U.S. patent application number 09/963366 was filed with the patent office on 2002-01-31 for information recording medium, information recording method and information recording apparatus.
This patent application is currently assigned to Hitachi, Ltd.. Invention is credited to Hirotsune, Akemi, Minemura, Hiroyuki, Miyamoto, Harukazu, Miyauchi, Yasushi, Terao, Motoyasu.
Application Number | 20020012310 09/963366 |
Document ID | / |
Family ID | 26503014 |
Filed Date | 2002-01-31 |
United States Patent
Application |
20020012310 |
Kind Code |
A1 |
Miyauchi, Yasushi ; et
al. |
January 31, 2002 |
Information recording medium, information recording method and
information recording apparatus
Abstract
A recording medium having a dummy signal area on at least one
side of a recording area is used and information is recorded with a
dummy signal added to at least one of the leading and trailing
sides in the recorded information signal. The user data area
remains unaffected by repeated overwriting so that recorded user
data is reproduced correctly. In particular, the wave form
distortion caused by fluidization of a recording film remains at
the dummy signal area and does not affect the user data area, so
that the reproduction of the target information (user data) is
assured.
Inventors: |
Miyauchi, Yasushi; (Tokyo,
JP) ; Terao, Motoyasu; (Tokyo, JP) ;
Hirotsune, Akemi; (Tokyo, JP) ; Minemura,
Hiroyuki; (Tokyo, JP) ; Miyamoto, Harukazu;
(Tokyo, JP) |
Correspondence
Address: |
MATTINGLY, STANGER & MALUR, P.C.
Suite 370
1800 Diagonald Road
Alexandria
VA
22314
US
|
Assignee: |
Hitachi, Ltd.
|
Family ID: |
26503014 |
Appl. No.: |
09/963366 |
Filed: |
September 27, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09963366 |
Sep 27, 2001 |
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09629867 |
Aug 1, 2000 |
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6317408 |
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09629867 |
Aug 1, 2000 |
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09412787 |
Oct 5, 1999 |
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6111850 |
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09412787 |
Oct 5, 1999 |
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09188370 |
Nov 10, 1998 |
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5974023 |
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09188370 |
Nov 10, 1998 |
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08892657 |
Jul 15, 1997 |
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5878021 |
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08892657 |
Jul 15, 1997 |
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08678070 |
Jul 10, 1996 |
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5703867 |
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Current U.S.
Class: |
369/59.25 ;
369/275.3; G9B/20.027; G9B/7.026; G9B/7.034; G9B/7.038 |
Current CPC
Class: |
G11B 2020/1287 20130101;
G11B 2220/2537 20130101; G11B 7/24 20130101; G11B 20/1217 20130101;
G11B 2220/216 20130101; G11B 2020/1232 20130101; G11B 7/006
20130101; G11B 7/013 20130101; G11B 2020/1288 20130101; G11B
2020/10898 20130101; G11B 7/126 20130101; G11B 2020/1298 20130101;
G11B 7/00454 20130101; G11B 2020/1277 20130101; G11B 7/00745
20130101 |
Class at
Publication: |
369/59.25 ;
369/275.3 |
International
Class: |
G11B 007/24 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 21, 1995 |
JP |
7-185294 |
Dec 13, 1995 |
JP |
7-324200 |
Claims
We claim:
1. An information recording medium on which information is recorded
in a recording area by means of energy beam irradiation,
comprising: a pattern of a dummy signal added to at least one of
the leading and trailing sides of the recording signal which is
recorded in the recording area.
2. An information recording medium as claimed in claim 1, wherein a
postamble is added between user data and the trailing side dummy
signal.
3. An information recording medium as claimed in claim 1, wherein
said recording medium has a phase change recording film.
4. An information recording medium as claimed in claim 3, wherein
said recording film is one of a Ge--Sb--Te system and a
Ag--In--Sb--Te system.
5. An information recording medium as claimed in claim 4, wherein
said recording film contains a high-melting point material selected
from one of Cr--Te and Ag--Te.
6. An information recording medium as claimed in claim 1, wherein,
in order, a protective layer, a recording layer, a protective
layer, a first reflective layer and a second reflective layer are
stacked on a substrate.
7. An information recording medium as claimed in claim 1, wherein
information concerning the pattern of the dummy signal is recorded
in a control data area on the recording medium.
8. An information recording medium as claimed in claim 7, wherein
an information on a pattern of the dummy signal in which the
average recording mark length is shorter than the average space
length between recording marks is written in the control data
area.
9. An information recording medium as claimed in claim 7, wherein
an information on the pattern of a single-frequency dummy signal is
written in a control data area.
10. An information recording medium on which information is
recorded in a recording area by means of energy beam irradiation,
comprising: a dummy area in which information to be recorded by a
dummy signal is added to at least one of the leading and trailing
sides in the recording area in which an information signal is
recorded on the recording medium.
11. An information recording method in which information is
recorded on a recording medium by means of energy beam irradiation,
comprising recording with an energy beam a dummy signal added to at
least one of the leading and trailing sides in the recording
signal.
12. An information recording method as claimed in claim 11, further
comprising using a laser for said recording of said dummy signal,
wherein an average energy of the laser beam during dummy signal
recording is lower than an average energy used to record user data
signal.
13. An information recording method as claimed in claim 11, further
comprising using a laser for said recording of said dummy signal,
wherein in said recording, the dummy signal is recorded with a
single-frequency and wherein the average energy of the laser beam
for said recording of said dummy signal is set lower than an
average energy used to record user data signal by adjusting the
duty ratio of the dummy signal.
14. An information recording method as claimed in claim 13, wherein
the average energy of the laser beam during dummy signal recording
is decreased stepwise or linearly by adjusting the duty ratio of
the dummy signal stepwise or linearly.
15. An information recording method as claimed in claim 11, wherein
a position where the recording of the signal including the dummy
signal starts is shifted at random.
16. An information recording method as claimed in claim 15, wherein
the maximum shift width of the recording start position is shorter
than the length of the dummy signal.
17. An information recording method as claimed in claim 16, wherein
the maximum shift width of the recording start position is in a
range of about {fraction (1/20)}-1/2 of the length of the dummy
signal.
18. An information recording apparatus for recording information by
means of energy beam irradiation, comprising: a laser beam source,
an optical system, automatic focusing (AF) means, tracking means, a
recording medium on which information is recorded in single or
plurality of recording area by means of the laser beam, means for
rotating the recording medium, means for condensing the laser beam
from the laser beam source on the recording medium, signal
modulating means for converting a signal to be recorded into a
modulation code, means for adding a dummy signal or dummy signals
to at least one of leading and trailing sides in the recording
signal, recording waveform generation means for generating a
recording waveform corresponding to a recording signal, recording
start position control means for shifting a recording start
position at random, laser driving means for driving the laser beam
source in accordance with the recording waveform, means for
converting the intensity change of the laser beam reflected from
the recording medium into an electrical signal, means for
amplifying the reproduced electrical signal, conversion-to-binary
means for converting the electrical signal into a binary waveform,
means for decoding the binary signal to make the decoded signal,
means for reading a preformatted header signal, means for deleting
the dummy signal, means for finding control data from said decoded
signal, means for pick up user data from the decoded signal, means
for extracting information on the dummy data pattern, means for
generating dummy data, and means for storing the dummy data
pattern.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an information recording
medium, an information recording method and an information
recording apparatus which are capable of recording such information
in real time by means of recording beams, for example, laser beams
as digital information including pulse-frequency modulated analog
signals of projected images and voice, data in electronic
computers, facsimile signals and digital audio signals. More
particularly, the present invention relates to a disk shaped
recording medium using an erasable, phase-change type optical
recording film.
BACKGROUND OF THE INVENTION
[0002] Conventional phase-change type optical disks have a
recording film capable of fast erasure by crystallization that is
materialized within a time substantially equal to the time required
for a recording laser beam to pass on a point on a disk, for
example. The conventional method of recording and erasing
information to and from such an erasable recording film is to
change the power of the laser beam between two levels higher than
the reading power levels, these levels are a high power level and
an intermediate power level. The advantage of this method is that
the so-called overwriting (replacing old information with new
without prior erasing) is possible. When such overwriting is
repeated a plurality of times, however, the laser beam irradiates
the recording film repeatedly in accordance with the recording
information signal. This results in a high probability of allowing
VFO recording marks to be repeatedly written to the same place in
an area close to a preformat section in particular, and therefore
variations in film thickness tend to occur locally because of
recording film fluidization.
[0003] According to Japanese Unexamined Patent Publication No.
150725/1991, a method that avoids the recording film from being
repeatedly written at the same place involves shifting the data
write start position each time data is written or at appropriate
times when old data is overwritten, whereby mark-forming positions
are properly distributed. Thus the overwriting cyclability of the
optical disk are improved.
SUMMARY OF THE INVENTION
[0004] Even when information is recorded on the phase-change type
optical disk as in the prior art, the fluidization of the overall
recording film inevitably occurs as overwriting is repeated a
plurality of times because the temperature distribution in the
laser beam is asymmetrical. Consequently, a change in the thickness
of the recording film is brought about in that the film becomes
thick on one side and thin on the other side (the initial or
terminal end portion of a recording area taken from the perspective
of the direction of recording) or the film becomes thick at the
center portion of the recording area and thin at the starting and
ending areas, so that the distortion of the reproducing signal
waveform also occurs. The latter type of thickness change is more
difficult to stop. Therefore, there arises a problem of making the
area having the waveform distortion expand as the number of
overwriting times increases. In the case of an erasable digital
video disk, moreover, mark edge recording may be used with both
edges of a recording mark provided with information for the purpose
of increasing density. When such a mark edge recording system is
employed, deterioration due to fluidization is further evident
because a long mark is repeatedly recorded.
[0005] An object of the present invention intended to solve the
foregoing problems in the prior art is to provide an information
recording medium, an information recording method and an
information recording apparatus that ensure reproduced signals
properly corresponding to recorded information signals.
[0006] According to the present invention, a recording medium
capable of recording or overwriting information with a laser beam
is provided. The recording medium has a preformatted area in which
information such as a track address has been formed with pits or
with recording marks resulting from a phase change. In addition to
the preformatted area, a gap area, a recordable area such as a
VFO/SYNC area and a user data area are reserved. Moreover, a dummy
area is provided on at least one of the sides before and after the
recording area. A part of the VFO area can be used instead of the
front dummy area, by making the VFO area long. Further, a buffer
area to allow for a margin for the rotational jitter of a motor is
located just after the dummy area. In this case, one of the
objectives for the provision of the dummy area is to prevent
information actually read from the user data area from being
damaged even though repeated overwriting causes the fluidization of
the recording film. Such damage is prevented because the distortion
of a reproduced signal waveform is confined to the VFO/SYNC area
and/or the dummy area. Further, the dummy area is preferably set to
be longer than the maximum shift width of a position where the
writing of a recorded information signal is started. Further, it is
preferable to add a pit array (data area postamble) depending in
accordance with applicable standards before this dummy area to
avoid the mark and the space from being inverted.
[0007] According to the invention, recording is made by adding a
dummy signal to at least the front or rear side of a target
(recorded) signal such as VFO, SYNC and user data. It is preferable
to add the dummy signal to the rear side (the trailing side with
respect to the direction of recording) when a dummy signal is added
to only one side of the target signal. In this case, the dummy
signal is chiefly recorded in the dummy area.
[0008] Further, according to the invention, the fluidization of the
recording film resulting from repeated overwriting can be moderated
by setting the average energy of the laser beam during dummy signal
recording to be lower than that during the target information
signal recording. Consequently, the distortion of the reproduced
signal waveform due to the fluidization slightly occurs in the
dummy area where the dummy signal is recorded and in part of the
buffer area. However, the recording area where the target signal is
recorded remains unaffected by the fluidization to ensure that a
reproduced signal correctly corresponding to the target signal is
obtained. Collectively, the sum of the dummy area and the buffer
area can be called a buffer area.
[0009] For the recording of the dummy signal, the average energy
thereof may be lowered, for example, by adjusting the duty ratio of
a single-frequency signal. In a mark edge recording system, the
duty ratio of the dummy signal may be set to not greater than 50%
because the average duty ratio is about 50%. The duty ratio of at
least a part of the dummy signal is preferably in a range of at
least 10% to about 40%, and more preferably in a range of at least
20% to about 30%. Moreover, the average energy of the laser beam
during the recording of the dummy signal may be decreased stepwise
or linearly by adjusting the duty ratio of the dummy signal
stepwise or linearly; or otherwise the recording power may be
varied. It is more preferred to vary the duty ratio of the dummy
signal than to vary the recording power in order to simplify the
apparatus. The dummy signal may be added to either the front or
rear side of the recording information signal, that is mainly VFO,
SYNC, and user data, depending on the recording media
characteristics. In the preferred case of adding the dummy signal
to only one side, the dummy signal is added to only the rear side
of the recorded information signal rather than the front side where
the VFO has a function of the dummy signal.
[0010] The distortion level of the reproduced signal waveform can
also be lowered by shifting the start position of writing the
recorded information signal to effect overwriting. In this case,
the maximum shift width is preferably set to be shorter than the
dummy signal that is added; particularly, it is preferably set to
be approximately {fraction (1/20)} to 1/2 of the length of the
recorded dummy signal.
[0011] Also according to the present invention the recording medium
stores thereon information concerning the pattern of the dummy
signal that is used, for example the duty cycle of the dummy
signal. For example, it is preferred that such information be
recorded in the control data area of the recording medium.
[0012] Recording films utilizing a phase change such as recording
films of a Ge--Sb--Te system and a Ag--In--Sb--Te system may be
used according to the present invention. The use of a recording
film containing a high-melting point material such as Cr--Te and
Ag--Te whose melting point is higher than that of the main
component material and a recording medium with an Si/metal double
reflective layer is preferred because the recording film thickness
is further restrained from varying because of fluidization.
[0013] Still further, according to the present invention,
information is recorded by an information recording apparatus
including: a laser beam source, an optical system, automatic
focusing (AF) means, tracking means, reproduced signal detection
means, means to read information in a control data area, a
recording medium on which information on a pattern of a dummy
signal to be added to at least one of the leading or trailing sides
of a recorded information signal is recorded beforehand, means for
rotating or moving the recording medium, means for condensing laser
beams from the laser beam source on the recording medium, signal
modulating means for converting a signal to be recorded into a
modulation code, means for adding the dummy signal as set forth
herein, recording waveform generation means for generating a
recording waveform corresponding to the recording code with the
dummy signal added, recording start position control means for
shifting a recording start position at random (preferably wherein
the maximum shift width of the recording start position, for
example, expressed in a unit of Bytes is shorter than the length of
the dummy signal expressed in a unit of Bytes), laser driving means
for driving the laser beam source in accordance with the recording
waveform, means for converting the intensity change of the laser
beam reflected from the recording medium into an electrical signal,
means for amplifying the reproduced electrical signal, binary
conversion means for converting the electrical signal into a binary
waveform, means for deleting the dummy signal, and means for
decoding the binary signal to make the decoded signal an
information signal (user data).
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a partial sectional view of a disk embodying the
present invention.
[0015] FIG. 2 is a diagram of an exemplary sector format according
to an embodiment of the invention.
[0016] FIG. 3 is a block diagram of an information recording
apparatus according to an embodiment of the invention.
[0017] FIG. 4 is a flow chart showing the steps followed in
generating the dummy data by reading information on the dummy data
pattern from a disk after the disk is inserted in the apparatus of
the invention;
[0018] FIG. 5 is a diagram of an example of the data area postamble
and the dummy data according to the invention; and
[0019] FIGS. 6(a) and 6(b) are diagrams of examples of the dummy
data pattern according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] A detailed description will subsequently be given of the
preferred embodiments of the present invention.
[0021] The recording film for use in the present invention is
preferably a crystal-amorphous phase-change optical recording film
capable of fast crystallization, a recording film utilizing an
amorphous-amorphous change, a crystal-crystal phase-change (e.g. a
change in the crystal system and particle size) recording film or a
magneto-optic recording film. However, any other recording film
which has a tendency to have waveform distortion at the beginning
and/or the end of a recording area may also be used.
[0022] In addition to the preformatted area and a gap area, a
recording area such as the VFO/SYNC area and the user data area
capable of recording information are provided. Moreover, the dummy
area is provided on at least one of the leading or trailing sides
located respectively before and after the recording area, and this
dummy area serves to prevent information actually read from the
data area from being damaged even though repeated overwriting
causes the fluidization of the recording film. The damage is
prevented because the distortion of the regenerative signal
waveform resulting from the fluidization thereof is confined to the
VFO area, the dummy signal and/or the buffer area.
[0023] A description will subsequently be given of the functions in
a case where a recording medium is used in which forward
fluidization (the recording film is fluidized in the same direction
as the direction in which the laser beam proceeds along the surface
of the disk) is caused therein by a plurality of overwritings. The
sector format of the recording medium used herein includes the
preformatted area, the gap area, the front dummy area, the
recording data area, the rear dummy area and the buffer area
arranged in this order. The recording data area is formed with the
VFO/SYNC area and the user data area. At this time, the shift width
at the recording start position is made shorter than the length of
the dummy area to ensure that the recorded information signal is
correctly reproduced. When overwriting is repeated a plurality of
times on the recording medium, fluidization occurs and the
fluidized portion of the recording film moves from the beginning or
leading side to the trailing or ending side of the recording area.
Therefore, the reproduced signal level varies.
[0024] In this recording medium, a reflectance first decreases,
then increases as the recording film becomes thinner and increases
as it becomes thicker. In other words, the reflectance first
decreases then increases on the leading side where the recording
film becomes thin, whereas it increases on the trailing side where
the recording film becomes thick. Therefore, the distortion of the
reproduced signal waveform occurs on the leading and trailing sides
of the recording area, thus causing errors. However, the error
generation resulting from repeated overwriting can be eased by
adding the dummy signal to at least one of the leading or trailing
sides respectively before or after a target information signal such
as the VFO/SYNC and data signal recording area and by making the
average energy of the dummy signal lower than that of the recorded
user data signal. At the time of the reproduction then, only the
reproduced signal waveform corresponding to the user data signal is
reproduced, whereby the user data recording area remains unaffected
by the fluidization even though the reproduced waveform distortion
in the dummy signal area and/or that of the buffer area occur to
ensure that the user data signal is reproduced correctly. Further,
no great distortion is caused in the reproduced signal waveform of
the recorded user data signal even if the number of overwritings
increases.
[0025] In this case, the average energy of the laser beam during
the dummy signal recording may be lowered by, for example,
recording the dummy signal with a single-frequency signal and
decreasing the duty ratio of the signal. In the mark edge recording
system, the duty ratio of the dummy signal may be set to not
greater than 50% because the average duty ratio of the user data is
about 50%. In the case of a disk causing the forward fluidization,
the duty ratio of the dummy signal should preferably be decreased
further to as low as 25%. Moreover, the average energy of the laser
beam during the dummy signal recording may be decreased stepwise or
consecutively by adjusting the duty ratio of the dummy signal
stepwise or linearly; or otherwise, the laser power level may be
varied instead of the duty ratio.
[0026] Although the average laser beam energy can be decreased by
varying the pulse width of the recording waveform and/or the power
that is used, it is preferred to vary the duty ratio of the dummy
signal because the apparatus is simplified. The dummy signal may be
added to either the front (leading) or rear (trailing) side or both
of the recorded information signal as occasion demands. In this
case, the dummy signal may be added to only the rear (trailing)
side of the recorded information signal rather than the front side
thereof where the VFO signal has a similar function as that of the
dummy data signal.
[0027] Although the invention is disclosed with respect to a disk
medium embodiment, any other recording medium in the form of not
only a disk but also a card and the like is applicable to the
present invention.
[0028] FIG. 1 is a partial sectional view of a disk used according
to a preferred embodiment of the invention. First, a ZnS--SiO.sub.2
dielectric layer 2 about 125 nm thick is formed by magnetron
sputtering on a polycarbonate substrate 1 for a continuous tracking
servo, the substrate 1 having a diameter of 5 inches and a
thickness of 0.6 mm. Subsequently, a recording film 3 of
Cr.sub.5Ge.sub.20Sb.sub.20Te.sub.55 is formed to about 30 nm
thickness on the ZnS--SiO.sub.2 dielectric layer 2 and additionally
a ZnS--SiO.sub.2 dielectric layer 4 about 20 nm thick is formed on
the recording film 3. Further, an Si layer 5 is formed to about 100
nm thickness on the dielectric layer 4 and then an Al--Ti-alloy
reflective layer 6 about 100 nm thick is formed on the Si layer
5.
[0029] The formation of these film layers is carried out
successively by one and the same sputtering apparatus. Further, an
ultraviolet-light-hardening resin layer 7 is applied onto the alloy
reflective layer 6 and then a hot-melt adhesive layer 8 is used to
adhere a protective layer 9 securely onto the
ultraviolet-light-hardening resin layer 7. In this case, it is
possible to obtain a bonded disk having a recording capacity twice
as large as that of the above bonded laminate by bonding, in place
of the protective plate 9, another disk as a combination ranging
from the polycarbonate substrate 1 up to the ultraviolet-hardening
resin protective layer 7.
[0030] FIG. 2 shows an example of a sector format of the substrate
used according to the preferred embodiment of the invention. The
sector format includes a preformatted area 10 where information
such as sector and track addresses are formed as uneven pits. In
addition to the preformatted area 10 which is a read-only area, a
gap area 11 and a recording area 14 (group section) such as a
VFO/SYNC area 12 and a user data area 13 capable of being recorded
(including overwriting) with information are provided.
[0031] According to this embodiment of the invention, moreover,
dummy areas 15, 16 are provided at the beginning and the end in the
recording area, respectively. Further, a buffer area 17 providing a
margin for a rotational jitter is also provided behind the dummy
area 16 which follows the recording area. The dummy areas 15, 16
serve to prevent information that is read from the user data area
13 from being damaged even though repeated overwriting causes the
fluidization of the recording film. This damage is prevented
because the distortion of a reproduced signal waveform resulting
from the fluidization thereof is confined to only the front-side
dummy area 15 before the VFO/SYNC area and further because the
distortion of the reproduced signal waveform resulting therefrom is
confine to the rear-side dummy area 16 behind the user data area.
In this case, the dummy areas 15, 16 are set to be longer than the
maximum shift width at a position where the writing of a recording
signal is started, and the rear-side dummy area 16 whose recording
film thickness varies greatly due to the fluidization is set to be
longer than the front-side dummy area 15. According to recording
media characteristics, such a dummy area for restraining the effect
of fluidization may be provided on either front or rear side, and
preferably on the rear side if it is to be provided on only the one
side.
[0032] In this embodiment, a dummy signal is added, as an example,
to both sides of a recorded information signal by a time length of
500 Tw (1 Tw: 90 ns, wherein Tw represents a reproduced signal
detection window width). Further, in this embodiment, a recording
start position is shifted at random within a range of 360 Tw. In
this case, the dummy signal is mainly recorded in the dummy area.
In order to moderate the fluidization of the recording film
resulting from repeated overwriting, moreover, the average energy
of the dummy signal is set to be lower than that of the user data
signal; in other words, affected area by the fluidization is made
to increase gradually.
[0033] In practice, a single-frequency (recording pulse period: 10
Tw) signal is used for the dummy signal and the duty ratio of the
signal is set low. In the case of a mark edge recording method, the
duty ratio becomes substantially equal to 50% in terms of the
average energy when the recording is made at the single frequency.
Consequently, the duty ratio of the dummy signal is preferably not
greater than 50%.
[0034] Since the recording film is fluidized in the same direction
as the direction of the laser beam (forward fluidization) due to
repeated overwriting on the disk of this embodiment according to
the invention, the duty ratio is set as low as 30%. The effect of
adding the dummy signal was noticeable when the duty ratio was at
least 10% and up to and including 40%. The effect was especially
pronounced when the duty ratio was in the range of at least 20% up
to and including 30%, whereby the effect of fluidization of the
recording film was significantly eased with the effect of enlarging
the recording power margin. Moreover, the average energy of the
laser beam during dummy signal recording, may, according to various
conditions, be decreased stepwise or linearly. In this embodiment,
the recording laser pulse corresponding to a recording mark was
divided into a plurality of pulses by a recording waveform
generator. Thus the laser pulse duty was less than 50% even for the
recording of the user data.
[0035] The reproduced signal waveform distortion due to
fluidization has been reduced by randomly shifting the write start
position of the recorded information signal by an amount
approximately equal to {fraction (1/20)} to 1/2 of the dummy signal
area.
[0036] Information on the pattern of the dummy signal (e.g.,
information on a single-frequency pattern in which the average
recording mark length recorded by the dummy signal becomes shorter
than the average space length between the recording marks, etc.) is
recorded with pits beforehand in the control data area of the disk
in this preferred embodiment of the invention; thus recording is
made according to this information.
[0037] Compared to a Ge--Sb--Te or Ag--In--Sb--Te recording film to
which no high-melting point material such as Cr--Te has been added,
a recording film containing a high-melting point material such as
Cr--Te and Ag--Te, for example, Ag.sub.2Te is preferred because the
recording power margin for moderating the fluidization is
attainable to a great extent, though the use of the recording
waveform with the dummy signal added thereto has the effect of
suppressing the effect of fluidization.
[0038] FIG. 3 is an exemplary block diagram of a record playback
system in a record playback apparatus embodying the present
invention. Before the recording, dummy data is generated according
to information stored in the control data concerning the dummy data
pattern, then the dummy data is stored in a memory 41. At the time
of recording, the primary signal to be recorded (user data) is fed
into a modulator 18 in which it is converted into a modulation
code. The dummy data generated and stored in the dummy data memory
41 is read out through the dummy data pattern reading circuit 42
and added to the user data with an adder 43. Further, VFO and SYNC
signals are added with an adder 44. Also, the pulse signal from the
adder is passed through a recording start position controller 20
for shifting a recording start position of the recording signal at
random. Then a recording waveform corresponding to a target
recording code is formed by a recording waveform generator 19
before being output as recording pulse signals. A laser driver 21
modulates the driving current of a semiconductor laser 22. Further,
a disk 24 is irradiated with a condensed laser beam via an optical
system in an optical head 23, so that a recording mark is formed.
It is understood that although the apparatus is disclosed
schematically, it includes elements such as an automatic focusing
(AF) means and tracking means as part of the transducing system
generally referred to as the optical head 23.
[0039] At the time of playback on the other hand, the intensity
change of the laser beam reflected from a target address on the
disk 24 is received by a light detector 25 in which the laser beam
is converted into an electrical signal. Then the electrical signal
is input via a reproduced signal amplifier 26 to a waveform
equalizer 27. Then, the binary signal is formed by a discriminator
28 and decoded by a decoder 29 into a data bit string
(information). Next, a preformatted area (header) of a target
address is detected and analyzed by header reader 33. Then, the
dummy signal and header are deleted by dummy signal and header
deleter 34, and a reproduced user data signal 35 is obtained.
[0040] Next, it is determined if the reproduced signal represents
control data by a control-data detector 36. If the reproduced
signal contains control data including information on the dummy
data pattern, the dummy data information is picked up from the
control data by dummy data information separator 39. Then, the
dummy signal is generated according to the information (dummy data)
on the dummy data pattern by dummy data pattern generator 40. If
the reproduced signal is not control data, the data is stored in
memory 38 through reproduced user data controller 37.
[0041] As a modification of the embodiment disclosed with respect
to FIG. 3, a bit array (data area postamble) can be added by
postamble adding circuit 43 before the dummy data recorded in the
dummy area 16, and the inversion of the ratio of the recording mark
and the space for the dummy signal can be avoided. The postamble
pattern is generated in accordance with the user data to be
recorded and is added to the user data by adder 43 at the position
just after the user data in the direction of recording.
[0042] FIG. 4 shows a flow chart of the steps followed when a disk
is inserted in the record playback apparatus of the present
invention. First, in step 45, it is detected that the disk is set
in the drive by an optical or mechanical sensor. Then, the optical
head is moved to, for example, the innermost area of the disk in
step 46 and reading information starts in step 47. In step 48, the
reproduced signal is read out and amplified from the rotating disk,
and then the wave form generated thereby is equalized, digitized
and decoded in steps 49-51, respectively. The control data is
extracted by deleting the synchronizing signal, etc. in step 52 and
in step 53 the information of the dummy data pattern is taken from
the control data. Such information (dummy data) includes, for
example, the specification of the duty ratio of the dummy signal to
be recorded being added to the user data. In step 54, the dummy
data pattern is generated and stored in step 55 in a memory so that
the dummy signal can be added when user data is to be recorded.
[0043] An example of the data area postamble is shown in FIG. 5 as
31 and the dummy data as 32. Patterns (a) and (b) show the case
where the end of the user data is a binary "0", and patterns (c)
and (d) show the case where the end of the user data is a binary
"1". Accordingly, patterns (a) and (c) show the case where the end
of the user data is a mark. Patterns (b) and (d) show the case
where the end of the user data is a space. It is preferable if the
postamble is provided according to the known signal modulation
standard.
[0044] An example of recording the information on the dummy data
pattern in the control data area is shown in FIG. 6(a). The dummy
signal area is divided into two sub areas, and the dummy signal
pattern information area in the control data area is also divided
into two sub areas; each sub area being divided into three
sections. A mark length, expressed in units of Tw, is recorded
using 4 bits in the first section. A space length, which is
expressed in units of Tw, is recorded using 4 bits in the second
section. The number of repetitions of these marks and spaces is
recorded using the following 8 bits (1 byte). Then, a mark length,
a space length, and the number of repetitions in the second sub
area is recorded using 16 bits. Thus, the whole pattern of the
dummy data expressed by marks and spaces is represented by 4 bytes
of control data.
[0045] In other examples, a single repetition pattern of a mark and
a space can be written in the dummy data pattern information area,
or 3 patterns can be written dividing the dummy data area into 3
sub areas. When the dummy data area is divided into more than 4
areas, the required space to represent the patterns in the control
data area exceeds 4 bytes.
[0046] As another example, the basic mark and space arrangement,
which is repeated in the first sub area of two sub areas in the
dummy data area, is recorded in the control data area using 2 bytes
in the same manner as in the dummy data area, and the basic mark
and space arrangement in the second sub area is recorded using the
following 2 bytes as shown in FIG. 6(b). In this method, 4 bytes
are used in the control data area to represent the pattern in the
dummy data when the number of sub areas is two, and more than 4
bytes are used when the number of sub areas are more than 3 just
like the former example.
[0047] Although a description has been given of the continuous
servo system by way of example, the same effect is achievable with
a sampled servo system in a like manner as set forth herein.
Further, although a laser beam has been disclosed for recording, it
is possible to use an electron beam or an ion beam instead of the
laser beam in accordance with the present invention.
* * * * *