Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Reexamination Certificate
1998-03-16
2001-11-27
Psitos, Aristotelis M. (Department: 2651)
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
Reexamination Certificate
active
06324157
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a medium in the shape of a disk, a tape or a card, such as an information recording medium where identification data is irreversibly recorded, and also to a recording/reproducing apparatus for reading the identification data from the information recording medium.
A magneto-optical disk can store a large volume of information with a portable size, and application of such a magneto-optical disk has been examined as a core recording medium in the rapidly developing multi-media. Since mass information can be recorded in a magneto-optical disk, management of information recorded therein, for example, prevention of illegal usage of the information has become very significant.
The present applicant has proposed a method of protecting information by using a medium identification code peculiar to each optical disk in Japanese Patent Application Laid-Open No. 5-257816 (1993). In this publication, however, a method of forming the medium identification code is not described, and the illegal usage of information cannot be actually prevented.
In order to definitely prevent the illegal usage of information, the present applicant has described a method of forming the medium identification code in Japanese Patent Application Laid-Open No. 9-73680 (1997). In this method, a medium identification code with a predetermined number of bits is irreversibly, namely, unrewritably recorded in a magneto-optical disk. An erasing operation is conducted on an area where the medium identification code is recorded, so as to judge whether or not a magneto-optical disk in use is a genuine product. When the medium identification code is not erased, the magneto-optical disk is genuine, and when it is erased, the magneto-optical disk is a copied product, and hence, information recorded therein is prohibited to be used.
The illegal usage of information can be thus prevented. However, a reproduced signal obtained from the irreversibly recorded medium identification code has such a small signal amplitude that there can be a case where the signal cannot be identified as the medium identification signal. As a countermeasure, the present applicant has described, in Japanese Patent Application No. 8-278466 (1996), an information recording medium where identification data is recorded by using an arrangement of irreversibly recorded unit areas and non-irreversibly recorded unit areas. In reading the identification data from this information recording medium, binary data is not read by using a difference of a signal amplitude but it is judged whether or not a read area is an irreversibly recorded area.
In reading such identification data, when a reproduced signal obtained from an irreversibly recorded area has a value approximate to a threshold value of binary data, an error in binarization can disadvantageously lead to a mistake in the judgement of the area.
BRIEF SUMMARY OF THE INVENTION
The present invention was devised to overcome the aforementioned problems. One object of the invention is providing a recording/reproducing apparatus which can read irreversible data from an information recording medium where the irreversible data is recorded, providing a recording/reproducing apparatus which can avoid a mistake in judging whether or not a unit area is an irreversibly recorded area, and providing an information recording medium from which irreversible data can be rapidly read by changing a frequency of error correction.
Another object of the invention is providing an information recording medium in which judgement of a unit area can be prevented from being affected by heat used in an irreversible recording operation by providing a buffer area not concerning irreversible data between an irreversibly recorded unit area and a following unit area.
Still another object of the invention is providing an information recording medium from which irreversible data can be accurately read by additionally recording error correction code data for the irreversible data therein.
The recording/reproducing apparatus of this invention comprises storage means for storing a predetermined code; recording means for recording the predetermined code in a predetermined area of the information recording medium; reproducing means for reproducing the predetermined code having been recorded in the predetermined area as a reproduced code; comparing means for comparing the predetermined code and the reproduced code; judging means for judging, as a result of comparison, the predetermined area to be an irreversible area when the predetermined code and the reproduced code do not accord with each other and to be a reversible area when the predetermined code and the reproduced code accord with each other; and reading means for receiving a result of judgement and reading the irreversible data.
Accordingly, it is possible to determine whether or not the predetermined code has been normally recorded by comparing the recorded predetermined code with the reproduced code obtained by reproducing the predetermined code by the comparing means. Since the predetermined code cannot be normally recorded in an irreversible area, the predetermined code does not accord with the reproduced code, namely, the area where the predetermined code is not normally recorded can be judged to be an irreversible area.
Alternatively, the recording/reproducing apparatus of this invention comprises storage means for storing a predetermined code; recording means for recording the predetermined code and error correction code data in a predetermined area of the information recording medium; reproducing means for reproducing the predetermined code and the error correction code data having been recorded in the predetermined area; error correcting means for conducting error correction by using the predetermined code and the error correction code data having been reproduced; judging means for judging the predetermined area to be an irreversible area when the error correction is abnormally completed and to be a reversible area when the error correction is normally completed; and reading means for receiving a result of judgement and reading the irreversible data.
Accordingly, the error correcting means determines whether or not the reproduced code includes an error and whether or not the error of the reproduced code can be corrected by using the error correction code data. Since the predetermined code cannot be normally recorded in an irreversible area, when the reproduced predetermined code cannot be corrected by using the error correction code data, namely, when the error correction is abnormally completed, the predetermined area can be judged to be an irreversible area.
Furthermore, the recording/reproducing apparatus can further comprises instructing means for instructing a subsequent predetermined area after the judgement of the predetermined area, and the reading means reads the irreversible data after the judgement of all predetermined areas on the basis of an arrangement of the predetermined areas.
Accordingly, the plural predetermined areas are successively reproduced, so that the respective areas can be judged to be an irreversible area or a reversible area. The reading means reads the irreversible data on the basis of the arrangement of the predetermined areas after receiving the results of the judgement.
In one aspect of the recording/reproducing apparatus, the instructing means specifies, when the predetermined area is judged to be an irreversible area by the judging means, a subsequent predetermined area excluding a buffer area, which is disposed between the irreversible area and a following unit area and do not concern the irreversible data.
Accordingly, the instructing means specifies reproduction of a subsequent predetermined area with the buffer area excluded. The buffer area is disposed on the back side along the track of each irreversible area, and can easily affect the judgement of an irreversible area due to heat used in the irreversible recording operation. The buffer area does not concern the irreversible data and
Fujitsu Limited
Greer Burns & Crain Ltd.
Psitos Aristotelis M.
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