Title of Invention

OPTICAL DISK, RECORDING METHOD, RECORDING MEDIUM, AND OPTICAL DISK UNIT

Abstract A method of recording information using a laser on a multilayer optical disk (20) having a plurality of recording layers is disclosed. The optical disk unit (20) comprises a spindle motor (22) to rotate an optical disk (15); an optical pickup unit (23); a seek motor (21), a laser control circuit (24); an encoder (25), a drive control circuit (26), a reproduced signal processing circuit (28), a buffer RAM (34), a buffer manager (37), an interface (38), a flash memory (39),a CPU (40),and a RAM (41). The plurality of recording layers comprise a first recording layer and a second recording layer adjacent the first recording layer. The first recording layer is provided with a first test writing area to be used for calibration of write power, and the second recording layer is provided with a second test writing area to be used for calibration of write power. The disk is arranged so that a first region of the first test writing area is superposed with a second region of the second test writing area when considered in the direction in which the laser is arranged to irradiate. The method comprises, if the second region of the second test writing area is unrecorded, recording data in the second region of the second test writing area, thereby converting the second region of the second test writing area into a recorded state; and once the second region of the second test writing area has been converted into a recorded state, performing test writing in the first region of the first test writing area.
Full Text DESCRIPTION
OPTICAL DISK, RECORDING METHOD, RECORDING MEDIUM,
AND OPTICAL DISK UNIT
TECHNICAL FIELD
The present invention relates generally to optical
disks, recording methods, recording media, and optical disk
units, and more particularly to an optical disk having
multiple layers on which information is rewritable
(information rewritable layers) , a method of recording
information on the optical disk, an optical disk unit capable
of recording information on the optical disk, and a recording
medium on which a program employed in the optical disk unit is
recorded.
BACKGROUND ART
In recent years, with progress in digital technology
and an improvement in data compression techniques, optical
disks such as DVDs (digital versatile disks) have drawn
attention as media for recording information such as music,
movies, photographs, and computer software (hereinafter also
referred to as "contents"). As optical disks have become
lower in price, optical disk units employing optical disks as
media for recording information have become widely used.

In the optical disk unit, information is recorded on
an optical disk by forming a minute laser light spot on the
recording surface of the optical disk on which a spiral track
or concentric tracks are formed, and information is reproduced
from the optical disk based on reflected light from the
recording surface. An optical pickup unit is provided in the
optical disk unit in order to emit laser light onto the
recording surface of the optical disk and receive reflected
light from the recording surface.
In general, the optical pickup unit includes an
optical system, a photodetector, and a lens drive unit. The
optical system includes an objective lens. The optical system
guides a light beam emitted from a light source to the
recording surface of the optical disk, and guides a returning
light beam reflected from the recording surface to a
predetermined light-receiving position. The photodetector is
disposed at the light-receiving position. The lens drive unit
drives the objective lens in the directions of its optical
axis (hereinafter also referred to as "focus directions") and
in the directions perpendicular to the tangential directions
of the tracks (hereinafter also referred to as "tracking
directions"). The photodetector outputs a signal including
not only the reproduced information of data recorded on the
recording surface, but also information necessary to control
the position of the objective lens (servo information).

Information is recorded on the optical disk based on
the length of each of a mark and a space different in
reflectivity from each other, and their combination.
For example, when a mark is formed in rewritable
optical disks such as DVD-RW (DVD-rewritable) and DVD+RW
(DVD+rewritable) disks including a special alloy in their
recording layers, the special alloy is rapidly cooled after
being heated to a first temperature so as to be in an
amorphous state. On the other hand, when a space is formed,
the special alloy is gradually cooled after being heated to a
second temperature (lower than the first temperature) so as to
be in a crystalline state. As a result, the reflectivity is
lower in the mark than in the space. Such control of special
alloy temperature is performed by controlling the light
emission power of laser light. At the time of forming marks
in particular, the pulse shape of light emission power is set
based on a rule (method) concerning the pulse shape of light
emission power, etc., called a write strategy, in order to
reduce variation in heat distribution due to preceding and
subsequent marks and spaces.
In the optical disk unit, at the time of recording,
an optimum write (recording) power is obtained by performing
test writing in a preset test writing area called PCA (Power
Calibration Area) before writing information in order that a
mark and a space of target length are formed at a target

position on the optical disk (see, for example, ECMA-337 Data
Interchange on 120 mm and 80 mm Optical Disk using +RW Format
- Capacity: 4.7 and 1.46 Gbytes per Side, December 2003).
This operation is called OPC (Optimum Power Control).
The contents tend to increase in quantity year by
year, so that a further increase in the recording capacity of
optical disks is expected. Providing multiple recording
layers is considered as means for increasing the recording
capacity of optical disks, and lots of efforts are being made
to develop optical disks having multiple recording layers
(hereinafter also referred to as "multilayer disks") and
optical disk units to access the multilayer disks. It is also
important to obtain an appropriate write power in the
multilayer disks, and a variety of proposals have been made
regarding OPC (see, for example, Japanese Laid-Open Patent
Application No. 2004-310995).
However, in rewritable multilayer disks, which are
not yet commercially available, for example, higher recording
rates may cause variations in recording quality even when
recording is performed with an optimum write power obtained by
OPC.
DISCLOSURE OF THE INVENTION
Accordingly, it is a general object of the present
invention to provide an optical disk in which the above-

described disadvantages are eliminated.
A more specific object of the present invention is
to provide an optical disk with multiple rewritable recording
layers on which disk recording can be stably performed.
Another more specific object of the present
invention is to provide a recording method and an optical disk
unit that make it possible to perform recording on the optical
disk with stable recording quality.
Yet another more specific object of the present
invention is to provide a recording medium on which recorded
is a program to be executed by the controlling computer of the
optical disk unit, the program making it possible to perform
recording on the optical disk with stable recording quality.
According to a first aspect of the invention, there
is provided a method of recording information using a laser on
a multilayer optical disk having a plurality of recording
layers, the plurality of recording layers including a first
recording layer and a second recording layer, the second
recording layer being a recording layer adjacent the first
recording layer, the first recording layer having a first test
writing area to be used for calibration of write power and the
second recording layer having a second test writing area to be
used for calibration of write power, wherein a first region of
the first test writing area is superposed with a second region
of the second test writing area when considered in the

direction in which the laser is arranged to irradiate, the
method comprising:
if the second region of the second test writing area
is unrecorded, recording data in the second region of the
second test writing area, thereby converting the second region
of the second test writing area into a recorded state; once
the second region of the second test writing area has been
converted into a recorded state, performing test writing in
the first region of the first test writing area.
The second recording layer can be the next recording
layer with respect to the first recording layer in the
direction in which the laser is arranged to irradiate.
In addition, the optical disk can include a third
recording layer, the third recording layer being the next
recording layer with respect to the first recording layer in
the opposite direction to that in which the laser is arranged
to irradiate, the third recording layer having a third test
writing area to be used for calibration of write power,
wherein a third region of the third test writing area is
superposed with the first region of the first test writing
area when considered in the direction in which the laser is
arranged to irradiate. In such embodiments, the method
comprises: if the third region of the third test writing area
is unrecorded, recording data in the third region of the third
test writing area, thereby converting the third region of the

third test writing area into a recorded state; once the third
region of the third test writing area has been converted into
a recorded state, performing said test writing in the first
region of the first test writing area.
In some embodiments, before performing the test
writing in the first region of the first test writing area, if
the first region of the first test writing area is unrecorded,
the method comprises: recording data in the first region of
the first test writing area, thereby converting the first
region of the first test writing area into a recorded state;
and then clearing the first region of the first test writing
area.
In some embodiments, before performing the test
writing in the first region of the first test writing area,
the method comprises clearing the first region of the first
test writing area.
The clearing of the first region of the first test
writing area can comprise performing an erasure operation to
make the first region unrecorded.
For the first region of the first test writing area,
or the second region of the second test writing area, or the
third region of the third test writing area, the respective
step of recording data in the region thereby converting the
region into a recorded state comprises performing an operation
to make the region logically zero.

According to a second aspect of the invention, there
is provided an apparatus arranged to record information to a
multilayer optical disk having a plurality of recording layers
using a laser, the plurality of recording layers including a
first recording layer and a second recording layer, the second
recording layer being a recording layer adjacent the first
recording layer, the first recording layer having a first test
writing area to be used for calibration of write power and the
second recording layer having a second test writing area to be
used for calibration of write power, wherein a first region of
the first test writing area is superposed with a second region
of the second test writing area when considered in the
direction in which the laser is arranged to irradiate,
wherein: if the second region of the second test writing area
is unrecorded, the apparatus is arranged to record data in the
second region of the second test writing area, thereby
converting the second region of the second test writing area
into a recorded state; once the second region of the second
test writing area has been converted into a recorded state,
the apparatus is arranged to perform test writing in the first
region of the first test writing area.
The second recording layer can be the next recording
layer with respect to the first recording layer in the
direction in which the laser is arranged to irradiate.
In addition, the optical disk can include a third

recording layer, the third recording layer being the next
recording layer with respect to the first recording layer in
the opposite direction to that in which the laser is arranged
to irradiate, the third recording layer having a third test
writing area to be used for calibration of write power,
wherein a third region of the third test writing area is
superposed with the first region of the first test writing
area when considered in the direction in which the laser is
arranged to irradiate, wherein: if the third region of the
third test writing area is unrecorded, the apparatus is
arranged to record data in the third region of the third test
writing area, thereby converting the third region of the third
test writing area into a recorded state; once the third region
of the third test writing area has been converted into a
recorded state, the apparatus is arranged to perform said test
writing in the first region of the first test writing area.
In some embodiments, before performing the test
writing in the first region of the first test writing area, if
the first region of the first test writing area is unrecorded,
the apparatus is arranged to: record data in the first region
of the first test writing area, thereby converting the first
region of the first test writing area into a recorded state;
and then to clear the first region of the first test writing
area.
In some embodiments, before performing the test

writing in the first region of the first test writing area,
the apparatus is arranged to clear the first region of the
first test writing area.
The clearing of the first region of the first test
writing area can comprise performing an erasure operation to
make the first region unrecorded.
For the first region of the first test writing area,
or the second region of the second test writing area, or the
third region of the third test writing area, the apparatus is
arranged such that the respective recording of data in the
region thereby converting the region into a recorded state
comprises performing an operation to make the region logically
zero.
One or more of the above objects of the present
invention are achieved by a single-sided multilayer optical
disk including a plurality of information rewritable recording
layers each having a spiral track or concentric tracks formed
thereon, wherein a test writing area to be used for
calibration of write power is provided in each of the
recording layers, and the test writing areas of adjacent two
of the recording layers are superposed at least partly on each
other in a view from a direction of incidence of a light beam.
An optical disk according to one embodiment of the
present invention allows an optical disk unit in which the
optical disk is set to perform positioning swiftly at the time

of performing test writing in one recording layer after
another, and accordingly, to calibrate write power in each
recording layer in a short period of time. As a result, it is
possible to perform stable recording even if the optical disk
has multiple rewritable recording layers.
One or more of the above objects of the present
invention are also achieved by a method of recording
information on a single-sided multilayer optical disk
according to one embodiment of the present invention, the
method including the step of, before performing test writing
in a first one of the test writing areas of the recording
layers in the optical disk except the recording layer closest
to a light beam entrance surface, recording data in a second
one of the test writing areas adjacent to the first one of the
test writing areas on a light beam entrance surface side
thereof, thereby converting the second one of the test writing
areas into a recorded state.
According to one embodiment of the present invention,
before performing test writing in a first one of the test
writing areas of recording layers in an optical disk except
the recording layer closest to a light beam entrance surface,
a second one of the test writing areas adjacent to the first
one of the test writing areas on its light beam entrance
surface side is converted into a recorded state. Accordingly,
it is possible to determine an optimum write power matching a

situation where user data is actually recorded, so that it is
possible to perform recording with stable recording quality.
One or more of the above objects of the present
invention are also achieved by a method of recording
information on a single-sided multilayer optical disk
according to one embodiment of the present invention, the
method including the step of, before performing test writing
in a first one of the test writing areas of the recording
layers in the optical disk except the recording layer most
remote from a light beam entrance surface, recording data in a
second one of the test writing areas adjacent to the first one
of the test writing areas on a side thereof opposite from the
light beam entrance surface, thereby converting the second one
of the test writing areas into a recorded state.
According to one embodiment of the present invention,
before performing test writing in a first one of the test
writing areas of recording layers in an optical disk except
the recording layer most remote from a light beam entrance
surface, a second one of the test writing areas adjacent to
the first one of the test writing areas on the opposite side
from the light beam entrance surface is converted into a
recorded state. Accordingly, it is possible to suppress the
adverse effect of so-called interlayer crosstalk, so that it
is possible to perform recording with stable recording quality.
One or more of the above objects of the present

invention are also achieved by a computer-readable recording
medium on which recorded is a program for causing a computer
to execute any of the above-described methods of recording
information on a single-sided multilayer optical disk
according to one embodiment of the present invention.
According to one embodiment of the present invention,
when a program is loaded into a predetermined memory, and its
start address is set in a program counter, the controlling
computer of an optical disk unit, before performing test
writing in a first one of the test writing areas of recording
layers in an optical disk except the recording layer closest
to a light beam entrance surface, changes a second one of the
test writing areas adjacent to the first one of the test
writing areas on its light beam entrance surface side into a
recorded state. Alternatively, the controlling computer,
before performing test writing in a first one of the test
writing areas of the recording layers except the recording
layer most remote from a light beam entrance surface, may
change a second one of the test writing areas adjacent to the
first one of the test writing areas on the opposite side from
the light beam entrance surface into a recorded state. Thus,
it is possible to cause the controlling computer of the
optical disk unit to execute any of the above-described
recording methods of recording information on the optical disk,
so that it is possible to perform recording with stable

recording quality.
One or more of the above objects of the present
invention are also achieved by an optical disk unit capable of
recording information on a single-sided multilayer optical
disk according to one embodiment of the present invention, the
optical disk unit including a memory, an optical pickup unit
configured to emit a light beam onto the optical disk, a
controlling computer, and a processing unit, wherein the
memory stores a program for causing the controlling computer
to execute any of the above-described methods of recording
information on the optical disk; the controlling computer
obtains an optimum recording condition for the optical disk in
accordance with the program stored in the memory; and the
processor unit records the information on the optical disk
with the optimum recording condition through the optical
pickup unit.
According to one embodiment of the present invention,
the controlling computer of an optical disk unit executes a
program, recorded in a memory, for causing the controlling
computer to execute any of the above-described methods of
recording the information on the optical disk, so that an
optimum recording condition is obtained. A processing unit
records the information on the optical disk with the optimum
recording condition through an optical pickup unit. In this
case, the controlling computer obtains an optimum recording

condition whichever recording layer of the optical disk is to
have information recorded therein. As a result, it is
possible to perform recording on the optical disk with stable
recording quality.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Other objects, features and advantages of the
present invention will become more apparent from the following
detailed description when read in conjunction with the
accompanying drawings, in which:
FIG. 1 is a block diagram showing an optical disk
unit according to an embodiment of the present invention;
FIG. 2 is a diagram for illustrating a structure of
an optical disk according to the embodiment of the present
invention;
FIGS. 3A and 3B are diagrams for illustrating a
write strategy according to the embodiment of the present
invention;
FIGS. 4A and 4B are additional diagrams for
illustrating the write strategy according to the embodiment of
the present invention;
FIG. 5 is another diagram for illustrating the write
strategy according to the embodiment of the present invention;
FIG. 6 is a tabie showing parameters of the write
strategy according to the embodiment of the present invention;

FIG. 7 is a diagram for illustrating a disk layout
of the optical disk of FIG. 2 according to the embodiment of
the present invention;
FIG. 3 is a diagram for illustrating PCA in the
optical disk of FIG. 2 according to the embodiment of the
present invention;
FIG. 9 is another diagram for illustrating the PCA
in the optical disk of FIG. 2 according to the embodiment of
the present invention;
FIG. 10 is a diagram for illustrating an optical
pickup unit of the optical disk unit of FIG. 1 according to
the embodiment of the present invention;
FIG. 11 is a flowchart for illustrating a recording
operation according to the embodiment of the present
invention;
FIG. 12 is a graph for illustrating the effect of
the recording state of a layer LO on the degree of modulation
of a layer L1 according to the embodiment of the present
invention;
FIG. 13 is a graph for illustrating the effect of
the recording state of the layer LO on the jitter of the layer
L1 according to the embodiment of the present invention; and
FIG. 14 is a graph for illustrating the effect of
the write power of the layer LO on the degree of modulation of
the layer L1 according to the embodiment of the present invention.

Accordingly, the present invention provides a method of recording information using a laser on
a multilayer optical disk having a plurality of recording layers, the plurality of recording layers
comprising a first recording layer and a second recording layer, the second recording layer being a
recording layer adjacent the first recording layer, the first recording layer having a first test writing area
to be used for calibration of write power and the second recording layer having a second test writing
area to be used for calibration of write power, wherein a first region of the first test writing area is
superposed with a second region of the second test writing area when considered in the direction in
which the laser is arranged to irradiate, the method comprising: if the first region of the first test writing
area is unrecorded, recording data in the first region of the first test writing area, thereby converting the
first region of the first test writing area into a recorded state; if the second region of the second test
writing area is unrecorded, recording data in the second region of the second test writing area, thereby
converting the second region of the second test writing area into a recorded state; clearing the first
region of the first test writing area before performing the test writing in the first region of the first test
writing area; and performing the test writing in the first region of the first test writing area.
The present invention also provides an apparatus arranged to record information to a multilayer
optical disk having a plurality of recording layers using a laser, the plurality of recording layers
comprising a first recording layer and a second recording layer, the second recording layer being a
recording layer adjacent the first recording layer, the first recording layer having a first test writing area
to be used for calibration of write power and the second recording layer having a second test writing
area to be used for calibration of write power, wherein a first region of the first test writing area is
superposed with a second region of the second test writing area when considered in the direction in
which the laser is arranged to irradiate, wherein if the first region of the first test writing area is
unrecorded, the apparatus is arranged to record data in the first region of the first test writing area,
thereby converting the first region of the first test writing area into a recorded state; if the second region
of the second test writing area is unrecorded, the apparatus is arranged to record data in the second
region of the second test writing area, thereby converting the second region of the second test writing
area into a recorded state; the apparatus is arranged to clear the first region of the first test writing area
before performing test writing in the first region of the first test writing area; and the apparatus is
arranged to perform the test writing in the first region of the first test writing area.

The present invention still further provides a single-sided multilayer optical disk, comprising: a
plurality of information rewritable recording layers each having a spiral track or concentric tracks
formed thereon, wherein a test writing area to be used for calibration of write power is provided in each
of the recording layers; and the test writing areas of adjacent two of the recording layers are superposed
at least partly on each other in a view from a direction of incidence of a light beam.

BEST MODE FOR CARRYING OPT THE INVENTION
A description is given below, with reference to the
accompanying drawings, of an embodiment of the present
invention.
FIG. 1 is a block diagram showing an optical disk
unit 20 according to the embodiment of the present invention.
The optical disk unit 20 includes a spindle motor 22
to rotate an optical disk 15 according to the embodiment of
the- present invention; an optical pickup unit 23; a seek motor
21 to drive the optical pickup unit 23 in the radial
directions of the optical disk 15; a laser control circuit 24,
an encoder 25, a drive control circuit 26, a reproduced signal
processing circuit 28, a buffer RAM 34, a buffer manager 37,
an interface 38, a flash memory 39, a CPU 40, and a RAM 41.
The arrows in FIG. 1 represent typical information and signal
flows, and do not represent all the interconnections of the
blocks. Further, in this embodiment, the optical disk unit 20
supports multilayer disks.
[Structure of Optical Disk 15]
A light beam is made incident on or enters the
optical disk 15 through one side thereof. By way of example,
the optical disk 15 includes two rewritable recording layers.
That is, the optical disk 15 is a single-sided double-layer

disk. By way of example, as shown in FIG. 2, the optical disk
15 includes a substrate la, a layer L0, an adhesive layer 7, a
layer L1, and a substrate lb in this order of closeness to the
light beam entrance surface. The incident light beam reaches
the layer L1 through the substrate 1a, the layer L0, and the
adhesive layer 7. Accordingly, the substrate 1a, the layer L0,
and the adhesive layer 7 should have a predetermined
transparency in the wavelength range of the incident light
beam.
The layer L0 has a lower protection layer 2a, a
recording layer 3a, an upper protection layer 4a, a semi-
transparent layer 5, and an intermediate layer 6 in this order
of closeness to the light beam entrance surface. Further, the
layer L1 has a lower protection layer 2b, a recording layer 3b,
an upper protection layer 4b, and a reflective layer 8 in this
order of closeness to the light beam entrance surface. By way
of example, the optical disk 15 is a disk of 120 mm in
diameter. Further, by way of example, the optical disk 15 is
an information recording medium belonging to the DVD system.
The substrate la is 0.565 mm in thickness. By way
of example, polycarbonate is employed as the material of the
substrate la.
The lower protection layer 2a has a film thickness
of 200 nm. By way of example, a mixture of ZnS and SiO2 is
employed as the material of the lower protection layer 2a.

Here, by way of example, the mixture ratio of ZnS to SiO2 is
80 : 20 (molar ratio).
The recording layer 3a has a film thickness of 8 nm.
By way of example, an In-Sb-Ge alloy is employed as the
material of the recording layer 3a.
The upper protection layer 4a has a film thickness
of 20 nm. By way of example, SiO2 is employed as the material
of the upper protection layer 4a.
The lower protection layer 2a and the upper
protection layer 4a are provided in order to prevent thermal
deformation and diffusion of the recording layer 3a.
The semi-transparent layer 5 has a film thickness of
8 nm. By way of example, Cu is employed as the material of
the semi-transparent layer 5.
The intermediate layer 6 has a film thickness of 150
nm. By way of example, ITO is employed as the material of the
intermediate layer 6. The intermediate layer 6 has the
function of diffusing heat around the recording layer 3a with
efficiency and of correcting light absorptance.
That is, the layer L0 is 386 nm in thickness.
The adhesive layer 7 is 50 µm in thickness. By way
of example, an acryl-based UV-curable adhesive agent is
employed as the material of the adhesive layer 7.
The lower protection layer 2b has a film thickness
of 100 nm. By way of example, the same ZnS-SiO2 mixture as

that of the lower protection layer 2a is employed as the
material of the lower protection layer 2b.
The recording layer 3b has a film thickness of 12 nm.
That is, the recording layer 3b is thicker than the recording
layer 3a. By way of example, a Ge-In-Sb-Te alloy is employed
as the material of the recording layer 3b.
The upper protection layer 4b has a film thickness
of 20 nm. By way of example, SiO2 is employed as the material
of the upper protection layer 4b.
The reflective layer 8 has a film thickness of 140
nm. By way of example, Ag is employed as the material of the
reflective layer 8.
That is, the layer L1 is 272 nm in thickness.
The substrate lb is 0.6 mm in thickness. By way of
example, polycarbonate is employed as the material of the
substrate lb.
Part of a light beam incident on the optical disk 15
is reflected from the layer L0, and the remaining part of the
light beam passes through the layer L0. The light beam
passing through the layer L0 is reflected from the layer L1.
Further, a spiral guide groove is formed in each of the layers
L0 and L1.
[Method of Manufacturing Optical Disk 15]
(a) A spiral groove of a track pitch of 0.74 µm is
formed on a first polycarbonate board of 0.565 mm in thickness

serving as the substrate la. This groove wobbles at a period
of 4.7 µm so that the period of a wobble signal is 1.22 µs at
the reference velocity of 3.83 m/s. The wobble shape is
partially phase-modulated. Address information, calibration
information used to calibrate write (recording) power for
writing onto the layer LO, and information on write power
recommended for writing onto the layer LO are stored in the
phase-modulated part of the wobble shape.
(b) A film of a mixture of ZnS and SiO2 to serve as
the lower protection layer 2a is formed on the groove formed
on the first polycarbonate board using a magnetron sputtering
device. The mixture film is 200 nm in thickness. The film
thickness is measured using ellipsometry and the fluorescent
X-ray method together.
(c) In the same manner, an In-Sb-Ge alloy film to
serve as the recording layer 3a is formed on the mixture film.
The In-Sb-Ge alloy film is 8 nm in thickness.
(d) In the same manner, a SiO2 film to serve as the
upper protection layer 4a is formed on the In-Sb-Ge alloy film.
The SiO2 film is 20 nm in thickness.
(e) In the same manner, a Cu film to serve as the
semi-transparent layer 5 is formed on the SiO2 film. The Cu
film is 8 nm in thickness.
(f) In the same manner, an ITO film to serve as the
intermediate layer 6 is formed on the Cu film. The ITO film

is 150 nm in thickness.
For convenience, the first polycarbonate board and
these stacked layers of the ZnS-SiO2 mixture film, the In-Sb-Ge
alloy film, the SiO2 film, the Cu film, and the ITO film on the
first polycarbonate board are collectively referred to as an
LO substrate.
(g) The same groove as in (a) is formed on a second
polycarbonate board of 0.6 mm in thickness serving as the
substrate lb. Here, address information, calibration
information used to calibrate write (recording) power for
writing onto the layer L1, and information on write power
recommended for writing onto the layer L1 are stored in the
phase-modulated part.
(h) A Ag film to serve as the reflective layer 8 is
formed on the groove formed on the second polycarbonate board
using a magnetron sputtering device. The Ag film is 140 nm in
thickness.
(i) In the same manner, a SiO2 film to serve as the
upper protection layer 4b is formed on the Ag film. The SiO2
film is 20 nm in thickness.
(j) In the same manner, a Ge-In-Sb-Te alloy film to
serve as the recording layer 3b is formed on the SiO2 film.
The Ge-In-Sb-Te alloy film is 12 nm in thickness.
(k) In the same manner, a film of a mixture of ZnS
and SiO2 to serve as the lower protection layer 2b is formed on

the Ge-In-Sb-Te alloy film. The mixture film is 100 nm in
thickness.
For convenience, the second polycarbonate board and
these stacked layers of the Ag film, the SiO2 film, the Ge-In-
Sb-Te alloy film, and the ZnS-SiO2 mixture film on the second
polycarbonate board are collectively referred to as an L1
substrate.
(1) A commercially available adhesive agent for DVDs
is applied to the intermediate layer 6 of the L0 substrate and
the lower protection layer 2b of the L1 substrate, and the L0
substrate and the L1 substrate are stuck together.
(m) The stuck LO and L1 substrates are irradiated
with ultraviolet rays from the L0 substrate side so that the
adhesive agent is hardened. The layer of the adhesive agent
is approximately 50 µm in thickness. The thickness of the
adhesive agent layer is measured by a so-called interference
method using a spectrophotometer. That is, here, the optical
disk 15 is manufactured by the so-called inverted stack method.
[Initialization of Recording Layers]
Laser light of 810 ran wavelength is emitted onto and
scans the recording layers 3a and 3b, so that each of the
recording layers 3a and 3b is initialized. Here, by way of
example, the light emission power is 700 mW for the recording
layer 3a and 1600 mW for the recording layer 3b. A light spot
in the recording layers 3a and 3b is shaped as an ellipse of 1

(µm) x 75 (µm) , and the scanning velocity is 3.5 m/s. The
directions of the shorter axis of the light spot coincide with
the tangential directions of a track. Before initialization,
the recording layers 3a and 3b are in an amorphous state and
have high transmittance. Accordingly, in order to reduce time
required for initialization, first, the recording layer 3b is
initialized, and thereafter, the recording layer 3a is
initialized. In this case, for example, the reflectance after
initialization is 8.5% in the layer LO and 7.5% in the layer
L1.
[Calibration Information]
Calibration information employed to calibrate write
power includes Pind, p, and ytarget (for example, see ECMA-337).
Here, by way of example, Pind = 33.6 mW, p = 1.25, and ytarget
= 1.4 in the layer LO, and Pind =40 mW, p = 1.25, and ytarget
= 1.5 in the layer L1.
[Write Strategy Information]
Write strategy information includes a variety of
parameters defining a light emission waveform according to
mark length nT (n = 3 through 11, T is the period of a write
channel clock). Here, by way of example, so-called 2T write
strategy is employed as shown in FIGS. 3A through 6. FIG. 3A
shows a light emission waveform at the time of formation of a
3T mark. FIG. 3B shows a light emission waveform at the time
of formation of a 4T mark. FIG. 4A shows a light emission

waveform at the time of formation of a 5T mark. FIG. 4B shows
a light emission waveform at the time of formation of a 6T
mark. For the marks of even multiples of T greater than the
6T mark, the same parameters as for the 6T mark are employed,
and only the number of pulses of a pulse width Tmp (so-called
intermediate heating pulses) is different. FIG. 5 shows a
light emission waveform at the time of formation of a 7T mark.
For the marks of odd multiples of T greater than the 7T mark,
the same parameters as for the 7T mark are employed, and only
the number of pulses of the pulse width Tmp (so-called
intermediate heating pulses) is different. FIG. 6 is a table
showing a value of each parameter.
[Disk Layout of Optical Disk 15]
By way of example, the optical disk 15 supports a
standard called opposite track path (OTP) as shown in FIG. 7.
That is, in the layer L0, a lead-in zone, a data
zone, and a middle zone are provided in this order from the
center to the edge of the optical disk 15. Meanwhile, in the
layer L1, a middle zone, a data zone, and a lead-out zone are
provided in this order from the edge to the center of the disk.
The layer L0 is assigned physical addresses to successively
increase from the lead-in zone to the middle zone. The layer
L1 is assigned physical addresses to successively increase
from the middle zone to the lead-out zone. Here, the start
address and the end address of the data zone of the layer LO

are 030000h and 22D7FFh, respectively, and the start address
and the end address of the data zone of the layer L1 are
DD2800h and FCFFFFh, respectively.
The data zone is provided between radial positions
of 24.0 mm and 58.0 mm in each of the layers L0 and L1. By
way of example, as shown in FIG. 8, a drive test zone that is
the test writing area of the layer L0 is provided in the lead-
in zone, and a drive test zone that is the test writing area
of the layer L1 is provided in the lead-out zone. Each drive
test zone is provided between radial positions of 23.4 mm and
23.75 mm, and the drive test zones are superposed on each
other when viewed from the direction of incidence of a light
beam.
Further, by way of example, as shown in FIG. 9, a
drive test zone that is the test writing area of the layer L0
is provided in the middle zone of the layer L0, and a drive
test zone that is the test writing area of the layer L1 is
provided in the middle zone of the layer L1. Each drive test
zone is provided between radial positions of 58.1 mm and 58.25
mm, and the drive test zones are superposed on each other when
viewed from the direction of incidence of a light beam.
That is, here, the test writing area is provided in
the center part and the peripheral part of each of the
recording layers 3a and 3b. Hereinafter, the drive test zones
are also referred to as "PCA (Power Calibration Area)" for

convenience.
The optical pickup unit 23 is a device for focusing
laser light on one of the two recording layers 3a and 3b of
the optical disk 15 which one is a target of access, and
receiving reflected light from the optical disk 15.
Hereinafter, the one of the two recording layers 3a and 3b of
the optical disk 15 which one is a target of access is
abbreviated as "target recording layer." By way of example,
as shown in FIG. 10, the optical pickup unit 23 includes a
light source unit 51, a coupling lens 52, a polarization beam
splitter 54, a 1/4 wave plate 55, an objective lens 60, a
collective lens (detection lens) 58, a light receiver PD
serving as a photodetector, and a drive system AC for driving
the objective lens 60.
The light source unit 51 includes a semiconductor
laser LD serving as a light source to emit laser light of a
wavelength corresponding to the optical disk 15 (in this case,
approximately 660 nm). In this embodiment, the direction of
maximum intensity emission of laser light emitted from the
light source unit 51 is a positive (+) X direction indicated
by the arrow X in FIG. 10. Further, by way of example, a
light beam of polarization parallel to the plane of incidence
of the polarization beam splitter 54 (p-polarization) is
emitted from the light source unit 51.
The coupling lens 52 is disposed on the positive X

side of the light source unit 51 so as to convert the light
beam emitted from the light source unit 51 into a
substantially parallel beam.
The polarization beam splitter 54 is disposed on the
positive X side of the coupling lens 52. The reflectance of
the polarization beam splitter 54 differs depending on the
polarization state of a light beam made incident thereon.
Here, by way of example, the polarization beam splitter 54 is
set so as to have low reflectance for p-polarized light and
high reflectance for s-polarized light. That is, most of the
light beam emitted from the light source unit 51 is allowed to
pass through the polarization beam splitter 54. The 1/4 wave
plate is disposed on the positive X side of the polarization
beam splitter 54.
The 1/4 wave plate 55 provides a light beam made
incident thereon with an optical phase difference of a 1/4
wavelength. The objective lens 60 is disposed on the positive
X side of the 1/4 wave plate, and focuses a light beam passing
through the 1/4 wave plate on the target recording layer.
Here, the NA (numerical aperture) is 0.60.
The collective lens 58 is disposed on the negative
(-) Z side of the polarization beam splitter 54 so as to focus
a returning light beam diverging in the negative Z direction
in the polarization beam splitter 54 on the light-receiving
surface of the light receiver PD. The light receiver PD

includes multiple light-receiving elements (or light-receiving
areas) for generating optimum signals (photoelectrically
converted signals) for detecting an RF signal, a wobble signal,
and servo signals in the reproduced signal processing circuit
28.
The drive system AC includes a focusing actuator for
driving the objective lens 60 minutely in the focus directions,
or the optical axis directions of the objective lens 60, and a
tracking actuator for driving the objective lens 60 minutely
in the tracking directions. Here, for convenience, the
optimum position of the objective lens 60 with respect to the
focus directions at a time when the target recording layer is
the recording layer 3a is referred to as "first lens
position," and the optimum position of the objective lens 60
with respect to the focus directions at a time when the target
recording layer is the recording layer 3b is referred to as
"second lens position."
A description is given of the operation of the
optical pickup unit 23 having the above-described structure.
A linearly polarized (p-polarized in this case)
light beam emitted from the light source unit 51 is converted
into a substantially parallel light beam in the coupling lens
52 and enters the polarization beam splitter 54. Most of the
light beam passes as it is through the polarization beam
splitter 54 to be circularly polarized in the 1/4 wave plate

55, and is focused into a fine spot on the target recording
layer of the optical disk 15 through the objective lens 60.
Reflected light from the optical disk 15 is circularly
polarized in the opposite direction from that of the light
beam incident on the optical disk 15 so as to be converted
again into a substantially parallel beam in the objective lens
60 as a returning light beam. The returning light beam is
converted into a linearly polarized (s-polarized in this case)
light beam perpendicular to that emitted from the light source
unit 51 in the 1/4 wave plate 55. Then, this returning light
beam enters the polarization beam splitter 54. The returning
light beam 54 is reflected in the negative Z direction in the
polarization beam splitter 54, and is received by the light
receiver PD through the collective lens 58. In the light
receiver PD, photoelectric conversion is performed in each
light-receiving element (or light-receiving area), and each
photoelectrically converted signal is output to the reproduced
signal processing circuit 28.
Referring back to FIG. 1, the reproduced signal
processing circuit 28 obtains servo signals (such as a focus
error signal and a tracking error signal), address information,
synchronization information, and an RF signal based on the
output signals (photoelectrically converted signals) of the
light receiver PD. The obtained servo signals are output to
the drive control circuit 26. The obtained address

information is output to the CPU 40. The obtained
synchronization signal is output to the encoder 25, the drive
control circuit 26, etc. Further, the reproduced signal
processing circuit 28 performs decoding and error detection on
the RF signal. In the case of detecting error, the reproduced
signal processing circuit 28 performs error correction, and
thereafter, stores the RF signal in the buffer RAM 34 through
the buffer manager 37 as reproduced data. Further, the
address information included in the reproduced data is output
to the CPU 40.
The drive control circuit 26, based on the tracking
error signal fed from the reproduced signal processing circuit
28, generates a tracking actuator driving signal for
correcting the position offset of the objective lens 60 with
respect to the tracking directions. Further, the drive
control circuit 26, based on the focus error signal fed from
the reproduced signal processing circuit 28, generates a
focusing actuator driving signal for correcting the focus
error of the objective lens 60. The generated driving signals
are output to the optical pickup unit 23 so that tracking
control and focus control are performed. Further, the drive
control circuit 26, based on instructions from the CPU 40,
generates a driving signal for driving the seek motor 21 and a
driving signal for driving the spindle motor 22. The driving
signals are output to the seek motor 21 and the spindle motor

22, respectively.
The buffer RAM 34 temporarily stores data to be
recorded on the optical disk 15 (recording data) and data
reproduced from the optical disk 15 (reproduced data). The
buffer manager 37 manages data input to and data output from
the buffer RAM 34.
The encoder 25, based on an instruction from the CPU
40, extracts recording data stored in the buffer RAM 34
through the buffer manager 37, performs modulation on the data,
and adds an error correction code to the data, thereby
generating a write signal for writing onto the optical disk 15.
The generated write signal is output to the laser control
circuit 24.
The laser control circuit 24 controls the light
emission power of the semiconductor laser LD. For example, in
the case of recording, a signal to drive the semiconductor
laser LD is generated in the laser control circuit 24 based on
the write signal, write (recording) conditions, and the light
emission characteristics of the semiconductor laser LD.
The interface 38 is a bidirectional communications
interface with a host apparatus 90 such as a personal computer,
and is compliant with standard interfaces such as ATAPI (AT
Attachment Packet Interface), SCSI (Small Computer System
Interface), and USB (Universal Serial Bus).
The flash memory 39 stores a variety of programs

including one coded in a code decodable by the CPU 40
according to the embodiment of the present invention, and a
variety of data including the light emission characteristics
of the semiconductor laser LD.
The CPU 40 controls the operation of each of the
above-described parts of the optical disk unit 20 in
accordance with the programs stored in the flash memory 39,
and stores data necessary for the control in the RAM 41 and
the buffer RAM 34.
[Recording Operation]
Next, a description is given, with reference to FIG.
11, of an operation in the optical disk unit 20 at the time of
receiving a recording request from the host apparatus 90. The
flowchart of FIG. 11 corresponds to a series of processing
algorithms executed by the CPU 40. When a recording request
(command) is received from the host apparatus 90, the start
address of a program stored in the flash memory 39 and
corresponding to the flowchart of FIG. 11 (hereinafter
referred to as "recording operation algorithm") is set in the
program counter of the CPU 40, and a recording operation is
started.
First, in step S401, an instruction is given to the
drive control circuit 26 so that the optical disk 15 rotates
at a predetermined linear velocity (or angular velocity), and
the reproduced signal processing circuit 28 is notified of

reception of the recording request (command) from the host
apparatus 90. By way of example, the write (recording)
scanning velocity is 9.19 m/s (2.4 times that in a DVD).
Next, in step S403, calibration conditions and write
strategy information recorded on the optical disk 15 are
obtained through the reproduced signal processing circuit 28.
Here, the reproduced signal processing circuit 28 performs
phase demodulation on a wobble signal detected in each layer,
and extracts calibration conditions and write strategy
information layer by layer.
Next, in step S405, the recording state of PCA in
each layer is obtained. Here, detection as to whether the PCA
of the layer L0 is recorded or unrecorded (whether recording
has been performed on the layer L0) and whether the PCA of the
layer L1 is recorded or unrecorded (whether recording has been
performed on the layer L1) is performed based on, for example,
the intensity of reflected light from each PCA.
Next, in step S407, it is determined whether the PCA
of the layer LO is recorded. If the PCA of the layer LO is
unrecorded (NO in step S407), the operation proceeds to step
S411.
In step S411, write conditions are set based on the
write strategy information in the layer LO obtained in step
S403. Parameters defining the light emission waveform of the
semiconductor laser LD are set in a register (not graphically

illustrated) of the laser control circuit 24.
Next, in step S413, an optimum write power (PwO) is
determined by performing OPC based on the calibration
information in the layer L0 obtained in step S403. Here, by
way of example, PwO = 42 mW is obtained.
Next, in step S415, dummy data is recorded in the
PCA of the layer LO with the optimum write power PwO
determined in step S413.
Next, in step S421, it is determined whether the PCA
of the layer L1 is recorded. If the PCA of the layer L1 is
unrecorded (NO in step S421), the operation proceeds to step
S423.
In step S423, write conditions are set based on the
write strategy information in the layer L1 obtained in step
S403.
Next, in step S425, an optimum write power (Pw1) is
determined by performing OPC based on the calibration
information in the layer L1 obtained in step S403. Here, by
way of example, Pwl = 50 mW is obtained.
Next, in step S427, dummy data is recorded in the
PCA of the layer L1 with the optimum write power Pwl
determined in step S425.
Next, in step S431, the target recording layer is
specified from a specified address included in the recording
request (command).

Next, in step S433, the PCA of the target recording
layer is made "unrecorded." Specifically, laser light of
erase power is emitted from the semiconductor laser LD onto
the PCA of the target recording layer. That is, so-called DC
erasure is performed.
Next, in step S435, write conditions are set based
on the write strategy information in the target recording
layer obtained in step S403.
Next, in step S437, an optimum write power Pw is
determined by performing OPC based on the calibration
information in the target recording layer obtained in step
S403.
Next, in step S439, dummy data is recorded in the
PCA of the target recording layer with the optimum write power
Pw determined in step S437.
Next, in step S441, user data is recorded at the
requested address of the target recording layer with the
optimum write power Pw determined in step S437. When the
recording of the user data is completed, the host apparatus 90
is notified of the completion, and the recording operation
ends.
In step S407, if the PCA of the layer L0 is recorded
(YES in step S407), the operation proceeds to step S421.
In step S421, if the PCA of the layer L1 is recorded
(YES in step S421), the operation proceeds to step S431.

When recording was performed with the write
conditions shown in FIG. 6, with ten overwrite operations (DOW
10), jitter was 8.6% and the degree of modulation was 0.60 in
the layer L0, and jitter was 8.2% and the degree of modulation
was 0.68 in the layer L1. Further, with one hundred overwrite
operations (DOW 100), jitter was 9.6% in the layer L0 and
jitter was 8.5% in the layer L1. In each case, the jitter of
each of the layers L0 and L1 was at a level causing no problem
in reproduction, being less than 10%. Here, the evaluations
were performed using ODU-1000, a DVD evaluation apparatus of
Pulstec Industrial Co., Ltd., with a read power of 1.4 mW and
a read (reproduction) scanning velocity of 3.83 m/s. The
details of jitter and the degree of modulation are described
in ECMA-337.
By way of example, as shown in FIG. 12, the write
power for obtaining a predetermined degree of modulation in
the layer L1 differs depending on the recording state of the
layer L0. If the layer L0 is unrecorded, a higher write power
is required than in the case where the layer L0 is recorded.
This is because T where the layer L0 is unrecorded, and T' is a transmittance in
the case where the layer L0 is recorded. The write power
differs depending on the number of times of overwrite even
though the layer L0 is recorded. However, the difference is
small.

By way of example, as shown in FIG. 13, the write
power for maintaining good jitter in the layer L1 also differs
depending on the recording state of the layer L0. If the
layer L0 is unrecorded, a higher write power is required than
in the case where the layer L0 is recorded. The minimum value
of jitter is smaller in the case where the layer L0 is
recorded than in the case where the layer L0 is unrecorded.
From these, letting the optimum write power in the
layer L1 in the case where the layer L0 is unrecorded be Po,
and letting the optimum write power in the layer L1 in the
case where the layer L0 is recorded be Po' , Po is greater than
Po' (P0 > P0').
Further, letting the intensity of reflected light
from the layer L1 in the case where the layer L0 is unrecorded
be R, and letting the intensity of reflected light from the
layer L1 in the case where the layer L0 is recorded be R', R
is less than R' (R Further, by way of example, as shown in FIG. 14, the
degree of modulation in the layer L1 varies also because of
write power in the layer L0. This is because the size of an
amorphous area in the layer L0 differs depending on write
power. In the case of FIG. 14, recording is performed in the
layer L1 with a constant write power (write power level) after
performing recording in the layer L0 with various write powers
(write power levels). That is, it is possible to maintain

high degrees of modulatipn in the layer L1 if recording is
performed in the layer L0 with high write power.
According to this embodiment, first, OPC is
performed on the layer L0 so that dummy data is recorded in
the PCA of the layer L0 with optimum write power, and then,
OPC is performed on the layer L1 so that dummy data is
recorded in the PCA of the layer L1 with optimum write power.
Thereafter, optimum write power is determined with respect to
the target recording layer by performing OPC thereon.
Accordingly, it is possible to determine optimum write power
that matches an actual situation of user data recording.
As a comparative example, when OPC was performed in
the layer L1 in the same manner as described above with the
PCA of the layer L0 being unrecorded, the obtained optimum
write power was 55 mW. Then, recording was performed in the
layer L0 with a write power of 42 mW, and overwriting was
performed 100 times on the layer L1 with a write power of 55
mW. This resulted in a jitter value of 11%. This corresponds
to a level more than 100 times of so-called PI error, and may
cause reproduction error.
As is apparent from the above description, in the
optical disk unit 20 according to this embodiment, the flash
memory 39 forms memory, and the encoder 25 and the laser
control circuit 24 form a processing unit. Further, the CPU
40 forms a computer for control (controlling computer).

Further, according to this embodiment, of the
programs stored in the flash memory 39, the program of the
above-described recording operation includes a program
according to this embodiment of the present invention.
In the above-described recording operation, a
recording method according to this embodiment of the present
invention is performed.
As described above, according to the optical disk
unit 20 according to this embodiment, at the time of recording
user data on the optical disk 15, which is a rewritable
single-sided double-layer disk where a test writing area is
provided in each recording layer and the test writing areas of
the adjacent recording layers are superposed on each other
when viewed from the direction of incidence of a light beam,
first, OPC is performed on the layer L0 so that dummy data is
recorded in the PCA of the layer L0 with optimum write power,
and then, OPC is performed on the layer L1 so that dummy data
is recorded in the PCA of the layer L1 with optimum write
power. Thereafter, OPC is performed on the target recording
layer, so that optimum write power is determined with respect
to the target recording layer. As a result, it is possible to
determine optimum write power whichever of the two recording
layers of the optical disk 15 is to have user data recorded
therein. As a result, it is possible to perform recording
with stable recording quality.

Further, according to the optical disk 15 according
to this embodiment, the test writing areas of the adjacent
recording layers are superposed on each other in a view from
the direction of incidence of a light beam. Accordingly, an
optical disk unit in which the optical disk 15 is set can
easily determine optimum write power matching an actual
situation of user data recording. As a result, it is possible
to perform stable recording.
Further, according to the optical disk 15 according
to this embodiment, calibration information and write strategy
information are "pre-formatted." Accordingly, an optical disk
unit in which the optical disk 15 is set can obtain optimum
write power swiftly.
In this embodiment, the above description is given
of the case where the optical disk 15 is manufactured by the
inverted stack method. The manufacturing method of the
optical disk 15 is not limited to this, and the optical disk
15 may be manufactured by the so-called 2P method.
Further, in this embodiment, the above description
is given of the case where the optical disk 15 has two
recording layers. However, the present invention is not
limited to this, and the optical disk 15 may have three or
more recording layers. In this case, at the time of recording
information in, for example, the Nth cL0sest recording layer to
the light beam entrance surface, OPC is performed in the Nth

recording layer after converting at least one of the PCA of
the (N-1)th recording layer and the PCA of the (N+1)th recording
layer into a recorded state (that is, after recording data in
at least one of the PCA of the (N-1)th recording layer and the
PCA of the (N+1)th recording layer).
Further, in this embodiment, the above description
is given of the case where the optical disk 15 is 120 mm in
diameter. However, the present invention is not limited to
this, and the optical disk 15 may be, for example, 80 mm or 30
mm in diameter.
Further, in this embodiment, the above description
is given of the case where each recording layer independently
stores calibration information and write strategy information
corresponding thereto. However, the present invention is not
limited to this, and the calibration information and the write
strategy information corresponding to all recording layers may
be recorded in one of the recording layers.
Further, in this embodiment, the above description
is given of the case where the calibration information and the
write strategy information are set recording layer by
recording layer. However, the present invention is not
limited to this. For example, if the difference in
calibration information and write strategy information between
recording layers is small, the average calibration information
and write strategy information may be set and recorded in one

of the recording layers.
Further, in this embodiment, for example, if the
range of supportable recording rates is wide, the calibration
information may be set recording rate by recording rate.
Further, in this embodiment, for example, if the
range of supportable recording rates is wide, the write
strategy information may be set recording rate by recording
rate.
Further, in this embodiment, the above description
is given of the case where the test writing areas of adjacent
recording layers are superposed on each other in a view from
the direction of incidence of a light beam. Alternatively,
the test writing areas of adjacent recording layers may be
superposed partly on, or overlap with, each other. In this
case, the overlap is preferably at least 50%, and more
preferably 70%, of the entire area. In the case of
overlapping (partial superposition), it is preferable to
perform OPC in the overlapping area.
Further, in this embodiment, the above description
is given of the case where the test writing area is provided
in each of the center part and the peripheral part of the
optical disk 15. However, the present invention is not
limited to this, and the test writing area may be provided in
one of the center part and the peripheral part of the optical
disk 15.

Further, in this embodiment, the above description
is given of the case where the test writing area of the center
part of the optical disk 15 is provided between radial
positions of 23.4 mm and 23.75 mm. However, the present
invention is not limited to these radial positions.
Further, in this embodiment, the above description
is given of the case where the test writing area of the
peripheral part of the optical disk 15 is provided between
radial positions of 58.1 mm and 58.25 mm. However, the
present invention is not limited to these radial positions.
Further, in this embodiment, the above description
is given of the case where 2T write strategy is empL0yed.
However, the present invention is not limited to this, and so-
called 1T write strategy may be empL0yed.
Further, in this embodiment, the above description
is given of the case where the disk layout supports OTP.
However, the present invention is not limited to this, and the
disk layout may support parallel track path (PTP).
Further, the material and the thickness of each
layer of the optical disk 15 may be, but are not limited to,
those described above in this embodiment.
(a) As the material of the substrate la, other
resins such as polyolefin-based and acryl-based resins, and
glass may also be employed. That is, materials for the
substrate la have high transmittance with respect to a light

beam emitted from the optical pickup unit 23. In terms of
processability and manufacturing cost, however, it is
preferable to empL0y resin.
(b) Inorganic material is preferable as the material
of each of the protection layers 2a, 4a, 2b, and 4b. For
example, metal or alL0y oxides, and simple substances or
mixtures of sulfides, nitrides, and carbides may be empL0yed.
Further, each of the protection layers 2a, 4a, 2b, and 4b may
have a multilayer structure. The material of each of the
protection layers 2a, 4a, 2b, and 4b is required to have a
melting point higher than that of the material of the
recording layer 3a, and at the same time, appropriate
toughness. Further, the material of each of the protection
layers 2a, 4a, 2b, and 4b is required to have transparency in
the wavelength range of an incident light beam. Materials
satisfying these conditions include, in addition to ZnS and
SiO2, MgO, Al2O3, SiO, ZnO2, InO2, SnO2, TiO2, ZrO2, Y2O3, AlN,
Si3N4, GaN, GeN, SiC, TiC, and TaC.
(c) The optimum film thickness of the L0wer
protection layer 2a, which is determined by reflectance and
recording sensitivity, preferably falls within the range of 40
nm to 300 nm.
(d) Since it is necessary to ensure a predetermined
transmittance in the recording layer 3a, the recording layer
3a should be reduced in film thickness compared with the case

of a single-layer disk having one recording layer. In general,
however, a thinner phase change material tends to have a L0wer
rate of crystallization. Accordingly, phase change materials
empL0yed in high-speed compliant optical disks such as 8X
(scanning veL0city: 27.9 m/s) single-layer DVD+RWs are
preferable. Specifically, an In-Sb alloy, Ga-Sb alloy, and
Ge-Sb alloy with a third metal added thereto may be used.
(e) The optimum film thickness of the upper
protection layer 4a, which is determined by thermal design,
preferably falls within the range of 4 nm to 50 nm.
(f) The material of the semi-transparent layer 5 may
also be an alloy whose principal component is Au, Ag, Al, or
Cu. Alternatively, the material of the semi-transparent layer
5 may also be a simple substance of Au, Ag, or Al.
(g) The optimum film thickness of the semi-
transparent layer 5, which is determined from transmittance
and reflectance, preferably falls within the range of 2 nm to
50 nm. More preferably, the optimum film thickness of the
semi-transparent layer 5 falls within the range of 5 nm to 15
nm particularly in order to ensure transmittance. If the
semi-transparent layer 5 exceeds 50 nm in film thickness, it
becomes difficult to ensure reflectance in the layer L1. If
the semi-transparent layer 5 is less than 2 nm in film
thickness, insufficient thermal diffusion results, so that
rapid cooling of the recording layer 3a is hindered. This

increases the possibility of a decrease in recording
sensitivity and deterioration of jitter.
(h) Materials for the intermediate layer 6 have
transparency in the wavelength range of an incident light beam
and high thermal conductivity. For example, a simple
substance or mixture of In2O3, SnO2, ZnO2, or Ga2O3 with a dopant
added thereto is usually employed. The dopant may be Al, Ga,
B, In, Y, Sc, F, V, Si, Ge, Ti, Zr, Hf, Sb, Mo, etc.
(i) The optimum film thickness of the intermediate
layer 6, which is determined by thermal design and optical
design, preferably falls within the range of 10 nm to 300 nm,
more preferably, the range of 50 nm to 200 nm.
(j) The material of the reflective layer 8 may also
be an alL0y whose principal component is Ag, Au, Cu, or Al.
Alternatively, the material of the reflective layer 8 may be a
simple substance of Au, Cu, or Al.
(k) Materials for the adhesive layer 7 do not
corrode an adjacent layer and have transparency in the
wavelength range of an incident light beam.
(1) The optimum thickness of the adhesive layer 7,
which is determined so that interlayer crosstalk and wave
front aberration are at or below predetermined levels,
preferably falls within the range of 40 nm to 70 nm.
Further, in this embodiment, the program according
to the present invention is recorded in the flash memory 39.

Alternatively, the program may be recorded in other recording
media such as a CD, magneto-optical disk, DVD, memory card,
USB memory, and flexible disk. In this case, the program is
L0aded into the flash memory 39 through a reproduction
apparatus (or dedicated interface) corresponding to a
recording medium in which the program is recorded. The
program may be forwarded to the flash memory 39 through a
network such as a LAN, an intranet, or the Internet. That is,
the program according to the present invention is stored in
the flash memory 39.
Further, in this embodiment, the above description
is given of the case where the optical disk 15 is a DVD-type
information recording medium. However, the present invention
is not limited to this, and the optical disk 15 may be, for
example, a CD-type rewritable single-sided multilayer disk or
a rewritable single-sided multilayer disk corresponding to a
light beam of 405 nm wavelength. In this case, for example,
the track pitch is 1.6 µm for a CD for which NA = 0.5 and λ
(wavelength) = 780 nm, and is 0.4 µm for an HD DVD for which
NA = 0.65 and λ = 405 nm.
Further, in this embodiment, the above description
is given of the case where the optical pickup unit 23 has one
semiconductor laser. However, the present invention is not
limited to this, and for example, the optical pickup unit 23
may have multiple semiconductor lasers emitting respective

light beams different in wavelength from each other. In this
case, the optical pickup unit 23 may include at least one of,
for example, a semiconductor laser emitting a light beam of a
wavelength of approximately 405 nm, a semiconductor laser
emitting a light beam of a wavelength of approximately 660 nm,
and a semiconductor laser emitting a light beam of a
wavelength of approximately 780 nm. That is, the optical disk
unit 20 may support multiple types of optical disks compliant
with respective standards different from each other. In this
case, at least one of the multiple types of optical disks may
be a rewritable single-sided multilayer disk.
As described above, the optical disk 15 according to
this embodiment has multiple rewritable recording layers, and
is suitable for stable recording and reproduction. Further,
the recording method and the optical disk unit 20 according to
this embodiment are suitable for performing recording on the
optical disk 15 of this embodiment with stable recording
quality. Further, the program and the recording medium
according to this embodiment are suitable for causing the
optical disk unit 20 to perform recording on the optical disk
15 of this embodiment with stable recording quality.
According to one embodiment of the present invention,
a single-sided multilayer optical disk including multiple
information rewritable recording layers each having a spiral
track or concentric tracks formed thereon is provided, wherein

a test writing area to be used for calibration of write power
is provided in each of the recording layers, and the test
writing areas of adjacent two of the recording layers are
superposed at least partly on each other in a view from the
direction of incidence of a light beam.
This optical disk alL0ws an optical disk unit in
which the optical disk is set to perform positioning swiftly
at the time of performing test writing in one recording layer
after another, and accordingly, to calibrate write power in
each recording layer in a short period of time. As a result,
it is possible to perform stable recording even if the optical
disk has multiple rewritable recording layers.
According to one embodiment of the present invention,
a method of recording information on a single-sided multilayer
optical disk is provided that includes the step of, before
performing test writing in a first one of the test writing
areas of the recording layers in the optical disk except the
recording layer closest to a light beam entrance surface,
recording data in a second one of the test writing areas
adjacent to the first one of the test writing areas on its
light beam entrance surface side, thereby converting the
second one of the test writing areas into a recorded state.
According to this method, before performing test
writing in a first one of the test writing areas of recording
layers in an optical disk except the recording layer cL0sest

to a light beam entrance surface, a second one of the test
writing areas adjacent to the first one of the test writing
areas on its light beam entrance surface side is converted
into a recorded state. Accordingly, it is possible to
determine an optimum write power matching a situation where
user data is actually recorded, so that it is possible to
perform recording with stable recording quality.
According to one embodiment of the present invention,
a method of recording information on a single-sided multilayer
optical disk is provided that includes the step of, before
performing test writing in a first one of the test writing
areas of the recording layers in the optical disk except the
recording layer most remote from a light beam entrance surface,
recording data in a second one of the test writing areas
adjacent to the first one of the test writing areas on the
opposite side from the light beam entrance surface, thereby
converting the second one of the test writing areas into a
recorded state.
According to this method, before performing test
writing in a first one of the test writing areas of recording
layers in an optical disk except the recording layer most
remote from a light beam entrance surface, a second one of the
test writing areas adjacent to the first one of the test
writing areas on the opposite side from the light beam
entrance surface is converted into a recorded state.

Accordingly, it is possible to suppress the adverse effect of
so-called interlayer crosstalk, so that it is possible to
perform recording with stable recording quality.
According to one embodiment of the present
invention, a computer-readable recording medium on which
recorded is a program for causing a computer to execute any of
the above-described methods of recording information on a
single-sided multilayer optical disk is provided.
According to this computer-readable recording medium,
when the program is loaded into a predetermined memory, and
its start address is set in a program counter, the controlling
computer of an optical disk unit, before performing test
writing in a first one of the test writing areas of recording
layers in an optical disk except the recording layer closest
to a light beam entrance surface, changes a second one of the
test writing areas adjacent to the first one of the test
writing areas on its light beam entrance surface side into a
recorded state. Alternatively, the controlling computer,
before performing test writing in a first one of the test
writing areas of the recording layers except the recording
layer remotest from a light beam entrance surface, may change
a second one of the test writing areas adjacent to the first
one of the test writing areas on the opposite side from the
light beam entrance surface into a recorded state. Thus, it
is possible to cause the controlling computer of the optical

disk unit to execute any of the above-described recording
methods of recording information on the optical disk, so that
it is possible to perform recording with stable recording
quality.
According to one embodiment of the present invention,
an optical disk unit capable of recording information on a
single-sided multilayer optical disk is provided that includes
a memory, an optical pickup unit configured to emit a light
beam onto the optical disk, a controlling computer, and a
processing unit, wherein the memory stores a program for
causing the controlling computer to execute any of the above-
described methods of recording information on the optical
disk; the controlling computer obtains an optimum recording
condition for the optical disk in accordance with the program
stored in the memory; and the processor unit records the
information on the optical disk with the optimum recording
condition through the optical pickup unit.
According to this optical disk unit, the controlling
computer executes a program, recorded in the memory, for
causing the controlling computer to execute any of the above-
described methods of recording the information on the optical
disk, so that an optimum recording condition is obtained. The
processing unit records the information on the optical disk
with the optimum recording condition through an optical pickup
unit. In this case, the controlling computer obtains an

optimum recording condition whichever recording layer of the
optical disk is to have information recorded therein. As a
result, it is possible to perform recording on the optical
disk with stable recording quality.
The present invention is not limited to the
specifically discL0sed embodiment, and variations and
modifications may be made without departing from the scope of
the present invention.
The present application is based on Japanese
Priority Patent Application No. 2005-153872, filed on May 26,
2005, the entire contents of which are hereby incorporated by
reference.

WE CLAIM :
1. A method of recording information using a laser on a multilayer optical disk (15) containing a
plurality of recording layers, the plurality of recording layers having a first recording layer and a
second recording layer,the second recording layer being a recording layer adjacent the first recording
layer, the first recording layer having a first test writing area to be used for calibration of write power
and the second recording layer having a second test writing area to be used for calibration of write
power, wherein a first region of the first test writing area is superposed with a second region of the
second test writing area when considered in the direction in which the laser is arranged to irradiate, the
method comprising:
if the first region of the first test writing area is unrecorded, recording data in the first region of
the first test writing area, thereby converting the first region of the first test writing area into a recorded
state;
if the second region of the second test writing area is unrecorded, recording data in the second
region of the second test writing area, thereby converting the second region of the second test writing
area into a recorded state;
clearing the first region of the first test writing area before performing test writing in the first
region of the first test writing area; and
performing the test writing in the first region of the first test writing area.
2. A method as claimed in claim 1, wherein the second recording layer is the next recording layer
with respect to the first recording layer in the direction in which the laser is arranged to irradiate.
3. A method as claimed in claim 2, wherein the optical disk (15) has a third recording layer, the
third recording layer being the next recording layer with respect to the first recording layer in the
opposite direction to that in which the laser is arranged to irradiate, the third recording layer having a
third test writing area to be used for calibration of write power, wherein a third region of the third test
writing area is superposed with the first region of the first test writing area when considered in the
direction in which the laser is arranged to irradiate, the method involving:
if the third region of the third test writing area is unrecorded, recording data in the third region

of the third test writing area, and thereby converting the third region of the third test writing area into a
recorded state; and
once the third region of the third test writing area has been converted into a recorded state,
performing said test writing in the first region of the first test writing area.
4. A method as claimed in any one of claims 1 to 3, wherein the clearing of the first region of the
first test writing area comprises performing an erasure operation to make the first region unrecorded.
5. A method as claimed in any one of claims 1 to 3, wherein for the first region of the first test
writing area, or the second region of the second test writing area, or the third region of the third test
writing area, the respective step of recording data in the region and thereby converting the region into a
recorded state comprises performing an operation to make the region logically zero.
6. Apparatus for recording information to a multilayer optical disk (15) containing a plurality of
recording layers using a laser, the plurality of recording layers having a first recording layer and a
second recording layer, the second recording layer being a recording layer adjacent the first recording
layer,the first recording layer having a first test writing area to be used for calibration of write power
and the second recording layer having a second test writing area to be used for calibration of write
power, wherein a first region of the first test writing area is superposed with a second region of the
second test writing area when considered in the direction in which the laser is arranged to irradiate,
wherein if the first region of the first test writing area is unrecorded, the apparatus is adapted to record
data in the first region of the first test writing area, and thereby converting the first region of the first
test writing area into a recorded state;
if the second region of the second test writing area is unrecorded, the apparatus is adapted to
record data in the second region of the second test writing area, and thereby converting the second
region of the second test writing area into a recorded state;
the apparatus is also adapted to clear the first region of the first test writing area before
performing test writing in the first region of the first test writing area; and
the apparatus is adapted to perform the test writing in the first region of the first test writing
area.

7. Apparatus as claimed in claim 6, wherein the second recording layer is the next recording layer
with respect to the first recording layer in the direction in which the laser is arranged to irradiate.
8. Apparatus as claimed in claim 7, wherein the optical disk (15) has a third recording layer, the
third recording layer being the next recording layer with respect to the first recording layer in the
opposite direction to that in which the laser is arranged to irradiate, the third recording layer having a
third test writing area to be used for calibration of write power, wherein a third region of the third test
writing area is superposed with the first region of the first test writing area when considered in the
direction in which the laser is arranged to irradiate,wherein if the third region of the third test writing
area is unrecorded, the apparatus is adapted to record data in the third region of the third test writing
area, and thereby converting the third region of the third test writing area into a recorded state; and
once the third region of the third test writing area, has been converted into a recorded state, the
apparatus is adapted to perform said test writing in the first region of the first test writing area.
9. Apparatus as claimed in any one of claims 6 to 8, wherein the clearing of the first region of the
first test writing area is caused to be performed by an erasure operation to make the first region
unrecorded.
10. Apparatus as claimed in anyone of claims 6 to 9, wherein for the first region of the first test
writing area, or the second region of the second test writing area, or the third region of the third test
writing area, the apparatus is adapted to perform an operation to make the region logically zero, so as to
cause the respective recording of data in the region and thereby converting the region into a recorded
state.

Documents:

00192-kolnp-2007-correspondence.pdf

00192-kolnp-2007-form-18.pdf

0192-kolnp-2007-abstract.pdf

0192-kolnp-2007-claims.pdf

0192-kolnp-2007-correspondence others.pdf

0192-kolnp-2007-description(complete).pdf

0192-kolnp-2007-drawings.pdf

0192-kolnp-2007-form-1.pdf

0192-kolnp-2007-form-3.pdf

0192-kolnp-2007-form-5.pdf

0192-kolnp-2007-international publication.pdf

0192-kolnp-2007-international search authority report.pdf

0192-kolnp-2007-pct form.pdf

0192-kolnp-2007-priority document.pdf

192-KOLNP-2007-ABSTRACT.pdf

192-KOLNP-2007-AMANDED CLAIMS.pdf

192-KOLNP-2007-AMNDED PAGES OF SPECIFICATION.pdf

192-KOLNP-2007-CLAIMS.pdf

192-KOLNP-2007-CORRESPONDENCE 1.2.pdf

192-KOLNP-2007-CORRESPONDENCE 1.3.pdf

192-KOLNP-2007-CORRESPONDENCE-1.1.pdf

192-kolnp-2007-correspondence-1.4.pdf

192-KOLNP-2007-CORRESPONDENCE.pdf

192-KOLNP-2007-DESCRIPTION (COMPLETE).pdf

192-KOLNP-2007-DRAWINGS.pdf

192-KOLNP-2007-EXAMINATION REPORT REPLY RECIEVED.pdf

192-kolnp-2007-examination report.pdf

192-KOLNP-2007-FORM 1.pdf

192-kolnp-2007-form 18.pdf

192-KOLNP-2007-FORM 2.pdf

192-kolnp-2007-form 3-1.1.pdf

192-KOLNP-2007-FORM 3.pdf

192-kolnp-2007-form 5.pdf

192-KOLNP-2007-FORM-27.pdf

192-kolnp-2007-gpa.pdf

192-kolnp-2007-granted-abstract.pdf

192-kolnp-2007-granted-claims.pdf

192-kolnp-2007-granted-description (complete).pdf

192-kolnp-2007-granted-drawings.pdf

192-kolnp-2007-granted-form 1.pdf

192-kolnp-2007-granted-form 2.pdf

192-kolnp-2007-granted-specification.pdf

192-KOLNP-2007-OTHERS 1.1.pdf

192-kolnp-2007-others-1.2.pdf

192-KOLNP-2007-OTHERS.pdf

192-KOLNP-2007-PA.pdf

192-kolnp-2007-reply to examination report.pdf


Patent Number 247525
Indian Patent Application Number 192/KOLNP/2007
PG Journal Number 16/2011
Publication Date 22-Apr-2011
Grant Date 13-Apr-2011
Date of Filing 16-Jan-2007
Name of Patentee RICOH COMPANY, LTD.
Applicant Address 3-6, NAKAMAGOME, 1-CHOME, OHTA-KU, TOKYO
Inventors:
# Inventor's Name Inventor's Address
1 KATO, MASAKI 10-11-101,HIGASHIRINKAN 2-CHOME, SAGAMIHARA-SHI KANAGAWA 228-0811
2 ITO, KAZUNORI 35-22, EDAHIGASHI, 4-CHOME, TSUZUKI-KU, YOKOHAMA-SHI, KANAGAWA 224-0006
3 SHINOTSUKA, MICHIAKI 45-211, RYUJYOGAOKA, 6-CHOME, HIRATSUKA-SHI, KANAGAWA 254-0814
4 HIBINO, EIKO 7-2-306, NAKAMACHIDAI, 5-CHOME, TSUZUKI-KU, YOKOHAMA-SHI, KANAGAWA 224-0041
5 SHINKAI, MASARU 683, KAWASHIMACHO, HODOGAYA-KU, YOKOHAMA-SHI, KANAGAWA 240-0045
6 SEKIGUCHI, HIROYOSHI 17-27, EDAMINAMI 2-CHOME, TSUZUKI-KU, YOKOHAMA-SHI, KANAGAWA, 224-0007
7 YAMADA, KATSUYUKI 5791-1-401, IRIYA 3-CHOME, ZAMA-SHI, KANAGAWA 228-0024
PCT International Classification Number N/A
PCT International Application Number PCT/JP2006/310940
PCT International Filing date 2006-05-25
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2005-153872 2005-05-26 Japan