Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Reexamination Certificate
2002-04-10
2003-08-19
Tran, Thang V. (Department: 2653)
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
C369S047210, C369S047310
Reexamination Certificate
active
06608810
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disk on which information (e.g., digital video information) can be stored at a high density.
2. Description of the Related Art
In recent years, the recording density of optical disk media goes on increasing. On an optical disk medium, a track groove has normally been formed in advance and a recording film has been formed so as to cover the track groove. Data or information is written by the user on the recording film along the track groove, i.e., either on the track groove or on an area (land) interposed between adjacent parts of the track groove.
The track groove is formed so as to wobble just like a sine wave and a clock signal is generated in accordance with a wobble period. Synchronously with this clock signal, user data is written on, or read out from, the recording film.
To write data at a predetermined position on an optical disk, address information (positional information), indicating physical locations on the optical disk, needs to be allocated to, and recorded at, respective sites on the optical disk while the disk is being manufactured. Normally, an address is allocated to a series of areas that are arranged along a track groove and have a predetermined length. There are various methods for recording such address information on an optical disk. Hereinafter, a conventional method for recording an address on an optical disk will be described.
Japanese Laid-Open Publication No. 6-309672 discloses a disk storage medium on which a wobbling track groove is discontinued locally so that an address-dedicated area is provided for the discontinued part. Pre-pits, representing address information recorded, are formed on the address-dedicated area on the track groove. This optical disk has a structure in which the address-dedicated area and a data-dedicated area (for writing information thereon) coexist on the same track groove.
Japanese Laid-Open Publication No. 5-189934 discloses an optical disk on which address information is recorded by changing the wobble frequency of a track groove. In an optical disk like this, an area on which the address information is recorded and an area on which data will be written are not separated from each other along the track.
Japanese Laid-Open Publication No. 9-326138 discloses an optical disk on which pre-pits are formed between adjacent parts of a track groove. These pre-pits represent the address information recorded.
These various types of optical disks have the following problems to be solved for the purpose of further increasing the recording density.
First, as for the optical disk on which address information is recorded as pre-bits within the address-dedicated area on the track, a so-called “overhead” occurs to secure the address-dedicated area and the data area should be reduced disadvantageously. As a result, the storage capacity available for the user has to be reduced.
Next, as for the optical disk for recording an address thereon by modulating the wobble frequency of the track, a write clock signal cannot be generated precisely enough. Originally, the wobble of the track groove is created mainly to generate a clock signal for establishing synchronization required for read and write operations. Where the wobble frequency is single, a clock signal can be generated highly precisely by getting a read signal, having amplitude changing with the wobble, synchronized and multiplied by a PLL, for example. However, if the wobble frequency is not single but has multiple frequency components, then the frequency band that the PLL can follow up should be lowered (as compared to the situation where the wobble has a single frequency) to avoid pseudo locking of the PLL. In that case, the PLL cannot sufficiently follow up the jitter of a disk motor or a jitter resulting from the eccentricity of a disk. Thus, some jitter might remain in the resultant recording signal.
On the other hand, where the recording film formed on the optical disk is a phase-change film, for example, such a recording film may result in a decreased SNR as the data stored on the film is altered repeatedly. If the wobble frequency is single, the noise components are removable using a band-pass filter having a narrow band. However, if the wobble frequency has been modulated, the filter should have its bandwidth broadened. As a result, the noise components are much more likely contained and the jitter might be further worsened. It is expected that the recording density will be further increased from now on. However, the higher the recording density, the narrower the allowable jitter margin will get. Accordingly, it will be more and more necessary to minimize the increase in jitter by avoiding the modulation of the wobble frequency.
In the structure in which the pre-pits representing the address information recorded are formed between adjacent parts of the groove, it is difficult to form long enough pre-pits in sufficiently large numbers. Accordingly, as the recording density is increased, detection errors might increase its number. This is because if large pre-pits are formed between adjacent parts of the groove, then those pits will affect adjacent parts of the track.
In order to solve the problems described above, a main object of the present invention is to provide an optical disk medium that contributes to minimizing the overhead and generating a clock signal precisely enough in accordance with the wobble of the track groove.
Another object of this invention is to provide a method and apparatus for reading an address that has been recorded on the optical disk medium.
SUMMARY OF THE INVENTION
An optical disk medium according to the present invention includes a track groove. On the optical disk medium, information is recorded along the track groove. The track groove includes a plurality of unit sections that are arranged along the track groove and that have side faces displaced periodically along the track groove. The side faces of the unit sections are displaced in a single fundamental period. Subdivided information allocated to each said unit section is represented by a shape given to the unit section.
In a preferred embodiment, the side faces of the track groove are displaced either toward inner or outer periphery of the disk with respect to a centerline of the track groove.
In another preferred embodiment, the information is recorded on a block-by-block basis. Each said block has a predetermined length and includes a number N of unit sections that are arranged along the track groove.
In another preferred embodiment, part of the side faces that is shared by at least two of the unit sections has a constant displacement period within at least one of the blocks.
In another preferred embodiment, one-bit subdivided information is allocated to each said unit section, and a group of subdivided information representing N bits is recorded on the N unit sections that are included in each said block.
In another preferred embodiment, each said N-bit subdivided information group includes address information of its associated block to which the unit sections, where the subdivided information group is recorded, belong.
In another preferred embodiment, each said N-bit subdivided information group includes an error correction code and/or an error detection code.
In another preferred embodiment, the error correction code or the error detection code has its ability to correct an error of the address information weighted in such a manner that low-order bits of the error correction or detection code have a relatively large weight.
In another preferred embodiment, each said unit section has a first side displacement pattern that has been so defined as to make a signal waveform rise relatively steeply and fall relatively gently or a second side displacement pattern that has been so defined as to make a signal waveform rise relatively gently and fall relatively steeply.
An inventive address reading method is a method for reading subdivided information from an optical disk medium, which includes a tra
Furumiya Shigeru
Gushima Toyoji
Ishibashi Hiromichi
Ishida Takashi
Minamino Jun-ichi
Akin Gump Strauss Hauer & Feld L.L.P.
Tran Thang V.
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