JP2002288878A - Optical recording medium, optical head, and optical recording/reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording/reproducing device using a high NA focusing lens that can carry out recording and reproducing for a long time without its optical head touching the optical recording medium. SOLUTION: This recording/reproducing device has an optical recording medium 10 having a transparent conductor 4 on a transparent cover layer 3, an optical head 12 having an optical head conductor 9 at the bottom of a lens 31, a capacitance detector 17 to detect the capacitance C between the transparent conductor 4 and the optical head conductor 9, and a position controller 18 to control the distance between the recording medium and the head 12 using the capacitance C. The optical head 102 is prevented from touching the cover layer of the optical recording medium by detecting the capacitance C between the transparent conductor 4 and the optical head conductor 9 to control the distance d between them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium and an optical head for recording and reproducing information by irradiating a light beam, and an optical recording and reproducing apparatus using the optical recording medium and the optical head. In particular, the present invention relates to an optical recording technique capable of high-density recording and reproduction using a high NA focal lens.

[0002]

2. Description of the Related Art At present, an optical recording medium for recording and reproducing information by irradiating a light beam (hereinafter referred to as "optical disk").
Has both medium variability, high-speed accessibility, large capacity, and high reliability, and has been widely put into practical use from the PC field to the AV field. It is expected that the large capacity and high speed will be promoted in the future. .

[0003] An optical disk records and reproduces information by irradiating a light beam condensed by a focusing lens onto the disk surface. The storage capacity of the optical disk is
Basically, it is defined by the light spot size of the light beam applied to the disk surface of the optical disk. This light spot size is defined by the wavelength (λ) of the light beam and the numerical aperture (NA) of the focusing lens, and the full width at half maximum of the light spot is approximately λ /
(2NA), the reproduction resolution is approximately given by λ / (4NA). Therefore, in order to increase the capacity of the optical disk, it is necessary to shorten the wavelength of the light beam and increase the NA of the focusing lens.

Conventionally, an optical disk having a recording layer on a substrate is irradiated with a light beam from the substrate side to record and reproduce information, and the focal length of a focusing lens is set longer than the thickness of the substrate. Inevitably, there is a limit to increasing the NA of the focus lens. For example, the NA of a focus lens used in a DVD (digital video disk) having a substrate having a thickness of 0.6 mm is 0.6, and even in a commercially available experimental DVD evaluator, the NA is at most 0.65. I have.

In recent years, in order to increase the capacity of an optical disk by increasing the NA of a focus lens, a recording layer and a thin transparent cover layer are sequentially deposited on a substrate, and a light beam is irradiated from the transparent cover layer side. Technology was developed. For example, Proc.P
In COS'99, pp.22-25, the thickness of the transparent cover layer is set to 0.
By setting it to 1 mm, it is possible to use a focal lens having an NA of 0.85. However, in this method, the distance (d) between the transparent cover layer and the focus lens is, for example, λ
There is a problem that the d is only about 0.13 mm with respect to a light beam of = 400 nm, and the transparent cover layer of the optical disc during operation comes into contact with the optical head, and the surface of the transparent cover layer is easily damaged.

Conventionally, for this problem, for example,
000-322768,
Applications of technologies practically used for magnetic disks, such as providing a hard protective film on the surface of a transparent cover layer and further providing a lubricating layer, have been proposed. However, when the transparent cover layer itself is made of a soft resin, it is not sufficient to avoid damage to the transparent cover layer only by providing a hard film on its surface. In Proc. PCOS2000, pp. 46-51, a capacitance detection method is disclosed as a means for actively controlling the distance between the optical head and the optical disk when a high NA SIL is used as the optical head. In this method, an electrode is provided on the SIL, and the distance between the electrode and the reflective layer of the optical disk is detected to control the distance.

[0007]

As described above, a medium-variable optical disk having a cover layer using an optical head (optical pickup) employing a high NA focus lens in order to realize a large capacity optical disk. In the conventional optical recording / reproducing apparatus for recording / reproducing the optical disk, the problem that the optical disc and the transparent cover layer are easily brought into contact with each other by shortening the distance (d) between the transparent cover layer and the focus lens, and the transparent cover layer is damaged. was there. There is a fear that damage to the transparent cover layer makes it difficult to read / write data from / on the optical disk, which in turn causes a reduction in the reliability of the optical disk.

In addition, high NA such as SIL and optical probe
In a conventional medium-fixed type optical recording apparatus using an optical head having a focal lens, a capacity detection method for controlling the distance between the optical head and the optical disk is based on the reflection layer of the optical disk and the SI.
Since a laminated film such as a dielectric layer, a recording layer, and a protective layer of the optical disk is disposed between the L electrodes, the capacitance differs depending on the film structure of the optical disk, and the distance changes for each optical disk. There was fear.

Further, in the case of the SIL recording system, 0.1 mm
It is not possible to provide a cover layer having a thickness of about
Since the distance between the IL and the optical disk is sub-μm, the system is not a medium-replaceable type.

The present invention has been made to solve such problems of the prior art, and its object is to provide a high NA.
Optical recording / reproducing apparatus capable of high-density recording / reproducing using a focal lens of this type performs highly reliable recording / reproducing operations without damaging the optical recording medium by avoiding contact between the optical recording medium and the optical head. It is an object of the present invention to provide an optical recording medium, an optical head, and an optical recording / reproducing apparatus having the optical recording medium and the optical head.

Another object of the present invention is to provide an optical recording medium, an optical head, an optical recording medium, and an optical head capable of controlling the distance between the optical recording medium and the optical head irrespective of the film structure of the optical recording medium. An object of the present invention is to provide an optical recording / reproducing apparatus having the following.

[0012]

In order to achieve the above object, a first feature of the present invention is that a substrate and information arranged on the substrate and recorded and reproduced by irradiating a light beam are recorded. An optical recording medium having at least an information recording layer, a transparent cover layer disposed on the information recording layer, and a transparent conductor disposed on the transparent cover layer.

According to a first feature of the present invention, the “optical recording medium” not only reads (reproduces) information recorded on the information recording layer but also writes new information on the information recording layer ( 1 shows a recording / reproducing optical recording medium (optical disc) capable of performing recording. The recording / reproducing type optical disc has a one-time recording type that can record only once, and a one-time recording type.
It includes a rewritable type that can erase recorded information multiple times and can perform recording / erasing many times. In the case of a recording / reproducing optical disk, for example, a reflective layer and a recording layer are formed on a substrate provided with unevenness such as a tracking guide group and address pits, and then a cover layer is formed.

The information recording layer has at least a reflective layer and a recording layer formed between the substrate and the cover layer. When the recording layer has a phase change recording layer, for example, the recording layer has a laminated structure including an upper interference layer, a phase change recording layer, and a lower interference layer. When the recording layer has a dye-based medium layer,
For example, the dye-based medium layer comprises a dye coating layer.

A second feature of the present invention is that a substrate having irregularities on which information to be reproduced by irradiating a light beam is recorded, a reflective layer disposed on the irregularities of the substrate, and a reflective layer An optical recording medium having at least a disposed transparent cover layer and a transparent conductor disposed on the transparent cover layer.

According to a second feature of the present invention, the "optical recording medium" can only read (reproduce) information recorded on irregularities formed in advance on the surface of the substrate, so-called "optical recording medium".
1 shows a read-only optical recording medium (optical disk). In a read-only optical disk, a series of information pits (irregularities) are formed on the surface of the substrate (disk surface) by a mastering process, and a thin reflective layer corresponding to the information pit arrays on the disk surface is formed. Is formed. The cover layer can be formed by a method such as spin-coating an ultraviolet curable resin or attaching a transparent sheet.

In the first and second aspects of the present invention, a light beam is applied to an information recording layer or a reflective layer via a transparent conductor and a cover layer. As a transparent conductor, IT
In addition to O and SnO ₂ , a composite film in which metal fine particles are dispersed in various transparent dielectrics, a metal film thin enough to transmit light, or the like can be used.

A third feature of the present invention resides in that a substrate, an information recording layer disposed on the substrate, on which information to be recorded / reproduced by irradiating a light beam is recorded, and an information recording layer disposed on the information recording layer. An optical recording medium having at least a transparent cover layer formed thereon and a transparent magnetic material disposed on the transparent cover layer. That is, instead of the transparent conductor in the optical recording medium having the first feature of the present invention, a magnetic material that can generate a magnetic field outside the cover layer and is substantially transparent to a light beam (this is referred to as “ A transparent magnetic material ”).

A fourth feature of the present invention is that a substrate having projections and depressions on which information to be reproduced by irradiating a light beam is recorded, a reflection layer disposed on the projections and depressions of the substrate, An optical recording medium having at least a transparent cover layer disposed thereon and a transparent magnetic material disposed on the transparent cover layer. That is, the optical recording medium according to the second aspect of the present invention is characterized in that the optical recording medium has a transparent magnetic material instead of the transparent conductor.

In the third and fourth aspects of the present invention, the light beam is applied to the information recording layer or the reflection layer via the transparent magnetic material and the cover layer. As the transparent magnetic material, besides ferrite and garnet, a composite film in which metal magnetic particles are dispersed in various transparent dielectrics, a metal magnetic film thin enough to transmit light, and the like can be used. The transparent magnetic body may be formed of a material that has been magnetized in advance in a continuous film shape. However, the generation of a large magnetic field outside the cover layer is not limited to this. That is, a material that is not magnetized may be formed into a film, patterned into an island shape or a lattice shape, and then magnetized.

In the first to fourth aspects of the present invention,
The "optical recording medium" includes not only an optical disk in a narrow sense for reproducing or recording / reproducing information using only optical means, but also reproducing / recording using reversal of magnetization direction or change of amorphous / crystal. Magneto-optical disks for reproduction are also included. That is, the “optical recording medium” in the present invention is a concept including all recording media that reproduce or record / reproduce information by irradiating a light beam condensed by a focusing lens onto a disk surface of an optical disk. . In any of the optical recording media, a cover layer is disposed on the substrate, and a transparent conductor or a transparent magnetic substance is disposed on the cover layer.

According to a fifth aspect of the present invention, there is provided a focus lens for imaging a light beam inside an optical recording medium having the first or second aspect of the present invention, and the focus lens is fixed to the focus lens. An optical head having at least an optical head conductor that performs an electrical interaction according to a distance with a transparent conductor.

For an optical recording medium in which a transparent conductor is disposed on the light incident surface of the cover layer, the optical head is provided with an optical head conductor that electrically interacts with the transparent conductor on the medium facing surface. Have. Here, "electrical interaction"
For example, this means forming a capacitance (capacitance: C) between the transparent conductor and the optical head conductor, or generating Coulomb force between the transparent conductor and the optical head conductor. As the means for arranging the optical head conductor, means such as fixing the focus lens on the casing and fixing the transparent conductor on the medium facing surface side of the casing, or forming at least the medium facing surface of the casing with a conductor can be applied. . A lead wire is preferably connected to the optical head conductor, and operations such as capacitance detection and voltage application are preferably performed through the lead wire.

According to a sixth aspect of the present invention, a focus lens for imaging a light beam inside an optical recording medium having the third or fourth aspect of the present invention, and the focus lens is fixed to the focus lens. An optical head having at least an optical head magnetic material that performs magnetic interaction according to a distance with the transparent magnetic material.

For an optical recording medium in which a transparent magnetic material is disposed on the light incident surface of the cover layer, the optical head has an optical head magnetic material that magnetically interacts with the transparent magnetic material on the medium facing surface. Have. Here, "magnetic interaction"
For example, it means to generate a magnetic repulsive force. As in the case of the optical head conductor, the arranging means of the optical head magnetic body fixes the focus lens on the casing and fixes the optical head transparent magnetic body on the medium facing surface side of the casing, or at least the medium facing surface of the casing. For example, a method of forming a magnetic material from a magnetic material can be applied.

An embodiment in which an optical recording medium having a transparent conductor and an optical head having an optical head conductor are combined,
The mode in which the optical recording medium having the transparent magnetic material is combined with the optical head having the optical head magnetic material can be further combined. For example, a conductive magnetic material may be provided on both the optical recording medium and the optical head.

A seventh aspect of the present invention is an optical recording / reproducing apparatus for performing optical recording / reproduction by irradiating an optical recording medium having the first or second aspect of the present invention with a light beam. An optical head having the fifth feature of the present invention disposed opposite to the conductor, a capacitance detection system for detecting a capacitance between the transparent conductor and the optical head conductor, and utilizing the capacitance do it,
An optical recording / reproducing apparatus having at least a position control system for controlling a distance between an optical recording medium and an optical head.

When an optical recording medium having a transparent conductor on the cover layer and an optical head having an optical head conductor on the medium facing surface are combined, the distance between the transparent conductor on the cover layer and the optical head conductor is reduced. Can be detected. The capacitance can be detected by, for example, configuring a circuit in which a capacitance and a resistor or a coil are connected in series or in parallel, applying an AC voltage, and monitoring a current or a resonance frequency. The position of the optical head is controlled by a voice coil motor or the like so that the capacitance thus detected falls within a predetermined range, thereby preventing the optical head from contacting the cover layer of the optical recording medium.

According to the seventh aspect of the present invention, since the transparent conductor is disposed on the cover layer and the optical head conductor is disposed on the opposing surface thereof, the distance between the transparent conductor and the optical head conductor is reduced. When the capacitance of the optical recording medium is detected, no matter how the layer configuration of the information recording layer of the optical recording medium is changed, the capacitance is not affected. Therefore, there is no problem that the capacitance differs depending on the film structure of the optical recording medium and the distance changes for each optical recording medium, which is a problem of the related art.

It is preferable that the optical recording / reproducing apparatus according to the seventh aspect of the present invention has means for applying a voltage having the same sign to the transparent conductor and the optical head conductor.

It is desirable that the weight of the optical head is smaller than the Coulomb repulsion acting when the distance between the optical recording medium and the optical head approaches a predetermined threshold value.

When an optical recording medium having a transparent conductor on the cover layer and an optical head having an optical head conductor on the medium facing surface are combined, the same as the transparent conductor and the optical head conductor on the cover layer. A Coulomb repulsion is formed by applying a sign voltage, and when the cover layer of the optical recording medium is too close to the optical head and the Coulomb repulsion is increased, the configuration of the optical head is made lighter than the repulsion. Thus, contact between the cover layer and the optical head can be avoided.

An eighth aspect of the present invention is an optical recording / reproducing apparatus for performing optical recording / reproduction by irradiating an optical recording medium having the third or fourth aspect of the present invention with a light beam, comprising: An optical head having the sixth feature of the present invention disposed opposite to the magnetic material, a magnetic field detection system for detecting a magnetic field intensity between the transparent magnetic material and the optical head magnetic material, and utilizing the magnetic field intensity ,
An optical recording / reproducing apparatus having at least a position control system for controlling a distance between an optical recording medium and an optical head.

When an optical recording medium having a transparent magnetic material on the cover layer and an optical head having an optical head magnetic material on the medium facing surface are combined, the distance between the transparent magnetic material on the cover layer and the optical head magnetic material is reduced. Can be detected. For the detection of the magnetic field strength, for example, a Hall element or the like can be used. The position of the optical head is controlled by a voice coil motor or the like so that the detected magnetic field intensity falls within a predetermined range, thereby preventing the optical head from coming into contact with the cover layer of the optical recording medium.

According to the eighth aspect of the present invention, since the transparent magnetic material is disposed on the cover layer and the optical head magnetic material is disposed on the opposing surface, the space between the transparent magnetic material and the optical head magnetic material is reduced. When the magnetic field strength of the optical recording medium is detected, no matter how the layer configuration of the information recording layer of the optical recording medium is changed, the magnetic field strength is not affected. Therefore, there is no concern that the magnetic field intensity varies depending on the film structure of the optical recording medium and the distance varies for each optical recording medium, which is a problem of the related art.

In the optical recording / reproducing apparatus according to the eighth aspect of the present invention, it is desirable that the transparent magnetic material and the optical head magnetic material are magnetized in advance so that repulsive magnetic force is generated.

It is desirable that the weight of the optical head is smaller than the repulsive force acting when the distance between the optical recording medium and the optical head approaches a predetermined threshold value.

In a case where an optical recording medium having a transparent magnetic material on the cover layer and an optical head having an optical head magnetic material on the medium facing surface are combined, the transparent magnetic material and the optical head magnetic material on the cover layer are previously combined. By magnetizing each other so that repulsive magnetic force is generated, when the cover layer of the optical recording medium and the optical head are too close to each other and the repulsive magnetic force is increased, the configuration of the optical head is made lighter than this repulsive magnetic force. The contact between the cover layer of the optical recording medium and the optical head can be avoided.

[0039]

Embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the width of the layers, the ratio of the thickness of each layer, and the like are different from actual ones. In addition, it goes without saying that the drawings include portions having different dimensional relationships and ratios.

(First Embodiment) In a first embodiment of the present invention, a recording / reproducing optical recording medium (optical disk) will be described. FIG. 1 is a cross-sectional view showing a film configuration of an optical disc 10 according to the first embodiment of the present invention. The optical disc 10 includes a substrate 1 having a surface on which irregularities such as grooves (pits) are formed, an information recording layer 2 disposed on the groove surface of the substrate 1, and a transparent layer disposed on the information recording layer 2. It has a cover layer 3 and a transparent conductor 4 arranged on the transparent cover layer 3.

The substrate 1 has a tracking guide groove,
A polycarbonate substrate on which predetermined irregularities such as address pits are formed is preferable (the irregularities of the substrate 1 are omitted in the drawings). In addition, as the substrate 1, a substrate having a photopolymer groove (2P groove) on a flat plate made of quartz glass or silicon (Si) or an RI on a flat plate made of glass or silicon (Si) can be used.
E (Reactive Ion Etching)
May be used in which grooves (irregularities) are formed.

The information recording layer 2 includes a reflective layer 21 disposed on the surface of the substrate 1 on which predetermined irregularities such as tracking guide grooves and address pits are formed, and a reflective layer 21.
, An upper interference layer 22, a recording layer 23 disposed on the upper interference layer 22, and a lower interference layer 24 disposed on the recording layer 23. The information recording layer 2 is a portion that can store information to be reproduced or recorded / reproduced by irradiating a light beam. Since the light beam is applied to the information recording layer 2 from the transparent cover layer 3 side, the interference layers (22, 24) are defined as the upper side 22 and the lower side 24 when viewed from the transparent cover layer 3 side. The film configuration of the information recording layer 2 shown in FIG. 1 is typical for a phase-change or magneto-optical rewritable optical disk. Here, the “rewritable optical disk” can read (reproduce) information stored in the information recording layer 2 and write (record) new information in the information recording layer 2. In addition, it is a recording / reproducing type optical disc which can erase information recorded once and can record / delete information many times.

The material of the reflection layer 21 is aluminum (A
l) Alloys, silver (Ag) alloys and the like are typical. Interference layer
The material of (22, 24) is ZnS-
SiO ₂In the case of a magneto-optical system, such as silicon nitride (Si
₃N₄) Or tantalum oxide (Ta₂O₅)
It is tabular. The material of the recording layer 23 is a phase change type material.
Magneto-optical system such as GeSbTe or AgInSbTe
In the above case, TbFeCo or the like is typical. Transparent hippo
The layer 3 is a film substantially transparent to the light beam,
It has a use to protect the information recording layer 2 from the external environment. Transparent
The material of the bright cover layer 3 is generally a phase change type or a magneto-optical type.
UV curable resin or resin
Use a fat-based sheet.

As the transparent conductor 4, ITO, SnO₂
Besides SiO₂, Si₃N₄, Al₂O₃, AlN,
TiO₂, Ta₂O₅, BN, ZrO₂Various dielectrics such as
Body or DLC (Diamond Like Carbon), organic resin
Fine conductive particles such as Au, Ag, Cu, and Al are dispersed therein
Composite film or gold (A
u), silver (Ag), copper (Cu), aluminum (A
l), tantalum (Ta), cobalt (Co), nickel
(Ni), chrome (Cr), etc.
No. When the weather resistance of the transparent conductor 4 itself is poor, the transparent conductor 4
SiO on the conductor 4 ₂Even if a thin protective film such as
good. In addition, regardless of weather resistance, thorough mechanical protection
To achieve this, a single layer of DLC or a combination of DLC and lubrication layer
A composite film may be coated.

The film thickness of the transparent conductor 4 is ITO, SnO ₂
10 nm to 1 μm, typically 50 nm
５００500 nm, more typically about 100 nm is desirable. The transparent conductor 4 is a film that is substantially transparent to a light beam. That is, when a composite film is used, although it depends on the content of the good conductor particles, when the film thickness is such that the transmittance becomes 50% or more, for example, when the content of the good conductor particles is v (vol%), (v ^{2 / 3} + (1-v) ^2/3 ) / v ^2/3 × 20
It is desirable that the film thickness is about nm or less. To form the above composite film, a co-sputtering method can be used.

(Second Embodiment) FIG. 2 is a sectional view showing a film configuration of an optical disk 19 according to a second embodiment of the present invention. An optical disc 19 according to the second embodiment of the present invention includes a substrate 1 having a surface on which irregularities such as grooves (pits) are formed, an information recording layer 2 disposed on the groove surface of the substrate 1, It has a transparent cover layer 3 disposed on the information recording layer 2 and a transparent magnetic body 5 disposed on the transparent cover layer 3. The difference is that a transparent magnetic body 5 is arranged in place of the transparent conductor 4 as compared with the optical disc 10 shown in FIG. 1, and the other configuration is the same.

As the transparent magnetic material 5, besides ferrite and garnet, SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ , Al
N, TiO ₂ , Ta ₂ O ₅ , BN, ZrO _2, etc. in various dielectrics or DLC, organic resin, CoCr, Co
A composite film in which a hard magnetic material typified by PtTaCr, TbFeCo or the like is dispersed, or a metal magnetic material such as CoCr, CoPtTaCr, or TbFeCo having a thickness of about 20 nm or less can be used. When the weather resistance of the transparent magnetic body 5 itself is poor, a thin protective film such as SiO ₂ may be coated on the transparent magnetic body 5.

The transparent magnetic body 5 applies a line of magnetic force perpendicular or parallel to the light incident surface of the optical disc 19 to the optical disc 19.
This is a film that can be uniformly generated in a plane.
Therefore, the shape of the transparent magnetic body 5 may be a continuous film shape, but may be an island shape, a lattice shape, a line and space shape, or the like.
It may be processed (patterned) into an appropriate shape. However, when the shape of the transparent magnetic body 5 is a continuous film, it is desirable that the directions of the magnetic poles of the transparent magnetic body 5 be uniformly distributed in the vertical direction with respect to the surface of the optical disk 19. That is, it is desirable that the direction of the magnetic pole is processed (patterned) into an appropriate shape. If the direction of the magnetic pole is only one of the upper and lower directions, a strong magnetic field is generated near the inner and outer peripheral ends of the optical disk 19, but almost no magnetic field is generated at the center of the optical disk 19. .

On the other hand, when processing into an appropriate shape, for example, by mask-sputtering a garnet-based perpendicular magnetization film, the transparent magnetic body 5 having the shape shown in FIG. 2 can be easily obtained. FIG. 2 shows a case where the transparent magnetic body 5 is processed (patterned) into an appropriate shape, and magnetic lines of force perpendicular to the light incident surface are uniformly generated in the surface of the optical disk 19. The pattern size of the transparent magnetic body 5 may be smaller than that of the focus lens or its casing, and may be several hundred μm to several mm, so that patterning can be easily performed by mask sputtering. Of course, a pattern may be formed by forming a continuous film, masking it, and subjecting it to ion milling, wet etching, or dry etching. After patterning, the magnetic field of the transparent magnetic material 5 is applied by applying a magnetic field equal to or higher than the coercive force of the transparent magnetic material 5 to make the magnetization directions of the transparent magnetic material 5 uniform. In the example of FIG. 2, magnetization is performed in the upward direction, but by magnetizing after patterning in this manner, magnetic lines of force (dashed lines in FIG. 2) can be periodically formed outside the cover layer. The transparent magnetic body 5 may be magnetized downward, and the magnetization of the transparent magnetic body 5 may be perpendicular or in-plane to the cover layer.

(Third Embodiment) In a third embodiment, an example of the optical head of the present invention will be described. FIG.
(A) is an optical head 1 according to a third embodiment of the present invention.
FIG. 2 is a cross-sectional view showing the configuration of FIG. As shown in FIG. 3A, the optical head 12 condenses a light beam using a first focus lens 6 and a second focus lens 7, and
0, 19). The arrow in FIG. 3A indicates the optical path of the light beam. In FIG. 3A, both the first focus lens 6 and the second focus lens 7 are convex lenses on one surface and are flat lenses on the other surface. The light beam emitted from the light source first enters the convex surface of the first focusing lens 6 and is converged. The light beam emitted from the flat surface of the first focus lens 6 enters the convex surface of the second focus lens 7 and is further converged, and the flat surface (lens bottom surface) 21 of the second focus lens 7 facing the optical disk 10. Is released. The light beams converged by the first and second focus lenses (6, 7) form an image at a focus position (FP). The information recording layer 2 of the optical disc (10, 19) is arranged at the position of the FP. The first and second focus lenses (6, 7) are made of glass or transparent resin.

Here, the distance from the lens bottom surface (the surface facing the medium) 21 of the second focus lens 7 to the image forming point of the light beam, that is, the information recording layer 2 forms a working distance (WD). Optical disk (10, 19)
Is defined as the distance to the surface (light incident surface) 20 of the cover layer 3. When the distance d becomes zero, it means that the optical head 12 and the optical disk (10, 19) are in contact with each other. By combining the two lenses of the first and second focal lenses (6, 7), the numerical aperture (NA) of the lenses can be increased to about 0.75 to 0.9. N
When A is 0.85 and a light beam having a wavelength of 400 nm is used, the working distance (WD) is 0.13 m
m.

The first and second focus lenses (6, 7) are held in a predetermined casing 8, and the optical system between the first and second focus lenses (6, 7) is fixed by the casing. A flat optical head conductor (hereinafter abbreviated as “conductor”) 9 is arranged on the outer periphery of the second focus lens 7 in parallel with the lens bottom surface 21 and on the same plane as the lens bottom surface 21. The conductor 9 is also a first and second focus lens (6,
It is fixed by the casing 8 as in 7). The material of the casing 8 is not particularly limited. In order to reduce the weight, it is desirable to use a resin. The shapes of the casing 8 and the conductor 9 are not particularly limited as long as they do not protrude from the medium facing surface (lens bottom surface) 21 of the second focus lens 7. It is preferable that the conductor 9 disposed on the medium facing surface of the casing 8 be connected to a capacitance detecting means or a voltage applying means by a lead wire. The capacitance detecting means or the voltage applying means will be described later.

FIG. 3B is a plan view showing the configuration of the optical head 12 shown in FIG. 3A as viewed from the medium facing surface (bottom of lens) 31 side. As shown in FIG. 3 (b), the conductor 9 has a ring-shaped planar shape, and its inner and outer circumferences are
It is arranged concentrically with respect to the second focus lens 7 arranged at the center of the optical head 12. Surface area S of conductor 9
Is the capacitance C, which will be described later with reference to FIG.
Has a proportional relationship with Therefore, in order to improve the detection sensitivity of the capacitance C, it is desirable that the area S is large. That is, it is desirable to make the inner diameter of the conductor 9 closer to the outer diameter of the second focus lens 7 and increase the outer diameter of the conductor 9.

Although the case where the conductor 9 is used is shown here, an optical head magnetic body (hereinafter, referred to as a conductor) is used instead of the conductor.
9 may be used. The conductor 9 and the magnetic body 9 can be made of the same material as the transparent conductor 4 and the transparent magnetic body 5 described in the first and second embodiments, respectively. Although an example in which two focus lenses are combined is shown here, three or more focus lenses or one focus lens may be used. Furthermore, the shape of each focus lens is not limited to the case where one is a convex lens and the other is a planar lens, and both may be convex lenses.
A high NA lens such as SIL may be used.

(Fourth Embodiment) In a fourth embodiment, the optical disk 10 having the transparent conductor 4 described in the first embodiment and the conductor 9 described in the third embodiment are used.
An optical recording / reproducing apparatus in which an optical head 12 having a combination is described. In the fourth embodiment, an apparatus configuration for realizing a position control method by detecting a capacitance C between the transparent conductor 4 of the optical disk 10 and the conductor 9 of the optical head 12 will be described. I do.

FIG. 4 is a block diagram showing a schematic configuration of an optical recording / reproducing apparatus according to a fourth embodiment of the present invention. A medium facing surface 31 with an optical head of 12 is disposed at a predetermined distance d on the light incident surface 20 side of the optical disk 10 on which the transparent conductor 4 is disposed on the transparent cover layer 3. Optical head 1
Above the light source 2, a light source 13 that generates a light beam via a beam splitter 14 is disposed. In a direction different from that of the light source 13 with respect to the beam splitter 14, a photodetector 15 that detects light reflected from the optical disc 10 is arranged. The beam splitter 14 is for guiding the reflected light from the optical disc 10 to the photodetector 15. The light detector 15 is connected to the data processing system 16. A voice coil motor (V
In order to move the optical head 12 in the CM 11, for example, a magnet or the like (not shown) is attached. Optical head 1
The second conductor 9 is connected to a capacitance detection system 17 for detecting the capacitance C between the second conductor 9 and the transparent conductor 4 of the optical disk 10, and the capacitance detection system 17 is connected to a position control system 18. Further, a spindle motor 32 for rotating the optical disk 10 at high speed is disposed at a central portion thereof.

As the light source 13, a semiconductor laser is generally used. For example, InGaN having a wavelength of 405 nm is used.
A system LD (Laser Diode) is used. The light beam (thin arrow in the figure) emitted from the light source 13 is incident on the optical head 12 via the beam splitter 14,
Is focused on the information recording layer 2 of the optical disc 10 to form an image. Then, the light beam is reflected by the information recording layer 2. The reflected light beam (reflected light) includes a signal (reproduction light) having information stored in the information recording layer 2. The reflected light again passes through the optical head 12 and is split from the incident light by the beam splitter 14. The divided reflected light enters the photodetector 15 and is converted into an electric signal. The electric signal (thick arrow in the figure) is input to the data processing system 16. The data processing system 16 transmits a predetermined control signal to the light source 13, the voice coil motor 11, or the spindle motor 32 based on the input electric signal. For example, when the data processing system 16 detects a focusing error from the reproduced signal of the photodetector 15, the data processing system 16 transmits a signal for correcting the focusing error to the voice coil motor 11. Then, based on this signal, the voice coil motor 11 moves the optical head 12 to adjust the distance d between the optical head 12 and the optical disk 10. Data processing system 16
The detailed configuration will be described later.

The capacitance detecting system 17 is composed of, for example, a circuit in which a resistor, an AC power supply, and a current monitor are connected in series, and the conductor 9 of the optical head 12 and the transparent conductor of the optical disk 10 are determined based on the resistance value, the current value, and the voltage value. The capacitance C with the body 4 is monitored, and the current value or the voltage value is set in the position control system 1.
8 is output. The position control system 18 receives the signal of the current value or the voltage value of the capacitance detection system 17, and when the capacitance C is out of the predetermined capacitance range, particularly, when the optical head 10 and the optical disk 10 are too close to each other, the capacitance When the increase of C becomes excessive, the optical coil 1
A signal for separating the optical head 12 from 0 is transmitted. The voice coil motor 11 moves the optical head 12 based on this signal, and
Increase the distance d between them.

FIG. 5 is a block diagram showing a detailed configuration of the data processing system 16. The preamplifier 161 and the variable gain amplifier 162 amplify the electric signal output from the photodetector 15. The A / D converter 163 converts the amplified electric signal into a digital signal sequence. Linear equivalent circuit 164
Is a kind of digital filter. The data detection circuit 165 is, for example, a signal processing circuit for detecting data from a reproduced signal waveform equalized by a partial response (PR) by using a maximum likelihood (ML), and more specifically, a Viterbi decoder. The decoder 166,
It has a function of restoring the code bit string detected by the data detection circuit 165 to the original recording data. The drive controller 167 is a main control system of the optical recording / reproducing apparatus, and is connected to, for example, a personal computer or an AV device via the interface 169, and controls transfer of recording / reproducing data.

Although not shown, the optical recording / reproducing apparatus performs an error correction process on the data demodulated by the moving picture compression circuit, the moving picture decompression circuit, and the data detection circuit 165 when recording and reproducing video information. An error detection and correction circuit is also included. When the optical disk 10 is of a recordable and erasable type such as a phase change type and a magneto-optical type, the erasing light for erasing the recorded data is formed, for example, by a modulation circuit
It is performed at 70. For example, when a phase-change rewritable optical disk is used, the modulation circuit 170 generates, as a signal for erasing data, erasing light having an erasing power level lower than the recording power level in a DC or pulse form. . Erasing light is emitted by the laser driver 171 according to the generated signal.

FIGS. 6A and 6B show two parts of the capacitance detection system 17 which is a characteristic part of the optical recording / reproducing apparatus according to the present invention.
FIG. 3 is a circuit diagram illustrating various embodiments. First, FIG.
Shows the configuration of the capacitance detection system 17 when detecting the capacitance using the RC circuit. In FIG. 6A,
The capacitance C is a capacitance formed between the transparent conductor 4 of the optical disk 10 and the conductor 9 of the optical head 12.
One electrode of the capacitance, that is, the transparent conductor 4 of the optical disk 10 is connected to the ground potential. One terminal of an AC power supply E is connected to the other electrode of the capacitance, that is, the conductor 9 of the optical head 12. The other terminal of the AC power supply E is connected to the position control system 18 and at the same time to the ground potential via the resistor R. The voltage drop across the resistor R depends on the capacitance. By outputting the voltage values at both ends of the resistor R to the position control system 18, the capacitance of the capacitance C can be detected and output.

The voltage at both ends of the resistor R is monitored, and when this value exceeds a predetermined value, the position control system 18 sends a signal from the optical head 12 to the optical head 12.
Is output in a direction away from the optical disk 10 to drive the voice coil motor 11. Assuming that the distance from the lens bottom surface 21 shown in FIG. 3 to the light incident surface 20 of the optical disk 10 is d, and the surface area of the conductor 9 at the lower end of the optical head 12 is S, the capacitance C is C = ε ₀ × S / D (1) Here, ε ₀ is the dielectric constant of air (8.85
4 × 10 ⁻¹² F). Even when a protective film or the like is provided between the transparent conductor 4 on the surface of the cover layer 3 and the conductor 9 at the lower end of the optical head 12, the capacitance C is (1) because the main part of the distance d is air. It may be approximated by an equation. The capacitance C can also be controlled by changing the distance d by recessing the position of the conductor 9 of the optical head 12 from the medium facing surface 31. However, here, the distance d is the distance between the medium facing surface (closest surface) 31 of the optical head 12 and the cover layer 3 of the optical disk 12. For example, in FIG. 3A, the outer diameter of the first focus lens 6 is 6 mm, the outer diameter of the second focus lens 7 is 2 mm, the shape of the casing 8 is devised, the outer diameter of the conductor 9 is 10 mm, and the inner diameter is 10 mm. Is the outer diameter (= 2 mm) of the second focal lens 7, the surface area S is 75.4.
a mm ^2.

FIG. 7A is a graph showing the relationship between the distance d and the capacitance C in the equation (1). For example, wavelength 4
In the just focusing operation of 00 nm and NA: 0.85, the distance d is 0.13 mm, so that the capacitance C is about 5 pF. When a focusing error occurs and the optical head 12 approaches the optical disc 10, the distance d
, And the capacitance C increases.

In the circuit configuration of FIG. 6A, the position control system 1
8, the voltage at both ends of the resistor R is given by V = E / (1+ (1 / ωCR ² )) ^1/2 (2) where the frequency of the AC power supply E is ω. Can be For example, when an AC power supply E having a frequency of 1 MHz and a voltage of 1 V is used and the resistance value of the resistor R is 24 kΩ, the voltage V changes as shown in the graph of FIG. The graph shown in FIG. 7B is obtained by substituting (1) for the capacitance C in the equation (2). FIG.
Using the response of the voltage V to the distance d as shown in (b), for example, when the voltage V exceeds 0.7 V, if the position control system 18 outputs a signal in a direction to move the optical head 12 away from the optical disc 10 Thus, contact between the optical head 12 and the cover layer 3 of the optical disk 10 can be prevented. Note that the voltage V
May be used as it is or may be amplified and used.

FIG. 6B shows the configuration of the capacitance detection system 17 for detecting the capacitance using the RLC circuit. In FIG. 6B, the capacitance C is as shown in FIG.
This is the capacitance formed between the transparent conductor 4 of the optical disk 10 and the conductor 9 of the optical head 12 as in (a).
The transparent conductor 4 of the optical disk 10 is connected to the ground potential,
The conductor 9 of the optical head 12 is connected to one terminal of an AC power supply E. The other terminal of the AC power supply E is connected to one end of the resistor R. The other end of the resistor R is connected to the position control system 18 and at the same time to the ground potential via the inductance L. The voltage drop across the inductance L depends on the capacitance C. By outputting the voltage value at both ends of the inductance L to the position control system 18, the capacitance of the capacitance C can be detected and output.

In the configuration shown in FIG. 6B, the detection sensitivity increases when the vicinity of the resonance frequency is used as the threshold value of the control signal. The input signal to the position control system 18 is the voltage V across the inductance L. In this case, the voltage V is given by: V = ωLE / (R ² + (ωL− (1 / ωC) ² )) ^1/2 (3) FIG. 6B shows a mode in which the frequency of the power source E is 1 MHz, the inductance L is 3.8 mH, the resistance value of the resistor R is 100Ω, and the capacitance C having the capacitance characteristic shown in FIG. The RLC circuit resonates when the distance d is d = 0.1 mm, and the output voltage V at this time becomes about 240 times the voltage of the AC power supply E. Therefore, for example, when the distance d between the optical head 12 and the optical disk 10 approaches 0.1 mm to 0.05 mm due to, for example, a focusing error, the output of the voltage V is changed to the AC power supply E.
Is reduced from 240 times to about 2 times, and the capacitance C, that is, the distance d can be detected with extremely high sensitivity.

In the circuit configurations shown in FIGS. 6A and 6B, the reason why one electrode 4 of the capacitance C is connected to the ground potential is that the potential of the optical disc 10 is generally equal to the ground potential. Corresponding to that in. Therefore, even if the optical disk 10 has a resistance component with respect to the ground potential, the effect of the present invention is not affected.

Next, an experimental example performed by the inventor of the present invention will be described. The inventor described an optical recording / reproducing apparatus according to a fourth embodiment of the present invention (Example of the present invention) shown in FIGS. 4, 5 and 6 and a conventional optical recording / reproducing apparatus (Comparative Example) as follows. It operated by the procedure of. In the operation of the embodiment of the present invention, the capacitance detection system 17 and the position control system 18 shown in FIG. 4 were operated, and in the operation of the comparative example, the capacitance detection system 17 and the position control system 18 were not operated. First, the operation procedure of the embodiment of the present invention will be described.

(A) First, the optical disk 10 having the film configuration shown in FIG. 1 is set on the spindle motor 32, and the spindle motor 32 is driven to rotate together with the optical disk 10 by the output from the drive control circuit 168. At this time, the capacitance detection system 17 and the position control system 18 are always operated, and when the capacitance C exceeds a predetermined value, that is, when the optical head 12 and the optical disk 10 approach abnormally, the optical head 12 is moved. A signal is output from the position control system 18 to the voice coil motor 11 in a direction away from the optical disk 10.

(B) Next, the light source 13 is connected to the laser driver 1.
Driving at the output of 71, for example, a light beam of a reproduction level or a recording / erasing level is first irradiated onto the disk surface. That is, a light beam for reading information stored in the optical disk 10 is irradiated. Then, the reflected light from the optical disk 10 is passed through the beam splitter 14 to the photodetector 1.
Lead to 5.

(C) Next, a focusing control signal is output from the drive controller 167 of the data processing system 16 and the voice coil motor 11 is driven via the drive control circuit 168 to place the optical disk on the light beam imaging point. 10
Focusing is performed so that the information recording layer 2 is disposed. When a focusing error occurs due to a disturbance, the voice coil motor 11 is driven by using the capacitance detection system 17 and the position control system 18, the optical head 12 is separated from the optical disk 10, and the focusing control is performed again with a certain distance. The operation procedures (a) to (c) are similarly performed during the recording / reproduction operation described below.

(D) Next, in the data recording procedure of the optical recording / reproducing apparatus, first, the drive controller 167 takes in the data signal input through the interface 169. Then, the signal is modulated into a predetermined signal pulse train through the modulation circuit 170. Then, the laser driver 171 is driven by the modulated signal, and the recording pulse light is emitted from the light source 13. When the phase-change type optical disk 10 is used, an amorphous recording mark is formed in a portion irradiated with the recording level light beam. The recording mark train is formed on a predetermined recording track according to the information signal train by the rotation operation of the optical disc 10 and the irradiation of the recording pulse light.

(E) Finally, in the data reproducing procedure of the optical recording / reproducing apparatus, first, a light beam at a reproducing level is emitted from the light source 13 and the converged light beam is irradiated on the optical disk 10. Then, the reflected light from the optical disk 10 is made incident on the photodetector 15. When a phase-change type optical disk is used, the reflected light (reproducing light) is signal-modulated by a reflectance difference or a phase difference between an amorphous mark portion and a crystal space portion. The reproduction light incident on the photodetector 15 is converted into an electric signal, amplified through a preamplifier 161 and a variable gain amplifier 162, and then converted into a digital signal series by an A / D converter 163. Then, a filter is applied by a linear equivalent circuit 164, and a Viterbi decoder (data detection circuit) 165 detects a sign bit sequence of a reproduced signal waveform. Finally, the code bit string is restored to the original recording data by the decoder 166.

In the above operation procedure, a recording / reproducing operation was similarly performed without operating only the capacitance detection system 17 and the position control system 18, and a comparative example was implemented. As a result, in the optical recording / reproducing apparatus according to the embodiment of the present invention, the cover layer 3 of the optical disk 10 is not damaged at all, that is, the cover layer 3 of the optical disk 10 is not in contact with the optical head 12 for a long time. The recording / reproducing operation could be performed stably over the whole period. However, in the optical recording / reproducing apparatus of the comparative example, contact between the cover layer 3 and the optical head 12 occurs accidentally, and the cover layer 3 is damaged. When the damage is severe, the vicinity of the damaged portion is no longer recorded and reproduced again. The operation can no longer be performed.

As described above, according to the optical recording / reproducing apparatus according to the fourth embodiment of the present invention, the capacity detecting system 17
Is the surface on the optical head 12 side of the optical disk 10 (light incident surface)
20 and a second conductor of the optical head 12.
During the recording / reproducing operation, the capacitance C between the optical head 12 and the optical disk 10 is monitored by the position control system 18 based on the value of the capacitance C. By controlling the position of the optical head 12 so as to avoid contact with the optical head 12, the recording / reproducing operation can be stably performed for a long time.

Therefore, the light beam converged by the high NA focusing lens (6, 7) is converted to a light beam of several tens μm to several hundred μm.
Even in a close high-density recording system in which the working distance is only about 100 μm and the information recording layer 2 is accessed via the transparent cover layer 3 having a thickness of It is possible to provide an optical disk, an optical head, and an optical recording / reproducing apparatus including the optical disk and the optical head that can perform a stable recording / reproducing operation for a long period without damaging the layer 3.

(Fifth Embodiment) In the fourth embodiment, an optical recording / reproducing apparatus in which an optical disk 10 having a transparent conductor 4 and an optical head 12 having a conductor 9 are combined is used. The method of controlling the position of the optical head 12 by monitoring the capacitance C between the optical head 12 and the optical head 12 has been described. However, in the present invention, the position control between the optical disk 10 and the optical head 12 is not limited to the method based on capacitance detection.

In the fifth embodiment, in an optical recording / reproducing apparatus in which an optical disk 19 having a transparent magnetic body 5 and an optical head 12 having a magnetic body 9 are combined, the transparent magnetic body 5 and the magnetic body 9 are repelled from each other. An embodiment will be described in which the magnets are magnetized so as to generate a force, and the position of both is controlled by the repulsive magnetic force acting between the optical disk 19 and the optical head 12.

The optical disk according to the fifth embodiment is
This is the optical disc 19 described with reference to FIG. 2 in the second embodiment. On the other hand, the optical head according to the fifth embodiment is the optical head 12 described with reference to FIG. 3 in the third embodiment.
Is used.

The transparent magnetic material 5 formed on the cover layer 3 of the optical disk 19 is initially magnetized after the mask is formed so that the magnetic field lines are generated upward as shown in FIG. On the other hand, the magnetic body 9 of the optical head 12 is magnetized downward in FIG. 3 so that the magnetic field lines are generated toward the light incident surface 20. When the lens bottom surface 31 of the optical disk 19 and the light incident surface 20 of the optical head 12 are close to each other with a distance d as shown in FIG. 3, magnetic poles of the same polarity face each other, and Magnetic force works. The strength of the repulsive magnetic force is proportional to the square of the distance d.

The weight of the movable portion of the optical head 12 is set to be smaller than the repulsive magnetic force acting when the distance d between the cover layer 3 and the optical head 12 is closer than a predetermined threshold. When the distance d between the cover layer 3 and the optical head 12 is greater than or equal to a predetermined threshold value, the repulsive magnetic force is set to be equal to or smaller than the weight of the optical head 12 and not to hinder normal focusing control. I do. By setting the magnetization amounts of the transparent magnetic body 5 and the magnetic body 9 and the weight of the optical head to the above-described conditions, when a focusing error occurs due to disturbance and the optical head 12 abnormally approaches the cover layer 3 of the optical disk 19, Since the optical head 12 is pushed back in a direction away from the optical disk 19 by the strong repulsive magnetic force, a contact accident between the optical head 12 and the cover layer 3 of the optical disk 19 can be prevented.

The operation procedure of the recording / reproducing operation of the optical recording / reproducing apparatus according to the fifth embodiment is basically the same as the procedure shown in the fourth embodiment. However, here, a configuration corresponding to the capacitance detection system 17 and a configuration corresponding to the position control system 18 are not required. Further, as in the fourth embodiment, the inventor conducted an operation experiment of the optical recording / reproducing apparatus according to the fifth embodiment, and was able to obtain similar good results.

(Sixth Embodiment) In the fourth embodiment, the capacitance detection system 17 and the position control system 18 are used to connect the transparent conductor 4 of the optical disk 10 and the conductor 9 of the optical head 12 with each other. The embodiment has been described in which the capacitance C of the optical head 12 is monitored and the position of the optical head 12 is controlled to avoid contact between the two. However, in the present invention, the position control between the optical disk 10 and the optical head 12 is not limited to the method based on capacitance detection.

In the sixth embodiment, in an optical recording / reproducing apparatus in which an optical disk 10 having a transparent conductor 4 and an optical head 12 having a conductor 9 are combined, the same reference numerals are used for the transparent conductor 4 and the conductor 9. An embodiment will be described in which the position of the optical disk 10 and the optical head 12 is controlled by the Coulomb repulsive force acting between the optical disk 10 and the optical head 12 using the means for applying the voltage.

The optical disc in the sixth embodiment is
This is the optical disc 10 described in the first embodiment with reference to FIG. On the other hand, the optical head according to the sixth embodiment is the optical head 12 having the conductor 9 described with reference to FIG. 3 in the third embodiment.

Means for applying the same voltage to transparent conductor 4 and conductor 9 (hereinafter abbreviated as "voltage applying means")
Comprises a first means for applying a positive or negative voltage to the transparent conductor 4 and a second means for applying a positive or negative voltage to the conductor 9. The first means is connected to the conductor 9 in the same manner as the capacitance detection system 17 shown in FIG. On the other hand, the second main stage is provided with a device such as arranging a rubbing contact on the spindle motor 32 so that the optical disk 10 which is driven to rotate is rotated.
Are connected to the transparent conductor.

In such an apparatus configuration, the cover layer 3
A voltage of the same polarity is applied to the upper transparent conductor 4 and the conductor 9 of the optical head 10. The magnitude of the voltage is set so large that a Coulomb repulsion force stronger than the weight of the optical head 12 occurs when the distance d between the optical head 12 and the optical disk 10 approaches a predetermined threshold value. At the same time, when the distance d between the optical head 12 and the optical disk 10 is greater than or equal to a predetermined threshold value, a Coulomb repulsion force equal to or smaller than the weight of the movable portion of the optical head 12 does not occur and does not hinder the focusing control. It is set small. Voltage applied to transparent conductor 4 and conductor 9 and optical head 12
By setting the weight of the optical disk 10 to the above-mentioned condition, the optical head 12 moves the optical disk 10 due to a focusing error due to disturbance.
Optical head 1 due to Coulomb repulsion when approaching abnormally
2 can be moved away from the optical disc 10.

Note that the voltage applying means may consist of only the first means. That is, it is not necessary to positively apply a voltage to the transparent conductor 4 on the cover layer using the second main stage. In this case, the transparent conductor 4 is in a state of being at a floating potential or being at a potential from an installation potential via a resistance component.

Further, the position control method based on capacitance detection and the position control method based on Coulomb repulsion described in the fourth embodiment may be combined. That is, the above-described voltage applying means may be added to the optical recording / reproducing apparatus having the capacitance detection system 17 and the position control system 18 shown in FIG.

(Seventh Embodiment) In the first to sixth embodiments, information is transmitted through the transparent cover layer 3 having a thickness of about 0.1 mm using a focal lens having an NA of about 0.85. The mode in which the recording layer 2 is irradiated with the light beam has been described. However, the present invention is also useful in a fixed optical recording / reproducing apparatus that irradiates an optical disk with a light beam through an SIL or a minute optical aperture having an effective NA of more than 1. In this case, a thin protective film of about several tens nm is disposed on the information recording layer 2 of the optical disc 10 instead of the transparent cover layer 3. The protective film also serves as the transparent conductor 4 or the transparent magnetic material 5, or the transparent conductor or the transparent magnetic material is disposed on the protective film. Other configurations are the same as those of the optical disc shown in the first and second embodiments.

The capacitance C between the transparent conductor 4 disposed on the outermost layer of the medium and the capacitance C between the transparent conductor 4 disposed on the outermost layer of the medium is detected without detecting the capacitance C between the transparent layer 4 and the reflection layer 21 disposed on the deep part of the medium. Since the position control is performed, it is possible to solve the problem of the related art that the optimum distance between the optical head and the optical disk changes for each layer configuration of the optical disk.

(Other Embodiments) As described above, the present invention has been described with reference to the first to seventh embodiments. However, the description and drawings constituting a part of this disclosure limit the present invention. Should not be understood. From this disclosure, various alternative embodiments, examples, and operation techniques will be apparent to those skilled in the art.

In the first embodiment of the present invention, a recording / reproducing optical disk has been described, but the present invention is not limited to this. The present invention can also be applied to a read-only optical disk. At this time, as shown in FIG. 8, the information recording layer shown in FIG. 1 or FIG. 2 has a surface (disk surface) of a substrate having an information pit row (irregularities) formed by a mastering process and a disk surface of this disk surface. It corresponds to a single-layer structure composed of a thin reflective layer 21 formed corresponding to the information pit row. Further, the recording / reproducing type optical disk may be a one-time recording type in which information can be recorded only once, or information recorded once can be erased, and recording / erasing can be performed many times. It may be a rewritable type. In the case of the one-time recording type, it has a dye-based or phase-change type information recording layer, and in the case of the rewritable type,
It has a phase-change or magneto-optical information recording layer.

Further, in the fourth embodiment of the present invention, the position control system 18 outputs a position control signal to the existing voice coil motor 11 for performing optical alignment of the optical head 12. I explained about the case.
That is, the method of moving the optical head 12 in a direction away from the optical disk 10 in order to avoid an accidental contact accident due to an abnormal approach between the optical head 12 and the optical disk 10 has been described. However, the present invention is not limited to this.
The optical disk 10 may be moved instead of the optical head 12 by rotating the spindle motor 32 and the optical disk 10 that are rotating.

Further, in the fifth embodiment, a method of arranging a magnetic material which has been magnetized in advance on both the optical disk 19 and the optical head 12 and performing position control using a repulsive magnetic force generated between them. However, the present invention is not limited to this. As in the fourth embodiment, as the capacitance of the conductors (4, 9) disposed on both the optical disk 19 and the optical head 12 is detected, the change in the magnetic field intensity between the optical disk 19 and the optical head 12 is determined. The distance d between the two may be detected. For example, the optical disk 19
A means for measuring the magnetic field strength such as a Hall element instead of disposing the transparent magnetic material 5 magnetized in advance as shown in FIG. 2 and disposing the magnetic material 9 on the optical head 12 (magnetic field sensor)
May be arranged. At this time, the optical recording / reproducing apparatus shown in FIG. 4 has a magnetic field detection system instead of the capacity detection system 17,
When the magnetic field sensor detects a magnetic field intensity equal to or higher than a predetermined threshold, the magnetic field detection system
A position control signal for avoiding contact with the position control system 1
8 may be output.

That is, the optical recording / reproducing apparatus according to the present invention is characterized by performing position control between an optical disk and an optical head using an electromagnetic interaction generated between the optical disk and the optical head. The following two types can be considered as specific control means.

(1) Repulsive magnetic force or Coulomb repulsive force generated between the optical disk and the optical head.

(2) Combination of means for detecting an electric field or a magnetic field between the optical disk and the optical head, and means for externally controlling the position of the optical head or the optical disk based on the detection results.

In the case of (2), since the conductor or magnetic material of the optical disk is disposed on the outermost layer on the light incident surface side, position control independent of the film structure of the optical disk can be performed.

Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Accordingly, the present invention is limited only by the matters specifying the invention according to the claims that are reasonable from this disclosure.

[0101]

According to the present invention, in an optical recording / reproducing apparatus capable of high-density recording / reproducing using a high NA focal lens, damage to the optical recording medium is avoided by avoiding contact between the optical recording medium and the optical head. It is possible to provide an optical recording medium, an optical head, and an optical recording medium and an optical recording / reproducing apparatus having the optical head, which can perform a highly reliable recording / reproducing operation without giving a problem.

Further, according to the present invention, an optical recording medium, an optical head, an optical recording medium, and an optical recording medium, which are capable of controlling the distance between the optical recording medium and the optical head irrespective of the film structure of the optical recording medium, are provided. An optical recording / reproducing device can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of an optical disc 10 having a transparent conductor 4 on a transparent cover layer 3 according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of an optical disc 19 having a transparent magnetic body 5 patterned on a transparent cover layer 3 according to a second embodiment of the present invention.

FIG. 3A is a cross-sectional view illustrating a configuration of an optical head 12 having an optical head conductor or an optical head magnetic material and a positional relationship with an optical disk according to a third embodiment of the present invention. It is. FIG. 3B is a plan view showing the configuration of the optical head 12 shown in FIG. 3A as viewed from the lens bottom surface 31 side.

FIG. 4 is a block diagram showing an overall configuration of an optical recording / reproducing apparatus having an optical disk and an optical head according to a fourth embodiment of the present invention.

5 is a data processing system 1 of the optical recording / reproducing apparatus shown in FIG.
FIG. 6 is a block diagram showing a detailed configuration of No. 6;

FIG. 6A is a circuit diagram showing an example of a configuration (RC circuit) of a capacity detection system 17 of the optical recording / reproducing apparatus shown in FIG. FIG. 6B is a circuit diagram showing an example of the configuration (RLC circuit) of the capacity detection system 17 of the optical recording / reproducing apparatus shown in FIG.

FIG. 7A is a graph showing an example of a relationship between a capacitance C between a transparent conductor 4 and an optical head conductor 9 and a distance d. FIG. 7B is a graph showing an example of the relationship between the voltage drop V across the resistor R and the distance d in the circuit configuration shown in FIG.

FIG. 8 is a sectional view showing an example of the configuration of a read-only optical disc.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2, 33 Information recording layer 3 Transparent cover layer 4 Transparent conductor 5 Transparent magnetic material 6 First focus lens 7 Second focus lens 8 Casing 9 Conductor (optical head conductor) 10, 19 Optical disk (optical recording medium) DESCRIPTION OF SYMBOLS 11 Voice coil motor 12 Optical head 13 Light source 14 Beam splitter 15 Photodetector 16 Data processing system 17 Capacity detection system 18 Position control system 21 Reflection layer 22 Upper interference layer 23 Recording layer 24 Lower interference layer 32 Spindle motor

Claims (7)

[Claims] 1. A substrate, an information recording layer disposed on the substrate, on which information to be recorded / reproduced by irradiating a light beam is recorded, and a transparent cover layer disposed on the information recording layer. And an optical recording medium comprising: a transparent conductor disposed on the transparent cover layer. 2. A substrate having projections and depressions on which information reproduced by irradiating a light beam is recorded, a reflection layer disposed on the projections and depressions of the substrate, and a transparent cover disposed on the reflection layer. An optical recording medium comprising a layer and a transparent conductor disposed on the transparent cover layer. 3. A substrate, an information recording layer disposed on the substrate, on which information to be recorded and reproduced by irradiating a light beam is recorded, and a transparent cover layer disposed on the information recording layer. And an optical recording medium comprising: a transparent magnetic material disposed on the transparent cover layer. 4. A substrate having projections and depressions on which information reproduced by irradiating a light beam is recorded, a reflection layer disposed on the projections and depressions of the substrate, and a transparent cover disposed on the reflection layer. An optical recording medium comprising: a layer; and a transparent magnetic body disposed on the transparent cover layer. 5. A distance between a focus lens for forming an image of the light beam inside the optical recording medium according to claim 1 and the transparent conductor fixed to the focus lens. An optical head conductor that makes an electrical interaction according to the following. 6. A distance between a focus lens for imaging the light beam inside the optical recording medium according to claim 3 or 4, and the transparent magnetic body fixed to the focus lens. An optical head comprising: an optical head magnetic material that performs magnetic interaction according to 7. An optical recording / reproducing apparatus for performing optical recording / reproduction by irradiating a light beam to the optical recording medium according to claim 1 or 2, wherein the optical recording medium is arranged to face the transparent conductor. An optical head according to claim 5, a capacitance detection system for detecting a capacitance between the transparent conductor and the optical head conductor, and the optical recording medium and the optical head using the capacitance. An optical recording / reproducing apparatus, comprising: a position control system that controls a distance of the optical recording / reproducing apparatus.