JPH06267143A - Objective lens and objective lens driving device for magneto-optical recording - Google Patents

Abstract

PURPOSE:To suppress the positional change of the center of gravity of a movable part to a small amount, to favorably balance the part, to miniaturize a magnetic field applying coil and to improve the rigidity by embedding the magnetic field applying coil in the outer peripheral part of a lens part. CONSTITUTION:An objective lens 2 is manufactured by molding and a cell part 2a and a magnetic field applying coil 14 are integrally composed by embedding the magnetic field applying coil 14 in the cell part 2a at the time of molding. A laser beam is converged by a lens part 2b, forms a light spot on the surface of an optical disk, a current is supplied to the magnetic field applying coil 14 through an electrode 15, the magnetic field is generated and information recording is performed by applying the magnetic field on the position of the light spot. In such a case, since the magnetic field applying coil 14 is comparatively miniaturized, the weight of a bobbin does not increase and the position of the center of gravity of the bobbin does not change largely. Further, since the magnetic field applying coil 14 is embedded in the cell part 2a, the rigidity is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens for magneto-optical recording applied to a magneto-optical disk device and an objective lens driving device for the objective lens.

[0002]

2. Description of the Related Art Information is recorded by a magneto-optical disk device by irradiating a magneto-optical disk having a recording layer made of a perpendicularly magnetized film on its surface with a laser beam to cure the temperature of the perpendicularly magnetized film in the irradiated portion. The coercive force is decreased by raising the temperature to near the temperature, and a magnetic field is applied to the irradiated portion to reverse the magnetization in the direction of the magnetic field.

Conventionally, as a method of recording information, it is general to irradiate a laser beam from the back surface of the magneto-optical disk and apply a magnetic field to the surface on which the recording layer is formed.

On the other hand, as in the objective lens described in Japanese Utility Model Laid-Open No. 3-84923, the objective lens for converging the laser light to form a light spot on the magneto-optical disk is integrated with the magnetic field applying coil. Some magnetic disks record information from the same direction.

[0005]

By adopting the structure in which the above-mentioned objective lens and the magnetic field applying coil are integrated, the size of the device can be reduced.

When the objective lens and the magnetic field applying coil are integrated, the magnetic field applying coil is provided above the objective lens (on the side of the magneto-optical disk) and the magnetic field applying coil is provided below the objective lens. The configuration is considered.

When the magnetic field applying coil is provided above the objective lens, the following problems occur.

First, since the magnetic field applying coil is provided between the objective lens and the magneto-optical disk, the distance between the objective lens and the magneto-optical disk becomes long, and the magneto-optical disk and the magnetic field applying coil come into contact with each other. There is a risk.

Further, since the coil is provided above the objective lens, the center of gravity of the movable portion in the objective lens driving device that supports the objective lens and performs the focusing operation and the tracking operation shifts upward, which deteriorates the balance of the movable portion. To do. Further, it is conceivable to provide a balancer on the movable portion as a countermeasure, but there is a possibility that the weight of the movable portion increases and the tracking characteristic deteriorates, or the current consumption increases.

Furthermore, since the resonance due to the lead wire for supplying a current to the magnetic field applying coil or the natural resonance of the magnetic field applying coil itself is directly transmitted to the movable portion,
There is a possibility that the follow-up characteristics will deteriorate.

On the other hand, the provision of the magnetic field applying coil below the objective lens means that the magneto-optical recording medium is separated by the thickness of the objective lens, and the information on the magneto-optical disk may not be accurately read. .

The present invention has been made in view of the above problems, and is an objective lens and an objective lens driving device for magneto-optical recording in which an objective lens and a magnetic field applying coil are integrated and the tracking characteristic is improved. The purpose is to provide.

[0013]

In order to achieve the above object, the present invention is characterized by using the means described below.

(1) A lens portion for forming a light spot on a magneto-optical recording medium, and a magnetic field applying coil for applying a magnetic field to the magneto-optical recording medium, which is concentric with the lens portion and integrally formed with the lens portion. In this objective lens for magneto-optical recording, the magnetic field applying coil is embedded in the outer peripheral portion of the lens portion.

(2) In the configuration of (1), at least two electrodes are provided on the outer peripheral portion for energizing the embedded magnetic field applying coil.

(3) In the configuration of (1) above, a plurality of magnetic field applying coils are independently embedded in the outer peripheral portion, and electrodes for energizing the magnetic field applying coils are provided in the outer peripheral portion. .

(4) A bobbin for holding the objective lens of (1), (2) or (3), and one end fixed to a supporting portion formed on this bobbin, and the other end fixed to the apparatus main body side. A supporting member for supporting the bobbin and a magnetic circuit for causing the objective lens to perform a focusing operation and a tracking operation, and at least two electrodes for energizing the magnetic field applying coil embedded in the objective lens. The bobbin is provided on the bobbin.

(5) In the structure of (4), the supporting member is a leaf spring, a hole is formed in the bobbin mounting portion which is one end of the leaf spring, and the coil for magnetic field application is energized in the supporting portion of the bobbin. It is characterized in that the electrodes are extended.

(6) One end is fixed to a bobbin for holding the objective lens of (2) and a supporting portion formed on the bobbin,
And a supporting member for supporting the bobbin by fixing the other end to the apparatus main body side, and a magnetic circuit for causing the objective lens to perform a focusing operation and a tracking operation, and further, a bobbin mounting portion at one end of the supporting portion. A hole formed in the hole, an extending portion extending from the electrode of the objective lens to cover the supporting portion, and the extending portion corresponding to the hole of the bobbin attaching portion when the supporting member is attached to the supporting portion. And a hole formed in.

(7) In the configuration of (4) or (5), the supporting member is a leaf spring, a hole is formed in a bobbin mounting portion that is one end of the leaf spring, and the hole is formed in the bobbin supporting portion. It is characterized in that it is provided with a protrusion that fits in the.

[0021]

By using the above-mentioned means, the following actions will occur.

In the configuration of (1), by embedding the magnetic field applying coil in the outer peripheral portion of the objective lens, it is possible to reduce the size and rigidity of the magnetic field applying coil. Further, when the objective lens having the configuration of (1) is installed in the objective lens drive device, the position of the center of gravity of the movable part including the objective lens and performing the focusing operation and the tracking operation is such that the magnetic field applying coil has a small size. As a result, the weight of the movable part is reduced, and the change is reduced.

In the configuration of (2), since the electrode for energizing the magnetic field applying coil is provided on the objective lens side, it is easy to supply power to the magnetic applying coil.

In the configuration of (3), a plurality of magnetic field applying coils are independently embedded in the outer peripheral portion of the objective lens, and electrodes corresponding to the plurality of magnetic field applying coils are provided, whereby the magnetic field It becomes easy to supply power to the applying coil, and even if a disconnection occurs in any of the plurality of magnetic field applying coils, another coil can be used for backup.

In the configuration of (4), when the objective lens is attached to the bobbin, wiring for energizing the magnetic field applying coil is made.

In the configuration of (5), wiring for energizing the magnetic field applying coil is made when the objective lens is attached to the bobbin, and the coil is energized through the leaf spring.

In the configuration of (6), the electrode in (2) is extended to the leaf spring mounting portion of the bobbin, and the leaf spring is fixed to this extended portion to energize the magnetic field applying coil. Connection is made. Furthermore, since the extending portion is separated from the objective lens, the influence of heat on the objective lens due to soldering or the like is reduced.

In the configuration (7), the leaf spring is easily positioned with respect to the bobbin by fitting it into the hole formed in the bobbin mounting portion of the leaf spring and the projection formed in the supporting portion of the bobbin.

[0029]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 14 is a perspective view showing the basic structure of an objective lens driving device, in which 1 is a bobbin and 2 is an objective lens.
The objective lens 2 is mounted in the center of the surface of the bobbin 1, and the lower portion of the objective lens 2 is a cylindrical through hole (described later). 3 is a yoke hole formed on both sides of the objective lens 2, 4 is a focusing coil wound around the side surface of the bobbin 1, 5 is a yoke coil facing the yoke holes 3, 3, and is attached to the surface of the focusing coil 4. The flat type tracking coil is provided, and 6 is a support portion to which a leaf spring, which will be a support member described later, is attached. The support portion 6 is formed on the edges of the collar portions 7, 7 formed on the upper and lower sides of the bobbin 1, and extends in the direction perpendicular to the yoke holes 3, 3 and on both sides of the objective lens 2. It will be. That is, the support portions 6 are formed at two locations for each of the collar portions 7, 7 at a total of four locations.

Further, 8 is a base, 9 is an outer yoke which is erected on the base 8, 10 is an inner yoke which is arranged side by side inside the outer yokes 9, 9, and 11 is opposed to the inner yoke 10 of the outer yoke 9. A permanent magnet is provided on the surface, 12 is a leaf spring as a support member, and 13 is a leaf spring support plate.

The bobbin 1 is supported on the base 8 by fixing one end of the leaf spring 12 to the support portion 6 and the other end to the leaf spring support plate 13. At this time, the inner yokes 10, 10 are loosely fitted in the yoke holes 3, 3 of the bobbin 1, and the permanent magnets 11, 11 face the tracking coils 5, 5. The focusing coil 4 and the tracking coil 5 are generated by passing a current through them.
The objective lens 2 is driven in the focusing or tracking direction by the action of the magnetic fields of 5 and the permanent magnet 11 and the inner and outer yokes 10 and 9.

FIG. 1 is a sectional view showing a first embodiment of the objective lens of the present invention. Reference numeral 2a is a cell portion which is an outer peripheral portion of the objective lens 2 which is a mounting portion on the bobbin 1, and 2b is a laser beam. Lens part for focusing, 14 is a magnetic field applying coil, 15
Indicates an electrode. The objective lens 2 is manufactured by molding, and at the time of molding, the cell portion 2a and the magnetic field applying coil 14 are integrally formed by embedding the magnetic field applying coil 14 in the cell portion 2a.

Further, an electrode 15 is provided on the outer periphery of the cell portion 2a by plating, and the electrode 15 is electrically connected to the magnetic field applying coil 14 in the cell portion 2a.

In the magneto-optical disk device employing such an objective lens 2, the laser light is focused by the lens portion 2b to form a light spot on the optical disk surface (not shown), and the magnetic field applying coil 14 is further passed through the electrode 15. Information is recorded by supplying power to the magnetic field, generating a magnetic field, and applying this magnetic field to the position of the light spot.

In the first embodiment of the objective lens constructed as described above, since the magnetic field applying coil 14 becomes relatively small, it is possible to prevent the bobbin from increasing in weight, which will be described later, and to position the center of gravity of the bobbin. Does not change significantly. Further, since the magnetic field applying coil 14 is embedded in the cell portion 2a, the rigidity is increased and, for example, disconnection of the coil due to weathering is prevented.

FIG. 2 is a sectional view showing a state in which the objective lens of FIG. 1 is mounted on a bobbin, 16 is a cylindrical through hole, and 17 is an electrode. The electrode 17 is provided around the through hole 16 on the surface of the bobbin 1, and when the objective lens 2 is placed on the bobbin 1, the electrode 15 and the electrode 17 overlap and are electrically connected. Then, power is supplied to the magnetic field applying coil 14 through the electrode 17.

FIG. 3 is a perspective view showing a bobbin supporting structure according to the first embodiment of the objective lens driving device having the bobbin shown in FIG. The same members as those in the basic configuration shown in FIG. 14 are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 3, two electrodes 17 are provided so as to be sandwiched between the bobbin 1 and the objective lens 2. One electrode serves as a positive electrode and the other electrode serves as a negative electrode. .
The through hole 16 of the bobbin 1 (see FIG. 2) is formed on one long side of the electrode 17.
A semi-circular recess is formed so that the other long side faces the supporting portions 6, 6.

On the supporting portion 6 of the bobbin 1, there is a bobbin mounting portion 12a which is one end of a leaf spring 12 made of a conductive metal.
Are fixed by adhesion or the like. Further, as shown in FIG. 4, the bobbin mounting portion 12 of the leaf spring 12 on the surface of the bobbin 1 is
By soldering S to the facing portion of a and the electrode 17,
The leaf spring 12 and the electrode 17 are electrically connected.

In the first embodiment of the objective lens driving device constructed as above, the leaf spring 12 to the electrode 17 and the electrode 15 are arranged.
Power can be supplied to the magnetic field applying coil 14 via the. Therefore, a lead wire for supplying power to the magnetic field applying coil 14 is unnecessary.

FIG. 5 is a perspective view showing a bobbin supporting structure according to a second embodiment of the objective lens driving device having the bobbin shown in FIG. The second embodiment of the objective lens driving device is different from the structure of the first embodiment described above in that the electrode 17 has an extending portion 17a.
Is provided, and the surface of the support portion 6 is covered with the extending portion 17a, and the point that a complex type hole 12b of a circular shape and a cross shape is formed on the surface of the bobbin mounting portion 12a of the leaf spring 12.

As shown in FIG. 6, this leaf spring 12 is fixed by filling the hole 12b by soldering S together with the extending portion 17a on the surface of the supporting portion 6, and both are electrically connected.

In the second embodiment of the objective lens driving device constructed as described above, the leaf spring 12 is obtained only by soldering together with the operation and effect of the first embodiment of the objective lens driving device described above.
Can be fixed to the bobbin 1.

FIG. 7 is a perspective view showing a bobbin supporting structure according to a third embodiment of the objective lens driving device having the bobbin shown in FIG. In the third embodiment, the protrusion 17b is formed on the surface of the extending portion 17a of the electrode 17 in the structure of the second embodiment, and the circular hole 1 is formed on the surface of the bobbin mounting portion 12a of the leaf spring 12.
2c is formed.

As shown in FIG. 8, the leaf spring 12 is formed by fitting the circular hole 12c of the bobbin mounting portion 12a to the protrusion 17b of the extending portion 17a and then fixing the same by soldering S.

In the third embodiment of the objective lens driving device thus constructed, the position where the leaf spring 12 is attached to the bobbin 1 can be easily determined and the bobbin 1 can be more firmly fixed.

FIG. 9 is a perspective view showing a modification of the third embodiment of the objective lens driving device shown in FIG. 7, and 18 is a V-shape formed on the surface of the extending portion 17a of the electrode 17 to the supporting portion 6. A groove, 19 is a cylindrical bar spring which is a supporting member of the bobbin 1. The surface of the V-shaped groove 18 is covered with an electrode 17, and one end of the bar spring 19 is placed on the V-shaped groove 18 and soldered S to fix the bar spring 19 to the V-shaped groove 18. .

With this structure, similarly to the third embodiment of the objective lens driving device, the rod spring 19 can be easily positioned with respect to the bobbin 1, and the rod spring 19 is fixed to the bobbin 1 only by soldering. As a result, the assembly work becomes easy.

FIG. 10 is a sectional view showing the structure of the second embodiment of the objective lens, and FIG. 11 is a perspective view showing the objective lens driving device equipped with this objective lens. In FIG. 10, 20
Is an objective lens, 21 is a magnetic field applying coil embedded in the outer peripheral portion of the objective lens 20, and 22 is an electrode. The electrode 22 is made of a conductive metal plate, and one end of the electrode 22 is embedded in both sides of the objective lens 20 on a horizontal line that passes through the center of gravity of the objective lens 20 and extends in a direction perpendicular to the optical axis. The other ends of the electrodes 22 and 22 are connected to the supporting portions 6 and 6 of the bobbin 1.
(See Fig. 14), and holes 23, 23 at the tip.
Are formed.

The objective lens 20 constructed in this way is shown in FIG.
It is placed in the center of the bobbin 1 as shown in FIG. In FIG. 11, 6a indicates a step at which the leaf spring 12 provided on the surface of the support portion 6 is attached. When the objective lens 20 is placed on the bobbin 1, a gap due to the step 6a is formed between the other end of the electrode 22 and the support portion 6. Insert the leaf spring 12 into this gap, and
The leaf spring 12, the electrode 22, and the supporting portion 6 are fixed to each other by combining 12d and the hole 23 and soldering S to the hole 23 of the electrode 22.

The electrode 22 may be formed by integrally molding the magnetic field applying coil 21 at the time of molding the lens and embedding one end by inserting a metal plate.

In the second embodiment of the objective lens constructed in this manner, the magnetic field applying coil 21 is connected to one end of the electrode 22 and the other end is directly fixed to the leaf spring 12, thereby No need for a lead-out line from the above, and it is not necessary to install the electrode 17 (FIG. 3) on the bobbin 1 as in the first embodiment of the objective lens described above. In addition, the objective lens 20
Since there is a distance between the lens part of and the hole 23 of the electrode 22,
The thermal effect on the lens portion 20b (see FIG. 10) due to soldering is reduced.

FIG. 12 is a plan view showing a third embodiment of the objective lens, and FIG. 13 is a sectional view taken along line XX of FIG. In the figure, 24 is an objective lens, 25 is an electrode, and 26 is a magnetic field applying coil. Both one end of the electrode 25 and the magnetic field applying coil 26 are embedded in the cell portion 24a of the objective lens 24.

As shown in FIGS. 12 and 13, twelve electrodes 25 are provided in the cell portion 24a in a direction perpendicular to the optical axis of the objective lens 24 and radially around the center of gravity. In this third embodiment, 6 out of 12 electrodes are positive electrodes,
Six are used as negative electrodes. Further, in the cell portion 24a, coils P, Q, R, which are element coils of three sets of independent magnetic field applying coils 26, are embedded. In this magnetic field applying coil 26, one terminal of the coil P is connected with two electrodes A, which are positive electrodes of the electrode 25, inside the cell portion 24a, and the other terminal is a negative electrode corresponding to the electrode A. There is 2
The electrodes A'of the sheet are connected. Similarly, electrodes BB 'and CC' are connected to the terminals of the coils Q and 12, respectively.

In the electrode 25 provided on the objective lens 24, the positional relationship between the electrodes A, B, C and the electrodes A ', B', C'is symmetrical about the optical axis. Therefore, the electrode
25 is a group of electrodes A, B, C and electrodes A ', B',
It is divided into a group with C ', that is, a positive electrode group and a negative electrode group.

In the third embodiment of the objective lens constructed as described above, since a plurality of electrodes are connected to one coil, for example, even if one electrode is broken, it is possible to back up with another electrode. Become. Further, since a plurality of independent coils are provided, even if any one of them becomes unusable, it becomes possible to back up by supplying a large amount of current to the other coils.

Further, since the electrodes are divided into the group of the electrodes A, B and C and the group of the electrodes A ', B' and C ', that is, the group of the positive electrode and the negative electrode, the power feeding can be easily performed. The first to third configurations of the objective lens driving device described above can be used.

[0059]

The present invention has the following effects by being configured as described above.

In the structure of claim 1, by embedding the magnetic field applying coil in the outer peripheral portion of the objective lens, the distance between the objective lens and the magneto-optical recording medium is not changed, and the objective lens driving device is used. Since the change in the position of the center of gravity of the movable portion can be suppressed to a small value, good balance is achieved. Therefore, the performance of recording / reproducing information can be improved.

According to the second aspect of the invention, since it is not necessary to draw a terminal, a power supply line, or the like from the inside of the objective lens in order to supply power to the magnetic field applying coil, the wiring work becomes easy.

In the third aspect of the invention, since there are a plurality of coils embedded in the objective lens, when one coil cannot be used, it can be backed up by another electrode or coil.

According to the fourth aspect of the invention, since the wiring for energizing the magnetic field applying coil is made at the time when the objective lens is attached to the bobbin, the efficiency of the assembling work is improved.

In the structure of claim 5, when the objective lens is attached to the bobbin, connection is made to energize the magnetic field applying coil, and power is supplied to the coil through the leaf spring. There is no need for a leader line from, and there is no disconnection. Furthermore, since the objective lens is separated from the extending portion, the influence of heat on the objective lens due to soldering or the like is reduced, so that the performance of the objective lens can be prevented from deteriorating during assembly.

According to the seventh aspect of the invention, since the hole formed in the bobbin mounting portion of the leaf spring is fitted into the protrusion formed in the supporting portion of the bobbin, the leaf spring is positioned with respect to the bobbin. Can be accurately and firmly fixed to the bobbin.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the objective lens of the present invention.

FIG. 2 is a cross-sectional view showing a state in which the objective lens of FIG. 1 is mounted on a bobbin.

FIG. 3 is a perspective view showing a first embodiment of the objective lens driving device of the present invention.

4 is a cross-sectional view showing a mounting state of a leaf spring in the objective lens driving device of FIG.

FIG. 5 is a perspective view showing a second embodiment of the objective lens driving device of the present invention.

6 is a cross-sectional view showing a mounting state of a leaf spring in the objective lens driving device of FIG.

FIG. 7 is a perspective view showing a third embodiment of the objective lens driving device of the present invention.

8 is a cross-sectional view showing a mounting state of a leaf spring in the objective lens driving device of FIG.

9 is a perspective view showing a modified example of the objective lens driving device of FIG.

FIG. 10 is a sectional view showing a second embodiment of the objective lens of the present invention.

11 is a perspective view showing an objective lens driving device on which the objective lens of FIG. 10 is mounted.

FIG. 12 is a plan view showing a third embodiment of the objective lens of the present invention.

13 is a sectional view taken along line XX of FIG.

FIG. 14 is a perspective view showing a basic configuration of an objective lens driving device of the present invention.

[Explanation of symbols]

1 ... Bobbin, 2, 20, 24 ... Objective lens, 2a, 24a ...
Cell part, 2b ... Lens part, 4 ... Focusing coil, 5 ... Tracking coil, 6 ... Support part,
12 ... Leaf spring, 12a ... Bobbin mounting part, 12b, 12c, 12d ...
Circular hole, 14, 21, 26 ... Coil for applying magnetic field, 15, 17,
22, 25 ... Electrodes, 17a ... Extensions, 17b ... Protrusions, 18 ... V
Grooves, 19… bar springs, 23… holes.

Claims (7)

[Claims] 1. A lens unit for forming a light spot on a magneto-optical recording medium, and a magnetic field applying coil for applying a magnetic field to the magneto-optical recording medium, which is concentric with the lens unit and integrally formed with the lens unit. An objective lens for magneto-optical recording, wherein the magnetic field applying coil is embedded in an outer peripheral portion of the lens portion. 2. The objective lens according to claim 1, wherein at least two electrodes for energizing the buried magnetic field applying coil are provided on the outer peripheral portion. 3. The objective lens according to claim 1, wherein a plurality of magnetic field applying coils are independently embedded in the outer peripheral portion, and electrodes for energizing the magnetic field applying coils are provided in the outer peripheral portion. 4. A bobbin for holding the objective lens according to claim 1, and a bobbin by fixing one end to a supporting portion formed on the bobbin and fixing the other end to the apparatus main body side. And a magnetic circuit for causing the objective lens to perform a focusing operation and a tracking operation. Further, at least two electrodes for energizing a magnetic field applying coil embedded in the objective lens are provided on the bobbin. An objective lens driving device characterized by being provided. 5. A support member is a leaf spring, a hole is formed in a bobbin mounting portion which is one end of the leaf spring, and an electrode for energizing a magnetic field applying coil is extended to the support portion of the bobbin. 5. The objective lens driving device according to claim 4, which is characterized in that. 6. A bobbin that holds the objective lens according to claim 2, and a support that supports the bobbin by fixing one end to a supporting portion formed on the bobbin and fixing the other end to the apparatus main body side. A member and a magnetic circuit for causing the objective lens to perform a focusing operation and a tracking operation, and further, a hole formed in a bobbin mounting portion at one end of the support portion and the support extending from an electrode of the objective lens. An objective lens driving device, comprising: an extending portion that covers the portion; and a hole formed in the extending portion that corresponds to the hole of the bobbin mounting portion when the supporting member is attached to the supporting portion. . 7. A support member is a leaf spring, a bobbin mounting portion which is one end of the leaf spring is provided with a hole, and a projection for fitting into the hole is provided on the support portion of the bobbin. The objective lens driving device according to claim 4 or 5.