JP2000315341A - Magneto-optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magneto-optical pickup giving consideration to the adhesive position of a collimator lens so as to reduce defocusing caused by a temperature change. SOLUTION: When defocusing occurs in a recording medium direction on an SIL lens because of a temperature change in a magneto-optical pickup, to reduce this defocusing, a collimator lens 116 is fixed while the part of its light source 104 side is abutted on the abutting part 204a of a mirror frame 204 by an adhesive. On the other hand, when defocusing occurs in a direction away from the recording medium on the SIL lens because of a temperature change in the magneto-optical pickup, to reduce this defocusing, the collimator lens 116 is fixed while the portion of its side opposite the light source 104 is abutted on the abutting part 204a' of the mirror frame 204 by an adhesive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical pickup provided with a magneto-optical head having a near-field optical element and a magnetic field generating coil.
(Solid immersion lens), SIM (solid immersion mirror), optical fiber and the like.

[0002]

2. Description of the Related Art As shown in FIG. 5 (a), for example, Japanese Patent Application Laid-Open No. H10-112036 discloses a light source unit 2 for emitting recording and reproduction laser light, and a laser light from the light source unit 2. Recording / reproducing apparatus comprising a magneto-optical head 6 for condensing light on the magneto-optical disk 4 and a signal detection unit 8 for receiving return light from the magneto-optical disk 4 and detecting a tracking state detection signal and a magneto-optical signal It is shown. The light source unit 2 is provided with a light source (not shown) and a collimator lens (not shown) for converting laser light from the light source into parallel light.

In this recording / reproducing apparatus, the light source unit 2 is fixed to the recording / reproducing apparatus, and the magneto-optical head 6 and the signal detecting unit 8 are mounted on an arm 12 which is rotatable about an arm rotation shaft 10. ing. Further, a mirror 14 and a beam splitter 16 are attached to the arm 12.

The magneto-optical head 6 has an objective lens 18 and a solid immersion lens 2 as shown in FIG.
0, and a magnetic field generating coil 22. These objective lens 18, solid immersion lens 20 (hereinafter, referred to as SIL 20), and magnetic field generating coil 22
It is positioned and fixed integrally with the slider 24.

In such a configuration, the light source unit 2
Is reflected from the beam splitter 16, is reflected by the mirror 14 in the direction of the magneto-optical disk 4, and is condensed on the magneto-optical disk 4 via the magneto-optical head 6. At this time, the return light reflected from the magneto-optical disk 4 is guided to the mirror 14 via the magneto-optical head 6, reflected from the mirror 14, passed through the beam splitter 16, and guided to the signal detection unit 8. The signal detection unit 8 detects a tracking state detection signal and a magneto-optical signal.

[0006]

Normally (normal temperature), laser light emitted from a light source (not shown) in the light source unit 2 is condensed by an objective lens 18 and is condensed with the above-mentioned solid immersion lens or SIL 20. Focus is achieved at the contact position of the magnetic disk 4.

However, when the temperature inside the recording / reproducing device changes due to the environment (for example, from 5 ° C. to 60 ° C.), the SIL 20 is changed due to a change in the position of optical components other than a collimator lens (not shown) or a change in optical characteristics. A focus shift (defocus) occurs between the optical disk and the magneto-optical disk 4.

In this case, the change in the position of the optical component and the change in the optical characteristics include, for example, a change in the distance between the objective lens 18 and the SIL 20 which is integrally fixed to the slider 24, a change in the radius of the SIL 20, Objective lens 18
Such changes include changes in the refractive index itself, changes in the surface curvature, changes in the thickness, etc., and changes in the working distance of the objective lens 18 (the distance from the lowermost surface of the objective lens to the surface of the magneto-optical disk).

When such a focus shift (defocus) occurs, the size of the spot on the magneto-optical disk 4 changes, so that it is difficult to detect the tracking state detection signal and the magneto-optical signal with high accuracy. Become.

The present invention has been made in order to solve such a problem, and an object of the present invention is to provide a magneto-optical pickup in which a bonding position of a collimator lens is considered so as to reduce defocus caused by a temperature change. To provide.

[0011]

In order to achieve the above object, the present invention provides a light source, a collimator lens for collimating laser light emitted from the light source, and a laser emitted from the light source. A magneto-optical head having a near-field optical element and a magnetic field generating coil for condensing light toward a recording medium, a support for supporting a light source, a lens frame for holding a collimator lens, and a lens frame attached to the support and mounted on the support In the magneto-optical pickup provided with a holder for holding the lens so as to be adjustable in the optical axis direction, the collimator lens has its light source side portion fixed to the lens frame with an adhesive. Further, the present invention provides a light source, a collimator lens for collimating the laser light emitted from the light source, a near-field optical element for condensing the laser light emitted from the light source toward a recording medium, and a magnetic field generation. A magneto-optical head having a coil, a support for supporting a light source, a lens frame for holding a collimator lens,
In a magneto-optical pickup having a holder attached to a support and holding the lens frame so as to be adjustable in the optical axis direction, the collimator lens has a portion opposite to the light source fixed to the lens frame with an adhesive. .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magneto-optical pickup according to an embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 schematically shows a configuration of a magneto-optical pickup 100 according to the present embodiment, and FIG.
The magneto-optical pickup 100 is a swing arm 102
The state arranged above is shown.

As shown in FIGS. 1 and 2, a magneto-optical pickup 100 according to the present embodiment has a light source (semiconductor laser) 104 capable of emitting laser light for recording and reproduction, and light emitted from the light source 104. A galvanomirror 106 for scanning the laser light in a predetermined direction, an imaging lens 110 for converting the laser light emitted through the galvanomirror 106 into a substantially parallel light beam, and a light guided through the imaging lens 110 Objective lens 108 and a near-field optical element, that is, an SIL (solid immersion lens), for condensing the laser light on a recording surface (not shown) of the recording medium 112.
A lens 109. The galvanomirror 106 and the front focal position Ff of the objective lens 108 are located at optically conjugate positions with each other.

Further, the magneto-optical pickup 100 of the present embodiment is provided with a light guide optical system 114 for guiding the laser beam from the light source 104 to the galvanomirror 106. A collimator lens 116 for converting a laser beam from the light source 104 into a parallel light beam,
And a relay lens 118 for condensing the parallel light flux emitted from the collimator lens 116 again.

In such a magneto-optical pickup 100, the collimator lens 116 and the relay lens 11
The center of 8, the center of the imaging lens 110 and the objective lens 108, the center of the SIL lens 109, and the rotation center of the galvanomirror 106 coincide on the same optical axis A.

In the optical path between the collimator lens 116 and the relay lens 118, a galvanomirror 106
A tracking detector 120 capable of optically detecting a tracking state by receiving return light (reflected light reflected from the recording surface of the recording medium 112) from the recording medium 112 is provided. The galvanometer mirror 106 and the imaging lens 11
An angle detector 122 that can optically detect the rotation angle of the galvanometer mirror 106 is disposed in the optical path between 0 and 0.

The tracking detector 120 has a beam splitter 124 for reflecting the return light from the galvanomirror 106, receives the return light reflected from the beam splitter 124, and generates an electric signal corresponding to a change in the light receiving position, ie, tracking. Light receiving element 126 that outputs a state detection signal
Are provided.

The objective lens 108 and the SIL lens 1
09 and a magnetic field generating coil (not shown) are the magneto-optical head 12 supported on the swinging tip of the swing arm 102.
8, the swing arm 102 is swung about a rotation shaft 130, and the swinging tip of the swing arm 102 is swung in the direction of arrow S, thereby allowing the objective of the magneto-optical head 128 to be swung. Lens 108 and S
The IL lens 109 can be moved in the radial direction of the recording medium 112.

According to such a configuration, in a state where the laser beam is focused on the recording surface of the recording medium 112, the swing arm 102 is swung about the rotation shaft 130,
By moving the magneto-optical head 128 along the radial direction of the recording medium 112, the spot position of the laser beam with respect to the recording surface of the recording medium 112 is coarsely adjusted (coarse tracking control), and at the same time, the galvanomirror 106 is moved by the arrow. By rotating the recording medium 112 in the R direction,
The spot position of the laser beam with respect to the recording surface is finely adjusted (finely tracking control).

During such coarse and fine tracking control, the laser light emitted from the light source 104 is transmitted to the light guide optical system 114 and the galvanomirror 10.
6 irradiates the reflecting mirror 132 through the imaging lens 110, and then the reflecting mirror 132
The light is condensed along tracks formed on the recording surface of the recording medium 112 via the 28 objective lenses 108 and the SIL lens 109. As a result, optical recording or optical reproduction of information on the recording surface of the recording medium 112 is performed.

The above-described magneto-optical pickup 100 has a structure in which the position of the collimator lens 116 is taken into consideration so as to reduce the defocus caused by a change in temperature.

For example, FIG. 4 shows an infinity optical system (light source 104, collimator lens 116, objective lens 108, SIL lens 109) which is a main component of the magneto-optical pickup 100 shown in FIGS. ing. In such an infinite optical system, the magneto-optical pickup 100
When the internal temperature changes due to the environment (for example, changes from 5 ° C. to 60 ° C.), the position between the SIL lens 109 and the recording medium 112 changes due to a change in the position of optical components other than the collimator lens 116 and a change in optical characteristics. Focus shift (defocus) occurs. That is, the focus position (0) is shifted by a predetermined amount (defocus amount) Δf in the recording medium 112 direction (+ direction) or in the direction away from the recording medium 112 (− direction).

In this case, the change in the position of the optical component and the change in the optical characteristics include, for example, a change in the distance between the objective lens 108 and the SIL lens 109 that are integrally positioned and fixed to the magneto-optical head 128, and a change in the SIL lens. 109, a change in the radius of the objective lens 108 (a change in the refractive index, a change in the surface curvature, a change in the thickness, etc.);
Working distance (from the lowermost surface of the objective lens 108 to the recording medium 1)
Change in the distance to 12).

Therefore, the magneto-optical pickup 100 according to the present embodiment uses the collimator lens 1 with respect to the light source 104 so as to reduce the defocus amount Δf as described above.
It is configured in consideration of 16 bonding positions.

First, the shift direction (+ direction,-direction) of the defocus amount Δf is determined in advance by simulation. For example, when the in-focus position (0) at the time of temperature rise shifts in the + direction, the bonding position of the collimator lens 116 is set to the light source 104 side (first setting structure) so as to reduce this defocus. On the other hand, when the focus position (0) at the time of temperature rise shifts in the negative direction, the bonding position of the collimator lens 116 is set on the opposite side to the light source 104 so as to reduce this defocus (second setting). Construction).

FIG. 3A shows a configuration for realizing the first setting structure. The support 200 supports the light source 104, and the support 200 is attached to the support 200 and the light source 104 is energized. A frame 204 for holding the collimator lens 116, and a holder 206 attached to the support 200 and holding the lens frame 204 so as to be adjustable in the optical axis A direction.

An abutting portion 204a is protrudingly provided on the lens frame 204 on the light source 104 side.
Can be fixed in a state where the portion on the light source 104 side is applied to the attaching portion 204a via an adhesive (for example, an ultraviolet curable adhesive). In this case, when a collimator lens 116 having one flat surface and the other convex shape as shown in FIG. 3A is used, the flat portion is fixed to the abutting portion 204 a of the lens frame 204. . On the other hand, when a collimator lens having a convex shape on both sides is used, the convex portion on the light source 104 side may be fixed to the abutting portion 204a.

The light source 10 of the collimator lens 116
The bonding position at which the portion on the fourth side is bonded to the abutment portion 204a is not limited to the bonding position indicated by reference numeral P1 in FIG.
The adhesive may be applied over the entire circumference of the applied portion applied to the, or the adhesive may be applied at positions where the entire circumference of the applied portion is equally divided (for example, into three equal parts). May be.

The mirror frame 204 is provided with the abutting portion 204 described above.
In addition to the light source 10 a, the holding unit 204 b holding the periphery of the collimator lens 116 extends along the optical axis A direction.
4, and extends in a direction away from the predetermined bonding position P
By applying an adhesive (for example, an ultraviolet curable adhesive or the like) to the second holding member 204b (the lens frame 2) at a position (a position separated from the light source 104 with respect to the collimator lens 116).
04) can be fixed to the holder 206.

In this case, the holding portion 204b is
Is not limited to the bonding position indicated by reference numeral P2 in FIG. 3A, and the adhesive may be applied over the entire circumference including P2. An adhesive may be applied to the position equally divided (for example, divided into three) over the entire circumference.

According to such a first setting structure, the light source 104 of the collimator lens 116 at the bonding position P1
The light source 104 and the collimator lens 11 are arranged such that the light from the collimator lens 116 becomes a parallel light beam while the side portion is fixed to the contact portion 204a of the lens frame 204 with an adhesive.
6 is adjusted. Then, after adjusting the position of the collimator lens 116 by moving the lens frame 204 along the direction of the optical axis A so that the defocus amount Δf in the + direction caused by the temperature change is reduced, the bonding position is adjusted. At P2, the lens frame 204 is fixed to the holder 206. At this time, since the position of the light source 104 is farther outward than the focal position of the collimator lens 116, the light emitted from the collimator lens 116 becomes divergent light, and the vertical direction of the collimator lens 116, the objective lens 108, and the SIL lens 109. Considering the magnification (to be described later), the magneto-optical pickup 100 having the infinite optical system (see FIG. 4) in which the defocus amount Δf in the + direction is reduced is realized.

A specific description will be given with reference to FIG.

Here, the focal length of the collimator lens 116 is f1, the defocus amount due to a temperature change is Δf1, the focal length of the combined objective lens 108 and SIL lens 109 is f2, the defocus amount due to the temperature change is Δf2, SI
The refractive index of the L lens 109 is n1, and the vertical magnification α is (f
2 / f1) ² , the defocus amount Δf on the SIL lens 109 is as follows: Δf = (α · Δf1 / n1) + Δf2 = (Δf1 / n1) · (f2 / f1) ² + Δf2

Here, the numerical aperture is 0.65 and the effective diameter is 2 m
m, the focal length f2 is 1.
54, and SF for the light source 104 having a wavelength of 650 nm.
When the SIL lens 109 made of S1 (squirt) is used, the refractive index n1 becomes 1.91. When the temperature changes from 20 ° C. to 60 ° C., the defocus amount Δf2 becomes +0.3 μm.
m / 40 ° C.

In this case, the condition for setting the defocus amount Δf in the + direction to zero is as follows: Δf = (Δf1 / 1.91) · (1.54 / f1) ² + 0.3 = 0 Δf1 / f1 ² = −0.242 (1) In the expression (1), the relationship of Δf1 <0 means that the light emitted from the collimator lens 116 becomes divergent light. Therefore, the light source 104 of the collimator lens 116 is attached at the bonding position P1 so as to satisfy the expression (1).
The side portion is fixed to the abutting portion 204a of the lens frame 204 with an adhesive, and the lens frame 204 is fixed to the holder 206 at the bonding position P2 in consideration of the relative relationship between Δf1 and f1. In the optical system at infinity in FIG. 4, f1 = about 2 to 4 and Δf1 = −2.0 / 40 ° C. In this case, f
By using the collimator lens 116 of 1 = 2.87,
The defocus amount Δf on the SIL can be reduced to a value close to zero as much as possible.

FIG. 3B shows a structure for realizing the second setting structure. This structure is basically the same as the above-described first setting structure. In the description, only the differences will be described.

In this second setting structure, the mirror frame 204
Has an abutting portion 204 a ′ protruding from a side opposite to the light source 104 (a position farthest from the light source 104), and the collimator lens 116 uses an adhesive (for example, , An ultraviolet-curable adhesive or the like) and can be fixed in a state of being applied to the abutting portion 204a '. In this case, as shown in FIG. 3B, one of the collimator lenses 11 is flat and the other is convex.
When 6 is used, the convex portion is fixed to the abutting portion 204a 'of the lens frame 204 in a state where it is abutted. On the other hand, when a collimator lens having a convex shape on both sides is used, the convex portion opposite to the light source 104 is attached to the abutting portion 204.
a 'may be fixed.

The light source 10 of the collimator lens 116
The bonding position where the part on the fourth side is bonded to the abutting portion 204a 'is not limited to the bonding position indicated by the reference numeral P1 in FIG.
The adhesive may be applied over the entire circumference of the applied portion applied to a ′, or the adhesive may be applied to a position obtained by equally dividing the entire circumference of the applied portion (for example, into three equal parts). It may be applied.

The mirror frame 204 is provided with the abutting portion 204 described above.
In addition to the light source 1, the holding portion 204 b holding the periphery of the collimator lens 116 extends along the optical axis A in addition to the light source 1.
04 toward the predetermined bonding position P2
An adhesive (for example, an ultraviolet-curable adhesive or the like) is applied to a position (a position further away from the light source 104 than the collimator lens 116).
Is applied, the holding portion 204b (the mirror frame 20)
4) can be fixed to the holder 206.

In this case, the holder 204b is
Is not limited to the bonding position indicated by reference numeral P2 in FIG. 3B, and the adhesive may be applied over the entire circumference including P2, or An adhesive may be applied to the position equally divided (for example, divided into three) over the entire circumference.

According to the second setting structure, the light source 104 of the collimator lens 116 at the bonding position P1
The opposite side of the mirror frame 204 is bonded to the abutting portion 204 with an adhesive.
The position relationship between the light source 104 and the collimator lens 116 is adjusted so that the light from the collimator lens 116 becomes a parallel light beam in the state where the light source 104 is fixed to a ′. After adjusting the position of the collimator lens 116 by moving the lens frame 204 along the direction of the optical axis A so as to reduce the defocus amount Δf in the − direction due to the temperature change, Δf1 and The lens frame 204 is fixed to the holder 206 at the bonding position P2 while considering the relative relationship of f1. At this time, since the position of the light source 104 is more inward than the focal position of the collimator lens 116, the light emitted from the collimator lens 116 is converged light (Δf1 <0).
As a result, it is possible to realize the magneto-optical pickup 100 having the infinity optical system (see FIG. 4) in which the defocus amount Δf in the negative direction is reduced (reduced to a value as close to zero as possible).

In the above-described embodiment, the magneto-optical pickup 100 of the type in which the magneto-optical head 128 is arranged on the swing arm 102 and the magneto-optical head 128 swings has been described. However, the present invention is not limited to this. And a magneto-optical pickup 10 of a type in which a magneto-optical head 128 is moved in parallel and linearly along the recording medium 112.
Needless to say, the technology of the present invention can be applied to 0.

[0044]

According to the present invention, it is possible to provide a magneto-optical pickup capable of adjusting the position of a collimator lens so as to reduce the defocus caused by a temperature change.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a magneto-optical pickup according to an embodiment of the present invention.

FIG. 2 is a diagram showing a state in which the magneto-optical pickup shown in FIG. 1 is arranged on a swing arm.

FIG. 3A is a diagram illustrating a configuration for realizing a first setting structure, and FIG. 3B is a diagram illustrating a configuration for realizing a second setting structure.

FIG. 4 is a diagram showing a configuration of an infinite optical system of the magneto-optical pickup.

5A is a diagram showing a configuration of a conventional magneto-optical pickup, and FIG. 5B is a diagram showing a configuration of a magneto-optical head.

[Explanation of symbols]

 104 light source 116 collimator lens 204 mirror frame 204a, 204a '

Claims (5)

[Claims] 1. A light source, a collimator lens for collimating laser light emitted from the light source, a near-field optical element for condensing the laser light emitted from the light source toward a recording medium, and a magnetic field generating coil Magneto-optical pickup comprising: a magneto-optical head having: a support for supporting a light source; a mirror frame for holding a collimator lens; and a holder attached to the support and holding the mirror frame so as to be adjustable in the optical axis direction. 2. The magneto-optical pickup according to claim 1, wherein the collimator lens has a light source side portion fixed to a lens frame with an adhesive. 2. A light source, a collimator lens for collimating laser light emitted from the light source, a near-field optical element for condensing the laser light emitted from the light source toward a recording medium, and a magnetic field generating coil Magneto-optical pickup comprising: a magneto-optical head having: a support for supporting a light source; a mirror frame for holding a collimator lens; and a holder attached to the support and holding the mirror frame so as to be adjustable in the optical axis direction. 3. The magneto-optical pickup according to claim 1, wherein the collimator lens has a portion opposite to the light source fixed to the lens barrel with an adhesive. 3. An abutting portion protrudes from the lens frame on the light source side, and the collimator lens has a light source side portion fixed to the abutting portion of the lens frame with an adhesive. 2. The magneto-optical pickup according to claim 1, wherein: 4. The mirror frame is provided on a side opposite to the light source,
3. The magneto-optical device according to claim 2, wherein an abutting portion is protruded, and a portion of the collimator lens opposite to the light source is fixed to the abutting portion of the lens frame with an adhesive. pick up. 5. The light according to claim 1, wherein the mirror frame is fixed to a holder with an adhesive at a position farther from the light source than the collimator lens. Magnetic pickup