field is generated in the yoke 5 and the auxiliary yokes 8 and 8 ', and the reaction force of the sum of these electromagnetic forces is the thrust. Then, the movable part b, that is, the optical pickup is moved. In this case, by the auxiliary yokes 8 arranged near both ends of the yoke 5,
Since the magnetic flux is guided to the outside of the focus coil 6 and the track coil 7, unbalance of the magnetic field around the yoke 5 and the auxiliary yoke 8 is promoted, the electromagnetic force generated in the yoke 5 and the auxiliary yoke 8 increases, and another Since an electromagnetic force is also generated in the auxiliary yoke 8'and a reaction force thereof is applied to the permanent magnet 4, the thrust generated in the permanent magnet 4, that is, the movable portion b is further increased even when a constant current is applied. Further, the shape of the surface of the auxiliary yoke 8 ′ facing the permanent magnet 4 is a surface that passes through substantially the center point of the permanent magnet 4 and is perpendicular to the focusing direction, or a shape that passes through the substantially center point of the permanent magnet 4 and is perpendicular to the track direction. Since it is symmetrical with respect to the plane, it is possible to reduce the generation of unnecessary thrust that causes yawing even when the movable portion b moves in the focus direction or the track direction.

[Fifth Embodiment] FIG. 7 is a plan view of an optical pickup of an optical recording / reproducing apparatus according to a fifth embodiment.
Is a sectional view taken along the line BB 'in FIG. 7, and FIG. 9 is a perspective view of the inner yoke.

In FIGS. 7 and 8, 1 is an objective lens, and 2 is
Is an objective lens holder that holds the objective lens 1, 6 is a focus coil wound around the objective lens holder 2, 7 is a track coil wound around the objective lens holder 2 outside the focus coil 6, and c is the objective lens 1. A movable part composed of an objective lens holder 2, a focus coil 6 and a track coil 7, 3 is an elastic support for movably supporting the movable part c, and 4 is arranged so as to sandwich the movable part c. Permanent magnets 2a are through-holes formed on both outer sides of the objective lens 1 in the objective-lens holder 2 and 5'inner yokes 5 "are provided inside the through-holes 2a independent of the movable part c. An outer yoke, 8 ″, disposed on the outer side of each of the permanent magnets 4, is an auxiliary yoke for connection, which is disposed so as to connect the inner yoke 5 ′ and the outer yoke 5 ″ at their bottom surfaces. 7 and shown in FIG. As such, in order to reduce the yawing generated when the movable portion c to move, the side facing the permanent magnet 4 in the inner yoke 5 'is constituted by a convex curved surface.

The operation of the optical pickup configured as described above will be described below.

First, since the magnetic flux generated in the permanent magnet 4 is linked to the focus coil 6 or the track coil 7, when moving the movable portion c including the objective lens 1 in the focus direction, the magnetic flux is generated in the focus coil 6. When a predetermined current is passed and the track coil 7 is moved in the track direction, a predetermined current is passed through the track coil 7, whereby an electromagnetic force according to Fleming's left-hand rule is generated in each coil, whereby the movable part c, that is, the optical pickup. Will be moved.

In this case, if the surface of the inner yoke 5'facing the permanent magnet 4 is a plane, the distribution of the magnetic flux interlinking with the focus coil 6 or the track coil 7 is as shown in FIG. Since the large area is large, the electromagnetic force generated in the coil due to the movement of the movable part c has an unbalanced distribution with respect to a plane that passes through substantially the center of gravity of the coil and is perpendicular to the track direction, which causes yawing.

On the other hand, in the optical pickups of FIGS. 7 and 8, since the surface of the inner yoke 5'facing the permanent magnet 4 is a convex curved surface as shown in FIG. The magnetic flux interlinking with 7 has a distribution as shown in FIG. 11 at the portion facing the permanent magnet 4, and the fluctuation of the magnetic flux density depending on the position becomes small. Can be reduced and yawing can be reduced.

[Sixth Embodiment] FIG. 12 is a plan view of an optical pickup of an optical recording / reproducing apparatus according to a sixth embodiment, and FIG. 13 is a perspective view of a permanent magnet in FIG. In FIG. 12, 1 is an objective lens, 2 is an objective lens holder that holds the objective lens 1, 6 is a focus coil wound around the objective lens holder 2, and 7 is outside the focus coil 6 and attached to the objective lens holder 2. A wound track coil, c is a movable part composed of the objective lens 1, the objective lens holder 2, the focus coil 6 and the track coil 7, 3 is an elastic support for movably supporting the movable part c, and 4 is movable. The permanent magnets 2a are arranged so as to sandwich the portion c, and the objective lens holder 2 is provided.
Through holes formed on both outer sides of the objective lens 1,
Reference numeral 5'denotes an inner yoke arranged in the through hole 2a independently of the movable portion c, 5 "an outer yoke arranged outside each permanent magnet 4, and 8" an inner yoke 5 '. It is an auxiliary yoke for connection arranged so that the outer yokes 5 ″ are connected to each other on their bottom surfaces. As shown in FIGS. 12 and 13, in order to reduce the yawing that occurs when the movable portion c moves, The surface of the permanent magnet 4 facing the inner yoke 5'is formed of a concave curved surface.

The operation of the optical pickup configured as described above will be described below.

First, since the magnetic flux generated in the permanent magnet 4 is linked to the focus coil 6 or the track coil 7, when moving the movable portion c including the objective lens 1 in the focus direction, the magnetic flux is generated in the focus coil 6. When a predetermined current is passed and the track coil 7 is moved in the track direction, a predetermined current is passed through the track coil 7, whereby an electromagnetic force according to Fleming's left-hand rule is generated in each coil, whereby the movable part c, that is, the optical pickup. Will be moved.

In this case, if the surface of the permanent magnet 4 facing the inner yoke 5'is a plane, the distribution of the magnetic flux linked to the focus coil or the track coil is as shown in FIG.
Since the area where the magnetic flux density is large is narrow, the electromagnetic force generated in the coil due to the movement of the movable portion c has an unbalanced distribution with respect to a plane that passes through the center of gravity of the coil and is perpendicular to the track direction. This causes yawing.

On the other hand, in the optical pickup of FIG. 12, since the surface of the permanent magnet 4 facing the inner yoke 5'is a concave curved surface as shown in FIG. 13, the focus coil 6 or the track coil 7 is chained. The intersecting magnetic flux has a distribution as shown in FIG. 14 in the portion facing the inner yoke 5 ', and the fluctuation of the magnetic flux density depending on the position is small, so that the imbalance of the electromagnetic force generated in the coil due to the movement of the movable portion c is caused. Can be reduced and yawing can be reduced.

[Seventh Embodiment] FIG. 15 is a plan view of an optical pickup of an optical recording / reproducing apparatus according to a seventh embodiment. In FIG. 15, 1 is an objective lens, 2 is an objective lens holder that holds the objective lens 1, 4 is permanent magnets arranged on both sides of the objective lens holder 2, and a is the objective lens 1.
Movable part consisting of objective lens holder 2 and permanent magnet 4
Is an elastic support 5 for movably supporting the movable part a.
Is a yoke which is arranged so as to sandwich the movable part a and constitutes a magnetic circuit, 6 is a focus coil wound around the yoke 5, 7 is a track coil wound around the yoke 5, and 8 is arranged near both ends of the yoke 5. The auxiliary yoke is made of a magnetic material for guiding the magnetic flux to the outside of the focus coil 6 and the track coil 7. The feature of the optical pickup of the seventh embodiment is that the yoke 5 and the auxiliary yoke 8 are made of a high resistance material such as ferrite.

The operation of the optical pickup configured as described above will be described below.

First, the thrust generated by the permanent magnet 4 is the reaction force of the sum of the electromagnetic force generated by the yoke 5 and the auxiliary yoke 8 and the electromagnetic force generated by the focus coil 6 or the track coil 7. From this, when moving the movable part a including the objective lens 1 in the focus direction, the focus coil 6
When a predetermined current is applied to the track coil 7 and the track coil 7 is moved in the track direction, a predetermined current is applied to the track coil 7 so that an electromagnetic force according to Fleming's left-hand rule is applied to each coil and to the yoke 5 and the auxiliary yoke 8. An electromagnetic force is generated due to the imbalance of the magnetic field around it, and the reaction force of the sum of these electromagnetic forces becomes a thrust to move the movable part a, that is, the optical pickup.

In this case, since the yoke 5 and the auxiliary yoke 8 are made of a high resistance material, the eddy current generated in the yoke 5 and the auxiliary yoke 8 due to the temporal change of the magnetic flux is reduced, and the magnetism in the yoke 5 and the auxiliary yoke 8 is reduced. Energy loss will be reduced.

[0047]

According to the optical pickup of the optical recording / reproducing apparatus of the present invention, the auxiliary yoke made of a magnetic material for guiding the magnetic flux to the outside of the focus coil or the track coil is provided, or the objective lens is held. By disposing another auxiliary yoke that is independent of the movable part in the through hole of the body, the imbalance of the magnetic field around the yoke and the auxiliary yoke is promoted, and the electromagnetic force generated in the yoke and the auxiliary yoke increases and becomes constant. Even when a current of 3 is applied, the thrust generated in the movable part can be increased. In addition, a focus coil and a track coil are wound around the objective lens holder, permanent magnets are arranged across the movable part, an inner yoke is arranged in the through hole of the objective lens holder, and an outer yoke is arranged outside the permanent magnet. However, by making the surface of the inner yoke facing the permanent magnet a curved surface, or by making the surface of the inner yoke facing the permanent magnet a curved surface, the fluctuation of the magnetic flux density linked to the focus coil or the track coil is small. Expand the area,
The imbalance of the electromagnetic force generated in the coil due to the movement of the movable portion can be suppressed, and yawing can be reduced. In the above description, instead of flowing a constant current to increase the thrust acting on the movable portion, it is possible to realize an optical pickup with low power consumption that requires less current to obtain a predetermined thrust. .

[Brief description of drawings]

FIG. 1 is a plan view showing an optical pickup of an optical recording / reproducing apparatus according to a first embodiment of the present invention.

FIG. 2 is a plan view showing an optical pickup of an optical recording / reproducing apparatus according to a second embodiment of the present invention.

FIG. 3 is a perspective view showing a yoke and an auxiliary yoke in the second embodiment.

FIG. 4 is a plan view showing an optical pickup of an optical recording / reproducing apparatus according to a third embodiment of the present invention.

5 is a cross-sectional view taken along the line AA ′ in FIG.

FIG. 6 is a plan view showing an optical pickup of an optical recording / reproducing apparatus according to a fourth embodiment of the present invention.

FIG. 7 is a plan view showing an optical pickup of an optical recording / reproducing apparatus according to a fifth embodiment of the present invention.

8 is a cross-sectional view taken along the line BB ′ in FIG.

9 is a perspective view showing an inner yoke in FIG. 7. FIG.

FIG. 10 is a diagram showing a magnetic flux distribution interlinking with the focus coil or the track coil when the shape of the surface of the inner yoke facing the permanent magnet is a flat surface.

11 is a diagram showing a magnetic flux distribution interlinking with a focus coil or a track coil in the optical pickup of FIG.

FIG. 12 is a plan view showing an optical pickup of an optical recording / reproducing apparatus according to a sixth embodiment of the present invention.

13 is a perspective view showing a permanent magnet in FIG.

14 is a diagram showing a magnetic flux distribution interlinking with a focus coil or a track coil in the optical pickup of FIG.

FIG. 15 is a plan view showing an optical pickup of an optical recording / reproducing apparatus according to a seventh embodiment of the present invention.

FIG. 16 is a plan view showing an optical pickup of a conventional optical recording / reproducing apparatus.

17 is a cross-sectional view taken along the line CC ′ of FIG.

[Explanation of symbols] a, b, c ... movable part 1 ... objective lens 2 ... objective lens holder 2a ... through hole 3 ... elastic support 4 ... permanent magnet 4a ... curved surface of permanent magnet 5 ... Yoke 5 '... Inner yoke 5 "... Outer yoke 5a ... Inner yoke curved surface 6 ... Focus coil 7 ... Track coil 8 ... Auxiliary yoke 8' ... Another auxiliary yoke 8" ... Auxiliary yoke for connection

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Susumu Iwata 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Within

Claims (7)

[Claims] 1. An objective lens, an objective lens holder for holding the objective lens, a permanent magnet disposed on the objective lens holder, and a movable part including the objective lens / objective lens holder and a permanent magnet. An optical recording / reproducing device that includes an elastic support member that movably supports the magnet, a yoke that is disposed so as to sandwich the movable portion to form a magnetic circuit, and a focus coil and a track coil that are wound around the yoke. In the optical pickup of the apparatus, an optical recording / reproducing device is provided, in the vicinity of the yoke, an auxiliary yoke made of a magnetic material for guiding a magnetic flux to the outside of at least one of the focus coil and the track coil. Optical pickup of the device. 2. The optical pickup for an optical recording / reproducing apparatus according to claim 1, wherein the auxiliary yoke is integrated with the yoke. 3. An objective lens, an objective lens holder that holds the objective lens, a permanent magnet that is disposed on the objective lens holder, and a movable unit that includes the objective lens / objective lens holder and a permanent magnet. An optical recording / reproducing device that includes an elastic support member that movably supports the magnet, a yoke that is disposed so as to sandwich the movable portion to form a magnetic circuit, and a focus coil and a track coil that are wound around the yoke. In the optical pickup of the device, a through hole is provided between the objective lens of the objective lens holder and the permanent magnet, and another auxiliary yoke made of a magnetic material independent of the movable part is provided in the through hole. An optical pickup for an optical recording / reproducing device characterized by the above. 4. The shape of the surface of the other auxiliary yoke facing the permanent magnet has a track passing through substantially the center point of the permanent magnet and perpendicular to the focus direction or a track passing through the substantially center point of the permanent magnet. The optical pickup of an optical recording / reproducing apparatus according to claim 3, wherein the optical pickup has a shape symmetrical with respect to a plane perpendicular to the direction. 5. An objective lens, an objective lens holder for holding the objective lens, a focus coil and a track coil wound around the objective lens holder, the objective lens, the objective lens holder, a focus coil and a track. An elastic support member that movably supports a movable portion formed of a coil, a permanent magnet that is arranged so as to sandwich the movable portion, and through holes are provided on both outer sides of the objective lens of the objective lens holder. An inner yoke arranged independently of the movable portion in the through hole, an outer yoke arranged outside the permanent magnet, and arranged so as to connect the inner yoke and the outer yoke. In an optical pickup of an optical recording / reproducing device having an auxiliary yoke for connection,
An optical pickup for an optical recording / reproducing apparatus, wherein a surface of the inner yoke facing the permanent magnet is a curved surface in order to reduce yawing that occurs when the movable portion moves. 6. The inner yoke of the permanent magnet is replaced with a curved surface on a surface of the inner yoke facing the permanent magnet in order to reduce yawing that occurs when the movable portion moves. 6. The optical pickup for an optical recording / reproducing apparatus according to claim 5, wherein the surface facing the is a curved surface. 7. The optical pickup of an optical recording / reproducing apparatus according to claim 1, wherein the yoke and the auxiliary yoke are made of a high resistance material such as ferrite. .