JP2854187B2 - Optical recording medium and information recording / reproducing device - Google Patents

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 information recording / reproducing apparatus which have a tracking groove and which meander the groove in accordance with address information.

[0002]

2. Description of the Related Art Conventionally, in an optical memory for recording and reproducing information using light, a recording film made of a perpendicular magnetization film is used as a recording medium, and a magnetic field is applied while irradiating a laser beam.
Magneto-optical disks for recording information by making the magnetization in a light spot upward or downward have been put to practical use.

As shown in a plan view of FIG. 4A and a vertical sectional view of FIG.
.. Are provided so that the light spot 52 can accurately follow the spiral track. The width of the groove 51 is set according to the track pitch. When the track pitch is set to, for example, 1.6 μm, the width of the groove 51 is set to 1 to 1.2 μm.

The grooves 51 are formed so as to meander (wobble) in the radial direction in accordance with the address information of the track. By extracting the component of the meandering frequency from the tracking signal, the light spot 52 is scanned. Track information can be obtained.

Recording and reproduction of information are performed on tracks matching the grooves 51. The track pitch is set to about the diameter of the light spot 52,
The diameter of 2 is determined by the wavelength of the laser light and the numerical aperture of the objective lens that converges the laser light to the light spot 52. The wavelength of the laser light is usually 780 to 830.
nm, and the numerical aperture of the objective lens is 0.45 to 0.6. Therefore, the diameter of the light spot 52 is 1.2 to
1.4 μm, and the track pitch is 1.4 to 1.6 μ
m. Therefore, the size of the recording domain whose magnetization is upward or downward is at least 0.8 μm.
About.

In recent years, by making the recording film of this magneto-optical disk a multilayer structure, a magnetic super-resolution (Ma
There is a measure to improve the recording density by forming a recording domain that is much smaller than the size of the light spot by giving the effect of the G.sub.nic super resolution. By using this magnetic super-resolution, it is possible to stably form a recording domain having a size of about 1/2 as described above. Therefore, the recording density can be dramatically improved. This magnetic super-resolution is described, for example, in Journal of the Japan Society of Applied Magnetics, Vo 1.15, No. 5,1991 p
p. 838-845 is detailed.

[0007]

However, in the above-mentioned conventional configuration, when the track pitch is set to about 0.8 μm, there is a problem that accurate tracking cannot be performed because the tracking signal becomes weak. .

Further, since it becomes difficult to extract the meandering frequency component from the tracking signal, there is a problem that accurate address information cannot be obtained.

[0009]

According to the first aspect of the present invention, there is provided an optical recording medium for recording information to solve the above-mentioned problems.
In an optical recording medium on which a track is formed,
It is characterized in that only one of the lateral ends of the track is meandering .

According to a second aspect of the present invention, there is provided an optical recording medium comprising : a track for recording information;
In the optical recording medium formed, the address information is
It is recorded by one meander of the widthwise side edge of the track.
It is characterized in that it comprises Te.

An optical recording medium according to a third aspect of the present invention is the optical recording medium described above.
In order to solve the problem of, the groove, between the groove
In an optical recording medium having lands, the address information is
One meander of adjacent sidewalls in the groove
Is recorded.

An optical recording medium according to a fourth aspect of the present invention is characterized in that
In order to solve the above problem, the optical recording medium according to claim 3
In this case, the average value of the width of the grooves is
Is set to be equal to the average land width
It is characterized by that.

[0013] The optical recording medium according to the invention of claim 5 is characterized in that:
The light according to claim 1, 2, or 3, for solving the problem of (1).
In the recording medium, the meandering amplitude of the meandering side wall is ± 3.
The range is from 5 nm to ± 50 nm.
You.

[0014]

According to a sixth aspect of the present invention, there is provided an information recording / reproducing apparatus, in which a track for recording information is formed by having a groove, and only one of side edges in the width direction of the track is provided. An information recording / reproducing apparatus for recording or reproducing information on or from an optical recording medium meandering, comprising means for causing a light spot to follow the track, and means for detecting a tracking signal of the light spot And means for obtaining address information by extracting the meandering frequency component at the meandering side end from the tracking signal.

According to a seventh aspect of the present invention, there is provided an information recording / reproducing apparatus, wherein a track for recording information is formed by having a groove, and only one of the lateral ends of the track in the width direction is provided. An information recording / reproducing apparatus for recording / reproducing information on / from an optical recording medium meandering, comprising means for causing a light spot to follow the track, and means for detecting the amount of reflected light of the light spot And means for obtaining address information by extracting the meandering frequency component of the meandering side end from the reflected light amount.

[0017]

According to the optical recording medium of the present invention, the track width
Is configured to meander one of the side edges of the
Can be improved. Also, accurate address information can be obtained.

Further , according to the information recording / reproducing apparatus of the present invention,
For example, one of the meandering side edges in the width direction of the track of the optical recording medium
Can reliably retrieve the information recorded by
You.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a magneto-optical disk according to this embodiment.
As shown in the plan view of (a) and the longitudinal sectional view of (b), spiral or concentric grooves 1 are provided. The average value of the width of the groove 1 and the average value of the width of the lands 2 between the grooves 1 and 1 are set to be equal to each other and equal to the tag pitch.

One of the side walls 1a of the grooves 1 ...
Are formed so as to meander in the radial direction of the magneto-optical disk according to the address information of the track. Side wall 1a ...
Is set to a frequency higher than the tracking frequency of a tracking servo system (not shown) and lower than the recording frequency at the time of recording.

In the above configuration, information is recorded on the tracks on the grooves 1 and the tracks on the lands 2. Therefore, one side wall 1 of the groove 1.
a ... are one of the side edges in the width direction of the track. Whether the light spot 3 follows the track on the groove 1 or the track on the land 2 can be easily selected by inverting the polarity of the tracking signal. The tracking signal is obtained by, for example, a push-pull method.

The address information of the track being scanned by the light spot 3 is obtained by extracting the meander frequency component of the side walls 1a from the tracking signal.

That is, when the light spot 3 is made to follow the groove 1, for example, the meandering frequency is higher than the following frequency. Therefore, the light spot 3 does not track on the center line connecting the two division points of the width of the groove 1. , Groove 1
Tracking on the line connecting the two division points of the average width of.
Therefore, a tracking error equal to half the meandering amplitude of the groove 1 always occurs. Therefore, if this is extracted from the tracking signal, a signal component having a meandering frequency can be obtained. The same applies to the case where the light spot 3 is made to follow the land 2.

Since the tracking error becomes half the meandering amplitude, the meandering amplitude must be doubled to obtain a signal component having the same meandering frequency as the conventional one. For example, if the conventional meandering amplitude is ± 30 nm,
This needs to be ± 60 nm.

However, the width of the groove 1 and the land 2
Is 0.8 μm, the magnitude of the tracking signal is 1.4 times the magnitude of the tracking signal when the width of the groove 1 and the width of the land 2 are 1.2 μm and 0.4 μm, respectively. Therefore, the meandering amplitude may be approximately 1.4 times (≒ 2 / 1.4) the conventional value.

The meandering amplitude may be approximately 1.1 times that when the width of the groove 1 and the width of the land 2 are 1.3 μm and 0.3 μm, respectively. Further, the width of the groove 1 and the width of the land 2 are 1.1 μm and 0.5 μm, respectively.
Compared with the case of m, the meandering amplitude may be approximately 1.7 times.

Therefore, in order to extract a signal component having a meandering frequency substantially the same as the conventional one, the meandering amplitude must be ± 3.
What is necessary is just to set it in the range of 5 nm to ± 50 nm.

In the magneto-optical disk of this embodiment, since only one side wall 1a of the groove 1 is meandering, the diameter of the light spot 3 is set to be larger than the track pitch and smaller than twice the track pitch. If it does, the light spot 3 will not simultaneously hit the two meandering side walls 1a. Therefore, accurate address information can be obtained.

In this embodiment, the address information of the track corresponding to the groove 1 is stored in the side wall 1 of the groove 1.
Although the address information is the same as the address information of the track corresponding to the land 2 adjacent to the side a, these tracks can be easily selected by the tracking servo system as described above, so that it is easy to specify a specific track.

When information is recorded on the above-described magneto-optical disk by using the magnetic super-resolution effect, the diameter of the recording domain is set to 0.
It can be about 4 μm. Therefore, the track width must be 0.8
μm (ie, the width of the groove 1 and the land 2
Are set to 0.8 μm), recording and reproduction can be easily performed. Further, since the track pitch can be reduced to half of 0.8 μm from the conventional 1.6 μm, the recording density can be greatly improved. Moreover, a large tracking signal can be obtained, and accurate address information can be obtained.

Further, when the wavelength of the laser beam used for recording and reproduction is shortened, the light spot 3 can be made smaller. For this reason, the track pitch can be further reduced. For example,
When the wavelength of the laser light is changed from 830 nm to 458 nm, the track pitch can be increased by (458/830) times.
That is, the recording density can be almost doubled.

In the above embodiment, the meander frequency signal component is extracted from the tracking signal. However, the meander frequency signal component may be extracted from the amount of reflected light from the magneto-optical disk. That is, when the width of the groove 1 or the land 2 is narrow, the reflected light is weak, and when the width is wide, the reflected light is strong. Therefore, if the change in the amount of reflected light from the light spot 3 is extracted, a signal component having a meandering frequency can be obtained.

The mastering process of the above-mentioned magneto-optical disk will be described below with reference to FIG.

First, a photoresist 5 is applied to one surface of the glass substrate 4 (FIG. 3A). Then, the laser light is converged on the photoresist 5 by the objective lens 7,
The photoresist 5 is exposed to a desired pattern of the groove 1 (FIG. 2B). By developing this,
Unnecessary photoresist 5 is removed, and a desired pattern is formed with photoresist 5a remaining on glass substrate 4 (FIG. 3C).

Next, a conductive thin film 8 is sputtered on the pattern made of the photoresists 5a.
It is formed by electroless plating or the like (FIG. 4D). As a material of the thin film 8, Ni, Ta, Cr or an alloy thereof, or a composite film thereof is used. Then, the thin film 8
A metal layer 9 made of, for example, Ni is formed on the upper surface by electroforming (FIG. 9 (e)), and when this is peeled off, a stamper 10 consisting of the metal layer 9 and the thin film 8 formed thereon is obtained (FIG. Figure (f).

By molding plastic such as polycarbonate using the stamper 10, a substrate for a magneto-optical disk having a desired groove 1 is manufactured. When a recording medium is formed on this substrate, the above-described magneto-optical disk is obtained.

In the step of exposing the photoresist 5 to the pattern of the groove 1, two laser beams are used. These laser beams form two light spots 6a and 6b on the photoresist 5. Light spot 6a
FIG. 1 (a) shows the relationship between the groove 6b and the groove 1 formed by the light spots 6a and 6b.

When the spiral groove 1 is formed, the light spots 6a and 6b are moved in a spiral relative to the glass substrate 4, but the light spot 6a is moved in a spiral in accordance with the address information. Vibration also occurs in the radial direction of the magneto-optical disk. Thereby, a pattern of the groove 1 in which one of the side walls 1a meanders can be formed on the photoresist 5 according to the address information.

For example, if the diameter of each of the light spots 6a and 6b is 0.4 μm and the track pitch is 0.8 μm, the light spots 6a and 6b average 0.4 μm from each other.
Only in the radial direction of the magneto-optical disk. Further, the diameter of each of the light spots 6a and 6b is set to 0.5 μm,
When the track pitch is 0.7 μm, the light spot 6a
6b are spaced apart from each other by 0.2 μm on average in the radial direction of the magneto-optical disk.

FIG. 3 shows an example of a recording apparatus for exposing the photoresist 5 to the pattern of the groove 1. As shown in FIG.

The recording apparatus has a laser light source 11a for exposing the photoresist 5 and a laser light source 11b for focusing the objective lens 7. As the laser light source 11a, for example, an argon laser is used, and as the laser light source 11b, for example, a He-Ne laser is used.

The laser light from the laser light source 11a is
After the optical noise is reduced by the noise suppression device 12 a, the light is reflected by the mirrors 19 and 20 and enters the beam splitter 21. Laser beam splitter 2
1 and divided into two optical modulators 18a and 1a, respectively.
8b. As the optical modulators 18a and 18b, for example, acousto-optic devices can be used. In that case, it is necessary to arrange convex lenses 22 for convergence before and after the optical modulators 18a and 18b, respectively.

The light beam passing through the light modulator 18a is incident on the light deflector 23, and is reflected by the prism mirror 24 in a right angle direction. As the light deflector 23, for example, an element whose traveling direction can be changed by using an electro-optic effect or an acousto-optic effect can be used. On the other hand, the light beam passing through the light modulator 18b is incident on the (1/2) wavelength plate 25, and the polarization plane is rotated by 90 degrees.

After these light beams are recombined by the polarizing prism 26, they are expanded to an appropriate light beam diameter by the beam expander 27, reflected by the dichroic mirror 15, and incident on the objective lens 7. Then, the light is converged by the objective lens 7 on the photoresist 5 on the glass substrate 4 as light spots 6a and 6b.

The optical modulators 18a and 18b are
Each is controlled by the drivers 28a and 28b. The light deflector 23 is controlled by a driver 29.

On the other hand, the laser light from the laser light source 11b is reduced in optical noise by the noise suppression device 12b, and then the polarization beam splitter 13, (1/4)
The light passes through the wave plate 14 and the dichroic mirror 15 and is converged on the photoresist 5 on the glass substrate 4 by the objective lens 7.

The reflected light is condensed by the objective lens 7, passes through the dichroic mirror 15, the (１ ／) wavelength plate 14, and the polarization beam splitter 13, and is subjected to four-division light detection by the objective lens 16 and the cylindrical lens 17. Container 18
Is converged. A focus servo signal is generated based on a signal from the photodetector 18, and a focus servo system (not shown) drives the objective lens 7 in a focus direction. Thus, the focus of the objective lens 7 is always focused on the photoresist 5 on the glass substrate 4 rotated by the spindle motor 30.

In the above configuration, first, the light spot 6
Positioning a is performed. That is, as described above, the magnitude of the DC voltage applied to the optical deflector 23 by the driver 29 so that the light spot 6a is arranged at a position spaced apart from the light spot 6b by a predetermined average distance in the radial direction. , The setting angle of the prism mirror 24 is adjusted.

Then, a voltage obtained by superimposing a signal voltage having a meandering frequency on the DC voltage is applied from the driver 29 to the optical deflector 23. Thereby, the light spot 6a can be vibrated in the radial direction according to the meandering frequency.

The light spots 6a and 6b can be turned on and off by applying a voltage from the drivers 28a and 28b to the light modulators 18a and 18b.

In the above embodiments, a magneto-optical disk, a method for manufacturing the same, and an information recording / reproducing apparatus have been described. However, the present invention can be widely applied to an optical disk having a meandering groove, a method for manufacturing the same, and an information recording / reproducing apparatus .

[0053]

As described above, the optical recording medium according to the present invention has a configuration in which one of the side edges in the width direction of the track is meandering.
Therefore, the recording density can be improved. Further, there is an effect that accurate address information can be obtained.

In the information recording / reproducing apparatus according to the present invention,
The meandering of one side of the width direction of the track of the recording medium
That the recorded information can be retrieved reliably.
It works.

[Brief description of the drawings]

FIGS. 1A and 1B show a schematic configuration of a magneto-optical disk having a meandering groove according to the present invention, wherein FIG. 1A is a schematic plan view, and FIG. 1B is a schematic longitudinal sectional view taken along a broken line in FIG. .

FIG. 2 is an explanatory diagram showing a mastering process of a substrate used in the magneto-optical disk of FIG.

3 is a block diagram schematically showing a recording apparatus used in a photoresist exposure step of the mastering process of FIG. 2;

4A and 4B show a schematic configuration of a conventional magneto-optical disk having a meandering groove, in which FIG. 4A is a schematic plan view, and FIG. 4B is a schematic longitudinal sectional view taken along a broken line in FIG.

[Explanation of symbols]

 Reference Signs List 1 groove 1a side wall 2 land 3 light spot 4 glass substrate 5 photoresist 5a photoresist 6a light spot 6b light spot 7 objective lens

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) G11B 7/24 561 G11B 7/00

Claims (7)

(57) [Claims] 1. An optical recording medium having a track for recording information formed thereon, wherein only one of the side edges in the width direction of the track is meandering. 2. An optical recording medium in which a track for recording information is formed, wherein address information is recorded by meandering one of the side edges in the width direction of the track. 3. An optical recording medium having grooves and lands between the grooves, wherein address information is recorded by meandering one of side walls adjacent to each other in the grooves. 4. The optical recording medium according to claim 3, wherein the average value of the width of the groove is set to be equal to the average value of the width of the land between the grooves. 5. The meandering amplitude of the meandering side wall is ± 35 nm.
4. The optical recording medium according to claim 1, wherein the optical recording medium is within a range of ± 50 nm. 6. An information recording device for recording or reproducing information on an optical recording medium in which a track on which information is recorded is formed by having a groove, and only one of the side edges in the width direction of the track is meandering. A reproducing apparatus, comprising: means for causing a light spot to follow the track; means for detecting a tracking signal of the light spot; extracting a meandering frequency component at the meandering side end from the tracking signal; An information recording / reproducing apparatus comprising: means for obtaining information. 7. An information recording device for recording or reproducing information on an optical recording medium in which a track on which information is recorded is formed by having a groove, and only one of the lateral ends of the track is meandering. A reproducing apparatus, comprising: means for causing a light spot to follow the track; means for detecting the amount of reflected light of the light spot; extracting the meandering frequency component of the meandering side end from the reflected light amount; An information recording / reproducing apparatus comprising: means for obtaining information.