Optical disc format exhibiting robust error correction coding

Details Optical disc format exhibiting robust error correction coding Optical disc format exhibiting robust error correction coding

2001-11-19

2003-05-20

Decady, Albert (Department: 2133)

Error detection/correction and fault detection/recovery

Pulse or data error handling

Digital data error correction

C714S755000

Reexamination Certificate

active

06567951

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an optical disc recording/reproducing method, an optical disc and to an optical disc device.
2. Description of the Related Art
Up to now, an optical recording medium, such as a disc-shaped recording medium or a card-shaped recording medium, employing an optical or magneto-optical signal recording/reproducing method, has been developed and offered to the market. Of these recording mediums, there are known read-only type recording mediums, such as the so-called compact discs, write-once type recording mediums on which the user can write only once, and an overwrite type recording mediums, on which the information can be rewritten, such as a magneto-optical disc.
An optical disc device for data writing/readout for a disc-shaped recording medium encloses a laser diode for radiating a light beam for information recording/reproduction and a photodetector for detecting the reflected light of the light beam illuminated on the optical disc and is adapted for recording/reproducing data by scanning the recording track of the optical disc with a light beam using an optical head focussing-servo or tracking-servo controlled, based on a detection output of the photodetector, as the speed servo is applied to the spindle motor to run the optical disc run in rotation at a constant angular velocity or at a constant linear velocity. It is noted that blocked codes are used in a magneto-optical disc system prescribed in International Organization for Standardization (ISO).
In the magneto-optical disc format, prescribed in ISO, the direction of user data is the data direction on a disc, as shown in FIG.
1
. In an ECC block, employing the blocked code, the direction of the correction code is interleaved with reference to the data direction on the disc for elevating the burst error correction capability. In this format, data directly following the frame sync FS belongs to the same error correction code, the second data from the frame sync FS belongs to the separate same error correction code, and so forth until the data directly previous to the frame sync FS belongs to the still separate same error correction code.
If, during recording on this format of the optical disc, the totality of a sole ECC block of user data sent from the application side is written via an arbiter
301
on a buffer memory
302
, an ECC processor
303
starts error correction coding. When the totality of data in the sole ECC block has been encoded, the encoded data is sent from the buffer memory
302
to modulation means to start channel encoding. It is this channel-encoded data that is recorded on the user data area on the disc.
Also, if during reproduction, the reproduced data obtained from the disc is channel-decoded by demodulation means so that the totality of a sole ECC block is written in the buffer memory
302
via arbiter
301
, as shown in
FIG. 2B
, the ECC processor
303
starts decoding. When the totality of data within the sole ECC block has been decoded, user data is retrieved from the buffer memory
302
and sent to the application side.
Recently, the recording capacity of a read-only memory (ROM) disc or a random-access memory (RAM) by an optical recording medium is increasing drastically. As the wavelength of a semiconductor laser used for an optical head of an optical disc recording/reproducing apparatus is becoming shorter, attempts are made towards increasing the numerical aperture NA of an objective lens used for converging the light beam on an information recording surface of the optical disc.
As a technique for realizing a high density phase change type optical disc of a larger recording capacity exceeding the capacity of the DVD-RAM, there is known a method of reducing the spot size. The spot size on a recording medium, generally given by &lgr;/NA, can be reduced by the technique of using a short wavelength semiconductor laser light source, such as GaN or ZnSe, or the technique of enlarging the NA of an objective lens by a double lens set exemplified by a solid immersion lens (SIL).
If, for example, a=640 nm and NA is 0.85, the spot diameter is approximately 0.75 &mgr;m on the recording medium, such that, if signals are recorded or reproduced using, for example, the RLL(1,7) modulation, the recording line density of the order of 0.21 &mgr;m/bit can be achieved.
As the representative modulation code of the modulation system of the broad channel detection window suited for high density recording/reproduction, there are known the RLL(1,7) code or the RLL(2,7) code.
In an optical disc system employing an optical head having an objective lens of high NA, it is necessary to elevate the error correction capability in order to combat errors ascribable to the dust and dirt affixed to or scratches on the optical disc surface. For elevating the error correction capability, the code or the ECC block is enlarged.
There is also proposed a method of bundling and blocking error correction codes by interleaving for enlarging the ECC block to a length equivalent to one track on the inner rim of the disc.
If the blocked code is used, the block size exceeding 64 kB as user data can be constructed even with the use of the GF(2
8
) routinely used as a code.
In the block structure known up to now, as shown in
FIG. 3
, the number of symbols of the C1 correction code and the C2 correction code is up to a maximum of 255 in the case of the product code (PRC) employing the GF(2
8
). The interleaving length is up to a maximum of 255+1 such that it cannot be extended limitlessly. Although the code length can be lengthened by limiting C1 only to the code for detection, C2 needs to be a correction code in order to effect error correction. Therefore, none of the C2 code, C1 code nor the interleaving length can be lengthened with a routine method.
On the other hand, if, with the ECC block structure of the DVD shown in
FIG. 4
, a large block is constituted, it is difficult to have the information word and the parity word distributed evenly in each sector, while it is difficult to have the sector ID in the information word arranged in each sector, to render the addressing in the ROM disc difficult.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an optical disc recording/reproducing method, an optical disc and an optical disc device in which a logical format of a product code is constructed for enabling the long interleaving by a large block to enable data recording/reproduction to high reliability.
It is another object of the present invention to provide an optical disc recording/reproducing method, an optical disc and an optical disc device in which recording/reproduction of data of sufficiently high reliability for normal use is enabled at a high transfer rate.
It is another object of the present invention to provide an optical disc recording/reproducing method, an optical disc and an optical disc device in which data can be recorded/reproduced with plural logical formats having the same physical format and different block sizes.
According to the present invention, the error correction code C1 takes a line in the vertical direction, against the oblique data direction on the disc, as indicated by the data direction on the disc and the code direction (correction line) in
FIG. 39
, and the error correction code C1 is interleaved. A number of the interleaved error correction codes C1 are bundled to form an ECC block, on which a second code C2 having the data direction different from the error correction code C1 is constituted, as shown in FIG.
40
.
In this ECC block, the data on the disc is in the oblique direction, while the interleaving direction with respect to the first error correction code C1 is in the horizontal direction, so that the interleaving length can be increased. Also, in this ECC block, a product code (PCR) can be constructed by having the second code C2 as the error correction code, thus assuring a high correction capability. Also, since the second code C2 in this ECC block has its direct

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