JP3991369B2 - optical disk - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical disc for recording and reproducing digital signals.
[0002]
[Prior art]
In recent years, optical disk devices have been attracting attention as means for recording and reproducing large volumes of data, and technological development is actively being carried out. In particular, high recording density, high transfer rate, high reliability, and the like are important issues. Various optical discs have been put into practical use and are spreading in the computer field or the fields of video and sound, but are expected to become more widespread in the future.
[0003]
Incidentally, FIG. 4 is a diagram showing a frame format of a CD (compact disc) commercialized as a music optical disc. It consists of 588 channel bits per frame, 24 bits of sync pattern at the head and 1 byte of sub-coding data (1 byte data is EFM modulated when actually recorded on the disk to become 14 channel bits) and data 12 bytes and 4 parity bytes are repeated twice. Between the synchronization pattern, sub-coding data, data, and parity, there are 3 channel combination bits. For the combined bits, a pattern that makes the number of bits 0 and 1 approximately equal is selected and recorded. This frame format is recorded continuously to form the entire disc.
[0004]
[Problems to be solved by the invention]
As described above, in the conventional optical disc format, 14 channel bits subjected to EFM modulation can be uniquely converted into 1 byte of user data. In addition, in a ROM type optical disk such as a CD, there is no deterioration of the recording surface due to repeated recording unique to the rewritable optical disk.
[0005]
However, when data is repeatedly recorded in the same recording sector with a rewritable optical disk, there is a possibility that a thermal load is applied due to the irradiation of the light spot on the recording surface and the recording surface is deteriorated. Especially in each recording sector, the boundary between the recording area and the non-recording area is likely to be subject to heat load, and the boundary portion may deteriorate due to repeated recording, making it impossible to read data correctly. is there. Therefore, there is a problem that it is not preferable to record necessary data in the vicinity of the boundary in an optical disc in which the recording surface may be deteriorated by repeated recording. That is, there is a problem that the worst data cannot be reproduced if recording is repeated at the beginning and end of the data recording area.
[0006]
Also, in the modulation code adopted by the rewritable optical disc, if there is no data of a specific pattern at the end of the data recording area where the data is recorded after the code conversion, the conversion is successful at the last part of the data. There was a problem that a case where it was not possible to appear.
[0007]
In addition, there is a problem that the recording data in the data recording area must be as short as possible except for the necessary data so that the recording capacity usable by the user can be increased as much as possible, and the reliability must be ensured.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide an optical disk format having a larger capacity and higher reliability.
[0009]
To achieve the above object, the optical disk of the present invention is provided a data recording area in each sector obtained by dividing a track into a plurality, and data of a specific pattern at the end of the data recording area (P1, P2, P3, P4 ) A dummy data is recorded as a guard data recording area, and at least data in the data recording area other than the guard data recording area is converted by selecting one from a plurality of tables based on the state (St) The pattern data is data including information for identifying a state (St + 1) determined from data in the data recording area immediately before the data of the specific pattern.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, first and second embodiments of the present invention will be described with reference to the drawings.
[0014]
FIG. 1A shows a schematic diagram of an optical disc according to an embodiment of the present invention. In FIG. 1A, 1a is an optical disk, 1b is a track existing on the optical disk 1a, and 1c is a sector. An optical disc has sectors arranged continuously along a track with a sector as a unit according to a predetermined physical format. FIGS. 1B, 1C, 1D and 1E are diagrams showing signal formats of the sectors of the optical disc in the embodiment of the present invention. A header area 2 is provided at the head of the sector 1c, and a signal for reading address information is recorded in advance. The header area 2 is followed by a gap area 3, a data recording area 4, and a buffer area 5 in this order. Data is not recorded in the gap region 3 and is used, for example, for power control of a semiconductor laser used for data recording / reproduction. The data recording area 4 is an area for actually recording user data. Digital data obtained by adding redundant data such as an error correction code to user data uses a run length restriction code in which zero runs are restricted between 2 and 10. Modulated and recorded in mark length. This run length limiting code is called a (2,10) modulation code. The buffer area 5 is provided to absorb rotational fluctuations of the optical disk, and no signal is recorded.
[0015]
There is a VFO area 6 at the top of the data recording area 4 and a guard data recording area 8 at the end of the data recording area. Further, the area between the VFO area 6 and the guard data recording area 8 is an area 7 for actually recording user data. The VFO area 6 exists in order for the optical disk apparatus to perform clock reproduction from a reproduction signal during reproduction.
[0016]
The guard data recording area 8 is provided in order to suppress the influence of deterioration of the recording surface caused by repeatedly recording data in the same recording sector.
[0017]
As a cause of deterioration of the recording surface due to repeated recording of data in the same recording sector, there is a thermal load due to irradiation of a light spot on the recording surface. Especially in each recording sector, the boundary between the recording area and the non-recording area is likely to be subject to heat load, and the boundary portion may deteriorate due to repeated recording, making it impossible to read data correctly. is there. Therefore, it is not preferable to record necessary data in the vicinity of this boundary when using an optical disc in which the recording surface may be deteriorated by repeated recording. Therefore, the guard data recording area 8 is provided to solve the above-described problem. As data to be recorded in the guard data recording area 8, the top data of the guard data recording area 8 is data of the specific pattern 8a, and the data other than the top data is the case of the arbitrary data 8b and the repetition of the data of the specific pattern 8a. There are cases.
[0018]
As an example of the arbitrary data 8b, a pattern as shown in FIG. 6 can be considered. This pattern is a pattern that satisfies the rules of (2, 10) modulation, and is a repetition of a pattern in which a mark is short, a space is long, and a byte is complete. Since the data is converted into 16-bit data, the 16-bit data pattern is repeated in FIG. 6). The reason why the mark is shortened and the space is increased is that when the data is actually written, the mark portion generates a higher power semiconductor laser output than the space portion, so that the degradation of the recording surface due to repeated recording can be minimized. Because.
[0019]
In the case where the specific pattern 8a is repeated, the recording of the guard data recording area 8 can be simplified simply by having a signal generator for repeatedly generating the specific pattern 8a in the optical disc apparatus. In addition, even when there is an error at the beginning of the specific pattern 8a during reproduction, the accuracy of detection of the specific pattern 8a is improved by reproducing the second, third,... Specific pattern 8a. Can do.
[0020]
The reason why the top data of the guard data recording area 8 is the specific pattern data 8a is as follows.
[0021]
FIGS. 2A, 2B, and 2C are schematic diagrams for explaining a modulation method and a demodulation method of a state modulation code used in the user data recording area 7 of the present embodiment. The state modulation code is a modulation code for converting 8-bit binary data into a 16-bit code sequence. A 16-bit output code sequence Yt for 8-bit input data Dt at a certain time t is determined based on the state St at that time t. That is, as shown in FIG. 2A, a conversion table having data Dt and a state St at time t as inputs and a code sequence Yt and a state (hereinafter referred to as the next state) St + 1 at the next time t + 1 as outputs. 21 and D flip-flop 22 are used for modulation.
[0022]
FIG. 2B shows a part of the contents of the conversion table 21. There are a total of four states St from 1 to 4 at each time, and a different code sequence Yt is assigned to each state. The next state St + 1 is determined by the state St and the data Dt at each time. All 16-bit sequences assigned to the table as the output code sequence Yt are limited to a zero run between 2 and 10, and even when a sequence between two times is connected, the zero run is limited between 2 and 10. The next state St + 1 is determined as follows.
[0023]
Further, there are cases where the same output series Yt is assigned at two locations to different input data dt, such as the underlined patterns p1b and p2b in the table. In such a case, the next states of both are always 2 and 3 (in this example, p1b is the next state 2 and p2b is the next state 3). Except for such a case, the output series Yt is never assigned redundantly at two locations.
[0024]
Further, the code sequences Yt belonging to the state 2 and the state 3 have the following properties. The output sequence Yt belonging to state 2 has both the first and twelfth bits from the left end being "0", and the output sequence Yt belonging to state 3 has one of the first and twelfth bits from the left end being "1". It is.
[0025]
In the demodulation of the state modulation code, it is necessary to convert a 16-bit code sequence into 8-bit binary data, contrary to the modulation. FIG. 2C is a block diagram illustrating the configuration of the demodulation circuit. A total of 18 bits of the 16-bit code sequence Yt at a certain time t, the first bit Yt + 1_1 of the code sequence Yt + 1 at the subsequent time t + 1, and the 12th bit Yt + 1_12 are input to the inverse conversion table 23. The The output of the inverse conversion table 23 at each time t is 8-bit binary data Dt.
[0026]
The configuration of the reverse conversion table 23 is basically the reverse view of the conversion table 23 shown in FIG. The binary data Dt that is the demodulation result is uniquely determined for a pattern that is not assigned redundantly in the code sequence Yt.
[0027]
On the other hand, the binary data Dt is not uniquely determined only by the code sequence Yt with respect to the patterns assigned overlappingly as in p1 and p2 in FIG. However, as described above, such duplication appears only when the next states of the two are 2 and 3, so that it can be uniquely determined by using the properties of the code sequences of the states 2 and 3. Is possible. That is, the binary data Dt is uniquely determined by looking at the first bit and the twelfth bit of the code sequence at time t + 1, which is the code sequence determined by the next state at time t during modulation.
[0028]
The data in the user data recording area 7 is code-converted using the modulation method as described above. The pattern of the head data of the guard data recording area 8 at the end of the data recording area 4 is determined based on the modulation result of the data recording area.
[0029]
For the above reasons, it is important that the head data of the guard data recording area 8 is data of a specific pattern.
[0030]
FIG. 3 shows an example of the specific pattern data 8a. In FIG. 3, the next state is the next state when the immediately preceding data is modulated. That is, if the next state when the last data of the user data recording area 7 is modulated is 1 or 2, and the last bit at the end of the user data recording area 7 is a mark, the pattern p1 is selected and the next state is 1 or 2. 2 and when the last bit at the end of the user data recording area 7 is a space, the pattern p2 is selected. When the next state is 3 or 4 and the last bit at the end of the user data recording area 7 is a mark, the pattern p3 is selected. If the next state is 3 or 4 and the last bit at the end of the user data recording area 7 is a space, the pattern p4 is selected and each mark length is recorded.
[0031]
The first and twelfth bits of the patterns p1 and p2 are both “0”. On the other hand, the first bit of the patterns p3 and p4 is “1”.
[0032]
By using such a pattern as the specific pattern data 8a, the final data pattern in the user data recording area 7 can be demodulated uniquely.
[0033]
Further, as a further feature, the patterns p1 and p2 are all "0" in the second bit, the eleventh bit, and the thirteenth bit, which are adjacent bits to the bits (first bit and twelfth bit) for identifying the state. Yes. As a result, it is possible to prevent the 12th bit from being recognized as “1” and demodulating the state by mistake due to bit shift or the like.
[0034]
A third embodiment of the present invention will be described with reference to FIGS.
As shown in the first embodiment, the guard data recording area 8 is provided in order to suppress the influence of deterioration of the recording surface caused by repeatedly recording data in the same sector.
[0035]
By the way, the above-described deterioration of the recording surface is not limited to the end of the recording data area 4. A similar phenomenon is considered to occur at the beginning. Therefore, it is necessary to give a role similar to that of the guard data area 8 to the VFO area 6 which is the head of the data recording area. Therefore, the role of the VFO area 6 is to suppress the influence of deterioration of the recording surface due to the repeated recording of data in the same recording sector, and the other is for the optical disk apparatus to perform clock reproduction from the reproduction signal. It is. In order to achieve the second role, for example, a rewritable optical disc standardized by ISO (see ISO / IEC10090) is determined to have a length of 12 bytes. As for the guard data recording area 8, one of the roles is to suppress the influence of deterioration of the recording surface due to the repeated recording of data in the same recording sector, and the other is to complete the user data code conversion. This is because the code conversion can be performed uniquely without error during reproduction. The second role can be achieved with a minimum length of 1 byte. Therefore, if the required byte length for achieving the purpose of suppressing the influence of deterioration of the recording surface due to repeated recording of data in the same recording sector, which is a common role, is constant, the length of the guard data recording area 8 The length can be less than or equal to the length of the VFO region 6. Therefore, considering the format efficiency of the sector 1c, the length of the guard data recording area 8 is determined to be equal to or less than the length of the VFO area 6.
[0036]
Note that the buffer area 5 is provided to absorb rotational fluctuations of the optical disk, and no signal is recorded.
[0037]
【The invention's effect】
The optical disc of the present invention is provided with a guard data recording area for recording data of a specific pattern and arbitrary dummy data at the end of the data recording area of each sector. Can be prevented from being lost, and at the same time, the last data of user data can be uniquely converted, and a specific pattern can be repeatedly recorded, so that a specific pattern is erroneously detected during playback. Even if this occurs, the accuracy can be improved by taking a majority decision of a specific pattern by detecting a plurality of times. Furthermore, by detecting a signal of a specific pattern, it is possible to reliably recognize the end of valid data, to know the completion of code conversion, and to initialize the next code conversion.
[0038]
Further, the optical disk of the present invention reduces the format efficiency as much as possible by making the length of the guard data recording area existing at the end of the data recording area of each sector shorter than the length of the VFO area at the head of the data recording area. It is possible to keep the user record data capacity as large as possible and to increase the reliability.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an optical disc in an embodiment of the present invention. FIG. 2 is a diagram for explaining a state modulation code in an embodiment of the present invention. FIG. 3 is for explaining specific pattern data in a guard data recording area. FIG. 4 is a diagram for explaining a signal format of a recording sector of an optical disc according to a conventional example. FIG. 5 is a diagram for explaining an example of dummy data in a guard data recording area.
1a Optical disc 1b Track 1c Sector 2 Header area 3 Gap area 4 Data recording area 5 Buffer area 6 VFO area 7 User data recording area 8 Guard data recording area 8a Specific pattern data 8b Arbitrary data 21 Conversion table 22 D flip-flop 23 Reverse conversion table

Claims (4)

  A data recording area is provided in each sector into which a track is divided into a plurality, and the end of the data recording area is a guard data recording area for recording data of a specific pattern (P1, P2, P3, P4) and dummy data, and at least the guard Data in the data recording area other than the data recording area is converted by selecting one from a plurality of tables based on the state (St), and the data of the specific pattern is the data recording immediately before the data of the specific pattern An optical disc characterized by being data including information for identifying a state (St + 1) determined from data in a region.   2. The optical disc according to claim 1, wherein the data (Dt) in the data recording area is converted in units of 8 bits and becomes 16 bits (Yt) after the conversion.   2. The optical disk according to claim 1, wherein the dummy data in the guard data recording area is a repeated pattern of a byte completion pattern.   3. The optical disc according to claim 1, wherein the information for identifying the state is first bit data of the specific pattern.

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