JP2001143282A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk device using an SIL which can rationalize a focus position despite the variation of refractive index or wavelength that is caused by the temperature change and also can decrease the noise components which are caused by the total reflected light in a reproduction mode. SOLUTION: This optical disk device consists of a 1st lens 41 which is placed near an optical disk D and has a hemispherical or super-spherical incident plane 41a and a flat emission plane 41b for the light sent from a light source, a 2nd lens 42 which has the same optical axis as the lens 41 and is placed at a position distant from the disk D compared with the lens 41 and a total reflected light detector 75 which detects the total reflected light of the light source on the plane 41b. In such a constitution, both lenses 41 and 42 can be relatively set close to each other and distant from each other according to the result of detection of the detector 75 so that the light sent from the light source forms a focus at the center of the plane 41b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an optical disk device. In this specification, the meaning of the optical disk device includes not only a device exclusively for reading an optical disk, but also a magneto-optical disk device capable of reading and writing on a magneto-optical disk by a magnetic field modulation method or an optical pulse modulation method.

[0002]

2. Description of the Related Art A magneto-optical disk is a rewritable recording medium, but in a multimedia environment that handles enormous information such as moving images and audio such as the Internet and video on demand, a further increase in capacity is desired. ing.

Recently, near-field recording using evanescent light has been spotlighted as a method for increasing the capacity of a magneto-optical disk, that is, increasing the recording density. In this method, light from a light source is transmitted to a SIL (solid immersion lens) using two hemispherical or hyperspherical lenses having a flat surface on one side and an aspherical lens.
This is achieved by focusing at a high NA on the plane of the IL. That is, of the light condensed on the plane of the SIL, light incident beyond the critical angle is totally reflected, and evanescent light with a very small spot diameter is created by this totally reflected light component. This evanescent light is SI
Since a very small spot is formed on the recording film of the magneto-optical disk located near the plane of L, a small mark can be recorded, and high-density recording becomes possible.

An optical disk apparatus for performing near-field recording using SIL is disclosed, for example, in Japanese Patent Laid-Open No. 8-212.
There is an invention described in JP-A-579. The invention described in this publication is shown in FIG. 7 of the present application. In the optical disk device 8 shown in this figure, the SIL 81 is fixed by the SIL actuator 80 disposed close to the optical disk D, and the objective lens 8 is fixed by the focus actuator 82.
3 is fixed. Then, the SIL actuator 8
The position of the focus actuator 82 and the focus actuator 82 can be adjusted, respectively.
3 between the SIL 81 and the optical disc D
The distance between the SIL 81 and the objective lens 83 is kept constant based on the change in capacitance between the SIL 81 and the objective lens 83.

[0005]

However, the SIL
If the distance between the object lens 81 and the objective lens 83 is kept constant, there is a problem that, when the refractive index or the wavelength fluctuates due to a temperature change, the focal position is shifted from a desired portion.

Further, in order to use the evanescent light by the SIL 81, it is necessary to totally reflect the light from the light source on the flat surface 81a of the SIL 81, but the totally reflected light becomes noise when the optical disk D is reproduced. There are also problems.

The present invention has been conceived under the circumstances described above. In an optical disk device using an SIL, the focus position can be optimized even if the refractive index or wavelength fluctuates due to a temperature change. Another object of the present invention is to reduce noise components caused by total reflection light during reproduction.

[0008]

DISCLOSURE OF THE INVENTION In order to solve the above problems, the present invention employs the following technical means.

That is, the optical disk device provided by the first aspect of the present invention is arranged close to the optical disk, the light incident surface of the light source is a hemispherical surface or a hyperspherical surface, and the light emitting surface is provided. A first lens having a flat surface, a second lens having the same optical axis as the first lens, and being disposed at a position farther from the optical disk than the first lens, and And a total reflection light detector for detecting total reflection of the light. The first lens and the second lens are relatively close to and separated from each other. To focus on the exit surface or on the optical disc,
The apparatus is characterized in that the first lens and the second lens are relatively close to or separated from each other based on the detection result of the total reflection light detector.

The detection result of the total reflection light detector is the first
This reflects the state of the totally reflected light on the exit surface of the lens, and thus the convergence state (defocus) of the incident light. For this reason,
By detecting the total reflected light and processing it, a focus error signal corresponding to the distance to be corrected between the first lens and the second lens can be generated. That is,
Irrespective of whether the cause of the defocus is due to tilt of the optical disc or uneven thickness of the optical disc, or to fluctuation of the refractive index or wavelength due to temperature change, the deviation of the focus position can be corrected. As described above, in the optical disk device, since the focused state can be maintained as desired, high-density recording using evanescent light can be achieved.

The first lens and the second lens may be held by the same actuator (slider), for example, the second lens may be configured to be movable in the focus direction, or the first lens and the second lens may be moved. The two lenses may be fixed to separate actuators, for example, the second lens may be configured to be movable in the focus direction.

An optical disk device provided by the second aspect of the present invention is arranged close to an optical disk, has a hemispherical surface or a hyperspherical surface on which light from a light source is incident, and has a flat exit surface. And the first lens
A second lens having the same optical axis as the lens and disposed at a position further away from the optical disc than the first lens, and a reproduction signal detector for outputting a reproduction signal by reflected light from the optical disc; An optical disc device provided on the optical path of light from the light source between the light source and the first lens, or on the optical path of the reflected light between the first lens and the reproduction signal detector. And a light shielding means for restricting incidence of total reflection light of light from the light source on the emission surface to the reproduction signal detector.

In the above configuration, since the incidence of the totally reflected light on the reproduction signal detector is restricted by the light blocking means, the total reflection light becomes noise and enters the reproduction signal detector as a noise during reproduction of the optical disk. There is no end.

The light shielding means may have any configuration as long as it can transmit only the reflected light from the optical disk, and the configuration is not particularly limited. For example, a liquid crystal that can form a non-transmissive region as necessary so as not to transmit only a light beam that will be totally reflected on the output surface of the first lens or a light beam that is totally reflected on the output surface of the light beam from the light source In addition to the shutter, a beam splitter having a non-transmission area as a reflection surface can be used.

An optical disk device provided by a third aspect of the present invention is arranged close to an optical disk, and has a hemispherical surface or a hyperspherical surface on which light from a light source is incident, and a flat exit surface. And the first lens
A second lens having the same optical axis as the lens and disposed at a position further away from the optical disc than the first lens, and a total reflection light detection for detecting total reflection of light from the light source on the emission surface A reproduction signal detector for outputting a reproduction signal by reflected light from the optical disk; and an optical path of light from the light source between the light source and the first lens, or the first lens and the reproduction signal. A light-shielding means provided on an optical path of the reflected light between the light-emitting device and a detector to limit incidence of totally reflected light of light from the light source on the emission surface to the reproduction signal detector; The first lens and the second lens can be relatively close to and separated from each other, and at the time of recording information on the optical disk, light from the light source is focused on the center of the emission surface. The first lens and the second lens are moved relatively close to or away from each other based on the detection result of the total reflection light detector. It is characterized in that it is configured to limit the incidence of the total reflection light on the detector.

In the above configuration, at the time of recording information on the optical disk, it is possible to appropriately focus on the center of the exit surface of the first lens in response to temperature change, tilt and uneven thickness of the optical disk. Therefore, high-density recording using evanescent light can be achieved. On the other hand, at the time of reproduction, the influence of the totally reflected light from the exit surface of the first lens is reduced, and a reproduced signal with less noise can be obtained.

[0017] Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the drawings.

FIGS. 1 and 2 show the configuration around the optical head 10 of the optical disk device 1 according to the present invention.
The optical head 10 includes a first
The second supported by the lens 41 and the actuator 30
It has a carriage 20 with a lens 42.

The carriage 20 is supported by a guide member 21 so as to be movable in the tracking direction (arrow X direction in FIG. 1), and is appropriately driven in the tracking direction by a linear drive mechanism 22 such as a linear voice coil motor. You.

The slider 50 is supported by the carriage 20 via a suspension member 23 made of a leaf spring. The slider 50 is a frame-shaped member having an upper surface 51 that slides on the surface (recording surface d) of the magneto-optical disk D, and has an opening 52 penetrating in the thickness direction. The first lens 41 is fitted into the opening 52. The first lens 41 is a so-called solid immersion lens (SIL), and has a form in which a sphere is cut along an equatorial plane. That is, in the first lens 41, as shown in FIG. 2, the near first surface 41a facing the second lens 42 is a hemispherical surface, and the far second surface 41b is a flat surface. I have. In SIL, the first surface 41a
When light is incident perpendicularly to the center, the light is focused on the center of the second surface 41b. Light incident on the focal point at a critical angle or more is totally reflected by the second surface 42b, and at this time, evanescent light is generated. This evanescent light is light having an extremely small spot diameter, but is easily attenuated. As will be described later, in this embodiment, the flying height of the slider 50 is set to about several tens nm because evanescent light is used when recording information on the magneto-optical disk D.

The actuator 30 is configured as a two-dimensional actuator to drive the second lens 42 in the focusing direction (the arrow Z direction in FIG. 1) and the tracking direction to perform focusing control and tracking control. The second lens 42 is basically
It is arranged on the same axis as the first lens 41 in the focusing direction. Then, the second lens 42 and the first lens 41
Is a distance such that light is perpendicularly incident on the first surface 41a of the first lens 41 to focus on the center of the second surface 41b, or on the recording surface d of the magneto-optical disk D. The distance is set so as to focus.

In FIGS. 1 and 2, reference numeral 60 indicates a magnetic head disposed on the surface of the magneto-optical disk D opposite to the slider 50. This magnetic head 60
Is required when information is recorded on the magneto-optical disk D by the magnetic field modulation method.

The recording and reproduction of information on the magneto-optical disk D by the optical disk device 1 having such an optical head 10 are performed as follows.

When recording information on the magneto-optical disk D, as shown in FIG. 3, a light beam emitted from a light source (not shown) such as a semiconductor laser and converted into parallel light by a collimator lens (not shown) is used. After passing through the half mirror 70,
The light passes through the aperture 71 and enters the second lens 42.

The half mirror 70 is a mirror that transmits light only in one direction. In this embodiment, the half mirror 70 is configured to transmit light from the light source but reflect light from the direction of the magneto-optical disk D. In addition, they are arranged so as to intersect with the traveling direction of the light from the light source.

As shown in FIG. 4, the aperture 71 has a central portion 71a which is a normal transmission region through which light can freely pass, but an outer peripheral portion (a region indicated by double hatching) 71a.
b is a selective transmission area in which a state where light is transmitted and a state where light is not transmitted can be selected. The size of the normal transmission region corresponds to the diameter of a light beam that is not totally reflected on the second surface 41b of the first lens 41. In this embodiment, when information is recorded on the magneto-optical disc D, light is transmitted through the selective transmission area, and light is not transmitted during reproduction.

As the aperture 71, for example, a liquid crystal filter is used, and by switching on and off during recording and reproduction, a state in which reflected light is selectively transmitted from the magneto-optical disk D and a state in which other light (all light) is transmitted. (Reflection) can also be selected. Also, by providing a through hole in the center of a member that does not transmit light, and by changing the position of the member during recording and reproduction,
The configuration may be such that a state in which reflected light is selectively transmitted from the magneto-optical disk D and a state in which other light (total reflection) is also transmitted can be selected.

The light incident on the second lens 42 is emitted at an angle at which the light can be perpendicularly incident on the first surface 41 a of the first lens 41, and is incident on the first lens 41. The light incident on the first lens 41 is converged and focused on the center of the second surface 41b. Then, the second surface 41b is formed at an angle smaller than the critical angle.
Is transmitted through the second surface 41b and propagates to the recording surface d of the magneto-optical disk D. On the other hand, light incident on the second surface 41b at a critical angle or more is totally reflected on the second surface 41b. At this time, evanescent light is generated on the surface of the second surface 41b. Since this light is light having a very small spot diameter as mentioned above, if this light is used, 1
High-density recording becomes possible by reducing each recording mark.

Thus, a spot is formed on the recording surface d of the magneto-optical disk D by the evanescent wave and the propagating wave. At the distance where the evanescent wave is localized, the spot formed by the propagating light is sufficiently within the depth of focus, so the size of the spot formed on the recording surface d of the magneto-optical disk D is the second surface 41b of the first lens 41. It is almost equal to the size of the spot at the upper focal position.

A light beam composed of the light totally reflected from the second surface 41b of the first lens 41 and the light reflected from the recording surface d of the magneto-optical disk D passes through the second lens 42 and the aperture 71, and then passes through the half mirror 70. It is reflected and its traveling direction is changed. Then, the luminous flux reaches the surface of the beam splitter 72 arranged in an inclined state.

Although not clearly shown in the drawing, the beam splitter 72 is provided with a circular transmission region at the center corresponding to the diameter of the light beam due to the reflected light from the magneto-optical disk D, and the remaining portion. Are reflection areas. For this reason,
The reflected light from the magneto-optical disk D is transmitted to the beam splitter 7.
2 and the totally reflected light from the second surface 41b of the first lens 41 is reflected by the surface of the beam splitter 72, and its direction is changed. The beam splitter 72 has a configuration in which, for example, the whole is formed of a normal BS film, and a reflection film is separately provided in a reflection region except for a transmission region at the center.

The total reflection light reflected by the beam splitter 72 passes through the servo unit 73. Servo unit 7
3 is a tapered first wedge portion 7 as shown in FIG.
3a, a second wedge portion 73b inclined in the opposite direction, and a lens portion 73c located therebetween. The light flux transmitted through such a servo unit 73 is
A first light beam a whose direction is changed by the eleventh wedge portion 73a, a second light beam b whose direction is changed from the first light beam a by the second wedge portion 73b, and a third light beam which is converged by the lens portion 73c. c. In addition,
As the servo unit 73, a unit having a spherical or non-inclined lens unit may be used.

Each of the light beams a, b, and c is converged by the objective lens 74, and then enters the total reflection light detector 75 in a state of being separated from each other. That is, the first light flux a
Is the second light flux b in the area A in the total reflection light detector 75.
Is incident on the area B, and the third light flux c is incident on the area C.
Each of the areas A, B, and C is provided with a plurality of split detectors (for example, two-split detectors (photoelectric conversion devices)), and each detector outputs an electrical output according to the amount of incident light. Is made. In the present embodiment, a focus error signal is generated by the Foucault method using an output from each detector according to the amount of light incident on the first area A and the second area B, and is incident on the third area C. A track error signal is generated by a push-pull method using an output from each detector according to the amount of light. Of course, the detection of the focus error and the track error may be performed by another method.

On the other hand, the reflected light from the magneto-optical disk D that has passed through the beam splitter 72 passes through the objective lens 76 and the Wollaston prism 77. In the Wollaston prism 77, the light from the objective lens 76 is split into a plurality (for example, two) of light beams and is incident on the reproduction signal detector 78 in a separated state. Is not used.

In the beam splitter 72, it is difficult to make the diameter of the transmission area equal to the diameter of the light beam of the reflected light from the magneto-optical disk D, and the reproduction signal of the totally reflected light which becomes a noise component during recording. In order to reliably block the light from entering the detector 78, the diameter of the transmission region may be smaller than the diameter of the light beam. In these cases, although the reflected light from the magneto-optical disk D is also slightly incident on the servo unit 73, the distance between the recording surface d of the magneto-optical disk D and the second surface 41 b of the first lens 41 is small. Since the distance is several tens of nm, and in the case of the magneto-optical disk D, the reflectance of light is several tens%, the focus offset generated by the reflected light from the magneto-optical disk D is slight.

Further, in order to eliminate the concern of a focus offset due to the reflected light from the magneto-optical disk D, the transmission area of the reflected light from the magneto-optical disk D in the servo unit 73 is formed as a spherical lens portion, and the remaining portion is formed. May be configured as a tapered wedge portion inclined in different directions, and may be totally reflected and incident on the wedge portion to generate a focus error signal.

By using the focus error signal obtained in this way, for example, the actuator 30 is driven in the focusing direction to optimize the distance between the first lens 41 and the second lens 42. 41
Can be focused on the center of the second plane 41b, and appropriate and high-density recording can be performed.

The driving of the second lens 42, that is, the actuator 30 in the focusing direction is performed by, for example, an electromagnetic force using a coil.

On the other hand, reproduction of information recorded on the magneto-optical disk D is performed, for example, as follows.

The light from the light source reaches the aperture 71 in the same manner as during recording. During playback, unlike during recording,
Light that will enter the second surface 41b of the first lens 41 at a critical angle or more is selectively blocked by the aperture 71, and only light incident at a critical angle or less is transmitted through the aperture 71.
Then, the light passes through the second lens 42 and is converged near the center of the second surface 41 b of the first lens 41.

At this time, if the previous operation is the recording of information on the magneto-optical disk D, the focus is on the center of the second surface 41b. This means that the second surface 41b of the first lens 41
This means that an offset occurs in the focus error signal due to the interval between the recording surface d of the magneto-optical disk D and the recording surface d. However, since the flying height of the slider 50 of this embodiment is extremely small, several tens of nm, the focus offset is small, and a reproduction spot having a sufficiently small diameter is formed on the magneto-optical disk D. can do. Further, when adjusting a focus error during reproduction, for example, a focus position where a track error signal is maximized is determined, an offset amount during reproduction is estimated, and offset injection is performed electrically during reproduction. More precisely, the focusing control of the second lens 42 can be performed at the time of reproduction.

The light applied to the magneto-optical disk D and reflected from the magneto-optical disk D reaches the beam splitter 72 in the same manner as during recording. In this beam splitter 72, only the reflected light from the magneto-optical disk D is selectively transmitted as mentioned above.
Due to this, light that would enter the second surface 41b of the first lens 41 at a critical angle or more is not sufficiently blocked, and the second surface 41b
Is totally reflected by the beam splitter 72 even if it reaches the beam splitter 72.

The light transmitted through the beam splitter 72 is transmitted through the objective lens 76 and the Wollaston prism 77. In the Wollaston prism 77, the light from the objective lens 76 is split into a plurality of (for example, two) light beams, and the split light is incident on the reproduction signal detector 78.
The reproduction signal detector 78 is configured as, for example, a four-division detector (photoelectric conversion device), and each of the light beams separated by the Wollaston prism 77 is detected in each divided region. Then, information recorded on the magneto-optical disk D is reproduced from the electrical output obtained from each divided area, and at the same time, a focus error signal is detected by, for example, the Foucault method.

Using the focus error signal obtained in this manner, the actuator 30 is driven in the focusing direction, the distance between the second lens 42 and the first lens 41 is optimized, and the first lens 41 The adjustment is performed so that the focal point is focused on the center of the two surfaces 41b.

In the above, the first lens is held by the slider and the second lens is held by the actuator. However, as shown in FIG. 6, the second lens 42 is connected to the same slider 50 as the first lens 41. And the second lens 42 is mounted on the comb-shaped electrode 5 formed on the slider 50.
It may be configured to drive in the focusing direction by using 3 or the like.

[0047]

As described above, in the optical disk device according to the present invention, the focal position can be optimized even if the refractive index or wavelength fluctuates due to a temperature change, and light density recording and reproduction on the optical disk can be achieved. can do.

In addition, during the reproduction, the total reflection light by the SIL is not only unnecessary, but may become a noise in the reproduction signal detector. However, in the above-mentioned optical disk device, the total reflection light enters the reproduction signal detector during the reproduction. Since the information is reliably shut off, appropriate information can be reproduced.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a main part of an optical disk device according to the present invention.

FIG. 2 is an enlarged sectional view taken along line II-II of FIG.

FIG. 3 is a schematic diagram illustrating an optical system of the optical disk device according to the present invention.

FIG. 4 is a plan view of the aperture shown in FIG. 3;

FIG. 5 is an overall perspective view of the servo unit shown in FIG. 3;

FIG. 6 is a cross-sectional view illustrating a state where the first lens and the second lens are mounted on the same slider.

FIG. 7 is a cross-sectional view showing the periphery of a head in a conventional optical disc device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical disk apparatus 41 1st lens 41a 1st surface 41b 2nd surface 42 2nd lens 71 Aperture (as light shielding means) 75 Total reflection light detector 78 Reproduction signal detector

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shingo Hamaguchi 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Goro Kawasaki 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture No. 1 Inside Fujitsu Limited (72) Inventor Kiyoto Matsui 4-1-1 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Kazufumi Uno 4, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Chome 1-1 F-term in Fujitsu Limited (Reference) 5D118 AA13 AA20 BA01 BB06 CC12 DB03 DC04 5D119 AA12 BA01 BB05 DA01 DA05 EB02 JA49 JA59 JB02

Claims (3)

[Claims] A first lens having a hemispherical surface or a hyperspherical surface on which light from a light source is incident and having a flat exit surface; A second lens having the same optical axis and located farther from the optical disc than the first lens; a total reflection light detector for detecting total reflection of light from the light source on the emission surface; Wherein the first lens and the second lens are relatively close to and separated from each other, and such that light from the light source is focused on the emission surface or on the optical disc. Based on the detection result in the total reflection light detector,
An optical disc device, wherein the first lens and the second lens are relatively close to or separated from each other. 2. A first lens which is arranged close to an optical disc, has a hemispherical surface or a hyperspherical surface on which light from a light source is incident, and has a flat exit surface. An optical disc having the same optical axis and a second lens disposed at a position more distant from the optical disc than the first lens, and a reproduced signal detector for outputting a reproduced signal by reflected light from the optical disc; An apparatus, provided on an optical path of light from the light source between the light source and the first lens, or on an optical path of the reflected light between the first lens and the reproduction signal detector, An optical disc device, further comprising: a light-shielding unit that restricts incidence of totally reflected light from the light source on the emission surface to the reproduction signal detector. 3. A first lens which is disposed close to an optical disc, has a hemispherical surface or a hyperspherical surface on which light from a light source is incident, and has a flat exit surface. A second lens having the same optical axis and located farther from the optical disc than the first lens; a total reflection light detector for detecting total reflection of light from the light source on the emission surface; A reproduction signal detector for outputting a reproduction signal by reflected light from the optical disk; and an optical path of light from the light source between the light source and the first lens, or the first lens and the reproduction signal detector. And a light-shielding means provided on an optical path of the reflected light between the light-emitting device and the light-emitting device, wherein the light-shielding means restricts the incidence of the totally reflected light of the light from the light source on the emission surface to the reproduction signal detector. Lens and above The second lens can be relatively close to and separated from the second lens, and when recording information on the optical disk, the total reflection light detection is performed so that light from the light source is focused on the center of the emission surface. The first lens and the second lens are relatively close to or separated from each other based on the detection result of the optical disc. When the information recorded on the optical disc is reproduced, the light-shielding means transmits the reproduced signal to the reproduction signal detector. An optical disk device characterized in that it is configured to limit the incidence of totally reflected light.