U.S. patent application number 13/488514 was filed with the patent office on 2012-09-27 for multi-layer optical disc, information recording method and information reproducing method.
Invention is credited to Hideo Ando, Naoki Morishita, Seiji Morita, Naomasa Nakamura, Yasuaki Ootera, Koji Takazawa, Kazuyo Umezawa.
Application Number | 20120243396 13/488514 |
Document ID | / |
Family ID | 38442562 |
Filed Date | 2012-09-27 |
United States Patent
Application |
20120243396 |
Kind Code |
A1 |
Umezawa; Kazuyo ; et
al. |
September 27, 2012 |
MULTI-LAYER OPTICAL DISC, INFORMATION RECORDING METHOD AND
INFORMATION REPRODUCING METHOD
Abstract
According to one embodiment, single-sided dual-layer recordable
disc 100 may be used. Information recording is performed by forming
mark and space portions on data area DA using modulated laser
power. Pp denotes the maximum laser power or peak power for forming
the mark portion, and Pb denotes the bias power for forming the
space portion. Power ratio Pb/Pp is calculated for each of
recording layers L0 and L1. Information is recorded on any of the
recording layers L0 and L1 based on the result of calculation.
Here, the calculated power ratio Pb/Pp changes among the recording
layers L0 and L1, thereby optimizing the recording condition for a
multi-layer recordable optical disc within relatively short
time.
Inventors: |
Umezawa; Kazuyo; (Yokohama,
JP) ; Morita; Seiji; (Yokohama, JP) ;
Takazawa; Koji; (Tokyo, JP) ; Ando; Hideo;
(Hino, JP) ; Ootera; Yasuaki; (Yokohama, JP)
; Nakamura; Naomasa; (Yokohama, JP) ; Morishita;
Naoki; (Yokohama, JP) |
Family ID: |
38442562 |
Appl. No.: |
13/488514 |
Filed: |
June 5, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12973196 |
Dec 20, 2010 |
8218416 |
|
|
13488514 |
|
|
|
|
11755451 |
May 30, 2007 |
7869339 |
|
|
12973196 |
|
|
|
|
Current U.S.
Class: |
369/100 ;
369/275.1; G9B/7 |
Current CPC
Class: |
G11B 7/126 20130101;
G11B 7/00736 20130101; G11B 2007/0013 20130101 |
Class at
Publication: |
369/100 ;
369/275.1; G9B/7 |
International
Class: |
G11B 7/00 20060101
G11B007/00; G11B 7/24 20060101 G11B007/24 |
Foreign Application Data
Date |
Code |
Application Number |
May 31, 2006 |
JP |
2006-152718 |
Claims
1. An optical disc comprising: a recording layer, the recording
layer being configured to store information by using a peak power
and a particular power arranged next to or subsequent to the peak
power, a power level of the particular power being lower than that
of the peak power, wherein the optical disc includes a parameter
information area including parameter information relating to a
ratio of a numerator corresponding to the particular power to a
denominator corresponding to the peak power, and duration
information relating to a duration of one of multi pulses each
having the peak power.
2. A method of recording information on an optical disc comprising
a recording layer, the recording layer being configured to store
information by using a peak power and a particular power arranged
next to or subsequent to the peak power, a power level of the
particular power being lower than that of the peak power, wherein
the optical disc includes a parameter information area including
parameter information relating to a ratio of a numerator
corresponding to the particular power to a denominator
corresponding to the peak power, and duration information relating
to a duration of one of multi pulses each having the peak power,
the method comprising: recording information on the disc.
3. A method of reproducing information from an optical disc
comprising a recording layer, the recording layer being configured
to store information by using a peak power and a particular power
arranged next to or subsequent to the peak power, a power level of
the particular power being lower than that of the peak power,
wherein the optical disc includes a parameter information area
including parameter information relating to a ratio of a numerator
corresponding to the particular power to a denominator
corresponding to the peak power, and duration information relating
to a duration of one of multi pulses each having the peak power,
the method comprising: reading recorded information from the disc.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 12/973,196, filed Dec. 20, 2010, which is a divisional of U.S.
application Ser. No. 11/755,451, filed May 30, 2007, now U.S. Pat.
No. 7,869,339, and is based upon and claims the benefit of priority
from Japanese Patent Application No. 2006-152718, filed May 31,
2006. The entire contents of each of there documents are
incorporated herein by reference.
BACKGROUND
[0002] 1. Field
[0003] One embodiment of the present invention relates to an
optical disc (or an information storage medium using light in
general concept) by which information can be recorded on or
reproduced from two or more recording layers of the one side of the
disc, a recording method using the disc, and a reproducing method
using the disc.
[0004] 2. Description of the Related Art
[0005] As an optical disc, in general, there are a read-only ROM
disc, a recordable or re-recordable R disc, and a rewritable RW or
RAM disc. As information becomes bulky, further-large capacity is
demanded for an optical disc. For the purpose of increasing the
capacity of an optical disc, some technique has been proposed in
which a recording capacity is increased by narrowing down a beam
spot, for example, in such a manner that a wavelength of a laser
beam is shortened, or a numerical aperture NA is enlarged (for
example, refer to Jpn. Pat. Appln. KOKAI Publication No.
2004-206849, paragraphs 0036 to 0041, FIG. 1).
[0006] As multi-layered optical discs, dual-layer ROM discs are
conventionally available in the market. Recently, dual-layer
recordable discs (DVD-R:DL) each using a laser of 650 nm wavelength
are reduced to practice. In a manner of recording and reproducing
an optical disc (such as a DVD-R) using an organic dye material for
the recording layer, recording marks in which the reflectivity of
the dye has been changed are formed by modulating the power of a
laser light. Thus, the information recording is performed utilizing
the difference between the reflectivity of recording marks and that
of unrecorded portions. As a manner of modulating the laser power,
multi-pulses are used for DVD-R, for example (cf. Jpn. Pat. Appln.
KOKAI Publication No. 9-282660, abstract).
[0007] A single-layer recordable R disc configured to perform
recording with a laser wavelength of 405 nm is prepared, and
investigation is made for information recording on the disc. It is
found that the bias power, which is not so significant matter with
the recording of 650 nm laser wavelength, is very significant
matter to control the recorded mark length. Thus, the bias power
has an effect on recording characteristics. From this, the number
of parameters of the recording condition increases, to thereby
consume much time to find an optimum recording condition. The
inventors discover that an optimum recording condition (for
instance, a condition serving to determine the recording power to
achieve a minimum error rate where the wavelength and/or the
waveform is/are fixed) can be found in short time while changing
the recording power with a constant ratio of the recording power
(or the peak power of recording pulses) to the bias power, as a
given condition.
[0008] However, when similar information recording is performed for
a dual-layer R disc, a problem occurs. That is, the inventors are
faced with a problem that when the ratio of the recording power to
the bias power is fixed and recording is performed for each of the
layers, even if both the layers are formed of the same
recording-layer material, the recording characteristic of one of
the layers becomes significantly deteriorated.
[0009] Another problem is also found. That is, when an information
storage medium (especially a multi-layer optical disc configured to
perform high-density recording with a blue laser) is preserved for
a long period of time, and/or when the medium is preserved in
severe circumstances such as high-temperature and high-humidity, a
sufficient time is consumed to find the optimum recording
condition, because the optimum recording power may change after the
information storage medium is newly manufactured.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0010] A general architecture that implements the various features
of the invention will now be described with reference to the
drawings. The drawings and the associated descriptions are provided
to illustrate embodiments of the invention and not to limit the
scope of the invention.
[0011] FIG. 1 is an exemplary view illustrating a configuration of
a multi-layered optical disc according to an embodiment of the
invention;
[0012] FIG. 2 is an exemplary view showing a physical sector layout
of the optical disc shown in FIG. 1;
[0013] FIG. 3 is an exemplary view showing a configuration of the
lead-in area of the optical disc shown in FIG. 1;
[0014] FIG. 4 is an exemplary view showing a configuration of the
control data zone shown in FIG. 3;
[0015] FIG. 5 is an exemplary view showing a structure of one of
the data segments shown in FIG. 4;
[0016] FIG. 6 is an exemplary view showing contents of the physical
format information shown in FIG. 5;
[0017] FIG. 7 is an exemplary view showing a data area allocation
of the physical format information shown in FIG. 6;
[0018] FIG. 8 is an exemplary view showing a part (regarding L0) of
the physical format information shown in FIG. 5;
[0019] FIG. 9 is an exemplary view showing another part (regarding
L1) of the physical format information shown in FIG. 5;
[0020] FIG. 10 is an exemplary view showing a waveform (Write
Strategy) of a recording pulse;
[0021] FIG. 11 is an exemplary flowchart for explaining a recording
method according to one embodiment;
[0022] FIG. 12 is an exemplary flowchart for explaining a
reproducing method according to one embodiment; and
[0023] FIG. 13 is a view for explaining an example of recording on
a single-sided dual-layer optical disc wherein the power ratio for
the L0 layer differs from that for the L1 layer.
DETAILED DESCRIPTION
[0024] Various embodiments according to the invention will be
described hereinafter with reference to the accompanying
drawings.
[0025] One task of the embodiment is to optimize the recording
condition for a multi-layer recordable optical disc with a
relatively short period of time
[0026] In a recording method according to one embodiment,
information is recorded on a data area (DA) of a multi-layer disc
(100) having a plurality of recording layers (L0, L1) wherein mark
and space portions are formed using a laser whose output power is
modulated. Here, the mark portion is formed with a maximum laser
power represented by Pp, and the space portion is formed with a
bias power represented by Pb. Then, a power ration Pb/Pp of the
bias power Pb to the maximum laser power Pp is calculated (ST16)
for each of the recording layers (L0, L1), and
[0027] information is recorded (ST14-ST22) on any of the recording
layers (L0, L1) based on a result of the calculating with a
condition that the calculated power ratio Pb/Pp changes among the
recording layers (L0, L1). (Since at ST16 the Pb/Pp of L0 is
calculated separately from or independently of the Pb/Pp of L1, the
former Pb/Pp can differ from the latter Pb/Pp.)
[0028] An optimum condition of recording (e.g., a condition
determining the recording power to achieve a minimum error rate
where the wavelength and the waveform are fixed) on an optical disc
having a plurality of recording layers can be found with a
relatively short period of time.
[0029] Various embodiments will be described with reference to the
accompanying drawings. FIG. 1 shows an example of the configuration
of multi-layer optical disc (a recordable or re-recordable
single-sided dual-layer disc as a practical example) 100 according
to one of the embodiments. As exemplified by (a) and (b) of FIG. 1,
disc 100 comprises transparent resin substrate 101 having a
disc-like figure and being formed of a synthetic resin material
such as polycarbonate, for example. Grooves are coaxially or
spirally formed on transparent resin substrate 101. Transparent
resin substrate 101 may be manufactured by injection molding with a
stamper.
[0030] On transparent resin substrate 101 with 0.59 mm thickness
and made of polycarbonate or the like, organic dye recording layer
105 and semi-transparent light-reflection or light-reflective layer
106 are sequentially laminated or stacked for the first layer (L0).
Photo Polymer (abbreviated as 2P resin) intermediate layer 104 is
spin-coated on layer 106. Then, the groove pattern of the second
layer (L1) is transferred to layer 104, and organic dye recording
layer 107 and reflection or reflective film 108 of silver or silver
alloy are sequentially laminated or stacked for the second layer
(L1). To the body on which L0 and L1 recording layers are laminated
or stacked, another transparent resin substrate (or dummy
substrate) 102 with 0.59 mm thickness is pasted via UV curing resin
(adhesive layer) 103. The organic dye recording films (recording
layers 105 and 107) have a dual-layer configuration in which
semi-transparent reflection or reflective layer 106 and
intermediate layer 104 are sandwiched between the organic dye
recording films. The total thickness of the resultant pasted
optical disc is about 1.2 mm.
[0031] On transparent resin substrate 101, spiral grooves with the
track pitch of 0.4 .mu.m and the depth of 60 nm, for example, are
formed (for respective layers L0 and L1). The grooves are wobbled
so that address information is recorded on the wobble. Further,
recording layers 105 and 107 each including an organic dye are
formed on transparent resin substrate 101 so as to fill-up the
grooves.
[0032] As the organic dye for forming recording layers 105 and 107,
a dye material whose maximum absorption wavelength area is shifted
to the longer wavelength side than the recording wavelength (e.g.,
405 nm) may be used. Note that the dye material is designed to have
a substantially large light absorption at the longer wavelength
area (e.g., 450 nm to 600 nm), and the absorption does not
disappear at the recording wavelength area.
[0033] The organic dye is dissolved in a solvent to provide a
liquid material. The recording film thickness can be precisely
managed by controlling the dilution rate of the solvent and/or the
rotating speed of spin-coating.
[0034] A cyanine dye, styryl dye, azo dye, or the like may be used
as an organic dye applicable to the embodiment. Particularly, the
cyanine dye or the styryl dye is suitable because control of the
absorption with respect to the recording wavelength is easy. The
azo dye may be obtained as a single azo compound or as a complex of
a metal and one or more molecules of an azo compound.
[0035] In the embodiment, cobalt, nickel, or copper may be used for
the center metal M of the azo metal complex so as to enhance the
optical stability. However, without being limited thereto, there
may be used for the center metal M of the azo metal comprex:
scandium, yttrium, titanium, zirconium, hafnium, vanadium, niobium,
tantalum, chrome, molybdenum, tungsten, manganese, technetium,
rhenium, iron, ruthenium, osmium, rhodium, iridium, palladium,
platinum, silver, gold, zinc, cadmium, or mercury and the like.
[0036] A low light reflectivity may be met when a recording laser
light is focused on or tracking over the track before recording of
information. Thereafter, the dye is subjected to a resolving
reaction by the laser light to reduce the optical absorption rate,
so that the light reflectivity at the recording mark portion is
enhanced. From this, a so-called "Low-to-High" (or "L to H")
characteristic is obtained wherein the light reflectivity at the
recording mark portion formed by irradiating the laser light
becomes higher than the light reflectivity obtained before the
laser light irradiation.
[0037] Incidentally, in transparent resin substrate 101,
particularly at the groove bottom portion (of L0 or L1), some
deformations may be caused by heat generated due to the irradiation
of the recording laser. In this case, in a reproduction process
after recording, a phase difference (compared with the case of no
heat deformation) could occur in the reflected laser light.
[0038] According to the embodiment, a physical format that can be
applied to the L0 and L1 layers on transparent resin substrate 101
and photo polymer (2P resin) 104 may be as follows: Namely, general
parameters of a recordable single-sided dual-layer disc are almost
the same as those of a single-layer disc, exept for the following.
That is, the user-available recording capacity is 30 GB, the inner
radius of layer 0 (L0 layer) of the data area is 24.6 mm, the inner
radius of layer 1 (L1 layer) thereof is 24.7 mm, and the outer
radius (of each of layer 0 and layer 1) of the data area is 58.1
mm.
[0039] In optical disc 100 of FIG. 1(a), system lead-in area SLA
includes a control data section as exemplified by FIG. 1(c). The
control data section includes, as a part of physical format
information, etc., recording-related parameters such as recording
power (peak power), bias power, and the like, for each of L0 and
L1.
[0040] On the track within data area DA of optical disc 100, as
exemplified by FIG. 1(d), mark/space recording is done by the laser
with a given recording power (peak power) and bias power. By this
mark/space recording, as exemplified by FIG. 1(e), object data
(such as VOB) and its management information (VMG) of a
high-definition TV broadcasting program, for example, are recorded
on the track (of L0 and/or L1) in data area DA.
[0041] <<Format of Information Area>>
[0042] FIG. 2 is an exemplary view showing a physical sector layout
of optical disc 100 shown in FIG. 1. As exemplified in FIG. 2, the
information area provided throughout the dual layers includes seven
areas: the System Lead-in area, Connection area, Data Lead-in area,
Data area, Data Lead-out area, System Lead-out area, and Middle
area. The Middle area on each layer allows the read-out beam to
move from Layer 0 (L0) to Layer 1 (L1). Data area DA is intended
for recording of the main data (such as management information VMG,
object data VOB, etc. in the example of FIG. 1(e)). System Lead-in
area SLA contains the Control data and Reference code. The Data
Lead-out area allows for a continuous smooth read-out.
[0043] <<Lead-Out Area>>
[0044] The System Lead-in area and System Lead-out area contain
tracks which consist of a series of embossed pits. The Data Lead-in
area, Data area and Middle area on Layer 0 (L0), and the Middle
area, Data area and Data Lead-out area on Layer 1 (L1) include a
series of groove tracks. The groove tracks are continuous from the
start of the Data Lead-in area to the end of the Middle area on
Layer 0 and from the start of the Middle area to the end of the
Data Lead-out area on Layer 1. When two single-sided dual-layer
discs are pasted on each other, a double-sided quadruplex-layer
disc having two read-out surfaces is manufactured.
[0045] FIG. 3 is an exemplary view showing a configuration of the
lead-in area of the optical disc shown in FIG. 1. As exemplified in
FIG. 3, system lead-in area SLA of Layer 0 is composed of an
initial zone, a buffer zone, a control data zone, and a buffer zone
in sequence from the inner peripheral side. The data lead-in area
of Layer 0 is composed of a blank zone, a guard track zone, a drive
test zone, a disc test zone, a blank zone, an RMD duplication zone,
an L-RMD (recording management zone in the Data Lead-in area), an
R-physical format information zone, and a reference code zone in
sequence from the inner peripheral side. A starting address (inner
peripheral side) of the data area of Layer 0 (L0) and an ending
address (inner peripheral side) of the data area of Layer 1 (L1)
are shifted by a distance of a clearance, and the ending address
(inner peripheral side) of the data area of Layer 1 is at a side
outer than the starting address (inner peripheral side) of the data
area of Layer 0.
[0046] <<Structure of Lead-In Area>>
[0047] FIG. 3 exemplifies a configuration of the lead-in area of
Layer 0 (L0). The system lead-in area is composed of an initial
zone, a buffer zone, a control data zone, and a buffer zone in
sequence from the inner peripheral side. The data lead-in area is
composed of a blank zone, a guard track zone, a drive test zone, a
disc test zone, a blank zone, an RMD duplication zone, a recording
management zone in the data lead-in area (L-RMD), an R-physical
format information zone, and the reference code zone in sequence
from the inner peripheral side.
[0048] <<Details of System Lead-In Area>>
[0049] The initial zone contains embossed data segments. The main
data of the data frame recorded as the data segment of the initial
zone is set to "00h". The buffer zone is formed of 1024 Physical
sectors from 32 Data segments. The Main data of the Data frames
eventually recorded as Data segments in this zone is set to "00h".
The Control data zone contains embossed Data segments. The Data
segments contain embossed Control data. The Control data is
comprised of 192 Data segments starting from PSN 123904 (01
E400h).
[0050] FIG. 4 exemplifies a configuration of the control data zone,
and FIG. 5 exemplifies a structure of the data segment of the
control data section. The contents of the first Data segment in a
Control data section is repeated 16 times. The first Physical
sector in each Data segment contains the physical format
information. The second Physical sector in each Data segment
contains the disc manufacturing information. The third Physical
sector in each Data segment contains the copyright protection
information. The contents of the other Physical sectors in each
Data segment are reserved for system use.
[0051] FIG. 6 exemplifies the physical format information in the
control data section of FIG. 5, and FIG. 7 exemplifies the data
area allocation of the physical format information. The contents of
description of respective bite positions (BP) for the physical
format information are as follows. The values specified for the
Read power, Recording speeds, Reflectivity of Data area, Push-pull
signal, and On-track signal given in BP 132-154 are only for
example. Their actual values may be determined by a disc
manufacture provided that the values are chosen within the values
satisfying the emboss condition and the recorded user data
characteristics. The details of the data area allocation given in
BP 4-BP15 are shown in FIG. 7, for example.
[0052] BP149 and BP152 of FIG. 6 specify reflectance ratios of the
data areas of Layer 0 and Layer 1. For example, 0000 1010b denotes
5%. An actual reflectance ratio can be specified by the following
formula:
Actual reflectance ratio=value.times.(1/2).
[0053] BP150 and BP153 specify push-pull signals of Layer 0 and
Layer 1. In respective BP's, bit b7 (not shown) specifies a track
shape of the disc of each layer, and bits b6 to b0 (not shown)
specify amplitudes of the push-pull signals as:
[0054] Track shape: 0b (track on a groove) [0055] 1b (track on a
land)
[0056] Push-pull signal: 010 1000b denotes 0.40, for example.
[0057] An actual amplitude of a push-pull signal is specified by
the following formula:
Actual amplitude of push-pull signal=value.times.(1/100).
[0058] BP151 and BP154 specify amplitudes of on-track signals of
Layer 0 and Layer 1:
[0059] On-track signal: 0100 0110b denotes 0.70, for example.
[0060] An actual amplitude of an on-track signal is specified by
the following formula:
Actual amplitude of on-track signal=value.times.(1/100).
[0061] Incidentally, recording-related parameters for L0 as
exemplified by FIG. 8 may be described at BP512 to BP543 of the
physical format information. Information of the initial peak power
and/or bias power, etc. for the L0 layer recording can be obtained
from the description of FIG. 8. Further, recording-related
parameters for L1 as exemplified by FIG. 9 may be described at
BP544 to BP2047 of the physical format information. Information of
the initial peak power and/or bias power, etc. for the L1 layer
recording can be obtained from the description of FIG. 9.
[0062] An evaluation disc of recordable dual-layered optical disc
100 according to one embodiment can be made as follows. More
specifically, on transparent resin substrate 101, a 1.2 wt % TFP
solution of an organic dye is applied by spin coating to form L0
recording layer 105. The thickness of the dye after application
from the bottom of the groove is set to be 60 nm. Reflecting film
106 of an Ag alloy with 25 nm thick is laminated or stacked on the
dye-coated substrate by sputtering, and intermediate layer 104 of
2P (photo polymer) resin with 25 .mu.m thickness is spin-coated. A
separately prepared polycarbonate stamper is placed thereon to
transfer the groove shape, and the stamper is removed. On the 2P
resin intermediate layer 104 thus prepared, a 1.2 wt % TFP solution
of an organic dye is applied by spin coating to form L1 recording
layer 107. Reflection or reflective film 108 of an Ag alloy is
laminated or stacked thereon with a thickness of 100 nm by
sputtering, and pasted with 0.59 mm thick transparent resin
substrate 102 by using UV hardening resin 103.
[0063] Using the information storage medium (a single-sided
dual-layer evaluation disc) produced as described above, an
experiment for evaluating a reproduction signal is performed.
[0064] The apparatus used for evaluation is optical disc evaluation
apparatus ODU-1000 manufactured by Pulstec Industrial Co., Ltd.
This apparatus has a laser wavelength of 405 nm and NA of 0.65. The
linear velocity in recording and reproduction is selected to be
6.61 m/s. A recording signal is 8-12 modulated random data, and
information is recorded by using a laser waveform containing a
given recording power and two bias powers 1 and 2 as shown in FIG.
10. The recording conditions applied to the evaluation are as
follows.
[0065] Explanation on Recording Conditions (Information of Write
Strategy)
[0066] Referring to FIG. 10, a description will be given with
respect to a recording waveform (exposure condition at the time of
recording) used when the optimal recording power is checked. The
exposure levels at the time of recording have four levels of
recording power (peak power), bias power 1, bias power 2, and bias
power 3. When long (4T or more) recording mark 9 is formed,
modulation is carried out in the form of multi-pulses between
recording power (peak power) and bias power 3. In the embodiment,
in any of the H format and B format systems, a minimum mark length
relevant to channel bit length T is obtained as 2T. In the case
where the minimum mark of 2T is recorded, one write pulse of the
recording power (peak power) level after bias power 1 is used as
shown in FIG. 34, and bias power 2 is temporarily obtained
immediately after the write pulse. In the case where 3T recording
mark 9 is recorded, bias power 2 is temporarily used after exposing
two write pulses, a first pulse and a last pulse of recording power
(peak power) level that follows bias power 1. In the case where
recording mark 9 having a length of 4T or more is recorded, bias
power 2 is used after the exposure is made with multi-pulse and
write pulse.
[0067] The vertical dashed line in FIG. 10 shows a channel clock
cycle (T). When a 2T minimum mark is recorded, the laser power is
raised at a position delayed by TSFP from the clock edge, and
fallen at a position delayed by TELP from the one-clock passing
portion. The just-subsequent cycle during which the laser power is
set at bias power 2 is defined as TLC. Values of TSFP, TELP, and
TLC are recorded in physical format information PFI contained in
control data zone CDZ in the case of the H format.
[0068] In the case where a 3T or more long recording mark is
formed, the laser power is risen at a position delayed by TSFP from
the clock edge, and lastly, ended with a last pulse. Immediately
after the last pulse, the laser power is kept at bias power 2
during the period of TLC. Shift times from the clock edge to the
rise/fall timing of the last pulse are defined as TSLP, TELP. In
addition, a shift time from the clock edge to the fall timing of
the last pulse is defined as TEFP, and further, an interval of a
single pulse of the multi-pulse is defined as TMP.
[0069] Each of intervals TELP-TSFP, TMP, TELP-TSLP, and TLC is
defined as a half-value wide relevant to the maximum value. In
addition, in the embodiment, the above parameter setting ranges are
defined as follows:
0.25T.ltoreq.TSFP.ltoreq.1.50T (eq. 01)
0.00T.ltoreq.TELP.ltoreq.1.00T (eq. 02)
1.00T.ltoreq.TEFP.ltoreq.1.75T (eq. 03)
-0.10T.ltoreq.TSLP.ltoreq.1.00T (eq. 04)
0.00T.ltoreq.TLC.ltoreq.1.00T (eq. 05)
0.15T.ltoreq.TMP.ltoreq.0.75T (eq. 06)
[0070] Further, in the embodiment, the values of the above
described parameters can be changed or modified according to the
recording mark length (Mark Length) and the immediately
preceding/immediately succeeding space length (Leading/Trailing
space length).
[0071] For the recordable information storage medium whose
recording is to be performed based on the recording theory of the
embodiment, parameters of the optimum recording power are
investigated. The result is that the values of bias power 1, bias
power 2, and bias power 3 are 2.6 mW, 1.7 mW, and 1.7 mW,
respectively, and reproduction power is 0.4 mW.
[0072] Optimum recording conditions (information of Write Strategy)
can be determined with an apparatus (disc drive) by which a test
writing has been done at a drive test zone accoring to the
respective parameter values as mentioned above.
[0073] FIG. 11 is an exemplary flowchart for explaining a recording
method according to one embodiment. In the following an example of
determining the optimum recording condition for dual-layer optical
disc 100 will be described with reference to this flowchart. First,
recording-related parameters (cf. FIGS. 6 to 9) are obtained from
the data described in system lead-in area SLA (ST10).
[0074] To minimize as much as possible the time for determining the
recording condition, the read-out parameters are used for test
recording (for example, the values of peak power Pp and bias power
Pb in FIG. 8 are used for test recording of layer L0, and the
values of peak power Pp and bias power Pb in FIG. 9 are used for
test recording of layer L1) (ST12). Then, the bit error rate (SbER)
of a reproduction signal from the test recording portion is
measured. When the result of measured SbER is more wrong than a
predetermined threshold value (e.g., 5.0 e-5) (NG at ST14), the
value of Pb/Pp is calculated (ST16) from the parameters described
in the data read-out from the system lead-in. Subsequently, the
recording power is changed with constant Pb/Pp (ST18), and new test
recording is done using the changed recording power (ST12).
Thereafter, similar measuring process for SbER (processing loop of
ST12 to ST18) is repeated to grope for or to find out the optimum
recording condition.
[0075] When the measured SbER is better than the threshold value
(e.g., 5.0 e-5) (OK at ST14), it is determined that the recording
condition providing the measured result is an optimum recording
condition (ST20). Then data recording is started for the tested
target recording layer (L0 and/or L1). The data recording is
continued with the optimum recoring condition determined at ST20
(ST22, no at ST22).
[0076] Although SbER is used for determining whether the test
recording condition is suitable, another index (such as data error
rate and/or information (such as PRSNR) relating to a signal to
noise ratio) may be used so long as the index can be used for
evaluating the recording quality.
[0077] In the embodiment, physical format information in the system
lead-in (and/or in lead-out) of the information storage medium is
read out first, and test recording is done using the parameters
being set by the read-out information. However, the test recording
may be done with a default constant value of Pb/Pp, and
subsequently, optimizing processing to grope for the optimum
recording condition may be performed while changing the recording
power suitably.
[0078] In the embodiment, parameters of the used Pb/Pp may be newly
recorded in the information storage medium, and the newly recorded
parameters may be read out to be used for the subsequent recording.
By so doing, the time for optimizing processing can be made shorter
than before.
[0079] In the embodiment, parameters already recorded on the
information storage medium are read out and used. However, a
recorder apparatus (or a disc drive) may have a memory (ROM) in
which recorded is a list of information items of Pb/Pp applied to
typical disc models (or grades) any of which will possibly be used
for the apparatus (or the drive).
[0080] In the embodiment, data in the system lead-in is used for
the information reading from the disc. However, other one such as
data recorded in a wobble signal may be used.
[0081] FIG. 12 is an exemplary flowchart for explaining a
reproducing method according to one embodiment. In reproduction
processing, management information (such as VMG in FIG. 1(e)) of
the recorded contents is read out (ST30) from the prescribed track
of optical disc 100 on which recording is done with the optimum
recording condition obtained based on the processing of FIG. 11.
The related object data (video object VOB, stream object SOB, or
the like) is reproduced based on the contents described in the
read-out management information (ST32).
[0082] As explained with reference to FIG. 11, when information
recording is performed on a multi-layer optical disc, the ratios of
the recording power (peak power) to the bias power are set to be
different among respective recording layers, and the preset ratios
of the recording power to the bias power are used for the
respective recording layers. By so doing, it is possible to find
out a suitable recording condition (for instance, a condition to
make the error rate lower than a predetermined threshold value
determined in view of practical use or the like where the recording
wavelength and recording waveform is fixed for respective layers)
with a relatively short period of time. This is because, in
multi-layered recording layers, aberrations of the laser light
and/or thermal influence of the information storage medium may be
different among respective layers, or differences are found in the
distances from the laser spot to the recording layers (the
differences depend on whether or not a light passing through other
semi-transparent recording layer is to be used), so that the
relations between the bias power and the recording power become
different among the layers. From this, optimizing is to be
independently performed for each of the layers.
[0083] FIG. 13 shows data supporting the above discussion. FIG. 13
exemplifies a case wherein at least .+-.5% (about 20% in the
illustrated example) of difference is found between the curve of
error rate SbER vs power ratio [Pb/Pp]a for layer L0 and that of
error rate SbER vs power ratio [Pb/Pp]b for layer L1 when recording
is done using single-sided dual-layer optical disc 100.
SUMMARY
[0084] An information recording method is applied to a recordable
information storage medium (such as a recordable or rewritable
optical disc) comprising at least a substrate, two or more
recording layers sandwiching an intermediate layer, and a groove
coaxially or spirally formed on the substrate. In this method,
information is recorded on the information storage medium using a
laser whose output power is modulated. When the maximum high power
(peak power) used for forming a mark portion is represented by Pp
and the light power (bias power) used for forming a space portion
is represented by Pb, the ratio Pb/Pp of one of the recording
layers (L0, L1, etc.) is set to be different from another one of
the recording layers.
[0085] To achieve a quick start of information recording (or to
reduce a waiting time as much as possible from the disc loading to
the drive to a state in which actual data recording can be
started), pre-recorded physical format information (including
information of the recording power, etc.) is read out from the
optical disc, and the ratio Pb/Pp to be used is determined based on
the read-out information. This Pb/Pp may be obtained directly from
the optical disc, or may be calculated from the recording power
(peak power) and the bias power respectively read out from the
disc.
[0086] A recordable or rewritable optical disc according to one
embodiment comprises at least a substrate, two or more recording
layers sandwiching an intermediate layer, and a groove coaxially or
spirally formed on the substrate. Information is recorded on the
optical disc by modulating the output power of a laser. When the
maximum high power (peak power) used for forming a mark portion is
represented by Pp and the light power (bias power) used for forming
a space portion is represented by Pb, the ratio Pb/Pp of one of the
recording layers (L0, L1, etc.) is set to be different from another
one of the recording layers.
[0087] At least information of the recording power and the bias
power for respective recording layers is stored in the optical
disc. The ratio of the recording power (peak power) to the bias
power described for one layer differs from that for another layer.
From the stored information of the recording power and the bias
power for each of the layers, it is possible to obtain the optimum
recording condition for each of the layers with a relatively short
period of time (when compared with a case wherein no such
information is available).
[0088] A recording method according to the embodiment is
particularly effective when a recordable optical disc (in which
only one recording is allowed for the same recording portion) is
used. When a single-sided dual-layer optical disc is used, it is
better to select a condition that the bias power for recording the
second layer (L1) is higher than that for recording the first
recording layer (L0) which is nearer to the optical reception
surface than L1.
[0089] While certain embodiments of the inventions have been
described, these embodiments have been presented by way of example
only, and are not intended to limit the scope of the inventions.
Indeed, the novel methods and systems described herein may be
embodied in a variety of other forms. For instance, the invention
(including an idea of obtaining the optimum recording condition
using different power ratios for respective recording layers) can
be reduced to practice not only in a dual-layer R (recordable or
write-once) disc, but in a multi-layer RW (rewritable) disc or in a
multi-layer RAM disc.
[0090] Furthermore, various omissions, substitutions and changes in
the form of the methods and systems described herein may be made
without departing from the spirit of the inventions. The
accompanying claims and their equivalents are intended to cover
such forms or modification as would fall within the scope and
spirit of the inventions.
* * * * *