US 7,126,897 B2Granted

Multi-level information recording apparatus, multi-level information recording method, multi-level information recording medium and multi-level information recording-reproducing apparatus

AssigneeRicoh Company, Ltd.

InventorsKohji Takeuchi, Akihiko Shimizu

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Abstract

A multi-level information recording-reproducing apparatus can accurately determine multi-level information even if recording density is increased. A multi-level information recording-reproducing apparatus radiates a laser beam to an information recording medium by switching a radiation energy level of the laser beam in a multi-level fashion and records a recorded mark in the information recording medium. The multi-level information recording-reproducing apparatus reproduces a multi-level data sequence recorded as a test pattern in the information recording medium, sets a reproduction signal level of a recorded mark based on an immediately-before cell located immediately before a cell to be reproduced, and corrects the radiation energy level of the laser beam so that the reproduction signal level can have a separate distribution from a distribution of another reproduction signal level.

Claims4

Dependent claims

A multi-level information recording method for radiating a laser beam in an information recording medium and recording multi-level data in said information recording medium wherein a radiation energy level of said laser beam is controlled in accordance with said multi-level data, comprising the steps of:

recording a known multi-level data sequence by using said laser beam of a radiation energy level corresponding to a combination of multi-level data and obtaining a reproduction result for said combination;
performing a waveform equalizing process for said reproduction result;
computing a target signal level for each combination of said multi-level data by using a waveform equalizing coefficient;
computing a difference between said target signal level and a value obtained by performing said waveform equalizing process;
determining a correction amount of said laser beam for each combination of said multi-level data in accordance with said waveform equalizing coefficient and said difference;
and
determining a correction amount of said laser beam corresponding to said combination of the multi-level data, and
wherein said waveform equalizing process is performed based on a formula (1), and said correction amount of the laser beam is determined based on a formula (2),
EQ
′
⁡
(
i
)
=
s
′
⁡
(
i
)
+
∑
j
=
-
h
h
⁢
⁢
Cj
⁢
{
s
′
⁡
(
i
)
-
s
′
⁡
(
i
+
j
)
}
,
(
1
)
and
Δ
⁢
⁢
E
⁡
(
i
)
=
β
·
Δ
⁡
(
i
)
⁢
(
1
+
∑
j
=
-
h
h
⁢
⁢
Cj
)
(
1
+
2
⁢
∑
j
=
-
h
h
⁢
⁢

Cj

)
·
ⅆ
s
′
⁡
(
i
)
ⅆ
E
⁡
(
i
)
,
(
2
)
where the number of taps of a waveform equalizer is 2h+1, EQ′(i) is a signal level after said waveform equalizing process, s′(i) is a reproduction signal level of i-th multi-level data, Cj is a waveform equalizing coefficient (j=−h, −(h−i), . . . , −1, 0, 1, . . . , h−1, h), β is a correction coefficient, Δ(i) is a difference between a target signal level and a result of the waveform equalizing process, and ds′(i)/dE(i) is a gradient of a curve of said reproduction signal level s′(i) to a laser beam energy E(i).

117 more elements

recording a known multi-level data sequence by using said laser beam of a radiation energy level corresponding to a combination of multi-level data and obtaining a reproduction result for said combination;
performing a waveform equalizing process for said reproduction result;
computing a target signal level for each combination of said multi-level data by using a waveform equalizing coefficient;
computing a difference between said target signal level and a value obtained by performing said waveform equalizing process;
determining a correction amount of said laser beam for each combination of said multi-level data in accordance with said waveform equalizing coefficient and said difference;
and
determining a correction amount of said laser beam corresponding to said combination of the multi-level data, and
wherein said waveform equalizing process is performed based on a formula (3), and said correction amount of the laser beam is determined based on a formula (4),
EQ
′
⁡
(
i
)
=
s
′
⁡
(
i
)
+
∑
j
=
-
h
h
⁢
⁢
Cj
⁢
{
s
′
⁡
(
i
)
-
s
′
⁡
(
i
+
j
)
}
,
(
3
)
and
Δ
⁢
⁢
E
⁡
(
i
)
=
β
[
1
+
∑
j
=
-
h
h
⁢
⁢
Cj
⁢
{
Δ
⁡
(
i
)
+
Δ
⁡
(
i
+
j
)
}
]
(
1
+
2
⁢
∑
j
=
-
h
h
⁢
⁢

Cj

)
·
ⅆ
s
′
⁡
(
i
)
ⅆ
E
⁡
(
i
)
,
(
4
)
where the number of taps of a waveform equalizer is 2h+1, EQ′(i) is a signal level after said waveform equalizing process, s′(i) is a reproduction signal level of ith multi-level data, Cj is a waveform equalizing coefficient (j=−h, −(h−1), . . . , −1, 0, 1, . . . , h−1, h), β is a correction coefficient, Δ(i) is a difference between a target signal level and a result of the waveform equalizing process, and ds′(i)/dE(i) is a gradient of a curve of said reproduction signal level s′(i) to a laser beam energy E(i).

126 more elements

Dependencies are inferred from the claim text.

Facts

Application: 10/386,532Filed 13 Mar 2003
Priority: JP 2002-07359918 Mar 2002
Published: US 2004/0027958 A112 Feb 2004
Granted: 24 Oct 2006
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

G11B 7/24088
Pits: for storing more than two values, i.e. multi-valued recording for data or prepits
G11B 7/00456
Recording: recording strategies, e.g. pulse sequences
G11B 7/261
Apparatus or processes specially adapted for the manufacture of record carriers: preparing a master, e.g. exposing photoresist, electroforming
G11B 7/005
Recording, reproducing or erasing methods; Read, write or erase circuits therefor: reproducing