Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Control of information signal processing channel
Reexamination Certificate
2001-06-27
2004-10-26
Tran, Thang V. (Department: 2653)
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Control of information signal processing channel
Reexamination Certificate
active
06809998
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disk drive for handling a disk-shaped record medium such as a magneto-optic disk, and a method for processing data using the same. Specifically, the present invention relates to an optical disk drive structured in such a manner that a reference clock having a frequency corresponding to a reproduction frequency of data reproduced from a data recording region is divided in accordance with a ratio between a record density of a header region where pre-formatted data including a sector mark for indicating a leading position of a sector is recorded, and a recording density of a data recording region subsequent to the header region, so as to produce a sampling clock, and by use of thus-produced sampling clock, the sector mark is detected. This structure enables, even if the header region has a recording density different from the recording density of the data region, to use a sector mark detector having the same structure as of a sector mark detector which is employed in the case where the header region has the same recording density as that of the data region and therefore a reference clock is used, thereby producing the optical disk drive at a low cost.
2. Description of the Related Art
FIG. 1
is a diagram showing a sector format of a magneto-optic disk (ISO/IEC 15286) of 5.2 GB on each of its sides. The numbers in
FIG. 1
indicate numbers of bytes.
One sector is divided into a header, a transition area TA
1
, an ALPC gap, a VFO
3
, a sync-field, a data field, a postamble PA
2
, a buffer field, and a transition area TA
2
in order of recording/reproduction.
This sector is broadly constituted by an address section (i.e. a header) and a data section. At the front and back of the data section, the ALPC gap, the transition area TA
1
, and the TA
2
are placed. The header is a region exclusively used for reproduction, and in the header, so-called emboss pit are pre-formatted and recorded. The area other than the header, that is, the area from the transition area TA
1
to the transition area TA
2
is a magneto-optic (MO) area.
The header of 64 bytes as the address section is constituted by a sector mark SM (8 bytes), VFO
1
in the VFO field (26 bytes), an address mark AM
1
(1 byte), ID
1
in the ID field (5 bytes), VFO
2
in the VFO field (16 bytes), an address mark AM
2
(1 byte), ID
2
in the ID field (5 bytes), and postamble PA
1
(2 bytes) in this order.
The sector mark SM is a mark used for identifying the initiation of the sector. The sector mark SM has a pattern which is formed by embossing and will not occur by (1-7) RLL code or (2-7) RLL code.
The VFO field is used to synchronize the variable frequency oscillator (VFO) at a phase-locked loop (PLL) section in the disk drive. In other words, the VFO field is a field into which the phase-locked loop is retracted. The VFO field in one sector is constituted by VFO
1
, VFO
2
, and VFO
3
. In the address section, VFO
1
and VFO
2
are formed by embossing. VFO
3
is provided in the data section, and when data is recorded in the sector, the data is magneto-optically recorded in the VFO
3
.
In VFO
1
and VFO
2
, recorded is a signal with a predetermined pattern for retracting the phase-locked loop (i.e. for generating a read clock) to read the data from the header. On the other hand, in VFO
3
, recorded is a signal with a predetermined pattern for retracting the phase-locked loop (i.e. for generating a read clock) to read the data from the data section.
The address marks AM
1
, AM
2
are used for synchronization of bytes for the subsequent ID field, and have predetermined patterns. In the address section, the address marks AM
1
, AM
2
are formed by embossing. The ID field is constituted by sector address information, that is, information about track number and sector number (3 bytes), and CRC byte (2 bytes) for detecting error which has occurred in the track number and sector number information in this order. Into the ID fields ID
1
, ID
2
, each having 5 bytes, the same data is recorded. In the address section, ID
1
and ID
2
are formed by embossing.
Subsequent to the header, an ALPC gap is placed via the transition area TA
1
. The ALPC gap is used for obtaining time that the disk drive needs for the processing performed after the reading from the header is completed, for permitting the displacement of the position of the subsequent VFO
3
, for testing laser power at the time of recording, and the like.
The data section is constituted by VFO
3
, a sync-field, a data field, postamble PA
2
, and a buffer field. The sync-field is used for synchronization of bytes for the data field subsequent to the sync-field, and has a predetermined bit pattern.
The data field is provided for recording user data. In the data field, 2048 bytes are reserved for the user data. In addition to the user data, parities, and the like for error detection and error correction are also recorded in the data field. As a result, the data field has 2498 bytes. The buffer field is a margin for rotation jitter.
FIG. 2
is a diagram showing a data structure of a magneto-optic disk having 2048 byte/sector.
“SB
1
” to “SB
4
” are sync bytes, and are synchronization signals which are recorded in the sync-field described above. “RS
1
” to “RS
59
” are resync bytes for resynchronization, and are provided at every 40 bytes, that is, at every 2 interleaves. “D
1
” to “D
2048
” are user bytes, and are provided into a length of 20 bytes in a column direction and sequentially in a row direction. “SWF
1
” and “SWF
2
” are sector written flag (SWF) bytes. “C
1
” to “C
4
” are CRC bytes. “E
1
,
1
” to “E
20
,
16
” are parities for error correction. The parities are generated in a row direction.
In the magneto-optic disk of 5.2 GB on each of its sides, the header (i.e. the address section) and the data section have the same recording densities with each other. Hereinafter, the process of reading data from this magneto-optic disk will be briefly described.
First, a sector mark is detected from the reproduction data by use of a reference clock having a frequency which corresponds to the reproduction frequency of the data to be reproduced from the data section. As a result of detecting the sector mark, it is acknowledged that there is an ID field located in a rearward position. Then, an address mark AM
1
is detected from the reproduction data by use of the read clock obtained by retracting phase-locked loop into VFO
1
. In this case, in order to prevent erroneous detection, a detection window for address mark is created. The detection of address mark is permitted only during the period when the window is opened. The detection window is created based on a count value obtained by counting the reference clock based on the position where the sector mark is detected.
When the address mark AM
1
is detected, the ID field ID
1
of 5 bytes subsequent to the address mark AM
1
is read and decoded to obtain sector address information (i.e. information about track number and sector number). From the sector address information, the current position is acknowledged. The same process is performed in the subsequent VFO
2
, AM
2
, and ID
2
. If it is impossible to read ID
1
, the current position is acknowledged in ID
2
. As a result of acknowledging the current position, if the sector is a target sector, the reading from the data field is performed. At this time, the data field is different from the ID field only in that the data field has sync bytes and resync bytes, instead of address mark.
In recent years, as one of techniques for giving higher density to magneto-optic disks, a magnetically induced super resolution (MSR) reproduction method has been suggested. The MSR reproduction method is a technique capable of reading recorded information from a region having an area smaller than a laser beam spot, by use of magnetic films having different temperature characteristics from each other. It is possible, therefore, to read information recorded in high density from MSR media with no need of reducing the dia
Frommer William S.
Frommer & Lawrence & Haug LLP
Sony Corporation
Tran Thang V.
Vuong Bach
LandOfFree
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