JP2002260239A - Optical disk and optical original disk exposing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to accurately detect address information and read the address information formed in line in the direction of the radius even in an optical disk having a narrow track pitch. SOLUTION: In the optical disk in which discontinued groups are spirally formed, by forming a prepit as the address information at either land of the discontinued parts of the groups, the prepit is formed at either land of the discontinued parts of the groups provided in the optical disk, and thereby the accurate detection of the address information becomes possible even if the optical disk has the narrow track pitch with a small push-pull signal. For this optical disk, further, the length Lp of the prepit satisfies the expression λ/(2 n.NA)<=Lp<=2λ/(n.NA), thereby sets the length of the prepit to increase the output of an address signal but not to affect an RF signal. Therefore, the address information after recorded and the recorded information are certainly detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical disk on which information can be written and a method for manufacturing an optical disk master, and more particularly to a method for pre-formatting an optical disk.

[0002]

2. Description of the Related Art In a recordable optical disk, address information is recorded by wobbling a groove. For example, CD-RW
(Compact Disc-ReWritable)
The pre-format method used in the above-mentioned method is such that a signal whose groove is frequency-modulated is approximately 30 nm in a radial direction.
Wobble (meandering) by a very small amount, but since this wobble frequency is higher than the tracking frequency,
The pickup cannot follow the groove wobble. Therefore, a wobble signal remains in the push-pull (hereinafter, referred to as “PP”) signal, which is detected as address information.

In recent years, in order to increase the storage capacity of an optical disk, it is necessary to improve the recording density by reducing the track pitch.
However, when the track pitch is reduced, the amplitude of the PP signal is reduced, and the wobble signal is also reduced.
For this reason, there is a problem that it becomes difficult to detect the address signal from the reduced wobble signal.
Therefore, even in an optical disk having a narrow track pitch and a small PP signal, a preformat method capable of accurately detecting address information is required. On the other hand, as a method for increasing the recording capacity, an L / G (land / groove) recording method has been proposed. this is,
Conventionally, data recorded on only one of the groove and the land is recorded on both the groove and the land. If this method is realized by the above-described method of wobbling the groove, the address information of the two adjacent groove tracks is superimposed on the wobble signal of the land track, so that the address information of the land track cannot be obtained. There is a point.

For this reason, for example, Japanese Patent Application Laid-Open No. 09-0449
In the method disclosed in Japanese Patent Application Laid-Open No. 07-2007, address information is formed on an optical disk substrate as a wobble mark that can be shared by a land track and a groove track, and demodulation is performed by changing an RF signal or a TE signal. Also, the groove is moved radially in the radial direction by 1 /
By wobbling by two, an address signal larger than that of a system such as a CD-RW can be obtained. However, in this method, when grooves wobbled in the radial direction are formed side by side as shown in FIG. 2A, the groove 1 and the land 1 have symmetrical cross-sectional shapes in the radial direction. Even if the formed groove is formed, no address signal is generated. Therefore, in such an arrangement, there is a problem that address information cannot be detected.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve these problems, and an object of the present invention is to provide an optical disk and an optical disk master exposure apparatus which solve the following problems.

A first object of the present invention is to provide an optical disk capable of accurately obtaining address information even when a track pitch is narrow and a push-pull signal is small.

According to a second aspect of the present invention, in the optical disk according to the first or fourth aspect, the address information can be reproduced even when the address information is arranged to overlap in the radial direction. To provide an optical disk.

Problem 3 (corresponding to claim 3 and claim 6) The problem 3 is to correct the recorded information and the address information after the information recording in the optical disc according to claim 1, claim 2, claim 4, or claim 5. To provide an optical disc that can be reproduced.

A fourth object of the present invention is to provide an optical disc capable of improving the recording capacity even at the same track pitch.

A fifth object of the present invention is to provide an optical disk master exposure apparatus for manufacturing the optical disk master according to any one of the first to seventh aspects.

[0006]

[Measures taken to solve the problem]

According to a first aspect of the present invention, there is provided an optical disk in which a discontinuous groove is formed in a spiral shape, a pre-pit is formed as address information on one of lands in a discontinuous portion of the groove. It was done.

Since prepits are formed on one land of the discontinuous portion of the groove provided on the optical disc, even if the optical disc has a narrow track pitch with a small push-pull signal, the address information can be accurately detected. It becomes possible.

[0007]

Embodiment 1 (corresponding to claim 2) In Embodiment 1, the distance ap between the center of the prepit and the center of the groove is TP / 8 ≦ ap ≦ 3TP /
It is eight. Here, the TP is a track pitch.

Since the prepit is formed at a position deviated from the center of the land, the address information can be reliably detected even when the prepit is formed overlapping in the radial direction.

[0008]

Embodiment 2 (corresponding to claim 3) In Embodiment 2, the prepit length Lp is λ / (2n · NA) ≦ Lp ≦ 2λ, with respect to the optical disk of Solution 1 or Embodiment 1.
/ (N · NA). Here, λ is the wavelength of the recording / reproducing light, n is the refractive index of the optical disk substrate, and NA is
Is the numerical aperture of the objective lens of the recording / reproducing apparatus.

The length of the prepit is set within a range in which the output of the address signal becomes large and does not affect the RF signal, so that the recorded address information and the recorded information can be reliably detected.

[0009]

A second aspect of the present invention is an optical disc in which grooves are spirally formed, and the address information is recorded by offsetting the grooves to one of the lands. is there.

In the solution 2, since the address information is recorded with the groove offset to one land side, even in an optical disk with a small push-pull signal,
Address information can be accurately detected.

[0010]

Embodiment 1 (corresponding to claim 5) Embodiment 1 is the optical disk of Solution 2, wherein the offset amount ag is T
P / 8 ≦ ag ≦ 3TP / 8. However,
The above TP is a track pitch.

In the first embodiment, since the offset amount of the groove is set to not more than 1/2 of the land width, the address information can be reliably detected even when the address information is arranged in the radial direction.

[0011]

Second Embodiment (Corresponding to claim 6) In the optical disk according to the second means or the first embodiment, the length Lg of the offset groove is λ / (2n · NA) ≦ Lg ≦ 2 /
(N · NA). Here, λ is the wavelength of the recording / reproducing light, n is the refractive index of the optical disk substrate, and NA is the numerical aperture of the objective lens of the recording / reproducing apparatus.

In the optical disk according to the second embodiment, the length of the offset groove is set to a length that increases the output of the address signal and does not affect the RF signal.
The recorded address information and the recorded information can be accurately reproduced.

[0012]

A third aspect of the present invention is an optical disc according to any one of the first to the second aspects of the present invention and the optical disc according to any one of the embodiments. That is, address information is shared between the groove track and the land track.

In the optical disk of Solution 3, information is recorded on lands and grooves, so that the recording capacity of the optical disk can be increased without reducing the track pitch.

[0013]

According to a fourth aspect of the present invention, there is provided an optical disc master exposing apparatus for exposing grooves and prepits on an optical disc master, comprising: a light source for generating first and second laser beams; Optical means for converging the second laser beam at different positions on the master optical disc, laser beam control means for controlling ON and OFF of the first and second laser beams, and control for controlling the operation of the laser beam control means Means for exposing a groove when the first laser beam is turned on, and a second means for exposing the groove when the first laser beam is turned off.
Is turned on to control the operation of the laser beam control means so as to expose the pre-pits.

In the optical disk master exposure apparatus according to the fourth aspect of the present invention, the groove and the prepit are exposed using the respective laser beams, so that the optical disk master can be easily manufactured.

[0014]

According to a fifth aspect of the present invention, there is provided an optical disc master exposing apparatus for exposing groove and address information on an optical disc master, a light source for generating a laser beam, and a laser beam condensing on the optical disc master. An optical unit for controlling the turning on and off of the laser beam, a unit for displacing the laser beam in the radial direction of the master optical disc, and a control unit for controlling the operation of the laser beam controlling unit. The control means exposes the groove when the laser beam is turned on, and turns on the laser beam when exposing the address information.
In this state, the operation of the laser beam control means is controlled so as to be displaced by a predetermined amount in the radial direction of the laser beam.

According to the optical disk master exposure apparatus of the invention, since the groove and the address information can be exposed by one laser beam, the optical system and the control system of the exposure apparatus can be simplified.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment (corresponding to claims 1 to 3 and claim 7) of an optical disk according to the present invention will be described with reference to FIG. FIG. 1A is an enlarged plan view of the optical disk. The groove is formed at a track pitch TP, and the address information is recorded as prepits offset from the center of the groove by ap toward the land. Note that one of the grooves where the pre-pits exist is interrupted. FIG. 1 shows a state of the PP signal when the light spot reproduces the m-th groove G (m).
(A). When the light spot is at the center of the groove, no PP signal is generated. However, at the position where the pre-pit exists, the PP signal is generated because the cross-sectional shape in the radial direction is asymmetric with respect to the groove center. The signal generated by the pre-pit is detected as an address signal, and the amplitude of the address signal at this time depends on the offset amount ap. As is clear from FIG.
/ 8 to 3TP / 8, the maximum value of the PP signal PP
Since the amplitude of the address signal of PPmax / 2 to PPmax is obtained with respect to the maximum, the address signal can be reliably detected even on an optical disk having a narrow track pitch and a small PP signal.
Further, as shown in FIG. 2B, ap is set to TP / 8 to 3T.
By setting P / 8, even when prepits are formed side by side in the radial direction, the radial cross-sectional shape at point C or point D can be made asymmetric, and the generation of address signals can be ensured. Can be.

According to this configuration, when exposing the pre-pits, it is determined whether or not two or more pre-pits are arranged in the radial direction in exposing the optical disc master. If the pre-pits are arranged, the exposure position is shifted in the circumferential direction. Since complicated processing is not required, there is an advantage that the control device of the exposure apparatus is simplified. Further, even when the light spot reproduces the m-th land L (m), an address signal is generated by the pre-pit similarly to the groove, so that one piece of address information can be shared by the land and the groove.

Next, a second embodiment of the optical disc according to the present invention (corresponding to claims 4 to 7) will be described with reference to FIG. FIG. 3 is an enlarged plan view of the optical disk. Grooves are formed at the track pitch TP,
The address information is recorded with the groove offset from the land side by ag. Similarly to the optical disc in the first embodiment, at the position where the groove is offset, the cross section in the radial direction is asymmetric with respect to the center of the groove, and a PP signal is generated. Can be. The groove offset amount is the same as that in the first embodiment. By setting the offset amount ap to TP / 8 to 3TP / 8, even when prepits are formed in a line in the radial direction, the offset in the radial direction is increased. Can be configured to be asymmetrical, and the amplitude of the address signal of about PPmax / 2 to PPmax is obtained with respect to the maximum value PPmax of the PP signal. Also in the present embodiment, since the address information is generated not only in the groove but also in the land track, one piece of address information can be shared by the land and the groove. In the optical disk having this configuration, the address information can be recorded only by offsetting the groove in the radial direction, so that the configuration of the optical disk master exposure apparatus can be simplified, and there is an advantage that the adjustment of the exposure optical system is easy.

Next, a first optical disk master exposure apparatus according to the present invention will be described with reference to FIG. FIG. 5 is a block diagram of the optical disk master exposure apparatus of the present invention. The laser beam emitted from the laser tube passes through a stabilizer that stabilizes the laser power,
The beam is split into a first beam (laser beam) 2 and a second beam 2 a by a beam splitter 1. First beam 2
After passing through the first optical modulator 3 and the optical deflector 4, is expanded to a predetermined beam diameter by a beam expander (not shown),
The light passes through a deflecting beam splitter (PBS) 5 and enters an optical head 6, where it is focused on an optical disk master 7. On the other hand, another second beam 2a passes through the optical modulator 3a and
Are combined with the first beam 2 and enter the optical head 6.
The first light modulator 3 and the second modulator 3a set the intensity of the beam (laser beam) on the light-converging surface, and respond to a signal from an exposure apparatus control device (not shown).
The second beam 2a is turned on / off. The optical deflector 4 deflects the laser light according to a signal from the exposure apparatus control device. The exposure apparatus controller controls the first light modulator 3, the second light modulator 3a, and the light deflector 4,
The number of rotations of the turntable, focus control of the optical head 6, and the like are performed. When exposing the glass master 7 of the optical disc described in the first embodiment using this optical disc master exposure apparatus, the groove is formed by the first beam 2 and the second beam 2 is formed.
Expose the pre-pits with a. Optical disk glass master 7
The distance between the first beam 2 and the second beam 2a converged thereon is adjusted according to a desired ap value (for example, 0.20 μm). The signals shown in FIGS. 6A and 6B are input from the exposure apparatus control device to the drivers of the first light modulator 3 and the second light modulator 3a, respectively, so that the first beam 2 and the second beam 2a are formed. Exposure at the timing shown in FIG.
Grooves and pre-pits are formed as shown in FIG.

A second optical disk master exposure apparatus (corresponding to claim 9) according to the present invention has basically the same configuration as the above-described first master disk exposure apparatus. However, in the present master exposure apparatus, only one exposure light source is required, so that the beam splitter and the optical modulator 3 in the first master exposure apparatus are unnecessary. When exposing the optical disc described in the second embodiment using the master disc exposure apparatus, the optical path of the first beam 2 in FIG. 5 is used, and when the address information is recorded, the first beam 2 is used. The first beam 2 is deflected in the radial direction by using the optical deflector 4 while keeping the ON state. The pre-format signal shown in FIG. 7 is output from the exposure apparatus controller, and is input to the driver of the optical deflector 4 to deflect the first beam 2. By performing such exposure, a groove as shown in FIG. 3 can be formed.

[0020]

Example 1 A substrate made of a polycarbonate resin (refractive index: 1.59) having a diameter of 120 mm and a thickness of 0.6 mm was formed on a substrate having a width of 0.34 μm by using a first optical disk master exposure apparatus.
m, a groove having a depth of 40 nm and a track pitch of 0.74
The prepits were formed at a position offset by 0.20 μm from the center of the groove, and five types of experimental boards were prepared in which the length Lp of the prepits was changed. The arrangement of the prepits may be appropriately selected according to the type of the optical disc. In the present embodiment, the DVD-RW (Di
digital Versatile Disc-ReWr
Iter).

After a phase change recording layer, a reflective layer, and a protective layer are sequentially laminated on this substrate, another layer having a diameter of 120 mm and a thickness of 0.1 mm is formed.
A phase-change optical disk was manufactured by bonding to a 6 mm polycarbonate resin substrate. The address reading error rate and PI error (uncorrectable data error of the reproduced signal) of this optical disk were measured. Recording and reproduction of information are performed by an optical disk evaluation device DDU-100 manufactured by Pulstec Industrial Co., Ltd.
0 was used. The wavelength of the recording / reproducing light is 635 nm, and the NA of the objective lens is 0.60. To measure the address reading error rate and PI error, the company's Signal Ana
Lyzer was used. Table 1 shows the measurement results. When Lp was 0.2 μm, the address read error rate before recording was small, but the output of the address signal was small, so that the address read error rate after recording was large, which was not practical. Also, Lp
2 μm, the signal due to the pre-pits was superimposed on the reproduced signal, and the PI error was large and not practical. 0.3 ≦
When Lp ≦ 1.5 μm, the address read error rate before and after recording was small, and the PI error was small.

[0022]

EXAMPLE 2 A groove having a width of 0.34 μm and a depth of 40 nm was formed at a track pitch of 0.74 μm on a substrate made of polycarbonate resin having a diameter of 120 mm and a thickness of 0.6 mm by using a second optical disk master exposure apparatus. Then, five types of experimental panels were prepared in which the length Lg of the groove that was offset was changed. The arrangement of the address information and the configuration of the optical disk are the same as in the first embodiment. The address reading error rate and PI error of this optical disk were measured using the same evaluation device as in Example 1.

Table 2 shows the measurement results. When the length Lg of the offset groove is 0.20 μm, the address read error rate before recording is small, but the output of the address signal is small, so that the address read error rate after recording is large, which is not practical. Further, when the length Lg of the offset groove was 2 μm, the PI error was large and not practical.
When 0.3 ≦ Lg ≦ 1.5 μm, the address read error rate before and after recording was small, and the PI error was small.

[0024]

As described above, according to the present invention,
By forming a prepit on one of the lands of the discontinuous portion of the groove, an effect is obtained that the address information can be accurately detected even on an optical disk having a small PP signal, and the address information is offset by offsetting the groove to one of the lands. With the configuration for recording, it is possible to manufacture an optical disk using a master exposure apparatus with a simplified optical system (corresponding to claims 1 and 4).

Further, the distance between the center of the pre-pit and the center of the groove or the offset amount ap is set to TP / 8 ≦ a
By setting p ≦ 3TP / 8, a sufficient amplitude of the address signal is ensured, and even when the address information is recorded side by side in the radial direction, the address information can be reliably detected. (Corresponding to claim 5). Furthermore, the length of the pre-pit or the offset groove is
By setting the range from λ / (2n · NA) to 2λ / (n · NA), the output of the address signal can be reliably read and the range that does not affect the RF signal can be set ( Claims 3 and 6). Further, by sharing address information between the groove track and the land track, a higher storage capacity can be realized at the same track pitch (corresponding to claim 7).
Further, according to the optical disk master exposure apparatus of the present invention, since the grooves and the prepits are exposed by the respective laser beams, it is possible to easily manufacture the optical disk master. For example, since groove and address information can be exposed with one laser beam, the optical system and control system of the exposure apparatus can be simplified.

[Brief description of the drawings]

FIG. 1A is an enlarged plan view of an optical disk according to the present invention, and FIG.
FIG. 10 is an explanatory diagram showing a state of a PP signal when (m) is reproduced.

FIG. 2 (a) is an enlarged plan view of an optical disk in which prepits are formed side by side in the prior art, and FIG. 2 (b) is an enlarged plan view of a part in which prepits are formed side by side in the present invention.

FIG. 3 is an enlarged plan view of another optical disk according to the present invention.

FIG. 4 shows a center position of a light spot of a pickup and PP.
FIG. 4 is an explanatory diagram showing a relationship between signals.

FIG. 5 is an explanatory view showing a first optical disk master exposure apparatus according to the present invention.

FIG. 6 is an explanatory diagram showing control signals of the first optical disk master exposure apparatus according to the present invention.

FIG. 7 is an explanatory diagram showing control signals of the second optical disk master exposure apparatus according to the present invention.

[Explanation of symbols]

1: beam splitter 2: first laser beam 2a: second laser beam 3: first optical modulator 3a: second optical modulator 4: optical deflector 5: deflection beam splitter (PBS) 6: optical head 7: glass Master: ap: distance between the center of pre-pits and the center of groove (offset amount) TP: track pitch λ: wavelength of recording / reproducing light n: refractive index of optical disk substrate NA: numerical aperture of objective lens of recording / reproducing apparatus

Claims (9)

[Claims] 1. An optical disk having spirally discontinuous grooves formed thereon, wherein prepits are formed as address information on one of the lands in the discontinuous portions of the groove. 2. The optical disk according to claim 1, wherein the distance ap between the center of the prepit and the center of the groove is TP / 8 ≦
An optical disc, wherein ap ≦ 3TP / 8.
Here, TP = track pitch. 3. The optical disk according to claim 1, wherein the length Lp of the prepit is λ / (2n · NA) ≦ Lp.
≦ 2λ / (n · NA). Here, λ: the wavelength of the recording / reproducing light, n: the refractive index of the optical disk substrate, and NA: the numerical aperture of the objective lens of the recording / reproducing apparatus. 4. An optical disk in which grooves are spirally formed, wherein address information is recorded by offsetting the grooves to one of the lands. 5. An optical disk according to claim 4, wherein the offset amount ag satisfies TP / 8 ≦ ag ≦ 3TP / 8. Here, TP = track pitch. 6. The optical disk according to claim 4, wherein the length Lg of the offset groove is λ / (2n
An optical disc, wherein NA) ≦ Lg ≦ 2λ / (n · NA). Here, λ: the wavelength of the recording / reproducing light, n: the refractive index of the optical disk substrate, and NA: the numerical aperture of the objective lens of the recording / reproducing apparatus. 7. The optical disk according to claim 1, wherein the optical disk is an L / G recording type optical disk.
An optical disc characterized by sharing address information between a groove track and a land track. 8. An optical disk master exposing apparatus for exposing grooves and prepits on an optical disk master, wherein a light source for generating first and second laser beams and the first and second laser beams are located at different positions on the optical disk master. An optical unit for converging, a laser beam control unit for controlling ON and OFF of the first and second laser beams, and a control unit for controlling an operation of the laser beam control unit, the control unit comprising: When the first laser beam is turned on, the groove is exposed, and the first laser beam is turned off.
An optical disc master exposure apparatus, wherein the operation of the laser beam control means is controlled so that the second laser beam is turned on when the pre-pit is exposed. 9. An optical disk master exposure apparatus for exposing groove and address information on an optical disk master, a light source for generating a laser beam, an optical means for condensing the laser beam on the optical disk master, and turning on and off the laser beam.
Laser beam control means for controlling the laser beam to be turned off, means for displacing the laser beam in the radial direction of the optical disk master, and control means for controlling the operation of the laser beam control means, wherein the control means turns on the laser beam. When the groove is exposed and the address information is exposed, the operation of the laser beam control means is controlled so that the laser beam is turned on and displaced by a predetermined amount in the laser beam radial direction. Optical disk master exposure equipment.