Title: Optical disk, and method and apparatus for reproducing information recorded in optical disk
Abstract: An optical disk is provided for recording data of a signal modulated according to a predetermined modulation method in a form of concavo-convex pits. The optical disk includes a first area having a reflecting film partly removed, and a second area for recording pits which are different from pits satisfying requirements of the predetermined modulation method. The first area having the reflecting film partly removed includes a portion which is formed by removing the reflecting film, and has a length longer than a maximum pit length determined by the modulation method in a circumferential direction of the optical disk. When the pits recorded on the optical disk are physically copied as they are, physical copying of the optical disk can be prevented by utilizing such a difference that the authorized optical disk differs from a pirated copy in a combination of the respective reproduced signals of the first and second areas.
Patent Number: 6,891,788 Issued on 05/10/2005 to Yumiba, et al.
| Inventors:
|
Yumiba; Takashi (Kyoto, JP);
Takizawa; Teruyuki (Osaka, JP);
Moriya; Mitsuro (Nara, JP);
Oshima; Mitsuaki (Kyoto, JP);
Nishioka; Akihiko (Osaka, JP);
Morioka; Koichi (Osaka, JP)
|
| Assignee:
|
Matsushita Electric Industrial Co., Ltd. (Osaka, JP)
|
| Appl. No.:
|
615853 |
| Filed:
|
July 10, 2003 |
Foreign Application Priority Data
| Oct 13, 1999[JP] | P11-290664 |
| Current U.S. Class: |
369/53.21; 369/47.19; 369/47.21; 369/275.4 |
| Intern'l Class: |
G11B 007/00 |
| Field of Search: |
369/5321,471.9,472.1,275.4,275.1,471.2
|
References Cited [Referenced By]
U.S. Patent Documents
| 5541904 | Jul., 1996 | Fite et al.
| |
| 5761301 | Jun., 1998 | Oshima et al.
| |
| 5807640 | Sep., 1998 | Ueno et al.
| |
| 5815484 | Sep., 1998 | Smith et al.
| |
| 5818812 | Oct., 1998 | Moribe et al.
| |
| 5881038 | Mar., 1999 | Oshima et al.
| |
| 6052465 | Apr., 2000 | Gotoh et al.
| |
| 6070799 | Jun., 2000 | Ashe.
| |
| Foreign Patent Documents |
| 1173942 | Feb., 1998 | CN.
| |
| 0 802 527 | Oct., 1997 | EP.
| |
| 0 807 929 | Nov., 1997 | EP.
| |
| 0 932 147 | Jul., 1999 | EP.
| |
| 61-178732 | Aug., 1986 | JP.
| |
| 7-85574 | Mar., 1995 | JP.
| |
| 8-55430 | Feb., 1996 | JP.
| |
| 9616401 | May., 1996 | WO.
| |
Primary Examiner: Ometz; David L.
Assistant Examiner: Ortiz Criado; J. L.
Attorney, Agent or Firm: Wenderoth, Lind & Ponack, L.L.P.
Parent Case Text
This application is a divisional application of Ser. No. 09/677,595, filed Oct.
3, 2000, now U.S. Pat. No. 6,661,768.
Claims
1. An apparatus for reproducing information recorded on an optical disk which
is provided for recording data of a signal modulated according to a predetermined
modulation method in a form of concavo-convex pits, said optical disk comprising
a first area having a reflecting film partly removed, and a second area for recording
pits which are different from pits satisfying requirements of said predetermined
modulation method, said apparatus comprising:
a first area detecting circuit for detecting said first area in accordance with
a reproduced signal from said optical disk upon reproducing information recorded
in said first area, and outputting a first detecting signal;
a second area detecting circuit for detecting said second area in accordance
with a reproduced signal from said optical disk upon reproducing information recorded
in said second area, and outputting a second detecting signal; and
judging means for judging whether or not the information recorded on said optical
disk should be reproduced, in accordance with said first and second detecting signals,
wherein said second area detecting circuit comprises:
a first comparator for comparing the reproduced signal from said optical disk
upon reproducing information recorded in said second area, with a predetermined
first threshold value, and outputting a first comparison result signal;
a second comparator for comparing the reproduced signal from said optical disk
upon reproducing information recorded in said second area, with a predetermined
second threshold value, and outputting a second comparison result signal; and
an arithmetic logic circuit for performing a logic operation between said first
comparison result signal and said second comparison result signal, and outputting
a logic operation result signal,
wherein said first area detecting circuit judges whether or not said first area
is detected in accordance with whether or not a first number of data from a predetermined
sector address to said detected first area, which is counted based on the reproduced
signal from said optical disk upon reproducing information recorded on a track
including said first area, substantially coincides with a second number of data
from said predetermined sector address to said detected first area, which is counted
based on a reproduced signal from said optical disk upon reproducing information
recorded on a further track including said first area and adjacent to said track.
2. An apparatus for reproducing information recorded on an optical disk which
is provided for recording data of a signal modulated according to a predetermined
modulation method in a form of concavo-convex pits, said optical disk comprising
a first area having a reflecting film partly removed, a second area for recording
pits which are different from pits satisfying requirements of said predetermined
modulation method, a first area location information recording area for recording
location information of said first area on said optical disk, and a second area
location information recording area for recording location information of said
second area on said optical disk, said apparatus comprising:
a first detecting window generating circuit for generating a first detecting
window signal in accordance with said location information of said first area on
said optical disk recorded in said first area location information recording area;
a second detecting window generating circuit for generating a second detecting
window signal in accordance with said location information of said second area
on said optical disk recorded in said second area location information recording
area;
a first area detecting circuit for detecting said first area in accordance with
a reproduced signal from said optical disk upon reproducing information recorded
in said first area, and outputting a first detecting signal;
a second area detecting circuit for detecting said second area in accordance
with a reproduced signal from said optical disk upon reproducing information recorded
in said second area, and outputting a second detecting signal; and
judging means for judging whether or not the information recorded on said optical
disk should be reproduced, in accordance with said first detecting signal in a
valid time interval of said first detecting window signal, and said second detecting
signal in a valid time interval of said second detecting window signal,
wherein said second area detecting circuit comprises:
a first comparator for comparing the reproduced signal from said optical disk
upon reproducing information recorded in said second area, with a predetermined
first threshold value, and outputting a first comparison result signal;
a second comparator for comparing the reproduced signal from said optical disk
upon reproducing information recorded in said second area, with a predetermined
second threshold value, and outputting a second comparison result signal; and
an arithmetic logic circuit for performing a logic operation between said first
comparison result signal and said second comparison result signal, and outputting
a logic operation result signal,
wherein said first area detecting circuit judges whether or not said first area
is detected in accordance with whether or not a first number of data from a predetermined
sector address to said detected first area, which is counted based on the reproduced
signal from said optical disk upon reproducing information recorded on a track
including said first area, substantially coincides with a second number of data
from said predetermined sector address to said detected first area, which is counted
based on a reproduced signal from said optical disk upon reproducing information
recorded on a further track including said first area and adjacent to said track.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disk for recording copyrighted content
information, and a method and an apparatus for reproducing copyrighted content
information recorded in an optical disk.
2. Description of the Related Art
In recent multimedia societies, optical disks such as a CD-ROM and a DVD have
become remarkably widespread. With the widespread use of the optical disks, so-called
pirated ROM disks have appeared and allow a pirate to benefit from the disk without
compensating a copyright owner by fraud by illegally making a pirated copy of the
optical disk. The percentage of pirated copies of disks is rapidly increasing.
Illegal copying of the optical disk can take place in the following manner. Generally
speaking, a pirate purchases an authorized optical disk, makes a master tape by
reproducing information recorded on the optical disk by means of a disk drive,
and mass-produces the pirated copies from the master tape by the same method as
a general disk manufacturing method.
In order to protect against the above-mentioned unauthorized copying, some optical
disks are devised so that they can be reproduced by only a player designed specifically
for them. As this type of optical disk, for example, there is disclosed in the
Japanese Patent Laid-Open Publication No 7-85574 a method including the steps of
recording main information on an optical recording medium using a predetermined
coding means, storing key information indicating decoding means for decoding the
main information in a form of a barcode symbol in a mirror surface area or the
like, reading our the key information by a reproducing apparatus, decoding and
reproducing the main information utilizing a coding method indicated by the key information.
The above-mentioned method of protecting against unauthorized copying has such
a very excellent advantage that a general optical disk player cannot reproduce
the optical disk. However, the method is helpless against and cannot protect against
copying means for performing copying involving no reproducing operation, i.e.,
for physically copying or transferring concavo-convex pits of data of a signal
recorded on an optical disk surface as they are. This copying method requires no
reproducing means, and can copy concavo-convex pit information of the optical disk
as it is even though original data of signal to be recorded on the optical disk
is made sophisticated and complicated. Therefore, the above mentioned method of
protecting against unauthorized copying is useless.
SUMMARY OF THE INVENTION
An essential object of the present invention is, therefore, to provide an optical
capable of protecting against copying means for physically copying concavo-convex
pits of data of a signal recorded on an optical disk surface as they are.
Another object of the present invention is to further provide a method and
apparatus for reproducing information recorded on the optical disk capable of protecting
against copying means for physically copying concavo-convex pits of data of a signal
recorded on an optical disk surface as they are.
In order to achieve the aforementioned objective, according to one aspect of
the
present invention, there is provided an optical disk for recording data of a signal
modulated according to a predetermined modulation method in a form of concavo-convex
pits, the optical disk comprising:
a first area having a reflecting film partly removed; and
a second area for recording pits which are different from pits satisfying requirements
of the predetermined modulation method.
According to another aspect of the present invention, there is provided
an optical disk for recording data of a signal modulated according to a predetermined
modulation method in a form of concavo-convex pits, the optical disk comprising:
a first area having a reflecting film partly removed;
a second area for recording pits which are different from pits satisfying requirements
of the predetermined modulation method;
a first area location information recording area for recording location information
of the first area on the disk; and
a second area location information recording area for recording location information
of the second area on the disk.
In the above-mentioned optical disk, the first area having the reflecting film
partly removed is preferably included in a user data recording area for recording
user data therein.
In the above-mentioned optical disk, the first area having the reflecting film
partly removed preferably includes a portion, which is formed by removing the reflecting
film, and which has a length longer than a maximum pit length determined by the
requirements of the modulation method, in a circumferential direction of the optical disk.
In the above-mentioned optical disk, each of the pits recorded in the second
area
is preferably longer than a maximum pit length determined by the modulation method.
In the above-mentioned optical disk, each of the pits recorded in the second
area
is preferably longer than a maximum pit length determined by the modulation method, and
wherein edges in the center of each of the pits recorded in the second area
are inclined more gradually than edges in an end portion of each of the pits.
In the above-mentioned optical disk, the first area location information recording
area and the second area location information recording area are preferably recorded
in an area except for a user data recording area for recording user data therein.
According to a further aspect of the present invention, there is provided
a method for reproducing information recorded on an optical disk which is provided
for recording data of a signal modulated according to a predetermined modulation
method in a form of concavo-convex pits, the optical disk comprising a first area
having a reflecting film partly removed, and a second area for recording pits which
are different from pits satisfying requirements of the predetermined modulation
method, the method including the steps of:
detecting an area having the reflecting film partly removed, in accordance
with a reproduced signal of the first area;
detecting a pit which is different from the pit satisfying the requirements
of the predetermined modulation method, in accordance with a reproduced signal
of the second area; and
judging whether or not the information recorded on the optical disk should
be reproduced, in accordance with results detected by the two steps of detecting.
According to a still further aspect of the present invention, there is
provided a method for reproducing information recorded on an optical disk which
is provided for recording data of a signal modulated according to a predetermined
modulation method in a form of concavo-convex pits, the optical disk comprising
a first area having a reflecting film partly removed, a second area for recording
pits which are different from pits satisfying requirements of the predetermined
modulation method, a first area location information recording area for recording
location information of the first area on the disk, and a second area location
information recording area for recording location information of the second area
on the disk, the method including the steps of:
reproducing information recorded in the first area in accordance with
the location information of the first area on the disk recorded in the first area
location information recording area, and outputting a reproduced signal of the
first area;
reproducing information recorded in the second area in accordance with
the location information of the second area on the disk recorded in the second
area location information recording area, and outputting a reproduced signal of
the second area;
detecting an area having the reflecting film partly removed, in accordance
with the reproduced signal of the first area;
detecting a pit which is different from the pit satisfying the requirements
of the predetermined modulation method, in accordance with the reproduced signal
of the second area; and
judging whether or not the information recorded on the optical disk should
be reproduced, in accordance with results detected by the two steps of detecting.
In the above-mentioned method, the step of reproducing information recorded in
the first area preferably includes the step of reproducing information recorded
in the first area in a defocus state.
In the above-mentioned method, the step of reproducing information recorded in
the first area preferably includes the step of reproducing the information recorded
in the first area by performing tracking an area located between two adjacent tracks.
In the above-mentioned method, the step of detecting the area having the reflecting
film partly removed preferably includes the step of detecting whether or not the
reflecting film is removed on the two adjacent tracks.
According to a still further aspect of the present invention, there is
provided an apparatus for reproducing information recorded on an optical disk which
is provided for recording data of a signal modulated according to a predetermined
modulation method in a form of concavo-convex pits, the optical disk comprising
a first area having a reflecting film partly removed, and a second area for recording
pits which are different from pits satisfying requirements of the predetermined
modulation method, the apparatus comprising:
a first area detecting circuit for detecting the first area in accordance with
a reproduced signal from the optical disk upon reproducing information recorded
in the first area, and outputting a first detecting signal;
a second area detecting circuit for detecting the second area in accordance with
a reproduced signal from the optical disk upon reproducing information recorded
in the second area, and outputting a second detecting signal; and
judging means for judging whether or not the information recorded on the
optical disk should be reproduced, in accordance with the first and second detecting signals.
According to a still further aspect of the present invention, there is
provided an apparatus for reproducing information recorded on an optical disk which
is provided for recording data of a signal modulated according to a predetermined
modulation method in a form of concavo-convex pits, the optical disk comprising
a first area having a reflecting film partly removed, a second area for recording
pits which are different from pits satisfying requirements of the predetermined
modulation method, a first area location information recording area for recording
location information of the first area on the disk, and a second area location
information recording area for recording location information of the second area
on the disk, the apparatus comprising:
a first detecting window generating circuit for generating a first detecting
window
signal in accordance with the location information of the first area on the disk
recorded in the first area location information recording area;
a second detecting window generating circuit for generating a second detecting
window signal in accordance with the location information of the second area on
the disk recorded in the second area location information recording area;
a first area detecting circuit for detecting the first area in accordance with
a reproduced signal from the optical disk upon reproducing information recorded
in the first area, and outputting a first detecting signal;
a second area detecting circuit for detecting the second area in accordance with
a reproduced signal from the optical disk upon reproducing information recorded
in the second area, and outputting a second detecting signal; and
judging means for judging whether or not the information recorded on the
optical disk should be reproduced, in accordance with the first detecting signal
in a valid time interval of the first detecting window signal, and the second detecting
signal in a valid time interval of the second detecting window signal.
In the above-mentioned apparatus, the first area detecting circuit preferably
comprises a first comparator for comparing the reproduced signal from the optical
disk upon reproducing information recorded in the first area, with a predetermined
first threshold value, and outputting a first comparison result signal.
In the above-mentioned apparatus, the second area detecting circuit preferably comprises:
a second comparator for comparing the reproduced signal from the optical disk
upon
reproducing information recorded in the second area, with a predetermined second
threshold value, and outputting a second comparison result signal;
a third comparator for comparing the reproduced signal from the optical disk
upon
reproducing information recorded in the second area, with a predetermined third
threshold value, and outputting a third comparison result signal; and
an arithmetic logic circuit for performing a logic operation between the second
comparison result signal and the third comparison result signal, and outputting
a logic operation result signal.
In the above-mentioned apparatus, the first area detecting circuit preferably
detects the first area in accordance with a reproduced signal from the optical
disk upon reproducing information recorded on a track including the first area,
and a reproduced signal from the optical disk upon reproducing information recorded
on a further track including the first area and adjacent to the track, and outputs
the first detecting signal.
According to a further aspect of the present invention, there is provided
a method for reproducing information recorded on an optical disk which is provided
for recording data of a signal modulated according to a predetermined modulation
method in a form of concavo-convex pits, the optical disk comprising a first area
having a reflecting film partly removed, the method including the steps of:
detecting the first area in accordance with a reproduced signal from the
optical disk upon reproducing information recorded in the first area, and outputting
a first detecting signal; and
judging whether or not the information recorded on the optical disk should
be reproduced, in accordance with the first detecting signal.
In the above-mentioned method, the step of detecting the first area and outputting
the first detecting signal preferably includes the step of:
detecting the first area in accordance with a reproduced signal from the
optical disk upon reproducing information recorded on a track including the first
area, and a reproduced signal from the optical disk upon reproducing information
recorded on a further track including the first area and adjacent to the track,
and outputting the first detecting signal.
In the above-mentioned method, the step of detecting the first area and outputting
the first detecting signal preferably includes the step of:
judging whether or not the first area is detected in accordance with whether
or not a first number of data from a predetermined sector address to the detected
first area, which is counted based on the reproduced signal from the optical disk
upon reproducing information recorded on the track including the first area, substantially
coincides with a second number of data from the sector address to the detected
first area, which is counted based on the reproduced signal from the optical disk
upon reproducing information recorded on a further track including the first area
and adjacent to the track.
According to a still further aspect of the present invention, there is
provided an apparatus for reproducing information recorded on an optical disk which
is provided for recording data of a signal modulated according to a predetermined
modulation method in a form of concavo-convex pits, the optical disk comprising
a first area having a reflecting film partly removed, the apparatus comprising:
detecting means for detecting the first area in accordance with a reproduced
signal from the optical disk upon reproducing information recorded in the first
area, and outputting a first detecting signal; and
judging means for judging whether or not the information recorded on the
optical disk should be reproduced, in accordance with the first detecting signal.
In the above-mentioned apparatus, the detecting means preferably detects the
first
area in accordance with a reproduced signal from the optical disk upon reproducing
information recorded on a track including the first area, and a reproduced signal
from the optical disk upon reproducing information recorded on a further track
including the first area and adjacent to the track, and outputs the first detecting signal.
In the above-mentioned apparatus, the detecting means preferably judges whether
or not the first area is detected in accordance with whether or not a first number
of data from a predetermined sector address to the detected first area, which is
counted based on the reproduced signal from the optical disk upon reproducing information
recorded on the track including the first area, substantially coincides with a
second number of data from the sector address and the detected first area, which
is counted based on the reproduced signal from the optical disk upon reproducing
information recorded on a further track including the first area and adjacent to
the track.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and features of the present invention will become clear
from the following description taken in conjunction with the preferred embodiments
thereof with reference to the accompanying drawings throughout which like parts
are designated by like reference numerals, and in which:
FIG. 1 is a plan view showing a planar structure of an optical disk 1
according to a first preferred embodiment of the invention;
FIG. 2 is a sectional view showing a sectional structure of the optical disk
1 shown in FIG. 1;
FIG. 3 is a sectional view showing a sectional structure of a first area 2
of the optical disk 1 shown in FIG. 1;
FIG. 4 is an enlarged view showing a second area 3 of the optical disk
1 shown in FIG. 1 and a plan view showing a planar structure of a long pit 107;
FIG. 5 is a sectional view and a block diagram showing a method of forming a
non-reflecting portion 106 of the optical disk 1 shown in FIG. 1;
FIGS. 6A, 6B and 6C show signal waveforms of reproduced signals
which are obtained during reproduction of information in an area of the non-reflecting
portion 106 of the optical disk 1 shown in FIG. 1, in which the signal
waveforms are proportional to the intensity of reflected light relative to a circumferential
length, wherein FIG. 6A is a waveform chart of the signal waveform of the reproduced
signal at a low degree of modulation, FIG. 6B is a waveform chart of the signal
waveform of the reproduced signal at a high degree of modulation, and FIG. 6C is
a waveform chart of the signal waveform of the reproduced signal at a high degree
of modulation and in a defocus state;
FIG. 7 is a block diagram showing a configuration of a first area detecting
circuit 23
a for use in the first preferred embodiment of the invention;
FIG. 8 is a plan view showing a planar structure of the long pit 107
formed in the second area 3 of the optical disk 1 shown in FIG. 1;
FIGS. 9A and 9B show a sectional structure of the long pit 107 shown
in FIG. 8, wherein FIG. 9A is a sectional view taken along the line A-A′
of FIG. 8 located in the center of the long pit 107, and FIG. 9B is a sectional
view taken along the line B-B′ of FIG. 8 located in an end portion of the
long pit 107;
FIG. 10 is a block diagram showing a configuration of a second area detecting
circuit 24
a for use in the first preferred embodiment of the invention;
FIGS. 11A, 11B and 11C show a method of detecting the second
area by the second area detecting circuit 24
a shown in FIG. 10, wherein
FIG. 11A is a waveform chart of a signal waveform of a reproduced signal in an
area including the area of the long pit 107, FIG. 11B is a waveform chart
of a signal waveform of an output signal CV1 from a comparator 8
shown in FIG. 10, which uses a first threshold value voltage V1th, and FIG.
11C is a waveform chart of a signal waveform of an output signal CV2 from
a comparator 9 shown in FIG. 10, which uses a second threshold value voltage V2th;
FIG. 12 shows a table of waveform charts of signal waveforms of reproduced signals
which are obtained during reproduction of information in the area of the non-reflecting
portion 106 and the area of the long pit 107 on each optical disk,
where FIG. 12(
a) shows waveform charts of the signal waveforms of
the reproduced signals which are obtained during reproduction of information in
the area of the non-reflecting portion 106 and the area of the long pit
107 on the authorized optical disk 1 according to the first preferred
embodiment of the invention, FIG. 12(
b) shows waveform charts of
the signal waveforms of the reproduced signals which are obtained during reproduction
of information in the area of the non-reflecting portion 106 and the area
of the long pit 107 on a first pirated optical disk, and FIG. 12(
c)
shows waveform charts of the signal waveforms of the reproduced signals which are
obtained during reproduction of information in the area of the non-reflecting portion
106 and the area of the long pit 107 on a second pirated optical disk;
FIG. 13 is a plan view showing a planar structure of an optical disk 1
a
according to a second preferred embodiment of the invention;
FIG. 14 is a block diagram showing a configuration of a first area detecting
circuit 23 for use in the second preferred embodiment of the invention;
FIG. 15 is a block diagram showing a configuration of a second area detecting
circuit 24 for use in the second preferred embodiment of the invention;
FIG. 16 is a block diagram showing a configuration of an optical disk reproducing
apparatus for use in a third preferred embodiment of the invention;
FIG. 17 shows a method of detecting the first area 2 for use in the optical
disk reproducing apparatus shown in FIG. 16 and is an enlarged plan view
showing the correlation from each track on the optical disk 1 in a circumferential
direction to the first area 2;
FIG. 18 is a flow chart of a first portion of processing for detecting and judging
the first area to be executed by a system controller 25 shown in FIG. 16; and
FIG. 19 is a flow chart of a second portion of the processing for detecting
and judging the first area to be executed by the system controller 25 shown
in FIG. 16.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An optical disk, an optical disk reproducing method and an optical disk reproducing
apparatus according to preferred embodiments of the invention will be described
below with reference to the accompanying drawings. Herein, optical disks include
an optical disk and a magneto-optical disk such as a CD, a video CD, a CD-ROM,
a CD-R, a CD-RW, an MD, a DVD, a DVD-ROM, a DVD-RAM and a DVD-RW.
First Preferred Embodiment
FIG. 1 is a plan view showing a planar structure of an optical disk
1
according to a first preferred embodiment of the invention, FIG. 2 is a sectional
view showing a sectional structure of the optical disk
1 shown in FIG. 1,
FIG. 3 is a sectional view showing a sectional structure of a first area
2
of the optical disk
1 shown in FIG. 1, and FIG. 4 is an enlarged view showing
a second area
3 of the optical disk
1 shown in FIG. 1 and a plan
view showing a planar structure of a long pit
107.
FIG. 1 shows a planar structure of an information recording area of the overall
optical disk
1. The information recording area comprises a lead-in area
111 for recording control information, a data recording area
112
that is a user data recording area for recording content information composed of
content control information and content data, and a lead-out area
113. The
optical disk
1 has a rotation driving hole
1h in the center
thereof. The lead-in area
111, the data recording area
112 and the
lead-out area
113 are located in an order from the inside of the optical
disk
1 toward the outside thereof. In the data recording area
112,
the first area
2, which will be described later in detail, extends so as
to have a longitudinal direction in a radial direction of the optical disk
1,
while the second area
3, which will be described later in detail, extends
so as to have a longitudinal direction in a circumferential direction of the optical
disk
1.
As shown in FIG. 2, the optical disk
1 is formed of a bonded structure
of a transparent optical disk substrate
100 and an optical disk substrate
102. A reflecting film
101 of a material such as aluminum or gold
is formed, by using the sputtering method which has been already known to those
skilled in the art, on one surface of the transparent optical disk substrate
100
which is formed so that concavo-convex pits are formed thereon based on a replica.
Then, one surface of the optical disk substrate
102 made through another
step is bonded onto the surface of the transparent optical disk substrate
100
on which the reflecting film
101 is formed, using an adhesive layer
103
made of an ultraviolet-curing resin which is located between the two optical disk
substrates
100 and
102. After that, the bonded optical disk substrates
100 and
102 are irradiated with ultraviolet rays, and this leads
to the adhesive layer
103 being allowed to cure and thus the two optical
disk substrates
100 and
102 are firmly bonded to each other. As a
result, the optical disk
1 is made.
FIG. 3 shows a sectional structure of the first area
2 having a non-reflecting
portion
106 formed by partly removing the reflecting film
101 in
the optical disk
1 shown in FIG. 1. A method of making the non-reflecting
portion
106 is disclosed in International Publication No. WO96/16401. With
reference to the publication, the method of making the non-reflecting portion
106
will be briefly described with reference to FIG.
5. The optical disk
1
completed by the method described above with reference to FIG. 2 is irradiated
on the side of the transparent optical disk substrate
100 with pulse laser
light emitted from a YAG pulse laser
104 so that the pulse laser light is
focused on the reflecting film
101 by a condenser lens
105. Thus,
the reflecting film
101 is partly removed. As a consequence, the non-reflecting
portion
106 is formed in the first area
2.
FIGS. 6A to
6C show signal waveforms of reproduced signals which are
obtained during reproduction of information in an area of the non-reflecting portion
106 of the optical disk
1 shown in FIG.
1. In this case, the
signal waveforms are proportional to the intensity of reflected light relative
to a circumferential length. FIG. 6A is a waveform chart of the signal waveform
of the reproduced signal at a low degree of modulation, FIG. 6B is a waveform chart
of the signal waveform of the reproduced signal at a high degree of modulation,
and FIG. 6C is a waveform chart of the signal waveform of the reproduced signal
at a high degree of modulation and in a defocus state.
When information recorded in the first area
2 of the optical disk
1
configured as described above with reference to FIG. 5 is reproduced by using the
optical disk reproducing apparatus, there are obtained the signal waveforms of
the reproduced signals including RF signals changing periodically as shown in FIGS.
6A to
6C. At a low degree of modulation, a dark level of the periodic RF
signal does not drop sufficiently. In this case, the dark level refers to the darkest
level of an envelope of the RF signal, and is called an envelope bottom level.
Therefore, as shown in FIG. 6A, the level of the reproduced signal in the area
of the non-reflecting portion
106 is compared with a threshold value, namely,
a first slice level that is lower than the envelope bottom level of the RF signal
by a predetermined amount of level shift, and then, the presence of the non-reflecting
portion
106 can be detected.
At a high degree of modulation, as shown in FIG. 6B, the envelope bottom level
of the RF signal drops sufficiently. Thus, little or no difference is made between
the envelope bottom level of the RF signal and an output level of the non-reflecting
portion
106. Therefore, it is not easy to detect the non-reflecting portion
106. However, in this case, an optical head, i.e., an optical pickup of
the optical disk reproducing apparatus is controlled so that a spot of the Laser
light to be applied to the optical disk
1 becomes in a defocus state. Thus,
the envelope bottom level of the reproduced RF signal rises, and therefore, a significant
difference is made between the envelope bottom level of the RF signal and the level
of the reproduced signal in the area of the non-reflecting portion
106.
Consequently, the area of the non-reflecting portion
106 can be easily detected.
In actuality, when an attempt is made to make the spot of the laser light on the
optical disk
1 be in a defocus state and to reproduce information recorded
on the optical disk
1, a reproduced clock signal, which is to be generated
from the reproduced signal by a PLL circuit in an analog processor, cannot be,
in some cases, generated. Therefore, in some cases, the PLL circuit is held immediately
before the spot of the laser light is made in a defocus state, and the analog processor
is controlled so as to hold and reproduce the reproduced clock signal in a state
immediately before the defocus state.
Furthermore, it may be a possible method to reproduce information recorded
in the first area
2 by performing tracking of an area located between two
adjacent tracks on the optical disk
1. In this case, in a manner similar
to above, the envelope bottom level, i.e., the dark level of the RE signal rises
in any area other than the non-reflecting portion
106, however, the reproduced
clock signal cannot be generated due to cross-talk between the RE signals. Thus,
a reproduced clock immediately before tracking between the tracks is held and reproduced
in a state immediately before tracking.
FIG. 7 is a block diagram showing a configuration of a first area detecting
circuit
23a for use in the first preferred embodiment of the invention.
The first area detecting circuit
23a comprises a data slicer
4,
an envelope bottom detecting circuit
5, a level shift circuit
6,
and a comparator
7.
Referring to FIG. 7, the reproduced signal outputted from an analog processor
20 of FIG. 16 for applying analog signal processing to the reproduced signal
from the optical disk
1 is inputted to the data slicer
4, a first
input terminal of the comparator
7 and the envelope bottom detecting circuit
5. The data slicer
4 binarizes the reproduced signal, which is inputted
from the optical disk
1 through the analog processor
20, by using
a predetermined threshold value. Thus, the data slicer
4 converts the reproduced
signal into digital data, i.e., a binarized reproduced signal, and then, outputs
the binarized reproduced signal. On the other hand, the envelope bottom detecting
circuit
5 detects the envelope bottom level that is the lowest level of
the envelope of the input reproduced signal, and then, outputs a low envelope signal
having the detected envelope bottom level to the level shift circuit
6.
Subsequently, the level shift circuit
6 shifts downward the envelope bottom
level of the input low envelope signal by a predetermined amount of level shift
(See FIGS.
6A and
6C), and then, outputs a threshold value signal
having the above-mentioned level-shifted first slice level to a second input terminal
of the comparator
7. Furthermore, the comparator
7 compares the reproduced
signal inputted to the first input terminal with the threshold value signal having
the first slice level inputted to the second input terminal. When the level of
the reproduced signal is lower than the first slice level, i.e., in the area of
the non-reflecting portion
106, the comparator
7 outputs a low-level
signal as a non-reflecting portion detecting signal. In the above-mentioned manner,
the area of the non-reflecting portion
106 in the first area
2 having
the reflecting film partly removed can be easily detected.
Next, description will be made with regard to the second area
3 having
a concavo-convex long pit
107 having a length longer than a maximum pit
length determined by a predetermined modulation method, i.e., having a length which
is different from concavo-convex pits satisfying the above-mentioned modulation
method. As shown in the planar structures of FIGS. 4 and 8, the long pit
107
having a length equivalent to about 100T in the longitudinal direction parallel
to the circumferential direction is formed in the second area
3, for example,
provided that a pit length for generally recording user data in the data recording
area
112 is 3T to 14T (where T denotes a length corresponding to one reproduced
clock signal). FIGS. 9A and 9B show a sectional structure of the long pit
107
shown in FIG.
8. FIG. 9A is a sectional view taken along the line A-A′
of FIG. 8 located in the center of the long pit
107. FIG. 9B is a sectional
view taken along the line B-B′ of FIG. 8 located in an end portion of the
long pit
107.
As shown in FIGS. 9A and 9B, the long pit
107 has a sectional structure
in which the curvature of each edge of a cross section of the long pit
107
is larger at the position closer to the circumferential, i.e., longitudinal center
(referring to a portion located at the midpoint position between both end portions
in the longitudinal direction). The cross section in the center of the long pit
107 has a sectional shape shown in FIG.
9A. The cross sections in
both the end portions of the long pit
107 have a sectional shape shown in
FIG.
9B. The long pit
107 having the above-mentioned sectional shape
can be easily formed by appropriately setting conditions for forming the transparent
optical disk substrate
100 of the optical disk
1, as well known.
FIG. 11A shows a signal waveform of a reproduced signal which is obtained when
information recorded in the second area
3 is reproduced in the circumferential
direction. The horizontal axis shown in FIGS. 11A,
11B and
11C represents
the elapsed time corresponding to the circumferential length when information recorded
in the second area
3 is reproduced in the circumferential direction by moving
the spot of the laser light to be applied to the optical disk
1 at a constant speed.
As shown in FIG. 11A, as the spot of the laser light to be applied to the optical
disk
1 is moved from one end of the long pit
107 to the longitudinal
center of the long pit
107 in the circumferential direction, the level of
the reproduced signal rises toward a bright level with a gradual gradient, and
then, the level of the reproduced signal reaches the brightest level in the area
of the long pit
107 in the longitudinal center of the long pit
107.
Furthermore, as the spot of the laser light to be applied to the optical disk
1
is moved from the center of the long pit
107 to the other end of the long
pit
107 in the circumferential direction, the level of the reproduced signal
drops toward the dark level with a gradual gradient. The level of the reproduced
signal changes in the area of the long pit
107 as mentioned above for the
following reason. As shown in FIG. 9A, the curvature of the edge of the long pit
107 in which interference occurs is larger in the center of the long pit
107, thus a substantial pit depth D is not equal to a specified value, i.e.,
λ/4 (where λ denotes an average wavelength of the laser light from
an optical head
18), and, therefore, the level of the reproduced signal
rises to the bright level.
Next, a method of identifying the second area
3 will be described with
reference to FIGS. 10,
11A,
11B and
11C. FIG. 10 is a block
diagram showing a configuration of a second area detecting circuit
24a
for use in the first preferred embodiment of the invention. FIGS. 11A to
11C
show a method of detecting the second area by the second area detecting circuit
24a shown in FIG.
10. FIG. 11A is a waveform chart of a signal
waveform of a reproduced signal in an area including the area of the long pit
107.
FIG. 11B is a waveform chart of a signal waveform of an output signal CV
1
from a comparator
8 shown in FIG. 10, which uses a first threshold value
voltage V
1th close to the bright level. FIG. 11C is a waveform chart of
a signal waveform of an output signal CV
2 from a comparator
9 shown
in FIG. 10, which uses a second threshold value voltage V
2th close to the
dark level.
Referring to FIG. 10, the second area detecting circuit
24a comprises
the data slicer
4, the two comparators
8 and
9, two threshold
value voltage generators
8a and
9a, two counters
10
and
11, and a normal length pit discriminating circuit
12. In FIG.
10, the same components as the components shown in FIG. 7 are indicated by the
same reference numerals.
Referring again to FIG. 10, the reproduced signal outputted from the analog
processor
20 of FIG. 16 for applying analog signal processing to the reproduced
signal from the optical disk
1 is inputted to the data slicer
4 and
the respective first input terminals of the two comparators
8 and
9.
The data slicer
4 binarizes the reproduced signal, which is inputted from
the optical disk
1 through the analog processor
20, by using a predetermined
threshold value. Thus, the data slicer
4 converts the reproduced signal
into digital data, i.e., a binarized reproduced signal, and then, outputs the binarized
reproduced signal. On the other hand, the first threshold value voltage V
1th
from the threshold value voltage generator
8a is inputted to a second
input terminal of the comparator
8. The comparator
8 compares the
reproduced signal inputted to the first input terminal to the first threshold value
voltage V
1th close to the bright level, and then, outputs a comparison result
signal to the counter
10. When the level of the reproduced signal is equal
to or higher than the first threshold value voltage V
1th, the comparator
8 outputs a high-level comparison result signal. In the other cases, the
comparator
8 outputs a low-level comparison result signal. Moreover, the
second threshold value voltage V
2th from the threshold value voltage generator
9a is inputted to a second input terminal of the comparator
9.
The comparator
9 compares the reproduced signal inputted to the first input
terminal with the second threshold value voltage V
2th close to the dark
level, and then, outputs a comparison result signal to the counter
11. When
the level of the reproduced signal is equal to or higher than the second threshold
value voltage V
2th, the comparator
9 outputs a high-level comparison
result signal. In the other cases, the comparator
9 outputs a low-level
comparison result signal.
Each of the counters
10 and
11 counts channel bit clock signals
pck which are reproduced from the reproduced signals by the analog processor
20,
during a valid time interval during which the input comparison result signal is
at high level. Then, each of the counters
10 and
11 outputs time
data of a count result (corresponding to the time interval T
1 shown in FIG.
11B and the time interval T
2 shown in FIG. 11C during which the comparison
result signal is at high level) to the normal length pit discriminating circuit
12. Subsequently, when the time interval T
2 shown in FIG. 11C is
equal to or longer than a predetermined first threshold time and the time interval
between the start of the time interval T
2 (the leading edge of a pulse of
the high-level comparison result signal in the time interval T
2 in the area
of the long pit
107) and the start of the time interval T
1 (the leading
edge of a pulse of the high-level comparison result signal in the time interval
T
1 in the area of the long pit
107) is equal to or longer than a
predetermined second threshold time, the normal length pit discriminating circuit
12 judges that the presence of the long pit
107, i.e., the presence
of the second area
3 is detected, and then, the circuit
12 outputs
a long pit detecting signal.
In the case of a typical normal pit, in a form of which data of a signal modulated
according to using a predetermined modulation method is recorded on the optical
disk
1, the reproduced level of the normal pit abruptly or suddenly changes
from the dark level to the bright level, and the time interval for the change is
substantially fixed. However, the reproduced level of the above-mentioned long
pit
107 gradually changes from the dark level to the bright level with a
more gradual gradient than the gradient of change in the typical normal pit. Therefore,
the long pit
107 or the second area
3 can be easily detected by using
the above-described method, i.e., by using the second area detecting circuit
24a
shown in FIG.
10.
Description will be made with regard to the case in which a pirate makes
a so-called RF copy of the optical disk
1 as configured as described above.
"RF copying" described herein refers to making a copy of the optical disk is made
by using a stamper made by the use of an RF signal that is a reproduced signal
from the optical disk
1.
Description will be made with reference to FIG. 12 with regard to the
case in which the optical disk
1 is made as mentioned above. FIG. 12 shows
a table of waveform charts of signal waveforms of reproduced signals which are
obtained during reproduction of information in the area of the non-reflecting portion
106 and the area of the long pit
107 on each optical disk. FIG.
12(
a)
shows waveform charts of the signal waveforms of the reproduced signals which are
obtained during reproduction of information in the area of the non-reflecting portion
106 and the area of the long pit
107 on the authorized optical disk
1 according to the first preferred embodiment of the invention. FIG.
12(
b)
shows waveform charts of the signal waveforms of the reproduced signals which are
obtained during reproduction of information in the area of the non-reflecting portion
106 and the area of the long pit
107 on a first pirated optical disk
made by RF copying. FIG.
12(
c) shows waveform charts of the signal
waveforms of the reproduced signals which are obtained during reproduction of information
in the area of the non-reflecting portion
106 and the area of the long pit
107 on a second pirated optical disk made under changed conditions from
forming the first pirated optical disk.
In general, the non-reflecting portion
106 of the pirated optical disk,
which is made by making a RF copy of the reproduced signal of the non-reflecting
portion
106 as it is, is recorded as the long pit. The long pit
107
of the authorized optical disk is judged as the presence or absence of the pit,
and thus the long pit
107 of the pirated optical disk is recorded as if
the length of the long pit
107 were reduced.
Therefore, as shown in FIG. 12, when information recorded on the pirated
optical disk is reproduced, the RF signal contains a long-time dark level signal
in an area corresponding to the first area
2 of the authorized optical disk,
and thus, it seems as if the long pit
107 were formed in the above-mentioned
area. However, the signal waveform of the reproduced signal that settles at the
dark level and is continuous (See a column of the area of the non-reflecting portion
106 shown in FIG.
12(
b)), or the signal waveform of the reproduced
signal similar to the reproduced signal of the second area
3 of the authorized
optical disk (See a column of the area of the non-reflecting portion
106
shown in FIG.
12(
c)) is obtained in accordance with the forming conditions.
Information recorded in a portion corresponding to the second area
3
of the authorized optical disk is reproduced as a long bright level sandwiched
between short dark levels. When a pirated, unauthorized optical disk is copied
by using the stamper made by the use of the RF signal, a pit shorter than the normal
long pit
107 is recorded. Moreover, the reproduced level of the shorter
pit changes from the dark level to the bright level more abruptly or suddenly than
the long pit
107 of the authorized optical disk (See a column of the area
of the long pit
107 shown in FIG.
12(
b) and FIG.
12(
c)).
As described above, it is judged whether or not the optical disk is the authorized
opti
