JP2000353346A - Optical head and optical recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve access speed by reducing the weight of an electromagnetic coil for impressing a magnetic field. SOLUTION: This optical head is constituted such that a solid immersion lens 12 (the lens) is provided at a position close to the recording film 2a of a magneto-optical disk 2 and that, above the lens 12, an objective lens 13 converging on the lens 12 the recording and reproducing light emitted from a light source is provided. In addition, in the lens 12, a vertically extending magnetic material rod 18 is provided, an electromagnetic coil 17 for impressing a magnetic filed is installed at a position surrounding at least a part of the magnetic material rod 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus for recording / reproducing information on / from a recording medium by light and an optical head used for the optical recording / reproducing apparatus.

[0002]

2. Description of the Related Art Heretofore, there is an apparatus for recording / reproducing information on / from a recording medium using light, which utilizes a magneto-optical change of a recording film provided on the recording medium. In such an apparatus, recording is performed by externally applying a magnetic field to a portion of the recording film heated to a temperature higher than the Curie point by irradiating a laser beam and inverting the magnetization of the portion, thereby generating reflected light due to the magnetic Kerr effect. Reproduction is performed by detecting the rotation of the polarization angle.

In such an optical recording / reproducing apparatus, in order to increase the recording density and increase the recording capacity of a recording medium, it is necessary to reduce the diameter of a laser spot formed on a recording film. Here, the focused spot diameter is K ·
λ / NA (λ: light wavelength, NA: numerical aperture of objective lens,
(K: constant), it is known that the diameter of the condensed spot can be reduced by reducing the light wavelength λ or increasing the NA of the objective lens.
Here, the light wavelength λ is 400 nm with a small semiconductor laser.
Some of them are being put to practical use, but have shortcomings in terms of short life and productivity, and have not yet reached a level that can be incorporated into equipment at present. On the other hand, a solid immersion lens (SIL: Solid Immersion Lens)
In some cases, s) is provided to increase the synthetic NA. According to this, it is possible to increase NA, which is about 0.45 to 0.60 only with the objective lens, to about 1.2 to 1.6.

FIG. 7 shows a configuration example of an optical head using a solid immersion lens. An objective lens 113 and a solid immersion lens 112 are provided in a gap 111a of a slider 111 (illustration of a drive mechanism of the slider 111) provided close to the recording medium 102, and an electromagnetic coil for applying a magnetic field. Is provided so as to surround the periphery of the solid immersion lens 112. The laser light emitted from the light source is focused by the objective lens 113, and a focused spot is formed on the bottom surface of the solid immersion lens. The temperature of the recording film 102a is locally increased by the condensed spot, and information is recorded by applying a magnetic field in a direction perpendicular to the recording film by the electromagnetic coil 117. Here, in the case of a hemispherical solid immersion lens 112 as in the apparatus of FIG.
A is (NA of objective lens) × (refractive index n of solid immersion lens material). Thus, for example, NA = 0.6 and n =
If 2.0, the synthetic NA is 1.2. At this time, the condensed spot diameter with respect to the light wavelength of 630 nm is constant K of 0.6.
If so, it is about 320 nm.

[0005]

By using a solid immersion lens as described above, the diameter of the condensed light spot can be made smaller than before, and the recording density of information can be increased. However, as described above, the combined NA exceeds 1. In this case, the diameter of the condensed spot on the recording film increases rapidly with an increase in the distance between the solid immersion lens and the recording film, and the light intensity also decreases rapidly. This is because, of the light inside the solid immersion lens, those in the area where NA exceeds 1 cause total reflection at the bottom of the solid immersion lens,
This is because the evanescent wave decreases exponentially as it moves downward from the bottom surface.

For this reason, it is necessary to dispose an electromagnetic coil for applying a magnetic field such as a solid immersion lens close to the recording film, and the electromagnetic coil is formed of a solid immersion lens (about 1 mm in diameter) as described above. Since the coil is provided so as to surround the periphery, the coil diameter is much larger than the recording pit width (1 μm or less), and a large current is required to obtain a magnetic field of a required strength. For this reason, the thickness of the electromagnetic coil has to be increased to some extent, and there has been a problem that the optical head itself is enlarged and the access speed is reduced.

The present invention has been made in view of such a problem, and an optical head and an optical recording / reproducing apparatus capable of reducing the weight of an electromagnetic coil for applying a magnetic field, thereby improving an access speed. It is intended to provide a device.

[0008]

In order to achieve the above object, an optical head according to the present invention comprises a light source for emitting recording / reproducing light (for example, a light irradiation device 5 in the embodiment),
A solid immersion lens disposed at a position close to a recording film of a recording medium (for example, the magneto-optical disk 2 in the embodiment); and a solid immersion lens disposed above the solid immersion lens to record and reproduce light from a light source. An objective lens for focusing light, a magnetic rod provided vertically extending in the solid immersion lens, and an electromagnetic coil for applying a magnetic field provided at a position surrounding at least a part of the magnetic rod. Be composed.

In such a configuration, the recording / reproducing light emitted from the light source is condensed on the solid immersion lens by the objective lens, and a condensed spot is formed on the bottom surface of the solid immersion lens. In this state, information can be recorded on the recording film (or the information recorded on the recording surface can be erased) by applying a current to the electromagnetic coil to generate a magnetic field. Since it concentrates on the magnetic rod provided on the side, the current required to obtain the required magnetic field can be made smaller than before. Therefore, the size of the electromagnetic coil (such as the thickness of the coil) can be reduced, and the optical head can be made compact to improve the access speed.

Here, the electromagnetic coil may be provided so as to surround the solid immersion lens. However, if the magnetic rod has a protrusion protruding upward from the upper surface of the solid immersion lens, the electromagnetic coil will It may be provided so as to surround the part. Alternatively, the electromagnetic coil may be provided inside the solid immersion lens.
Further, a projection projecting downward may be formed on the bottom surface of the solid immersion lens so that the lower end of the magnetic rod is located inside the projection, and an electromagnetic coil may be provided so as to surround the projection. It is preferable that the lower end of the magnetic rod is located above the bottom surface of the solid immersion lens at a distance of at least three times the diameter of the magnetic rod. It is possible to prevent the light incident on the immersion lens from being blocked by the magnetic rod, thereby reducing the light use efficiency.

An optical recording / reproducing apparatus according to the present invention has a medium driving mechanism (for example, a spindle motor 1 in the embodiment) for holding and moving a recording medium in a plane, the optical head, and the optical head. The head arm and an arm driving mechanism (for example, the voice coil motor 3 in the embodiment) for driving the head arm so as to move the optical head in a direction intersecting the plane movement direction of the recording medium. In such an optical recording / reproducing apparatus, since the optical head can be made compact as described above, the apparatus itself can be reduced in size and weight.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 and 2 show an optical recording / reproducing apparatus provided with an optical head according to a first embodiment of the present invention. This optical recording / reproducing apparatus records data on a magneto-optical disk 2 which is rotated by a spindle motor 1. An optical head 10 positioned close to the film 2a, a head arm 4 for holding the optical head 10, a voice coil motor 3 for rotating the head arm 4, and a recording / reproducing laser beam And a light irradiation device 5.

The optical head 10 includes a slider 11. The slider 11 is located on the recording film 2a on the rotating magneto-optical disk 2 and floats by a certain minute distance from the recording film 2a by an air bearing effect. (Ie, constitute a flying head). Head arm 4
Is a rotary shaft 4a connected to the voice coil motor 3 and driven to rotate, an arm 4b extending horizontally from the upper end of the rotary shaft 4a, and an optical head 1 at the tip of the arm 4b.
And a suspension portion 4c that supports the vertical movement of the suspension portion 4c. Voice coil motor 3
When the rotation shaft 4a is driven to rotate, the arm portion 4b swings horizontally and moves the optical head 10 in a direction substantially perpendicular to the rotation direction of the magneto-optical disk 2 (the direction of arrow A in FIG. 2). The optical head 10 scans on the recording film 2a of the magneto-optical disk 2. That is, tracking control is performed by the voice coil motor 3.

A circular tapered space 11a extending upward is formed in the slider 11 of the optical head 10.
A solid immersion lens 12 made of a glass material is provided below the gap 11a, and an objective lens 13 also made of a glass material is provided above the gap 11a. A microprism 15 is provided above the slider 11 with a spacer 14 interposed therebetween, and a high reflection film 16 is provided on a reflection surface 15a thereof. This micro prism 1
Reference numeral 5 is connected to the suspension section 4c of the head arm 4 via the fine movement actuator 20. The space 11a may be filled with a transparent or light-transmitting material.

As shown in FIG. 3, an electromagnetic coil 17 for applying a magnetic field is provided outside the solid immersion lens 12.
Is provided so as to surround. Here, the center axis of the electromagnetic coil 17 coincides with the optical axes of the objective lens 13 and the solid immersion lens 12. A vertically extending magnetic rod 18 is embedded in the solid immersion lens 12, and at least a part of the magnetic rod 18 is surrounded by the electromagnetic coil 17 (the magnetic rod 18). At least a portion is located inside the electromagnetic coil 17).
The center axis of the magnetic rod 18 also coincides with the optical axis. The diameter of the magnetic rod 18 is 0.5 m for the thickness of the solid immersion lens 12.
If it is about m, it is preferable to be about 0.1 mm. In this case, the magnetic rod 18 is press-fitted into a hole having a diameter of about 0.1 mm formed in the upper center of the solid immersion lens 12. Preferably, the electromagnetic coil 17 is wound with a radius as small as possible.

Here, the lower end of the magnetic rod 18 is preferably located above the bottom surface of the solid immersion lens 12 at a distance of at least three times the diameter of the magnetic rod 18 (the solid immersion lens 12 and the magnetic immersion lens 12). 0.3m if body rod 18 is the above size
m). This is to prevent the light condensed on the solid immersion lens 12 from being blocked by the magnetic rod 18 and reducing the light use efficiency. Further, it is more effective if the lower end of the magnetic rod 18 is sharpened.

FIG. 4 shows the fine movement actuator 20 in an enlarged manner. The fine movement actuator 20 is of a parallel plate type, and specifically has a fixed block 23 and a movable block 24 provided on a first substrate 21 joined to the suspension part 4c.
4 has a large number of parallel flat plates extending parallel to each other. By applying a voltage between these parallel flat plates to actuate electrostatic force, the movable block 24 is finely moved relative to the fixed block 23 in a direction perpendicular to the parallel flat plate (the direction of arrow B) to provide fine and highly accurate movement control. Is available.

The movable block 24 is further joined to the microprism 15 via the flat plate portion 22. Therefore, if a voltage is applied between the parallel flat plates to finely move the movable block 24, the movable block 24 is moved relative to the suspension portion 4c. The optical head 10 can be slightly moved in the direction of arrow B. The direction of the arrow B is the same as the moving direction A for scanning the optical head 10 by the voice coil motor 3.

A reflection mirror 6 is disposed on the rotation shaft 4a of the head arm 4 so as to be obliquely opposed to the light irradiation device 5.
The recording / reproducing laser light emitted from the light irradiation device 5 is reflected by the reflection mirror 6 and guided to the microprism 15 as shown by chain lines R1 and R2 in FIGS.
The recording / reproducing laser beam guided to the microprism 15 in this manner is reflected by the reflection surface 15a of the microprism 15.
After being reflected by the high-reflection film 16, the light is condensed by the objective lens 13 so as to be narrowed down to the diffraction limit and is incident on the solid immersion lens 12. A small condensed spot (the condensed spot diameter is several hundred nm) is formed.

The operation of the optical recording / reproducing apparatus having the above configuration will be described. First, the magneto-optical disk 2 is rotated at a predetermined speed by the spindle motor 1. At this time, the optical head 10 supported by the suspension portion 4c of the head arm 4 and disposed on the recording film 2a on the upper surface of the magneto-optical disk 2
Means that the slider 11 has the recording film 2
It floats by a very small distance from a. When the recording / reproducing laser beam is irradiated from the light irradiation device 5 in this state, this light is reflected by the reflecting mirror 6 and enters the microprism 15 as indicated by chain lines R1 and R2. Then, after being reflected by the reflecting surface 15a of the microprism 15, the light is condensed by the objective lens 13 and enters the solid immersion lens 12 to be focused. As a result, a focused spot is formed on the bottom surface of the solid immersion lens 12.

Here, since the magneto-optical disk 2 is driven at a constant speed, the flying height of the slider 11 is always constant, and therefore, the distance between the recording film 2a of the magneto-optical disk 2 and the bottom surface of the solid immersion lens 12 is high. The distance is always kept at an appropriate value. For this reason, the condensed spot can be always positioned on the recording film 2a of the magneto-optical disk 2, and it is not necessary to provide a focusing mechanism as in the conventional case.

The temperature of the portion of the recording film 2a where the condensed light spot is applied locally rises, but when a magnetic field is applied from the outside while the temperature is raised to a temperature higher than the Curie point, the magnetization of that portion is reversed. Then, the information is recorded (or erased). The application of the magnetic field is performed by energizing the electromagnetic coil 17, but the direction of the applied magnetic field can be switched by changing the direction of the energizing current.
The direction of the applied magnetic field (generated by the electromagnetic coil 17) is perpendicular to the recording film 2a. on the other hand,
A device for detecting the magnetic Kerr effect is used for reproducing information, and such an optical recording / reproducing device is also provided with such a device. However, since these devices are well known, illustration and description thereof are omitted.

The recording and reproduction of such information is performed by moving (scanning) the optical head 10 in the radial direction of the magneto-optical disk 2 in accordance with the rotation of the magneto-optical disk 2. Scanning or tracking is performed by rotating the head arm 4 by the voice coil motor 3 arranged at the root of the head arm 4. However, here, the voice coil motor 3 is used as a coarse movement servo, and controls a relatively low-speed component of the head arm 4. That is,
Since the precision of tracking control by the voice coil motor 3 is limited and fine tracking control is difficult, this is used for coarse motion servo control.
This is performed by applying a fine movement servo with 0.

As described above, the recording surface 2a of the recording medium 2
When information is recorded on the recording medium 2 (or when information recorded on the recording surface 2a is erased), the electromagnetic coil 17 is energized to generate a magnetic field. Since the magnetic rod 18 is provided on the magnetic member 18, the magnetic field generated in the electromagnetic coil 17 can be concentrated on the magnetic rod 18. That is, when the magnetic rod 18 is not used, the magnetic field is uniformly distributed over almost the entire area surrounding the electromagnetic coil 17. (Relative permeability) times. As a result, the current required to obtain a required magnetic field can be made smaller than before, so that the size of the electromagnetic coil 17 (such as the thickness and number of turns of the coil) can be reduced, and the optical head 10 can be made compact. Access speed can be improved.
The material of the magnetic rod 18 is preferably a material having a large magnetic permeability μ, among which Sendust, Permalloy, Supermalloy, and Mumet.
al is preferred.

FIGS. 5 to 7 show the configuration near the solid immersion lens 12 in the optical head according to the second to fourth embodiments of the present invention. The optical recording / reproducing apparatus according to the second to fourth embodiments differs from the optical recording / reproducing apparatus according to the first embodiment only in the manner in which the solid immersion lens 12, the magnetic rod 18, and the electromagnetic coil 17 are provided. Therefore, description of other common parts is omitted.

In the optical head according to the second embodiment of the present invention shown in FIG. 5, the magnetic rod 18 has a protruding portion 18a protruding upward from the upper surface of the solid immersion lens 12. The coil 17 is provided so as to surround the projection 18a. Also in this case, it is preferable that the electromagnetic coil 17 is wound with a radius as small as possible. In such a configuration, the coil diameter of the electromagnetic coil 17 can be reduced, and since the magnetic rods 18 are located in the entire area of the electromagnetic coil 17, a large magnetic field can be obtained with a smaller current. The weight of the head 10 can be further reduced. Also in this case, it is preferable that the lower end of the magnetic rod 18 is kept at least three times the diameter of the magnetic rod 18 away from the bottom surface of the solid immersion lens 12, and the lower end of the magnetic rod 18 is sharpened. As in the first embodiment, it is possible to more effectively prevent light from being blocked (the same applies to the third and fourth embodiments described below).

In the optical head according to the third embodiment of the present invention shown in FIG. 6, the electromagnetic coil 17 is provided inside the solid immersion lens 12 and surrounds the magnetic rod 18. here,
The encapsulation of the magnetic rod 18 and the electromagnetic coil 17 in the solid immersion lens 12 is as follows: (A) When the solid immersion lens 12 is manufactured by molding, the magnetic rod 18 in a state in which the electromagnetic coil 17 is wound.
Or (B) the upper and lower parts of the solid immersion lens 12 are separately manufactured, and holes are formed in the center of these upper and lower parts, and the magnetic rod 1 around which the electromagnetic coil 17 is wound.
The upper and lower parts are bonded or fused while sandwiching 8 between both holes. In such a configuration, the coil diameter can be reduced as in the second embodiment, and the electromagnetic coil 17 can be brought closer to the magnetic rod 18, so that the current required to generate a magnetic field is reduced. Can be further reduced.

In the optical head according to the fourth embodiment of the present invention shown in FIG. 7, a projection 12a projecting downward is formed on the bottom surface of the solid immersion lens 12, and the lower end of the magnetic rod 18 is formed by the projection. It is located inside the part 12a. The electromagnetic coil 17 is provided so as to surround the protrusion 12a. In such a configuration, the mounting of the electromagnetic coil 17 is easier than in the case of the third embodiment, and the magnetic field can be used efficiently because the electromagnetic coil 17 is located closer to the magnetic rod 18. Yes, electromagnetic coil 1
7 can be reduced.

FIG. 8 shows a modification of the fourth embodiment. This uses a glass member 212 provided with a reflective film 212a on the outer surface instead of the solid immersion lens 12 (this may be referred to as a solid immersion mirror), and is provided to protrude downward from the bottom surface. Projection 2
An electromagnetic coil 17 is provided so as to surround 12b. Such a glass member 212 is used for the solid immersion lens 1.
Since the same effects as in the second embodiment are exhibited, the same effects as in the case of the fourth embodiment can be obtained.

Although the embodiments of the optical head according to the present invention and the optical recording / reproducing apparatus provided with the same have been described above, the scope of the present invention is not limited to the above. For example,
The optical head according to the present invention can be mounted not only on the optical recording / reproducing apparatus having the above configuration, but also on an optical recording / reproducing apparatus having another configuration.

[0031]

As described above, the optical head according to the present invention comprises: a light source for emitting recording / reproducing light; a solid immersion lens disposed at a position close to a recording film of a recording medium; An objective lens disposed on the upper side of the recording and reproducing light from the light source to focus the solid immersion lens, a magnetic rod extending vertically in the solid immersion lens, and at least a part of the magnetic rod. Since it is configured to have a magnetic field applying electromagnetic coil provided at the surrounding position, the magnetic field generated in the electromagnetic coil can be concentrated on the magnetic rod, and the required magnetic field can be reduced with a smaller current than before. Obtainable. Therefore, the size of the electromagnetic coil (such as the thickness of the coil) can be reduced, and the optical head can be made compact to improve the access speed.

Here, the electromagnetic coil may be provided so as to surround the solid immersion lens. However, if the magnetic rod has a projection projecting upward from the upper surface of the solid immersion lens, the electromagnetic coil will It may be provided so as to surround the part. Alternatively, the electromagnetic coil may be provided inside the solid immersion lens.
Further, a projection protruding downward may be formed on the bottom surface of the solid immersion lens so that the lower end of the magnetic rod is located inside the projection, and an electromagnetic coil may be provided so as to surround the projection. It is preferable that the lower end of the magnetic rod is located above the bottom surface of the solid immersion lens at a distance of at least three times the diameter of the magnetic rod. It can be prevented that the used light is blocked by the magnetic rod and the light use efficiency is reduced.

Further, an optical recording / reproducing apparatus according to the present invention comprises a medium drive mechanism for holding a recording medium and moving it in a plane, the optical head, a head arm for holding the optical head,
An arm drive mechanism for driving the head arm so as to move the optical head in a direction intersecting with the plane movement direction of the recording medium. In such an optical recording / reproducing apparatus, since the optical head can be made compact as described above, the apparatus itself can be reduced in size and weight.

[Brief description of the drawings]

FIG. 1 is a schematic front view showing a configuration of an optical recording / reproducing apparatus including an optical head according to a first embodiment of the present invention.

FIG. 2 is a schematic plan view showing a configuration of the optical recording / reproducing apparatus.

FIG. 3 is an enlarged side view showing the vicinity of a solid immersion lens in the optical recording / reproducing apparatus.

FIG. 4 is a perspective view showing a fine movement actuator constituting the optical recording / reproducing apparatus.

FIG. 5 is an enlarged side view showing the vicinity of a solid immersion lens in an optical recording / reproducing apparatus including an optical head according to a second embodiment of the present invention.

FIG. 6 is an enlarged side view showing the vicinity of a solid immersion lens in an optical recording / reproducing apparatus including an optical head according to a third embodiment of the present invention.

FIG. 7 is an enlarged side view showing the vicinity of a solid immersion lens in an optical recording / reproducing apparatus including an optical head according to a fourth embodiment of the present invention.

FIG. 8 is an enlarged side view showing the vicinity of a solid immersion lens in a modification of the optical recording / reproducing apparatus including the optical head according to the fourth embodiment of the present invention.

FIG. 9 is a schematic side view showing a part of an optical recording / reproducing apparatus provided with a conventional optical head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Spindle motor (medium drive mechanism) 2 Magneto-optical disk (recording medium) 2a Recording film 3 Voice coil motor (arm drive mechanism) 4 Head arm 5 Light irradiation device (light source) 10 Optical head 11 Slider 12 Solid immersion lens 13 Objective lens 17 Electromagnetic coil 18 Magnetic rod

Claims (4)

[Claims] A light source for emitting recording / reproducing light; a solid immersion lens disposed at a position close to a recording film of a recording medium; and a recording / reproduction from the light source disposed above the solid immersion lens. An objective lens for condensing light on the solid immersion lens; a magnetic rod extending vertically in the solid immersion lens; and a magnetic field application provided at a position surrounding at least a part of the magnetic rod. An optical head, comprising: an electromagnetic coil. 2. The solid-state imaging device according to claim 1, wherein the electromagnetic coil is provided so as to surround the solid immersion lens.
An optical head according to claim 1. 3. The magnetic rod according to claim 2, wherein the magnetic rod has a protrusion protruding upward from an upper surface of the solid immersion lens, and the electromagnetic coil is provided so as to surround the protrusion. Item 2. The optical head according to item 1. 4. A medium drive mechanism for holding a recording medium and moving it in a plane, the optical head according to claim 1, a head arm for holding the optical head, and recording the optical head on the recording medium. An optical recording / reproducing apparatus, comprising: an arm drive mechanism for driving the head arm so as to move the head arm in a direction intersecting with the plane movement direction of the medium.