Dynamic information storage or retrieval – Information location or remote operator actuated control – Selective addressing of storage medium
Reexamination Certificate
1999-12-20
2002-05-07
Dinh, Tan (Department: 2651)
Dynamic information storage or retrieval
Information location or remote operator actuated control
Selective addressing of storage medium
C369S030270
Reexamination Certificate
active
06385144
ABSTRACT:
The present invention relates to control of movement of a head in a storage device which can use a medium having concentric or spiral tracks. More particularly, the invention relates to head position control in storage devices having a plurality of guard areas which do not include position information (ID).
BACKGROUND OF THE INVENTION
In recent years, disk type computer media such as phase change type disks and magneto-optical disks or the like are being developed, in addition to floppy disk, hard disk and card/tape type optical storage technology.
In comparison with a floppy disk or a hard disk, an optical disk is capable of drastically increasing the recording capacity by forming recording pits of the sub-micron order on the medium, using a laser beam.
Moreover, information rewriting of a hundred thousand times or more is possible for a magneto-optical disk utilizing a rare earth-transition metal based material, and expectations are high for this magneto-optical disk. Recently, development has been made for such an optical disk having storage capacity of 540 MB to 640 MB at one surface of a 3.5 inch disk.
The storage capacity of a typical floppy disk of 3.5 inch is about 1 MB, so the storage capacity of an optical disk is equal to that of 540 to 640 floppy disks. As described, an optical disk is a rewritable storage medium having a much higher recording density.
However, the recording density of an optical disk must be further raised from the current density, in preparation for the future multi-media era. In order to raise the recording density, more pits must be recorded on the medium. Therefore, the current pit must be further reduced in size and the interval between pits must also be reduced.
In the case of raising the recording density with such a method, the wavelength of the laser beam has to be further reduced from the current 670 nm, but when practical use is considered, the pit size must be reduced even in the current wavelength of 670 nm.
It is possible to form the pit smaller than the beam diameter by controlling the power of the laser beam when recording. However, in regard to reproduction, when a pit smaller than the beam diameter is formed, crosstalk with a neighboring pit increases. In the worst case, the neighboring pit is entered in the reproduced beam. Thus, normal reproduction is very difficult when practical use is considered.
As a method for reproducing the pit smaller than the beam diameter in the current wavelength of 670 nm, MSR (Magnetically induced Super Resolution) has been proposed. The principle of MSR, namely rare earth—transmission metal based film material of a magneto-optical recording medium layer consisting of a reproducing layer, a switch layer (intermediate layer) and a recording layer, and a method of manufacturing a magneto-optical storage medium, are disclosed in detail in Japanese Published Unexamined Patent Application Nos. HEI 7-244877, HEI 9-147436 and HEI 10-134429, and others.
An optical storage medium used in an optical disk apparatus has, as illustrated in
FIG. 1
, concentric or spiral tracks divided into a plurality of sectors. The sectors are alternately provided with recording areas (DATA areas) for recording and/or reproducing data and header areas (ID area) formed of the recessed and projected pits.
In the ID area, a sector mark (SM) indicating the position of a sector, position information (ID information) such as track number, sector number, etc. and VFO such as a synchronous pattern are recorded.
The target sector of the target track can be positioned by the relative movement (tracking) of the head in the traveling direction (track following direction)
121
with rotation of the optical storage medium.
Moreover, the operation for moving the head with a carriage or lens actuator (track actuator) in the direction (disk medium radius direction)
123
crossing the tracks in order to move the head to the target track at a high speed to record/reproduce the information on the medium is called the seek operation.
Under the seek control, when the ID (track No., sector No.) is issued, as the target position of movement, via an interface controller from a host, the optical disk apparatus immediately reads the ID (track No., sector No.) of the current position with the carriage
122
in order to identify the current position.
The amount of movement required, i.e., the difference between the target position and the current position, is calculated with the MPU. This amount of movement is converted to the number of tracks to be jumped and it is then set to a DSP (Digital Signal Processor) as a VCM (Voice Coil Motor) drive controlling means for driving the carriage
122
. Therefore, the carriage executes the seek operation in the traveling direction
123
by instructing a drive current of the VCM from the DSP via the driver.
For the storage medium of the related art, ID exists for all tracks in the range where the head moves, namely in the track jump range of the track actuator in which the lens can precisely move in the track crossing direction and in the seek range of the carriage. Therefore, the current position (track No., sector No.) can be detected immediately by reading the ID.
In these years, a high density storage medium in which track interval is reduced from the current interval to form more tracks by utilizing the MSR technology is being developed. Almost all optical disk media employ the ZCAV system, in which a predetermined number of tracks are defined as one zone and control for making the angular velocity constant is performed for a plurality of zones.
The latest high density storage medium technology has a problem in the recording, erasing and reproducing operations at the boundary of zones, due to realization of higher track density.
Therefore, as illustrated in
FIG. 2
, guard areas are provided between zones of tracks (track grooves are formed like ordinary tracks) but the ID area and DATA area do not exist in the track at the boundary of zones. Accordingly, the number of guard areas depends on the number of zones.
Guard areas prevent interference with respective tracks of neighboring zones, and are used because track density is higher than it is in the related art. Namely, about 10 tracks are provided in one guard area. Although it is a matter of course, the data areas in the ordinary tracks have the ID area and DATA area as in the case of FIG.
1
.
When the head is positioned (on-track) to this guard area in the seek method of the related art, since ID does not exist, as illustrated in
FIG. 3
, an error that ID cannot be read is judged and therefore the ordinary error recovery process, which is based on the to existence of ID, is executed.
However, in the high density storage medium of the new system, ID cannot be read even with any kind of method because the ID does not intrinsically exist. Accordingly, the track number and sector number cannot be recognized and error recovery is conducted for a long period of time. As a result, time is wasted. In addition, a seek error is also generated, lowering reliability of the medium and apparatus.
FIG. 3
illustrates the recovery process when ID cannot be read in the medium of the related art. The ordinary recovery process means this flowchart. The step S
1
indicates that the target track is instructed and seek is completed. In order to detect the seek end position, the ID is read in step S
2
.
As a result, operation transfers to the ordinary process when ID can be read in step S
3
. If ID cannot be read, the recovery process starts from step S
4
. Factors for searching for the cause of error are sequentially detected.
In step S
4
, it is determined whether or not forcible ejection is occurring. If it is a cause, exclusive recovery is conducted. When it is not a cause, whether LD is erased or not is detected in step S
5
.
When it is not a cause, it is detected in step S
6
whether or not the spindle is stopped. If it is a cause, exclusive recovery is conducted. When it is not a cause, whether VCM over-current is detected in step S
7
. If that is a cause, exclusive rec
Kuriuzawa Toshio
Yanagi Shigenori
Dinh Tan
Fujitsu Limited
Greer Burns & Crain Ltd.
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