HK1068449B - Data recording method and data recording device - Google Patents

Description

Data recording method and data recording device

Technical Field

The present invention relates to a data recording medium, a data recording method, and a data recording apparatus, which can be applied to an optical disk, such as a read only optical disk (ROM).

Background

The standard relating to Compact Discs (CD) has been widely used and is referred to as for compact discs for audio (CD-DA) and is according to the specifications in a standard specification called the red book. According to this specification, a variety of formats, such as CD-ROM, have been standardized, and so-called CD families have been proposed. In the following description, a CD generally refers to a disc of various formats included in the CD family.

A technique has been proposed in which a laser beam is irradiated onto a properly selected reflective film on a disc to vary the length of pits. Such a recording process is sometimes referred to as an additional recording process. When data is additionally recorded on the reflective film, identification information for identifying each disc, for example, may be recorded. When recording the identification information in the CD format, a subcode of the Q channel in the CD format may be used.

An error correction code called CIRC (cross interleaved reed-solomon code) is used in CDs. Therefore, when data such as disc identification information is recorded on the reflective film, the additionally recorded data is detected as an error and corrected with the CIRC. In this case, the original data at the time when the additional recording process has not been performed is read. If an error occurs that exceeds the error correction capability of the CIRC, the error cannot be corrected and thus the data cannot be read. In addition, the additionally recorded data cannot be read either, because an interpolation process is to be performed. Therefore, the proposed additional recording process has been performed so far only in the area where the error correction code encoding process is not performed. Thus limiting the scope of application of the additional recording process.

Disclosure of Invention

An object of the present invention is to provide a data recording medium, a data recording method, and a data recording apparatus, which are capable of extending the range of application of the additional recording process.

In order to solve the above problems, the present invention is a data recording medium having a reflective film, by recording data encoded with an error correction code to the reflective film, a part of the data in a recording area is rewritten so that the data is not detected as an error when the data is decoded.

A data recording method for recording data on a data recording medium having a reflective film, by recording data encoded with an error correction code to the reflective film, a part of the data in a recording area is rewritten so that the data is not detected as an error when the data is decoded.

A recording apparatus for recording data on a data recording medium having a reflective film, by recording data encoded with an error correction code to the reflective film, a part of the data in a recording area is rewritten so that the data is not detected as an error when the data is decoded.

According to the present invention, data is additionally recorded on the reflective film so that the data is not detected as an error when decoded. Therefore, when data encoded with an error correction code is decoded, the problem that the rewriting data cannot be read does not occur. According to the present invention, since data can be additionally recorded in an area that has been encoded with an error correction code, the application range of the additional recording process can be extended.

Drawings

Fig. 1 is a diagram illustrating a recording mode and structure of a conventional CD.

Fig. 2 is a schematic view illustrating a disc manufacturing process according to an embodiment of the present invention.

Fig. 3 is a diagram illustrating an additional recording process according to an embodiment of the present invention.

Fig. 4 is a diagram illustrating an optical disc recording format according to the present invention.

Fig. 5 is a diagram illustrating an optical disc recording format according to the present invention.

Fig. 6 is a block diagram showing an example of a CIRC encoder.

Fig. 7 is a more detailed block diagram showing an example of a CIRC encoder.

Fig. 8 is a block diagram showing an example of a CIRC decoder.

Fig. 9 is a more detailed block diagram showing an example of a CIRC decoder.

Fig. 10 is a diagram illustrating a CIRC interleaving process.

Fig. 11A to 11H are diagrams illustrating an additional recording process according to an embodiment of the present invention.

Fig. 12 is a diagram illustrating an additional recording process in the case of using CIRC.

Fig. 13 is a diagram illustrating an additional recording process in the case of using CIRC.

Fig. 14 is a diagram illustrating an additional recording process in the case of using CIRC.

Fig. 15 is a diagram illustrating an additional recording process in the case of using CIRC.

Detailed Description

Next, an embodiment of the present invention, which is applied to the case of recording disc identification information (hereinafter referred to as UDI) on a disc-shaped recording medium, will be described. The UDI is information for identifying each disc. The UDI describes, for example, the name of a disc manufacturer, the name of a disc vendor, the name of a manufacturing plant, the year of production, a serial number, time information, and the like. According to the present invention, the additionally recorded information is not limited to the UDI but is required information. The UDI is recorded in such a way that it can be read by a conventional CD player or a conventional CD-ROM drive. For ease of understanding, the structure of an optical disc, such as a CD, will first be described.

Fig. 1 is an enlarged view showing a portion of a conventional CD. On a track having a predetermined track pitch (e.g., 1.6 μm), depressed portions (called pits) and lands (non-depressed areas) are alternately formed. The pit and land lengths range from 3T to 11T, T representing the minimum switching interval. Laser light is irradiated from the reverse side of the CD.

The CD comprises a transparent disc-shaped substrate 1 having a thickness of 1.2mm, a reflective film 2 coated thereon, and a protective film 3 coated thereon. The reflective film 2 is made of a material having a high reflection coefficient. The CD is a read-only disc. However, as will be described later, after the reflective film 2 is coated, information (UDI) is recorded on the reflective film 2 by laser light.

Next, a flow of the CD production process will be described with reference to fig. 2. In step S1, a glass master is rotated by a spindle motor, which coats a photosensitive resist, a photosensitive material, on a glass substrate. A laser light turned on/off in accordance with a recording signal is irradiated onto the photosensitive resist film, and as a result, a master is produced. In order to develop the photoresist film, a developing process is performed. When the resist is of a positive type, the exposed portion is dissolved. An uneven pattern is formed on the photoresist film.

A master of photoresist is electroformed using an electroplating process, resulting in a metal master (at step S2). A plurality of pieces of master discs are produced (at step S3) using the metal master. A multi-piece stamper is again produced (at step S4) using the master disc. The disk substrate is produced using a stamper. The disc substrate is produced by a compression molding method, an injection molding method, a photo-curing method and the like. In step S6, a reflective film and a protective film are coated. In a conventional disc production method, a mark is printed on a CD.

In the example shown in fig. 2, laser light is irradiated to a reflective film (a mirror portion, e.g., a land). In addition, in step S7, information is additionally recorded. Laser light is irradiated onto the reflective film, and the land on the reflective film is heated (thermal recording). As a result, atoms are displaced, and the structure and crystalline state of the thin film are changed. Therefore, the reflectance at this portion decreases. As a result, after the laser light is irradiated to the land, the reflection of the laser light becomes small. Thus, the light detector recognizes the land as a pit. With this feature, the pit length can be varied to record information. In this case, the material for manufacturing the reflective film can have its reflection coefficient changed by laser irradiation. With a material, the additional recording process will increase its reflection coefficient.

In practice, the reflective film is made of an aluminum alloy Al_100-yX_yWherein X is at least one element selected from Ge, Ti, Ni, Si, Tb, Fe and Ag. The composition ratio y of the aluminum alloy film is selected in the range of 5 < y < 50 [ atom%]。

In addition, the reflecting film can also be made of a silver alloy film Ag_100-zY_zWherein Y is at least one element selected from Ge, Ti, Ni, Si, Tb, Fe and Al. The composition ratio z of the silver alloy film is selected to be [ atomic% ]in the range of 5 < z < 50]. The reflective film can be formed by, for example, magnetron sputtering.

For example, in the case of forming an AlGe alloy reflective film 50nm thick, laser light is irradiated from the transparent substrate surface or the protective film surface through an objective lens, and if the Ge composition ratio is 20[ atomic% ], and the recording power is in the range of 6 to 7[ mW ], the reflectance is lowered by about 6%. In such a case, if the Ge composition ratio is 27.6 atomic%, and the recording power is in the range of 5-8 mW, the reflection coefficient decreases by 7-8%. Since the reflection coefficient changes in such a manner, additional recording processing can be performed for the reflective film.

Fig. 3 is a schematic diagram actually illustrating a method for additionally recording a UDI. There are two modes, depending on the previous mode. These two modes are referred to as mode a and mode B.

First, mode a will be described. Three merge bits, e.g., (000), are inserted between the symbols. When the additional recording process is performed, one data symbol of 8 bits is, for example, (0x47), where 0x denotes a hexadecimal notation. Fig. 3 shows a pattern (00100100100100) of 14 bits of 00000000000000, 8 bits of data having been modulated in advance using the EFM (8-14 modulation) scheme.

A laser beam for performing an additional recording process is irradiated to a shadow area between two pits. As a result, the reflection coefficient of the shadow area is decreased. After the additional recording process is performed, two pits are linked and reproduced as one pit. In this case, the 14-bit mode becomes (00100100000000). This is because when this 14-bit mode is EFM decoded, it is decoded into 8 bits (0x 07).

In the case of mode B, the merge bit is (001). In this case, as in the case of the pattern a, when one laser beam is irradiated to the shadow area, 8 bits may be changed from (0x47) to (0x 07).

As described above, one data symbol (0x47) can be rewritten as (0x 07). There are many types of data that can be additionally recorded. One data symbol (0x40) can be changed to (0x 00). However, in the additional recording process, laser light is irradiated to a mirror portion where data has been recorded to change the length of the pit. Therefore, there is a limit to the types of data that can be additionally recorded.

Next, the error correction code encoding process used for the CD will be described. In CD, as an error correction code encoding system, the CIRC performs a double error correction code encoding process with a C1 code sequence (in the vertical direction) and a C2 code sequence (in the diagonal direction). The data encoded by the error correction code is subjected to EFM modulation in units of one frame.

Fig. 4 shows one frame of the CD data structure before EFM modulation of the data. If the audio data is sampled with 16 bits, as shown in fig. 14, one frame includes 24-symbol data bits, which correspond to six samples words (one symbol is 8 bits, so 16 bits are divided into two symbols) for each of the L (left) and R (right) channels, one Q parity composed of four symbols, one P parity composed of four symbols, and one sub-code composed of one symbol. One frame data recorded on the disc is converted from 8 bits to 14 bits according to EFM modulation. In addition, a DC component suppression bit is also added. In addition, a frame synchronization is added.

Accordingly, one frame recorded on the disc includes:

frame synchronization of 24 channel bits

Data bit 14.24 equals 336 channel bits

Subcode 14 channel bits

Parity check 14.8 ═ 112 channel bits

Merging bits 3.34 ═ 102 channel bits

Therefore, the total number of channel bits of one frame is 588 channel bits.

In the EFM modulation scheme, each symbol (8 data bits) is converted into 14 channel bits. The minimum time width Tmin of EFM modulation (time width of several 0 s between adjacent 1 s in one recording system) is 3T. The pit length corresponding to 3T was 0.87. mu.m. The pit length corresponding to T is the minimum pit length. In addition, 3 merge bits are placed between two blocks (each including 14 channel bits). In addition, a frame synchronization pattern is added at the beginning of the frame. If the duration of the channel bit is T, the frame synchronization pattern is a pattern of 11T, 11T and 2T in this order. Such a pattern does not occur in the rules of EFM modulation. Thus, a special mode can be used to detect frame synchronization. One frame includes a total of 588 channel bits. The frame frequency is 7.35 kHz.

Such a group of 98 frames is called a subcode frame (or a subcode block). The subcode frame corresponds to a reproduction time of 1/75 seconds for a conventional CD. Fig. 5 shows a sub-code frame in which 98 frames are arranged in order in the vertical direction. The sub-code in each frame is a symbol, each comprising one bit for each of the 8 lanes P-W. As shown in fig. 5, a sector includes a duration (98 frames) that completes a subcode. The sub-codes of the first two frames of the 98 frames are sub-code frame synchronization flags S0 and S1. When data of one disc is recorded on, for example, a CD-ROM disc, 98 frames (2352 bytes), one unit of which subcodes are completed, is one sector.

Fig. 6 and 7 are block diagrams showing a flow of encoding processing according to the CIRC system. The 24 symbols are supplied to the two-symbol delay/scramble circuit 11, in which one word of an audio signal is divided into high-order 8 bits and low-order 8 bits (W12n, A, W12n, B, …, W12n +11, A, W12n +11, B) (a denotes the high-order 8 bits and B denotes the low-order 8 bits). Each of the even digital data L6n, R6n, L6n +2, R6n +2, … is delayed by two symbols. Even if a sequence becomes erroneous in the C2 encoder 12, it can interpolate the sequence. The two-symbol delay/scramble circuit 11 can add scrambling to data so that the interpolation length of burst errors can be maximized.

The output of the two-symbol delay/scramble circuit 11 is supplied to the C2 encoder 12. The C2 encoder 12 performs an encoding process using a (28, 24, 5) reed-solomon code over GF (28) to generate a Q parity comprising four symbols Q12n, Q12n +1, Q12n +2 and Q12n + 3. The output of the C2 encoder 12, comprising 28 symbols, is provided to an interleaving circuit 13. If D represents a unit delay amount, the interleaving circuit 13 gives delay amounts which vary in an arithmetic progression, such as 0, D, 2D, …, so that the first sequence of symbols is converted into the second sequence. The interleaving circuit 13 disperses burst errors.

The output of the interleaving circuit 13 is supplied to the C1 encoder 14. The C1 encoder 14 uses the (32, 28, 5) reed-solomon code on GF (28) as the C1 code. The C1 encoder 14 generates a P parity that includes four symbols P12n, P12n +1, P12n +2, and P12n + 3. Each of the C1 codes and C2 codes, having a minimum distance of 5. Thus, a two-symbol error can be corrected. A four symbol error can be erasure corrected (in case the position of one erroneous symbol is known).

The output of the C1 encoder 14, comprising 32 symbols, is provided to a single-symbol delay circuit 15. The single symbol delay circuit 15 separates adjacent symbols to prevent errors at symbol boundaries from causing a two symbol error. An inverter inverts the Q parity. Therefore, even if the data and parity become all zero, an error can be detected.

The interleaving circuit 13 has a unit delay amount D of 4 frames. The adjacent symbols are separated by four frames. In the CIRC4 system, the maximum delay amount is 27D (═ 108 frames). The total interleaving length is 109 frames.

Fig. 8 and 9 are block diagrams showing a flow of the decoding process. The decoding process is performed in reverse order of the encoding process. The reproduced data output from the EFM demodulation circuit is supplied to the one-symbol delay circuit 21. The circuit 21 cancels the data delay generated by the single symbol delay circuit 15 on the encoding side.

The output of the single symbol delay circuit 21, comprising 32 symbols, is provided to a C1 decoder 22. The output of the C1 decoder 22 is provided to a de-interleaving circuit 23. The deinterleaving circuit 23 gives delay amounts which are varied in an arithmetic progression, for example 27D, 26D, …, D and 0 for 28 symbols, to cancel the delay generated by the interleaving circuit 13. The deinterleaving circuit 23 has a unit delay amount D of 4 frames.

As shown in fig. 10, the unit delay amount D is (D ═ 4). The total interleaving length is 109(═ 108+1) frames, which are slightly larger than one section. Many consecutive data become errors due to fingerprints sticking on the disc, scratches present, etc., and the total interleaving length defines the correction performance for such burst errors. Since the total correction length is large, the correction performance of the burst error is high.

The output of the deinterleaving circuit 23 is supplied to the C2 decoder 24. The C2 decoder 24 performs a C2 code decoding process. The output of the C2 decoder 24, comprising 24 symbols, is provided to a two-symbol delay/descramble circuit 25. The decoded data of 24 symbols is obtained from the two-symbol delay/descramble circuit 25. An interpolation flag generation circuit 26 generates an interpolation flag by using the error flags output from the C1 decoder 22 and the C2 decoder 24. The interpolation flag is used to interpolate the data indicating the error. Therefore, in the CIRC, error correction code encoding processing is performed with a C1 code sequence in the vertical direction and a C2 code sequence in the diagonal direction. In other words, the error correction code encoding process is performed doubly.

According to the present invention, in an area that has been encoded with an error correction code, a part of data is rewritten to record desired data, such as UDI. Fig. 11A to 11H show an example of a data rewriting method. However, for ease of understanding, the error correction code encoding process shown in fig. 11A to 11H is simpler than that in CIRC. In other words, for the data of four symbols (0x82, 0xef, 0x75, and 0x40) shown in fig. 11A, parities (0xba and 0xe2) of two symbols shown in fig. 11B are generated. This error correction code encoding process has the capability of correcting single symbol errors. The binary digits of the true parity check symbols represent only a code example. For example, they are parity symbols of a reed-solomon code, rather than values obtained by calculation of the error correction code encoding process.

These six symbols are EFM modulated. As shown in fig. 11C, each symbol containing 8 bits is converted into a 14-bit pattern. No merge bits are added. In fig. 11C, "1" represents the inversion of the height. A pit/land sequence as an uneven pattern on the disc as shown in fig. 11D. The duration of successive "1" s is the duration of the pits, and the duration of successive "0" s is the duration of the lands.

The additional recording process is performed next as described with reference to fig. 3. In fig. 11, two symbols are rewritten as indicated by the boxes. One symbol is originally (0x 40). After the additional recording process is performed on the pit/land sequence shown in fig. 11D, the pit length becomes longer as shown in fig. 11E. When the pit/land sequence shown in fig. 11E is reproduced after the additional recording process is performed, 14-bit data shown in fig. 11F is reproduced.

The 14-bit data is converted into 8 bits in the reproducing direction, and the entire read data shown in fig. 11G is obtained. Therefore, the original data (0x40) is rewritten to (0x 22). If only one of the six symbols of an error correction code sequence is changed, an error is detected and corrected when they are decoded. In other words, the original data (0x40) is reproduced. In this case, the rewritten data (0x22) cannot be reproduced.

Therefore, in the example shown in fig. 11, the parity symbol (0xe2) is changed to (0x01), so the additionally recorded data symbol (0x22) is not detected as an error at the time of data decoding. With the error correction code, when six symbols (0x82, 0xef, 0x75, 0x22, 0xba, and 0x01) including one data symbol that has been rewritten and one parity symbol (0x01) are reproduced and decoded, no error is detected. In other words, in the case where data (0x22) is included, (Oxba and 0x01) are obtained as parity symbols. Therefore, as shown in fig. 11H, one rewritten data symbol can be reproduced.

Next, the relationship between the additionally recorded data and the desired information, such as UD1, will be described. On the disc, an area in which data is additionally recorded is predefined in absolute address or the like. An example of such a region is shown in fig. 11. The data recorded in the area is defined as predetermined data. The additionally recorded data (0x22) in the above example is different from the known data (Ox 40). Therefore, when data is reproduced, it can be determined that it has been rewritten. The rewritten data (0x22) may be UDI data or a part thereof. In this case, since there is a limit to the types of data that can be additionally recorded, it is difficult to record many types of data.

Therefore, according to the present invention, it is represented by one bit of UDI according to whether known data is rewritten. If the data is rewritten, as in the example shown in fig. 11, it is determined to be "1". If the data is not rewritten, "0" is determined. If the area shown in fig. 11A to 11H is processed N times, N bits can be additionally recorded. Actually, the N areas are further repeated in order to increase the recording data.

Next, the case where the present invention is applied to CIRC will be described. In CIRC, four parity symbols are added. Therefore, if an error of more than five symbols occurs, it cannot be determined. With this phenomenon, five data symbols are rewritten, so that errors are not corrected. Thus, one data sequence that has been rewritten can be reproduced.

When decoding is performed using reed-solomon codes, a syndrome is calculated to determine whether there is an error. The number of syndromes is the same as the number of parity symbols. In CIRC, four syndromes are calculated. If all syndromes are 0, it is determined that there is no error. Logically, after one parity check of four symbols is added, if data of five data symbols is rewritten, all syndromes become 0. However, when calculating the syndrome value, any value cannot be replaced by any value. The numerical values that can be replaced by arbitrary numerical values are limited.

As described above, any data cannot be written to any data due to limitations in the additional recording of data. Therefore, replacement of the data sequence is decided in rewritable combinations, each of which is original data and rewritten data. In addition, the replacement of the data sequence is determined by considering adjacent data. Considering these two conditions, a data sequence capable of being rewritten is decided, and the syndrome of the rewritten data sequence becomes 0.

In the CIRC, as described above, two codes, i.e., the C1 code and the C2 code, are used as error correction codes. Each data symbol is double coded with both code sequences. Thus, by the second error correction code processing, one data sequence subjected to rewriting is restored to the original data sequence. As a result, the rewritten data cannot be read. Therefore, it is necessary to make these two code sequences not correct errors.

As described above, in the CIRC to which the parity of four symbols is added, the values of all syndromes become 0 when five symbols are rewritten. However, when five symbols are not fixed, it is necessary to add five symbols satisfying the second error correction code (code C1). The result is a divergence. If one of the five symbols is placed anywhere and the other four symbols are placed in the region where the parity is added, the divergence can be prevented.

Fig. 12 to 15 describe the positions of five data symbols to be rewritten in the CIRC. Fig. 12 shows positions of five data symbols to be rewritten among 24 symbols of input data as shaded areas. These five data symbols are contained in the same C2 code sequence. If the values of the five data symbols are properly selected, the values of all syndromes decoded with the C2 code become 0. Fig. 13 shows the positions of five data symbols at the output of the C2 encoder as shaded areas.

An interleaving circuit interleaves the output of the C2 encoder and inputs the result to the C1 encoder. Fig. 14 shows the positions of five data symbols at the output of the C1 encoder as shaded areas. The output of the C1 encoder is provided to the EFM modulator through a single symbol delay circuit. Fig. 15 shows the positions of five data symbols input to the EFM modulator as shaded areas. As shown in fig. 14 and 15, for each of the five data symbols to be rewritten, four C1 parity symbols are rewritten so that all syndrome values become 0 when they are decoded in the C1 code. Finally, 25 symbols are rewritten by an additional recording process.

While the invention has been shown and described with respect to the best mode embodiments thereof, it will be understood by those skilled in the art that the foregoing and various other changes, omissions and additions in the form and detail thereof may be made therein without departing from the spirit and scope of the invention. For example, the present invention is not limited to the additional recording process of the reflective film. In addition, the present invention can also be applied to an additional recording process of a phase change film, a magneto-optical recording film, or the like. Further, the present invention can also be applied to a write-many optical disk on which data in a CD-DA format and data in a CD-ROM format, for example, are recorded. As information recorded on the optical disk, there are various types of data such as audio data, video data, still image data, text data, computer graphics data, game software, and computer programs. In addition, the present invention can also be applied to, for example, DVD video and DVD-ROM.

As is apparent from the above description, according to the present invention, when additional recording processing is performed on a disc on which data has been recorded, information such as a disc identification can be recorded in an area that has been encrypted with an error correction code. Since the additional recording process can be performed using the error correction code, the application range of the additional recording process can be extended.

Claims (4)

1. A data recording method for recording data on a data recording medium having a reflective film, by recording data encoded with an error correction code to the reflective film, rewriting a part of the data in a recording area so that the data is not detected as an error when the data is decoded.

2. The data recording method according to claim 1,

the recording method is characterized in that the known data is recorded at a predetermined position of the recording area, part of the known data is rewritten, and the desired information is recorded based on whether or not the part of the known data has been rewritten.

3. A data recording apparatus for recording data on a data recording medium having a reflective film, by recording data encoded with an error correction code to the reflective film, a part of the data in a recording area is rewritten so that the data is not detected as an error when the data is decoded.

4. The data recording device according to claim 3,

the recording method is characterized in that the known data is recorded at a predetermined position of the recording area, part of the known data is rewritten, and the desired information is recorded based on whether or not the part of the known data has been rewritten.