U.S. patent application number 12/977970 was filed with the patent office on 2011-04-21 for optical information recording method, optical information recording device and optical information recording medium.
This patent application is currently assigned to PANASONIC CORPORATION. Invention is credited to Shigeaki FURUKAWA, Kenji NARUMI, Kenichi NISHIUCHI.
Application Number | 20110090778 12/977970 |
Document ID | / |
Family ID | 29243484 |
Filed Date | 2011-04-21 |
United States Patent
Application |
20110090778 |
Kind Code |
A1 |
NARUMI; Kenji ; et
al. |
April 21, 2011 |
OPTICAL INFORMATION RECORDING METHOD, OPTICAL INFORMATION RECORDING
DEVICE AND OPTICAL INFORMATION RECORDING MEDIUM
Abstract
The present invention provides an optical information recording
apparatus and method capable of effectively determining appropriate
recording parameters in a short time with favorable efficiency,
when recording information onto an optical disk having different
information recording conditions and information recording
characteristics. An information recording condition or an
information recording characteristic of an optical disk 1 is
identified, and a recording pulse position is corrected at a
correction accuracy according to the identifies information
recording condition or information recording characteristic, such
that a recording mark is formed in a predetermined position.
Inventors: |
NARUMI; Kenji; (Osaka,
JP) ; NISHIUCHI; Kenichi; (Osaka, JP) ;
FURUKAWA; Shigeaki; (Nara, JP) |
Assignee: |
PANASONIC CORPORATION
Osaka
JP
|
Family ID: |
29243484 |
Appl. No.: |
12/977970 |
Filed: |
December 23, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12846439 |
Jul 29, 2010 |
7881173 |
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12977970 |
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11973740 |
Oct 10, 2007 |
7813239 |
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12846439 |
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10511931 |
Oct 18, 2004 |
7760596 |
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PCT/JP03/04874 |
Apr 17, 2003 |
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11973740 |
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Current U.S.
Class: |
369/53.31 ;
G9B/27.052 |
Current CPC
Class: |
G11B 7/1267 20130101;
G11B 7/0062 20130101; G11B 7/00456 20130101; G11B 7/00736
20130101 |
Class at
Publication: |
369/53.31 ;
G9B/27.052 |
International
Class: |
G11B 27/36 20060101
G11B027/36 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 19, 2002 |
JP |
2002-117247 |
Claims
1-59. (canceled)
60. An optical information recording method for recording
information onto an optical information medium containing a control
track region, the method comprising: an identifier detection step
that reproduces information from the control track region and
detects an identifier that represents a linear recording velocity
of the optical information recording medium; a recording pulse
correction step of correcting at least one of elements to be
corrected by each resolution, which is a minimum unit of increase
or decrease of a correction amount, in order to form a recording
mark in a predetermined position; wherein in the recording pulse
correction step, the resolution is differentiated according to a
recording linear velocity represented by the identifier detected in
the identifier detection step, and the correction is performed with
a correction amount, which is a total amount of at least one
minimum unit corresponding to the differentiated resolution.
61. An information recording medium onto which data are recorded by
recording a mark by the optical information recording method
according to claim 60.
62. A reproduction method comprising: reproducing data by reading a
mark recorded on a recording medium by the optical information
recording method according to claim 60.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation of U.S. application Ser.
No. 12/846,439, filed Jul. 29, 2010, which is a Continuation of
application Ser. No. 11/973,740, filed Oct. 10, 2007, which is a
Divisional of application Ser. No. 10/511,931, filed Oct. 18, 2004,
which is a U.S. National Stage of PCT/JP03/04874, filed Apr. 17,
2003, which applications are incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to optical information
recording media, such as optical disks, for optically recording and
reproducing information, and information recording methods and
information recording apparatuses that use the optical information
recording media.
BACKGROUND ART
[0003] In recent years, optical disks, optical cards and optical
tapes and the like have been proposed and developed as media for
optically recording information. Of these, optical disks have come
in for particular attention as media that are capable of recording
and reproducing information, both in large volumes and at high
density. A phase change-type optical disk is one type of rewritable
optical disk. In order to obtain the desired thermal and optical
characteristics in phase change-type optical disks, it is common to
use a multi-layered film configuration in which layers such as
dielectric layers and reflecting layers are added onto the
recording layer. The recording layer that is used in the phase
change-type optical disk is either amorphous or crystalline,
depending on the heating and cooling conditions caused by the laser
light, and is reversible between the amorphous and crystalline
states. The optical indices (refractive index and attenuation
co-efficient) of the recording layer differ between the amorphous
and crystalline states. In the phase change-type optical disk, the
two states are selectively formed on the recording film in response
to an information signal, and the optical changes (changes in
transmittance or reflectance) that occur as a result are utilized
to record and reproduce the information signal.
[0004] In order to obtain the two states, the information signal is
recorded by a method such as described below. A laser light (power
level Pp) that is focused by the optical head is irradiated onto
the recording film of the optical disk in pulses (known as
recording pulses) to raise the temperature of the recording film.
When the temperature exceeds the melting temperature, the recording
film melts, and after the passage of the laser light, the
melted
portion rapidly cools to become an amorphous recording mark (also
known as a mark). It should be noted that the power level Pp is
known as the peak power. Furthermore, when the light, whose
intensity is of a level that raises the temperature of the
recording film to more than the crystallizing temperature and less
than the melting temperature, is focused and emitted by a laser
light (power level Pb, where Pb<Pp) the irradiated portion of
the recording film is crystallized. It should be noted that the
power level Pb is known as the bias power. Furthermore, the peak
power and the bias power more generally are referred to as
recording power.
[0005] In this manner, a recording pattern of recording marks,
which are created from amorphous regions that correspond to the
recording data signal, and non-mark portions (also known as
"spaces"), which are made of crystalline regions, is formed on a
track of the optical disk. Thus, an information signal can be
reproduced, utilizing the difference in optical characteristics
between the crystalline regions and the amorphous regions.
[0006] Furthermore in recent years, use of the mark edge recording
method (also known as PWM recording) has increased, replacing the
mark position recording method (also known as PPM recording). As
opposed to mark position recording, in which information is only
held in the position of the recording mark itself, in mark edge
recording, information is held in both the forward and back end of
the edge of the recording mark, and thus it is advantageous for
increasing the recording line density.
[0007] In the case of mark edge recording, the recording pulse
during recording of a long mark is divided into a sequence of a
plurality of recording pulses (these are known as multi pulses),
and a recording method is used in which the width of the front
pulse (known as the front end pulse) is made larger than the width
of the middle pulses or the width of the last pulse (known as the
back end pulse). Considering the influence of excess heat that is
transmitted from the front portion of the mark, this is in order to
lessen the distortion of the recording mark shape, and to record a
more accurate mark by reducing the heat applied to the recording
film when recording the rear portion of the mark to less than that
which is applied when recording the front portion of the mark.
[0008] Coincidentally, in the case of the mark edge recording
method, differences in thermal characteristics of optical disks
affect the shape of the recording mark itself, and the degree of
thermal interference between recording marks. That is to say, even
if recorded by the same recording pulse waveform, the shape of the
recording mark that is formed will differ between disks. As a
result, the edge of the recording mark may be offset from the ideal
position, depending on the disk, and the quality of the signal that
is reproduced may drop. Because of this, methods have been proposed
with which a recording mark can be recorded at an ideal edge
position by optimally correcting the recording power, front end
pulse edge position or back end pulse edge position for any
disk.
[0009] As a method for correcting the front end pulse edge position
or the back end pulse edge position, a method has been proposed in
which combinations of code lengths that correspond to recording
marks (known as recording code lengths), and code lengths that
correspond to spaces before or after the recording marks (known
respectively as pre-code length and post-code length) are provided
in a correction table, and the front end pulse edge position and
the back end pulse edge position are corrected according to
correction values for the combinations in the correction table
(known as correction table elements).
[0010] Furthermore, as a test recording method for correcting the
front end pulse edge position and the back end pulse edge position,
a method that corrects the front end pulse edge position or the
back end pulse edge position has been disclosed in which before
recording an actual information signal, a test pattern that has a
specific period (known as a test pattern) is recorded, after which
the test signal that was recorded is reproduced, and the front end
pulse edge position and back end pulse edge position are corrected
according to the amount of offset of the recording mark edge
determined by measuring the reproduced signal.
[0011] It should be noted that the conventional methods described
above are disclosed in, for example, Patent Document 1 given below.
[0012] Patent Document 1: WO 00/57408.
[0013] However, in the conventional methods described above, the
correction table for optical disks that have different recording
characteristics and recording conditions is always determined via a
succession of identical test recording steps. Thus, if, for
example, the thermal interference of an optical disk is small, and
it is not necessary to correct the front end pulse edge position
and the back end pulse edge position for each element of the
correction table in order to obtain sufficient reproduction signal
quality, then by going through what is effectively an unnecessary
test recording step, the result is that there is a problem in that
excessive time is taken for the recording and reproduction
apparatus to come to a state in which it is actually capable of
recording an information signal.
DISCLOSURE OF INVENTION
[0014] In order to solve the foregoing conventional problems, it is
an object of the present invention to provide an optical
information recording method and apparatus that is capable of
effectively determining appropriate recording parameters in a short
time, and accurately recording and reproducing information, when
recording information onto a recording medium having different
information recording conditions and information recording
characteristics.
[0015] In, order to achieve this object, the optical information
recording method of the present invention is an optical information
recording method that records information onto an optical
information recording medium, the method provides an identification
step of identifying an information recording condition or an
information recording characteristic of the optical information
recording media, and a recording pulse correction step of
correcting a recording pulse position, in order to form a recording
mark in a predetermined position, wherein in the recording pulse
correction step, correction accuracy of the recording pulse
position is changed depending on the information recording
conditions or information recording characteristic that were
identified in the identification step.
[0016] The recording process of the mark can be either a mark
position recording process, or a mark edge recording process.
Correction of the recording pulse position can mean either
correction of the edge position of the recording pulse, or it can
mean correction of the position of the recording pulse itself.
Information recording condition means, for example, recording
density or linear recording velocity, or the like, but is not
limited to these. Furthermore, information recording characteristic
means, for example, favorability of recording characteristic, and
more specifically, means for example jitter or bit rate of the
reproduction signal, or repetition of the recording and
reproduction characteristic, however it is not limited to
these.
[0017] According to the foregoing method, since the correction
accuracy of the recording pulse position is changed according to
the information recording condition or information recording
characteristic of the optical information recording medium, it is
capable of effectively determining recording parameters in a short
time, and can accurately record and reproduce information.
[0018] It is also preferable that the optical information recording
method of the present invention, in which an optical information
recording medium that has two or more information layers is used as
the optical information recording medium, further provides, before
the identification step, an information layer specification step of
specifying an information layer on which the information is to be
recorded in the optical information recording medium, wherein in
the identification step, information recording conditions or
information recording characteristics of the information layer that
is specified by the information layer specification step are
identified, and wherein in the recording pulse correction step, the
correction accuracy of a recording pulse position in order to
record the information on the information layer that is specified
in the information layer specification step is differentiated
according to the information recording conditions or information
recording characteristics that are identified in the identification
step.
[0019] According to this method, the correction accuracy of the
recording pulse position is changed according to differences in the
recording conditions or recording characteristics of the
information layers, and thus is capable of effectively determining
appropriate recording parameters in a short time, and accurately
recording and reproducing information.
[0020] Furthermore, in the optical information recording method
according to the present invention, in which an optical information
medium that has a test recording region is used as the optical
information recording medium, it is preferable that the method
further provides a test recording step of recording a pattern for
test recording in the test recording region, using the recording
pulse that was corrected in the recording pulse correction step,
and a correction amount determination step of reproducing the
pattern for test recording from the test recording region, and of
determining the correction amount of the recording pulse position
depending on the reproduction result.
[0021] Accordingly, the correction accuracy of the recording pulse
position for forming the pattern for test recording is changed in
accordance with differences in the recording conditions or
recording characteristics of the optical information recording
medium or information layers, and thus is capable of efficiently
test recording in a short time to determine appropriate recording
parameters, and can accurately record and reproduce
information.
[0022] Furthermore, in the optical information recording method of
the present invention, in which an optical information recording
medium that contains a control track region is used as the optical
information recording medium, the identification step further
comprises an identifier detection step that reproduces information
from the control track region and detects an identifier that
represents the information recording conditions or information
recording characteristics of the optical information recording
medium, from the information that is reproduced, wherein in the
recording pulse correction step, the correction accuracy of the
recording pulse position is differentiated according to the
information recording conditions or information recording
characteristics that are represented by the identifier detected in
the identifier detection step.
[0023] According to this method, by differentiating the correction
accuracy according to the identifier that is recorded on the
optical information recording medium, the time required for
determining the recording parameter can be shortened, and it is
possible to record and reproduce information accurately. It should
be noted that the identifier is not limited to representing the
information recording condition or the information recording
characteristic directly, but also can represent these
indirectly.
[0024] Furthermore, in the optical information recording method of
the present invention, in which an optical information recording
medium that contains a test recording region is used as the optical
information recording medium, it is also preferable that the
identification step further provides a test recording step of
recording a test recording pattern onto the test recording region,
and a characteristic assessment step of reproducing the test
recording pattern from the test recording region and of assessing
the information recording characteristics of the optical
information recording medium by measuring the jitter or the bit
error rate of the reproduction signal, wherein in the recording
pulse correction step, the correction accuracy of the recording
pulse position is differentiated according to the information
recording characteristics that are assessed in the characteristic
assessment step.
[0025] According to this method, even when the optical information
recording medium does not contain an identifier, by differentiating
the correction accuracy in accordance with the results of the test
recording, the as time required for determining the recording
parameter can be shortened, and it is possible to record and
reproduce information accurately. Furthermore, in this case it is
also possible to test record the pattern for test recording at a
low correction accuracy; and increase the correction accuracy by,
for example, increasing the number of table elements only when the
jitter or the bitter error rate of the reproduction signal is
higher than a fixed value, or conversely, it is possible to test
record the pattern for test recording at a high accuracy, and
decrease the correction accuracy by, for example, decreasing the
number of table elements only when the jitter or the bit error rate
of the reproduction signal is lower than a fixed value.
[0026] Furthermore, in order to achieve the object of the present
invention, the optical information recording apparatus of the
present invention is an optical information recording apparatus
that records information onto an optical information recording
medium, that provides identification means for identifying
information recording conditions or information recording
characteristics of the optical information recording medium, and
recording pulse correction means for correcting a recording pulse
position, in order to form a recording mark in a predetermined
position, wherein the recording pulse correction means
differentiates the correction accuracy of the recording pulse
position according to the information recording conditions or the
information recording characteristics that are identified by the
identification means.
[0027] According to this apparatus, the correction accuracy of the
recording pulse position is differentiated according to an
information recording condition or information recording
characteristic of the optical information recording medium, and
thus is capable of efficiently deciding appropriate recording
parameters in a short time and can record and reproduce information
accurately.
[0028] Furthermore, in the optical information recording apparatus
of the present invention, in which an optical information recording
medium that has two or more information layers is used as the
optical information recording medium, it is also possible further
to provide information layer specification means for specifying the
information layer in the optical information recording medium on
which information is to be recorded, wherein the identification
means identifies information recording conditions or information
recording characteristics of the information layer that is
specified by the information layer specification means, and wherein
the recording pulse correction means differentiates the correction
accuracy of the recording pulse position in order to record
information into the information layer that is specified by the
information layer specification means, according to the information
recording conditions or information recording characteristics that
are identified by the identification means.
[0029] According to this configuration, since the correction
accuracy of the recording pulse position is differentiated in
accordance with differences in the recording conditions and
recording characteristics of the information layers, the apparatus
is capable of effectively determining appropriate recording
parameters in a short time, and accurately recording and
reproducing information.
[0030] In the optical information recording apparatus of the
present invention in which an optical information recording medium
that contains a control track region is used as the optical
information recording medium, the identification means further
provides identifier detection means for reproducing information
from the control track region, and for detecting an identifier that
represents the information recording conditions or information
recording characteristics of the optical information recording
medium, from the information that is reproduced, wherein the
recording pulse correction means differentiates the correction
accuracy of the recording pulse position depending on the
information recording conditions or information recording
characteristics that are represented by the identifier detected by
the identifier detection means.
[0031] According to this configuration, by differentiating the
correction accuracy according to the identifier that is recorded on
the optical information recording medium, the time required to
determine the recording parameters can be shortened, and it is
possible to record and reproduce information accurately.
[0032] In the optical information recording apparatus of the
present invention, in which an optical information recording medium
that contains a test recording region is used as the optical
information recording medium, the identification means further
provides test recording means for recording a pattern onto the test
recording region, and characteristic assessment means for
reproducing the test recording pattern from the test recording
region and assessing the information recording characteristics of
the optical information recording medium by measuring the jitter or
the bit error rate of the reproduction signal, wherein the
recording pulse correction means differentiates the correction
accuracy of the recording pulse position according to the
information recording characteristics that are assessed by the
characteristic assessment means.
[0033] According to this configuration, even when the optical
information recording medium does not contain an identifier, by
differentiating the correction accuracy in accordance with the
results of the test recording, the time required for determining
the recording parameter can be shortened, and it is possible to
record and reproduce information accurately. Furthermore, in this
case it is also possible to test record the pattern for test
recording at a low correction accuracy, and increase the correction
accuracy by, for example, increasing the number of table elements
only when the jitter or the bitter error rate of the reproduction
signal is higher than a fixed value, or conversely, it is possible
to test record the pattern for test recording at a high accuracy,
and decrease the correction accuracy by, for example, decreasing
the number of table elements only when the jitter or the bit error
rate of the reproduction signal is lower than a fixed value.
[0034] Furthermore, in order to achieve the object of the present
invention, the optical information recording medium of the present
invention is an optical information recording medium that records
information, wherein the optical information recording medium
contains a plurality of correction tables whose correction accuracy
is mutually different and that correspond to a plurality of
information recording conditions or information recording
characteristics.
[0035] According to this medium, since test recording is performed
by directly changing the correction accuracy of the correction
table according to the result read out from the correction table on
the medium, the time required to determine the recording parameters
can be shortened further, and information can be recorded and
reproduced accurately.
[0036] It is also preferable that the foregoing optical information
recording medium contains an identifier that represents the
correction accuracy of a recording pulse position.
[0037] According to this medium, since it is possible to test
record by changing the correction accuracy of the correction table
according to the identification result of the identifier of the
medium, the time required to determine the recording parameters can
be shortened, and information can be recorded and reproduced
accurately.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 is a block diagram showing a configuration of a
recording and reproduction apparatus according to Embodiment 1 of
the present invention.
[0039] FIG. 2 is a block diagram showing a configuration of a
recording pulse edge correction portion of the recording and
reproduction apparatus according to Embodiment 1.
[0040] FIG. 3 is a perspective view showing a configuration of an
optical information recording medium according to Embodiment 1.
[0041] FIG. 4 is a flowchart that describes the operation of the
recording and reproduction apparatus according to Embodiment 1.
[0042] FIG. 5 is an explanatory diagram showing an example in which
a recording pulse edge position is corrected, in Embodiment 1 and
Embodiment 2 of the present invention.
[0043] FIG. 6 is an explanatory diagram showing an example in which
the recording pulse edge position is corrected in Embodiment 1 and
Embodiment 2.
[0044] FIG. 7 is an explanatory diagram showing an example in which
the recording pulse edge position is corrected in Embodiment 1.
[0045] FIG. 8 is a perspective view showing a configuration of an
optical information recording medium according to Embodiment 2.
[0046] FIG. 9 is a block diagram showing a configuration of a
recording pulse edge correction portion according to Embodiment 3
of the present invention.
[0047] FIG. 10 is a flowchart that describes the operation of a
recording and reproduction apparatus according to Embodiment 3.
[0048] FIG. 11 is an explanatory diagram showing an example in
which a recording pulse edge position is corrected according to
Embodiment 3.
[0049] FIG. 12 is a block diagram showing a recording and
reproduction apparatus according to Embodiment 4 of the present
invention.
[0050] FIG. 13 is a flowchart describing the operation of the
recording and reproduction apparatus according to Embodiment 4.
BEST MODE FOR CARRYING OUT THE INVENTION
[0051] Embodiments of the present invention are described below
with reference to the drawings. The essence of the present
invention is to cause a change in a correction accuracy of the
recording pulse position, in response to various conditions such as
recording characteristics and recording conditions of a disk, in
order to form a recording mark in a predetermined position. As
described below, the correction accuracy includes, for example, the
number of elements in the correction table and the resolution of
the correction table, however it is not limited to this.
Embodiment 1
[0052] In the present embodiment, identifiers representing a
recording density of a disk are assessed by reproducing the disk,
and disks whose recording density is low are recorded using a
correction table that has fewer elements. Thus, there is an
advantage in not going through unnecessary test recording steps. In
the present embodiment, an example is shown in which the number of
elements of a correction table is differentiated for three to types
of recording density, namely a first, a second and a third
recording density. The relationship between the recording densities
is: (first recording density)>(second recording
density)>(third recording density). FIG. 1 and FIG. 2 are block
diagrams showing a conceptual structure of a recording and
reproduction apparatus (optical information recording device) for
realizing Embodiment 1.
[0053] The present recording and reproduction apparatus is an
apparatus that records and reproduces information using an optical
disk (optical information recording medium) 1, and is provided with
a spindle motor 13 for rotating the optical disk 1 and an optical
head 12 that contains a laser light source (not shown) that focuses
laser light onto a desired location of the optical disk 1. The
operation of the entire recording and reproduction apparatus is
controlled by a system control circuit 2. The recording and
reproduction apparatus of the present embodiment further includes a
table registration memory 3 that registers the information in the
correction tablet into each element. It should be noted that
information in the correction table can be registered in the table
registration memory 3 by read-out from the optical disk 1, or it
can be recorded in the table registration memory 3 in advance, such
as when the recording and reproduction apparatus is manufactured.
It should be noted that in FIG. 1, a configuration is illustrated
in which the table registration memory 3 is external to the system
control circuit 2, however it is also possible to have a
configuration in which the table registration memory 3 is provided
inside the system control circuit 2.
[0054] The recording and reproduction apparatus is provided with a
test pattern signal generation circuit 4 as recording data signal
generating means. In order to determine the front end pulse edge
position and the back end pulse edge position, the test pattern
signal generation circuit 4 generates a test pattern signal for
determining the edge position of the recording pulse that has a
specific period, or generates a random pattern signal for
generating a random pattern. Furthermore, the recording and
reproduction apparatus contains a modulation circuit 5 as a
recording data signal generating means that generates a recording
data signal 18, which corresponds to a recorded information
signal.
[0055] The recording and reproduction apparatus further is provided
with a recording pulse generation circuit 6 that generates a
recording pulse signal 19 for driving the laser, and a recording
pulse edge correction circuit 8 that adjusts the front end pulse
edge position and the back end pulse edge position of the recording
pulse signal 19 that is output by the recording pulse generation
circuit 6.
[0056] A laser drive circuit 11 further is provided in order to
modulate an electric current that drives the laser light source in
an optical head 12, in response to the recording pulse signal 22
that is output by the recording pulse edge correction circuit
8.
[0057] Furthermore, the recording and reproduction apparatus
contains a reproduction signal processing circuit 14 that performs
wave form processing of the reproduction signal, such as wave form
equalization or binary conversion that is based on light reflected
from the optical disk 1, as reproduction means for reproducing
information from the optical disk 1, a reproduction signal waveform
measuring circuit 16 that measures the reproduction signal waveform
and detects the timing of the edge of the reproduction signal
waveform, a demodulation circuit 15 that obtains reproduction
information, and an identifier detection circuit 17 that obtains
information about the optical disk 1 from the identifier contained
on the optical disk 1.
[0058] FIG. 2 is a structural diagram showing of the recording
pulse edge correction circuit 8 of FIG. 1 in further detail. The
recording pulse edge correction circuit 8 contains a front pulse
detection circuit 201 that detects a front pulse from the recording
pulse signal, a multi pulse detection circuit 202 that detects a
multi pulse, and a rear end pulse detection circuit 203 that
detects a back end pulse. The recording pulse edge correction
circuit 8 also is provided with selection circuits 204 and 205 for
switching the number of elements in the correction table, first
delay amount setting circuits 206 and 208 that set the amount of
delay of the recording pulse edge for 32 elements, second delay
amount setting circuits 207 and 209 that set the amount of delay of
the recording pulse edge for eight elements, delay circuits 210 and
211 that finally adjust the recording pulse edge and an addition
circuit 212 that adds the signal waveforms of the front pulse, the
multi pulse and the back end pulse.
[0059] FIG. 3 shows a perspective of the optical disk 1 (optical
information recording medium) used in the present embodiment. The
optical disk 1 has a substrate in which grooves or phase pits are
formed in advance, and is fabricated by film forming such films as
a dielectric film, a recording film and a reflecting film (all of
which are omitted from the diagram). Moreover, the substrate (also
called a cover substrate) can be bonded to the disk after film
formation.
[0060] For the substrate, a transparent flat plate made of glass or
resin or the like may be used. A material in which a resin is
dissolved and then coated and dried also can be used.
[0061] As the dielectric film, it is possible to use an oxide such
as SiO.sub.2, SiO, TiO.sub.2, MgO and GeO.sub.2, a nitride such as
Si.sub.3N.sub.4, BN, and AlN, a sulfide such as ZnS and PbS, or a
mixture of these.
[0062] Material whose phase changes between amorphous and
crystalline can be used as the material for the recording film, for
a example SbTe-based, InTe-based, GeTeSn-based, SbSe-based,
TeSeSb-based, SnTeSe-based, InSe-based, TeGeSnO-based,
TeGeSnAu-based, TeGeSnSb-based or TeGeSb-based chalcogen compound.
Materials such as a Te--TeO.sub.2-based, Te--TeO.sub.2--Au-based
and Te--TeO.sub.2--Pd-based oxide can also be used. In the case of
these materials, a phase change occurs between the crystalline
(that is, corresponding to condition a) and amorphous (that is,
corresponding to condition b) states. Furthermore, these also may
be AgZn-based or InSb-based metallic compounds whose phase changes
between the crystalline state (condition a) and the crystalline
state (condition b).
[0063] Metallic materials such as Au, Ag, Al and Cu, or a
multilayer dielectric film that has high reflectance at a
predetermined wavelength can be used as the reflective film.
[0064] As a method for film forming these materials, methods such
as vacuum deposition or sputtering can be used.
[0065] Furthermore, the optical disk 1 contains a center hole 301
for fixing the optical disk 1 to a shaft of the spindle motor 13.
The optical disk 1 also contains a control track region 302, a test
recording region 303 and a data region 304 as its physical
format.
[0066] The control track region 302 is a region for applying
information that relates to the optical disk 1 to the optical
information recording and reproduction apparatus, and it is
principally reproduced when the optical disk 1 is inserted into the
apparatus. The recording structure of the information in the
control track region 302 can be a structure formed in advance as
phase pits in the substrate or it can be a structure recorded as an
optical transformation in the recording layer.
[0067] The control track region 302 is for applying information
that relates to the optical disk 1 with respect to the optical
information recording and reproduction apparatus, and is
principally replayed by the optical information recording and
reproduction apparatus when the disk is inserted. The recording
structure of the information recorded onto the control track region
302 can be a structure formed in advance on the substrate as a
phase pit, and the structure can be recorded as an optical change
in the recording film. Information representing, for example, the
type of disk (such as single recordable, rewritable or rewritable
only in a specific region), the size of the disk, recording
density, recording power, information about the disk manufacturer
and the correction table is recorded in the control track region
302.
[0068] An identifier 305 is recorded in the control track region
302. An identifier that corresponds to the correction accuracy is
recorded as the identifier 305. In this identifier, the disk
manufacturer can, based on a test result and prior to shipping,
record information that represents the number of elements in the
correction table by which sufficiently favorable recording and
reproduction characteristics can be obtained in the optical disk 1.
In the present embodiment, information that represents the
recording density of the disk is used as the identifier. In a
similar manner to the information recorded in the control track
302, the recording structure of the identifier 305 can be in the
form of a phase pit, or it can be in the form of an optical
transformation in the recording film. Furthermore, it is preferable
that the identifier 305 is in the control track region 302, so that
the apparatus can replay that information at the same time as other
disk information when the disk is inserted. However it also can be
in any other region on the optical disk 1.
[0069] The test recording region 303 is a region for test writing,
which allows the optical information recording and reproduction
apparatus to record onto the optical disk 1 at an appropriate
recording power or recording pulse edge position. The data region
304 is the region for recording the actual information signal.
Operation of Embodiment 1
[0070] The following is a description of the operation of the
recording and reproduction device of the present embodiment using
the flowchart in FIG. 4 and operational charts in FIG. 5 to FIG.
7.
[0071] FIG. 4 is a flowchart showing the operation of the present
embodiment. FIG. 5 is a waveform showing the operation according to
the present embodiment when recording at an increased recording
density. The operation to correct the edge positions of the front
end pulse and the back end pulse in the combinations (that is, the
elements of the correction table) of (pre-code length 7T-recording
code length 3T-post-code length 7T), (pre-code length 7T-recording
code length 5T-post-code length 7T) and (pre-code length
3T-recording code length 5T-post-code length 6T) is described in
FIG. 5. Here, T represents the period of the channel clock. In FIG.
5, (a) is a channel clock signal, (b) is a waveform of the
recording data signal 18, (c) is a waveform of the recording pulse
signal 19 and, (d) shows a waveform of the recording pulse signal
22 after pulse edge correction. (e) shows the state of the marks
that are recorded according to the recording pulse signal, numeral
501 represents a track, and numeral 502 represents a recording
mark.
[0072] During test recording, first of all, according to a seek
operation step (step 401 in FIG. 4, abbreviated below as S401), the
optical head 12 seeks out the control track region 302 on the
optical disk 1, based on a command from the system control circuit
2. The identifier that represents the recording density of the
optical disk 1 is recorded in the control track region 302.
Information that indicates the recording power and initial values
of the correction table of the optical disk 1 is also recorded in
the control track region 302. In accordance with the information of
the control track region 302, the system control circuit 2 records
the initial values of the front end pulse edge position and the
back end pulse edge position in the table registration memory 3.
Furthermore, the system control circuit 2 sets these initial values
in the recording pulse edge correction circuit 8. The system
control circuit 2 also sets the recording power of the laser drive
circuit 11 in advance.
[0073] Next, the disk information track is reproduced by an
identifier reproduction step (S402), and the reproduction signal is
transmitted to the identifier detection circuit 17 via the
reproduction signal processing circuit 14 and the demodulation
circuit 15. Then, the information of the identifier is detected by
the identifier detection circuit 17, and is transmitted to the
system control circuit 2. In the recording density decision step
(S403), the system control circuit 2 decides the density at which
the information should be recorded, and transmits a switching
control signal 20 that depends on the recording density that was
determined to the selection circuits 204 and 205 of the recording
pulse edge correction circuit 8.
[0074] The results that were decided in the recording density
decision step (S403) are described below, divided into the cases of
the first to third recording densities.
Operation of Embodiment 1
The Case of the First Recording Density
[0075] If the result of the recording density decision step (S403)
is the first recording density (that is, the recording density is
the highest), then the selecting circuits 204 and 205 are switched
by a selection circuit switching step (S404) to the first delay
amount setting circuits 206 and 208. Accordingly, a state is
assumed in which the edge positions of the recording 21) pulses can
be set in response to a combination of the pre-code length and the
recording code length, and a combination of the recording code
length and the post-code length.
[0076] The operation of the selection circuit switching step (S404)
is described in detail using FIG. 2. The selection circuit 204 is
switched so as to input the recording data signal 18, which comes
from the demodulation circuit 5, into the first delay amount
setting circuits 206 and 208. The delay amount setting circuits 206
and 208 compare a table setting signal 21 that comes from the table
registration memory 3, the combination of the pre-code length and
the recording code length, and the combination of the recording
code length and the post-code length, and set the correction amount
of the recording pulse edge in the delay circuits 210 and 211. The
delay circuit 210 adjusts the forward edge of the front pulse, and
the delay circuit 211 corrects the edge position by adjustment of
the rear edge of the back end pulse.
[0077] In this case, the structure of the correction table in the
table registration memory 3 is as shown in Table 1 and Table 2.
TABLE-US-00001 TABLE 1 Forward edge correction amount Recording
code length 6T and 3T 4T 5T greater Pre-code 3T .DELTA. (3, 3) F
.DELTA. (3, 4) F .DELTA. (3, 5) F .DELTA. (3, 6) F length 4T
.DELTA. (4, 3) F .DELTA. (4, 4) F .DELTA. (4, 5) F .DELTA. (4, 6) F
5T .DELTA. (5, 3) F .DELTA. (5, 4) F .DELTA. (5, 5) F .DELTA. (5,
6) F 6T and .DELTA. (6, 3) F .DELTA. (6, 4) F .DELTA. (6, 5) F
.DELTA. (6, 6) F greater
TABLE-US-00002 TABLE 2 Forward edge correction amount Recording
code length 6T and 3T 4T 5T greater Post-code 3T .DELTA. (3, 3) L
.DELTA. (4, 3) L .DELTA. (5, 3) L .DELTA. (6, 3) L length 4T
.DELTA. (3, 4) L .DELTA. (4, 4) L .DELTA. (5, 4) L .DELTA. (6, 4) L
5T .DELTA. (3, 5) L .DELTA. (4, 5) L .DELTA. (5, 5) L .DELTA. (6,
5) L 6T and .DELTA. (3, 6) L .DELTA. (4, 6) L .DELTA. (5, 6) L
.DELTA. (6, 6) L greater
[0078] These tables represent the correction amount of the front
end edge position and the back end edge position when the shortest
code length is 3T, and the longest code length is 11T.
[0079] Correction tables that use the same correction values for 6T
and above are recorded as information in the control track region
of the optical disk used in the present embodiment. Consequently,
from the combination of the code lengths, there are 32 elements in
the correction tables.
[0080] A test recording and edge position determination subroutine
(S405), is a step that determines the edge positions for the 32
table elements. The details are described in the steps S412 to
S416. That is to say that in a test pattern switching step (S412),
a control signal is transmitted from the system control circuit 2
such that a test pattern for determining the correction amount of a
predetermined table element can be transmitted from the test
pattern signal generation circuit 4.
[0081] By a test pattern recording operation step (S413), the
recording pulse generation circuit 6 converts the recording data
signal 18 (corresponding to (b) in FIG. 5) transmitted from the
test pattern signal generation circuit 4 into the recording pulse
signal 19 (corresponding to (c) in FIG. 5). This detects how many
multiples of the channel clock period T the signal inverted
interval of the recording data signal 18 corresponds to, and
generates a recording pulse sequence of a predetermined number and
a predetermined width at a predetermined timing, which depends on
the recording code length.
[0082] And, in the recording pulse edge correction circuit 8, the
front end pulse edge position and the back end pulse edge position
of the recording pulse sequence are adjusted to the set values.
That is to say, as shown in (d) of FIG. 5, the leading edge of the
front end pulse of (pre-code length 7T-recording code length 3T) is
adjusted by .DELTA..sub.(6, 3) F, the trailing edge of the back end
pulse of (recording code length 3T-post-code length 7T) is adjusted
by .DELTA..sub.(3, 6) L, the leading edge of the front end pulse of
(pre-code length 7T-recording code length 5T) is adjusted by
.DELTA..sub.(3, 5) F, . . . and thus, the pulse edges are adjusted
in accordance with the values of the elements of the correction
tables of Table 1 and Table 2.
[0083] The laser drive circuit 11 carries out test recording on the
track in the test region 303 by modulating the driving current of
the laser according to the recording pulse signal that passed
through the recording pulse edge correction circuit 8, as shown in
(d) of FIG. 5. As shown in (e) of FIG. 5, after recording, the
edges of the recording mark 502 are formed on the track 501 at
normalized positions that correspond to integer multiples of the
channel clock.
[0084] After the test pattern signal is recorded, the track is
reproduced by the optical head 12 in a reproduction operation step
(S414). The reproduction signal circuit 14 carries out equalization
of the waveform, and binary conversion of the reproduction signal.
And, the reproduction signal waveform measurement circuit 16 slices
the binary signal, and measures the reproduction signal inverted
interval by a signal timing measurement step (S415). An edge
position determination step (S416) requests the difference between
the reproduction signal inverted interval and the signal inverted
interval of the test pattern signal (that is, the offset amount of
the edge mark), and fixes the amount that compensates that
difference as the correction amount in that table element. It
should be noted that the steps S413 to S416, which change the
correction amount, can be performed repeatedly until the difference
between the reproduction signal inverted interval and the signal
inverted interval of the test pattern signal is a minimum.
[0085] The system signal circuit 2 registers the edge position that
is being set in the table registration memory 3 in the system
control circuit 2 as edge position information, and concludes the
test recording with respect to this combination table element.
Moreover, in a table element determination step (S406), the system
control circuit 2 determines whether S405 has been repeated or not
for all the elements of the combination table, and completes the
setting and registration of the edge position of all 32 table
elements shown in Table 1 and Table 2, after which it completes the
test recording and starts recording the actual information
signal.
Operation of Embodiment 1
The Case of the Second Recording Density
[0086] On the other hand, when the determination result is the
second recording density (that is, lower than the first recording
density), the operation is as described below. By a switching
selection circuit step (S408), the selection circuit 204 switches
so as to input the recording data signal 18 that comes from the
modulation circuit 5 into second delay amount setting circuits 207
and 209. Thus, the selection circuit 204 is in a condition to set
the edge position of the recording pulse, with consideration only
to the recording code length.
[0087] In the second delay amount setting circuits 207 and 209, the
table setting signal 21 from the table registration memory 3 is
compared to the recording code length, and the correction amount of
the recording pulse edge is set for the delay circuits 210 and 211.
Similarly as in the case of the first recording density, the edge
position is corrected in the delay circuits 211 and 212 by
adjusting, respectively, the leading edge of the front pulse, and
the trailing edge of the rear pulse.
[0088] In this case, the structure of the correction table in the
table registration memory 3 is as given in Table 3 and Table 4.
From the combination of code lengths, the number of elements in the
correction table is 8.
TABLE-US-00003 TABLE 3 Recording code length Forward edge
correction amount 3T .DELTA. 3F 4T .DELTA. 4F 5T .DELTA. 5F 6T and
greater .DELTA. 6F
TABLE-US-00004 TABLE 4 Recording code length Forward edge
correction amount 3T .DELTA. 3F 4T .DELTA. 4F 5T .DELTA. 5F 6T and
greater .DELTA. 6F
[0089] Furthermore, FIG. 6 is a waveform showing the operation of
recording the disk at the second recording density, according to
the present embodiment. FIG. 6 shows recording of the same
recording data signal as in FIG. 5, however the operation to
correct the edge position of the recording pulse is different. That
is to say, correction of the edge position is performed with
respect to a recording code length of 3T and a recording code
length of 5T.
[0090] The test recording and edge position determination
subroutine (S405) is the step in which the edge position is
determined with respect to the 8 table elements, and is similar to
that of the step for high density recording described above. It
differs in that in the second recording pulse edge correction
circuit 9, the front end pulse edge position and the back end pulse
edge position of the recording pulse sequence are adjusted to set
values. That is to say, as shown by (d) in FIG. 5, the leading edge
of the front end pulse of the recording code length 3T is adjusted
by .DELTA.3F, the trailing edge of the back end pulse of the
recording code length 3T is adjusted by .DELTA.3L, the leading edge
of the front end pulse of the recording code length 5T is adjusted
by .DELTA.5F, . . . and thus, the pulse edge is adjusted according
to the values of the elements of the correction tables of Table 3
and Table 4. Consequently, a table element determination step
(S409) determines whether or not setting and registration of the
edge position of the eight table elements shown in Table 3 and
Table 4 is complete.
Operation of Embodiment 1
The Case of the Third Recording Density
[0091] Moreover, when the determination result is the third
recording density (that is, lower than the second recording
density), the selection circuits 204 and 205 transmit the signals
to the direct delay circuits 210 and 211 respectively, without
carrying out the test recording.
[0092] FIG. 7 is a waveform showing the operation in the case of
the third recording density. FIG. 7 shows the recording of the same
recording data signal as in FIG. 5 and FIG. 6, however it differs
in the correction of the edge position of the recording pulse. The
waveforms of (c) and (d) in FIG. 7 are the same, and there is no
adjustment step of the edge position of the recording pulse.
[0093] The method as described above is used for the following
reasons. The effect of thermal interference between recording marks
that are adjacent in the tracking direction, when the disk is
recorded at the second recording density is less than when recorded
at the first recording density, so fluctuations in the edge
position of the recording marks caused by differences in the
pre-code length or differences in the post-code length are small
enough to ignore. Consequently, the recording pulse edges are
corrected only with respect to the recording code length, and
sufficient reproduction signal quality can be obtained even using
the correction table containing eight elements. Moreover, with the
third recording density, fluctuations of the edge position of the
recording mark caused by differences in the recording code length
are small enough to ignore. Consequently, sufficient reproduction
signal quality can be obtained even without adjusting the edge
position of the recording pulse with respect to the recording code
length, the pre-code length and the post-code length.
[0094] Accordingly, there are no unnecessary test recording steps
when recording low density disks. Thus, it is possible to reduce
the time taken for test recording.
Comparative Experiment of Embodiment 1
[0095] The following is an explanation in order to confirm the
effect of Embodiment 1, a comparative experiment (working example)
in which the recording density is differentiated. A polycarbonate
resin having a diameter of 120 mm and a thickness of 0.6 mm is used
as the substrate of the optical disk 1. Unevenly-shaped phase pits
are pre-formatted in advance as a control track region on this
substrate. Information that represents the recording density of the
disk is recorded as an identifier in the control track region
[0096] In order to handle recording and reproduction at different
recording densities, an identifier that represents two different
types of recording density is recorded on the optical disk 1. Here,
information showing that the disk is capable of being recorded and
reproduced at two recording densities, namely at a first recording
density with a minimum mark length of 0.35 .mu.m and a second
recording density with a minimum mark length of 0.55 .mu.m, is
recorded.
[0097] A guide groove is formed in a sector of the data region of
the resin substrate. Furthermore, phase pits that represent address
information are formed between the sectors. The pitch of the guide
grooves is 1.4 .mu.m. A protective film, a recording film, a
protective film and a reflective film are four layers that are film
formed on the substrate by sputtering, and a protective substrate
is bonded onto that. ZnS--SiO.sub.2 is used as the protective film,
GeSbTe is used as the recording film, and Al is used as the
reflective film.
[0098] The disk 1 is rotated at a linear velocity of 8.2 m/s by the
spindle, motor 13, and laser light of wavelength 650 nm is focused
by an objective lens whose numerical aperture (NA) is 0.6.
[0099] The power of the laser light for recording and reproduction
is Pp=10.5 mW, Pb=4 mW and Pr=1 mW. The modulation process of the
recording information uses (8-16) pulse width modulation. The
frequency of the channel clock was changed to handle the recording
density.
[0100] For comparison, the case in which the number of elements in
the correction table is 32 is shown in Table 1 and Table 2, and the
case when the number of elements is eight is shown in Table 3 or
Table 4. The correction resolution of the elements is 0.5 ns. It
should be noted that correction resolution means the minimum unit
of increase or decrease of the correction amount. Specific examples
of the correction tables Table 1 to Table 4 according to this
condition, for the case in which the minimum mark length is 0.55
.mu.m, are shown in Table 5 to Table 8, and for the case in which
the minimum mark length is 0.35 .mu.m, are shown in Table 9 to
Table 12.
TABLE-US-00005 TABLE 5 Forward edge correction amount (ns)
Recording code length 6T and 3T 4T 5T greater Pre-code 3T -3 -1 -1
-1 length 4T -3 -1 -1 -1 5T -2 -1 -1 0 6T and -2 -1 -1 0
greater
TABLE-US-00006 TABLE 6 Forward edge correction amount (ns)
Recording code length 6T and 3T 4T 5T greater Post-code 3T 0 2 2 3
length 4T 0 2 2 3 5T 1 2 2 3 6T and 1 2 3 3 greater
TABLE-US-00007 TABLE 7 Recording code length Forward edge
correction amount (ns) 3T -2 4T -1 5T -1 6T and greater 0
TABLE-US-00008 TABLE 8 Recording code length Forward edge
correction amount (ns) 3T 1 4T 2 5T 3 6T and greater 3
TABLE-US-00009 TABLE 9 Forward edge correction amount (ns)
Recording code length 6T and 3T 4T 5T greater Pre-code 3T -5 -3 -2
-2 length 4T -4 -2 -2 -2 5T -3 -2 -1 -1 6T and -2 -1 -1 0
greater
TABLE-US-00010 TABLE 10 Forward edge correction amount (ns)
Recording code length 6T and 3T 4T 5T greater Post-code 3T -1 1 1 2
length 4T 0 1 2 2 5T 0 2 2 3 6T and 1 2 3 3 greater
TABLE-US-00011 TABLE 11 Recording code length Forward edge
correction amount (ns) 3T -3 4T -2 5T -1 6T and greater -1
TABLE-US-00012 TABLE 12 Recording code length Forward edge
correction amount (ns) 3T 0 4T 2 5T 2 6T and greater 3
[0101] Test recording was performed using the Conditions described
above, after which a random signal was recorded 10 times, and
reproduction signal jitter was measured by a time interval
analyzer. The results of measuring the jitter for each information
layer and correction table element number are shown in Table
13.
TABLE-US-00013 TABLE 13 Number of elements 8 32 Minimum mark 0.35
.mu.m 11.0% 8.9% length 0.55 .mu.m 6.8% 6.5%
[0102] From Table 13, when the minimum mark length is 0.55 .mu.m,
either 8 elements or 32 elements give a jitter in the 6% range. As
opposed to this, when the minimum mark length is 0.35 .mu.m, 32
elements give a jitter in the 8% range, however it is found that in
the case of eight elements, jitter deteriorates to 11.0%. This is
because when the minimum mark length is 0.35 .mu.M, the space
between the recording marks is shorter and the period of the
channel clock also decreases. Consequently, since changes in
thermal interference with respect to changes in the pre-code length
and the post-code length are relatively large, it appears that the
desired jitter is unobtainable without using the correction table
arranged by combining the pre-code lengths or post-code lengths
with the recording code length. Consequently, when the minimum mark
length is 0.55 .mu.m, from the stand point of reducing the test
recording time, it is preferable to switch so that the number of
elements in the correction table is 8, and from the stand point of
obtaining a favorable jitter value, it is preferable that the
number of elements in the correction table is switched to 32 when
the minimum mark length is 0.35 .mu.m.
[0103] Thus, in the present embodiment, since the number of
elements in the table is reduced and the test recording is
performed when recording at a low recording density according to
the identification result of the identifier of the disk, it is
possible to achieve a special effect in that the amount of time
required for test recording is reduced.
[0104] It should be noted that in the embodiment described above,
the number of elements in the correction table also can be
differentiated by the linear velocity at which the disk is
recorded. For example, when recording is performed using the same
channel clock frequency, the recording density is lower at the
higher linear velocity, and since heat is less likely to accumulate
on the recording film during recording, the edge position of the
recording mark is less susceptible to the influence of thermal
interference. Consequently, even without using the correction table
that is combined from the pre-code length or the post-code length
and the recording code length, a favorable jitter can be obtained.
Thus, the number of elements in the correction table can be
reduced, and it is possible to reduce the time that is required for
the test recording.
[0105] Furthermore, in the embodiment described above, the
correction accuracy was switched by actually changing the number of
elements in the table, according to the identification result of
the identifier, however the present embodiment can also have the
structure in which the correction accuracy is changed by keeping
the number of elements in the table as is, and setting the values
of the predetermined table elements to be equivalent. For example,
in the tables of Table 1 and Table 2, by setting the values of the
table elements equivalent such that:
.DELTA. ( 3 , 3 ) F = .DELTA. ( 4 , 3 ) F = .DELTA. ( 5 , 3 ) F =
.DELTA. ( 6 , 3 ) F .DELTA. ( 3 , 4 ) F = .DELTA. ( 4 , 4 ) F =
.DELTA. ( 5 , 4 ) F = .DELTA. ( 6 , 4 ) F .DELTA. ( 6 , 3 ) L =
.DELTA. ( 6 , 4 ) L = .DELTA. ( 6 , 5 ) L = .DELTA. ( 6 , 6 ) F
##EQU00001##
then the same effect of the correction table of Table 3 and Table 4
can be obtained.
[0106] Furthermore, the adjustment step of the recording pulse edge
position was not performed in the case of the third recording
density in the operation of the embodiment described above, however
it is also possible of uniformly adjust the recording pulse edge
position without consideration to the code length. At this time,
the correction table contains a total of two elements, as shown in
Table 14 and Table 15. In this case, it is possible to obtain more
favorable recording and reproduction characteristics at the third
recording density.
TABLE-US-00014 TABLE 14 Forward edge correction amount .DELTA.F
TABLE-US-00015 TABLE 15 Rear edge correction amount .DELTA.L
Embodiment 2
[0107] Even in a structure other than that described in Embodiment
1, and even when the structure is such that the number of elements
of the correction tables differs when there is a difference in the
recording characteristics of the disk, it is possible to obtain a
similar special effect. That is to say, even when the recording
density is the same, if the disk itself has recording
characteristics with low thermal interference, then even if the
number of elements in the correction table is reduced, the
fluctuations in the edge position of the recording mark are small
enough to be ignored. Consequently, it is possible to reduce the
time that is required for test recording.
[0108] An embodiment of an optical disk that has two recording
layers is described below, as the most typical example of the case
in which the recording characteristics differ, regarding an
embodiment in which the number of elements of the correction table
are made to differ to handle the information layers of multi-layer
media.
Structure and Operation of Embodiment 2
[0109] FIG. 8 shows a perspective view of an optical disk 1
(optical information recording medium) that is used in the present
embodiment. In order to describe an internal portion of the optical
disk, FIG. 8 shows the optical disk 1 with one-part cut out. The
optical disk is viewed from the side on which the laser light for
recording and reproducing the optical disk is incident, and is made
of a first information layer 801, which is positioned at the front,
and a second information layer 802, which is positioned at the
back. An identifier 305 is present independently on the information
layers, and an identifier that corresponds to the correction
accuracy is recorded.
[0110] Excluding the point that the identifier detection circuit
detects the identifier on each information layer, the configuration
and operation of the recording and reproduction apparatus of the
present embodiment is the same as that of Embodiment 1.
Comparative Experiment of Embodiment 2
[0111] The comparative experiment (working example) of Embodiment 2
is described below. The optical disk is fabricated as given below.
As the substrate, polycarbonate resin having a diameter of 120 mm
and a thickness of 1.1 mm is used, and a spiral-shaped groove
having a width of 0.25 .mu.M, a pitch of 0.32 .mu.m and a depth of
20 nm is formed on its upper surface.
[0112] Furthermore, unevenly-shaped phase pits are pre-formatted in
advance as a control track region on this substrate.
[0113] The second information layer 802 is formed on top of the
surface of the substrate and is film formed in the order:
reflective layer Ag alloy; dielectric layer ZnS--SiO.sub.2;
recording layer GeSbTe; dielectric layer ZnS--SiO.sub.2.
[0114] Next, a center layer, which transcribes a groove shape that
is similar to that on the substrate, is formed. Moreover, an AlN
dielectric layer, a ZnS--SiO.sub.2 dielectric layer, a GeSbTe
recording layer and a ZnS--SiO.sub.2 dielectric layer are film
formed in this sequence as the first information layer 801. No
reflective layer is used with the front information layer so as to
increase its transmittance.
[0115] Finally, a sheet made from polycarbonate is bonded by an
ultraviolet hardening resin. The total thickness of the adhesive
and the sheet is 0.1 mm.
[0116] Furthermore, in the control track region of the information
layers, information that represents the correction accuracy of the
information layers is recorded in the form of a phase pit structure
as the identifier 305. The identifier information that is recorded
differs between that of the front information layer and the back
information layer.
[0117] The recording and reproduction experiment was performed
using this disk. Rotating the disk at a linear velocity of 5 m/s,
either of the information layers of the disk is irradiated by
semiconductor laser light of wavelength of 405 nm that is stopped
down through an objective lens, which has a numerical aperture (NA)
of 0.85.
[0118] (8-16) modulation is used as the modulation code during
recording and reproduction, and the signal after modulation is
multi-pulse processed to cause the semiconductor laser to emit
light. A mark length of 3T was 0.20 .mu.m.
[0119] For comparison, the case in which the number of elements in
the correction table is 32 is shown in Table 1 and Table 2, and the
case when the number is 8 is shown in Table 3 or Table 4. The
correction resolution of the elements was 0.5 ns.
[0120] Test recording was performed under these conditions, after
which a random signal was recorded 10 times, and the jitter of the
reproduction signal measured by a time interval analyzer. The
result of the jitter measurement with respect to the information
layers and number of elements in the correction table is shown in
Table 16.
TABLE-US-00016 TABLE 16 Number of elements 8 32 Information Front
9.8% 8.7% layer Back 8.3% 8.0%
[0121] From Table 16, in the information layer at the back, a
favorable jitter in the 8% range can be obtained using either the
correction table that has 32 elements or eight elements. This is
because there is no necessity for the back information layer of the
multi-layer media to have a configuration that has a high
transmittance, unlike in the front information layer in which it is
necessary to ensure that the laser light reaches the back layer.
Therefore, because optical absorption is high, it is possible to
constitute a multi-layer film using a thick reflecting film of a
high thermal conductivity, and the heat developed during recording
tends to be dispersed easily from the recording film to the
reflecting film. Consequently, since the effect of thermal
interference in the tracking direction is small, and the change in
thermal interference relative to the change in pre-code length or
post-code length is small, it seems that the jitter does not change
very much even using a table that corrects the edge position of the
recording pulse only with respect to the recording code length. In
this case, since the number of test recording process steps can be
reduced when the number of elements is eight, it is favorable from
the view point of shortening the time required for test
recording.
[0122] On the other hand, although the jitter of the front
information layer is in the 8% range when the number of elements is
32, it has been found that this deteriorates to 9.8% with only
eight elements. Since the front information layer is not provided
with a reflective layer that has high thermal conductivity, the
heat developed during recording tends to be dispersed within the
recording layer. Consequently, the change in thermal interference
relative to the change in pre-code length and post-code length is
large, so it seems that the desired jitter cannot be obtained
without using a correction table that is a combination of pre-code
length or post-code length and recording code length. In this case,
it is preferable that the correction table has 32 elements from the
stand point of obtaining a favorable jitter value.
[0123] In the present working example as described above, since the
number of elements in the correction table is reduced before test
recording according to the result of identifying the identifier
that represents the information layer, it is possible to shorten
the time that is required for test recording. It should be noted
that the number of information layers is not limited to two, and
the same result can be obtained with three or more layers, provided
the number of elements is matched to the recording characteristics
of the layers.
[0124] Furthermore, the present working example is not limited to
multi-layer disks, and even with mono-layer disks, the number of
elements can differ in accordance with differences in the recording
characteristics of each disk.
Embodiment 3
[0125] The present embodiment is an embodiment in which a disk
whose recording conditions are identified by reproducing an
identifier on the disk, and whose recording characteristics when,
for example, the linear velocity of recording onto the disk is low,
are such that even if the edge of the recording pulse is greatly
changed then the effect on the edge position of the recording mark
is small, and there are no unnecessary test recording steps to pass
through by reducing the resolution of the elements of the
correction table to record.
Configuration and Operation of the Embodiment 3
[0126] A structural overview of the recording and reproduction
apparatus (optical information recording apparatus) for realizing
Embodiment 3 is the same as that in FIG. 1. FIG. 9 is a diagram
showing the detailed configuration of the recording pulse edge
correction circuit 8 in FIG. 1. FIG. 10 is a flowchart used to
describe the operation of the present embodiment, and FIG. 11 is a
waveform diagram of the recording pulse signal that describes the
present embodiment.
[0127] The configuration of FIG. 9 differs from Embodiment 1 in
that the destination of the transmission of the front pulse signal
from a front pulse detection circuit 901 is switched between either
a first delay circuit 908 or a second delay circuit 909 by a
selection circuit 906. Furthermore, the destination of the
transmission of the back end pulse signal from a back end pulse
detection circuit 903 is switched between either a first delay
circuit 910 or a second delay circuit 911 by a selection circuit
907. Accordingly, the number of elements in the tables is the same,
but the operation is realized by switching the set resolution of
the elements in the correction table based on the disk recording
characteristics. The operation is described in greater detail using
FIG. 10 and FIG. 11.
[0128] The recording operation in FIG. 10 is as described below.
The recording data signal 18 from the modulation circuit is
transmitted to delay amount setting circuits 904 and 905; Pulse
signals from the front pulse detection circuit 901 and back end
pulse detection circuit 903 are transmitted to the selection
circuits 906 and 907 respectively. In the delay setting circuits
904 and 905, the table setting signal 21 that comes from the table
registration memory 3 is compared to a combination of the pre-code
length and the post-code length, or a combination of the recording
code length and the post-code length, so as to set the correction
amount of the recording pulse edge for the first delay circuits 908
and 910 and the second delay circuits 909 and 911. In the delay
circuits 908 to 911, the edge position is corrected by adjusting
the relevant recording pulse edges. At this time, for the structure
of the correction table in the table registration memory 3 as shown
in Table 1 and Table 2, the table has the same number of components
whichever selection is made by the selection circuits.
[0129] The operation of the first delay circuits 908 and 910
differs from that of the second delay circuits 909 and 911 in the
set resolution of the delay amount. FIGS. 11(a) and (b) show an
example of an adjustment of the recording pulse edge by the first
delay circuits 908 and 910, and FIGS. 11(c) and (d) show an example
of an adjustment of the recording pulse edge by the second delay
circuits 909 and 911. Whereas the set resolution (minimum setting
unit) of the delay circuit in the first delay circuit is r.sub.1,
that of the second delay circuit is r.sub.2, and this is
characterized by being smaller than that of the first delay
circuit.
[0130] Furthermore, an identifier that corresponds to the set
resolution is recorded in the control track region of the optical
disk 1. For example, based on the results of an examination by the
manufacturer of the disk, information is recorded that shows a set
resolution at which sufficiently favorable recording and
reproduction characteristics can be obtained when the edge of the
recording pulse is changed, according to the size of the effect on
the edge position of the recording mark.
[0131] FIG. 10 shows a series of test recording operations. They
differ from Embodiment 1 in the following points. In a decision
step S1003, the set resolution at which the disk that is recorded
can obtain favorable recording and reproduction characteristics is
identified according to the reproduction result in an identifier
reproduction step S1002. That is to say, in a disk that has
recording characteristics whereby the edge position of the
recording mark changes greatly when the edge of the recording pulse
changes, there is an increase in the set resolution at which
favorable recording and reproduction characteristics can be
obtained.
[0132] In cases in which disks or recording conditions have
recording characteristics in which the edge position of the
recording marks change greatly, the selection circuits 906 and 907
are switched to the second delay circuits 909 and 911 in a
selection step S1007, and the edge position of the recording pulse
is adjusted and determined at the relatively fine setting
resolution r.sub.2 (corresponding to steps S1015 to S1019).
[0133] Conversely, in the case in which the change in the edge
position of the recording mark of disks or recording conditions is
small, the selection circuit 907 is switched to the first delay
circuit 908 and 910 in the selection step S1004, and the edge
position of the recording pulse is adjusted and determined at the
relatively coarse setting resolution r.sub.1 (corresponding to
steps S1010 to S1014).
[0134] By this operation, on the disk, or in the condition in which
the change in the edge position of the recording mark is small,
even if the steps S1011 to S1014 are performed repeatedly while
changing the correction amount until the difference in the
reproduction signal inverted interval and the signal inverted
interval of the test pattern signal is a minimum, since the setting
resolution is coarse, the edge position of the recording pulse can
be determined with a minimum of repetitions. Additionally,
fluctuations of the edge position of the recording mark can be made
small enough to ignore. Consequently, it is possible to shorten the
time necessary for test recording.
Comparative Experiment of Embodiment 3
[0135] In order to confirm the effect of the present embodiment, a
comparative experiment (working example) in which the linear
velocity was changed is described next as the recording condition.
The optical disk 1 is fabricated by the same method as in
Embodiment 1.
[0136] Information that represents the linear velocity at which the
disk is recorded is recorded as an identifier in the control track
region. In order to handle recording and reproduction at different
linear velocities, two types of identifiers, which represent
different linear velocities, are recorded. Information that the
disk is capable of recording and reproducing at linear velocities
of 8.2 m/s and 12.3 m/s is recorded here.
[0137] The disk 1 is rotated by the spindle motor 13 at the two
different linear velocities of 8.2 m/s and 12.3 m/s, and a laser
light of wavelength 650 nm is focused on the disk by an objective
lens whose numerical aperture is 0.6.
[0138] The power of the laser light is Pp=11 mW, Pb=4.5 mW and Pr=1
mW when recording and reproduction at the linear velocity of 8.2
m/s. When the linear velocity is 12.3 m/s, Pp=13 mW, Pb=5 mW and
Pr=1 mW. The modulation process of the recording information used
(8-16) pulse width modulation. By changing the channel clock to
handle the linear velocities, the minimum mark length is 0.4 .mu.m
at either linear velocity.
[0139] This comparative experiment uses the correction table shown
in Table 1 and Table 2. The same 32 element table is used with
either of the two linear velocities.
[0140] For comparison, the correction resolution of the table
elements was set at the two types, namely 0.5 ns and 1.0 nm with
respect to the linear velocities. That is to say that the element
values were set to only 0.5 ns or only 1.0 ns in a setting
step.
[0141] Test recording was performed using the above conditions,
after which a random signal was recorded 10 times, and the jitter
of the reproduction signal measured by a time interval analyzer.
The result of the jitter measurement with respect to the linear
velocities and correction resolution is shown in Table 17.
TABLE-US-00017 TABLE 17 Correction resolution 0.5 ns 1.0 Linear 8.2
m/s 8.2% 8.4% velocity 12.3 m/s 8.6% 10.3%
[0142] From Table 17, a favorable jitter in the 8% range can be
obtained at either resolution of 0.5 ns or 1.0 ns for the linear
velocity of 8.2 m/s. Since the linear velocity is slow, it appears
that changes in the edge position of the recording pulse have only
a small effect on the mark edge position, and thus there is not a
lot of change in jitter at either resolution. In this case, it is
preferable from the stand point of reducing the time that is
required for the test recording, because the number of adjustment
points of the pulse edge can be reduced when test recording at the
correction resolution of 1.0 ns.
[0143] On the other hand, at the linear velocity of 12.3 m/s, the
jitter is in the 8% range when the correction resolution is 0.5 ns,
however it is found that this deteriorates to 10.3% when at 1.0 ns.
This is because the effect of the change of the edge position of
the recording pulse is large when the linear velocity is fast, and
it is felt that the jitter worsens because the setting step is too
coarse at 1.0 ns. In this case, from the stand point of obtaining a
favorable jitter value, it is preferable that the correction
resolution is 0.5 ns.
[0144] Therefore, in recording conditions in which the change in
the edge position of the recording mark is small, it is possible to
say that by lowering the resolution based on the identification
result of the identifier, test recording is effective for
accurately recording and reproducing information in a short test
recording time.
[0145] In this manner, since the test recording in the present
embodiment is performed by lowering the resolution of the elements
of the correction table, the time necessary for test recording can
be shortened when recording under conditions in which changes in
the edge position of the recording pulse have a small effect on the
mark edge position.
[0146] That is to say, the present embodiment is one in which the
correction resolution is changed by switching the delay circuits.
However it is also possible to use the same delay circuits and
change the resolution from r.sub.2 to r.sub.1 by culling the
setting steps, as shown in the waveform (e) in FIG. 11.
[0147] Furthermore, in the present embodiment, the number of
elements in the table is the same, without consideration of the
identification result of the identification step, however it is
also possible to change the number of elements depending on the
recording density or recording characteristics of the disk. That is
to say, it is also possible to use the combinations in the first or
second embodiments.
[0148] Furthermore, in the case whereby recording conditions differ
within the same disk, test recording can be performed at a minimum
testing time corresponding to each recording condition, by
recording a plurality of identifier information that represent a
correction accuracy corresponding to the conditions. For example,
as shown in Table 18, it is only necessary that the recording
power, the number of table elements and the resolution that
corresponds to a plurality of linear velocities are recorded onto
the control track region.
TABLE-US-00018 TABLE 18 Linear velocity v.sub.1 v.sub.2 Recording
power P.sub.p1, P.sub.b1 P.sub.p2, P.sub.b2 Number of Table
elements n.sub.1 n.sub.2 Resolution r.sub.1 r.sub.2
[0149] Moreover, if recording at different conditions within the
same disk, instead of recording the number of table elements and
the resolution as values, then it is possible to use a media to
record a plurality of correction tables themselves, which contain
the number of table elements and resolution. In this case, there is
no necessity to provide special identifiers that represent the
number of elements or the resolution, and the information that is
recorded in the control track region can be simplified.
Furthermore, the test recording can be performed by changing the
correction accuracy of the correction table directly from the
result of the read out from the correction table on the medium, and
thus it is possible to further shorten the time required for test
recording and information can be accurately recorded and
reproduced, without needing to read out the special identifiers
that represent the number of elements or the resolution.
[0150] Furthermore, when recording a plurality of correction tables
of differing correction accuracies that correspond to a plurality
of different linear velocities onto the medium, it is also possible
to provide a correction table for high recording densities, which
has high accuracy. In this case, since the correction accuracy can
be reduced before test recording according to the correction table
of low correction accuracy, when at a low linear velocity at which
the change in the edge position of the recording mark is small, it
is effective in accurately recording and reproducing information in
a short test recording time.
[0151] Similarly, when recording a plurality of correction tables
of differing correction accuracies that correspond to a plurality
of different linear velocities, it is also possible to provide a
correction table that has high accuracy for high recording
densities. In this case, at low recording densities, since the
correction accuracy can be reduced before test recording according
to the correction table of low correction accuracy, it is effective
in accurately recording and reproducing information in a short test
recording time, in a similar manner to that described above.
Embodiment 4
[0152] The present embodiment is an embodiment in which BER is
measured by recording and reproducing a random pattern on the disk,
whereby the number of elements in the correction table is increased
and test recording performed only when BER is higher than a fixed
value, and in which there is no unnecessary test recording step for
disks whose recording density is low, or for disks whose thermal
interference is small.
Configuration and Operation of the Embodiment 4
[0153] FIG. 12 is a block diagram showing a structural overview of
a recording and reproduction apparatus. (optical information
recording apparatus) for realizing Embodiment 4. The configuration
of the recording pulse edge correction circuit 8 in the present
embodiment can be the same as that used in FIG. 2. FIG. 12 differs
from the configuration of Embodiment 1 (FIG. 1) in the provision of
a BER measurement circuit 1201 instead of the identifier detection
circuit 17.
[0154] FIG. 13 is a flowchart that describes the operation of test
recording in the present embodiment. The operation is described in
more detail below using FIG. 12, FIG. 2 and FIG. 13.
[0155] After a seek operation (S1301) of the present embodiment,
the selection circuits 204 and 205 are switched to the second delay
amount setting circuits 207 and 209 by a selection circuit
switching step S1302. Thus, the procedure is in a state in which
the recording pulse edge position can be set according to the
recording code length.
[0156] In this case, the structure of the correction table in the
table registration memory 3 is as Table 3 and Table 4. From the
combination of code lengths, the number of elements in the
correction table is eight.
[0157] In a similar manner to Embodiment 1, test recording and
measurement of the reproduction signal wave form is performed in
order to determine the elements in the correction table (S1302 to
S1303). After determining the values of the eight elements of the
correction table, a random signal is transmitted from the test
pattern signal generation circuit 4 and recording of the disk is
performed (S1306). In addition to waveform equalization and binary
conversion of the reproduction signal from the disk in the
reproduction signal processing circuit 14, the information signal
is demodulated (S1307) in the demodulation circuit 15. The
demodulated information signal and the information signal of the
random pattern that was generated in the test pattern signal
generation circuit 4 are compared in the BER measurement circuit
1201, and the BER (bit error rate) of the reproduction signal is
measured (S1308).
[0158] Then, the bit error rate and a BER prescribed value are
compared in the system control circuit 2 by a BER assessment step,
and the result of the assessment is obtained. Here, the BER
prescribed value indicates a value at which the bit error rate of
the information that is reproduced is capable of use. This value is
fixed with consideration given to the recording margin of the
recording and reproduction apparatus and the optical disk.
[0159] If the measured value is less than the standard value, then
the test recording ends. Thus, with disks whose recording density
is low, or with disks whose thermal interference is small, if
fluctuation of the edge position of the recording mark caused by
differences in the pre-code length or by differences in the
post-code length is small enough to ignore, then it is not
necessary to pass through an unnecessary test recording step.
Therefore, it is possible to reduce the time taken for test
recording even when using disks that have no identifier.
[0160] If the bit error rate that was measured is higher than the
BER standard value, then the procedure passes through the following
steps. The selection circuits 204 and 205 are switched to the first
delay amount setting circuits 206 and 208 by a selection circuit
switching step S1310. By this, the procedure is in a state in which
it can set the edge position of the recording pulse depending on
the combination of the pre-code length and the recording code
length, and the combination of the recording code length and the
post-code length.
[0161] In this case, the structure of the correction table in the
table registration memory 3 is as given in Table 1 and Table 2.
From the combination of the code lengths, the number of elements in
the correction table is 32.
[0162] Similarly to Embodiment 1, test recording and measurement of
the reproduction signal waveform are performed in order to
determine the elements of the correction table. The test recording
ends after determining the correction values of all the table
elements.
[0163] In this manner, in the present embodiment, recording the
random pattern signal after the test recording with fewer table
elements, the test recording is repeated with a greater number of
table elements only when the BER of the reproduction signal is
higher than the fixed value, and thus the procedure does not pass
through unnecessary test recording steps when using disks whose BER
recording density is low, or disks whose thermal interference is
small. Due to this, it is possible to shorten the time required for
test recording even when the disk has no identifier.
[0164] It should be noted that in the present embodiment, the
decision to end the procedure was based on the size of the BER
value. However it is also possible to use the jitter value
instead.
[0165] Furthermore, in the present embodiment, the number of
elements were increased to perform the test recording only when the
BER was higher than a fixed value, however a similar effect can
also be obtained even in a method in which the number of elements
are decreased to perform the test recording only when the BER is
lower than a fixed value. That is, the test recording time is
shortened. Furthermore, in the present embodiment, the number of
elements in the correction table were changed, however a similar
effect can also be obtained using a structure in which the
resolution of the elements is changed. Moreover, a combination of
changes to the number of elements and changes in the resolution is
also possible.
[0166] Furthermore, the number of elements used in the correction
tables of the Embodiment 1 to Embodiment 4 is independent of the
code lengths, however since the effect of thermal interference
decreases with longer code lengths, it is also possible to use a
same number of elements for code lengths over a certain length (for
example 6T or more).
[0167] Furthermore, in the foregoing embodiments, the front edge
position of the front end pulse and the rear edge position of the
back end pulse were changed in the recording pulse edge correction
circuit (in these cases, the width of the front end pulse and the
width of the back end pulse change respectively), however it is
also possible that the circuit adjusts the edge as position by
changing the actual position of the front end pulse and the back
end pulse. Furthermore, it is also possible to have a circuit that
switches between the method for changing the actual position of the
front end pulse and the back end pulse, and the method for changing
the edge position, depending on the disk recording characteristics
and recording density.
[0168] Furthermore, in the foregoing embodiments, the correction
accuracy was changed according to the number of elements in the
correction table, or the value of the resolution of the correction
table, however it is possible to use any other variable as long as
it is a variable that affects the accuracy of the edge-position of
the recording pulse, such as a delay amount error of the delay
circuit.
[0169] Furthermore, in the foregoing embodiments, the information
that represents the correction accuracy was recorded on the medium
as an identifier, however it is also possible to record onto that
medium the actual correction table itself that contains the
correction accuracy necessary for that medium. In this case, since
the test recording is performed by changing the correction accuracy
of the correction table directly from the result of the read-out of
the correction table on the medium, the time required for test
recording can be shortened further, and information can be recorded
and reproduced accurately.
[0170] Moreover, provided the optical disk is a medium in which the
optical characteristics of the recording mark and non-mark portion
are different, such as a phase change material, photomagnetic
material or pigment material, then any of the methods described
above can be applied.
[0171] Furthermore, in the foregoing embodiments, recording has
been illustrated using the mark edge recording method, however the
present invention also can be applied to the recording by the mark
position recording method.
[0172] Furthermore, such items as the modulation method, pulse
lengths and period of the test pattern signal are not limited to
those shown in the foregoing embodiments, and it goes without
saying that it is possible to set appropriate values depending on
the recording conditions and medium.
INDUSTRIAL APPLICABILITY
[0173] As described above, according to the present invention,
since the correction accuracy of the recording pulse position is
changed depending on an information recording condition or an
information recording characteristic of an optical information
recording medium, when recording information on recording media
whose information recording conditions or information recording
characteristics differs, it is possible to provide an optical
information recording method and apparatus that can effectively
determine appropriate recording parameters in a short time and
which are capable of accurately recording and reproducing
information.
* * * * *