JP2002109788A - Optical disk and optical disk device - Google Patents

Abstract

(57) Abstract: An object of the present invention is to provide an optical disc capable of sufficiently reproducing a reproduction signal at each reproduction wavelength even with laser light having different reproduction wavelengths. In order to achieve the above object, in an optical disc of the present invention, pits corresponding to information are formed on a substrate,
By irradiating the pits with laser light, a reproduced signal having a predetermined signal amplitude ratio or more can be obtained, and thus, in an optical disc capable of reproducing the information, the optical disc has a first wavelength of 395 nm. To 415 nm and a second wavelength longer than the first wavelength of 635 nm to 655 nm.
The shape of the pits that, when irradiating the laser light having the wavelength of each of the first and second wavelengths, provides a reproduction signal having a predetermined signal amplitude ratio or more in any one of the first wavelength and the second wavelength. Wherein the depth of the pit is 70 nm to 170 nm, and the ratio of the width of the pit opening to the width of the pit bottom is the width of the pit opening / the width of the pit bottom ≦ 0.4. It is characterized by being.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk and an optical disk device on which information is recorded at a high density by using pits or the like.

[0002]

2. Description of the Related Art A general technique for producing an original master of an optical disc and a technique for duplicating a disc are described in, for example, "Introduction to Video Discs and DADs: Soichi Iwamura," edited by Corona Publishing Co., Ltd., p. 151-196. In brief, an original master having a photoresist applied to a glass disk is exposed to laser light by an exposure device to expose the photoresist. Next, the exposed portion is removed by development processing to form pits or grooves. A stamper is manufactured from the master, and a disk is formed using the stamper. On this disc, a reflective film is formed for reproduction only, and a recording film is formed for recording / reproducing,
The optical disk is completed. DVD (Digital Versatile)
In the case of Disk), these two disks are pasted together to form one disk.

[0003] Next, a brief description will be given of pit production.
In the current DVD, the shortest pit length is 0.40 μm and the pit depth is a depth near λ / 4n (λ: reproduction wavelength, n: refractive index of the disk). This is because the degree of modulation of the reproduced signal is maximized. "Video Disc and DA
D Primer: Soichi Iwamura's editor "p. With reference to 22 ~
Since the interference effect of laser light is used, the phase of the reflected light from the pit periphery and the phase of the reflected light from the pit portion are 1/4 wavelength,
In other words, if the wavelength shifts by 往復 in the round trip, they cancel each other out, so that the interference effect is maximized. When the phase of the reflected light from the pit peripheral portion and the phase of the reflected light from the pit portion are shifted by 波長 wavelength, that is, one wavelength in the reciprocation, the signal is minimized only by strengthening by the interference effect.

When the depth d is calculated from nd = λ / 4, d = λ / 4n = 655/4 × 1.578 = 104 nm (provided that n = 1.578 and λ = 655 nm). This calculation is performed when the shape of the prepit is an ideal shape (rectangular shape). However, since it is actually a trapezoidal shape, it shifts to a side deeper than this depth. The pit depth of the current DVD is 100 to 130 nm.

Next, a blue-violet laser is considered as a next-generation disk laser. Consider the case where the laser is used to reproduce the DVD. The same calculation is performed for the depth at which the reproduced signal is maximized. When d is calculated from nd = λ / 4, d = λ / 4n = 405/4 × 1.623 = 62.
nm (when n = 1.623, λ = 405 nm). The depth of the DVD calculated previously is 100 to 130 nm, and this depth is twice as deep as the λ / 4n of the blue-violet laser (124
nm), and the degree of modulation is minimized, and there is a problem that it is difficult to reproduce the current DVD with a blue-violet laser in this state.

[0006]

At present, the depth of a pit of a DVD is approximately 100 to 130 nm, and even if this depth is to be reproduced by a blue-violet laser, this depth is substantially equal to the wavelength λ of the blue-violet laser. / 2n, and the degree of modulation is minimized, which makes it difficult to reproduce information.

The present invention has been made to solve the above problems, and has as its object to provide an optical disk and an optical disk apparatus capable of reproducing information even with a blue-violet laser.

[0008]

In order to achieve the above object, in an optical disk according to the present invention, a pit corresponding to information is formed on a substrate, and a predetermined signal is emitted by irradiating the pit with a laser beam. A reproduced signal having an amplitude ratio or more is obtained, and thus, in an optical disc capable of reproducing the information, the optical disc has a first wavelength of 395 nm.
When the laser beam having a wavelength of 635 nm to 655 nm as a second wavelength longer than the first wavelength and a wavelength of 635 nm to 655 nm is longer than the first wavelength, any one of the first wavelength and the second wavelength Also, the optical disk having the shape of the pit from which a reproduction signal of the predetermined signal amplitude ratio or more is obtained, wherein the pit shape has a depth of 70 nm
170170 nm, wherein the ratio of the width of the pit opening to the width of the pit bottom is pit opening width / pit bottom width ≦ 0.4.

In the optical disk apparatus of the present invention, a pit corresponding to information is formed on the optical disk, and a laser signal is irradiated on the pit to obtain a reproduced signal having a predetermined signal amplitude ratio or more. Accordingly, in the optical disk device capable of reproducing the information from the optical disk, the optical disk has a wavelength of 395 nm to 415 nm as the first wavelength and a wavelength of 635 nm to 655 nm as the second wavelength longer than the first wavelength. When irradiating the laser light having the following, each of the laser light of the first wavelength and the second wavelength has a shape of the pit from which a reproduction signal having a predetermined signal amplitude ratio or more can be obtained. An optical disc, wherein the depth of the pit is 70 nm to 170 nm, and the ratio of the width of the pit opening to the width of the bottom of the pit is the width of the pit opening / the bottom of the pit. The width ≦ 0.4, and
The information processing apparatus further comprises a reproducing unit for reproducing the information from the optical disc.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. (Pits of Optical Disc of the Present Invention) First, pits of the optical disc of the present invention will be described.

FIG. 1 shows the shape of the pit 100. Fig. 1 (a)
FIG. 1B is a view of the optical disk as viewed from above, and FIG.
FIG. 2A is a cross-sectional view in the thickness direction of the optical disk taken along line X in FIG.

In this embodiment, the width (width of the opening) of the pit 100 in the radial direction of the optical disk (perpendicular to the line X in the figure) is a, and the width of the bottom 120 (width of the bottom) of the pit 100 is b. . In FIG. 1B, since it is a cross-sectional view of the pit 100 along the line X, it is described as b / 2. The pit depth is d, the track pitch is Tp, and the length of the pit 100 in the circumferential direction of the optical disk is pl. After that, the simulation will be described. The dimensions of the pit 100 and the like are all based on this figure.

As shown in FIG. 1, the pit 100 has a trapezoidal cross section, the periphery 110 of the pit 100 has a downward slope, and the bottom 120 is substantially flat. (Optical Disk of the Present Invention) FIG. 2 is a diagram showing an outline of an optical disk.

FIGS. 2A and 2B show a double-sided optical disk 15.
FIG. 2 is a perspective view and a cross-sectional view of FIG. 0. Reflective films 153 and 154 made of aluminum or the like are attached to one surface of transparent substrates 151 and 152 having a pit and made of a light-transmitting resin such as polycarbonate or acrylic. ing. The transparent substrates 151, 1
The thickness of 52 is 0.6 mm. Then, the transparent substrates 151 and 152 are bonded to each other with the reflective films 153 and 154 facing each other by an adhesive layer 157 made of a thermosetting adhesive and having a thickness of several tens of μm. A hole 158 for clamping is formed in the center of the optical disk 150, and a clamping zone 159 is provided around the hole 158. In a read-only optical disk, information is formed as pits in an information recording area 162.

[0015] In both the read-only optical disk and the recordable / reproducible optical disk, a control track 161 composed of prepits is formed on the innermost circumference on at least one side. In the case of an optical disc that can be recorded and reproduced,
In the information recording area 162, address information and the like are formed in advance by pre-pits, and grooves or lands are formed in portions where information is recorded. In the control track, information on the optical disk, recording characteristics of the recording film, start and end positions of address information recording, and the like are recorded. Although the basic structure of the recorded contents does not change between the recordable / reproducible optical disk and the read-only optical disk, there are those that are recorded as information and those that are not. In the embodiment,
Although the example in which the control track 161 is formed on the innermost circumference is shown, the control track 161 may be formed on the outermost circumference on the outer circumference side of the information recording area 162, or either one may be used. (Simulation Result) Next, FIGS. 3 to 8 show reproduction simulation results showing the difference in the amplitude ratio between the red laser and the blue-violet laser. The reproduction simulation will be described with reference to FIG. First, the simulation was performed assuming an ideal system free from aberrations and noise. In the DVD Read-Only Disc standard, the maximum value of the signal amplitude from 0 level to 14T and the signal amplitude Peak
o The ratio of Peak (PP value) is described as 0.6 or more. Therefore, hereinafter, even when a blue-violet laser is used, the 8-16 modulation method used in DVDs using a red laser and the R
It is assumed that the LL (Run-Length Limited) (2,10) method is adopted. This method is an encoding method that converts 8 bits of original information into 16 bits and limits the continuous length of 0 to a range of 2 to 10. Although the 14T, which is a code that does not exist in this range, is used as the synchronization signal, the synchronization signal needs to be reliably obtained regardless of whether any of the red laser and the blue-violet laser is used, so that the 14T signal can be obtained. It was simulated whether or not. The light source wavelength is 405 nm as a blue-violet laser, and the light source wavelength is 650 nm as a red laser.
simulated at 395nm to 415n for blue-violet
For the m, red laser, almost the same results were obtained within the range of 635 nm to 655 nm.

In FIGS. 3 and 5 to 8, the vertical axis represents the signal amplitude ratio (reproduced signal (all signals) by the reflected light of the laser light from the reflection film 153 or 154 in the area where the pit 100 of the optical disc 150 is not formed. (Reflection) is 1 and 14T
Almost coincides with the maximum value of the signal amplitude. The ratio of the reproduced signal to this signal) is shown, and the horizontal axis represents the pit depth (d).

Table 1 shows parameters in the simulation in FIG.

[0018]

[Table 1]

In FIG. 3, the pit 100 has a pit width (opening) (width of pit opening): 0.40 μm,
(Bottom) (Width of bottom of pit): Fixed at 0.15 μm, and a simulation of changing the pit depth was performed. Red1 is simulated with the wavelength and NA of the laser mounted on the current DVD player and the like, and is indicated by a dotted line in the figure. From this figure, DVD
The depth satisfying the standard is about 75 nm to about 170 nm. Since the reduction in the signal amplitude ratio due to the red laser is small up to a depth of about 70 nm, it may be in the range of about 70 nm to about 170 nm. ☆ → In the simulation, it was not possible to read as 75nm or more, so I put a reason to insert 70nm in accordance with the claim. ← ☆ The simulation result with the same pit shape and only the reproduction wavelength was changed to Blue1. It is shown by solid lines. As can be seen from this figure, the depth of the pit is about 75 nm to about 170 nm or about 70 nm.
If it is about 170 nm, even if pits satisfying the DVD standard are formed by the wavelength and NA of the laser mounted on the current DVD player, etc., the player equipped with the blue-violet laser also satisfies the standard. It will be fully reproducible.

FIG. 4 shows the amplitude ratio (reproduced signal (total reflection) by the reflected light of the laser light from the reflection film 153 or 154 in the area where the pit 100 of the optical disk 150 is not formed) as 1 on the vertical axis, and 14T. Of the pit bottom width (b) is plotted on the horizontal axis, and the pit depth (d) is 13
This is a result of a simulation in the case of 0 nm (in FIG. 3, the pit depth at which the signal amplitude ratio is substantially the lowest). From this figure, it can be seen that the pit shape which satisfies the DVD standard and satisfies the standard even with a blue-violet laser mounted player has a bottom width of 0.16.
When the ratio between the opening a and the bottom b at this time is taken, the opening (width of the opening of the pit) a / the bottom (width of the bottom of the pit) b = 0.4.

Next, a simulation result in the case where pit opening width / pit bottom width> 0.4 is shown.

Table 2 shows parameters in the simulation in FIG.

[0023]

[Table 2]

In FIG. 5, a simulation was performed in which the pit shape was fixed at a pit width (opening): 0.40 μm and (bottom): 0.35 μm, and the pit depth was varied. R
ed1 is simulated with the wavelength and NA of the laser mounted on the current DVD player, etc.
This is indicated by a dotted line in the figure. From this figure, the depth satisfying the DVD standard is about 65 nm to 150 nm. A simulation result obtained by changing only the reproduction wavelength for the same pit shape is Blue1, which is indicated by a solid line in the figure. As can be seen from this figure, even if pits satisfying the DVD standard are formed at the wavelength and NA of the laser mounted on the current DVD player, the player equipped with the blue-violet laser cannot satisfy the standard. become.

Table 3 shows parameters in the simulation in FIG.

[0026]

[Table 3]

In FIG. 6, a simulation was performed in which the pit shape was fixed at pit width (opening): 0.40 μm and (bottom): 0.30 μm, and the pit depth was varied. R
ed1 is simulated with the wavelength and NA of the laser mounted on the current DVD player, etc.
This is indicated by a dotted line in the figure. From this figure, the depth satisfying the DVD standard is about 65 nm to 155 nm. A simulation result obtained by changing only the reproduction wavelength for the same pit shape is Blue1, which is indicated by a solid line in the figure. As can be seen from this figure, even if pits satisfying the DVD standard are formed at the wavelength and NA of the laser mounted on the current DVD player, the player equipped with the blue-violet laser cannot satisfy the standard. become.

Table 4 shows parameters in the simulation in FIG.

[0029]

[Table 4]

In FIG. 7, a simulation was performed in which the pit shape was fixed at pit width (opening): 0.40 μm and (bottom): 0.25 μm, and the pit depth was varied. R
ed1 is simulated with the wavelength and NA of the laser mounted on the current DVD player, etc.
This is indicated by a dotted line in the figure. From this figure, the depth satisfying the DVD standard is about 70 nm to 165 nm. A simulation result obtained by changing only the reproduction wavelength for the same pit shape is Blue1, which is indicated by a solid line in the figure. As can be seen from this figure, even if pits satisfying the DVD standard are formed at the wavelength and NA of the laser mounted on the current DVD player, the player equipped with the blue-violet laser cannot satisfy the standard. become.

Table 5 shows parameters in the simulation in FIG.

[0032]

[Table 5]

In FIG. 8, a simulation was performed in which the pit shape was fixed at pit width (opening): 0.40 μm and (bottom): 0.20 μm, and the pit depth was varied. R
ed1 is simulated with the wavelength and NA of the laser mounted on the current DVD player, etc.
This is indicated by a dotted line in the figure. From this figure, the depth satisfying the DVD standard is about 70 nm to about 175 nm.
A simulation result obtained by changing only the reproduction wavelength for the same pit shape is Blue1, which is indicated by a solid line in the figure. As can be seen from this figure, the DVD and the wavelength of the laser mounted on the current DVD player etc.
Even if pits satisfying the standard are formed, a player equipped with a blue-violet laser cannot satisfy the standard.

According to the results of FIGS. 3 to 8 described above, if the ratio of the opening a / bottom b is larger than 0.4 based on the ratio of the opening a having the pit width and the bottom b of the pit width, the current DVD player is used. D at the wavelength and NA of the laser mounted on
Even if pits satisfying the VD standard are formed, a player equipped with a blue-violet laser cannot satisfy the standard. However, by setting the ratio of the opening a / bottom b to 0.4 or less, it becomes possible for a player equipped with a blue-violet laser to satisfy the standard. This is because the optical disk utilizes the interference effect of the laser beam, and the phase of the reflected light from the pit peripheral portion (the portion other than the pit portion) and the phase of the reflected light from the pit portion are 1/4 wavelength, that is, 1/0 in the round trip. If the wavelengths deviate from each other, they cancel each other, so that the interference effect is maximized. When the phase of the reflected light from the pit peripheral portion and the phase of the reflected light from the pit portion are shifted by 波長 wavelength, that is, one wavelength in the reciprocation, the signal is minimized only by strengthening by the interference effect. This effect is large when the pit shape is rectangular, but the effect becomes weaker as the pit shape becomes trapezoidal. Therefore, the phase of the reflected light from the pit peripheral portion and the phase of the reflected light from the pit portion are reduced by 1 /.
Even if the wavelength is shifted by two wavelengths, that is, one wavelength in a round trip, the degree of modulation can be obtained. (Optical Disk Reproducing Apparatus) Next, an outline of a reproducing apparatus for reproducing the optical disk 150 of the present invention will be described with reference to FIG. As shown in FIG. 9, the optical disc reproducing apparatus includes:
Spindle motor 8, rotation detector 9, optical pickup 1
0, actuator 11, servo controller 12, system controller 13, playback speed controller 14, playback processor 1
5, an error detection unit 16, a buffer control unit 17, an interface (I / F) 18, and the like.

The spindle motor 8 includes a servo controller 12
Optical disk 150 based on the motor drive signal sent from
Is driven to rotate. The rotation detector 9 detects the rotation drive of the spindle motor 8 and transmits the rotation drive to the system controller 13 as a rotation detection signal.

The optical pickup 10 irradiates the optical disk 150 with a light beam for reproduction, detects the reflected light from the optical disk 150, and transmits it to the reproduction processing unit 15 as an RF (Radio Frequency) signal. Actuator 11
Drives the optical pickup 10 for focus drive and tracking drive based on the focus drive signal and the tracking drive signal transmitted from the servo control unit 12.

The optical pickup 10 has at least a built-in LD (semiconductor laser) and an objective lens (not shown). When a red laser is used as the LD, an LD with a light source wavelength of 650 nm and an objective lens NA of 0.60 is used. Use an objective lens.

When a blue-violet laser is used as the LD, an LD having a light source wavelength of 405 nm and an objective lens NA of 0.65 and an objective lens are used.

The reproduction processing unit 15 reproduces the data of the optical disk 150 reflected on the RF signal transmitted from the optical pickup 10 and transmits the data to the error detection unit 16. In addition, the reproduction processing unit 15 generates a focus error signal, a tracking error signal, and the like from the RF signal transmitted from the optical pickup 10, and transmits the focus error signal and the tracking error signal to the servo control unit 12. Further, the reproduction processing unit 15 transmits an RF signal, a focus error signal, and a tracking error signal to the system controller 13.

The error detecting section 16 detects an error contained in the data of the optical disk 150 transmitted from the reproduction processing section 15, and corrects the detected error to the extent possible. The data recorded on the optical disc is provided with an error correction code, and the error is corrected by the error correction code. However, there is a limit to the error correction capability of the error correction code, and if the data on the optical disk includes an error exceeding the limit of the error correction capability, the error cannot be corrected. The error detection unit 16 notifies the system controller 13 of a reading error when the error of the data on the optical disk 150 cannot be corrected.

The buffer control unit 17 includes an error detection unit 16
The data of the optical disk whose error has been corrected is buffered, and the buffered data of the optical disk 150 is output to the outside via the interface 18.

The system controller 13 controls the entire optical disk device. Further, the reproduction speed control unit 14 performs a reproduction speed of the optical disc (rotation of the disc) based on the RF signal, the focus error signal, the tracking error signal, the focus drive signal, the tracking drive signal, and the read error notification from the error detection unit 16. Is transmitted to the servo control unit 12 for controlling the reproduction speed control signal. The reproduction speed control of the reproduction speed control unit 14 controls the disk reproduction speed.

The servo controller 12 generates a motor drive signal based on the reproduction speed control signal, and controls the drive of the spindle motor based on the motor drive signal. Further, the servo control unit 12 generates a focus drive signal and a tracking drive signal based on the focus error signal and the tracking error signal, and controls the driving of the actuator using the focus drive signal and the tracking drive signal. As a result, a good focus state and tracking state are always obtained.

Although an example in which one LD and an objective lens are provided in the optical pickup 10 has been described, two LDs and an objective lens may be provided in the optical pickup 10 or two optical pickups 10 may be provided. Each of the optical pickups may be provided with an LD and an objective lens so as to share a configuration other than the optical pickup.

As described above, in the optical disk of the present invention,
In particular, an optical disk having a pit shape in which the opening a / bottom b is 0.4 or less is formed. By adopting such a shape, it is possible to satisfy a standard even with a drive device having an actual wavelength different from the actual one and to a level that does not cause a problem. Was.

The above-mentioned optical disk of the present invention is the same as a normal optical disk manufacturing method, but has a great difference.

In the optical disk of the present invention, a resist having a low gamma is used. As a result, a pit shape (a pit bottom width is narrow) corresponding to the profile (shape) of the exposure beam is formed. In the conventional resist, since the gamma of the resist is high, the resist responds to an exposure light beam of a predetermined power or more, and becomes substantially rectangular (the width of the pit opening and the width of the pit bottom are substantially the same).

By controlling the light beam for exposure using a resist having a low gamma, the ratio of the width of the pit opening to the width of the pit bottom is determined by the following formula: width of pit opening / width of pit bottom ≦ 0.4. The optical disk having the pits can be obtained.

[0049]

As described above, according to the present invention, an optical disk and an optical disk capable of reading information stably at a level that satisfies the standard even with actual drive devices having different wavelengths and has a sufficient level of problem. Equipment can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining the shape of a pit on an optical disc of the present invention.

FIG. 2 is a schematic diagram of an optical disk of the present invention.

FIG. 3 is a view showing a range of a pit shape of the optical disc of the present invention.

FIG. 4 is a diagram showing a range of a pit shape of the optical disc of the present invention.

FIG. 5 is a diagram showing a case where the optical disk of the present invention deviates from a pit shape.

FIG. 6 is a diagram showing a case where the optical disk of the present invention deviates from a pit shape.

FIG. 7 is a diagram showing a case where the optical disk of the present invention deviates from a pit shape.

FIG. 8 is a diagram showing a case where the optical disk of the present invention deviates from a pit shape.

FIG. 9 is a diagram showing a schematic structure of a reproducing apparatus for reproducing an optical disk of the present invention.

[Explanation of symbols]

 Reference Signs List 100 pits (pre-pits) 110 Periphery of pits 120 Pit bottom 150 Optical disk 151, 152 Transparent substrate 153, 154 Reflective film 157 Adhesive layer 158 Hole 159 Clamping zone 161 Control track 162 Information recording area 8 Spindle motor 9 Rotation detector 10 Light Pickup 11 Actuator 12 Servo control unit 13 System controller 14 Reproduction speed control unit 15 Reproduction processing unit 16 Error detection unit 17 Buffer control unit 18 Interface (I / F)

Claims (2)

[Claims] A pit corresponding to information is formed on a substrate,
By irradiating the pits with a laser beam, a reproduced signal having a predetermined signal amplitude ratio or more can be obtained, whereby an optical disk capable of reproducing the information has a first wavelength of 395 nm for the optical disk. To 415
63 as the wavelength of nm and the second wavelength longer than the first wavelength.
When irradiating the laser light having a wavelength of 5 nm to 655 nm, the laser light of any one of the first wavelength and the second wavelength can obtain a reproduction signal having a predetermined signal amplitude ratio or more. An optical disc having a pit shape, wherein a depth of the pit shape is 70 nm to 170 nm, and a ratio of a width of the pit opening to a width of the pit bottom is obtained by: pit opening width / pit bottom width. An optical disc characterized by a width ≦ 0.4. 2. A pit corresponding to information is formed on an optical disk, and a laser signal is applied to the pit to obtain a reproduced signal having a predetermined signal amplitude ratio or more. An optical disc apparatus capable of reproducing information from an optical disc, wherein the first wavelength of the optical disc is from 395 nm to 415 nm.
63 as the wavelength of nm and the second wavelength longer than the first wavelength.
When irradiating the laser light having a wavelength of 5 nm to 655 nm, the laser light of any one of the first wavelength and the second wavelength can obtain a reproduction signal having a predetermined signal amplitude ratio or more. An optical disc having a pit shape, wherein a depth of the pit shape is 70 nm to 170 nm, and a ratio of a width of the pit opening to a width of the pit bottom is obtained by: pit opening width / pit bottom width. An optical disc device, wherein a width is ≦ 0.4, and a reproducing unit for reproducing the information from the optical disc.