JP2002269803A - Optical disk device and optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the structure of a floating head and the recording/ reproducing operation with the near-field in an optical disk system by miniaturizing the head having the convergent system such as an objective lens. SOLUTION: Linear polarization laser beams emitted from a semiconductor laser 31 oscillating in multi-mode in a 1st optical system 11 are made incident on a polarization plane maintaining fiber 13 through a polarizing beam splitter 34 and transmitted to a head part 12 while the polarizing state is kept as it is. The linear polarization is converted to the circular polarization by a 1/4 wavelength plate 42, and the information on the surface of the optical disk 1 is detected by using the evanescent wave with a SIL(Solid Immersion Lens) consisting of lenses 43, 44 and the circular polarization is converted to the linear polarization by the 1/4 wavelength plate 42 and transmitted to the 1st optical system 11 through the polarization plane maintaining fiber 13, then detected by a photodiode 37 after being reflected with a polarization beam splitter 34.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical disk device for recording and / or reproducing data on and from an optical disk and an optical pickup device for irradiating and detecting a laser beam on the optical disk.

[0002]

2. Description of the Related Art Optical discs include read-only discs,
Recordable disc (Recordable or
Write Once) disk and re-recordable type (Rewitable)
There is a disk. As a recordable optical disk,
Optical disks of a phase change type, an organic dye type or the like are known.

The recording and / or reproduction of information signals on such an optical disk is performed using an optical disk device having an optical pickup device for writing and / or reading information signals on the optical disk. .

An optical pickup device is disposed so as to face a signal recording surface of an optical disk to be rotated, and the optical pickup device is disposed on a signal recording surface of the optical disk via an objective lens. The light beam is collected and irradiated.

[0005]

Incidentally, in an optical pickup device of an optical disk device, it is desirable to dispose an objective lens close to the optical disk when the NA value is increased in order to increase the recording density of the optical disk.
In particular, in the case of an optical pickup in a so-called near-field optical system that detects information (pits or the equivalent thereof) on the surface of an optical disk using an evanescent wave, a recording / reproducing head using a so-called SIL (Solid Immersion Lens) or the like The distance between the lower surface and the disk surface is, for example, 5
It is necessary to keep it at about 0 nm.

The distance from such a disk surface is 50 nm.
It is conceivable to use a floating head (flying head) used in a hard disk drive as a head for maintaining the head close to the extent. The floating type head is a type in which the head floats and is supported by an air film generated by the rotation of the disk, and is required to be as small as several mm square as the head size.

However, the optical pickup device is
It is composed of a plurality of optical components such as a laser light source, a collimator lens, a beam splitter, a wave plate, an objective lens, and a light receiving element, and it is difficult to combine them into several mm square.

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned circumstances, and is directed to an apparatus for recording and / or reproducing data on a phase-change optical disk or an organic dye-based optical disk. It is an object of the present invention to provide an optical disk device and an optical pickup device that can reduce the size of a head having a system, enable a floating head structure, and enable recording and reproduction using near-field light.

[0009]

In order to solve the above-mentioned problems, an optical disk device according to the present invention is a multi-mode optical disk device that irradiates a laser beam onto an optical disk to record and / or reproduce information signals. A first optical system having a laser light source that oscillates at a speed, a second optical system having a condensing system disposed in close proximity to the optical disk, and a first optical system and a second optical system disposed between the first optical system and the second optical system. And an optical fiber for transmitting light emitted from the laser light source to the light collection system.

In order to solve the above-mentioned problems, an optical pickup device according to the present invention comprises a first optical system having a laser light source that oscillates in multiple modes, and a condensing system arranged in close proximity to the optical disk. Having a second optical system, and an optical fiber disposed between the first optical system and the second optical system, for transmitting light emitted from the laser light source to the condensing system. It is characterized by.

Preferably, the optical fiber is a polarization maintaining fiber. The first optical system includes a light emitting / receiving unit including a laser light source and a light receiving element, and a polarizing beam splitter for separating light emitted from the laser light source and light returned from the optical disc, As a laser light source, use of a semiconductor laser driven by a high-frequency superimposed current may be used. It is preferable that the second optical system has a floating head structure. The second optical system includes a condensing system using near-field light that detects information on the optical disk surface using an evanescent wave, and a linearly-polarized light beam incident from the polarization-maintaining fiber. And a quarter-wave plate for converting the circularly polarized light of the return light from the optical disk into linearly polarized light.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an optical disk device and an optical pickup device according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of an optical disk apparatus to which the present invention is applied. Optical disk 1 used in the optical disk device shown in FIG.
Examples thereof include a phase change type optical disk and an organic dye-based optical disk.

An optical pickup device 10 for recording and / or reproducing information on and from the optical disc 1 includes a first optical system 11 having a laser light source oscillating in multiple modes.
And a head 12 serving as a second optical system having a condensing system such as an objective lens disposed close to the optical disc 1, and between the first optical system 11 and the head (second optical system) 12. And a polarization-maintaining fiber 13 serving as an optical fiber for transmitting light emitted from the laser light source of the first optical system 11 to the light-collecting system of the head 12 as a second optical system.
And is configured.

That is, in the optical disk apparatus shown in FIG. 1, a head (second optical system) 12 serving as a recording / reproducing head for irradiating light to the optical disk 1 and receiving return light, and a laser. It is configured as a part separate from the first optical system 11 having a laser light source that emits light and a light detection element that detects light. These heads (second optical system) 12 and first optical system 11
Optically coupled by an optical path of a polarization maintaining fiber 13 which is an optical fiber.

In the optical disk apparatus shown in FIG. 1, a head (second optical system) 12 supported by a support spring 2 of a rotating arm portion is used as a head moving means, for example, a voice coil motor (VCM) 3. Optical disk 1
The information is recorded and / or reproduced by being moved substantially in the radial direction. The first optical system 11, the head (second optical system) 12, the polarization maintaining fiber (optical fiber)
13, a spindle motor 5 for rotating and driving the optical disc 1, a motor drive circuit 6, and a coarse movement drive circuit 7 for controlling the drive of the voice coil motor 3
a, a fine drive circuit 7b for finely moving the condensing system in the second optical system 12 by a piezoelectric element or the like, and an actuator control for controlling the coarse drive circuit 7a and the fine drive circuit 7b. A position detection circuit 4 for detecting a head position which is a position of the second optical system 12;
And a disk controller 9.

The voice coil motor 3 includes a support spring 2 having a head 12 serving as the second optical system provided at a tip thereof.
The head 12 is moved in a substantially radial direction of the optical disk 1 by rotating a rotating arm portion including the voice arm motor 3.
a.

The head 12 serving as the second optical system is configured as, for example, a flying head having a slider structure that is opposed to and close to the optical disc 1.

More specifically, for example, as shown in FIG. 2, a head 12 serving as a second optical system has a slider 21 facing the optical disk 1 and a slider 21 attached to the slider 21 so as to face the optical disk 1. It has a first lens 22 and a second lens 23 that faces the optical disc 1 with the first lens 22 interposed therebetween. The head 12 includes a reflecting mirror 24 for changing the direction of light entering or exiting the second lens 23 to a substantially right angle, a reflecting mirror 24, and the reflecting mirror 24.
And a third lens 25 disposed between the optical fibers 13 facing each other.

The head (second optical system) 1 shown in FIG.
The second first lens 22 and the second lens 23 constitute a combined lens for utilizing an evanescent wave in near-field optics, a so-called SIL (Solid Immersion Lens). The surface of the first lens 22 facing the optical disc 1 is maintained at 100 nm or less, for example, about 50 nm with respect to the optical disc 1.

That is, in the present embodiment, the optical disc 1
It is assumed that an optical disk device applied to an optical disk system using near-field light, such as detecting information on a recording surface (pits or the equivalent thereof) using an evanescent wave, is used in such an optical disk system. In order to detect an evanescent wave, it is necessary to maintain the distance between the lower surface of the head 12 and the surface of the optical disk 1 at about 50 nm. For this reason, in the present embodiment, as shown in FIG. 2, a floating head (flying head) structure similar to that of a so-called hard disk device is adopted, and the air flow generated by the rotation of the optical disk 1 causes the lower surface of the slider 21 to move. By entering the air film, a stable flying height can be obtained, and the distance between the lower surface of the first lens 22 and the surface of the optical disc 1 is set to 50, for example.
It is possible to stably maintain it at about nm.

The flying type head having the structure shown in FIG. 2 is a head 1 used in the present embodiment.
2 is a specific example, and the present invention is not limited to the specific example of this embodiment. Further, the optical system of the present invention,
The present invention is not limited to an optical system using a near field, and is applicable to an optical system based on a far field.

Next, a specific example of an optical pickup device according to an embodiment of the present invention will be described with reference to FIG. Here, the optical pickup device is provided with a first optical unit 13 serving as a light emitting / receiving unit, a second optical system 2 serving as a recording / reproducing head unit having a light condensing system disposed close to an optical disc, and a first optical unit. The optical fiber 12 that optically couples the unit 13 and the second optical system 2 will be described in the order in which light is transmitted.

The optical pickup device shown in FIG.
As the first optical system 11, a semiconductor laser 31 serving as a laser light source, a collimator lens 32 configured to collimate light emitted from the semiconductor laser 31, and a collimator lens 3
Anamorphic prism 33 for shaping light from 2
A polarizing beam splitter (PBS) 34 on which light emitted from the anamorphic prism 33 is incident, and a front monitor photodiode 35 for detecting light partially reflected by the polarizing beam splitter 34. Further, it has a photodiode 37 for receiving, via a lens 36, return light from the optical disk reflected by the polarization beam splitter 34.

The laser light emitted from the semiconductor laser 31 is collimated by a collimator lens 32 into parallel rays, and then shaped by an anamorphic prism 33. The optical system is set so that the light emitted from the anamorphic prism 33 becomes linearly polarized light having a vibrating surface in a direction parallel to the paper surface. Splitter 34
Can pass through. If a front monitor for laser power control is required, the setup may be performed with the tilt plane of the linearly polarized light slightly inclined.

The laser beam that has passed through the polarizing beam splitter 34 is incident on one end face of the polarization maintaining fiber (PMF) 13 via a condenser lens 38. As described later, the incident laser light is propagated while maintaining the polarization state by entering the polarization plane so as to be parallel to the optical axis (fast axis or slow axis) of the polarization plane preserving fiber 13. The light is emitted from the other end face of the polarization maintaining fiber 13.

The light emitted from the polarization maintaining fiber 13 is
After being incident on the collimator lens 41 of the head 12 which is a second optical system having a condensing system, and converted into parallel light again,
The light enters the wavelength (λ / 4) plate 42 and is converted into linearly polarized light. The circularly-polarized laser light from the quarter-wave plate 42 is transmitted to the S
It is incident on an IL (Solid Immersion Lens). These lenses 43 and 44 correspond to the lenses 23 and 22 in the floating head structure using the slider of FIG. 2, and the distance between the disk facing surface of the lens 44 and the surface of the optical disk 1 is, for example, about 50 nm. Is maintained. The laser light incident on such an SIL is condensed on the bottom surface (disc-facing surface) of the lens 44, coupled to the surface of the optical disk 1 via an evanescent wave, and after reading data, again via the SIL. The light is incident on the 波長 wavelength plate 42. When passing through the quarter-wave plate 42 on this return path, the circularly polarized light is converted into linearly-polarized light, but the oscillation direction of the linearly-polarized light emitted from the quarter-wave plate 42 is incident on the quarter-wave plate 42. Is orthogonal to the vibration direction of the linearly polarized light. The laser light emitted from the 波長 wavelength plate 42 enters the polarization plane preserving fiber 13 via the collimator lens 41, propagates while maintaining the changed state, and returns to parallel light via the condenser lens 38. Then, the light is incident on the polarization beam splitter 34. The laser light incident on the polarization beam splitter 34 is linearly polarized light having a vibration plane in a direction orthogonal to the paper surface, is reflected without loss of light amount, and is reflected through a lens 36 to a light detecting means or a light receiving means. The light is incident on a photodiode 37 as an element.

As described above, the first optical system 11 and the head (second optical system) 12 are optically connected by the polarization-maintaining fiber 13, and the １２ wavelength plate 42 is used for the head 12. In principle, an optical system having no light quantity loss can be constructed, and stable circularly polarized incident light can be supplied to the surface of the optical disc 1.

The polarization maintaining fiber 13 used in this embodiment will be described. In general, a polarization maintaining fiber is used as an optical fiber when it is necessary to transmit incident light while maintaining the polarization state. The polarization-maintaining fibers are fast axes that are orthogonal to each other.
/ Slow axis (slow axis) is an optical fiber having a waveguide structure, and by inputting light having linearly polarized light along one of these fast axis / slow axis,
The light is transmitted while maintaining the polarization state. The fast axis and the slow axis are, specifically, two axes having a difference in refractive index, and a direction having a low refractive index is a fast axis,
The direction perpendicular to this and having a high refractive index is called the slow axis. PA with two stress applying parts was installed on the polarization-maintaining fiber.
There are an NDA type fiber and an elliptical jacket type fiber in which a clad portion has a double structure and an intermediate clad portion is elliptically deformed to apply stress to a core.

Here, when an optical pickup device for a near-field optical disk system using a phase-change optical disk or the like is configured as in the above-described embodiment,
Circularly polarized light is desirable as the incident polarized light to the recording pits on the recording surface of the optical disk or the equivalents. This is because it is effective to prevent the dispersion of the polarization direction with respect to the track direction and, as a result, the dispersion of the signal quality or the average deterioration. In addition, when performing land / groove recording on an optical disk having a preformatted groove (guide groove), it is more preferable to use circularly polarized light incidence because the above signal quality variation and the like are further increased when linearly polarized light is incident. It will be desired. In order to realize such circularly polarized light incidence, linearly polarized light from the first optical system is transmitted while maintaining the polarization state, and the linearly polarized light is linearly transmitted to the second optical system as a head using a 波長 wavelength plate. It is possible to convert the polarized light into circularly polarized light, convert the circularly polarized light of the return light into linearly polarized light (linearly polarized light perpendicular to the outward path), and transmit the light again to the first optical system while maintaining the polarization state. No. Therefore, it is not desirable to use a single-mode fiber or a multi-mode fiber whose polarization state is not guaranteed to be maintained as an optical fiber serving as an optical transmission means, and it is necessary to appropriately use a polarization-maintaining fiber. In consideration of this, in the embodiment of the present invention, the first optical system 11 and the head 12 as the second optical system are optically connected by the polarization maintaining fiber 13.

Next, the laser light source 31 oscillating in multiple modes used in the first optical system 11 will be described. As a light source used in a general optical disk system, a semiconductor laser (laser diode: LD) is used. However, in order to reduce the influence of reflected return light from an optical disk or an interface of an optical system, a multimode light source is used. What oscillates with is used. Specifically, for example, the driving current of the semiconductor laser is changed to a high frequency signal (for example, 200 MHz to 400 MHz).
Modulation (high frequency superimposition) in z) forcibly emits multimode laser light, or causes self-pulse oscillation in advance to cause multimode oscillation. Light emitted from a semiconductor laser in such a multimode oscillation state has a wavelength distribution (spectral distribution) as shown in FIG. 4, for example. In the example of FIG.
Taking wavelength (λ) on the horizontal axis and intensity on the vertical axis, 65
It shows a wavelength distribution (spectral distribution) in a range of about ± several nm around 7.726 nm, and has a wavelength spread of about ± several nm, although multimode oscillation can be maintained in a stable state.

A laser beam having such a wavelength distribution is
Consider the case of transmission via the polarization-maintaining fiber. FIG. 5 shows a graph in which the amount of phase shift with respect to the incident angle is calculated by calculation when the wavelength (λ) is 650 ± 10 nm as a transmittable mode in the polarization-maintaining fiber. Curve is wavelength 6
It corresponds to 50 nm. Normally, transmission is performed in the fundamental mode, that is, mode (0) in the figure. However, from FIG. 5, good transmission is achieved even when the laser light in the multimode oscillation state is transmitted by entering the polarization-maintaining fiber. It is clear that this can be achieved.

According to the above-described embodiment of the present invention, recording / reproducing becomes the first optical system 11 having the light emitting / receiving section and the second optical system having the light condensing system arranged close to the optical disk. And a polarization maintaining fiber 13
Even when using light emitted from the semiconductor laser 31 that oscillates in multiple modes,
Light can be transmitted while maintaining the polarization state between the light emitting / receiving section and the head, and signal detection can be performed efficiently.

Therefore, in the present embodiment, the head 12 serving as the recording / reproducing head does not need to include the light emitting / receiving section, so that the head 12 can be reduced in size and weight, and high-speed reading from the optical disc 1 can be performed. High-speed access (reduction in access time) is achieved. The head 12
Since the flying head method can be adopted by reducing the size of the optical disk, the focus servo provided in the conventional optical disk device becomes unnecessary. Furthermore, since the flying head method can be adopted, an optical pickup for a recording / reproducing system using near-field light can be configured.

Further, as a multimode oscillation laser light source,
An inexpensive semiconductor laser 31 combined with high-frequency superposition can be used, and low cost can be realized.

Further, since optical transmission can be performed to a plurality of optical recording / reproducing heads via a plurality of polarization preserving fibers, the configuration of a multi-head optical disk system such as a hard disk drive having a plurality of heads is also available. Can be easily realized.

In the above-described embodiment of the present invention, a head having a slider structure using a condensing system using near-field light has been exemplified. However, the present invention is not limited to this. Can be applied to the optical system. As a light condensing system using near-field light, the above-mentioned S
A SIM (Solid Immersion Mirror) or the like may be used instead of the IM. In addition, it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0038]

According to the present invention, there are provided a first optical system having a laser light source oscillating in multiple modes, a second optical system having a condensing system arranged in close proximity to the optical disk, and the first optical system. And an optical fiber disposed between the light source and the second optical system and transmitting the light emitted from the laser light source to the light condensing system, thereby reducing the size and weight of the second optical system. Thus, a flying head structure can be adopted, and recording and reproduction using evanescent waves in near-field optics can be performed.

Since the second optical system serving as the recording / reproducing head does not need to include a light receiving / emitting unit, the head can be reduced in size and weight, and high-speed reading and high-speed access (access time) to the optical disk can be achieved. Is shortened). In addition, since the flying head method can be adopted by downsizing the head, the focus servo provided in the conventional optical disk device becomes unnecessary. Furthermore, since the flying head method can be adopted, an optical pickup for a recording / reproducing system using near-field light can be configured.
Further, since there is no need to mount a laser light source on the head, there is more room for selecting a laser light source, and an inexpensive laser light source can be employed. For example, low cost can be realized by using an inexpensive semiconductor laser combined with high-frequency superposition as a multimode oscillation laser light source.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a configuration of an optical disc device according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a specific example of a head configuration of the optical disk device.

FIG. 3 is a diagram illustrating an example of a schematic configuration of an optical pickup device used in the optical disc device.

FIG. 4 is a diagram showing a wavelength distribution of a semiconductor laser oscillating in multiple modes.

FIG. 5 is a diagram illustrating a relationship between an incident angle and a phase shift amount in a transmission-possible mode in a polarization-maintaining fiber.

[Explanation of symbols]

1 optical disk, 2 support spring, 4 position detection circuit, 5 spindle motor, 6 motor drive circuit,
7a coarse drive M drive circuit, 7b fine drive drive circuit,
Reference Signs List 8 actuator control unit, 9 disk controller, 10 optical disk device, 11 first optical system, 12 head (second optical system), 13 polarization-maintaining fiber, 21 slider, 22, 23, 4
3,44 lens (SIL), 31 semiconductor laser,
34 polarizing beam splitter, 37 photodiode, 42 1/4 wavelength plate

Claims (15)

[Claims] 1. An optical disc apparatus for recording and / or reproducing information signals by irradiating an optical disc with a laser beam, comprising: a first optical system having a laser light source oscillating in multiple modes; A second optical system having a condensing system, disposed between the first optical system and the second optical system,
An optical fiber for transmitting light emitted from the laser light source to the focusing system. 2. The optical disk device according to claim 1, wherein said optical fiber is a polarization maintaining fiber. 3. The optical disk device according to claim 2, wherein the first optical system has a light receiving / emitting unit including a laser light source and a light receiving element. 4. The optical disk apparatus according to claim 2, wherein the first optical system has a polarization beam splitter for separating light emitted from the laser light source and light returned from the optical disk. 5. The optical disk device according to claim 2, wherein the laser light source of the first optical system uses a semiconductor laser driven by a high-frequency superimposed current. 6. The optical disk device according to claim 2, wherein said second optical system has a floating head structure. 7. The optical disk apparatus according to claim 2, wherein the second optical system has a light condensing system using near-field light for detecting information on the optical disk surface using an evanescent wave. . 8. The second optical system converts linearly polarized light of incident light from the polarization-maintaining fiber into circularly polarized light, and converts circularly polarized light returned from the optical disk into linearly polarized light. 3. The optical disk device according to claim 2, further comprising a wave plate. 9. A first optical system having a laser light source that oscillates in multiple modes, a second optical system having a light condensing system disposed close to the optical disk, the first optical system, and the second optical system. Between the optical system of
An optical fiber for transmitting light emitted from the laser light source to the focusing system. 10. The optical pickup device according to claim 9, wherein said optical fiber is a polarization maintaining fiber. 11. The first optical system comprises: a light receiving / emitting unit including a laser light source and a light receiving element; and a polarizing beam splitter for separating light emitted from the laser light source and light returned from an optical disk. 11. The method according to claim 10, wherein
Optical pickup device as described 12. The optical pickup device according to claim 10, wherein the laser light source of the first optical system uses a semiconductor laser driven by a high-frequency superimposed current. 13. The optical pickup device according to claim 10, wherein said second optical system has a floating head structure. 14. The optical system according to claim 1, wherein the second optical system has a light condensing system using near-field light for detecting information on the optical disk surface using an evanescent wave.
0. The optical pickup device according to 0. 15. The second optical system converts linearly polarized light of incident light from the polarization-maintaining fiber into circularly polarized light, and converts circularly polarized light of return light from the optical disk into linearly polarized light. The optical pickup device according to claim 10, further comprising a wave plate.