JP2906703B2 - Information record carrier and its 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 information recording carrier such as an optical disk capable of recording high-density information, which is used as a storage unit of a computer system, and a recording / reproducing apparatus therefor.

[0002]

2. Description of the Related Art In recent years, a recording / reproducing apparatus using an optical disk as a storage unit of information of a computer system has been improved. In particular, there is a great demand for high-density recording of optical disks for miniaturization. When performing high-density recording on this optical disc, the recording spot can be narrowed down to the physical diffraction limit limited by the wavelength of the recording laser beam and the numerical aperture of the recording lens (hereinafter referred to as NA). The density is limited. In order to improve the recording density, conventionally, a recording laser having a slightly shorter wavelength or a lens having a larger NA has been used. Further, a method of reducing the size of the zero-order portion of the Airy disk of the focused spot using the principle of super-resolution has been attempted. FIG. 10 shows a conventional example. The shape of the spot formed on the focal plane by the recording focusing lens 36 shown in FIG. 10A is such that a light shield 37 is placed on the optical axis in the light beam incident on the lens 36 and the light intensity around the lens is centered. If the area is larger than the area, a spot having an intensity distribution as shown in FIG. 10B is obtained. Light shield 37
0th order light intensity distribution 40 with air (Airy disk)
The width (spot diameter) can be reduced as compared with the intensity distribution 38 in the case where there is no. However, the distribution of the primary light increases in intensity as shown by the intensity distribution 41 as compared with the intensity distribution 39 without the shield 37. As a result, the recording density can be improved by the smaller Airy disk diameter,
As the primary light intensity increases, crosstalk to adjacent tracks increases. FIG. 11 shows another conventional example. Japanese Patent Application Laid-Open No. 57-105828 proposes a method of increasing the recording density by forming the structure of a guide groove on an optical disk into a V-shape and using the slope of each groove as a recording area. As a method of forming a continuous V-shaped groove, there is a method of mechanically forming a groove on a metal plate. However, this method requires a metal disk having high precision and high cutting properties, and it is difficult to record track addresses and the like.

[0003]

In order to improve the recording density, it is necessary to reduce the recording spot size or reduce the recording track pitch. However, in the conventional method, when trying to increase the recording density, crosstalk occurs and there is a problem in productivity. In the present invention, the recording laser wavelength can be made shorter than before,
An information recording device that can reduce the recording track pitch without increasing the NA of the recording lens, and can record and reproduce information signals while suppressing crosstalk to a practical level.
An object of the present invention is to provide a record carrier and a recording / reproducing apparatus therefor.

[0004]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a substrate and a spiral concave and convex formed on the substrate.
Structure tracking guide and optical information can be stored
The recording formed on the surface with the tracking guide
Layer and tracking guide concave (or convex) structure convex
(Or concave) structure, and a discontinuous portion to be inverted.
Recording layer in the area including the boundary of the tracking guide on the plate
With the steps of the uneven structure of the tracking guide retained
An information record carrier on which optical information is recorded in a state .

[0005] Further, the present invention is to achieve the above object.
In addition, recording to be recorded and reproduced using such an information record carrier
It is a playback device. In particular, the light flux for recording and reproduction is collected on the recording layer.
Recording and reproducing means for recording and reproducing information,
Approximately at the center of the boundary of the tracking guide of the information record carrier
And a guide means for guiding to a portion of the recording layer.
Record and play back information in the area around the King Guide boundary
Is a recording and reproducing apparatus to be.

[0006]

In general, upon recording, the recording layer usually has a recording gamma characteristic (a rising portion of a change in the recording substance with respect to the recording power), and the recording cannot be started unless light having a predetermined intensity or more is applied. Have. Therefore, using a recording spot of a light beam having an intensity distribution close to a Gaussian distribution on the optical disk surface, a part of the intensity distribution can be written according to the gamma characteristic of the recording layer. Thus, recording pits as optical recording can be formed. However, when reading signals from the optical disk surface, recorded information is reproduced by diffracted light from an area irradiated with a spot of a light beam for reproduction in accordance with the intensity distribution. Therefore, a minute pit can be recorded, but if it is reproduced from a reproduction spot by a light beam having the same intensity distribution as the recording, large crosstalk occurs. Therefore, the present invention uses a spot having the same intensity distribution as in the past for recording and reproduction, irradiates a light flux to the boundary of the tracking guide on the optical disk surface, and performs recording and reproduction to produce a reflected diffracted light between the information reproduction track and the adjacent track. Intensity distributions are provided in different directions spatially, thereby significantly reducing crosstalk.

That is, when light is made incident on a reflecting surface having a concavo-convex structure on the order of the wavelength of light or a light-transmitting object having a phase structure, reflected light or transmitted light is diffracted by the structure.
Causes interference. In particular, when a light spot crosses a step portion such as a boundary portion of a tracking guide, diffraction occurs in various directions depending on the shape and height of the step. By appropriately selecting the height of this step, the direction of the step with respect to the traveling direction of the light spot by the light beam, that is, the case where the step is a positive step and the case of a negative step, the diffraction direction is relative to the incident light beam direction. Swing in opposite directions. By making areas having a positive step and a negative step as recording areas adjacent to each other, the diffraction directions can be made different. Therefore, at the boundaries on both sides of the tracking guide, the direction of the steps is opposite, so even if the distance between adjacent tracks is reduced by arranging photodetectors in each diffraction direction,
High-quality signal recording and reproduction with little crosstalk can be performed.

[0008]

FIG. 1 shows a flat information recording carrier according to one embodiment of the present invention. Tracking guide 2 which is a so-called guide groove
In addition, the information signal 4 is provided on the plate-like substrate 1 in which the width of the land portion, which is an isolation band provided between the adjacent tracking guides 2, is formed substantially equal to the edges 5, 6 at the left and right boundaries of the tracking guide 2. Shows the state of the portion of the optical disk on which is recorded on the recording layer 3. Reproduced signal information obtained by irradiating a light beam for reproducing the information signal 4 appears as a change in the intensity of diffracted light when the recording layer 3 is a phase change type or a perforated type. Appears as a rotation of the plane of polarization.

When the focused laser light is applied to the edges 5 and 6 of the tracking guide 2, the light is diffracted and interfered by the edges 5 and 6 to determine the far field distribution. FIG. 2 shows a near-field (on the disk surface) coordinate system (x, x) when a recording / reproducing spot is irradiated on the edge 6 of the tracking guide 2 through the lens 7.
y) and the coordinate system (x, y) of the far field (lens surface). Assuming that the amplitude reflectance at x = x ₀ , y = 0 is r (x, x ₀ ), r (x, x ₀ ) = u (xx− ₀ ) exp [ikG (x)] (1) When G (x) = 2h, | x | ≦ a / 2 When G (x) = 0, it can be expressed as | x |> a / 2. Here, u (x) represents the amplitude distribution of the spot on the disk surface, h represents the groove depth, a represents the groove width, and k = 2π / λ.

The amplitude of the far-field diffracted light in the θ direction is

[0011]

(Equation 1)

## EQU1 ## Here, if the focal length of the recording / reproducing lens is f and the numerical aperture is NA, then X = f · sin θ, and (Equation 1) becomes

[0013]

(Equation 2)

## EQU1 ## Where a ₁ = (− x ₀ −a / 2)
kNA, a ₂ = (− x ₀ + a / 2) kNA, and the intensity distribution is the square of the absolute value of (Equation 2), | R (x / f, x ₀ ) | ²
Can be obtained by FIG. 3 shows the calculation results. When there is a spot on the right edge 6, the far field distribution is as shown in FIG. 3B, and when there is a spot on the left edge 5, the far field distribution is as shown in FIG.
It becomes like B of (b). It can be seen that the amount of change in the intensity distribution with respect to the incident optical axis becomes maximum when the optical groove depth is λ / 8 in the case of a rectangular groove. If two light detectors are arranged at positions where the intensity of the diffracted light is maximized when the spot traces the right edge 6 and the left edge 5, information from each part can be sufficiently separated and detected. can do. FIG. 3C shows an example in which the photodetectors (A ₁ ) and (A ₂ ) are arranged for the edge 6, and the photodetectors (B ₁ ) and (B ₂ ) are arranged for the edge 5. This reproduced signal information appears as a change in the intensity of diffracted light when the recording layer is a phase change type or a perforated type,
In the case of a magneto-optical film, it appears as rotation of the plane of polarization. When a groove is recorded on a glass master coated with a photoresist by a laser cutting machine, the groove edge portion is not always a perfect rectangle but always has a slope. In the case of having a slope, the groove depth has the same result as apparently shallower than that of the rectangular case. Therefore, it is desirable to slightly increase the groove depth as the inclination of the groove edge increases.

[0015] For the recording layer, it is preferable that the groove edge has a slope rather than a sharp edge, because it has higher environmental resistance,
It is desirable in view of the characteristics of repeated recording and erasing. 1
There are two edges per book groove, and when tracking, in order to follow both edges, for example, FIG.
As shown in (1), it is necessary to make the spot jump to the adjacent edge every round. By doing so, it is possible to trace all edges in the disk surface. In order to be able to trace all edges without jumping to an adjacent edge for each rotation, a master photoresist is used for each rotation, as shown in FIG. At the time of manufacture, the polarity of the groove, that is, the tracking guide 2 may be changed from a concave to a convex. For this purpose, if the cutting laser beam is repeatedly turned on and off for each rotation of the master, a spiral edge having a different polarity for each rotation of the disk can be obtained for the information recording / reproducing recording beam. A discontinuous portion 8 occurs in the polarity conversion portion. FIG. 5B is an enlarged view of the polarity switching section. The spot 9 following the left edge 5 of the groove follows the right edge 6 of the groove via a discontinuous portion 8 which is a polarity switching section of the tracking guide 2.

FIG. 6 shows an embodiment of an optical disk recording / reproducing apparatus according to one embodiment of the flat information recording carrier of the present invention. As components, a beam splitter 22 to which a laser beam 11 is input from a laser generating unit (not shown) as a laser generating unit, and a laser beam 12 which has passed through the beam splitter 22 to be input to the flat substrate 1 of the optical disc. The lens 7 focuses the light beam of the laser beam 13 on the track 23 for recording and reproducing the above-described optical information and irradiates it as a spot. The diffracted light reflected by the optical information recorded on the track 23 is transmitted through the lens 7 to the beam splitter. The photodetectors 18, 19, 20, 21 receive the laser beam 14 as diffracted light reflected by the laser beam 22 and containing reproduction information, and a differential amplifier 24 to which the outputs of the photodetectors 18, 19, 20, 21 are input. , 25, and summing amplifiers 27, 28, and a polarity switch 26 for selecting and outputting the outputs of these amplifiers. Than it is. The related operation of the component will be described.

The laser beam 11 is applied to a beam splitter 22,
The light passes through the recording / reproducing lens 7 and is focused on the track 23 on which the recording layer 3 is formed. The light beam reflected by the recording layer 3 is applied to the photodetectors 18 and 1 arranged on the far field surface.
Light is incident on 9, 20, 21. The fact that the light intensity distribution in the far field greatly changes depending on which of the edges 5 and 6 of the tracking guide 2 the light spot is located has already been described with reference to FIG. Therefore, for example, to follow the right edge 5, the photodetectors 18 and 19 are used for the opening of the reproducing lens, and to follow the left edge 6, the output signals of the photodetectors 20 and 21 are used. .
The outputs from the photodetectors 18 and 19 are connected to a subtractor 24, and the output signals from the photodetectors 20 and 21 are connected to a subtractor 25 to obtain a tracking signal. The polarity is switched by the tracking polarity switch 26 depending on which side of the edge of the tracking guide 2 is to be followed. Also R
The F signal is obtained by adding the outputs of the photodetectors by adders 27 and 28. This is also switched by the polarity switch 26 depending on which edge follows.

Next, switching between the tracking detector and the tracking polarity will be described. It has already been described as shown in FIG. 3 that when the optical depth of the groove is approximately λ / 8, the deviation of the diffracted light from the left and right edges of the groove is greatest. As shown in FIG. 7, the far field distribution of the diffracted light reflected from the optical disk is a result of the interference of the superposition of the 0th-order light (15), the + 1st-order light (16), and the -1st-order light (17). Above the photodetectors 18, 19, 20, 21
The relationship with the position appears as shown in the figure. Depending on whether the tracking guide 21 follows the right edge or the left edge of the groove, the overlap between the 0th and + 1st orders becomes brighter, and the overlap between the 0th and -1st orders becomes brighter. For example, to follow the right edge 5 of the groove, the tracking detectors 18 and 19 are arranged with respect to the opening of the reproducing lens, and to follow the left edge 6, the tracking detectors 20 and 21 are arranged. . As shown in FIG. 6, the output from the tracking detector is connected to the differential amplifiers 24 and 25, and the tracking polarity is switched by the polarity switch 26 at the discontinuous portion 8 of FIG. The switching signal of the polarity switch 26 is obtained by a rotation synchronizing signal or the like which is output for each rotation of the disk. RF signal is detected by detector 1
It is obtained by the addition signal of 8, 19 or the addition signal of detectors 20, 21. The track pitch can be reduced most by setting the width of the land portion, which is an isolation band between the groove width of the tracking guide 2 and the remaining adjacent tracking guide 2, to approximately 1: 1. When the recording track pitch is 1 μm to 0.
Even when the width is reduced to 8 μm, crosstalk can be reduced to about −25 dB or less necessary for reproducing data information.

Next, means for forming a wide groove having a width of about 1 μm or more will be described. Increase the peak power of a focused spot with a normal Gaussian distribution to form a wide groove around the base of the intensity distribution, or worsen the focusing of the focused spot and widen the base of the Gaussian distribution to form a wide groove There are methods. However, in these methods, the photoresist is irradiated with a spread laser beam other than in the portion to be exposed, so-called fogging occurs, and the photoresist in an area which should not be exposed is reduced in film thickness. As shown in FIG. 8A, a Gaussian beam 29 having a normal condensed spot has a very large influence on an adjacent region. By combining a plurality of condensed spots as in the method of the present invention, a trapezoidal intensity distribution 30 can be obtained. One embodiment for synthesizing a plurality of spots is shown in FIG. When two beams orthogonal to each other enter the polarization beam splitter 31, the recording lens 3
At the focal plane of No. 2, 30 synthesized intensity distribution spots are obtained. The shape of the intensity distribution can be controlled by changing the angle θ between the two beams. A high-quality wide groove with less fogging can be formed by using a trapezoidal spot with a small spread of skirt. Combining the two beams may be spatial or temporal.

In order to identify a recording track, it is necessary to record a track address. An embodiment of the recording method will be described. When performing wide groove recording by irradiating two beams, as shown in FIG. 9A, one of the beams is turned off, and the other beam is turned on and off. Can be formed. FIG. 9B shows a method of recording the address information 34 when one beam remains on and the other beam is turned on and off. The above is the case where individual addresses are assigned to the right edge and the left edge of the groove. If the right edge of the groove is, for example, an even address and the left edge is an odd address, a set can be represented by one representative address 35 as shown in FIG. 9C. If the tracking polarity is made positive with respect to the representative address, the representative address +
At address 1, if it is negative, the address becomes the same as the representative address, and the address corresponding to the left and right groove edges can be read.

According to the present invention, optical information can be recorded / reproduced on the recording layer at the adjacent edge of the tracking guide 2. Therefore, a plurality of photodetectors are arranged to perform recording / reproducing from the adjacent edge. Can be done simultaneously. Also, even if the step direction of the edge changes in the middle, as described above,
By configuring one photodetector as one set, all adjacent edge information can be detected.

Generally, to form a tracking guide for an optical disc, a so-called guide groove, a photosensitive photoresist is applied to a glass master by a spinner, prebaked, and then focused with an argon laser or He-Cd laser beam. Exposure and recording are performed. Thereafter, a guide groove is formed through a developing process. From there, a metal stamper is made, and a duplicate disc is made with a resin such as polycarbonate or PMMA. A recording layer is formed thereon. This recording layer is recorded / reproduced using not only thermomagnetic recording materials, but also materials that cause a change in reflectance or transmittance due to deformation or melt evaporation, and recording materials such as phase change type, perforated type, and dye materials. Needless to say, the same effect can be obtained by erasing.

[0023]

As described above, by using the edge portion of the tracking guide as the information recording area,
Compared with the conventional recording method, while suppressing the cross-talk low, everyone can be greatly improved recording density
Instead, the tracking guide becomes concave and convex every round.
Without jumping to adjacent edges every lap
You can trace edges . In addition, such a guide groove can be easily formed using a photoresist master ,
In particular, the cutting laser beam is used to rotate the master during production of the master.
By turning it on and off, the tracking guide makes one round
It can be concave and convex every time. The high-density optical disk of the present invention can be applied not only to thermomagnetic recording materials but also to phase change type, perforated type and dye materials.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of an optical disc according to an embodiment of the present invention.

FIG. 2 is a state diagram showing irradiation of a light beam on the optical disk surface of the embodiment.

FIG. 3A is a state diagram showing light beam irradiation in different step directions of the embodiment; FIG. 3B is a graph showing a far-field intensity distribution of diffracted light by the light beam of the embodiment; Front view showing the arrangement of photodetectors

FIG. 4 is a conceptual diagram showing the shape of a tracking guide on the optical disc of the embodiment.

FIG. 5A is a top view showing a shape of a tracking guide on the optical disc of the embodiment; FIG. 5B is a top view showing an enlarged portion of a discontinuous portion of the tracking guide on the optical disc of the embodiment;

FIG. 6 is a block diagram of a main part of a recording / reproducing apparatus for recording / reproducing information on / from an optical disc according to an embodiment of the present invention;

FIG. 7 is a top view showing an arrangement state of the photodetector of the embodiment.

FIG. 8 (a) is a state diagram showing the relationship between the guide groove of the optical disc and the intensity distribution of the light beam for exposure according to one embodiment of the present invention; FIG. 4C is a graph showing the intensity distribution of the exposure beam of the embodiment.

FIG. 9 is a state diagram showing an information recording state of a recording layer of the optical disc according to one embodiment of the present invention.

10A is a state diagram showing a state of a light beam to a conventional optical disc, and FIG. 10B is a graph showing an intensity distribution by the conventional light beam;

FIG. 11 is a partial cross-sectional view showing a state of recording information on the conventional optical disc.

[Explanation of symbols]

 Reference Signs List 1 flat substrate 2 tracking guide 3 recording layer 4 information signal 5, 6 edge

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-177732 (JP, A) JP-A-62-89236 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 7/24 561 G11B 7/00

Claims (10)

(57) [Claims] A substrate and a spiral formed on the substrate
Tracking guide of the uneven structure of the optical memory
Possible and shaped on the surface with the tracking guide
The formed recording layer and the concave (or
A discontinuous portion for inverting a convex (or concave) structure to a convex (or concave) structure, and the recording layer in a region including a boundary of the tracking guide on the substrate ,
An information recording carrier in which the optical information is recorded in a state where a step of the concavo-convex structure is maintained . 2. The step of the concave or convex structure of the tracking guide is 1/1 of the wavelength of light when recording and reproducing optical information.
2. The information recording carrier according to claim 1, wherein the ratio is 9 to 1/6. 3. The optical information recorded on the recording layer, the information recording responsible according to any one of claims 1 to be recorded on the recording layer of approximately 1/2 of the area of the tracking guide width
Body . 4. A tracking guide width, the width of the isolation band provided between the adjacent tracking guide, information recording according to any one of claims 1, 2, 3 which is substantially equal to
Recording carrier . 5. The method according to claim 1, 2, 3, or 4.
A recording / reproducing apparatus for recording / reproducing using an information record carrier. 6. A light beam for recording and reproduction is focused on a recording layer ,
Recording / reproducing means for recording / reproducing information; and guiding means for guiding a substantially central portion of the light beam to a boundary portion of the tracking guide of the information recording carrier , wherein the center of the recording layer is centered on the boundary of the tracking guide. 6. The recording / reproducing apparatus according to claim 5 , wherein information is recorded / reproduced in / from the set area. 7. The recording / reproducing apparatus according to claim 6 , wherein the recording / reproducing means has a plurality of photodetectors, each of which performs recording / reproducing of a portion on a different boundary line of the tracking guide. 8. A recording and reproducing means, provided with two light detection section configured photodetector as a pair two pairs, the two pairs of optical detection
Are disposed out section in the far field distribution of the light diffracted by the light beam for recording and reproduction becomes possible to perform recording and reproduction of the tracking guide adjoining the two boundary of the recording layer according to claim 6 recording according apparatus. 9. The recording reproducing means, two sets Urn <br/> Chi light detecting portions, one of the light detecting portion is concave of the information recording carrier (or convex) configuration
Performs reproduction of the information recording layer on the forming of the tracking guide, claims other light detecting portion is configured to perform the reproduction of the information of the convex (or concave) recording layer on tracking <br/> Gugaido structure 9. The recording / reproducing apparatus according to 8 . 10. A recording / reproducing means for recording data on different boundaries.
Select one of the two photodetectors corresponding to the recording layer.
9. The recording / reproducing method according to claim 8, wherein the switching is performed.
apparatus.