Write power adjustment method and information recording method
View Patent ↗In write power adjustment for an optical disc having a plurality of information storage layers, data of trial writing is varied by the influence of layers other than a target layer. It is difficult, therefore, to determine optimal write power. A modulation M[m] is obtained from a reproduction signal amplitude of a signal subjected to the trial writing performed with use of write powers Pw[m] (m being an integer) of a plurality of kinds. At least an optimum write power intercept Pint_opt is determined by fitting a relation between the Pw[m] and the M[m] by a modulation characteristic formula M=Masy×(1−(Pint−Pasy)/(Pw−Pasy)) having an asymptotic modulation Masy, a write power intercept Pint, and an asymptotic write power Pasy as parameters. Approximation accuracy by the fitting and/or quality of the trial writing signal are evaluated with use of at least the M[m], the modulation characteristic formula, and the Pint_opt. An optimum write power Pw_opt is calculated by performing a specified operation at least with use of the Pint_opt.
1. An evaluation method, comprising the steps of:
fitting a relation between write powers Pw[m] (m being an integer) of a plurality of kinds and a modulation M[m] obtained from a reproduction signal amplitude of a signal subjected to trial writing by a modulation characteristic formula M=Masy×(1−(Pint−Pasy)/(Pw−Pasy)) having an asymptotic modulation Masy, a write power intercept Pint, and an asymptotic write power Pasy as parameters to determine Masy_opt as an optimal value of the asymptotic modulation, Pint_opt as a optimal value of the write power intercept, and Pasy_opt as an optimal value of the asymptotic write power so as to minimize S:
S
=
∑
m
{
M
[
m
]
×
(
Pw
[
m
]
-
Pasy
)
-
Masy
×
(
Pw
[
m
]
-
Pint
)
}
2
;
calculating a square of a correlation coefficient r between M (Pw[m]) obtained by substituting the Pw[m] into the modulation characteristic formula using the Masy_opt, the Pint_opt, and the Pasy_opt and the modulation M[m] obtained from the trial writing; and
evaluating whether or not the relation between the write powers Pw[m] and the modulation M[m] is appropriate for write power adjustment with use of the square of a correlation coefficient r and a predetermined value.
2. The evaluation method according to claim 1 , wherein the correlation coefficient r is calculated by the following expression:
r
2
=
{
n
∑
m
=
1
n
{
M
[
m
]
×
M
(
Pw
[
m
]
)
}
-
(
∑
m
=
1
n
M
[
m
]
)
×
(
∑
m
=
1
n
M
(
Pw
[
m
]
)
)
}
2
(
n
∑
m
=
1
n
(
M
[
m
]
)
2
-
(
∑
m
=
1
n
M
[
m
]
)
2
)
(
n
∑
m
=
1
n
{
M
(
Pw
[
m
]
)
}
2
-
(
∑
m
=
1
n
M
(
Pw
[
m
]
)
)
2
)
.
3. An information recording method, comprising the steps of:
fitting a relation between write powers Pw[m] (m being an integer) of a plurality of kinds and a modulation M[m] obtained from a reproduction signal amplitude of a signal subjected to trial writing by a modulation characteristic formula M=Masy×(1−(Pint−Pasy)/(Pw−Pasy)) having an asymptotic modulation Masy, a write power intercept Pint, and an asymptotic write power Pasy as parameters to determine Masy_opt as an optimal value of the asymptotic modulation, Pint_opt as an optimal value of the write power intercept, and Pasy_opt as an optimal value of the asymptotic write power so as to minimize S:
S
=
∑
m
{
M
[
m
]
×
(
Pw
[
m
]
-
Pasy
)
-
Masy
×
(
Pw
[
m
]
-
Pint
)
}
2
;
calculating a square of a correlation coefficient r between M (Pw[m]) obtained by substituting the Pw[m] into the modulation characteristic formula using the Masy_opt, the Pint_opt, and the Pasy_opt and the modulation M[m] obtained from the trial writing;
evaluating whether or not the relation between the write powers Pw[m] and the modulation M[m] is appropriate for write power adjustment with use of the square of a correlation coefficient r and a predetermined value; and
recording information with write waveforms having the write powers after the evaluation.