JP2999994B2 - Optical recording / reproducing device and optical recording medium - 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 / reproducing apparatus and an optical recording medium capable of improving recording density.

[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 in, for example, Journal of the Japan Society of Applied Magnetics, Vol. 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]

An optical recording / reproducing apparatus according to the present invention is an optical recording / reproducing apparatus for recording / reproducing information on / from an optical recording medium having both grooves and lands as recording tracks. It has a designating means for designating a specific recording track by using address information common to both recorded at track boundaries.

Further, the specification means specifies the specific recording track also using a tracking signal.

In an optical recording / reproducing apparatus for recording / reproducing information on / from a recording track of an optical recording medium, address information common to both recorded at the boundary between adjacent recording tracks and a tracking signal are used. , Characterized by having a designating means for designating a specific recording track.

Further, the optical recording medium of the present invention is characterized in that, in an optical recording medium having both a groove and a land as recording tracks, address information common to both recording tracks is recorded at a boundary between adjacent recording tracks. And

The operation of the present invention will be described below. According to the optical recording / reproducing apparatus of the present invention, accurate address information can be obtained even when the track pitch is reduced, and a specific recording track can be easily specified.

Further, in the optical recording medium of the present invention, the recording density can be improved.

[0015]

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 land 2 between the grooves 1 and 1 are set to be equal to each other and equal to the track pitch.

One of the side walls 1a of the grooves 1 is formed.
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 arrangement, information is recorded on the tracks on the grooves 1 and the tracks on the lands 2. That is, both the groove 1 and the land 2 are recording tracks. 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 meandering 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.

Further, 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.
The address information becomes the same as the address information of the track corresponding to the land 2 adjacent to the side a. However, as described above, these tracks can be easily selected by the tracking servo system. That is, a specific track can be easily designated by using both the address information recorded by the meandering of the side wall 1a at the boundary between the groove 1 and the land 2 and the tracking signal.

When information is recorded on the above-mentioned 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.

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 light reflected 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. 1A). 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 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 ((e) in the same figure), and when this is peeled off, a stamper 10 composed of the metal layer 9 and the thin film 8 formed thereon is obtained (FIG. Figure (f).

By molding a 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 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.

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 having passed through the light modulator 18a enters 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.

These light beams are recombined by the polarizing prism 26, 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, after the laser light from the laser light source 11b is reduced in optical noise by the noise suppression device 12b, 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 divided into four 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 and a method for manufacturing the same have been described. However, the present invention can be widely applied to an optical disk having a meandering groove and a method for manufacturing the same.

[0049]

According to the optical recording / reproducing apparatus of the present invention, accurate address information can be obtained even when the track pitch becomes small, and a specific recording track can be easily specified.

Further, in the optical recording medium of the present invention, the recording density can be improved.

[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 Continuation of the front page (51) Int.Cl. ⁷ Identification code FI G11B 11/10 586 G11B 11/10 586G JP-A-64-35727 (JP, A) JP-A-4-47536 (JP, A) JP-A-62-89236 (JP, A) JP-A-58-23333 (JP, A) JP-A-57-138065 (JP, A) JP-A-2-68721 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B ^7/ 00-7/013 G11B ^7/ 24- 7/26 G11B 11/00-13/06

Claims (4)

(57) [Claims] 1. An optical recording / reproducing apparatus for recording / reproducing information on / from an optical recording medium having both grooves and lands as recording tracks, comprising: address information common to both recorded at the boundary between adjacent recording tracks; An optical recording / reproducing apparatus characterized by having a designation means for designating a specific recording track by using the above. 2. The optical recording / reproducing disk device according to claim 1, wherein the specifying means specifies the specific recording track also using a tracking signal. 3. An optical recording / reproducing apparatus for recording / reproducing information on / from a recording track of an optical recording medium, using address information common to both recorded at the boundary between adjacent recording tracks and a tracking signal. An optical recording / reproducing apparatus, comprising: a designation unit for designating a specific recording track. 4. An optical recording medium having both grooves and lands as recording tracks, wherein address information common to both recording tracks is recorded at the boundary between adjacent recording tracks.