Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Reexamination Certificate
2000-03-16
2003-12-02
Neyzari, Ali (Department: 2655)
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
C369S030120, C369S059120
Reexamination Certificate
active
06657947
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to information recording media which has error detecting codes, as pre-format information, for detecting erroneous address numbers. More specifically, the invention relates to information recording media in which it is possible to reduce the cross talk of the reproduced signals of error detecting codes between adjacent tracks in order to securely or reliably detect the errors of the address numbers and read the address information on the tracks.
2. Description of Related Art
The multimedia era having come, optical disks are known as information recording media which can take or cover a great quantity of data such as voice and dynamic images. An optical disk has concentric or spiral tracks which are numbered generally in radially outward (or inward) order. As shown in
FIG. 3
, each of the tracks is divided into sectors, in each of which information can be recorded and reproduced.
Each of the sectors has pre-format information formed as pre-pits at its front. As shown in
FIG. 3
, the pre-format information consists mainly of a sector mark, a VFO, an address mark, address data and a CRC (cyclic redundancy check) code. By reading the pre-pits, it is possible to obtain the address information. On the basis of the obtained address information, information is recorded in, and/or read from, the data region of the sector. The sector mark is a data pattern indicating the front of the sector. The VFO (variable frequency oscillator) is a code pattern for timing control in reading the address data positioned just at the back of it. The address mark is a code pattern indicating the starting position or point of the address data. Recorded as the address data are data representing the track number of the associated track and the sector number. The CRC code is an error detecting code for instantaneously detecting whether the address data read out just before it is correct. The CRC code is generated on the basis of the track number and the sector number.
The information recording media proposed for larger capacity in recent years include an optical recording medium having a track pitch narrowed for higher recording density in the directions across the tracks of the medium. The proposed media also include a land-groove (land and groove) type optical recording medium, of which both the lands and the grooves are used as tracks for higher recording density. The pre-pits in the sectors of an optical recording disk are adjacent to each other in the radial direction. Therefore, if the track pitch of the disk is narrowed, or if both the lands and the grooves of the disk are used as tracks, the pre-pits in each track of the disk are close to those in the adjacent tracks. Consequently, when information is read from the pre-pits in one of the tracks, signals may leak from the pre-pits in the adjacent tracks, that is to say, cross talk may occur.
In particular, because the CRC code of the pre-format information is generated on the basis of the track and sector numbers, the data trains of the CRC codes in the “n”th track from which information is being read differs entirely from those of the CRC codes in the adjacent “n+1”th and “n−1”th tracks. This makes cross talk liable to affect the CRC codes. If it is impossible under the influence of cross talk to correctly read out the CRC codes for detection of errors, it is impossible to correctly detect whether the address data read out before each CRC code is accurate. In other words, even if the address data is correctly read out, it may be judged to be erroneous. Accordingly, the cross talk from the adjacent tracks is a very serious problem in address data error detection.
In the land-groove type optical recording medium, sector marks and/or ID data which include address information are recorded in both the lands and grooves. For example, when information is read from one of the lands (or grooves), cross talk occurs from the adjacent grooves or groove (or lands or land), making it difficult to correctly read the address information from the lands.
In view of the above problems, Japanese Patent Application Laid-Open No. 8-339540 discloses an optical recording medium for recording in lands and grooves. This recording medium has sectors each including a sector ID region. This ID region consists of a sector mark indicating the front of the sector, an ID data zone and a space without a pit. The space of each of the sector ID regions formed in a groove is positioned adjacent to the ID data zone of one of the sector ID regions formed in a land. Likewise, the space of each of the sector ID regions in a land adjoins the ID data zone of one of the sector ID regions in a groove. Specifically, each sector ID region in each groove consists of a sector mark, a space and an ID data zone in that order, while each sector ID region in each land consists of a sector mark, an ID data zone and a space in that order. Each of the ID data zones is a data train consisting of a VFO, an address mark, address data and a CRC code.
The space of each sector ID region is equivalent in area to the ID data zone, which consists of a VFO, an address mark, address data and a CRC code, of each sector ID region. The area of the spaces of the sector ID regions restricts the recording capacity of the optical recording medium. The capacity restriction does not match the need for recording densification or higher recording density.
SUMMARY OF THE INVENTION
The present invention has been made for solution of the problems with, and the disadvantages of, the prior art. A first object of the invention is to provide an information recording medium having novel error detecting codes as pre-format information which can be less affected by cross talk from the adjacent tracks.
A second object of the invention is to provide an information recording medium which can be less affected by cross talk from the adjacent tracks, and which can realize larger capacity.
A third object of the invention is to provide a novel error detecting method which can detect the error of address information reliably with little influence of cross talk from the adjacent tracks.
According to a first aspect of the invention, there is provided an information recording medium having a plurality of tracks each sectioned into sectors, the medium being characterized in:
that each of the sectors has a mark representing address data which represents the address of the associated sector and a mark representing an error detecting code for detection of the error of the address data; and
that the error detecting codes of the tracks are so formed that the distance between the detecting codes of any adjacent tracks is always 1.
The error detecting codes for detection of the errors of the address data of this information recording medium are so formed that the distance between the codes of adjacent tracks is always 1. In other words, the detecting codes are constructed in such a manner that, when the codes of adjacent tracks are compared, there is only one reverse bit. Consequently, when the detecting code of one of adjacent tracks is read out, there is only one place where signal leakage (cross talk) may occur from the other track. This minimizes the influence of cross talk. Therefore, even if the recording medium has a narrow track pitch, it is possible to reliably read out the detecting codes, making it possible to reliably detect the errors of the address data.
In this specification, the term “mark/s” is/are the concept of any marks formed by changes in physical or chemical shape, material or structure. The marks may be pits formed in any shape in a substrate, magnetic marks formed in accordance with the directions of magnetization on a magnetic film, marks formed on the basis of a change of phase between the crystalline and amorphous substances on a phase change film, or marks formed on the basis of a change of shape or material with heat, light and/or the like on an organic pigment film.
In this invention, generation of such error detecting codes that
Fujitani Shigeo
Ishizaki Osamu
Hitachi Maxell Ltd.
Neyzari Ali
Oliff & Berridg,e PLC
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