JPH0954956A - Optical recording medium reproducing device and recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve recording density and to increase a processing speed by recording disk information to be recorded as an error correction code by a product code and constituting so that respective symbols incorporated in a one side code word are separated sufficiently. SOLUTION: A recording medium 1 is constituted so as to record/reproduce information through a thinner protective layer 4 not to record/reproduce through a substrate 2. Here, the protection layer 4 is defined 1.5 in a refractive index and 0.5mm in a thickness. A numerical aperture NA of an objective lens 11 is 0. 74. At this time, a period of an information track on a recording layer 3 is capable of making 1μm. Thus, the thickness of the transparent protection layer through which a light beam for recording/reproducing transmits is thinned, and thus, the objective lens with the large NA becomes usable, and the high recording density is realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing device and a recording device for an optical recording medium that optically records information, and particularly to improve the recording density thereof.

[0002]

2. Description of the Related Art In recent years, applications of optical recording / reproducing technology have been remarkably widespread, and especially audio and video discs exclusively for reproduction have been widely spread to households. These are recorded at extremely high density, and in order to secure reliability against defects and dust of various recording media, a protective layer with a thickness of about 1.2 mm and a strong error correction code are used.

An example of the above-mentioned conventional optical reproducing apparatus and recording apparatus will be described below with reference to the drawings. 3 and 4 show a schematic configuration diagram of a compact disc player and a conceptual diagram of a recording format as an example of a conventional optical reproducing apparatus. In FIG. 3, reference numeral 21 is a recording medium, 22 is a substrate thereof, 23 is a recording film formed of a reflective film having irregularities called pits, and 24 is a protective layer for protecting the recording film 23. Reference numeral 25 denotes a light beam for reading information, which is converged on the recording film 23 through the substrate 22. Reference numeral 30 is an optical head, 31 is an objective lens included in the optical head 30, and the objective lens 31 records the light beam 25 into a recording film.
Upon converging on 23 and receiving the reflected light, the optical head 30 converts the received detection light into an electric signal and outputs it.
A reproduction channel 32 performs analog signal processing such as amplification of an electric signal output from the optical head 30. Reference numeral 33 denotes a synchronization circuit which extracts a clock from an output signal from the reproduction channel 32 to generate a read clock, detects a synchronization signal, and also generates a timing signal necessary for the operation of each unit. A demodulation circuit 34 restores the channel code output from the reproduction channel 32 to the original data while referring to the read clock and timing signal output from the synchronization circuit 33. Reference numeral 35 is a data control circuit, 36 is a buffer memory, and 37 is an error correction circuit. The error correction circuit 37 reads the data stored in the buffer memory 36, corrects the error, and then again corrects the error in the buffer memory 36. The data control circuit 35 controls the flow of these data, stores the read data in the buffer memory 36, and outputs the data read from the buffer memory 36 to the outside.

The operation of the optical recording medium and the reproducing apparatus configured as described above will be described below. First,
The objective lens 31 focuses the light beam 25 on the recording film 23 through the substrate 22. At this time, the thickness of the substrate 22 is about 1.2 mm, and the numerical aperture NA of the objective lens 31 is set so that the aberration falls within the allowable range even if the substrate 22 is tilted to the extent normally considered.
Is limited to about 0.5 or less. As the light beam 25, light having a wavelength of about 780 nm emitted from a semiconductor laser is usually used. The light spot formed on the recording film 23 cannot be narrowed down below the diffraction limit determined by the numerical aperture and the wavelength, and this becomes a factor limiting the recording density. actually,
Under the above optical conditions, the track period is 1.3 μm.
If it is made small, crosstalk will increase.
It is set to about 5 μm or more.

On the recording film 23, there is recorded a channel code obtained by converting the data to be recorded into a modulation code suitable for high density recording. . The optical head 30 converges the light beam 25 on the recording film 23 to form a light spot, and scans the information track on which the channel code is recorded.
The optical head 30 receives the light reflected from the recording film 23, converts the light into an electric signal, and outputs the electric signal. The reproduction channel 32 performs impedance conversion and amplification of the signal output from the optical head 30, and then shapes the waveform to output a binary signal. The synchronizing circuit 33 locks the PLL at the edge of the binary signal output from the optical head 30 to generate a channel clock synchronized with the bit period of the channel code, and
The sync signal included in the binary signal is detected to generate various timing signals. The demodulation circuit 34 synchronizes the binary signal output from the reproduction channel 32 with the channel clock to reproduce the channel code, and refers to the timing signal output from the synchronization circuit 33 to group the channel code to generate the original signal. Inverse conversion to the data of. The read data reproduced by the demodulation circuit 34 is stored in the buffer memory 36 via the data control circuit 35.

FIG. 4 is a conceptual diagram showing a recording format. On the recording medium, Dn, 1, Dn + 1,2, Dn, 3, Dn + 1,
4 ... Dn + 1, 12, Qn, 1 ... Qn +
1, 4, Dn, 13, Dn + 1, 14, Dn, 15,
Dn + 1, 16 ... Dn + 1, 24, Pn, 1 ...
· Pn + 1,4, from left to right along the row direction of the figure, n
A data word is alternately recorded between a line and an (n + 1) th line after being converted into a channel code. Each data word is composed of one byte. Each byte represented by P and Q is a parity byte for error correction, and Q parity is generated so as to form a code word when each byte is collected every four rows in the diagonal direction of the figure, P-parity is generated such that one row in the figure is a code word. That is, Dn, 1, Dn + 4,2, ... Dn + 44,12
, Qn + 48, 1 ... Qn + 60, 4, Dn + 64,
13, Dn + 68,14 ... Dn + 108,24 becomes a code word, Qn + 48,1 ... Qn + 6
0,4 are generated, and Dn, 1, Dn, 2, ... Dn, 12, Qn, 1
..Qn, 4, Dn, 13, Dn, 14 ... Dn, 2
Pn, 1 ... Pn, 4 are generated so that 4, Pn, 1 ... Pn, 4 are code words. Thus, by forming a code word in two directions, it is configured as a kind of product code.

The data control circuit 35 of FIG. 3 reads the code word in the row direction of FIG. 4 from the buffer memory 36, performs error correction, returns the corrected code word to the buffer memory 36 again, and returns the code word in the row direction. The error correction circuit 37 is controlled so that the code word in the diagonal direction of the portion where the code word correction operation is completed is read from the buffer memory 36 to perform error correction, and the corrected code word is returned to the buffer memory 36 again. . Data control circuit
Further, 35 reads out the data in the buffer memory 36 for which all the correction operations have been completed in a predetermined order at a predetermined speed and outputs it. (For example, Ohmsha "Compact Disc Reader" pages 103-110)

[0008]

However, in the above configuration, the symbols forming the codeword in the row direction are recorded in close proximity to each other on the recording medium, and the parity in each direction is only 4 symbols. Since the substrate 22 is not added, if the substrate 22 is made thin, burst errors due to surface flaws and dust frequently occur, and the correction ability is improved even if iterative correction is performed alternately in two directions while using erasure correction. It was not sufficient, the error correction probability was not sufficiently small, and it was difficult to put it into practical use for external storage of a computer. Therefore, the thickness of the substrate needs to be 1 mm or more.
A lens with a diameter of about 2 mm is used.
A is limited to about 0.5 or less, and there is a problem that the improvement of recording density is hindered.

In view of the above-mentioned problems, the present invention can be put into practical use even if the thickness of the transparent layer through which the light beam for recording / reproducing is transmitted is reduced to about 1 mm or less. The present invention provides an optical recording medium and a recording / reproducing device capable of recording.

[0010]

In order to solve the above problems, the optical recording medium of the present invention records disk information to be recorded as an error correction code by a product code, and at least one code word is recorded. In order to prevent uncorrectable burst errors due to flaws and dust on the surface of the medium, the symbols included in them should be sufficiently separated from each other, and the number of parity symbols included in at least one codeword should be correct. The thickness of the protective layer through which the light beam for recording / reproducing passes is set to 1 mm or less and the period of the information track is set to 1.3 μm or less by adding the number necessary to sufficiently reduce the probability of . Further, the recording or reproducing apparatus of the present invention is for recording information on the optical recording medium or reproducing information from the storage medium, and focuses the light beam with an objective lens having a numerical aperture NA of 0.58 or more. It has a unique configuration.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Even when an objective lens having a large numerical aperture capable of recording or reproducing information at a high recording density is used, the present invention is equivalent to the conventional one because the transparent protective layer through which the light beam is transmitted is thin at 1 mm or less. Since the product code allows the inclination of the recording medium and is capable of iterative correction using erasure correction, it is possible to secure sufficient reliability against flaws and dust on the surface of the recording medium. .

This will be described in more detail below. Generally, the recording density when performing optical recording is limited by the size of a light spot converging on a recording film. If the light spot becomes smaller, both the track period and the bit period can be reduced in proportion. However, the bit period can transmit a larger amount of information in a certain band by devising a modulation code, waveform equalization, and the like, so that it cannot be said that the bit period is limited solely by the light spot. However, it can be said that the track period is almost limited by the size of the light spot because it is difficult to improve the track period by the crosstalk that occurs when the track period is reduced. The size of the light spot is inversely proportional to the numerical aperture of the objective lens. Therefore, by increasing the numerical aperture of the objective lens, the track period can be reduced, and the recording density can be improved. In the conventional example, the numerical aperture is 0.
For example, the track cycle is set to about 1.5 μm.

On the other hand, the numerical aperture of the objective lens cannot be increased without limit, and there is another factor that limits this.
That is the aberration that occurs when the recording medium is tilted. This aberration increases as the numerical aperture or the thickness of the transparent protective layer through which the light beam passes increases. The numerical aperture allowed for the same inclination angle is inversely proportional to the cubic root of the thickness of the transparent protective layer. Conventionally, the thickness of the transparent protective layer is set to about 1.2 mm in order to defocus surface flaws and dust and reduce the influence on the read signal. for that reason,
The practical limit of the numerical aperture is about 0.55. In order to increase the numerical aperture, it is necessary to reduce the thickness of the transparent protective layer. When the thickness becomes 1 mm or less, the influence of flaws and dust on the signal becomes noticeable. Therefore, instead of defocusing and optically mitigating the effects of flaws and dust, if the effects are dispersed and mitigated by signal processing, even a thin transparent protective layer of 1 mm or less can be put to practical use.

The upper limit of the size of surface flaws and dust that must be tolerated under a normal use environment is approximately 200 μm experimentally and empirically. Therefore, even if the thickness of the transparent protective layer is negligible, the recording format must be able to withstand a signal loss of 200 μm. Further, when the transparent protective layer becomes thicker and the diameter of the light beam on its surface exceeds 200 μm, the signal format must be able to withstand the loss of a signal of a length corresponding to the beam diameter. I won't. The refractive index of the transparent protective layer is n, and its thickness is t (m
m) and the numerical aperture of the objective lens is expressed as NA, the diameter D of the light beam on the surface of the transparent protective layer is D≈2 · NA · t / n (mm). Since the practical limit of the numerical aperture for the thickness of 1.2 mm of the transparent protective layer is 0.55, the limit NA of the numerical aperture for the transparent protective layer is NA≈0.55 · (1.2 / t) ¹ / 3≈0.58 / t ^1/3 Therefore, D≈1.2 · t ^2/3 / n. Since loss of a signal having such a length frequently occurs, the recording format must be able to withstand the loss. Then, this invention aims at solving the subject as follows. (1) Use product code to enable strong error correction by iterative correction. (2) At least one of the codewords secures an interleave length that does not result in an uncorrectable burst error even if a signal with the above-mentioned length is missing. (3) At least codewords in either direction should be at least as large as the number necessary to make the probability of miscorrecting an error that exceeds the capacity limit, even if the correction operation is performed up to the capacity limit. Parity of the number of symbols is added to enable erasure correction in the direction orthogonal to it.

The product code is a two-dimensional array of data,
Parity is added to each of the row and column directions,
Each direction is an independent code word. The repetitive correction refers to performing the correction operation in the row direction and the correction operation in the column direction alternately and repeatedly as long as the number of errors decreases. The repetitive correction of the product code can have extremely high correction capability, and is more effective if erasure correction is used together. Erasure correction is a correction method in which when a certain codeword is corrected, if an erroneous symbol is known in advance, the symbol is considered to be lost and the lost symbol is calculated from the remaining symbols. Yes, and when all non-disappearing symbols are correct,
Even if the same number of symbols as the number of parity symbols disappears, the symbols can be calculated. For example, when the parity is 16 symbols, a normal correction operation can only correct 8 symbols, but when only erasure correction is performed, the original codeword can be decoded even if 16 symbols are lost. To use this erasure correction for correcting the product code, for example, the following is performed. First, when the product codes arranged two-dimensionally are regarded as one unit block, 1
The data of the block is read and stored in the memory, and the correction operation in the row direction is performed for each row.

At this time, a flag is set for the uncorrectable code word in the row direction. When the number of flags set in the code word in the row direction is less than the number of parity in the column direction, it is considered that all of these code words have disappeared,
Complete error correction can be performed by performing erasure correction on a code word in the column direction. When there are too many flags, normal error correction is performed instead of erasure correction. At this time, if at least one codeword in the column direction has been corrected and not all have been corrected, the above-described correction operation in the row direction may be repeated once. When performing such erasure correction, the reliability of the flag is important. For example, in the correction operation in the row direction, the flag is not set when the originally uncorrectable error is erroneously corrected, and if the erasure is corrected to the full capacity in the column direction, this erroneous correction is overlooked and the error is corrected. Even though it includes it, it is regarded as correct and the correction operation is completed. In order to solve such a problem of erasure correction, it is necessary to sufficiently reduce the probability of erroneous correction in the correction operation in the row direction.

The number of parity symbols required to sufficiently reduce the error correction probability will be described below. Now, it is assumed that each symbol consists of n bits, that is, the codeword is generated on the Galois field GF (2 ⁿ ). If the number of symbols for parity is d, the number of symbols that can be corrected is [d / 2] symbols (where [] is a Gaussian symbol). When the number of erroneous symbols becomes [d / 2] +1, there is a possibility of erroneous correction.

The probability is (2 ⁿ -1) ^{[(d-1) / 2] +1} . In general, it is said that the allowable frequency of occurrence of errors in a data storage device is once per 10 ¹² bits. Therefore, if the number of symbols of information included in this codeword is m, d is set so as to satisfy (2 ⁿ −1) ^{[(d−1) / 2] +1} ≧ 10 ¹² / (n · m) If decided, erasure correction with sufficiently high reliability can be performed. Symbol bit number n is 8
If the number of information symbols m is 30 or more, d may be 7 or more.

Next, the interleave will be described.
The interleaving means that the symbols in one codeword are not continuously recorded on a recording medium, but are rearranged and recorded so as to be recorded at fixed intervals. By doing so, even if there is a burst error due to a relatively long loss in the read signal, it is possible to prevent a number of errors from occurring in one codeword due to the burst error due to the loss. For burst errors that occur relatively frequently, it is ideal that at most one error occurs in one codeword, but the number of error symbols caused by one burst error is If the number of correctable symbols is less than half, even if there is another burst error in the block, there is enough capacity to correct it, and it can be said that interleaving is sufficiently effective. If the number of parity symbols included in the codeword is d, the number of symbol errors that can be corrected is [d / 2]. Therefore, the mutual distance between the symbols included in the codeword is the burst error of the read signal. It may be greater than or equal to the value obtained by dividing the length by [d / 2] / 2. The length of the burst error of the read signal that frequently occurs is 200 μm, 2 · NA · t /
Since n or 1.2 · t ^2/3 / n, the mutual distance of each symbol is 400 / [d / 2] 4 · NA · t / (n · [d / 2]) 2.4 · t ² Interleaving may be performed so as to be larger than any of ^{/ 3} / (n · [d / 2]).

Even if the thickness of the transparent protective layer is reduced to about 1 mm or less by using all of the means explained above,
Practically sufficient reliability can be secured and the recording density can be improved. An optical recording medium and a recording / reproducing apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic block diagram of an optical recording medium and a recording / reproducing apparatus according to an embodiment of the present invention. In FIG. 1, 1 is a recording medium, 2 is a substrate thereof, 3 is a recording film for recording information, and 4 is a protective layer for protecting the recording film 3. Reference numeral 5 denotes a light beam for reading information, which is converged on the recording film 3 through the protective layer 4. 10 is an optical head, 11 is an objective lens included in the optical head 10, 12 is a recording / reproducing channel, 13 is a synchronizing circuit, 14 is a demodulating circuit, and 15
Is a data control circuit, 16 is a buffer memory, and 17 is an error correction circuit. These all have basically the same functions as the conventional example of FIG.

The operation of the optical recording medium and the recording / reproducing apparatus configured as described above will be described below with reference to FIGS. 1 and 2. First, the recording medium 1 differs from the conventional example in that information is not recorded and reproduced through the substrate 2 but recorded and reproduced through a thinner protective layer 4. Here, the protective layer 4 has a refractive index of 1.5 and a thickness of 0.5 mm. The numerical aperture NA of the objective lens 11 is 0.7
4. At this time, the period of the information track on the recording film 3 can be set to 1 μm. When reading information from this recording medium 1, the optical head 10 and recording / reproducing channel
The operations of 12, the synchronization circuit 13, and the demodulation circuit 14 are the same as those of the conventional example, and thus detailed description thereof will be omitted.

FIG. 2 is a conceptual diagram showing a recording format in this embodiment. In the figure, Di, j represents a data symbol, and the symbol consists of 8 bits. 129 symbols of data are arranged in the row direction, and these data Di, 0 to Di, 128 are arranged. 16 symbols of parity Pi, 0 to P
i and 15 are added to form a Reed-Solomon code. Further, data of 129 symbols is arranged in the column direction, and these D0, j to D128, j Or P0, k to P128, k Also, 16 symbols of parity Q0, j to Q15, j are added to form a Reed-Solomon code. The entire product code is recorded as one block at a predetermined position on the recording medium with an address assigned to each block. At this time, the arrangement is recorded on the recording medium in the order in which the arrangement is scanned in an oblique direction. That is, each symbol is recorded on the recording medium as D _0,0 · D _1,1 …… D ₁₂₈ , ₁₂₈・ Q _0,129・ ・ ・ Q _15,144・
D _1,0・ D _2,1 ………… D _128,127・ Q _0,128 …… Q
_15,143・ P _0,15・ D _2,0・ D _3,1 …… D _128,126・ Q
_0,127 are arranged as shown in _{...... Q 15,142 · P 0,14 · P} 1,15 · D 3,0 ....... This block is further divided into a plurality of sectors every four rows. The 0th to 3rd rows are divided into the first sector, the 4th to 7th rows are divided into the 2nd sector, and the 124th to 127th rows are the 32nd sector.
On line 128, the attribute of this block and each sector in this block can be recorded. In addition, each sector has a capacity of 516 bytes, and 51
A 4-byte CRC code can be included in addition to the 2-byte user data.

The operation of reading the data recorded in such a format will be further described. When the address of the sector to read the information is designated from the external device such as the host computer, the data control circuit 15
Calculates the address of the block including the sector and the number of the sector in the block. When the address of the block is known, this is instructed to the access means, not shown in the figure, and the optical head 10 is positioned at a predetermined position. When a predetermined block address is found from the read signal, the data control circuit 15 stores the data read from the block in the buffer memory 16. When reading is completed, the data control circuit 15 controls the error correction circuit 17 to perform an error correction operation in the column direction. Since each codeword includes 16 symbols of parity, even 8-fold error correction is possible. Flags are set for codewords that cannot be corrected. When the correction operation in the column direction is completed, the error correction circuit 17 is controlled so as to perform the correction operation in the row direction next. The number of flags set by the correction operation in the column direction is 16
In the following cases, it is assumed that all the code words in the column direction in which the flags are set have disappeared, and all errors can be corrected by performing erasure correction in the row direction.
When the number of the flags exceeds 16, the correction operation is performed up to the 8-fold error in the row direction. Also at this time, if the code cannot be corrected, the flag is set to the code word. After one round of the row-direction correction operation is completed, a correction operation similar to the row-direction correction operation is performed again in the column direction. In this way, the correction operation in the column direction and the row direction is alternately repeated. When all the erroneous symbols are corrected, or when the number of erroneous symbols does not decrease at all, the correction operation ends. When all the errors of the predetermined sector are corrected, the data control circuit 15 reads the data of the sector from the buffer memory 16 and outputs it to the outside. When an error remains in a predetermined sector, a read error signal is output to the outside.

On the other hand, when rewriting the data of a predetermined sector, first, as in the case of reading, the data of the block including the predetermined sector is read out and buffered.
The data is stored in the memory 16 and the correction operation is performed. If the correction has failed, a write error signal is output. When the correction operation is completed normally, the data in the predetermined sector is rewritten, and only the parity in the row direction of the rewritten row is calculated and rewritten. Since the buffer memory 16 has a capacity capable of accumulating data of a plurality of blocks, it is not necessary to rewrite the block of the recording medium immediately after rewriting the data on the buffer memory 16, and the buffer memory 16 can be stored at an appropriate time. The contents of the memory 16 may be moved to the recording medium. Therefore, the parity in the column direction may be calculated and rewritten after the information in the sector of the buffer memory 16 is finally rewritten until the data in the rewritten block is transferred to the recording medium.

As described above, according to the present embodiment, the error correction code is a product code, the number of parity symbols is sufficiently large so that repeated erasure correction can be performed using highly reliable erasure correction, and the interleave length is increased. By making it sufficiently large, it is possible to reduce the thickness of the transparent protective layer through which the light beam for recording / reproducing is transmitted, which makes it possible to use an objective lens with a large numerical aperture NA and achieve high recording density. can do. Moreover, such a product code has a large block size, and recording / reproduction on / from a recording medium needs to be performed in this block unit. However, this block is divided into a plurality of sectors, and rewriting is performed in the sector unit on the buffer memory. By configuring it to
The recording medium can be used efficiently without spending the entire large block for a small amount of data.

In the above embodiment, the recording format as shown in FIG. 2 has been described, but the present invention is not limited to such a specific format. For example, a code word in the row direction is changed to a code word in the column direction. It is also possible to make it shorter by about half and to arrange two code words in the row direction. In this case, the same operation as in the above embodiment may be performed.

Further, in the present embodiment, the thin protective layer 4 is provided on the opposite side of the substrate 2 with the recording film 3 interposed therebetween, and information is recorded / reproduced through the thin protective layer 4, but the same as in the conventional example. It does not matter if the substrate 22 is made thin so as to have a structure.

[0029]

As described above, the present invention is not a product code in which information to be recorded is substantially two-dimensionally arranged and a parity is added in each of the column direction and the row direction to form a code word. One codeword is interleaved so that even if there is a defect of about 200 μm, only a double error occurs at most,
Furthermore, by limiting the number of parity symbols so that the error correction probability of the code word in either direction is sufficiently small, the thickness of the protective layer of the optical recording medium through which the light flux for recording / reproducing information is transmitted is 1 mm or less. And the numerical aperture of the objective lens is increased to 0.58 or more to set the track period to 1.
By reducing the thickness to 3 μm or less, it is possible to perform high-density recording while maintaining the same crosstalk characteristics as the conventional one.

Further, the codewords in any direction constituting the product code are interleaved so that even if there is a defect of about 200 μm, an error of less than half of the correction capability is generated at most, or the codewords in any direction are interleaved. In both cases, by limiting the number of parity symbols so that the error correction probability becomes sufficiently small, it is possible to obtain an effect of further strengthening the flaws and dust on the surface of the recording medium.

Further, if interleaving is long in the row direction and the column direction, the size of the block becomes large. However, by dividing this block into a plurality of sectors and enabling rewriting in units of this sector, the recording medium is made efficient. Can be used well. In addition, by dividing the sector along the row or column direction,
Immediately after data in a sector is rewritten, only the parity related to that sector is calculated and rewritten. Parity over multiple sectors is rewritten until the data is rewritten until it is transferred to the recording medium. The effect that the processing speed can be increased is obtained by performing the processing only once during the period.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a recording / reproducing apparatus in an embodiment of the present invention.

FIG. 2 is a conceptual diagram of a recording format in this embodiment.

FIG. 3 is a schematic configuration diagram of a conventional optical reproducing device.

FIG. 4 is a conceptual diagram of a recording format in a conventional example.

[Explanation of symbols]

 1 Recording Medium 4 Protective Layer 10 Optical Head 11 Objective Lens 15 Data Control Circuit 16 Buffer Memory 17 Error Correction Circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G11B 20/18 540 9558-5D G11B 20/18 540A 572 9558-5D 572C

Claims (2)

[Claims] 1. Information is arranged two-dimensionally in a predetermined order and each row is arranged.
And a parity is added to each column to form a codeword.
Digit coded with error correction code as product code by and
A playback device that optically plays back
The refractive index of the transparent protective layer of the optical recording medium is n, and its thickness is t
(Mm), either in the row or column direction
For each symbol included in one of the codewords, the number of parity symbols included in this codeword is d.
When at least each other,  2.4t^2/3/ (N · [d / 2]) mm or 400 / [d / 2] μm (where [] is Gauss symbol), whichever is greater
Place them along the information track for more than the distance of
The codeword in either direction is Galois field GF (2
^k) The number of symbols of the information generated and contained in
When m, the number of symbols of parity included in this is d
Is (2^k-1 )^{[(d-1) / 2] +1}≧ 10¹²/ (K · m) so that they are separated along the information track.
An optical recording medium characterized by reproducing each placed symbol
Body regeneration device. 2. Information is arranged two-dimensionally in a predetermined order, and each row is arranged.
And a parity is added to each column to form a codeword.
Digit coded with error correction code as product code by and
A recording device for optically recording information
The refractive index of the transparent protective layer of the optical recording medium is n, and its thickness is t
(Mm), either in the row or column direction
For each symbol included in one of the codewords, the number of parity symbols included in this codeword is d.
When at least each other,  2.4t^2/3/ (N · [d / 2]) mm or 400 / [d / 2] μm (where [] is Gauss symbol), whichever is greater
Place them along the information track for more than the distance of
The codeword in either direction is Galois field GF (2
^k) The number of symbols of the information generated and contained in
When m, the number of symbols of parity included in this is d
Is (2^k-1 )^{[(d-1) / 2] +1}≧ 10¹²/ (K · m) so that they are separated along the information track.
Optical recording medium characterized by recording each placed symbol
Body recorder.