JPH1027361A - Objective lens drive unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a good driving efficiency by forming a lens holder from a ferromagnetic material, magnetizing it, improving precision in dimensions, and reducing an air gap length. SOLUTION: A whole of a lens holder 2 is formed from a ferromagnetic material, and its magnetization is made to be in a direction parallel to a disk and also in a direction of an axis vertical to a tracking direction, and one is N-pole and the other is S-pole. Coils are confronted with each other with the lens holder 2 confronted in-between, and by making a current flow through focus coils 7a, 7b, the lens holder 2 is driven in the focus direction 15 in which the lens holder 2 is in the direction of the vertical axis to the disk surface, and by making a current flow through tracking coils 8a, 8b, the lens holder is driven in the tracking direction 16, the axis direction parallel to the disk surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device used in an optical disc recording / reproducing apparatus for irradiating a disc with laser light to record / reproduce the disc.

[0002]

2. Description of the Related Art In recent years, a moving coil type in which a driving coil is directly wound around a holder for holding an objective lens has been predominantly used as an objective lens driving device in order to reduce production costs.

[0003] With an increase in the reproduction speed, the driving of the objective lens must be accelerated. For this reason, it is necessary to supply a large current to the drive coil. However, the large current increases the heat generated by the drive coil. The heat causes distortion in the objective lens itself, causing an error in signal reading.

[0004] Therefore, in the moving coil type, the limit to increase the speed has been reduced. To solve this problem, there is a moving magnet type objective lens driving device.

FIG. 3 shows a moving magnet type objective lens driving device. In FIG. 3, 31 is an objective lens,
Reference numeral 32 denotes a rectangular parallelepiped holder for holding the objective lens 31, which is formed of a liquid crystal polymer. Two magnets 33a, 33b magnetized in the thickness direction about the axis parallel to the disk and on both sides of the objective lens 31 are adhesively fixed to the lens holder 32.

At this time, one of the magnets 33a and 33b has an N pole and the other has an S pole in the direction of the center of the lens. Actuator base 4 as fixed side
0, the substrate 36 with the suspension holder 41 interposed therebetween.
End 36a is attached with a screw 44. The lens holder 32 is provided with four metal wire springs 34 at an end 36a of a substrate 36 fixed to the actuator base 40 side.
a, 34b, 34c, and 34d are connected and supported.

More specifically, the tips of the metal wire springs 34a and 34b are fixed to the upper and lower portions of a small piece 35a fixed to the lens holder 32 by soldering, and the tips of the metal wire springs 34c and 34d are fixed to the lens holder 32. It is fixed by soldering above and below the small piece 35b.

The other ends of 34a and 34b pass through the suspension holder 41 and are fixed to the substrate 36 by soldering. As a result, the cantilevered lens holder 32 moves in two directions, a focusing direction 45 and a tracking direction 46. Will be possible.

Reference numerals 39a and 39b denote coil bobbins, in which an iron metal piece serving as a yoke is insert-molded inside, and focus coils 38a and 38b wound around an axis perpendicular to the disk surface and a disk bobbin. The tracking coil 37a wound around an axis parallel to the
37b, the tracking coils 37a and 37b are fixed vertically to the actuator base 40, respectively.
b and the focus coils 38a and 38b are connected to the substrate 36 by soldering through the actuator base 40.

When the magnets 33a and 33b and the tracking coils 37a and 37b are opposed to each other, the movable portion including the objective lens 31 and the lens holder 32 can be moved in a focus direction 4 perpendicular to the disk.
5 and tracking direction 4 parallel to the disk
6 can be driven in two directions.

[0011]

However, the conventional objective lens driving device as described above has a magnet 33a,
Since 33b is fixedly adhered to the lens holder 32, the dimension between the outer surfaces of the magnets 33a and 33b is not stable, and therefore, a large space gap between the magnet 33a and the drive coil is required.

Further, when the space gap is made large, there is a problem that the driving efficiency is reduced. Further, the conventional apparatus has a problem that the number of parts is large and the production cost is high.

[0013]

In order to solve this problem, an objective lens driving device according to the present invention comprises a lens holder made of a ferromagnetic material and magnetized.

According to the present invention, it is possible to improve the dimensional accuracy, to reduce the space gap, and to obtain an objective lens driving device with good driving efficiency.

[0015]

According to a first aspect of the present invention, there is provided an objective lens driving device in which a lens holder for holding an objective lens is supported by a metal spring, and a coil bobbin having a yoke opposed to the lens holder is mounted on a base as a fixed member. Assembly,
A moving magnet type objective lens driving device for energizing a coil wound around a coil bobbin and swinging the lens holder in a focusing direction and a tracking direction by an attraction and repulsion action with a magnetized state on the lens holder side, The lens holder is formed of a ferromagnetic material and is magnetized, and the lens holder can be driven by the attraction and repulsion of the coil without the need to fix and fix a separate magnet to the lens holder.

According to a second aspect of the present invention, in the objective lens driving device according to the first aspect, a part of the lens holder is formed of a ferromagnetic material and magnetized. According to a third aspect of the present invention, in the objective lens driving device according to the first or second aspect, a part or all of the lens holder is formed of a molded magnet and magnetized.

According to a fourth aspect of the present invention, there is provided an objective lens driving device, an objective lens, a lens holder for holding the objective lens, a base portion having a surface parallel to the disk, and a projection on the base toward the disk. A yoke arranged so as to be opposed to both sides adjacent to the lens holder and perpendicular to the disc, and a focus coil wound outside the yoke in an axial direction perpendicular to the disc,
The tracking coil wound in the axial direction parallel to the disk enables the lens holder to be driven in two directions, a focus direction perpendicular to the disk and a tracking direction parallel to the disk. ,
The lens holder is formed of a molded magnet.

According to a fifth aspect of the present invention, in the objective lens driving device according to the fourth aspect, a small projection is provided on each of the corners of the yoke on a surface of the lens holder opposed to the yoke, and the lens holder is perpendicular to the yoke. , And are positioned both in the horizontal direction.

An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a configuration of an objective lens driving device according to a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes an objective lens, and 2 denotes a rectangular parallelepiped lens holder for holding the objective lens 1. This lens holder 2 is entirely formed of a ferromagnetic material. The magnetization direction is an axial direction parallel to the disk and perpendicular to the tracking direction, one of which is an N pole and the other is an S pole.

More specifically, the entire lens holder 2 is formed by injection molding a synthetic resin in which ferromagnetic powder is dispersed and mixed. An end 5 a of the substrate 5 is attached to the actuator base 10 as a fixed side with a screw 11 across the suspension holder 9. The lens holder 2 is supported by being connected to the end 5a of the substrate 5 fixed to the actuator base 40 via four metal wire springs 4a, 4b, 4c, 4d.

More specifically, the tips of the metal wire springs 4a and 4b are fixed to the upper and lower portions of the small piece 3a fixed to the lens holder 2 by soldering, and the tips of the metal wire springs 4c and 4d are fixed to the lens holder 2. It is fixed by soldering above and below the small piece 35b.

The other ends of 4a and 4b penetrate suspension holder 9 and are fixed to substrate 5 by soldering.
The cantilevered lens holder 2 is movable in two directions, a focus direction 15 and a tracking direction 16.

The actuator base 10 has a base portion 10a having a surface parallel to the disk, and bobbin holding portions 10b, 10b projecting from the base portion 10a toward the disk and perpendicular to the disk.
c and 10d are integrally formed. Reference numerals 6a and 6b denote coil bobbins, in each of which an iron metal piece serving as a yoke is installed by insert molding. The coil bobbin 6a has a focus coil 7a wound around an axis perpendicular to the disk surface and a tracking coil 8a wound around an axis parallel to the disk surface,
Similarly, the coil bobbin 6b has a focus coil 7b wound around an axis perpendicular to the disk surface and a tracking coil 8b wound around an axis parallel to the disk surface.

The coil bobbins 6a, 6b are vertically bonded and fixed to the actuator base 10, respectively, and the focus coils 7a, 7b and the tracking coils 8a,
8b is connected to the substrate 5 by soldering, and the tracking coil 7a and the tracking coil 7b are connected to the substrate 5 by soldering.
, And the focus coil 8a and the focus coil 8b are similarly connected in series by the substrate 5, so that the current can be supplied from the substrate 5 to each coil independently.

The magnetized lens holder 2
The lens holder 2 is driven in the focus direction 15, which is an axial direction perpendicular to the disk surface, by passing a current through the focus coils 7a and 7b. Driving in the tracking direction 16 which is an axial direction parallel to the disk surface by flowing a current.

As described above, since the lens holder 2 is formed of a ferromagnetic material and magnetized, the dimensional accuracy can be improved as compared with the conventional case where a separate magnet is adhered and fixed to the lens holder 2. This eliminates the need to increase the space gap between each coil as in the conventional example, and enables efficient driving.

Since the lens holder 2 has a larger volume than the conventional moving magnet type magnets 33a and 33b, it goes without saying that the driving efficiency is further improved. In addition, since the above-mentioned bonding step is unnecessary, the production cost can be reduced.

FIGS. 2A and 2B show the sectional shapes of the lens holder 2 and the yoke 12 insert-molded on the coil bobbins 6a and 6b. The focus coils 7a and 7b, the tracking coils 8a and 8b, and The metal wire springs 4a to 4d are omitted.

On the surface of the lens holder 2 facing the yoke 12, small projections 13a to 13d are formed integrally with small projections 12a to 12d formed at the corners of the yoke 12, and the corners of the yoke 12 are formed. The small projections 13e to 13h are formed integrally with the small projections 12e to 12h.

In the coil holder 6a around which the focus coil 7a and the tracking coil 8a are wound, the small projections 12a to 12d are hidden by the coils and cannot be seen.
Similarly, the small protrusions 12e to 12h on the coil holder 6b are hidden by the wound focus coil 7b and tracking coil 8b and are invisible.

As described above, the small projection 1 is attached to the lens holder 2.
By providing the small protrusions 3a to 13h and the small protrusions 12a to 12h at the corners of the opposing yoke 12, to reduce the space gap, the driving efficiency can be further improved.

When no current is applied to the coil, the lens holder 2 is positioned at a magnetically neutral position in both the vertical and horizontal directions with respect to the yokes 12a and 12b by utilizing the minimum magnetic circuit. it can.

In the above embodiment, the entire lens holder 2 is formed of a magnetic molding material. However, only the necessary portions are formed of the magnetic molding material, and the other portions are formed of a normal molding material to form two materials. Needless to say, the lens holder 2 can be made.

[0035]

As described above, according to the present invention, since the lens holder is formed of a ferromagnetic material and magnetized,
While maintaining the advantages of the moving magnet type suitable for high-speed driving, the driving efficiency can be increased, and the production cost can be reduced because the bonding step is not required.

When small projections are provided at the corners of the yoke on the surface of the lens holder facing the yoke, the lens holder is positioned vertically and horizontally relative to the yoke. It can be positioned at the neutral position.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an objective lens driving device according to an embodiment of the present invention.

FIG. 2 is a plan view and a side view showing a relationship between a lens holder and a coil bobbin according to the embodiment.

FIG. 3 is an exploded perspective view of a conventional objective lens driving device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Objective lens 2 Lens holder 3 Small piece 4a-4d Metal wire spring 5 Substrate 6a, 6b Coil bobbin 7a, 7b Tracking coil 8a, 8b Focus coil 9 Suspension holder 10 Actuator base 11 Screw 12 Yoke 12a-12h Formed at the corner of yoke Small projections 13a to 13h Small projections formed on lens holder

Claims (5)

[Claims] 1. A lens holder for holding an objective lens is supported by a metal spring, a coil bobbin having a yoke opposed to the lens holder is assembled to a base which is a fixed member, and a coil wound around the coil bobbin is energized to energize the coil. What is claimed is: 1. A moving magnet type objective lens driving device for driving a lens holder in a focusing direction and a tracking direction by an attraction and repulsion action with a magnetized state of a lens holder, wherein the lens holder is formed of a ferromagnetic material and magnetized. Objective lens driving device. 2. The objective lens driving device according to claim 1, wherein a part of the lens holder is formed of a ferromagnetic material and magnetized. 3. The lens holder according to claim 1, wherein a part or the whole of the lens holder is formed of a molded magnet and magnetized.
An objective lens driving device according to claim 1. 4. An objective lens, a lens holder for holding the objective lens, a base portion having a surface parallel to the disc, and a projection on the base toward the disc side and perpendicular to the disc. A yoke arranged adjacent to the lens holder on both sides so as to face each other, a focus coil wound outside of the yoke in an axial direction perpendicular to the disc, and a focus coil wound in an axial direction parallel to the disc With the tracking coil, the lens holder can be driven in two directions, a focus direction perpendicular to the disk and a tracking direction parallel to the disk, and the lens holder is formed of a molded magnet. Characteristic objective lens driving device. 5. The lens holder according to claim 1, wherein a small projection is provided on each of the corners of the yoke on a surface of the lens holder facing the yoke, and the lens holder is positioned both vertically and horizontally with respect to the yoke. 5. The objective lens driving device according to 4.