JPH087537Y2 - Objective lens driving device for magneto-optical recording / reproducing apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is used for a magneto-optical recording / reproducing apparatus adapted to write a desired information signal onto an optical disc having a magnetic thin film as a recording film constituting a signal recording layer. And an objective lens driving device.

[Outline of device]

The present invention relates to an objective lens driving device used in a magneto-optical recording / reproducing device for writing a desired information signal on an optical disc having a magnetic thin film that is perpendicularly magnetized as a recording film forming a signal recording layer, and is a semiconductor device. A light beam emitted from a light source such as a laser is accurately focused on a signal recording layer of an optical disc that is rotated, and a recording track formed on the optical disc is accurately scanned. A magnetic circuit unit of electromagnetic drive means for electromagnetically driving an objective lens for focusing a light beam on the signal recording layer of the optical disc in a direction parallel to the optical axis direction of the objective lens and a direction orthogonal to the optical axis direction is formed. By making the opposite magnetized surfaces of the pair of magnets that are opposite to each other, the leakage magnetic flux from the magnetic circuit section is suppressed, and the magnetic flux is applied to the optical disc. Suppressing the influence on the field, and makes it possible to record with less noise information signal.

[Conventional technology]

Conventionally, a magneto-optical recording / reproducing apparatus has been known in which an optical disk having a magnetic thin film having a magneto-optical effect as a recording film is used as a recording medium. As shown in FIG. 4, this magneto-optical recording / reproducing apparatus has magnetic field generating means for applying a magnetic field to the optical disc 1 on one main surface side of the optical disc 1 which is rotated by a predetermined disc rotation driving device. A magnetic head 2 composed of a magnet or the like is arranged oppositely, and an optical pickup device 3 for irradiating a light beam to the other main surface side which is the signal recording surface side of the optical disk 1 facing the magnetic head 2 is oppositely arranged. Is configured. In this magneto-optical recording / reproducing apparatus in which a magnet is used as the magnetic head 2, since the magnetic head 2 reverses the direction of the magnetization of the recording film, the magnetic pole facing the optical disk 1 can be appropriately selected. Thus, it is rotatably supported around the support shaft 4. The magnetic head 2 is rotationally operated by supplying a current in a specific direction to a coil 5 arranged around the magnetic head 2, so that its N pole or S pole faces the main surface of the optical disc 1. Is configured.

In such a device, in order to write an information signal to the optical disc 1 in which the recording film is perpendicularly magnetized in one direction as shown by the arrow in FIG. 4, the optical pickup device 3 is used.
While increasing the intensity of the light beam applied to the recording film of the optical disc 1, the current in the opposite direction is supplied to the coil 5 to rotate the magnetic head 2 by 180 ° to change the direction of magnetization of the recording film. Apply magnetic fields in opposite directions. Then, the optical disc 1 is rotated while modulating the light beam according to the information signal to be recorded. Then, the direction of the magnetization of the recording film of the optical disc 1 is reversed according to the change in the intensity of the light beam, and the desired information signal is recorded.

By the way, in the optical pickup device 3 used in the magneto-optical recording / reproducing apparatus, the light beam is accurately focused on the recording film of the optical disc 1 which is rotated, and the recording track formed on the optical disc 1 is arranged. In order to perform accurate scanning, the objective lens 6 for focusing the light beam on the recording film of the optical disc 1 is provided with a focus direction parallel to the optical axis direction of the objective lens 6 and orthogonal to the optical axis direction. An objective lens driving device 7 for driving and displacing in the tracking direction of the moving direction is provided. The objective lens driving device 7 is configured to electromagnetically drive the objective lens 6 by electromagnetic driving means. That is, as shown in FIG. 5, the objective lens driving device 7 is provided on a bobbin 8 holding the objective lens 1 and is provided with a focus control driving coil 9 for moving and displacing the objective lens 1 in the focusing direction and the tracking direction. The drive coil 10 for tracking control, the above drive coils 9,
It is composed of a magnetic circuit section 12 having a pair of magnets 11 and 12 and yokes 13 and 14 that form a magnetic path and are arranged to face each other so as to face each other with the bobbin 7 interposed therebetween. . As shown in FIG. 5, the pair of magnets 11 and 12 constituting the magnetic circuit portion 12 are magnetized so that the magnetic poles of the surfaces facing the drive coils 9 and 10 are N poles. . That is, the pair of magnets 11 and 12 are magnetized with the same pole so that the opposite magnetized surfaces become N poles.

[Problems to be solved by the device]

The magnetic flux Φ ₁ in the magnetic circuit section 15 of the objective lens driving device thus configured forms a magnetic path from each magnet 11, 12 to the inner yoke 14 as shown in FIG. Further, as shown in FIG. 5, a leakage magnetic flux Φ ′ ₁ is generated which is vertically incident on the optical disc 1. This leakage magnetic flux Φ ′ ₁ exists in the area of the optical disc 1 where the light beam is focused, where the information signal is to be written.
The leakage flux Φ ′ ₁ affects the recording film of the optical disc 1 which is magnetized perpendicularly, and the reversal control of the magnetization direction of the recording film by the light beam modulated according to the information signal to be recorded is performed. The information cannot be written accurately and the information signal cannot be written with good recording characteristics.

Therefore, in order to suppress the generation of such leakage magnetic flux Φ ′ ₁ , there has been proposed an objective lens driving device in which the magnetic circuit portion 15 is covered with a shield case made of a material having a high magnetic permeability such as permalloy. . However, the shield case acts as a magnetic path, absorbs the magnetic flux from the magnetic circuit section 12, and generates a leakage magnetic flux from the shield case portion. This leakage magnetic flux also has a component that is substantially perpendicular to the optical disc 1 from the magnetic path of the magnetic circuit unit 15. Since the shield case is arranged so as to cover the magnetic circuit section 15,
Since it is located close to the optical disc 1, even if the leakage magnetic flux Φ ′ ₁ from the shield case is a small amount, it affects the recording film magnetized in the perpendicular 1 of the optical disc 1. However, it becomes impossible to write an information signal having good recording characteristics.

Therefore, the present invention suppresses the generation of leakage magnetic flux in the vertical direction, which is the thickness direction of the optical disc, which may affect the recording film that is perpendicularly magnetized in the optical disc, and has a good recording characteristic to generate an information signal. The object of the present invention is to provide an objective lens driving device for a magneto-optical recording / reproducing device that enables writing.

[Means for solving the problem]

In order to achieve the above-mentioned object, the present invention provides an objective lens, a bobbin for holding the objective lens, a bobbin in a direction parallel to the optical axis of the objective lens, and a direction orthogonal to the optical axis direction. An objective lens support mechanism for movably displacing, a drive coil for generating a driving force for moving and displacing the objective lens in a direction parallel to the optical axis and a direction orthogonal to the optical axis direction, and an optical axis of the objective lens And a pair of magnets arranged opposite to each other with the bobbin sandwiched therebetween in a direction orthogonal to the pair of magnets constituting the magnetic circuit section, and an optical axis of the objective lens. Magnetization is performed in the orthogonal direction, and the opposite magnetized surfaces have different polarities.

[Action]

According to the present invention, a pair of magnets arranged to face each other in the direction orthogonal to the optical axis of an objective lens forming a magnetic circuit unit are magnetized in a direction orthogonal to the optical axis of the objective lens, Since the magnetized surfaces of the magnets facing each other have different poles, the magnetic path is horizontal from one magnet with the magnetized surfaces facing each other to the other magnet, and the objective lens faces each other. The generation of leakage magnetic flux in the vertical direction, which is the thickness direction of the optical disk to be arranged, is eliminated.

〔Example〕

Hereinafter, a specific embodiment of the present invention will be described with reference to the drawings.

The objective lens driving device according to the present invention is useful when applied to an optical pickup device of a magneto-optical recording / reproducing device in which a desired information signal is written on an optical disc having a magnetic thin film as a recording film constituting a signal recording layer. It is a thing. That is, the invention of the present application constitutes an optical pickup device in combination with an optical system block having optical components such as a light source such as a semiconductor laser, a photodetector such as a photodiode, and a beam splitter. The light beam emitted from the light source is focused on the signal recording layer of the optical disc.

This objective lens driving device, as shown in FIGS. 2 and 3, includes an objective lens 21 for focusing a light beam emitted from a semiconductor laser arranged on the optical system block side onto a signal recording layer by light. , Bobbin 22 that holds this objective lens 21
And an objective lens support mechanism 23 for supporting the objective lens 21 held by the bobbin 22 so as to be movable and displaceable in a direction parallel to the optical axis of the objective lens 21 and a direction orthogonal to the optical axis direction.
A focus control drive coil 24 for generating a driving force for moving and displacing the objective lens 21 supported by the bobbin 22 in a direction parallel to the optical axis direction of the objective lens 21, and the objective lens 21 by the optical axis. A tracking control drive coil 25 that generates a drive force for moving and displacing in a direction orthogonal to the direction, and a magnetic circuit unit 28 having a pair of magnets 26, 27 that are arranged opposite to each other with the bobbin 22 interposed therebetween. It is configured as the main component.

The objective lens 21 is fitted and held in a lens holder 29, and the bobbin 22 is fitted and held in a fitting hole 30 formed in the thickness direction from the plane of the bobbin 22. Is held. This bobbin 22
As shown in FIG. 3, is formed of a molded body of synthetic resin, and a light introducing hole 31 for making a light beam emitted from an optical system block (not shown) incident is formed on one side surface. The light beam introduced from the light introducing hole 31 is reflected by the reflecting mirror arranged in the bobbin 22 to form the objective lens.
21.

The bobbin 22 is supported and the objective lens 21 is
An objective lens support mechanism 23, which is movably supported in a direction parallel to the optical axis of 21 and in a direction orthogonal to the optical axis direction, includes a pair of left and right objective lens support blocks 32 and 33. As shown in FIG. 3, the objective lens support blocks 32 and 33 have a pair of leaf springs 36 and 37 formed by a metal plate such as a thin stainless plate in parallel between a support base 34 and a bobbin support base 35, as shown in FIG. It is constructed by connecting and connecting to. Then, the support base 34 is formed with a thin hinge portion 38 by forming grooves from both side surfaces in a height direction orthogonal to the extending direction of the pair of leaf springs 36, 37. . Further, on one side surface side of the bobbin support base 35, a fitting support portion 40 for the bobbin 22 is connected via a hinge portion 39 formed in parallel with a hinge portion 38 formed on the support base 34. It is set up. The bobbin 22 is supported by the pair of objective lens support blocks 32 and 33 by fitting the fitting support portions 40 into the fitting grooves 41 and 42 formed on both sides.

Objective lens support mechanism supporting the bobbin 22 as described above
23 is a support base 3 for a pair of objective lens support blocks 32, 33.
4 is fixedly supported in a housing 43 made of a magnetic material such as metal that constitutes the yoke of the magnetic circuit unit 28. The fixed support of the support base 34 to the housing 43 is carried out by inserting and fitting the fitting holes 44 formed in the support base 34 into the support pins 45, 45 which are set up in the housing 43. .

In this way, the housing via the objective lens support mechanism 23
The bobbin 22 supported so as to be housed in the 43 is a support base.
By elastically displacing the pair of leaf springs 36 and 37 with the 34 side as a fixed point, the leaf springs 36 and 37 are moved and displaced in a direction parallel to the optical axis direction of the objective lens 21 held by the bobbin 22, and the support base 34
The hinge part 38 and the hinge part 39 of the bobbin supporting base 35 are displaced, so that the hinge part 38 is moved and displaced in the direction orthogonal to the optical axis direction.

As described above, the bobbin 22 supported by the objective lens support mechanism 23 has a pair of front and rear focus control drive coils.
A pair of tracking control drive coils 25 are attached to the front and rear of 24. The drive coils 24 and 25 are attached to both front and rear side surfaces of the leaf springs 36 and 37 in the extension direction. That is, the tracking control drive coil 25 is wound in a rectangular tubular shape as shown in FIG. 3, and is fitted from the open front and rear portions of the bobbin 22.
Mounted on. In addition, the focus control drive coil 24
3 are wound so as to form a rectangular plane rectangular shape as shown in FIG. 3, and are mounted in pairs in the front and rear over the upper and lower corners of the bobbin 22.

Further, the bobbin 22 holding the objective lens 21 is provided in the housing 43 in which the objective lens support mechanism 23 is provided, and the objective lens supporting mechanism 23 is combined with the focus control drive coil 24 and the tracking control drive coil 25. A magnetic circuit section 28 is configured which constitutes an electromagnetic driving means for moving and displacing the lens 21 in a direction parallel to the optical axis direction of the objective lens 21 and a direction orthogonal to the optical axis direction. That is, the housing 43
Inside, a pair of magnets 26 that face each other with the bobbin 22 sandwiched therebetween are provided so as to face the focus control drive coil 24 and the tracking control drive coil 25 respectively disposed on the front and rear surfaces of the bobbin 22. , 27 are provided. Then, one magnet 26 is attached via a magnet attachment plate 48 located on the support base 34 side of the objective lens support mechanism 23 and arranged across both sides of the housing 43, and the other magnet 27 is attached. The magnet mounting plate 49 is mounted on the front surface side of the housing 43. Further, the housing 43 includes the magnets
Inner yokes 50 and 51 are arranged so as to face 26 and 27. The inner yokes 50, 51 are arranged so as to extend across both sides of the housing 43, and are inserted into the tracking control drive coils 25 arranged in front of and behind the bobbin 22, respectively. The bobbin 22 includes the inner yokes 50, 51.
Drive coil for tracking control in order to insert
Openings 52, 53 are opened at positions corresponding to the 25 openings.

By the way, the pair of magnets 26, 27 constituting the magnetic circuit section 28 are magnetized so that the magnetized surfaces facing each other have different polarities, as shown in FIG. That is, one magnet 26 has a magnetized surface facing the other magnet 27 as an N pole, and the other magnet 27 is one magnet.
It is magnetized with the magnetized surface facing 26 as the S pole. By magnetizing in this way, the magnetic flux Φ ₃ from one magnet 26 forms a magnetic path from this magnet 26 to the inner yoke 50, as shown by the arrow in FIG. 1, and from the other magnet 27. The magnetic flux Φ ₄ forms a magnetic path from the inner yoke 51 to the S pole surface of the other magnet 27, as shown by the arrow in FIG. Even if there is a leakage magnetic flux Φ ′ ₃ that does not directly enter the inner yoke 50 among the magnetic fluxes Φ ₃ radiated from the one magnet 26, this leakage magnetic flux Φ ′ ₃ has an opposing magnetized surface on one side. The magnet 27 is attracted by the other magnet 27, which is an S pole having a different pole from the magnet 26, and is parallel to the surface of the optical disc 1 on which the objective lens 21 is arranged to face. Therefore, in this magnetic circuit unit 28, all the magnetic fluxes Φ ₃ and Φ ₄ including the leakage magnetic flux Φ ′ ₃ are generated by the optical disc 1.
It is not a component that affects the recording film that is parallel to and perpendicular to the plane of.

The pair of magnets 26, 27 may be magnetized as long as the surfaces facing each other have different polarities.
May be magnetized in the opposite manner to the example shown in FIG.

By the way, the magnetic path of the magnetic circuit unit 28 of the objective lens driving device according to the present invention is the same in the magnets 26 and 27. Therefore, the focus control drive coils 24, 24 respectively arranged before and after the bobbin 22 are wound so as to generate the drive force in the same direction in cooperation with the magnetic path in the one direction, or the same. The direction of the supplied current is controlled to generate the directional driving force.

Further, the objective lens driving device according to the present invention is provided with a shield case formed of a high magnetic permeability material such as permalloy so as to cover the magnetic circuit portion 28 as needed. By providing such a shield case, the magnetic fluxes to the drive coils 24 and 25 become unbalanced due to the displacement of the mounting positions of the magnets 26 and 27 facing each other, and the leakage flux in the direction of incidence on the surface of the optical disc 1. Even if occurs, the shield case can reduce the leakage flux in the direction of incidence on the surface of the optical disc 1 to a level that does not affect the information signal.

[Effect of device]

As described above, according to the present invention, a pair of magnets arranged to face each other in the direction orthogonal to the optical axis of the objective lens forming the magnetic circuit unit is magnetized in the direction orthogonal to the optical axis of the objective lens. Since the magnetized surfaces facing each other of the pair of magnets have different polarities, the magnetic path is in the horizontal direction from one magnet with the magnetized surfaces facing each other having different polarities toward the other magnet, The generation of leakage flux in the vertical direction, which is the thickness direction of the optical disk, which affects the recording film that is magnetized perpendicularly in the optical disk, is eliminated.

Therefore, it is possible to provide an objective lens driving device for a magneto-optical recording / reproducing device that enables writing of information signals with good recording characteristics.

[Brief description of drawings]

FIG. 1 is a sectional view showing an objective lens driving device according to the present invention in relation to an optical disk, FIG. 2 is a perspective view of the objective lens driving device, and FIG. 3 is an exploded perspective view thereof. FIG. 4 is a schematic side view showing a magneto-optical recording / reproducing apparatus,
FIG. 5 is a schematic side view schematically showing a state of magnetic flux in a magnetic circuit section of a conventional objective lens driving device. 1 ... Optical disc 21 ... Objective lens 22 ... Bobbin 23 ... Objective lens support mechanism 24 ... Focus control drive coil 25 ... Tracking control drive coil 26, 27 ... Magnet 28 ... Magnetic circuit section

Claims (1)

[Scope of utility model registration request] 1. An objective lens, a bobbin that holds the objective lens, and an objective lens that supports the objective lens such that the objective lens is movable and displaceable in a direction parallel to an optical axis of the objective lens and a direction orthogonal to the optical axis direction. A support mechanism, a drive coil for generating a driving force for moving and displacing the objective lens in a direction parallel to the optical axis and a direction orthogonal to the optical axis direction, and the bobbin in the direction orthogonal to the optical axis of the objective lens. It has a magnetic circuit section having a pair of magnets that are arranged so as to face each other, and the pair of magnets forming the magnetic circuit section are magnetized in a direction orthogonal to the optical axis of the objective lens. And an objective lens driving device for a magneto-optical recording / reproducing apparatus in which oppositely polarized magnetized surfaces have different polarities.