Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
2001-11-19
2002-12-17
Edun, Muhammad (Department: 2853)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S053150, C369S053100
Reexamination Certificate
active
06496460
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of managing defects in a disk recording medium, an optical disk device recording data on the optical disk using such a defect management method, and an optical disk capable of storing information concerning a defect criteria used for replacing a defective area of disk with a non-defective area.
A very high degree of reliability less than 10
−12
at worst is required of a disk used for recording computer data. Defect-managing systems have been used hitherto to accommodate the reality that defects in recording sectors which lead to an error are unavoidable, even very rare, in the current disk-manufacturing technique.
Disk mediums are subjected to the defect management for assuring data reliability even when dirt, scratches or degradation due to repetition of rewriting operation is caused. Primary defects occurring at the time of manufacture of the disks are found through a certifying process carried out at the time of initializing disks, and secondary defects occurring after being put to use are found through verification carried out at the time of writing, or the like. Sectors found to have a defect are replaced, using sectors located in a spare area formed on part of a disk other than a user area. In the defect management, a pair of a user area and a spare area is called a group.
In an example of arrangement of user areas and spare areas on a disk, the data area consists of a single group. However, there are many optical disks in which a data area is divided into a plurality of groups. When a defective group is found in a group, it is first attempted to replace the defective sectors using sectors in a spare area of the same group. In many cases, an optical disk is configured such that a recording capacity of a spare area is several % of that of a user area. The 90 mm magneto-optic disk standard defined by ECMA-154 or ECMA-201, and the DVD-RAM standard defined by ECMA-272 are examples of such configuration.
Incidentally ECMA is an abbreviation of European Computer Manufacturers Association, DVD is an abbreviation of digital video disk, and RAM is an abbreviation of random-access memory.
The presence or absence of a defect in a sector can be determined by an error in an ID signal representing a physical address of the sector, an error in a recorded data signal, or a servo error signal.
When a plurality of ID's are recorded in the header area for each sector, if not less than a predetermined number of ID's for each sector contain an error, the sector in question is found to have a header defect. In the DVD-RAM standard for example, each sector is provided with four ID's, and an error can be detected for each ID. Each sector is found not to have a header defect if it has not more than two ID errors: a sector having three or more ID errors is found to have a header defect, since its reliability is low.
Further, the presence or absence of an error in a recorded data signal is detected by the use of an error correcting code added thereto. When more than a predetermined number of errors are included per unit of recording, the data signal is found to have a data defect. The “unit of recording” may be a sector or a block constituted of a plurality of sectors depending on the span of an error correcting code (ECC).
In the DVD-RAM standard, data is recorded in sectors on a disk, and is subjected to error-correcting coding in units of 16 sectors, called an ECC block. Data of 32 KB constituting one ECC block is arranged in the form of matrix of 172×192 bytes (or 172 columns×192 rows), and Reed-Solomon codes (inner code PI, outer code PO) of 10 bytes and 16 bytes are added in column direction and row direction, respectively, to constitute a product code.
The inner code PI is disposed so as to be completely within a sector. By means of the inner code PI, the number of error bytes in each row of the reproduced data can be determined. In accordance with the detected number of errors, reliability of each row is evaluated, and whether each sector or each block has a data defect can be determined based on the number. For instance, a sector including four or more rows having four or more error bytes is found to have a data defect, or a block including six or more such rows are found to have a data defect.
With regard to detection of defects based on a servo error signal, when the magnitude of the servo error signal such as a tracking error signal exceeds a predetermined value that makes it difficult to ensure the servo control stability required of data recording, a sector in question is found to have a servo defect.
When a sector is found to have a header defect, a data defect or a servo defect, it is found to be defective.
Generally, in the defect management, two different methods are used for performing replacement of a sector. One is a slip replacement, and the other is a linear replacement.
The slip replacement is applied to primary defects. If a defective sector is found at the time of certifying a disk, the next sector is used in place of the defective sector. In a disk drive device, for accessing a sector containing data, a logical address is converted into a physical address representing the position of the sector, and a sector having ID's representing the physical address is accessed. When the slip replacement has been performed, the physical address numbers corresponding to the logical addresses are shifted, or “slip” by one.
The slip replacement is carried out within each group. For instance, if there occur two slip replacements of m sectors and n sectors in a user area, the end of the user area of the group is shifted into the head of the spare area by (m+n) sectors. If such slip replacements are made, the linking relation between the physical addresses and logical addresses is shifted by the number of replaced sectors for all the sectors succeeding the replaced sectors. Primary defects subjected to the slip replacement are registered in a PDL (Primary Defect List). The list contains the physical addresses of defective sectors in each entry.
Linking the physical addresses with the logical addresses can be made only when a disk is initialized, and therefore, the slip replacement is applied to primary defects only.
The linear replacement is applied to secondary defects. When a defective sector is found, replacement is effected using spare sectors in a spare area. When an ECC block (formed of 16 sectors) is found to contain a defective sector, the entire ECC block is replaced with 16 sectors in a spare area. There may be a case where a block in a spare area having replaced another block is subsequently replaced with another block. A substitutive sectors are given the same logical addresses as the original sectors.
The linear replacement is effected within the same group first. For instance, when two linear replacements of m blocks and n blocks respectively occur in a user area, m blocks and n blocks at the beginning of the unused part of the spare area are used. It may be so designed that when the spare area of the same group has been used up the spare area in another group is used. Secondary defects subjected to linear replacement are registered in an SDL (Secondary Defect List). The list contains physical addresses of defective sectors and substitutive sectors in each entry.
When such a linear replacement has been made, every time an access is made using a logical address which designated a substitutive sector, an access to the substitutive sector and subsequent return have to be made. Therefore, the average data transfer rate is substantially lowered when the secondary defects exist.
A set of the defect lists PDL and SDL is stored in a defect management area within a control information area in each of outer and inner periphery parts. They are disposed at a plurality of locations, and they are recorded together with information on the structure of a disk.
Generally, in recording devices, criteria for detecting primary and secondary defects are set in the following way.
A di
Nakane Kazuhiko
Ohata Hiroyuki
Edun Muhammad
Mitsubishi Denki & Kabushiki Kaisha
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