U.S. patent application number 11/562089 was filed with the patent office on 2007-04-05 for optical disk, optical disk recording method and optical disk apparatus.
Invention is credited to Hideo Ando, Yutaka Kashihara, Chosaku Noda, Yutaka Okamoto.
Application Number | 20070076569 11/562089 |
Document ID | / |
Family ID | 18656983 |
Filed Date | 2007-04-05 |
United States Patent
Application |
20070076569 |
Kind Code |
A1 |
Okamoto; Yutaka ; et
al. |
April 5, 2007 |
OPTICAL DISK, OPTICAL DISK RECORDING METHOD AND OPTICAL DISK
APPARATUS
Abstract
A signal can be detected based on a level slice system and
detection delay time can be reduced by setting the recording
density of a header field in a linear direction lower (coarse) than
that of a user data recording field. Further, a signal can be
detected based on the level slice system and detection delay time
can be reduced by using a mark position form having a large
detection margin as an information recording system of the header
field. A readout error of a sector number due to a detection error
is compensated for by recording address marks AM for attaining byte
synchronization of the header field in both of a head portion and
tail portion of information recorded in the header field.
Inventors: |
Okamoto; Yutaka; (Chofu-Shi,
JP) ; Ando; Hideo; (Hino-Shi, JP) ; Noda;
Chosaku; (Kawasaki-Shi, JP) ; Kashihara; Yutaka;
(Fuchu-Shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Family ID: |
18656983 |
Appl. No.: |
11/562089 |
Filed: |
November 21, 2006 |
Related U.S. Patent Documents
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Application
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Filing Date |
Patent Number |
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11328132 |
Jan 10, 2006 |
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11562089 |
Nov 21, 2006 |
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11059386 |
Feb 17, 2005 |
7012873 |
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11328132 |
Jan 10, 2006 |
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10748142 |
Dec 31, 2003 |
6870804 |
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11059386 |
Feb 17, 2005 |
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10441119 |
May 20, 2003 |
6711111 |
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10748142 |
Dec 31, 2003 |
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09861715 |
May 22, 2001 |
6587417 |
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10441119 |
May 20, 2003 |
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Current U.S.
Class: |
369/275.3 ;
G9B/7.026; G9B/7.034; G9B/7.037 |
Current CPC
Class: |
G11B 7/0079 20130101;
G11B 20/1426 20130101; G11B 2020/1245 20130101; G11B 2020/1278
20130101; G11B 7/00745 20130101; G11B 27/19 20130101; G11B 7/24082
20130101; G11B 20/10055 20130101; G11B 20/10111 20130101; G11B
2020/1298 20130101; G11B 7/006 20130101; G11B 7/24085 20130101;
G11B 27/3027 20130101; G11B 2020/1267 20130101; G11B 20/18
20130101; G11B 2220/2562 20130101; G11B 20/1403 20130101; G11B
20/1217 20130101; G11B 27/24 20130101; G11B 2020/1277 20130101;
G11B 20/10 20130101; G11B 20/10101 20130101; G11B 7/007 20130101;
G11B 20/10009 20130101; G11B 20/10296 20130101; G11B 7/00718
20130101; G11B 2220/2575 20130101; G11B 20/14 20130101; G11B
2220/216 20130101; G11B 2020/1287 20130101; G11B 2020/1239
20130101; G11B 20/10083 20130101; G11B 2220/2537 20130101; G11B
2020/1292 20130101; G11B 2020/1295 20130101; G11B 20/10037
20130101; G11B 2020/1274 20130101; G11B 2020/1294 20130101; G11B
2020/1465 20130101; G11B 7/013 20130101; G11B 7/005 20130101 |
Class at
Publication: |
369/275.3 |
International
Class: |
G11B 7/24 20060101
G11B007/24 |
Foreign Application Data
Date |
Code |
Application Number |
May 23, 2000 |
JP |
2000-151421 |
Claims
1. (canceled)
2. An optical disc, comprising: a first area including first
recording data formed as pre-pit data; and a second recording area
including second recording data, a minimum pit of the second
recording data being based on a 2 T system, the second recording
data being recorded in such a manner as to be decodable in partial
response maximum likelihood (PRML) decoding system, and the second
recording data being recorded according to a NRZJ manner.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No.
2000-151421, filed May 23, 2000, the entire contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] This invention relates to an optical disk on which data is
recorded, a recording method for recording data on the optical
disk, and an apparatus for recording and reproducing data on the
optical disk.
[0003] Recently, DVD systems have been developed to meet the
requirements for recording MPEG2 images on one surface of an
optical disk having a diameter of 12 cm for two hours or more.
Present DVD standards state that the memory capacity of the disk is
4.7 GB for one surface, the track density is 0.74 .mu.m/track, and
the linear density is 0.267 .mu.m/bit. A DVD based on the above
standards is referred to as a present DVD in this
specification.
[0004] Reproduction of information recorded on an optical disk such
as a DVD is performed by use of an optical head. In the optical
head, a light beam emitted from an LD (laser diode) is focused on a
pit series formed on the track of the optical disk via an object
lens, a light beam reflected from the optical disk is concentrated
on a photo-detector by use of a condensing lens and thus a
reproduction signal can be attained. The reproduction signal from
the photo-detector is input to a reproduction signal processing
system and subjected to waveform equalization by an equalizer, and
then data is decoded by use of a detector. According to DVD
standards, the wavelength of the LD in the optical head is 0.65
.mu.m and the numerical aperture of the object lens is 0.6.
[0005] As a higher definition system is required as an image
source, it is required to further increase the memory capacity of
the DVD in order to record and supply such image data. In order to
satisfy the above requirement, the wavelength of the LD is reduced
to attain a higher recording density expressed in terms of the
wavelength, thus requiring further study on increasing the memory
capacity using the PRML (Partial Response Maximum Likelihood)
signal process.
[0006] In the conventional signal detection method, whether the
recorded information is "0" or "1" is determined for each bit.
Since the interval between pits or marks becomes shorter as the
information recording density is increased, the influence of
waveform interference by the adjacent information bit on the
reproduction signal also increases.
[0007] In order to eliminate the influence of waveform
interference, it is necessary to perform a signal process to
emphasize the high frequency component of the response
characteristic of the recording/reproduction channel and suppress
the skirt portion of the response waveform extending to the
adjacent bit to a low level.
[0008] However, since the noise component is also emphasized if the
high frequency component of the response characteristic is
emphasized, the number of errors caused by the emphasizing process
consequentially increases. Therefore, it is difficult to
significantly improve the recording density using the conventional
signal processing system.
[0009] On the other hand, in the PRML signal processing system, a
waveform interference amount between adjacent bits of the
reproduction signal waveform is permitted in a range specified by
the PR (Partial response) class. Since the reproduced waveform is
influenced by the waveform interference from the adjacent bit and
distorted, it becomes impossible to determine data by use of only
one bit as in the conventional system.
[0010] However, since the waveform interference amount is limited
to a specified value, signal power dispersed before and after an
information bit can be efficiently utilized if a Maximum Likelihood
detector using an ML (Maximum Likelihood) determination circuit for
selecting data of the most likelihood among the sequence by taking
portions before and after the waveform into consideration is used,
and therefore, data can be detected at a relatively low error rate.
A PR equalizer is used as an equalizing circuit for correcting a
deviation of the reproduction waveform from the PR class.
[0011] In conventional level slice equalizers, the reproduced
waveform is subjected to a waveform equalization process to set the
intersecting point between the equalized waveform and a certain
threshold level at the center of the window. More specifically, the
high frequency component of the reproduced signal is amplified. In
the detector, an intersecting point between the equalized waveform
and the certain threshold level is detected and if the intersecting
point is detected in the window, binary data "1" is output, and if
it is not detected, binary data "0" is output. Then, by subjecting
the binary data obtained after detection of the intersecting point
to an NRZI (Non Return Zero Inverted) conversion process, the
decoded data can be attained.
[0012] The intersecting point between the equalized waveform and
the threshold level does not always exist at the center of the
window due to the presence of noise. The standard deviation of
intersecting point data standardized according to the window width
is called "jitter" and is used as an evaluation standard for
optical disks and drive units.
[0013] Now, a case wherein an optical disk whose recording density
is made higher than present DVDs is reproduced by use of the same
optical head as that of the present DVD is considered. If the track
density is increased, a reproduction signal may contain a large
amount of signal-degrading component called "crosstalk". On the
other hand, if the linear density is increased, the reproduced
waveform becomes dull. As described before, in the equalizer, since
the high frequency component of the reproducing signal is
amplified, it is necessary to more strongly amplify the high
frequency component when an input reproduced waveform becomes
duller. As a result, the equalizer also amplifies the
signal-degrading component. Thus, if the waveform slice system is
used for the signal detection system, the signal-degrading
component is increased irrespective of the method for increasing
recording density, therefore data cannot be correctly decoded.
[0014] As the reproduction signal processing system used when the
SNR (signal/noise ratio) of the reproduction signal is lowered,
utilization of a PRML (Partial Response and Maximum Likelihood)
system instead of the waveform slice system is studied. In the PRML
system, the reproduced waveform is equalized into a waveform having
a known correlation between identification points called a PR
characteristic by use of the equalizer.
[0015] Further, the PRML signal processing system can attain a
satisfactory (low) error rate in the case of high recording
density. This system is a system for detecting data by use of the
correlation between information bits while permitting waveform
interference. Therefore, a delay occurs because a sample data
series is stored into a bus memory as shown in FIG. 9 which will be
described later.
[0016] In the process for detecting user data, generally, the above
delay does not cause any problems. However, in the header field,
since a readout sector number is fed back to the later operation,
the influence becomes larger.
[0017] That is, in a data writing process, a sector number is read
out from the header field, and if the number is determined as a
to-be-accessed sector, the readout operation must be immediately
interrupted, which affects the write operation. Further, if the
number is not the object sector, the write operation is disabled
since data will be destroyed. Therefore, if detection of the number
necessary for the above determination is delayed, it becomes
necessary to take a large GAP field of FIG. 10 which will be
described later in order to take a sufficiently long time
corresponding to the delay time and thus the format efficiency is
degraded accordingly.
[0018] In the conventional header field, only one address mark AM
for attaining byte synchronization is provided after VFO. The
construction is satisfactory when a clock phase pull-in process is
completely terminated in the VFO field, but if the phase pull-in
process is not completely performed due to a disturbance, for
example, data after this cannot be correctly read out.
[0019] Therefore, it is required to provide a device capable of
suppressing the time delay caused when an address of the header
field is read out, reducing the interval of a gap field required
between the header field and the recording field and improving the
format efficiency.
[0020] Further, it is required to provide a device capable of
error-free readout of an address of the header field.
[0021] This invention can solve the above problems, suppress the
time delay caused when an address of the header field is read out,
reduce the interval of a gap field required between the header
field and the recording field and improve the format
efficiency.
[0022] Further, this invention can read out an address of the
header field without error.
BRIEF SUMMARY OF THE INVENTION
[0023] An optical disk of this invention comprises header fields
which are provided on tracks of a concentric form or spiral form
and in which addresses each indicating a position on the track are
previously recorded; and recording fields which respectively follow
the header fields and in which preset data is recorded; wherein the
recording density of the header field is lower than that of the
recording field.
[0024] An optical disk recording method of this invention is a
method for recording data on an optical disk having header fields
which are provided on tracks of a concentric form or spiral form
and in which addresses each indicating a position on the track are
previously recorded, and recording fields which respectively follow
the header fields and in which preset data is recorded; wherein
data is recorded in the recording field with a recording density
higher than the recording density of the header field.
[0025] An optical disk apparatus of this invention for recording
data on an optical disk having header fields which are provided on
tracks of a concentric form or spiral form and in which addresses
each indicating a position on the track are previously recorded,
and recording fields which respectively follow the header fields
and in which preset data is recorded and reproducing data recorded
on the optical disk, comprises first reproduction means for
reproducing data in the header field; second reproduction means for
reproducing data in the recording field; determining means for
determining whether a signal now reproduced is a signal from the
header field or a signal from the recording field; and processing
means for reproducing data by use of the first reproduction means
when the determining means determines that the signal now
reproduced is a signal from the header field and reproducing data
by use of the second reproduction means when the determining means
determines that the signal now reproduced is a signal from the
recording field.
[0026] An optical disk apparatus of this invention for recording
data on an optical disk having header fields which are provided on
tracks of a concentric form or spiral form and in which addresses
each indicating a position on the track and at least one pattern
for detecting the address are previously recorded, and recording
fields which respectively follow the header fields and in which
preset data is recorded and reproducing data recorded on the
optical disk, comprises first reproduction means for reproducing
data in the header field; second reproduction means for reproducing
data in the recording field; recording means for recording data in
the recording field; first detecting means for detecting the
pattern used for detecting the address recorded in the header field
based on a reproduction signal from the first reproduction means;
second detecting means for detecting the address recorded in the
header field based on a detection process of the first detecting
means; and processing means for reproducing data in a corresponding
portion of the recording field by use,of the second reproduction
means or recording data in a corresponding portion of the recording
field by use of the recording means when the address detected by
the second detecting means comes to an access position.
[0027] Additional objects and advantages of the invention will be
set forth in the description which follows, and in part will be
obvious from the description, or may be learned by practice of the
invention. The objects and advantages of the invention may be
realized and obtained by means of the instrumentalities and
combinations particularly pointed out hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0028] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate presently
preferred embodiments of the invention, and together with the
general description given above and the detailed description of the
preferred embodiments given below, serve to explain the principles
of the invention.
[0029] FIG. 1 is a view showing the schematic construction of an
optical disk;
[0030] FIG. 2 is a view for illustrating the state of pre-format
data of a header field of the optical disk and grooves and lands of
the surrounding portion;
[0031] FIG. 3 is a diagram for explaining the state of pre-format
data of a header field of the optical disk and grooves and lands of
the surrounding portion;
[0032] FIG. 4 is a view for illustrating the state of pre-format
data of a header field of the optical disk and grooves and lands of
the surrounding portion;
[0033] FIG. 5 is a diagram for explaining the state of pre-format
data of a header field of the optical disk and grooves and lands of
the surrounding portion;
[0034] FIG. 6 is a diagram for explaining the state of pre-format
data of a header field of the optical disk and grooves and lands of
the surrounding portion;
[0035] FIG. 7 is a view for illustrating zones of the optical
disk;
[0036] FIG. 8 is a diagram for explaining ECC block data;
[0037] FIG. 9 is a diagram for explaining the frame construction of
each sector;
[0038] FIG. 10 is a diagram showing a sector format of each
sector;
[0039] FIG. 11 is a diagram showing a format of another embodiment
of the header field;
[0040] FIG. 12 is a diagram showing the schematic construction of
an optical disk apparatus;
[0041] FIG. 13 is a circuit diagram showing the schematic
construction of a signal detecting section and signal determining
circuit;
[0042] FIG. 14 is a block diagram showing a schematic construction
of a level slice signal processing circuit and PRML signal
processing circuit;
[0043] FIGS. 15A to 15F are diagrams showing signal waveforms and
data values at main portions of the level slice signal processing
circuit;
[0044] FIGS. 16A to 16G are diagrams showing signal waveforms and
data values at main portions of the PRML signal processing
circuit;
[0045] FIGS. 17A to 17C are diagrams for illustrating the decoding
process using an ML decoder;
[0046] FIGS. 18A to 18D are diagrams showing signal waveforms in
the signal determining circuit;
[0047] FIG. 19 is a diagram showing the schematic construction of
an equalizer and ML decoder;
[0048] FIG. 20 is a diagram for illustrating a change in the state
of ACS;
[0049] FIGS. 21A, 21B are diagrams for illustrating a 1,7
modulation process;
[0050] FIGS. 22A to 22F are diagrams showing a difference in the
data detection window width according to modulation codes;
[0051] FIG. 23 is a flowchart for illustrating the data recording
process and data reproducing process;
[0052] FIG. 24 is a diagram showing the schematic construction of
an optical disk apparatus according to another embodiment;
[0053] FIG. 25 is a flowchart for illustrating the data recording
process and data reproduction process;
[0054] FIG. 26 is a diagram showing the schematic construction of
an optical disk apparatus according to another embodiment;
[0055] FIG. 27 is a block diagram showing the schematic
construction of a level slice signal processing circuit and PRML
signal processing circuit;
[0056] FIG. 28 is a flowchart for illustrating the data recording
process and data reproducing process;
[0057] FIG. 29 is a diagram showing the layout of a header field in
another embodiment;
[0058] FIG. 30 is a diagram showing the circuit construction of an
ID detecting section;
[0059] FIG. 31 is a diagram showing the schematic construction of
an optical disk apparatus according to another embodiment;
[0060] FIG. 32 is a flowchart for illustrating the ID detecting
process in the ID detecting section;
[0061] FIG. 33 is a flowchart for illustrating the ID detecting
process in the ID detecting section;
[0062] FIG. 34 is a diagram for illustrating an example of a
process for distributing and recording ID information into a
plurality of sectors; and
[0063] FIG. 35 is a diagram for illustrating an example of a
process for distributing and recording ID information into a
plurality of sectors.
DETAILED DESCRIPTION OF THE INVENTION
[0064] There will now be described embodiments of this invention
with reference to the accompanying drawings.
[0065] FIGS. 1, 2, 3 show the schematic constructions (one example
of the form of a track) of an optical disk 1 of this invention.
[0066] The optical disk 1 has grooves 2 which are previously
wobbled for tracking and in which data is recorded and header
portions (header fields) 3 having pre-pit (emboss pit) strings each
indicating a track address or the like. Lands 4 are provided in
positions adjacent to the grooves 2.
[0067] Data is recorded in the groove 2 by use of recording marks 5
based on a phase change. For example, data is recorded by use of
the recording marks 5 based on the 1,7 RLL (Run Length Limited)
modulation process. For example, user data is recorded in the
groove 2 based on a mark edge form.
[0068] Data is recorded in the header field 3 by use of pre-pits 6
previously formed, for example, formed at the time of formation of
the grooves. For example, data is recorded by use of the pre-pits 6
based on the 8-16 RLL modulation process. Further, for example,
address data is recorded in the header field 3 based on a mark
position form.
[0069] As shown in FIG. 1, the grooves 2 of the optical disk 1 are
previously wobbled in a preset cycle for tracking. For example,
grooves for tacking are wobbled in a preset cycle in order to
obtain a signal used as a reference at the data recording time.
[0070] The header field 3 is formed at the time of formation of the
grooves. As shown in FIGS. 2, 3, the header field 3 includes a
plurality of header fields 3a, 3b, 3c, 3d each formed of a
plurality of pits and is pre-formatted with respect to the grooves
2 as shown in FIGS. 2, 3 and the center of each pit lies on the
same line which passes through the center of the amplitude of
corresponding grooves 2.
[0071] The optical disk 1 is explained by taking a case wherein
data is recorded in the grooves as an example, but the optical disk
is not limited to this case and the optical disk in which data can
be recorded in both of the lands and grooves may be used
(DVD-RAM).
[0072] In this case, as shown in FIGS. 4, 5, 6, the optical disk
has grooves 7 previously wobbled for tracking and header fields 8
having pre-pit (emboss pit) strings each indicating a track address
or the like.
[0073] That is, the grooves 7 for tacking are wobbled in a preset
cycle in order to obtain a signal used as a reference at the data
recording time.
[0074] The header field 8 is formed at the time of formation of the
grooves. As shown in FIGS. 5, 6, the header field 8 includes a
plurality of header fields 8a, 8b, 8c, 8d each formed of a
plurality of pits and is pre-formatted with respect to the grooves
7 as shown in FIGS. 5, 6 and the center of each pit lies on the
boundary line between the groove 7 and the land 9. FIG. 5 shows the
header field 8 attached to the head sector of each track and FIG. 6
shows the header field 8 attached to one of sectors other than the
head sector provided in each track.
[0075] In this case, the header fields 8 for the grooves and the
header fields 8 for the lands are arranged alternately (in a
staggered form).
[0076] The grooves and lands can be formed in a concentric form
instead of the spiral form.
[0077] In this embodiment, it is assumed that data is recorded
based on a zone CLV (ZCLV) system. The ZCLV system is a system for
dividing the plurality of tracks into several zones and keeping
constant the rotating speed of the disk in the same zone. The
recording frequency is kept constant for the entire circumference.
Therefore, the recording capacity of each track in the same zone is
the same. In FIG. 7, the clock signals for the respective zones are
the same and the rotating speeds of the optical disk 1 for the
respective zones and the numbers of sectors for each track are
different.
[0078] In this embodiment, the term "sector" is used to indicate a
minimum unit which can be used for recording, reproducing and
rewriting. In the DVD format, 16 sectors constitute one ECC block.
In the construction of the ECC block of the DVD, parity is
distributed and recorded in the sectors.
[0079] Therefore, data can be rewritten in the sector unit as a
binary data string. However, since a defect occurs in the parity if
data of only one sector is rewritten, data can be rewritten only in
the ECC block unit as significant data. In this respect, it can be
said that the rewritable unit is an ECC block, but in this
embodiment, the "sector" used as a unit to which access of binary
data string can be made is called a "minimum recordable unit".
[0080] That is, as shown in FIG. 7, the optical disk 1 is
constructed of 35 zones, for example, and the rotating speeds (the
reference speed for each zone) of the optical disk 1 for the
respective zones and the numbers of sectors for each track are
different.
[0081] Each zone includes a plurality of (1568) tracks in the
radial direction.
[0082] In each zone, the rotation speed of the optical disk 1
becomes lower and the number of sectors for each track becomes
larger in a portion on the inner side of the optical disk than in a
portion on the outer side.
[0083] As shown in FIG. 8, data is recorded in the tracks of each
zone for each ECC (error correction code) block data unit (for
example, 38688 bytes) used as a data recording unit.
[0084] The ECC block includes 16 sectors in which 2-kilobyte data
is recorded, each of sector ID (identification data) items 1 to 16
of 4-byte (32-bit) configuration used as address data is attached
to the main data (sector data) together with an error detection
code (IED: ID Error Detection Code) of 2-byte configuration for
each sector, and lateral ECCs (Error Correction Codes) 1 and
longitudinal ECCs 2 used as error correction codes for reproduction
data recorded in the ECC block. The ECCs 1, 2 are error correction
codes attached to data as redundancy words for ensuring
reproduction of data in the case that defects exist in the optical
disk 1.
[0085] Each sector is constructed by data of 172 bytes.times.12
rows, and the lateral ECC 1 of 10-byte configuration is attached
for each row (line) and the longitudinal ECC 2 of one row with
182-byte configuration is attached. Thus, an error correcting
section 27 which will be described later performs an error
correction process for each line by use of the lateral ECC 1 and
performs an error correction process for each column by use of the
longitudinal ECC 2.
[0086] When the ECC block is recorded on the optical disk 1, a sync
code (2 bytes: 32 channel bits) for taking byte synchronization at
the data reproducing time is attached for every preset data amount
(for every preset data length interval, for example, 91 bytes: 1456
channel bits) of each sector.
[0087] As shown in FIG. 9, each sector is constructed by 26 frames
(frame=91 bytes: 1456 channel bits) from frame zero to a 25th
frame. The sync code (frame sync signal) attached to each frame is
constructed by a specification code (one byte: 16 channel bits) for
specifying a frame number and a common code (one byte: 16 channel
bits) commonly used for each frame.
[0088] FIG. 9 shows the construction of a physical sector in the
DVD. It is constructed by 26 SYNC frames starting from a 32-channel
bit SYNC code (sync code) and the channel bits are set to 38688
channel bits in total.
[0089] The format of each sector is shown in FIG. 10.
[0090] In FIG. 10, one sector is constructed by 2697 bytes and
includes a 128-byte header field (corresponding to the header
section) 3, 8, 2-byte mirror field 10 and 2567-byte recording field
11.
[0091] The channel bit recorded in the header field 3, 8 of the
sector takes a form subjected to 8-16 RLL modulation. The channel
bit recorded in the recording field 11 of the sector takes a form
subjected to 1,7 RLL modulation. In the header field 3, 8, address
data is recorded according to the mark position form. In the
recording field 11, user data is recorded according to the mark
edge form.
[0092] The header field 3, 8 is an area in which preset data is
recorded when the optical disk 1 is formed. The header field 3, 8
is constructed by four header fields of header 1 field 3a, 8a,
header 2 field 3b, 8b, header 3 field 3c, 8c and header 4 field 3d,
8d.
[0093] Each of the header 1 field 3a, 8a to header 4 field 3d, 8d
is constructed by 46 bytes or 18 bytes and includes a 36-byte or
8-byte sync code portion VFO (Variable Frequency Oscillator),
3-byte address mark AM (Address Mark), 4-byte address portion PID
(Position Identifier), 2-byte error detection code IED (ID Error
Detection Code) and one-byte post amble PA (Post Ambles).
[0094] The header 1 field 3a, 8a and header 3 field 3c, 8c include
a 36-byte sync code portion VFO 1 and the header 2 field 3b, 8b and
header 4 field 3d, 8d include an 8-byte sync code portion VFO
2.
[0095] The sync code portion VFOs 1, 2 are fields for performing
the pull-in process of the PLL, and the sync code portion VFO 1 is
obtained by repeatedly recording "00010001" in channel bits by 36
bytes (576 bits in channel bits) (repeatedly recording a pattern
with a preset interval) and the sync code portion VFO 2 is obtained
by repeatedly recording "100010001" in channel bits by 8 bytes (128
bits in channel bits). The sync code portion VFO 1 is a successive
pattern of so-called 4 T.
[0096] The address mark AM is a 3-byte sync code indicating a
position in which a sector address starts and is constructed by a
48-bit channel code. As the pattern of the respective bytes of the
address mark AM, a special pattern of
"000100010000000000000100010001000000000000010001" which does not
appear in the data portion is used.
[0097] The address portion PIDs 1 to 4 are fields in which sector
numbers are recorded as 4-byte addresses. The sector number is a
physical sector number indicating a physical position on the track
of the optical disk 1, and since the physical sector number is
recorded in the mastering process, it cannot be rewritten.
[0098] The address portion PID (1 to 4) includes one-byte (8-bit)
sector information and 3-byte sector number (physical sector number
as a physical address indicating a physical position on the track).
The sector information includes a 2-bit reserve field, 2-bit
physical ID number field, 3-bit sector type field and one-bit layer
number field.
[0099] The physical ID number is "1" in the case of PID 1, for
example, and is a number indicating the order in which data is
overwritten by four times in the header field 3, 8.
[0100] In the sector type field, codes indicating the first sector
and last sector of the track are recorded.
[0101] The error detection code IED is used for the sector address
(containing the ID number) and for detecting whether or not an
error is present in the readout PID.
[0102] The post amble PA contains state information necessary for
demodulation and also has a function of polarity adjustment for
terminating the header field 51 in space.
[0103] The mirror field 10 is used for offset correction of a
tracking error signal and timing generation of a land/groove
changeover signal, for example.
[0104] The recording field 11 includes a 10-byte or 11-byte gap
field, 20-byte to 27-byte guard 1 field, 35-byte VFO 3 field,
3-byte pre-synchronous code (PS) field, 2418-byte data field,
one-byte post amble 3 (PA3) field, 48-byte to 55-byte guard 2 field
and 24-byte or 25-byte buffer field.
[0105] The gap field is a field in which nothing is written.
[0106] The guard 1 field is a field for preventing terminal
deterioration caused at the repetitive recording time inherent in a
phase change recording medium from giving an influence on the VFO 3
field.
[0107] The VFO 3 field is used for repeatedly recording "100010001"
in channel bits by 35 bytes (560 bits in channel bits) in the PLL
lock field.
[0108] The PS (pre-synchronous code) field is a synchronization
field for connection to the data field.
[0109] The data field is a field including data ID, data ID error
detection code IED, sync code, ECC (Error Correction Code), EDC
(Error Detection Code) and user data. The data ID is sector data of
4-byte (32-channel bit) configuration of each sector. The data ID
error detection code IED is an error detection code of 2-byte
(16-bit) configuration for data ID.
[0110] The PA (post amble) 3 field is a field containing state
information necessary for demodulation and indicating the end of
the last byte of the preceding data field.
[0111] The guard 2 field is a field which prevents terminal
deterioration from influencing the data field. Terminal
deterioration, inherent in phase change recording media, is caused
by repetitive recording.
[0112] The buffer field is a field provided for absorbing
variations in rotation of the optical disk 1 so as to prevent the
recording field from extending into the next header field 3, 8.
[0113] The reason why the gap field is expressed to be constructed
by 10 or 11 bytes is that random shifting is performed. Random
shifting shifts the data write starting position to reduce
repetitive recording degradation of the phase change recording
medium. The length of random shifting is adjusted by use of the
buffer field lying in the last portion of the recording field and
the total length thereof in one sector is a constant 2697
bytes.
[0114] Next, anther embodiment of the header field 3, 8 is
explained with reference to FIG. 11. Portions which are the same as
those of FIG. 10 are denoted by the same reference numerals and the
explanation thereof is omitted.
[0115] The header field 3, 8 includes four header fields of header
1 field 3a', 8a', header 2 field 3b, 8b, header 3 field 3c', 8c'
and header 4 field 3d, 8d.
[0116] The header 1 field 3a', 8a' is constructed by 46 bytes and
includes a 6-byte sync code portion VFO arranged in the top portion
and a 3-byte address mark AM, 4-byte address portion PID 1, 2-byte
error detection code IED 1 and one-byte post amble PA 1 which are
repeatedly recorded by four times after the VFO.
[0117] The header 3 field 3c', 8c' is constructed by 46 bytes and
includes a 6-byte sync code portion VFO arranged in the top portion
and a 3-byte address mark AM, 4-byte address portion PID 3, 2-byte
error detection code IED 3 and one-byte post amble PA 1 which are
repeatedly recorded by four times after the VFO.
[0118] Therefore, a total of 10 bytes of AM, PID, IED, PA is
repeatedly recorded by four times after the 6-byte sync code
portion VFO. As a result, the pull-in time of the PLL becomes
longer than in a case wherein only the exclusive VFO pattern (36
bytes) is used, but since the possibility of reading ID information
repeatedly recorded can be enhanced if the margin of the header
field is large, it becomes more advantageous than the construction
of FIG. 10.
[0119] Next, an optical disk apparatus 21 for dealing with the
optical disk 1 is explained with reference to FIG. 12.
[0120] The optical disk apparatus 21 records data on the optical
disk 1 and reproduces data recorded on the optical disk 1 while it
rotates the optical disk 1 at different speeds for respective
zones.
[0121] As shown in FIG. 12, the main portion of the optical disk
apparatus 21 includes an optical pickup section (optical head) 22,
level slice signal processing circuit 23, PRML signal processing
circuit 24, signal determining circuit 25, drive control circuit
26, error correcting section 27, host device interface 28,
modulator 29, write compensation circuit 30, write driver 31, servo
controller 32 and spindle motor 33.
[0122] The optical pickup section 22 has an object lens 34. In the
optical head section 22, a semiconductor laser unit (not shown) is
provided to face the object lens 34 and energized by the write
driver 31 used as a laser control unit to generate laser rays of an
appropriate wavelength. When the semiconductor laser unit is
energized, laser light properly applied to the optical head 1 is
directed to the object lens 34 and converged on the optical disk 1
by the object lens 34. Data is written on (creation of a mark
string: data is written on the optical disk 1 according to the
interval between variable length marks and the length of each
variable length mark) or reproduced from the optical disk 1 by use
of the converged laser light.
[0123] Setting contents of the write driver 31 are set by the write
compensation circuit 30 and are different depending on the
reproduction power for obtaining a reproducing signal, recording
power for recording data and erasing power for erasing data. The
laser light has three power levels: the reproduction power,
recording power and erasing power, and the semiconductor laser unit
is energized by the write driver 31 so as to emit laser light of
appropriate power.
[0124] The optical disk 1 is directly carried into the apparatus by
use of a tray (not shown) or carried into the apparatus after being
received into a disk cartridge (not shown) so that the optical disk
1 will be arranged to face the object lens 34. A tray motor (not
shown) for driving the above tray is provided in the apparatus.
Further, the loaded optical disk 1 is rotatably held on the spindle
motor 33 by a damper (not shown) and rotated by the spindle motor
33.
[0125] The optical pickup section 22 has a signal detecting section
35. As shown in FIG. 13, the signal detecting section 35 includes
amplifiers 41a, 41b, 41c, 41d for converting current signals of
detection signals (Ia, Ib, Ic, Id) from a photo-detector 40 used as
a photo-detector for detecting laser light into voltage signals, an
adder 42a for adding together the signals from the amplifiers 41a,
41b, an adder 42b for adding together the signals from the
amplifiers 41c, 41d, and a subtracter 43 for subtracting the signal
output from the adder 42b from the signal output of the adder
42a.
[0126] A signal from the subtracter 43 or an output signal of the
signal detecting section 35 is output to the level slice signal
processing circuit 23 for reproducing data of the header field 3,
8, and to the PRML signal processing circuit 24 for reproducing
data of the recording field 11 and the signal determining circuit
25.
[0127] Further, a servo signal (track error signal, focus error
signal) is generated by a signal processing circuit (not shown)
based on the signals from amplifiers 81a, 81b, 81c, 81d and output
to the servo controller 32.
[0128] As a method for optically detecting a focus deviation
amount, the following methods are given, for example.
[0129] [Astigmatism Method]
[0130] This is a method for detecting variations in laser light
irradiated on to the photo-detector 40 by use of an optical element
(not shown) for causing astigmatism to occur which is disposed on
an optical detection path of laser light reflected from a light
reflecting film or light reflective recording film of the optical
disk 1. The photo-detecting area is divided into four areas along
diagonal lines. A difference between the sums of the detection
signals obtained from the respective diagonal detection areas is
derived by a signal processing circuit (not shown) and used as a
focus error detection signal (focus signal).
[0131] [Knife-Edge Method]
[0132] This is a method using a knife edge disposed for
non-symmetrically shielding part of the laser light reflected from
the optical disk 1. The photo-detecting area is divided into to two
areas and the difference between the detection signals obtained
from the respective detection areas is derived as a focus error
detection signal.
[0133] Generally, either the astigmatism method or the knife-edge
method is used.
[0134] The optical disk 1 has tracks in a spiral form or concentric
form and information is recorded on the track. Information is
reproduced or recorded/erased by tracing a focused light spot along
the track. In order to stably trace the focused light spot along
the track, it is necessary to optically detect a relative
positional deviation between the track and the focused light
spot.
[0135] As the track deviation detecting method, the following
methods are generally used.
[0136] [Differential Phase Detection Method]
[0137] A variation in the intensity distribution of laser light
reflected from a light reflecting film or light reflective
recording film of the optical disk 1 on the photo-detector 40 is
detected. The photo-detecting area is divided into four areas along
diagonal lines. A phase difference between the sums of the
detection signals obtained from the respective diagonal detection
areas is derived by a signal processing circuit (not shown) and
used as a track error detection signal (tracking signal).
[0138] [Push-Pull Method]
[0139] A variation in the intensity distribution of laser light
reflected from the optical disk 1 on the photo-detector is
detected. The photo-detecting area is divided into two areas and a
difference between the detection signals obtained from the
respective detection areas is derived and used as a track error
detection signal.
[0140] [Twin-Spot Method]
[0141] For example, a diffraction element is disposed in a light
transmission system between the semiconductor laser element and the
optical disk 1 to divide light into a plurality of wave surfaces
and detect a variation in the reflected light amount of -primary
diffracted light applied to the optical disk 1. A photo-detecting
area for individually detecting the reflected light amount of
+primary diffracted light and the reflected light amount of
-primary diffracted light is disposed in addition to the
photo-detecting area for detecting the reproducing signal and a
track error detection signal is obtained by deriving a difference
between the detection signals.
[0142] The signal processing system on the reproducing side has two
systems including a system (level slice signal processing circuit
23) for processing a signal from the header field 3, 8 by use of
the level slice system having less detection delay and a system
(PRML signal processing circuit 24) for processing a signal from
the recording field 11 for recording user data by use of the PRML
signal processing system which can attain high-density
recording.
[0143] As shown in FIG. 14, the level slice signal processing
circuit 23 includes an AGC (Automatic Gain Control) amplifier 51,
adder 52, equalizer 53, level slice detector 54, PLL circuit 55,
8-16 RLL demodulator 56, AGC controller 57 and offset controller
58.
[0144] The AGC amplifier 51 corrects the level of a signal from the
signal detector 35 according to a control signal from the AGC
controller 57 and outputs the corrected signal to the adder 52. The
adder 52 adds the signal from the AGC amplifier 51 with an offset
signal from the offset controller 58 and outputs the result of
addition to the equalizer 53.
[0145] The equalizer 53 subjects the waveform (reproduced waveform)
of the reproduction signal from the adder 52 to waveform
equalization so that an intersecting point between the equalized
waveform and a certain threshold level will be set at the center of
the window and then outputs the result of equalization to the level
slice detector 54, AGC controller 57 and offset controller 58.
[0146] The level slice detector 54 detects an intersecting point
between the equalized waveform from the equalizer 53 and the
threshold level according to a channel clock from the PLL circuit
55, and if the intersecting point is detected in the window, binary
data "1" is output to the 8-16 RLL demodulator 56, and if the
intersecting point is not detected in the window, binary data "0"
is output to the 8-16 RLL demodulator 56.
[0147] The PLL circuit 55 generates a channel clock based on a
signal from the level slice detector 54 and outputs the channel
clock to the 8-16 RLL demodulator 56.
[0148] The 8-16 RLL demodulator 56 demodulates binary data from the
level slice detector 54 based on the 8-16 RLL code.
[0149] The AGC controller 57 corrects the signal of the AGC
amplifier 51 based on the equalized waveform from the equalizer
53.
[0150] The offset controller 58 outputs an offset value to the
adder 52 based on the equalized waveform from the equalizer 53.
[0151] The waveform slice system used as the signal processing
system by the level slice signal processing circuit 23 is explained
with reference to the operation waveform diagrams of FIGS. 15A to
15G.
[0152] As shown in FIG. 15C, a pit series is previously recorded on
the optical disk 1 according to the recording waveform of NRZI form
shown in FIG. 15B and corresponding to recording data which is
information to be recorded as shown in FIG. 15A.
[0153] When information thus recorded on the optical disk 1 is
reproduced, a light beam for reproduction from a photo-diode in the
optical pickup section 22 is applied to the optical disk 1 as a
fine beam spot as indicated by a hatched portion in FIG. 15C to
read out the pit series and derive a reproducing signal.
[0154] The waveform (reproduced waveform) of the reproduction
signal is not obtained as a rectangular wave such as a recording
waveform as shown in FIG. 15B because of the characteristic of the
recording/reproducing system and is obtained as a dull waveform as
shown in FIG. 15D.
[0155] Therefore, the reproduced waveform is subjected to waveform
equalization in the equalizer 53 so that an intersection point
between the equalized waveform and a preset threshold level
(indicated by a dashed line) will be set at the center of the
window. More specifically, the high frequency component of the
reproduction signal is amplified.
[0156] As shown in FIG. 15F, the level slice detector 54 detects an
intersection point between the equalized waveform and the threshold
level, and if the intersection point is detected in the window, it
outputs binary data "1", and if the intersection point is not
detected in the window, it outputs binary data "0".
[0157] Thus, the 8-16 RLL demodulator 56 demodulates the binary
data from the level slice detector 54.
[0158] As shown in FIG. 14, the PRML signal processing circuit 24
includes an AGC amplifier 61, adder 62, A/D converter 63, equalizer
(linear equalizer) 64, ML decoder (Viterbi decoder) 65, 1,7 RLL
demodulator 66, PLL circuit 67, AGC controller 68 and offset
controller 69.
[0159] The AGC amplifier 61 corrects the level of a signal from the
signal detector 35 according to a control signal from the AGC
controller 68 and outputs the corrected signal to the adder 62. The
adder 62 adds the signal from the AGC amplifier 61 with an offset
signal from the offset controller 69 and outputs the result of
addition to the A/D converter 63. The A/D converter 63 converts the
signal from the adder 62 into a digital signal of a discrete time
and discrete amplitude series according to a channel clock from the
PLL circuit 67 and outputs the digital signal to the equalizer
64.
[0160] The equalizer 64 is constructed of a linear equalizer which
is formed of an FIR filter (transversal filter), performs an
equalizing process for the waveform (reproduced waveform) of the
reproduction signal from the A/D converter 63 into a waveform of
PR(l,l) characteristic and outputs the equalized waveform to the ML
decoder 65, PLL circuit 67, AGC controller 68 and offset controller
69.
[0161] The ML decoder 65 is constructed by a Viterbi decoder,
decodes the equalized waveform from the equalizer 64, detects the
same as binary data and outputs the binary data to the 1,7 RLL
demodulator 66.
[0162] The 1,7 RLL demodulator 66 demodulates the decoded binary
data from the ML decoder 65 based on the 1,7 RLL code.
[0163] The PLL circuit 67 generates a channel clock based on the
signal from the equalizer 64 and outputs the channel clock to the
A/D converter 63. That is, it recovers the channel clock by
converting a difference between the amplitude of the PR equalized
waveform and an ideal amplitude value into a phase difference.
[0164] The AGC controller 68 corrects the signal in the AGC
amplifier 61 based on the equalized waveform from the equalizer
64.
[0165] The offset controller 69 outputs an offset value to the
adder 62 based on the equalized waveform from the equalizer 64.
[0166] Next, the signal processing system by the PRML signal
processing circuit 24 is explained with reference to the waveform
diagrams shown in FIGS. 16A to 16G.
[0167] A pit series is previously recorded on the optical disk 1 as
shown in FIG. 16C according to the recording waveform of NRZI form
shown in FIG. 16B and corresponding to recording data which is
information to be recorded as shown in FIG. 16A.
[0168] When information thus recorded on the optical disk 1 is
reproduced, a light beam for reproduction from the photo-diode in
the optical pickup section 22 is applied to the optical disk 1 as a
fine beam spot as indicated by a hatched portion in FIG. 16C to
read out the pit series and derive a reproducing signal.
[0169] The waveform (reproduced waveform) of the reproducing signal
is not obtained as a rectangular wave such as a recording waveform
as shown in FIG. 16B because of the characteristic of the
recording/reproducing system and is obtained as a dull waveform as
shown in FIG. 16D.
[0170] Waveforms obtained after subjecting the reproduced waveform
of FIG. 16D to waveform equalization based on the PR(1,1)
characteristic, PR(1,2,1) characteristic and PR(1,2,2,1)
characteristic in the equalizer 64 are respectively shown in FIGS.
16E, 16F, 16G. The PR(1,1) characteristic is a characteristic in
which an impulse response appears at the rate of 1:1 at two
successive identification points (=amplitude values of the
reproduced waveform at two channel clock timings).
[0171] The recording waveform of NRZI form of FIG. 16B
corresponding to the first part "010010" of recording data of FIG.
16A is expressed as follows.
[0172] 011100
[0173] Since the reproduced waveform is regarded as being an
impulse response to "1" of the recording waveform, the waveform of
FIG. 16E expressed as linear superposition of the following
responses and obtained as "012210" becomes a target waveform to be
equalized as the PR(1,1) characteristic (class).
[0174] 0110
[0175] 00110
[0176] 000110
[0177] The PR(1,2,1) characteristic is a characteristic in which an
impulse response appears at the rate of 1:2:1 at three successive
identification points. The PR(1,2,2,1) characteristic is a
characteristic in which an impulse response appears at the rate of
1:2:2:1 at four successive identification points. As in the case of
the PR(1,1) characteristic, to-be-equalized target waveforms
derived by linear superposition of impulse responses corresponding
to the recording waveform become the waveforms as shown in FIGS.
16F, 16G (although not shown in the drawing, this is also applied
to other PR characteristics).
[0178] As shown in FIGS. 16E, 16F, 16G, it is understood that the
characteristic of the waveform after equalization becomes a duller
characteristic in the order of PR(1,1)
characteristic.fwdarw.PR(1,2,1) characteristic.fwdarw.PR(1,2,2,1)
characteristic.
[0179] In the PRML system, an increase in the signal degrading
component in the equalizer 64 can be suppressed by equalizing the
reproduced waveform into a waveform of a PR characteristic which is
closer to the characteristic of the reproduced waveform.
[0180] In the reproduction signal processing system of PRML system,
a Viterbi decoder which is a representative one of maximum
likelihood decoders is generally used as the ML decoder 65 arranged
after the equalizer 64.
[0181] If the reproduced waveform is equalized into a waveform of
the PR(1,2,2,1) characteristic by the equalizer 64, the ML decoder
65 selects a series having the smallest error with respect to the
sample series of the equalized waveform from all of the reproduced
waveform series which satisfy the PR(1,2,2,1) characteristic and
estimates and outputs recording data (binary data, decoded data)
used as a source for generating the selected reproduced waveform
series while tracing the state transition.
[0182] The state is shown in FIGS. 17A to 17C. In the PRML system,
since the decoding process is not effected based on one sample
value but based on a sequence using the correlation (waveform
interference) due to the PR characteristic of a series of a
plurality of sample values as a premise, the PRML system is highly
resistant to the signal degrading component having no correlation
between sample values.
[0183] The signal determining circuit 25 determines whether a
signal now reproduced is a signal from the header field 3, 8 or a
signal from the recording field 11 in which user data is
recorded.
[0184] As shown in FIG. 13, the signal determining circuit 25
includes a band-pass filter (BPF) 71, comparator (Comp) 72 and
re-triggerable multivibrator 73. The re-triggerable multivibrator
73 is supplied with a power supply voltage via a circuit including
resistors R1, R2 and capacitor C.
[0185] The signal determining circuit 25 receives a signal from the
signal detector 35 of the optical pickup section 22 and makes the
determination and outputs the result of determination to the drive
control circuit 26.
[0186] For example, in a case of groove 2 in which data is recorded
in the header field 3, 8 by use of pre-pits and the recording field
11 of user data is wobbled, if a signal [(Ia+Ib)-(Ic+Id)] of the
photo-detector 40 as shown in FIG. 13 is input to the signal
detector 35 shown in FIG. 13, a determination signal corresponding
to the recording field 11 for recording user data can be obtained
as shown by the waveform of FIG. 18D, and therefore, the drive
control circuit 26 determines whether it is the recording field 11
or not based on the determination signal.
[0187] As shown in FIG. 18A, that is, the band-pass filter (BPF) 71
outputs a waveform having an amplitude based on the wobbled groove
2 to the comparator (Comp) 72. When the comparator (Comp) 72 is
supplied with the waveform of amplitude from the band-pass filter
(BPF) 71, it outputs a pulse signal as shown in FIG. 18C to the
re-triggerable multivibrator 73 based on a comparison voltage V1
shown in FIG. 18B. The re-triggerable multivibrator 73 outputs a
determination signal as shown in FIG. 18D to the drive control
circuit 26 based on the pulse signal from the comparator 72.
[0188] Thus, a convex portion of the wobble signal shown in FIG.
18A is detected by the comparator 72 and a detection signal shown
in FIG. 18C is used as a trigger signal of the re-triggerable
multivibrator 73, and an output of the re-triggerable multivibrator
73 is set at "1" as shown in FIG. 18D while the convex portion of
the wobble signal is being detected.
[0189] The error correcting section 27 is constructed by an ECC
decoder, corrects errors in the demodulated data from the 8-16 RLL
demodulator 56 of the level slice signal processing circuit 23 and
outputs the corrected data to the drive control circuit 26 as data
of the header field 3, 8 or corrects an ECC error of demodulated
data from the 1,7 RLL demodulator 66 of the PRML signal processing
circuit 24 and outputs the corrected data to the host device
interface 28 as reproducing data from the recoding field 11.
[0190] The host device interface 28 outputs reproduction data from
the error correcting section 27 to a host device (not shown),
outputs an instruction of recording or reproduction and the access
position from the host device to the drive control circuit 26, or
converts recording data from the host device into data of a data
form having an error correction code added thereto by an ECC
encoder (not shown) and outputs the converted data to the modulator
29.
[0191] The modulator 29 encodes data supplied from the host device
interface 28 into a 1,7 modulation code or data to be recorded on a
channel and outputs the coded data to the write compensating
circuit 30 used as a recording compensator. The write compensating
circuit 30 converts an output waveform from the modulator 29 into
an NRZI form and outputs a write current waveform in which a
deviation between the write waveform and the mark form caused by
conduction of heat of the optical disk 1 is compensated for to the
write driver 31.
[0192] The drive control circuit 26 controls the whole portion of
the optical disk apparatus 21.
[0193] The drive control circuit 26 supplies a selection signal to
the level slice signal processing circuit 23 or PRML signal
processing circuit 24 according to the determination signal from
the signal determination circuit 25 and performs the control
operation so that data now produced can be adequately
processed.
[0194] For example, the drive control circuit 26 outputs a
selection signal to a changeover switch 59 of the level slice
signal processing circuit 23 to turn ON the changeover switch 59 so
that demodulated data from the 8-16 RLL demodulator 56 can be
output to the error correcting section 27 via the changeover switch
59.
[0195] Further, the drive control circuit 26 outputs a selection
signal to a changeover switch 70 of the PRML signal processing
circuit 24 to turn ON the changeover switch 70 so that demodulated
data from the 1,7 RLL demodulator 66 can be output to the error
correcting section 27 via the changeover switch 70.
[0196] In addition, the drive control circuit 26 controls the servo
controller 32 based on address data including data from the error
correcting section 27 and instruction data from the host device so
as to move the light beam from the optical pickup section 22 to the
access position and control the spindle motor 33 to rotate at a
rotation speed of a zone corresponding to the access position.
[0197] Further, the drive control circuit 26 controls the write
driver 31 so as to control a semiconductor laser oscillator (not
shown) based on recording data from the write compensating circuit
30 to emit a light beam.
[0198] The drive control circuit 26 includes an AM detector 26a,
SYNC detector 26b and format controller 26c.
[0199] The AM detector 25a detects an address mark AM of the header
field 3, 8 according to a demodulation signal from the 8-16 RLL
demodulator 56 based on the channel clock from the PLL circuit 55
of the level slice signal processing circuit 23.
[0200] For example, the AM detector includes a register in which
the pattern of the address mark AM is stored, a register for
recording a demodulation signal from the 8-16 RLL demodulator 56
based on the channel clock from the PLL circuit 55 and a comparator
for comparing register data items in the two registers and outputs
a detection signal of the address mark AM to the format controller
26c when a coincidence signal is output from the comparator.
[0201] The SYNC detector 26b detects a SYNC code of the recording
field 11 according to a demodulation signal from the 1,7 RLL
demodulator 66 based on the channel clock from the PLL circuit 67
of the PRML signal processing circuit 24.
[0202] For example, the SYNC detector includes a register in which
the pattern of the SYNC code is stored, a register for recording a
demodulation signal from the 1,7 RLL demodulator 66 based on the
channel clock from the PLL circuit 67 and a comparator for
comparing register data items in the two registers and outputs a
detection signal of the SYNC code to the format controller 26c when
a coincidence signal is output from the comparator.
[0203] The format controller 26c determines a position illuminated
on the track by the laser light from the optical pickup section 22
and controls timings of the control signals output to the
respective sections by using the result of determination as a
reference by counting a read clock, write clock or wobble clock
while attaining synchronization by use of a detection signal of the
address mark AM from the AM detector 26a and a detection signal of
the SYNC code from the SYNC detector 26b.
[0204] The read clock is a clock at the data reproducing (readout)
time, the channel clock from the PLL circuit 55 is supplied to the
format controller 26c when data of the header field 3, 8 is
reproduced and the channel clock from the PLL circuit 67 is
supplied to the format controller 26c when data of the recording
field 11 is reproduced.
[0205] The write clock is a clock generated based on a clock having
a preset cycle from a clock generating section (not shown), that
is, a reference clock from an oscillator and supplied to the format
controller 26c.
[0206] The wobble clock is a clock generated from a clock
generating section (not shown) based on an output signal from the
signal detector 35 of the optical pickup section 22 and supplied to
the format controller 26c.
[0207] That is, the format controller 26c determines a position
illuminated on the track by the laser light from the optical pickup
section 22 and controls timings of the control signals output to
the respective sections by using the result of determination as a
reference by counting the read clock or wobble clock while
attaining synchronization by use of a detection signal of the
address mark AM of the header field 3, 8 and a detection signal of
the SYNC code of the recording field 11 when data of the recording
field 11 is read out.
[0208] Further, the format controller 26c determines a position
illuminated on the track by the laser light from the optical pickup
section 22 and controls timings of the control signals output to
the respective sections by using the result of determination as a
reference by counting the read clock or wobble clock while
attaining synchronization by use of a detection signal of the
address mark AM of the header field 3, 8 when data of the recording
field 11 is written and by counting the write clock or wobble clock
in the recording field 11.
[0209] With the construction shown in FIGS. 13, 14, since data of
the header field 3, 8 is constructed by pre-pits, the write data
modulator 29 is only required to cope with a (1,7) RLL code used in
the PRML system of the recording field 11.
[0210] The signal processing system on the reproducing side is
constructed by two systems including a system for processing the
header field 3, 8 according to the level slice system and a system
for processing the recording field 11 for recording user data
according to the PRML signal processing system, but in the above
embodiment, since an 8-16 modulation code in which the minimum run
length is 3 is used as the modulation code of the header field 3,
8, it becomes necessary to provide the demodulator 56 for the 8-16
RLL modulation code in the succeeding stage of the signal
processing system of the level slice system. Further, since a (1,7)
modulation code in which the minimum run length is 1 is used as the
modulation code of the recording field 11 for recording user data,
it becomes necessary to provide the demodulator 66 for the (1,7)
RLL modulation code in the succeeding stage of the signal
processing system of the PRML system.
[0211] FIG. 19 is a diagram showing the construction of the linear
equalizer (PR equalizer) 64 and ML decoder (Viterbi decoder, ML
detector) 65 which are the main portions of the PRML signal
processing circuit 24.
[0212] The ML decoder 65 selects a series having the smallest error
with respect to the sample series of the equalized waveform and
outputs binary data (decoded data) corresponding to the selected
series.
[0213] That is, as shown in FIGS. 17A to 17C, in a case where the
signal waveform series obtained after PR(1,2,2,1) equalization is
given as follows,
[0214] 01355311356531
[0215] impulse responses for a candidate of recorded data (01010 .
. . ) (the recorded waveform is 01100 . . . ) are given as
follows.
[0216] 012210
[0217] 001221
[0218] Then, the reproduced waveform of an ideal PR characteristic
obtained by linear superposition of the above impulse responses is
obtained as follows.
[0219] 013431
[0220] Further, impulse responses for a candidate of another
recorded data (01110 . . . ) (the recorded waveform is 01110 . . .
) are given as follows.
[0221] 0122100
[0222] 0012210
[0223] 0001221
[0224] Then, the reproduced waveform of the ideal PR characteristic
obtained by linear superposition of the above impulse responses is
obtained as follows.
[0225] 0135531
[0226] After this, the cross-correlations with respect to the
waveform series of the above reproduced waveforms are calculated
and a series having the highest correlation (=the smallest error
between the series) with respect to the reproduced equalized
waveform is selected by a probabilistic method.
[0227] The number of candidates of the waveform can be increased
and counted up as in a tree structure but the number of available
states is limited when taking the PR characteristic into
consideration. In the case of the PR(1,2,2,1) characteristic, the
constraint length (the range which the waveform interference gives
an influence) is "4" and variations of recording data series caused
by the waveform interference occur in 16 combinations of four-digit
values constructed by two types of data values of "0" and ill, and
therefore, the state number having no redundancy is 16 at maximum.
There is a possibility that the state number will be reduced if the
modulation code is limited.
[0228] The ML decoder 65 calculates the probability according to an
input sample value when it is assumed that the state is transited
from a certain state to a next state. When a plurality of
candidates of the waveform series transited to the same state are
provided, a probable one of the candidates is determined based on
the accumulated value of the past transition probability.
[0229] For this purpose, a pass memory 65d for storing candidates
of the waveform series is provided in the ML decoder 65. Generally,
the length thereof is set to a length of several ten channel bits.
A plurality of candidates of the waveform series are transited to
the same state while they pass through the pass memory 65d, then
the candidates are repeatedly selected and the most probable series
is finally selected.
[0230] A branch metric calculating section 65a calculates a
logarithm value of the probability of transition of the state which
is expressed in terms of a difference between actual amplitude and
ideal amplitude obtained if it is assumed that the state is
transited from a certain state to a next candidate state when a
sample value is input. A pass metric memory 65c is a memory for
storing a past branch metric accumulated value obtained until the
state transition for each of the states of the state number is
repeatedly effected and the state is attained.
[0231] An ACS 65b is the abbreviated name of a circuit for
performing the Add (addition), Compare (comparing) and Selection
(selecting) operations. As shown in FIG. 20, it is assumed that the
pass metric values of the states A and B at time 1 are respectively
set at "5" and "8", the branch metric caused for transition from
the state A (at time 1) to the state A at time 2 is "4", the branch
metric caused for transition from the state A (at time 1) to the
state B is "5", the branch metric caused for transition from the
state B (at time 1) to the state A is "2", and the branch metric
caused for transition from the state B (at time 1) to the state B
is "5".
[0232] In the ACS 65b, a value "9" obtained by adding the pass
metric value "5" of the state A at time 1 with the branch metric
"4" caused for transition from the state A (at time 1) to the state
A (at time 2) and a value "10" obtained by adding the pass metric
value "8" of the state B at time 1 with the branch metric "2"
caused for transition from the state B (at time 1) to the state A
(at time 2) are compared with each other and transition from the
state B (at time 1) to the state B (at time 2) corresponding to the
larger value is selected (in practice, since the metric value is
diverged if a larger value is selected, a circuit for making a
calculation in which the metric value corresponding to a higher
probability takes a smaller value by properly dealing with the
equations and selecting a smaller metric value is mounted in many
cases). Likewise, a value "10" obtained by adding the pass metric
value "5" of the state A at time 1 with the branch metric "5"
caused for transition from the state A (at time 1) to the state B
(at time 2) and a value "13" obtained by adding the pass metric
value "8" of the state B at time 1 with the branch metric "5"
caused for transition from the state B (at time 1) to the state B
(at time 2) are compared with each other and transition from the
state B (at time 1) to the state B (at time 2) corresponding to the
larger value is selected. In this case, since it is only the state
B of time 1 that has been transited to each of the states of time
2, the waveform series which is set to the state A at time 1 is
eliminated from the candidate to be selected. The pass memory 65d
is a memory for recording series (=pass) remaining as selected
candidates. Generally, only one candidate of the series is left
behind by the time the candidate passes through the pass memory
65d, but a plurality of series may remain as candidates depending
on the noise condition, and in this case, the series which is
determined as the most probable candidate is selected by comparing
the contents of the pass memory 65d and the pass metric of the pass
metric memory 65c by use of the pass selecting section 65e.
[0233] Since the series is selected and detection data is
determined after the series has passed through the pass memory 65d,
an output of the ML decoder 65 is more delayed than in a case of
the conventional data detector of a waveform slice system.
[0234] In the above embodiment, data of the header field 3, 8 is
detected by the level slice system having less detection delay and
data of the recording field 11 for recording user data is detected
by the PRML system capable of attaining the high recording density.
In the case of the PRML system, a system such as the 1,7 modulation
code in which the code rate can be made high and the channel band
can be suppressed to a low level is used.
[0235] The 1,7 modulation code is a conversion system for
conversion to a code in which the code rate is 2/3, the minimum run
length (=d constraint) indicating the minimum number of "0s" lying
between "1" and "1" of the data series is "1", and the maximum run
length (=k constraint) indicating the maximum number of "0s" lying
between "1" and "1" of the data series is "7".
[0236] As the modulation code adequately applied to the PRML system
and having the code rate of 2/3 (2 to 3, conversion of 2-bit data
to 3 bits), an 8-12 modulation code having the d constraint of 1 is
provided in addition to the 1,7 modulation code.
[0237] On the other hand, in the case of the level slice system, a
system such as a 2,7 modulation code in which the code rate is low,
but the minimum run length can be set large is preferable. The 2,7
modulation code is a conversion system for conversion to a code in
which the code rate is 1/2, the minimum run length (=d constraint)
indicating the minimum number of "0s" lying between "1" and "1" of
the data series is "2", and the maximum run length (=k constraint)
indicating the maximum number of "0s" lying between "1" and "1" of
the data series is "7". As the modulation code adequately applied
to the level slice system and having the minimum run length (=d
constraint) of "2", an 8-16 modulation code having the code rate of
8/16 and an 8-15 modulation code having the code rate of 8/15 are
provided in addition to the 2,7 modulation code.
[0238] The reason why the system in which the minimum run length
can be set to a large value can be adequately used for the level
slice system is that it is important that the linear convolution is
established even when the minimum mark/pit amplitude value is small
in the case of PRML system, but it is impossible to slice the
amplitude if the minimum mark/pit amplitude value is not larger
than a certain value in the case of level slice system.
[0239] The 1,7 modulation code is a modulation code in which the
code rate is 2/3, the d constraint is "1" and the k constraint is
"7". As shown in FIG. 21A, the d constraint of "1" indicates that
the constraint is set so as to provide at lest one "0" between "1"
and "1" of the code after modulation. The k constraint of "7"
indicates that the constraint is set so as to provide seven "0s" at
most between "1" and "1" of the code after modulation. Since the
modulated code is recorded in the NRZI form (FIG. 21B) when it is
recorded on the optical disk 1, the minimum pit/mark length is set
to the length of two channel clocks period and the maximum pit/mark
length is set to the length of eight channel clocks period.
[0240] The 8-16 modulation code used in the DVD is a modulation
code in which the code rate is 1/2, the d constraint is "2" and the
k constraint is "10". Therefore, when the code is recorded on the
recording medium, the minimum pit/mark length is set to the length
of three channel clocks period and the maximum pit/mark length is
set to the length of eleven channel clocks period. Like the 8-16
modulation code, in the 8-15 modulation code, the d constraint is
"2" and the minimum pit/mark length is set to the length of three
channel clocks period.
[0241] If the same user data recording density is set for the 1,7
modulation code and 8-16 modulation code, 2-bit user data is
converted into a 3-bit code in the 1,7 modulation code and 2-bit
user data is converted into a 4-bit code in the 8-16 modulation
code, and therefore, the length of one channel clock in the 8-16
modulation code becomes 3/4 times that of the 1,7 modulation code.
However, since the minimum pit/mark length of the 8-16 modulation
code is set to the length of three channel clocks period and the
minimum pit/mark length of the 1,7 modulation code is set to the
length of two channel clocks period, the result of
(3/4.times.3/2=9/8) is obtained. Thus, it is understood that the
8-16 modulation code has a slightly larger bit length and is more
suitably used for the level slice system. Therefore, in order to
use the level slice system having less detection delay for the
header field 3, 8, it is required to make the recording density in
the linear direction of information recorded in the header field 3,
8 lower than the recording density in the linear direction of
information recorded in the user data recording field 11.
[0242] In the above example, a case wherein the 8-16 modulation
code is used for the header field 3, 8 and the 1,7 modulation code
is used for the user data recording field 11 is explained as a code
selection example based on the reality, but the same modulation
code can be used for the header field 3, 8 and the user data
recording field 11 in certain cases. Also, in this case, since it
is impossible to operate the level slice system at the same
amplitude value as the PRML system with the recording density at
which the PRML system can be used for the user data recording field
11, it becomes necessary to lower the recording density in the
linear direction of the header field 3, 8 and elongate the pit/mark
length to attain a large amplitude value.
[0243] As an example of a method for using the same modulation code
for the header field 3, 8 and user data recording field 11 and
lowering the recording density in the linear direction of the
header field 3, 8 to elongate the pit length or mark length and
attain a large amplitude value, a method for writing data in which
a code of the minimum pit length does not appear into the header
field 3, 8 is provided.
[0244] The advantage of this method is that the channel clock rate
becomes the same in the header field 3, 8 and user data recording
field 11 although the physical pit recording density is lowered.
Therefore, it becomes unnecessary to separate the PLL for clock
recovery for the header field 3, 8 and the PLL for clock recovery
for the user data recording field 11. Further, since the modulation
code is the same, the demodulator can be commonly used.
[0245] In a recording/reproducing optical disk apparatus using a
pre-pit header for the header field 3, 8, there is a large
difference between the level of a signal from the mark of the user
data recording field 11 and the level of a signal from the pit of
the header field 3, 8. Since the PRML signal processing system is a
system for detecting an amplitude value at an identification point
synchronized with the channel clock, it tends to be influenced by a
level variation. Of course, a correction for level difference
between the header field 3, 8 and the user data recording field 11
is made by use of an AGC, but it is difficult to completely
eliminate the influence by the previously used level at the
changeover time if the detection system utilizes the same PRML
signal processing system.
[0246] Since it is necessary to make the GAP field for changeover
large in order to almost completely eliminate the influence, the
format efficiency is lowered. If the conventional level slice
system is applied to the ID section of the recording/reproduction
optical disk apparatus using the pre-pit header, it is expected
that the above problem can be solved.
[0247] As shown in FIGS. 22A to 22C, data is recorded in the header
field 3, 8 by use of a modulation code having the minimum pit
(mark) length of three channel bits and, as shown in FIGS. 22D to
22F, data is recorded in the recording field 11 by use of a
modulation code having the minimum pit (mark) length of two channel
bits.
[0248] That is, FIGS. 22A to 22C show the relation between the
channel bit pattern (FIG. 22A), write current waveform (FIG. 22B)
and to-be-written pit (mark) (FIG. 22C) in the case of the minimum
pit in the (1,7) modulation code.
[0249] FIGS. 22D to 22F show the relation between the channel bit
pattern (FIG. 22D), write current waveform (FIG. 22E) and
to-be-written pit (mark) (FIG. 22F) in the case of the minimum pit
in the 8-16 modulation code.
[0250] In a modulation code such as the 8-16 modulation code shown
in FIGS. 22D to 22F in which the code rate is low, the clock
frequency becomes high and the width of the data detection window
becomes narrow even if the minimum pit/mark length is large.
[0251] As for the conversion ratio in the case of 8-16 modulation,
one-bit user data is converted into a 2-bit channel bit pattern
from the viewpoint of ratio, and in the case of (1,7) modulation in
which the code rate is higher, 2-bit user data is converted into a
3-bit channel bit pattern.
[0252] Therefore, as indicated by the relationship shown in FIGS.
22A to 22C and FIGS. 22D to 22F, even if the minimum pit (mark)
length is larger in the 8-16 modulation and the amplitude can be
made larger than in the (1,7) modulation accordingly, the window
width is shorter in the 8-16 modulation than in the (1,7)
modulation and it becomes more difficult to control the rise and
fall positions of the waveform.
[0253] If the recording density is enhanced, it is advantageous to
use the mark edge form in which information can be recorded on both
edges in a condition that the recording density is restricted by
the minimum pit/mark length, but if an attempt is made to attain a
sufficiently large margin by lowering the recording density, it is
expected that the reliability can be enhanced by using a mark
position form in which information is recorded only in the mark
position and simplifying the construction of the data recording and
reproducing means.
[0254] That is, pre-pits are formed in the header field 3, 8 by the
recording method of the mark position form and recording marks are
written into the user data recording field 11 by the recording
method of the mark edge form.
[0255] As shown in FIG. 2, in the case of the groove recording
system, the groove is interrupted (temporarily terminated) in a
portion of the pre-pit header of the header field 3 in some
cases.
[0256] Further, as shown in FIG. 4, in the case of the groove/land
recording system, the groove is interrupted in a portion of the
pre-pit header of the header field 8 in some cases.
[0257] That is, in the case of a wobble groove system for wobbling
the groove in the radial direction, timing is generated by use of a
clock synchronized with wobbling. Therefore, if a deviation occurs
with respect to the phase of the clock before the wobble groove is
interrupted and after the wobble groove is re-started, the PLL
pull-in process becomes necessary and stability cannot be
maintained.
[0258] Therefore, even when the recording density and minimum
pit/mark length are changed for the header field 3, 8 and the
recording field 11, the length of the to-be-interrupted groove of
the header field 3, 8 is set to the integral multiple of the groove
cycle. Alternatively, the phase of the amplitude at timing when the
wobble groove is re-started after the header field 3, 8 is set to a
value which can be derived based on the phase at the end time of
the wobble groove and the interruption time length by the header
field 3, 8.
[0259] That is, an output of a phase difference detection circuit
(not shown) of the PLL circuits 55, 67 synchronized with the wobble
signal before interruption of the wobble groove is set to have such
a phase that a large phase difference will not be detected when the
wobble signal is input after interruption.
[0260] If the recording density is lowered (coarse) to make the
pit/mark length large, a sufficiently large amplitude value can be
surely obtained, but in the case of level slice system, the
detection window width is important as well as the amplitude
value.
[0261] In a DVD, the pit/mark recording system on the optical disk
1 is a mark edge form in which information is recorded in rise and
fall positions of the waveform. As shown in FIG. 22B, in the
modulation code such as the 8-16 modulation code in which the code
rate is low, the clock frequency becomes high and the data
detecting window width becomes narrow even if the minimum pit/mark
length is large. That is, it is difficult to control the rise and
fall positions of the waveform. If the recording density is
enhanced (dense), it is advantageous to use the mark edge form in
which information can be recorded on both ends in a condition that
the recording density is restricted by the minimum pit/mark length.
However, if an attempt is made to attain a sufficiently large
margin by lowering the recording density, it is expected that the
reliability can be enhanced by using a mark position form in which
information is recorded only in the mark position and simplifying
the construction of the data recording and reproducing means.
[0262] That is, as shown in FIGS. 2, 4, pre-pits are formed in the
header field 3, 8 by the recording method of the mark position form
and recording marks are written into the user data recording field
11 by the recording method of the mark edge form.
[0263] Next, with the above construction, the data recording
process and data reproduction process in the optical disk apparatus
21 are explained with reference to the flowchart shown in FIG.
23.
[0264] Immediately after the seeking operation of the optical
pickup section 22 is completed or, when the format controller 26c
deviates from the tracing path by a disturbance or the like, that
is, when the format controller 26c cannot grasp the position on the
track, the following control process is effected.
[0265] That is, the signal determining circuit 25 checks the signal
level of a signal supplied from the optical pickup section 22 (ST1)
and determines whether or not it is the recording field 11 for
recording user data (ST2).
[0266] As the result of determination, if the signal determining
circuit 25 determines that it is the user data recording field 11,
the circuit 25 outputs a signal indicating the user data recording
field 11 to the drive control circuit 26 (ST3).
[0267] Then, the drive control circuit 26 outputs a selection
signal to the PRML signal processing circuit 24 (ST4).
[0268] In step ST2, if the signal determining circuit 25 does not
determine the user data recording field 11, it outputs a signal
indicating the header field 3, 8 to the drive control circuit 26
(ST5).
[0269] Then, the drive control circuit 26 outputs a selection
signal to the level slice signal processing circuit 23 (ST6).
[0270] While the PRML signal processing circuit 24 or level slice
signal processing circuit 23 is being selected by the selection
signal obtained in step ST4 or ST6, the drive control circuit 26
establishes synchronization of the format controller 26c and
records data or reproduces recorded data based on data from the
signal processing system properly selected for each field
(ST7).
[0271] At the start of correct data reproduction, the format
controller 26c can grasp the position on the track and the
determination result of the signal determining circuit 25 is used
no more.
[0272] In the above embodiment, a case wherein the signal
determining circuit 25 is provided in the succeeding stage of the
optical pickup section 22 is explained, but this is not limitative
and, as shown in FIG. 24, a case wherein a signal determining
circuit 36 is provided in the succeeding stage of the error
correcting section 27 can be realized in the same manner. Portions
which are the same as those of FIG. 12 are denoted by the same
reference numerals and an explanation thereof is omitted.
[0273] In the signal determining circuit 36, whether the signal now
reproduced is a signal from the header field 3, 8 or a signal from
the user data recording field 11 is determined based on whether
data is significant or not. In order to determine whether the
signal now reproduced is a signal from the header field 3, 8 or a
signal from the user data recording field 11, an attempt is made to
read out data on the assumption that one of the fields is
temporarily determined in the initial condition. When a signal is
determined to be output from the temporarily determined field,
significant data such as the sync code portion VFO, address mark AM
can be obtained and the position in the temporarily determined
field is detected at this time point.
[0274] In the case of a rewriting type, since no data is written in
the user data recording field 11 in some cases, it is preferable to
search for significant data on the assumption that the header field
3, 8 is temporarily determined.
[0275] In this case, the signal determining circuit 36 determines
whether data can be read out from the header field 3, 8 based on an
output from the error correcting section 27 which is based on an
output of the level slice signal processing circuit 23 for
processing the signal from the optical pickup section 22 and
determines that the field is the header field 3, 8 when data of the
header field 3, 8 can be read out.
[0276] With the above construction, the data recording process and
data reproduction process in the optical disk apparatus 21 are
explained with reference to the flowchart shown in FIG. 25.
[0277] Immediately after the seeking operation by the optical
pickup section 22 or when the format controller 26c deviates from
the tracing path by a disturbance or the like, that is, when the
format controller 26c cannot grasp the position on the track, the
following control process is effected.
[0278] That is, the signal determining circuit 36 outputs a signal
indicating the header field 3, 8 to the drive control circuit 26
(ST11).
[0279] Then, the drive control circuit 26 outputs a selection
signal to the level slice signal processing circuit 23 (ST12).
[0280] Thus, a signal from the level slice signal processing
circuit 23 is supplied to the signal determining circuit 36 via the
error correcting circuit 27.
[0281] As a result, the signal determining circuit 36 determines
whether significant data such as the sync code portion VFO, address
mark AM can be obtained or not (ST13).
[0282] Then, the signal determining circuit 36 outputs a signal
indicating the header field 3, 8 to the drive control circuit 26
when significant data is obtained (ST14).
[0283] Then, the drive control circuit 26 sets up synchronization
of the format controller 26c and records data or reproduces
recorded data based on data from the signal processing circuit
properly selected for each field (ST15).
[0284] At the start of correct data reproduction, the format
controller 26c can grasp the position on the track and the
determination result of the signal determining circuit 25 is used
no more.
[0285] Next, another embodiment is explained with reference to
FIGS. 26, 27. In this case, portions which are the same as those of
FIGS. 12, 14 are denoted by the same reference numerals and an
explanation thereof is omitted.
[0286] In this embodiment, one example of the construction of the
optical disk apparatus 21 is shown in a case where the recording
density of the header field 3, 8 in the linear direction is lowered
(coarse) and the pit/mark length is made large to make an amplitude
value large by using the same modulation code for the header field
3, 8 and user data recording field 11 and writing data having no
code with the minimum pit length into the header field 3, 8.
[0287] The signal processing system on the reproducing side is
constructed by two systems including a system (level slice signal
processing circuit 23') for processing the header field 3, 8
according to the level slice system to detect channel data and a
system (PRML signal processing circuit 24') for processing the user
data recording field 11 according to the PRML signal processing
system to detect channel data.
[0288] In the case of FIG. 27, the level slice signal processing
circuit 23' is constructed by removing the PLL circuit 55 and 8-16
RLL demodulator 56 from the level slice signal processing circuit
23 shown in FIG. 14 and the PRML signal processing circuit 24' is
constructed by removing the PLL circuit 67 and 1,7 RLL demodulator
66 from the PRML signal processing circuit 24 shown in FIG. 14.
[0289] In the case of FIG. 26, a PLL circuit 37 and demodulator 38
which are commonly used by the level slice signal processing
circuit 23' and PRML signal processing circuit 24' are
provided.
[0290] Further, the drive control circuit 26 supplies a selection
signal to the level slice signal processing circuit 23' or PRML
signal processing circuit 24' according to a determination signal
from the signal determining circuit 25 to perform the control
operation so that data now reproduced can be properly
processed.
[0291] At this time, the drive control circuit 26 supplies a
changeover signal for a phase difference detecting system to a
phase difference detecting circuit 37a in the PLL circuit 37
according to a determination signal from the signal determining
circuit 25 to perform the control operation so that data now
reproduced can be properly processed. Thus, the phase difference
detecting circuit 37a in the PLL circuit 37 generates a clock for
reproduction while a phase difference is detected by a phase
difference detecting system (detection of a phase difference by the
level slice system or detection of a phase difference by the PRML
system) suitably selected for the level slice signal processing
circuit 23' or PRML signal processing circuit 24'.
[0292] As a result, after channel data is detected, the data is
demodulated by the common demodulator 38.
[0293] Next, with the above construction, the data recording
process and data reproduction process in the optical disk apparatus
21 are explained with reference to the flowchart shown in FIG.
28.
[0294] Immediately after the seeking operation of the optical
pickup section 22 or when the format controller 26c deviates from
the tracing path by a disturbance or the like, that is, when the
format controller 26c cannot grasp the position on the track, the
following control process is effected.
[0295] That is, the signal determining circuit 25 checks the signal
level of a signal supplied from the optical pickup section 22 (ST1)
and determines whether or not it is the recording field 11 for
recording user data (ST2).
[0296] As a result of determination, if the signal determining
circuit 25 determines that it is the user data recording field 11,
the circuit 25 outputs a signal indicating the user data recording
field 11 to the drive control circuit 26 (ST3).
[0297] Then, the drive control circuit 26 outputs a selection
signal to the PRML signal processing circuit 24' and phase
difference detecting circuit 37a (ST4').
[0298] In step ST2, if the signal determining circuit 25 does not
determine the user data recording field 11, it outputs a signal
indicating the header field 3, 8 to the drive control circuit 26
(ST5).
[0299] Then, the drive control circuit 26 outputs a selection
signal to the level slice signal processing circuit 23 and phase
difference detecting circuit 37a (ST6').
[0300] While the PRML signal processing circuit 24 or level slice
signal processing circuit 23 is being selected by the selection
signal obtained in step ST4' or ST6', the drive control circuit 26
sets up synchronization of the format controller 26c and records
data or reproduces recorded data based on data from the signal
processing system properly selected for each field (ST7).
[0301] When data starts to be correctly reproduced, the format
controller 26c can grasp the position on the track and the
determination result of the signal determining circuit 25 is used
no more.
[0302] Next, another embodiment is explained with reference to FIG.
29. In the above embodiment, the header field 3, 8 is constructed
by four header fields and only one address mark AM is provided
before the address portion PID in each of the header fields, but
this is not limitative and, in another embodiment, a plurality of
address marks AM can be provided in one header field.
[0303] The layout of a header field 71 is shown in FIG. 29. In the
format of the header field 3, 8, four header fields are provided,
but in this example, it is assumed that only one header field 71 is
provided for simplicity, but this does not limit the number of
header fields 71.
[0304] The header field 71 has a significant feature in that AM
(address mark) patterns for detecting divisions between data items
are recorded in a plurality of portions of the same header field
71.
[0305] The header field 71 is constructed of 49 bytes and includes
a 36-byte sync code portion VFO (Variable Frequency 0scillator),
3-byte address mark AM, 4-byte address portion PID (Position
Identifier), 2-byte error detection code IED (ID Error Detection
Code), one-byte post amble PA and 3-byte address mark AM arranged
in this order from the left side.
[0306] With the above construction, the reliability at the time of
reproduction of information recorded in the header field 71 can be
significantly enhanced. That is, as shown in FIG. 29, in this
embodiment, the address marks AM for attaining data byte
synchronization are respectively provided before the address
portion PID and after the post amble PA.
[0307] Generally, synchronization is attained by use of the address
mark AM provided before the address portion PID to take out
succeeding individual information items and, if no error is
detected by the error detection code, it is supposed that correct
sector information and sector number can be obtained.
[0308] In this embodiment, even if an error is detected by use of
the error detection code, correct sector information and sector
number can be obtained by use of the following means in a case
where the detection error is caused only by use of the address mark
AM provided before the address portion PID. Since the address mark
AM provided before the address portion PID is placed in position
immediately after the sync code portion VFO, a detection error
tends to occur when the pull-in process of the PLL is delayed by a
disturbance. However, even in such a case, data after the address
portion PID is correctly read out in some cases.
[0309] Next, an ID detecting circuit 80 for detecting the address
portion PID in a case where one header field 71 has two address
marks AM is explained with reference to FIGS. 30, 31.
[0310] FIG. 30 shows the circuit construction of the ID detecting
circuit 80 and FIG. 31 is a circuit construction diagram of the
optical disk apparatus 21 having the ID detecting circuit 80
mounted thereon. In the case of FIG. 31, portions which are the
same as those of FIGS. 12, 14 are denoted by the same reference
numerals and an explanation thereof is omitted. However, it should
be noted that the changeover switches 59 in the signal determining
circuit 25 and level slice signal processing circuit 23 and the
changeover switch 70 in the PRML signal processing circuit 24 are
omitted.
[0311] As shown in FIG. 31, the ID detecting circuit 80 is provided
in the succeeding stage of the 8-16 RLL demodulator 56 which is the
last stage of the level slice signal processing circuit 23 for
processing the signal from the header field, detects ID information
based on binary data decoded by the 8-16 RLL demodulator 56 and the
channel clock from the PLL circuit 55 and outputs the detected ID
information to the drive control circuit 26.
[0312] As shown in FIG. 30, the ID detecting circuit 80 includes a
shift register 81, address mark detector (AM detector) 82, counter
83, ID information detector 84, stack register 85, changeover
switches 86a, 86b and stack counter 87.
[0313] The shift register 81 is supplied with channel bit data as
binary data decoded by the 8-16 RLL demodulator 56 at an input
terminal 81a and shifts the channel bit data for each bit to the
left direction in the drawing in synchronism with the channel
clock. The shift register 81 is required to have at least the
length capable of receiving all of the data of the header field 71
and is required to have a margin so as to save data for recovery
when the first address mark AM fails to be detected and store the
whole data even if the data is shifted due to the occurrence of an
error. For example, the shift register has a margin of several
bytes to several tens of bytes in addition to the data number of 49
bytes of the header field 71.
[0314] The AM detector 82 detects an address mark AM based on the
coincidence between AM patterns.
[0315] The counter 83 notifies that one-byte data is taken out and
supplied to the ID information detector 84 for every 16 bits.
[0316] The ID information detector 84 recovers sector information
and sector number from the readout channel bit pattern and detects
an error.
[0317] Further, the ID information detector 84 outputs an
instruction to the AM detector 82 again to detect the address mark
AM when the error detection code IED reading operation is ended so
as to make ready for a case wherein an error occurs.
[0318] The stack register 85 stacks a lower 16-bit channel data
pattern of the shift register 81 supplied via the switch 86a.
[0319] The changeover switches 86a, 86b are set on a node 86d side
when the top of the stacked data becomes the head address of the
address portion PID and puts the contents of the stack register 85
into the ID information detector 84.
[0320] The stack counter 87 counts the bytes (=16 channel bits)
after the shift register starts to reverse the shifting direction
and detects the depth of the stacked data until the top of the
stacked data becomes the head address of the address portion
PID.
[0321] With the above construction, the detection process of the ID
detecting circuit 80 is explained with reference to the flowchart
shown in FIG. 33.
[0322] A signal for starting detection of the address mark AM is
supplied from the format controller 26c to the AM detector 82
approximately at a time point when the header field is subjected to
the read process and the PLL operation starts to be converged
according to the VFO pattern. At the same time, data of the ID
field starts to be input to the input terminal 81a of the shift
register 81 (ST21). Thus, readout channel bit data is input to the
shift register 81 via the input terminal 81a and shifted for each
bit to the left direction in FIG. 33 in synchronism with the
channel clock.
[0323] In this case, it is assumed that data has been subjected to
8-16 modulation in the header field 3, 8, for example. Since the
address mark AM is 3 bytes, it is 48 bits in the channel code.
[0324] When coincidence of the 48-bit pattern is detected in the AM
detector 82, the AM pattern is detected (ST22) and an enable signal
is output to the counter 83 via a signal line 88. As a result, the
counter 83 is set into the enable state and starts to count the
channel clock. Since one-byte data corresponds to a 16-bit code on
the channel, the counter 83 informs the ID information detector 84
that one-byte data is taken out for every 16 bits.
[0325] At this time, the changeover switches 86a, 86b are set on
the node 86c side to permit lower 16-bit data of the shift register
81 to be input as it is to the ID information detector 84
(ST23).
[0326] The ID information detector 84 recovers the sector
information and sector number from the readout channel bit pattern
and detects an error (ST24). If no error is detected, a process for
starting access to the sector or a process for making preparation
for detection of the next sector is performed by the same operation
as in the conventional case (ST25).
[0327] When detecting the address mark AM provided after the post
amble PA, the AM detector 82 resets the counter 83 by use of a
signal supplied via the signal line 88, and at the same time,
reverses the shifting direction of the shift register 81 by use of
the signal from the signal line 89. The counter 83 re-starts to
count the channel clock and supplies a latch signal to the stack
register 85 for every 16 bits.
[0328] As a result, the lower 16-bit channel data pattern of the
shift register 81 is pushed into the stack register 85 via the
switch 86a. When the shifting direction of the shift register 81
starts to be reversed, the switch 86a is set on the node 86d side
to permit lower 16-bit data of the shift register 81 to be supplied
to the stack register 85.
[0329] The stack counter 87 counts bytes (=16 channel bits) after
the shifting direction of the shift register 81 starts to be
reversed and detects the depth of the stacked data until the top of
the stacked data becomes the head address of the address portion
PID. When the top of the stacked data becomes the head address of
the address portion PID, the switches 86a, 86b are set on the node
86d side so as to put the contents of the stack register 85 into
the ID information detector 84 (ST27).
[0330] The ID information detector 84 recovers sector information
and sector number from the readout channel bit pattern and detects
an error (ST28).
[0331] If no error is detected, a process for starting access to
the sector or a process for making preparation for detection of the
next sector is performed by use of the above information by the
same operation as in the conventional case.
[0332] Since the operation after the shifting direction of the sift
register 81 is reversed is a retrial operation using the address
mark AM provided in the rear portion when an error occurs in the
first ID detection process, the operation can be stopped at any
point in time if the first ID detection process is successfully
effected.
[0333] In this embodiment, the other address mark AM is provided
after the error detection code IED. Therefore, the ID information
detector 84 outputs an instruction to the AM detector 82 again to
detect the address mark AM when the error detection code IED
reading operation is ended so as to make ready for a case wherein
an error occurs. As shown in the steps ST31 to ST33 of FIG. 33, it
is possible to detect the other address mark AM before the error
detection result is determined by taking the detection time of the
error detection code IED into consideration.
[0334] In the above embodiment, the address marks AM are
distributed and arranged in two portions of the same header field,
but this is not limitative and the same operation can be attained
even if address marks AM are distributed and arranged in three or
more portions of the same header field.
[0335] Next, another embodiment in which the contents of the header
field are changed depending on the sector is explained. Generally,
when the recording density in the header field is lowered, the
header field is made longer if the amount of ID information is not
reduced, but in this embodiment, an increase in the length of the
header field is suppressed by reducing an amount of ID information
in the header field for each sector.
[0336] As one example, one ECC block is constructed by 16
2-kilobyte sectors in the optical disk 1 used for a DVD as shown in
FIG. 8, but in this case, ID information (refer to FIG. 29)
identical to that in the conventional case is recorded in the
header field 3, 8 of the head sector of the ECC block and only the
sector number or track number is recorded in the header field 3, 8
of the other sectors.
[0337] As another example, if ID information is constructed by four
bytes as shown in FIG. 34, the amount of ID information is reduced
by recording the least significant one byte in the header field of
each sector and distributing and recording the remaining three
bytes in the respective sectors.
[0338] A more specific example is shown in FIG. 35. A header field
of the conventional form in which ID information is constructed by
four bytes of ID information 1 to ID information 4, the contents of
the ID information 1 is "00010100", the contents of the ID
information 2 is "11001001", the contents of the ID information 3
is "00111101" and the contents of the ID information 4 is
"01100001" is considered and an example of ID information of a form
based on this embodiment and corresponding to the above form is
shown.
[0339] It is supposed that three successive sectors each having a
header field to which the ID information of this embodiment is
applied are provided. In the header field of the first sector, only
the ID information 1 and ID information 4 of the header of the
conventional form are recorded. That is, the contents of binary
data recorded in the header field become "00010100"+"01100001".
Only binary data obtained by incrementing the contents of the ID
information 4 by one and the ID information 2 of the header of the
conventional form are recorded in the header of the second
sector.
[0340] That is, the contents of the binary data recorded in the
header field become "11001001"+"01100010". The reason why the
contents of the second byte become a value obtained by incrementing
the contents of the ID information 4 of the header field of the
conventional form by one is that the ID information 4 is supposed
to be the least significant byte of the sector number and the
sector number is incremented by one. Only binary data obtained by
incrementing the contents of the ID information 4 by two and the ID
information 3 of the header of the conventional form are recorded
in the header of the third sector. That is, the contents of binary
data recorded in the header field become "00111101"+"01100011".
[0341] In this embodiment, since the whole portion of the ID
information cannot be obtained simply by reading one header field,
it takes a long time to obtain a correct sector number (block
number), for example. However, in a conventional ID information
recording method, when access is made to a large number of
successive header fields, the amount of information in a redundant
portion and readout time of the header field become useless since
most of the ID information is not so different in the adjacent
header fields.
[0342] In this embodiment, information which varies for each header
field is recorded in each header field and information of a portion
which does not change is distributed in a plurality of header
fields so as to enhance the efficiency of the readout time and
information amount.
[0343] As still another example, a system for supporting additional
writing and rewriting of written data is considered as a
recording/reproducing optical disk. That is, the system is a system
in which new data can be additionally written in a portion
immediately after a data field in which significant data is
written, data cannot be jumped to and written into a field
successive to a data field in which data has not been written and
the contents of a data field in which data has been already written
can be rewritten. Since data exists in the lead-in field of the
optical disk to which access is first made, initial writing can be
performed immediately after this field.
[0344] In the optical disk system with the above construction,
address information can be eliminated from the header field. Since
ID information is recorded together with user data in the sector or
ECC block in which data is already written, the access position can
be detected by reading out the above data. It is only required to
record a pattern used for synchronization of the start position of
the sector (block) in the header field.
[0345] As described above, a signal of the conventional level slice
system can be detected and detection delay time can be reduced by
setting the recording density of the header field in the linear
direction lower (coarse) than that of the user data recording
field.
[0346] Further, a signal of the conventional level slice system can
be detected and detection delay time can be reduced by using the
mark position form having a large detection margin as the
information recording system of the header field.
[0347] Further, a readout error of the sector number due to a
detection error can be compensated for by recording the address
marks AM for attaining byte synchronization of the header field in
both of the head portion and tail portion of information recorded
in the header field.
[0348] Thus, it becomes possible to provide an optical disk which
has a large capacity and is high in reliability and in which the
length of the to-be-changed field is reduced to improve the format
efficiency by suppressing the readout delay of the sector number of
the header field and a readout error of the sector number due to a
detection error of the data dividing pattern in the header field
can be compensated for.
[0349] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *