JPH07169102A - Information record carrier - Google Patents

Abstract

PURPOSE:To obtain a higher data density and a higher data transfer rate by recording information using the combination of the beginning and the ending of a mark. CONSTITUTION:It is assumed that N kinds of shapes can be formed for the beginning and the ending of a mark. Thus, the number of combinations of the beginning and ending of the mark is NXN=N<2>. If these combinations are made to correspond to information, N<2> values of multi-value recordings are possible. If N<2>>=2<n>, n multiplexed binary recording is possible. For example, a mark 3 is placed at the center of a track 1 and the shapes of its beginning 4 and an ending 5 are varied for the purposes. Moreover, optical characteristics such as reflectivity, transmissivity and phase differences at the beginning section 4 and the ending section 5 of the mark 3 are used instead of using the shapes. Furthermore, magnetic or magneto-optical characteristics or the positions of the beginning and the ending of a mark are also used for the purposes.

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, an optical card, a magnetic disk, a magnetic card and a magnetic tape. More specifically, the present invention relates to a new information record carrier capable of realizing high data density and high data transfer rate.

[0002]

2. Description of the Related Art Information recording carriers such as optical disks, optical cards, magnetic disks, magnetic cards, and magnetic tapes, which can store high-density data and can process information at high speed, are widely used as computer memories. Especially diameter 5.2
For a 5-inch optical disc, a write-once type that allows information to be written only once and a magneto-optical type that allows information to be rewritten have a diameter of 3.5.
In inch optical discs, a magneto-optical type, a read-only ROM type, and a partial ROM type in which magneto-optical and ROM are mixed are standardized by the ISO standard, and are expected to be further widely spread in the future. .

Recently, information recording carriers such as optical discs, optical cards, magnetic discs, magnetic cards, and magnetic tapes are also applied in the field of digital audio.
For example, a player using a write-once type optical disk or a magneto-optical disk as a master source in 24-48 digital multi-track recording is sold.

In addition to such products for professionals, CD-Rs (light once type compact discs) and MDs (mini discs) have also appeared as products for general consumers, and attention is paid to future trends. There is. A number of tracks are formed on these information record carriers, and information is recorded by the presence or absence of marks along the tracks. RO
Taking an M type optical disc as an example, as shown in FIG. 5, a row of marks (3) is formed along the center (2) of the track (1). This mark (3) is a depression having a certain phase depth and is called a pit. Information is reproduced depending on the presence or absence of pits. In the simplest example, a pit is 1, a part without a pit is 0, and binary recording is performed by the 1,0.

[0005]

In order to further increase the data density of such a conventional information record carrier, it is currently researched to narrow the track pitch (the interval from the track center to the adjacent track center). ing. However, for example, in the case of an optical disc, the wavelength is 780-83.
0 nm semiconductor laser and numerical aperture (NA) 0.5
In a conventional pickup equipped with a 0.55 objective lens, the influence of information written in adjacent tracks (called crosstalk) becomes extremely large when the track pitch is smaller than 1.4 μm. In addition, since the tracking error signal necessary for tracking becomes extremely small, it is difficult to perform accurate tracking. To solve this problem, the wavelength 67
Semiconductor lasers of 0 to 690 nm have been developed,
The shape and output of laser light is still inadequate.

In addition, in the case of the conventional information record carrier, in principle, 2
Value recording is the limit, and so high data density cannot be achieved by so-called multi-value recording of three or more values. 2 more binary information
It was also impossible to achieve high data density by so-called multiplex recording in which recording is performed in double and triple layers. Therefore, the present invention solves the above-mentioned drawbacks of the prior art, enables multi-valued recording and multiple recording on an information record carrier, and is a new information recording that can realize high data density and high data transfer rate. The purpose is to provide a carrier.

[0007]

In order to solve the above problems, the present invention provides an information record carrier having marks formed along a track, in which information is recorded by a combination of a mark start end and a mark end. There is provided an information record carrier characterized by being recorded. Further, in the present invention, the combination of the mark start end and the mark end is a combination of the mark start end shape and the mark end end shape, or the position with respect to the track center of the mark start end and the track end point of the mark. With the position of the mark, the one using the optical property at the mark start and end, the one using the magneto-optical property at the mark start and end, and the combination of the position of the mark start and end. It is also one aspect.

[0008]

The information record carrier of the present invention is characterized in that information is recorded by the combination of the start end of the mark and the end end of the mark. That is, assuming that the positions of the start end and the end of the mark with respect to the track center take a total of M positions, there are M × M = M ² combinations of the start end position and the end position. Therefore, M ² value recording is possible. further,
If M ² ≧ 2 ^L , double L double recording is possible. Further, when the mark is a pit and the pit depth is K types, there are M ² × K = M ² K combinations of the start end position and the end position, and the M ² K value can be recorded. If M ² K ≧ 2 ^L , binary L double recording is possible. The above information can be reproduced by detecting the reflected light intensity when the laser light is focused on the mark, for example. Thus, according to the present invention, multi-valued recording and multiple recording are possible, and high data density and high data transfer rate are realized.

The principle of the present invention will be described below with reference to the drawings. That is, first, the information record carrier according to the present invention is different from the conventional information record carrier in which information is recorded depending on the presence or absence of a mark, in that information is recorded by a combination of a mark start end and a mark end. . As a result, the information record carrier according to the present invention can realize high data density by multi-value recording or multiple recording.

A method of recording information by combining a mark start end and a mark end will be described. For example, it is assumed that the mark start end and the mark end can have N types of shapes. At this time, there are N × N = N ² combinations of the mark start edge shape and the mark end edge shape. Therefore, if this number of combinations is associated with information, multi-value recording of N ² values becomes possible. Further, if N ² ≧ 2 ⁿ , ^n- ary binary multiplex recording becomes possible. FIG. 1 shows an example of the starting and ending shapes of such a mark.

The mark (3) arranged at the center (2) of the track (1) can have various shapes of the starting end (4) and the terminating end (5). Is not only the shape of the start end (4) and the end (5) of the mark (3) shown in FIG. 1, but also the optical properties such as reflectance, transmittance and phase difference at the mark start end (4) and end (5). The properties may be used, or the magnetic properties such as the direction of magnetization and coercive force, and the magneto-optical properties such as Kerr rotation angle and Kerr ellipticity may be used. Further, it may be the positions of the start and end of the mark.

An example in which information is multi-valued and multiplexed according to the positions of the start (4) and end (5) of the mark with respect to the track center (2) will be described below. Now, assuming that the positions of the start and end of the mark with respect to the track center take a total of M positions, there are M × M = M ² combinations of the start and end positions. Therefore, M ² value recording is possible. Furthermore, if M ² ≧ 2 ^L , double L double recording is possible.

Further, the mark is a pit and the pit depth is K.
As for types, M ² × K = M ² K combinations are possible, so that M ² K value recording is possible. Also M ² K ≧ 2
^{If L} , binary L double recording is possible. M = 3, K = 2
An example of is shown below. As shown in FIG. 2, the positions of the start and end of the mark with respect to the track center (2) are as follows.
It is assumed that there are a total of three positions of the track center (2) position, the right side (6) position with respect to the track center, and the left side (7) position with respect to the track center. There are 3 × 3 = 9 combinations of starting and ending positions. Therefore, 9-value recording is possible. Also, since 9 ≧ 2 ^3, binary triple recording is possible. Furthermore, if the mark is a pit and the pit depth is two types, there are 9 × 2 = 18 combinations, so 18
Value recording becomes possible. Also, since 18 ≧ 2 ^4, binary quadruple recording is possible.

The above information can be reproduced by, for example, detecting the reflected light intensity when the laser light is focused on the mark. The detection of the beginning and end of the mark is performed by the photodetector signal (when the photodetector is a multi-division sensor, the sum of the signals of the divided photodetection units, that is, the total signal) increasing or decreasing, that is, the differential signal. This can be done by detecting the point where is a positive or negative extreme value.

The detection of the shape, position, optical property, magnetic property, magneto-optical property, etc. of the start end and end of the mark can be distinguished by, for example, the difference in the amount of light received by the photodetector, that is, the difference in signal level. Particularly, in the case of the shape of the start end and the end of the mark, the photodetector may be divided into, for example, two parts before and after the track, and the two photodetection parts can be distinguished by the difference signal level. Further, in the case of the positions of the start end and the end of the mark, the photodetector may be divided into, for example, two parts on the left and right sides of the track, and can be distinguished by the difference signal level of the two divided photodetection parts.

When the marks are pits of several kinds of depths, the difference in the amount of light received by the photodetector, that is, the difference in signal level can be used to judge the difference in depth. In particular, when the pit depth is set to two types, for example, the incident laser light is linearly polarized light forming an angle of 45 ° with the track direction and the reflected light is 2
By splitting into a polarized light component in the direction parallel to the track and a polarized light component in the direction perpendicular to the track by the half-wave plate and the polarization beam splitter and detecting the light quantity with each photodetector, or two photodetectors The depth can also be discriminated by detecting the difference signal of. In this case, one of the pits has a depth at which diffraction efficiency is large for polarized light in the direction parallel to the track (about λ / 3n to λ / 4n, where λ is the wavelength of the reproduction light and n is the refractive index of the information recording carrier substrate). It is preferable that the other pit is selected to a depth (about λ / 4n to λ / 5n) having a large diffraction efficiency for polarized light in the direction perpendicular to the track.

An example of a method of detecting the positions of the start and end of the mark with respect to the track center will be described below. As shown in FIG. 2, the positions of the start and end points of the mark with respect to the track center are the track center (2) position, the right side (6) position with respect to the track center, and the left side (7) position with respect to the track center. Take a position. The photodetector is divided into two parts on the left and right sides of the track, and the light outputs from the two divided photodetection sections are I ₁ and I ₂ , respectively. At this time, the sum signal of the two split photodetection sections, that is, (I ₁ +
The point at which I ₂ ) increases or decreases, that is, (I ₁ + I ₂ ).
It is possible to detect the start end and the end of the mark from the point where the differential signal of is a positive or negative extreme value. Further, at that time, since the difference signal of the two divided photodetection sections, that is, (I ₁ −I ₂ ) becomes 0 or a positive value or a negative value, the positions of the start and end portions of the mark with respect to the track center are the track center positions. , The position on the right side of the center of the track and the position on the left side of the center of the track can be determined. Mark from the signals obtained by dividing the difference signal (I ₁ -I ₂₎ rather than the difference signal by the sum signal or _{(I 1 -I 2) / (} I 1 + I 2) is zero or a positive or negative value It is also possible to determine the positions of the start end portion and the end portion of the track relative to the track center. The differential signal d of the overall _{(I 1 + I 2) (} I 1
A product signal of + I ₂ ) / dt and the difference signal (I ₁ −I ₂ ) may be used.

FIG. 3 shows the sum signal (I ₁ + I ₂ ) and the derivative signal d (I of the sum signal when the marks shown in FIG. 2 are reproduced.
₁ shows an example of values to be associated with ₁ + I ₂ ) / dt and a difference signal (I ₁ -I ₂ ) in 9-value recording and an example of values to be associated in binary / triple recording. In order to distinguish two kinds of pit depth, for example, the incident laser light is set to 45 ° with respect to the track direction.
This is possible by detecting the reflected light as a linearly polarized light having an angle of 2 by dividing the reflected light into a polarized light component in the track direction and a polarized light component in the direction perpendicular to the track by a half-wave plate and a polarization beam splitter.

[0019]

【Example】

[Example of optical disc] Information recorded on the optical disc is 1
Eight-valued data was used. That is, these data were recorded as pits of 9 types as shown in FIG. 2 as 2 types of pit depths and 2 × 9 = 18 types of pits.

In this example, an optical disk was manufactured by the method described below. First, a synthetic quartz master having an outer diameter of 220 mm, an inner diameter of 10 mm, a plate thickness of 6 mm, and a surface roughness Ra10 or less is washed in a mixed solution of sulfuric acid and hydrogen peroxide solution at a liquid temperature of 60 ° C., and then washed with a weak alkaline detergent, Then, it was ultrasonically cleaned with ultrapure water and dried by a high speed spin drying method. Then, a primer (anchor coat manufactured by Transyl Co., Ltd.) was spin-coated on the surface of the master disk, and then a positive photoresist (AZ1350 manufactured by Hoechst) was spin-coated.

Then, data was recorded on the surface of the master by a laser cutting machine (wavelength 457.9 nm, NA 0.93). Nine kinds of pits are formed by adding a new EO deflector after the conventional EO modulator of the cutting machine optical system to wobble the signal-modulated laser light and center the laser light on the track. The position was set to the right side with respect to the track center, and the left side with respect to the track center. The pits having two kinds of depths were formed by modulating the laser power with an EO modulator.

The linear velocity during cutting is 1.4 m / s, the track pitch is 1.2 μm, the length of pits to be formed is about 0.8 μm, and the distance between pits is about 0.8.
The wobbling layer at the pit start and end is about 0.04 μm on both the right and left sides with respect to the track center.
After that, a phenomenon treatment was performed to form a pit pattern on the master surface.

After forming a nickel conductive layer having a film thickness of 500Å on the surface of the resist master pattern thus produced by sputtering, electroforming was performed in a nickel sulfamate bath to form a nickel plating layer having a thickness of 300 μm. After polishing the nickel-plated surface,
A stainless steel plate having an outer diameter of 180 mm, an inner diameter of 20 mm and a plate thickness of 10 mm was adhered to the nickel-plated surface with an epoxy adhesive. After the adhesive was hardened, the quartz plate and the nickel plating that had been bonded to the plate were peeled off, and the residual photoresist on the pattern surface was removed by oxygen ashing to produce a stamper. The pit depth of the stamper is 1000Å and 1300Å
And the pit width was about 0.3 to 0.4 μm.

From the stamper thus obtained, a pit pattern was duplicated on the surface of a glass substrate having an outer diameter of 120 mm, an inner diameter of 15 mm and a plate thickness of 1.2 mm by the so-called 2P method. Next, an aluminum layer was sputtered on the pattern replication surface, and an organic protective film was spin-coated to obtain an optical disc. The optical disk manufactured in this manner was reproduced by an evaluation drive. FIG. 4 shows an example of the pickup optical system of the evaluation drive.

A collimator lens (9), a beam shaping prism (10), a beam splitter (11) and an objective lens (12) are arranged in the optical path from the laser (8),
The information recording carrier (20) is illuminated with laser light. Further, the Hick-up optical system includes a condenser lens (13), a cylindrical lens (14), a tracking and focusing photodetector (15), a half-wave plate (16), a polarization beam splitter (17), and A split photodetector 1 (18) and a split photodetector 2 (19) are provided.

The wavelength of the laser (8) is 680 nm and the NA of the objective lens (12) is 0.55. The tracking is a push-pull method, and the focusing is an astigmatism method. The laser light incident on the optical disk is linearly polarized light that makes an angle of 45 ° with the track direction. The reflected light from the optical disc is divided into two by the half-wave plate (16) and the polarization beam splitter (17), and the photodetector 1 (18) and the photodetector 2 are divided into two in the horizontal direction of the track.
The light is received by (19). When the respective channel outputs of the photodetector 1 (18) are I ₁ and I ₂ and the respective channel outputs of the photodetector 2 (19) are I ₃ and I ₄ , the detection of the pit start end and the end and the pit start end The detection of the position of the pit end is [(I ₁ + I ₂ ) + (I ₃ + I ₄ )] × [(I ₁ −
Carried out by _{I 2) + (I 3 -I} 4)] signal, the detection of the depth of the pits is _{[(I 1 + I 2)} - can be carried out by (I ₃ + I _4)] signal. As a result of actually reproducing the optical disk, it was confirmed that the 18-value data could be discriminated without any problems.

[0027]

As described in detail above, according to the present invention, it is possible to perform multi-valued recording and multiple recording on an information record carrier by recording information by combining a mark start end and a mark end. Higher data density and higher data transfer rate can be realized.

[Brief description of drawings]

FIG. 1 is an enlarged plan view showing an example of a mark on an information record carrier of the present invention.

FIG. 2 is an enlarged plan view showing an example of a mark on the information record carrier of the present invention.

FIG. 3 is a time correlation diagram showing an example of a reproduction signal and data from the information recording carrier of the present invention.

FIG. 4 is an optical system 1 for reproducing the information record carrier of the present invention.
It is a block diagram showing an example.

FIG. 5 is an enlarged plan view showing a mark of a conventional information record carrier.

[Explanation of symbols]

 1 track 2 track center 3 mark 4 mark start end 5 mark end 6 right side to track center 7 left side to track center 8 laser 9 collimator lens 10 beam shaping prism 11 beam splitter 12 objective lens 13 condensing lens 14 cylindrical lens 15 Photodetector for tracking and focusing 16 Half-wave plate 17 Polarizing beam splitter 18 2-split photodetector 1 19 2-split photodetector 2 20 Information record carrier

Claims (9)

[Claims] 1. An information record carrier having marks formed along a track, wherein information is recorded by a combination of a mark start end and a mark end. 2. The information record carrier according to claim 1, wherein the shape of the beginning of the mark and the shape of the end of the mark are combined. 3. The information record carrier according to claim 1, wherein the position of the beginning of the mark with respect to the track center and the position of the end of the mark with respect to the track center are combined. 4. The mark has a phase structure.
Information record carrier. 5. The information record carrier according to claim 4, wherein the mark has a phase structure having two kinds of depths. 6. The information record carrier according to claim 1, wherein in the combination of the mark start end and the mark end end, the optical properties at the mark start end and the mark end are utilized. 7. The information record carrier according to claim 1, wherein the combination of the mark start end and the mark end uses the magneto-optical property at the mark start end and the mark end. 8. The information record carrier according to claim 1, wherein a magnetic property at a mark start portion and a mark end portion is utilized in a combination of the mark start end and the mark end. 9. The information record carrier according to claim 1, wherein the start position and the end position of the mark are combined.