Title: Optical information recording medium, and method and apparatus for recording/reproducing information thereon
Abstract: The present invention relates to an optical information recording medium including a disk-shaped transparent substrate and a recording layer for recording, reproducing or erasing information by irradiation of laser light, the recording layer being formed over the substrate. The recording layer of the present invention includes information tracks including groove tracks and land tracks that are formed alternately in a radial direction of the disk. The information tracks comprise information recording regions and address regions interposed between the information recording regions, the information recording regions and the address regions being arranged along the tracking direction of the laser light. In the information recording regions, every second step in the radial direction of steps for dividing the groove tracks from the land tracks adjacent to the groove tracks is wobbled in the tracking direction, and in a range whose ends are defined by the address regions the every second step is wobbled at a constant frequency. Prepit addresses for providing information on a position on the recording medium are formed on the address regions. Moreover, the present invention provides an optical information recording medium including n recording layers (where n is an integer of at least 2), and in at least the first recording layer to the (n-;1)th recording layer from the transparent substrate side, no pair of adjacent address regions in the radial direction of the disk are arranged so as to be aligned on a straight line passing through the center of the disk.
Patent Number: 6,922,387 Issued on 07/26/2005 to Akiyama, et al.
| Inventors:
|
Akiyama; Tetsuya (Osaka, JP);
Nishiuchi; Kenichi (Osaka, JP);
Narumi; Kenji (Osaka, JP)
|
| Assignee:
|
Matsushita Electric Industrial Co., Ltd. (Osaka, JP)
|
| Appl. No.:
|
600090 |
| Filed:
|
June 20, 2003 |
Foreign Application Priority Data
| Mar 24, 2000[JP] | 2000-084282 |
| Aug 01, 2000[JP] | 2000-232632 |
| Current U.S. Class: |
369/124.12; 369/44.41; 369/44.29 |
| Intern'l Class: |
G11B 007/00 |
| Field of Search: |
369/4441,444.2,442.8,442.9,443.4,443.6,124.12
|
References Cited [Referenced By]
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| 5452284 | Sep., 1995 | Miyagawa et al.
| |
| 5616390 | Apr., 1997 | Miyagawa et al.
| |
| 5726969 | Mar., 1998 | Moriya et al.
| |
| 5818812 | Oct., 1998 | Moribe et al.
| |
| 5852599 | Dec., 1998 | Fuji.
| |
| 5883958 | Mar., 1999 | Ishiguro et al.
| |
| 5936933 | Aug., 1999 | Miyamoto et al.
| |
| 6002655 | Dec., 1999 | Ono et al.
| |
| 6370091 | Apr., 2002 | Kuroda.
| |
| Foreign Patent Documents |
| 0 549 488 | Jun., 1993 | EP.
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| 0 715 301 | Jun., 1996 | EP.
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| 0 756 279 | Jan., 1997 | EP.
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| 0 802 527 | Oct., 1997 | EP.
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| 1 152 402 | Nov., 2001 | EP.
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| 2-301020 | Dec., 1990 | JP.
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| 3-219440 | Sep., 1991 | JP.
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| 5-314538 | Nov., 1993 | JP.
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| 6-176404 | Jun., 1994 | JP.
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| 6-309673 | Nov., 1994 | JP.
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| 6-338066 | Dec., 1994 | JP.
| |
| 9-73666 | Mar., 1997 | JP.
| |
| 9-91781 | Apr., 1997 | JP.
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| 9-97216 | Apr., 1997 | JP.
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| 9-120584 | May., 1997 | JP.
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| 9-259438 | Oct., 1997 | JP.
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| 9-265633 | Oct., 1997 | JP.
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| 9-306144 | Nov., 1997 | JP.
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| 10-65662 | Mar., 1998 | JP.
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| 10-83567 | Mar., 1998 | JP.
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| 10-188280 | Jul., 1998 | JP.
| |
| 98/58368 | Dec., 1998 | WO.
| |
| 01/6502 | Jan., 2001 | WO.
| |
Other References
Chinichi Tanaka, et al.; "Additional Information Recording Method on DVD-ROM
Disck: BCA (Burst Cutting Area)" Technical Research Report of the Institute of
Electronics, Information and Communication Engineers,, MR97-33; Oct. 1997; pp.
33-38. (Partial English Translation).
|
Primary Examiner: Hindi; Nabil
Attorney, Agent or Firm: Merchant & Gould P.C.
Parent Case Text
This application is a divisional of U.S. application Ser. No. 09/812,533 filed
Mar. 20, 2001, now U.S. Pat. No. 6,754,143.
Claims
1. A recording/reproducing method for an optical information recording medium
for recording, reproducing or erasing information by irradiating an optical information
recording medium with laser light,
the optical information recording medium comprising a disk-shaped transparent
substrate and a recording layer for recording, reproducing or erasing information
by irradiation of laser light, the recording layer being formed over the substrate,
wherein
the recording layer comprises information tracks,
the information tracks comprise information recording regions and address regions
interposed between the information recording regions, the information recording
regions and the address regions being arranged along the tracking direction of
the laser light,
prepit addresses for providing information on a position on the recording medium
are formed on the address regions, and
no pair of adjacent address regions in the radial direction of the disk are arranged
so as to be aligned on a straight line passing through a center of the disk,
the method comprising:
detecting reflected light obtained by irradiating the recording medium with the
laser light by a photodetector including two light-receiving portions divided in
a direction corresponding to a tracking direction of the laser light;
generating a sum signal and a difference signal of electrical signals output
from the two light-receiving portions;
generating a corrected sum signal obtained by correcting an amplitude variation
of the sum signal with the difference signal; and
generating data information from the corrected sum signal, thereby reproducing
the information.
2. The recording/reproducing method of claim 1, wherein the optical information
recording medium is an optical information recording medium comprising a disk-shaped
transparent substrate and n recording layers (where n is an integer of at least
2) for recording reproducing or erasing information by irradiation of laser light,
the recording layers being formed over the substrate, wherein
the recording layers comprise information tracks,
the information tracks comprise information recording regions and address regions
interposed between the information recording regions, the information recording
regions and the address regions being arranged alone a tracking direction of the
laser light,
prepit addresses for providing information on a position on the recording medium
are formed on the address regions, and
in at least the first recording layer to the (n-;1)th recording layer from the
transparent substrate side, no pair of adjacent address regions in the radial direction
of the disk are arranged so as to be aligned on a straight line passing through
a center of the disk.
3. A recording/reproducing method for an optical information recording medium
for recording, reproducing or erasing information by irradiating an optical information
recording medium with laser light,
the optical information recording medium comprising a disk-shaped transparent
substrate and a recording layer for recording, reproducing or erasing information
by irradiation of laser light, the recording layer being formed over the substrate,
wherein
the recording layer comprises information tracks including groove tracks and
land tracks that are formed alternately in a radial direction of the disk,
the information tracks comprise information recording regions and address regions
interposed between the information recording regions, the information recording
regions and the address regions being arranged along the tracking direction of
the laser light,
prepit addresses for providing information on a position on the recording medium
are formed on the address regions,
a pair of adjacent information tracks in the radial direction of the disk have
a common address region on which a common prepit address is formed, and
no pair of adjacent common address regions in the radial direction are arranged
so as to be aligned on a straight line passing through the center of the disk,
the method comprising:
detecting reflected light obtained by irradiating the recording medium with the
laser light by a photodetector including two light-receiving portions divided in
a direction corresponding to a tracking direction of the laser light;
generating a sum signal and a difference signal of electrical signals output
from the two light-receiving portions;
generating a corrected sum signal obtained by correcting an amplitude variation
of the sum signal with the difference signal; and
generating data information from the corrected sum signal, thereby reproducing
the information.
4. The recording/reproducing method of claim 3, wherein the optical information
recording medium is an optical information recording medium comprising a disk-shaped
transparent substrate and n recording layers (where n is an integer of at least
2) for recording, reproducing or erasing information by irradiation of laser light
the recording layers being formed over the substrate, wherein
the recording layers comprise information tracks including groove tracks and
land tracks that are formed alternately in a radial direction of the disk,
the information tracks comprise information recording regions and address regions
interposed between the information recording regions, the information recording
regions and the address regions being arranged along the tracking direction of
the laser light,
prepit addresses for providing information on a position on the recording medium
are formed on the address regions,
a pair of adjacent information tracks in the radial direction of the disk have
a common address region on which a common prepit address is formed, and
in at least the first recording layer to the (n-;1)th recording layer from the
transparent substrate side, no pair of adjacent common address regions in the radial
direction are arranged so as to be aligned on a straight line passing through the
center of the disk.
5. A recording/reproducing apparatus for an optical information recording medium
for recording, reproducing or erasing information by irradiating an optical information
recording medium with laser light,
the optical information recording medium comprising a disk-shaped transparent
substrate and a recording layer for recording, reproducing or erasing information
by irradiation of laser light, the recording layer being formed over the substrate,
wherein
the recording layer comprises information tracks including groove tracks and
land tracks that are formed alternately in a radial direction of the disk,
the information tracks comprise information recording regions and address regions
interposed between the information recording regions, the information recording
regions and the address regions being arranged along the tracking direction of
the laser light,
prepit addresses for providing information on a position on the recording medium
are formed on the address regions,
a pair of adjacent information tracks in the radial direction of the disk have
a common address region on which a common prepit address is formed, and
no pair of adjacent common address regions in the radial direction are arranged
so as to be aligned on a straight line passing through the center of the disk,
the apparatus comprising:
an optical head for outputting electrical signals based on reflected light obtained
by irradiating the recording medium with the laser light, the optical head including
a photodetector including two light-receiving portions divided in a direction corresponding
to a tracking direction of the laser light;
an addition amplifier for generating a sum signal of electrical signals output
from the two light-receiving portions;
a differential amplifier for generating a difference signal of electrical signals
output from the two light-receiving portions;
a waveform correcting circuit for generating a corrected sum signal obtained
by correcting an amplitude variation of the sum signal with the difference signal;
and
a data demodulating circuit for reproducing the information by generating data
information from the corrected sum signal.
6. The recording/reproducing apparatus of claim 5, wherein a control band of
the data demodulating circuit includes a frequency of wobbling of the information
tracks of the optical information recording medium containing information to be
recorded, reproduced or erased by the recording/reproducing apparatus.
7. The recording/reproducing method of claim 5, wherein the optical information
recording medium is an optical information recording medium comprising a disk-shaped
transparent substrate and n recording layers (where n is an integer of at least
2) for recording reproducing or erasing information by irradiation of laser light,
the recording layers being formed over the substrate, wherein
the recording layers comprise information tracks including groove tracks and
land tracks that are formed alternately in a radial direction of the disk,
the information tracks comprise information recording regions and address regions
interposed between the information recording regions, the information recording
regions and the address regions being arranged along the tracking direction of
the laser light,
prepit addresses for providing information on a position on the recording medium
are formed on the address regions,
a pair of adjacent information tracks in the radial direction of the disk have
a common address region on which a common prepit address is formed, and
in at least the first recording layer to the (n-
1)th recording layer from
the transparent substrate side, no pair of adjacent common address regions in the
radial direction are arranged so as to be aligned on a straight line passing through
the center of the disk.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical information recording medium for
recording/reproducing information by irradiation of laser light, and further relates
to a method and an apparatus for recording/reproducing information on this medium.
2. Description of the Prior Art
Optical information media have been noted widely as a large capacity and
high density memory, and erasable media that can be rewritten have been under development
at present. In one of the erasable optical information recording media, a recording
layer made of a phase change material that changes between an amorphous state and
a crystalline state is formed on a substrate, and information is recorded and erased
by irradiating the recording layer with laser light.
An alloy film comprising Ge, Sb, Te, or In as the main components such as a GeSbTe
alloy is known as a phase change material for the recording layer. Information
is recorded by making the recording layer partially amorphous to form recording
marks. The recording layer is made amorphous by heating the recording layer to
the melting point or more and cooling it. The recording layer is made crystalline
by heating the recording layer to the crystallization temperature or more and not
more than the melting point. The reflectance and the transmittance of the irradiated
laser light in a region in which a recording mark is formed are different from
those in other regions.
In general, spiral or concentric circular guide grooves that are tracked by laser
light for recording/reproducing information previously are provided on a substrate.
Regions between the grooves are called lands. In recordable CDs (CD-R) or minidisks
(MD), either grooves or lands are used as information tracks to record information
on, and the other is used as a guard band for separating adjacent information tracks.
In recent years, with improvement of the processing ability of various information
equipment, the amount of information to be handled has increased. For this reason,
there is a great demand for recording media with a larger capacity than ever. As
one approach to achieve larger capacity, in DVD-RAMs or the like, a method for
increasing track density by recording information on both grooves and lands is
adopted (land & groove recording method).
In DVD-RAMs, a format structure called a ZCLV (Zoned Constant Liner Velocity)
method is adopted. In this format structure, an information track is segmented
into a large number of information recording regions (sectors) by addresses indicating
the position on the medium. Further, several information recording regions are
grouped in the radial direction to form a zone. The number of sectors corresponding
to one rotation and the rotation speed are increased step by step by each zone
from the inner circumference to the outer circumference. In each zone, the rotation
speed is constant, and the linear velocity and the duration of a sector are substantially
constant between the zones.
On the other hand, in CD-Rs or MDs, a CLV (Constant Liner Velocity) method is
used in which information is recorded/reproduced at a constant linear velocity
throughout the recording regions. This method can achieve the maximum recording
density, and has an advantage in that the design of the recording layer is easy
because the thermal conditions during recording are constant.
In the CLV method, it is necessary to change the rotation speed frequently for
random access. For this change, the grooves are wobbled in the radial direction
at a constant spatial frequency, and a rotating motor of a recording/reproducing
apparatus is controlled based on signals obtained from these wobbles for recording/reproducing
information. However, the length of a groove for one rotation is varied with the
position in the radial direction, so that a phase difference occurs between the
wobbles in the adjacent grooves. Therefore, when the land & groove recording method
is used with the CLV method, signals are synthesized from wobbles having different
phases in the land portion. Thus, good circuit control signals cannot be obtained.
In order to solve this problem, JP 6-338066 has proposed a recording medium in
which only one edge of a groove is wobbled. In this recording medium, address information
is recorded as a signal that has been frequency-modulated, using a rotation control
signal as the carrier frequency.
However, when a gap between information tracks (track pitch) is narrowed
to achieve higher density, the ratio of the variation of the information track
width is increased, if the amplitude of the wobble is unchanged. Therefore, the
signal amplitude is varied during reproduction of information, so that signal quality
is deteriorated. On the other hand, when the amplitude of the wobble is reduced
as well, the intensity of the signal obtained from the wobble is reduced, which
makes it difficult to detect address information.
Furthermore, as another approach to achieve higher density information
recording, multilayered recording media including at least two recording layers
are proposed. In many multilayered recording media, it is necessary to record/reproduce
information with laser light that has passed through another recording layer. Furthermore,
it may be necessary to record information successively on a plurality of recording
layers, or reproduce information continuously from a plurality of recording layers.
SUMMARY OF THE INVENTION
Therefore, with the foregoing in mind, it is an object of the present
invention to provide an optical information recording medium with a large capacity
that can achieve easy and reliable recording/reproduction of information. More
specifically, first, it is an object of the present invention to provide an optical
information recording medium that can achieve easy detection of address information
while using the land & groove recording method and the CLV method. Secondly, it
is another object of the present invention to provide an optical information recording
medium that allows stable recording/reproduction of information even when the recording
medium includes two or more recording layers, and information is recorded/reproduced
on/from a recording layer with laser light that has passed through another recording
layer. Thirdly, it is another object of the present invention to provide an optical
information recording medium that can achieve efficient and reliable recording/reproduction
of information even when information is recorded/reproduced successively and continuously
on/from a plurality of recording layers.
A first optical information recording medium of the present invention includes
a disk-shaped transparent substrate and a recording layer for recording, reproducing
or erasing information by irradiation of laser light. The recording layer is formed
over the substrate, wherein the recording layer comprises information tracks including
groove tracks and land tracks that are formed alternately in a radial direction
of the disk. The information tracks comprise information recording regions and
address regions interposed between the information recording regions. The information
recording regions and the address regions are arranged along the tracking direction
of the laser light. In the information recording regions, every second step in
the radial direction of steps for dividing the groove tracks from the land tracks
adjacent to the groove tracks is wobbled in the tracking direction, and in a range
whose ends are defined by the address regions the every second step is wobbled
at a constant frequency, and prepit addresses for providing information on a position
on the recording medium are formed in the address regions.
The first recording medium of the present invention makes it possible to detect
the address information reliably when the CLV method is used together with the
land & groove method, so that the present invention allows stable recording/reproduction
of information.
The present invention also provides a method for recording/reproducing information
on the first optical information recording. In this method, information is recorded,
reproduced or erased at a constant linear velocity in all the information recording
regions while controlling a rotation speed of the recording medium with a rotation
control signal obtained from the wobbled steps.
One embodiment of a second optical information recording medium of the present
invention includes n recording layers (where n is an integer of at least 2), wherein
the recording layers comprise information tracks. The information tracks comprise
information recording regions and address regions interposed between the information
recording regions. The information recording regions and the address regions are
arranged along the tracking direction of the laser light. Prepit addresses for
providing information on a position on the recording medium are formed on the address
regions, and in at least the first recording layer to the (n-;1)th recording layer
from the transparent substrate side, no pair of adjacent address regions in the
radial direction of the disk are arranged so as to be aligned on a straight line
passing through the center of the disk.
Another embodiment of the second optical information recording medium includes
a disk-shaped transparent substrate and n recording layers (where n is an integer
of at least 2) for recording, reproducing or erasing information by irradiation
of laser light. The recording layer is formed over the substrate, wherein the recording
layers comprise information tracks including groove tracks and land tracks that
are formed alternately in a radial direction of the disk. The information tracks
comprise information recording regions and address regions interposed between the
information recording regions. The information recording regions and the address
regions are arranged along the tracking direction of the laser light. Prepit addresses
for providing information on a position on the recording medium are formed on the
address regions. A pair of adjacent information tracks in the radial direction
of the disk have a common address region on which a common prepit address is formed,
and in at least the first recording layer to the (n-;1)th recording layer from
the transparent substrate side, no pair of adjacent common address regions in the
radial direction are arranged so as to be aligned on a straight line passing through
the center of the disk.
The second recording medium allows stable recording/reproduction of information,
even when information is recorded/reproduced with laser light that has passed through
another recording layer. In this medium, even if the transmittance of the laser
light is different between the information recording regions and the address regions,
the address regions do not form a block but are dispersed. Therefore, transmitted
laser light hardly affects the recording layer. The difference in the transmittance
of the laser light is made typically by formation of recording marks on the information
recording regions.
The present invention also provides a method and an apparatus for recording/reproducing
information suitable for the second optical information recording medium. This
method is a recording/reproducing method for an optical information recording medium
for recording, reproducing or erasing information by irradiating an optical information
recording medium with laser light, including detecting reflected light obtained
by irradiating the recording medium with the laser light by a photodetector including
two light-receiving portions divided in a direction corresponding to a tracking
direction of the laser light; generating a sum signal and a difference signal of
electrical 1 signals output from the two light-receiving portions; generating
a corrected sum signal obtained by correcting an amplitude variation of the sum
signal with the difference signal; and generating data information from the corrected
sum signal, thereby reproducing the information.
Furthermore, this apparatus is a recording/reproducing apparatus for
an optical information recording medium for recording, reproducing or erasing information
by irradiating an optical information recording medium with laser light, including
an optical head for outputting reproduction signals of the information based on
reflected light obtained by irradiating the recording medium with the laser light.
The optical head includes a photodetector including two light-receiving portions
divided in a direction corresponding to a tracking direction of the laser light;
an addition amplifier for generating a sum signal of electrical signals output
from the two light-receiving portions; a differential amplifier for generating
a difference signal of electrical signals output from the two light-receiving portions;
a waveform correcting circuit for generating a corrected sum signal obtained by
correcting an amplitude variation of the sum signal with the difference signal;
and a data demodulating circuit for reproducing the information by generating data
information from the corrected sum signal.
The above-described recording/reproducing method and apparatus are effective
for an optical information recording medium in which no pair of adjacent address
regions or adjacent common address regions are formed so as to be aligned on a
straight line passing through the center of the disk, such as the second optical
information recording medium of the present invention, regardless of the number
of the recording layers.
A third optical information recording medium of the present invention includes
a disk-shaped transparent substrate and n recording layers (where n is an integer
of at least 2) for recording, reproducing or erasing information by irradiation
of laser light. The recording layers are formed over the substrate, and include
a first recording layer and a second recording layer, the first recording layer
including a first information track for guiding the laser light from an inner disk
circumference side to an outer disk circumference side by rotation of the disk
in a predetermined direction, and the second recording layer including a second
information track for guiding the laser light from an outer disk circumference
side to an inner disk circumference side by rotation of the disk in the predetermined direction.
The present invention also provides a method for recording/reproducing information
on the third optical information recording medium. This method is a method for
recording, reproducing or erasing information by irradiating the third optical
information recording medium with laser light, wherein when in either one recording
layer selected from the first recording layer and the second recording layer, recording,
reproducing or erasing information on either one information track selected from
the first information track and the second information track ends at either one
end selected from an inner circumferential end and an outer circumferential end
of the one information track, subsequently in the other recording layer, recording,
reproducing or erasing information is performed in succession from the corresponding
end in the other track.
This and other advantages of the present invention will become apparent to those
skilled in the art upon reading and understanding the following detailed description
with reference to the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of an embodiment of an optical information recording medium
of the present invention.
FIG. 2 is a partial perspective view showing an example of an enlarged surface
of the recording medium of FIG. 1.
FIG. 3 is a perspective view showing an example of a spiral of an information
track in the optical information recording medium of the present invention.
FIG. 4 is a plan view showing switched portions of an information track of the
optical information recording medium of FIG. 3.
FIG. 5 is a cross-sectional view of another embodiment of the optical information
recording medium of the present invention.
FIG. 6 is a cross-sectional view of yet another embodiment of the optical information
recording medium of the present invention.
FIG. 7 is a cross-sectional view of still another embodiment of the optical
information recording medium of the present invention together with the scanning
order of laser light.
FIG. 8 is a plan view of another embodiment of the optical information recording
medium of the present invention.
FIG. 9 is a partial perspective view showing an example of an enlarged surface
of the recording medium of FIG. 8.
FIG. 10 is a partial perspective view showing another example of an enlarged
surface of the recording medium of FIG. 8.
FIG. 11 is a partial plan view showing an example of an arrangement of information
recording regions and address regions in the optical information recording medium
of the present invention together with recording marks formed in the information
recording regions.
FIG. 12 is a partial plan view showing another example of arrangement of information
recording regions and address regions in the optical information recording medium
of the present invention together with recording marks formed in the information
recording regions.
FIG. 13 is a plan view of an optical information recording medium showing an
example of an arrangement of tracks for correcting servo conditions.
FIG. 14 is a partial plan view showing an example of an enlarged surface of
the recording medium of FIG. 13.
FIG. 15 is a partial plan view showing an example of a stamper production process
in a method for producing an optical information recording medium of the present invention.
FIG. 16 is a partial plan view showing an other example of a stamper production
process in a method for producing an optical information recording medium of the
present invention.
FIG. 17 is a configuration diagram showing an example of a recording/reproducing
apparatus for the optical information recording medium of the present invention.
FIG. 18 is a cross-sectional view showing a configuration of an optical head
of the recording/reproducing apparatus of FIG. 17.
FIGS. 19A to 19C are diagrams illustrating an example of a recording/reproducing
method using the recording/reproducing apparatus of FIG. 17. FIG. 19A is
a diagram showing an example of a sum signal of electrical signals obtained from
two light-receiving portions. FIG. 19B is a diagram showing an example of a difference
signal of the electrical signals. FIG. 19C is a diagram showing an example of a
sum signal corrected with the difference signal (corrected sum signal).
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, optical information recording media of the present invention
will be described with reference to the accompanying drawings.
First Embodiment
An optical information recording medium of the present invention includes a recording
layer (not shown) on a transparent substrate
1 having a thickness, for example,
of 0.6 mm. The substrate
1 is formed of polycarbonate or the like and is
provided with a circular center hole in its center with which the substrate is
mounted on a recording/reproducing apparatus, as shown in FIG.
1. The recording
layer is formed, for example, of a GeSbTe alloy, which is a phase change recording
material. In many cases, the recording layer formed of such a phase change recording
material is initialized (crystallized) for use. The recording layer is made amorphous
locally by irradiation of laser light to form recording marks. The substrate
1
previously is provided with a spiral information track
2 that is tracked
by laser light during recording/reproduction and on which information is recorded.
The information track
2 includes grooves
3 and lands
4 that
are formed alternately in the radial direction of the disk for the land & groove
recording method.
As shown in FIG. 2, laser light
8 is focused on the information track
2
with an objective lens
7 of a recording/reproducing apparatus. The laser
light
8 is irradiated from the lower portion of the FIG. 2, that is, after
passing through the substrate.
As shown in FIG. 3, the information track
2 is of a double spiral structure
in which the grooves
3 and the lands
4 form independent spirals from
each other. In the information track
2, information recording regions
5
and address regions
6 are arranged alternately in the circumferential direction
of the disk (the tracking direction of laser light). In other words, the information
track
2 has a sector format structure in which the information track
2
is segmented into a large number of regions by the address regions
6.
Information can be recorded and reproduced on this optical information
recording medium by irradiating the medium with laser light having a wavelength
of about 400 nm and condensed mainly by an objective lens having a NA of about
0.65, for example. The groove
3 is a recess formed on the substrate
1
having, for example, a depth of about 40 nm and a width of about 0.35 μm.
The land
4 is a protrusion having a width, for example, of about 0.35 μm
that remains between the grooves.
One of two edges (step portion) formed along both ends of the groove
3
is wobbled at a constant spatial frequency (in other words, at a constant cycle
along the tracking direction of the laser light). On the other hand, the other
edge is not wobbled. The spatial frequency is set to be constant within at least
the same information recording region
5. With this configuration, only the
wobble of one of the grooves adjacent to the land
4 is detected. Therefore,
even if the phases of the adjacent wobbles are dislocated, an adverse effect of
the wobbles on the signals for rotation control can be reduced.
In this recording medium, the address region
6 is constituted by embossed
pits formed on the groove
3 and the land
4. Therefore, even if the
track pitch is reduced, address information with a sufficiently large signal intensity
can be detected, compared with the medium in which address information is provided
by frequency modulation of the wobbles.
Thus, in the optical information recording medium, signals can be detected
from stable wobbles in the land as well as the groove, so that stable rotation
control can be achieved, and reliable detection of address information also can
be achieved. These effects are particularly significant in the case where the track
pitch (P in FIG. 2) is small, for example, 0.4 μm or less.
It is preferable that the address regions
6 are formed at a substantially
constant interval in the circumferential direction along the information track
(in other words, the length in the circumferential direction of each information
recording region is substantially uniform) in order to equalize the capacity of
each sector for recording/reproducing by the CLV method.
As shown in FIG. 1, in the recording medium having a double spiral structure,
a method for recording the information on either the land tracks or the groove
tracks and then recording the information on the other tracks later is advantageous,
particularly for recording animation information for a long time, because an access
operation can be eliminated during recording and reproduction. However, when the
track pitch is small, in some optical systems of recording apparatuses or recording
conditions, adjacent erase (cross erase) occurs where recording marks of information
track that have been recorded earlier are shrunk by heat energy transferred from
the information track for recording later, so that signal quality may deteriorate.
When the adjacent erase is predicted, it is preferable to compare the land track
and the groove track and to record information first on the track that provides
a larger signal amplitude in view of the relationship between the optical nature
of the recording layer and the groove shape of the information track. According
to this preferable example, even if signal quality is deteriorated by the adjacent
erase, the signal intensity of the information track used for earlier recording
can be at a sufficient level for demodulation. Thus, reproduction errors can be
suppressed. Alternatively, the width of the track for earlier recording can be
made wider than that of the track for later recording to suppress the deterioration
of the signal quality due to the adjacent erase.
In the recording medium, the information track is of a double spiral structure.
However, the structure is not limited thereto, and for example, a single spiral
structure in which a spiral is formed while switching the land and the groove about
by every one rotation can be used. In this case, the address regions
6 can
be formed as shown in FIG.
4. The single spiral structure of this form has
an advantage, because this makes it easy to record/reproduce information continuously
throughout the recording regions in the medium, using the CLV method as well as
the land & groove recording method.
When the edges of the grooves are wobbled, the groove width and the land width
are changed, and this change may affect reproduction signals. If it is necessary
to eliminate this adverse effect, it is preferable that the frequency of the wobbles
falls within the control band of a data demodulation circuit of a recording/reproducing
apparatus used for the recording medium. When the information is corrected by the
data demodulation circuit with the frequency of the wobbles, the data recorded
in the recording medium can be demodulated more reliably.
In the above example, the thickness of the transparent substrate is about 0.6
mm and the width of the groove track is about 0.35 μm on the assumption that
an apparatus including an objective lens of a NA of about 0.65 and laser light
of a wavelength of about 400 nm is used. However, this is only illustrative, and
the values are not limited thereto. For example, when it is assumed to use an apparatus
including an objective lens of a NA of about 0.85 and laser light of a wavelength
of about 400 nm, for example, the thickness of the transparent substrate can be
about 0.1 mm and the width of the groove track can be about 0.3 μm. The depth
of the groove track can be adjusted as appropriate.
As shown in FIGS. 1 and 4, it is preferable that the address regions do not coincide
with the straight line
12 that passes through the center of the disk (the
straight line including the diameter) in the radial direction of the disk. More
specifically, in these media, the address regions adjacent along the radial direction
of the disk are arranged so as not to be on the above-described straight line.
When the address regions are dispersed in their arrangement in this manner, information
can be recorded/reproduced stably, even if information is recorded/reproduced on
a recording layer by laser light that has passed through another recording layer,
the recording layers having a different transmittance in the address regions from
that in the information recording regions. This point will be described in Embodiment 2.
Embodiment 2
As shown in FIG. 5, an optical information recording medium of this embodiment
includes a one-sided two layered structure including two recording layers
14
and
16, and information is recorded, reproduced or erased on/from the recording
layers by irradiating the recording layers with laser light
19 from a substrate
13 side and focusing the light on the first recording layer
14 or
the second recording layer
16. The recording layers
14 and
16
are separated from each other by a separating layer
15. These layers
14,
15, and
16 are interposed between the substrate
13 and a protective
plate
18.
As shown in FIGS. 1 and 4, at least in the first recording layer
14, the
address regions adjacent along the radial direction of the disk are arranged so
as not to be on the straight line that passes through the center of the disk. Such
an arrangement prevents the angular positions of the address regions when viewed
from the disk center from being coincided with each other in the adjacent information
tracks. For this reason, the address regions are not arranged in the same angular
position in the same zone, unlike the case where the ZCLV is used.
When the address regions are arranged so as not to form a block in this manner,
a local change in the light amount of the laser light that passes through the first
recording layer
14 can be suppressed, even if the first recording layer
14 is formed of a recording layer having a different transmittance of laser
light in the address regions from that in the information recording regions, typically,
a material that allows a change in the transmittance of laser light due to formation
of recording marks. Therefore, a local influence on the reproduction signal level
from the second recording layer
16 advantageously can be reduced.
For example when the first recording layer
14 is formed of a material
that allows a reduction of the transmittance by recording information, the transmittance
of laser light in the address regions is higher than that in the information recording
regions in which recording marks are formed. On the other hand, when the first
recording layer
14 is formed of a material that allows an increase of the
transmittance by recording information, the transmittance of laser light in the
address regions is lower. However, if the address regions are not concentrated
on the region of the first recording layer
14 through which laser light
passes, this hardly causes a problem.
An effect obtained from the dispersion of the address regions is more significant
in an optical information recording medium as shown in FIG. 6, which is provided
with n′ recording layers (n′≧3) in total. For recording/reproducing
information on the n'th recording layer
17, the address regions can be arranged
in a non-linear form, as shown in FIGS. 1 and 4, at least in (n-;1) recording layers
positioned on the laser light incident side than the n'th layer
17. In the
recording medium shown in FIG. 6, as the recording medium shown in FIG. 5, the
separating layers
15 are disposed between the recording layers, and all
the layers are protected by the substrate
13 and the protective layer
18
from both surfaces. However, it is not necessary to form the separating layer between
all neighboring recording layers.
In this case, as in Embodiment 1, it is preferable for each recording layer to
have the sector format structure in which the information track is segmented into
a large number of sectors by the address regions, and it is preferable that the
address regions are formed at a substantially constant interval in the circumferential
direction so that the capacitor of each sector is equal when recording/reproducing
information by the CLV method. Also in this case, in the substrate
13, only
one edge of the groove is wobbled at a constant spatial frequency in the information
recording regions, and prepit addresses are arranged in the address regions.
Furthermore, in the multi-layered recording media as shown in FIGS.
5 and 6, it is preferable to form recording layers in which the spiral directions
of their information tracks are opposite when viewed from a predetermined direction.
This is because so-called seamless recording or seamless reproduction can be achieved.
This point will be described in Embodiment 3.
Embodiment 3
In an optical information recording medium of this embodiment, as shown in FIG.
7, the spiral directions of the information tracks of the first recording layer
14 and the second recording layer
16 are opposite to each other when
viewed from the laser light
19 incident side. Therefore, seamless recording
or seamless reproduction that uses the capacity of the recording medium to the
maximum can be achieved by using these two recording layers alternately.
For example, in FIG. 7, information can be recorded (or reproduced) in the following
manner. First, the laser light
19 is focused on the second recording layer
16, and information is recorded from an inner circumferential end A of a
second groove
22 toward the outer circumference. When the laser light
19
reaches an outer circumferential end B, the laser light is focused on an outer
circumferential end C in a first groove
20 of the first recording layer
14. Furthermore, information is recorded toward the inner circumference
of the first groove
20, and when laser light reaches an inner circumferential
end D, the laser light is focused again on an inner circumferential end E in a
second land
23 of the second recording layer
16. Subsequently, information
is recorded toward the outer circumference of the second land
23. When the
laser light reaches an outer circumferential end F, the laser light
19 is
focused on an outer circumferential end G in a first land
21 of the first
recording layer
14. Then, information is recorded toward an inner circumferential
end H in the first land
21. Herein, the outer circumferential end (inner
circumferential end) refers to the outer circumferential end (inner circumferential
end) of the region to be used for recording information.
When recording/reproducing information is performed continuously while transferring
from one recording layer to another recording layer at the end of the information
track, as appropriate, it is not necessary to move an optical head for switching
the information tracks while using all the information recording regions of the
medium. Therefore, seamless recording and seamless reproduction can be achieved
while using the capacity of the recording medium to the maximum.
In order to obtain opposite spiral directions of the information tracks of the
recording layers
14 and
16 of the recording medium shown in FIG.
5, for example, the spiral directions of the grooves of the substrate
13
and the protective plate
18 can be made opposite. In this case, the recording
layers
14 and
16 are formed on the substrate
13 and the protective
plate
18, respectively, and the substrate
13 and the protective plate
18 are attached with a UV curable resin that becomes the separating layer
in such a manner that the recording layers face each other. Thus, the recording
medium as shown in FIG. 5 can be obtained. The thickness of the separating layer
can be, for example, about 40 μm. However, the thickness is not limited thereto,
and a groove having a spiral direction opposite to that of the transparent substrate
can be formed on the separating layer
15. In this case, for example, the
first recording layer
14 and the separating layer
15 can be laminated
on the substrate
13 in this order, and an information track can be formed
in the separating layer
15 by a 2P(photo-polymerization) method or the like.
Then, the second recording layer
16 can be formed thereon, and then the
protective layer
18 can be provided.
In the recording medium including at least three recording layers as shown in
FIG. 6, if at least one recording layer provided with the information track having
a first spiral direction and at least one recording layer provided with the information
track having a second spiral direction that is opposite to the first direction
are included, the seamless recording (reproduction) in the same level as above
can be performed. In the case of at least three recording layers, the number of
recording layers (group) having the first spiral direction is equal to the number
of recording layers (group) having the second spiral direction, or else the difference
in the number of the layers is 1, so that seamless recording (reproduction) using
the capacity of the recording medium to the maximum can be performed.
There is no limitation on the order of recording information on the recording
layers. However, taking a recording layer of a two layered structure as an example,
when the first recording layer has the property that the transmittance of the laser
light is increased by recording information, it is preferable to record information
on the first recording layer first. On the other hand, when the first recording
layer has the property that the transmittance of the laser light is decreased by
recording information, it is preferable to record information on the second recording
layer first.
In this case, as in Embodiment 1, it is preferable for each recording layer to
have the sector format structure in which the information track is segmented into
a large number of sectors by the address regions, and it is preferable that the
address regions are formed at a substantially constant interval in the circumferential
direction so that the capacitor of each sector is equal when recording/reproducing
information by the CLV method. Also in this case as in the substrate
1 of
Embodiment 1, in the substrate
13, only one edge of the groove is wobbled
at a constant spatial frequency in the information recording regions, and prepit
addresses are arranged in the address regions.
Embodiment 4
This embodiment shows a variation of the prepit addresses in the address regions
shown in the above embodiments. In the optical information recording medium of
this embodiment shown in FIG. 8, as in the recording medium of Embodiment 1 shown
in FIG. 1, a recording layer (not shown) is provided on the substrate
1
on which grooves
3 and lands
4 are formed. The recording layer formed
on the surfaces of the groove and the land is provided with information tracks
2. The information track
2 has a sector format structure in which
information recording regions
75 and address regions
76 are arranged
alternately along the radial direction of the disk.
Also in this optical information recording medium, as shown in FIG. 9, only
one edge of the groove
3 is wobbled at a constant spatial frequency in the
recording regions
75. Since the other edge is not wobbled, the wobbled edges'
are arranged at every two edges in the radial direction of the disk. In the address
regions
76, prepit addresses
71 formed as an embossed pit group are
formed. Thus, also in the medium of this embodiment, signals can be detected stably
from the wobbles both in the land and the groove, while using the CLV method, so
that stable rotation control can be achieved. At the same time, reliable detection
of address information can be achieved. In this embodiment as well, it is preferable
that the address regions
76 are arranged at a substantially constant interval
in the circumferential direction along the information tracks so that the capacity
of each sector is equal when recording/reproducing information by the CLV method.
As shown in FIG. 9, in this embodiment, prepit addresses
71 are provided
on the extended line of the edge of the groove
3, and the land
4
and the groove
3 that are adjacent via this edge share the prepit addresses
71. The prepit addresses
71 are arranged at an interval equal to
the track pitch in the radial direction. The address regions
76 in which
common prepit addresses are formed are common address regions with respect to a
pair of information tracks that are adjacent in the radial direction of the disk.
If the common prepit addresses
71 are formed so as to straddle the boundary
of the pair of information tracks in this manner, the prepits can be made larger
than when the prepit addresses are formed for each information track so that the
prepits can be formed easily by, for example, injection molding. Furthermore, it
is preferable that a pair of information tracks having the common address region
share the wobbled step in the information recording region. This makes it possible
to form the wobbles in the groove tracks and the land tracks without discontinuation.
In the case where the prepit addresses common to a pair of a groove track and
a land track are formed as shown in FIG. 10, as in this embodiment, it is preferable
to form groove-land identifying pits
72 on at least one of the groove track
and the land track in the common address regions
76. The groove-land identifying
pits
72 shown in FIG. 9 are detected only when information is recorded/reproduced
on/from the groove track
3, so that reliable identification of the tracks
can be achieved. In this embodiment, the pits
72 are formed only on the
groove track
3, but the identifying pits can be formed only on the land
track
4 or both tracks. Furthermore, as shown in FIG. 10, it is preferable
to form the groove-land identifying pits
72 over the central line extending
in the circumferential direction of the track to be identified.
Embodiment 5
In this embodiment, a variation of the groove track and the land track of the
above-described embodiments will be described. The optical information recording
medium of this embodiment can be used as a recording medium in which the address
regions adjacent in the radial direction of the disk are not arranged on the straight
line that passes through the disk center.
In the recording medium in which the address regions are arranged as above, an
information region is adjacent to at least a part of the address region. Therefore,
as shown in FIG. 11, a recording mark
77 formed on the land track
4
is wider in the radial direction in the portion where the recording mark
77
is adjacent to the address region
76 (region A) than to the other information
region
75 (region B). Such a partial enlargeme
