JP2013101727A - Optical disk medium and optical disk recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a mark edge position with high accuracy in a high-density optical disk.SOLUTION: In an optical disk recording method using a so-called n/2 recording strategy where when n is an integer equal to or greater than 2 and a quotient is q when n is divided by 2, pulse sequences corresponding to marks of length nT are constituted by q units of write power level pulses, the starting time, the ending time or the duration of each pulse in pulse sequences corresponding to marks where n is equal to or greater than 4 is controlled separately for at least the case of being n=4, the case in which n is an even number equal to or greater than 6, and the case in which n is an odd number equal to or greater than 5.

Description

  The present invention relates to an optical disc medium and an optical disc recording method for recording information by irradiating pulsed intensity-modulated laser light, and more particularly to an optical disc medium and an optical disc recording method suitable for high-density recording of information.

  In a recordable optical disc, information is recorded by changing the state of the recording film by irradiating the optical disc with laser light whose intensity is modulated in a pulsed manner, and forming a mark and a space between marks. Of recordable optical disks, DVD-R and DVD + R are well known as recordable optical disks capable of recording information only once, and DVD-RAM, DVD-RW and DVD + RW are well-known as rewritable optical disks capable of overwriting information. Yes. Recently, a Blu-ray Disc (BD), which is a large-capacity optical disc that realizes an information recording capacity of 25 GB per recording layer by using a blue light source, has been put into practical use.

  As a recording method suitable for increasing the recording speed, there is an “N / 2 recording strategy”, which is used in BD and the like. FIG. 1 is a diagram showing a recording pulse waveform in the N / 2 recording strategy. Here, the recording pulse waveform corresponding to the mark of 2T-8T used for the BD RLL (1,7) code and 9T (T is the channel bit length) used for Frame Sync, together with the NRZI data signal Indicated. In the N / 2 recording strategy, when n is an integer, and n is a quotient obtained by dividing n by 2, q is a recording pulse train corresponding to a mark of length nT, which is composed of q write power level pulses. It is a feature. That is, there are one pulse train corresponding to the 2T mark and 3T mark, two pulse trains corresponding to the 4T mark and 5T mark, three pulse trains corresponding to the 6T mark and 7T mark, and pulse trains corresponding to the 8T mark and 9T mark. Consists of four write power level pulses. Thus, every time the recording mark length increases by 2T, the pulse increases by one, and the pulse interval becomes about 2T. One advantage of this method compared to a recording method with a pulse interval of about 1T, such as the “N-1 recording strategy”, is that the time width of each pulse can be increased, so that the rise time and rise time of laser light emission can be increased. It is a point that the influence of the fall time can be reduced. Another advantage is that an amorphous phase mark can be stably formed on a rewritable disc using a phase change recording film because the pulse interval is large and the cooling period is sufficiently long. Due to these advantages, the N / 2 recording strategy is suitable for high-speed recording.

FIG. 2 is a diagram showing the power level of the recording pulse. Here, an 8T mark recording pulse is shown as an example. The output power level of the laser beam, write power _{P W,} space power (erase _{power) P} S _{(P E),} the bias power _{P B,} there is a cooling power _{P C.} The write power _PW is a power level for injecting energy into the recording film to cause a state change. The bias power P _B is a power level corresponding to a gap between pulses of write power. Space power P _S is the power level to irradiate the portion to be the inter-mark (space) to the write-once disc, mainly used for preheating for forming the next mark. Erase power P _E is the power level to irradiate the portion to be a space for rewritable disc using a phase change recording film is used to perform direct rewriting by changing the space to erase the mark . Cooling power P _C is a power level of the cooling pulse, for write-once disc used for the purpose of reducing the blocking and thermal interference diffusion of heat to a subsequent mark recording unit, with respect to a rewritable disc It is used for the purpose of forming an amorphous mark by rapid cooling after heating the recording film. Each power level is a uniform value regardless of the mark length.

Next, the names of pulses corresponding to each power level will be described with reference to FIG. Of the pulses having the write power level _PW , the first pulse is called the first pulse, and the last pulse is called the last pulse. A plurality of pulses between the first pulse and the last pulse is called a multi-pulse. There are no multipulses in the pulse train corresponding to the 2T to 5T marks. A pulse having one write power level _PW in the pulse train corresponding to the 2T mark and the 3T mark is defined as a first pulse. The pulse having a cooling power level P _C immediately after the last pulse is called a cooling pulse.

  Next, control parameters for each pulse will be described with reference to FIG. The pulse control parameters include the first pulse start time dTtop, the first pulse time width Ttop, the multipulse start time dTmp, the multipulse time width Tmp, the last pulse start time dTlp, the last pulse time width Tlp, and the cooling. There is a pulse end time dTs (dTe). dTs is a parameter used for a write-once disc, and dTe is a parameter used for a rewritable disc, both for controlling the width of a cooling pulse. Parameters dTtop, dTmp, dTlp and dTs (dTe) for specifying the start time or end time of the pulse are defined as shown in FIG. 1 with reference to the timing of the NRZI signal. The sign of these parameters is defined as plus when the direction is ahead (left direction in the figure) with respect to the reference time of the NRZI signal and minus when the direction is delayed (right direction in the figure).

  The values of the above control parameters are variable, and the mark edge position can be appropriately controlled by adjusting the values of the parameters. dTtop and Ttop are mainly used to control the front edge position of the mark, and dTlp, Tlp and dTs (dTe) are mainly used to control the rear edge position of the mark.

  In addition, since the edge position of a mark must be controlled in consideration of the influence of heat when recording marks before and after the mark, the time at the start of the pulse and the time width of the pulse are adjacent to the length of the mark. Adaptive recording control is used in which control is performed by classifying the patterns by combinations of space lengths.

  FIGS. 3A to 3E are diagrams showing tables that give specified values of the control parameters of the pulse. (A) dTtop and Ttop are categorized and specified by a pattern of combinations of recording mark lengths (even numbers of 2T, 3T, 4T or more and odd numbers of 5T or more) and preceding space lengths (2T, 3T, 4T and 5T or more). . (B) dTmp is classified and specified only by the recording mark length (an even number of 4T or more and an odd number of 5T or more). (C) A uniform value is designated for Tmp for recording marks of 6T or more regardless of the recording mark length. (D) dTlp and Tlp are specified by being classified according to a combination of recording mark length (an even number of 4T or more and an odd number of 5T or more) and a subsequent space length (2T, 3T, 4T and 5T or more). (E) dTs (dTe) is specified by being classified according to a pattern of combinations of recording mark lengths (even numbers of 2T, 3T, 4T or more and odd numbers of 5T or more) and subsequent space lengths (2T, 3T, 4T and 5T or more). The The adjustment unit of each parameter is 1/16 of the channel bit period (Tw).

  The basic concept of the recording method as described above is disclosed in, for example, Patent Document 1.

  The value of each control parameter is converted into a quotient (integer value) divided by 1/16 of the channel bit period, and is recorded in a control information recording area provided separately from the user data recording area on the disk medium. Stored.

  As a method of adjusting the control parameter of each pulse to an optimum value, for example, there is a method of minimizing edge shift. FIG. 4 shows marks / spaces recorded on the medium, the corresponding equalized reproduction signal, the binarized reproduction signal obtained by binarizing the equalized reproduction signal by the direct slice method, and the channel generated from the binarized reproduction signal. It is the figure which showed the waveform of the bit clock signal typically. Edge shift is the average value of the time difference between the binarized playback signal and the edge of the channel clock signal, normalized by the channel clock period, and indicates the average shift size and direction of the edge position of a specific pattern. ing. The sign of the edge shift is defined as positive when the reproduction signal is delayed with respect to the channel bit clock signal (right direction in the figure) and minus when the reproduction signal is advanced (left direction in the figure).

  FIG. 5 is a flowchart showing an example of a pulse adjustment procedure using the N / 2 recording strategy. The control parameters for each pulse are specified by classification according to the table shown in FIGS.

  After the process starts, in step 11, initial values of pulse control parameters dTtop, Ttop, dTmp, Tmp, dTlp, Tlp, and dTs (dTe) are set. These initial values are acquired by reading the data stored in the control information recording area. Next, in step 12, random data is recorded in the trial writing dedicated area provided on the optical disk medium, and the recorded data is reproduced. Next, in step 13, an edge shift is calculated using the reproduction signal. Here, regarding the edge shift of the front edge of the mark, as shown in FIG. 6A, the recording mark length (2T, 2T, Ttop is used in accordance with the table form of the designated values of dTtop and Ttop used for front edge control. 3T, 4T or more even number and 5T or more odd number) and preceding space length (2T, 3T, 4T and 5T or more) are combined and calculated. With respect to the edge shift of the trailing edge, the recording mark length (2T, 2T, Tlp, Tlp and dTs (dTe) used for controlling the trailing edge is adjusted as shown in FIG. 3T, even 4T or more and 5T or more) and subsequent space lengths (2T, 3T, 4T and 5T or more). Next, in step 14, it is determined whether or not the absolute values of the edge shifts of all patterns have become minimum. If Yes, the process ends. If no, the pattern in which the edge shift remains in step 15 is determined. The value of the corresponding control parameter is updated, and the process returns to step 12 again.

  As described above, the processing is repeated until the absolute values of the edge shifts of all the patterns are minimized, and each control parameter is adjusted.

JP 2005-149540 A

  Recently, in order to further increase the capacity of optical discs, research has been conducted on techniques for increasing the recording capacity per recording layer by increasing the linear recording density based on the BD format.

  However, when recording is performed at a recording density of 30 GB / layer or more using the conventional N / 2 recording strategy, there is a problem that the mark edge position cannot be controlled with high accuracy. This will be described using experimental results.

  The experiment was performed using a commercially available rewritable BD (BD-RE) disc. The conventional N / 2 recording strategy was used as the recording strategy, and the recording capacity per recording layer was set to 33.4 GB (corresponding to channel bit length = 55.8 nm). The control parameters for the recording pulse were specified according to the table of FIG. The adjustment unit of each parameter is 1/16 of the channel bit period. dTmp and Tmp are given as fixed values, respectively, and dTmp (4T, 6T, 8T) = 0, dTmp (5T, 7T, 9T) = 0, and Tmp = 6.

Here, the control parameters dTtop, Ttop, dTlp, Tlp, and dTe were adjusted according to the aforementioned pulse adjustment procedure so that the absolute value of the edge shift of each pattern was minimized. As a result, the values of the control parameters were as shown in FIGS. 7A and 7B. When the recorded portion was reproduced and the edge shift was calculated according to the table shown in FIGS. 6A and 6B, the edge shift value of each pattern was as shown in FIGS. 8A and 8B. It became so. Further, the estimated value of the bit error rate (ratio of the number of error bits in the total number of bits) at this time was 1.7 × 10 ⁻⁷ .

  According to FIGS. 8A and 8B, the absolute value of each edge shift after the pulse adjustment is suppressed to a sufficiently small value, and the recording quality seems to have no problem. However, more detailed analysis revealed the problem.

  8C and 8D show an even number (4T, 6T, 8T) having a recording mark length of 4T or more in the edge shift table of the leading edge and the trailing edge shown in FIGS. 8A and 8B, respectively. ) Are further divided into 4T groups and even (6T, 8T) groups of 6T or more. In the case of the front edge, as shown in FIG. 8C, the edge shift value is almost equal between the group of 4T and the group of even number (6T, 8T) of 6T or more, whereas in the case of the rear edge, As shown in d), the edge shift value is split positively and negatively between the group with a recording mark length of 4T and the group with an even number (6T, 8T) of 6T or more. Although not shown in the drawing, for the group whose recording mark length is an odd number (5T, 7T, 9T) of 5T or more, the split as described above is performed for the 5T group and the odd number (7T, 9T) group of 7T or more. Did not occur.

  FIG. 9 is a histogram showing the distribution of the edge position deviation for the trailing edge of the mark, where the horizontal axis represents the edge position deviation and the vertical axis represents the number of measurement edges. Here, the edge position shift corresponds to the time difference at each edge of the binarized reproduction signal and the channel clock signal in FIG. 4 normalized by the channel clock cycle. FIG. 9A shows the distribution of edge position deviations for even (4T, 6T, 8T) groups having a mark length of 4T or more, together with the distribution (Total) for all mark lengths of 2T to 9T. Also, FIG. 9B shows the distribution of edge position deviations for odd (5T, 7T, 9T) groups with a mark length of 5T or more, together with the distribution (Total) for all mark lengths of 2T to 9T. . According to FIG. 9, (b) for an odd number (5T, 7T, 9T) group of 5T or more, the distribution of edge shifts is generally clustered around edge shift = 0, whereas (a ) For even (4T, 6T, 8T) groups of 4T or more, the edge shift distribution is split into two peaks.

  The edge shift histogram in the case of an even (4T, 6T, 8T) group of 4T or more shown in FIG. 9A is shown in FIG. 8 (d) for the 4T group and the even number (6T, 8T) of 6T or more. Assuming that the edge shift value is split in the group, it can be considered as shown in FIG. That is, the distribution of edge shifts of a group having a mark length of 4T and an even number (6T, 8T) group of 6T or more is split from each other, and a distribution (dashed line) of a group of 4T or more is an even number (6T or more). 6T, 8T) group distribution (dashed line) is closer to the minus side.

  Due to the split of the edge shift distribution as described above, the width of the total edge shift distribution of the even (4T, 6T, 8T) groups of 4T or more is widened, and it is considered that a reproduction error is likely to occur. In the conventional N / 2 recording strategy, since the pulse control parameters are uniformly controlled in groups of even numbers (4T, 6T, 8T) of 4T or more, the edge shift split as described above cannot be corrected.

  When recording is performed at a recording density of 30 GB / layer or more using the conventional N / 2 recording strategy, the edge shift splitting of the trailing edge of the mark as described above is caused by the channel bit length, that is, the mark per 1T. Since the length is smaller than that of the conventional BD, it is considered that the degree of influence of heat accumulation during recording on the trailing edge of the mark is greatly different between 4T and the other (6T and 8T). .

  FIG. 20 shows the front edge of the mark, as in the case of the rear edge of FIG. 9, (a) an even number (4T, 6T, 8T) group of 4T or more and (b) an odd number (5T, 5T, 5T or more). 7T, 9T) is a histogram showing the distribution of the edge shift of the trailing edge of each mark. As can be seen from FIG. 20, in the case of the front edge of the mark, both (a) an even number (4T, 6T, 8T) group of 4T or more and (b) an odd number (5T, 7T, 9T) group of 5T or more are edge shifted. The distribution of is divided into one mountain, and the split of the distribution seen in the case of the trailing edge is not seen. This is as shown in FIG.

  An object of the present invention is to provide an optical disk medium, an optical disk recording method, and an optical disk recording apparatus that can solve the above-described problems and perform high-density recording using an N / 2 recording strategy.

In the present invention, the following means are used to achieve the above object.
(1) Recording method: optical disk recording for recording information by irradiating a control optical disk medium with laser light whose intensity is modulated in a pulse train form at least one of the control parameters to form marks and spaces between the marks. A method,
In the optical disk recording method in which the pulse train corresponding to the mark of length nT is composed of pulses having q write power levels, where n is an integer greater than or equal to 2 and n is a quotient divided by 2;
In a pulse train corresponding to a mark of n = 4 or more, at least one of the start time, end time, or time width of each pulse is used. When n = 4, n = 6 or more and n = 5 or more It was decided to control each of the odd numbers.

  As a result, the control parameter of the pulse can be controlled separately for a group with a recording mark length of 4T and an even group with a recording mark length of 6T or more. Therefore, the split of the edge shift distribution as described in the above problem is performed. Can now be corrected appropriately.

(2) Recording method: Control of at least one of dTlp, Tlp, and dTs (dTe) Start time and time width of the last pulse, which is a pulse of the final write power level, in a pulse train corresponding to a mark with control n = 4 or more , At least one kind of the end time of the cooling pulse which is a pulse immediately after the last pulse, in the case of n = 4, n = 6 or more and n = 5 or more odd number Each was controlled separately.

  This configuration is basically the same as the above (1), but the parameters for dividing the specified value between the group with the recording mark length of 4T and the even group with 6T or more are parameters dTlp, Tlp related to the control of the rear edge. And dTs (dTe). As described above, the edge shift distribution is split mainly between the group having a recording mark length of 4T and the even group having a recording mark length of 6T or more mainly at the rear edge, and almost at the front edge. This is because there is not. As a result, the types of control parameters can be reduced as compared with the case of the predetermined case (1), and there are advantages such as shortening the recording pulse adjustment time.

(3) Recording method; only dTs (dTe) is controlled. In the pulse train corresponding to the mark of n = 4 or more, the end time of the cooling pulse, which is the pulse immediately after the last pulse, is n = 6 or more when n = 4. The control is divided into three cases, i.e., even number and n = 5 or more.

  This configuration is basically the same as the above (2), except that a parameter that divides a specified value between a group with a recording mark length of 4T and an even group with a recording mark length of 6T or more is a parameter dTs (dTe that specifies a cooling pulse width). ) Only. This is because, especially in a rewritable disc, the trailing edge position of the mark contributes most to the cooling pulse width. As a result, the types of control parameters can be further reduced as compared with the case of (2) above, and there is an advantage that the recording pulse adjustment time can be further shortened.

(4) Recording method: front edge and rear edge shift table is separated by 4T, and the edge shift of the front edge and the rear edge corresponding to the mark of n = 4 or more is further performed by the recording method of the above (1) to (3). , N = 4, it is calculated separately for an even group of 6T or more and an odd group of 5T or more,
The parameters are adjusted so that the absolute value of each edge shift is minimized.

  This is a configuration for more ideally implementing the above recording methods (1) to (3). That is, by detecting the edge shift value separately for a group with a recording mark length of 4T and an even group with a recording mark length of 6T or more, each of a parameter with a recording mark length of 4T and an even group with a recording mark length of 6T or more is detected. An optimal designated value can be obtained.

(5) Recording method: 4T separation of rear edge shift table only In the recording method of (1) to (3) above, when the edge shift of the rear edge corresponding to n = 4 or more marks is n = 4 , 6T or more even groups and 5T or more odd groups are calculated separately, and the parameters are adjusted so that the absolute value of each edge shift is minimized.

  This configuration is basically the same as (4) above, but the edge shift value is limited to the trailing edge of the mark to be detected separately for a group with a recording mark length of 4T and an even group with a recording mark length of 6T or more. It is a thing. As described above, since the edge shift distribution is split mainly at the rear edge when the recording mark length is 4T and an even number of 6T or more, the edge shift of the front edge is 4T and 6T or more. This is because it is not necessary to separately detect even numbers. Thereby, the edge shift detection process can be simplified as compared with the above (4).

(6) Recording method: high density The optical disk has a recording capacity of 30 GB or more per recording layer.

  Since the edge shift split between the group having the recording mark length of 4T and the even group having the recording mark length of 6T or more described above becomes particularly noticeable at a high recording density of 30 GB / layer or more, the above (1) to (1) The optical disk recording method (5) becomes more effective when applied to recording at a recording density of 30 GB / layer or higher.

(7) Recording method; RE
The optical disk medium is rewritable.

  The N / 2 recording strategy is mainly used in rewritable discs. Accordingly, the optical disk recording methods (1) to (6) are more effective when applied to a rewritable disk.

(8) Medium: When at least one of the control parameters is control n is an integer of 2 or more and n is a quotient obtained by dividing n by 2, the pulse train corresponding to the mark of length nT has q write powers. Information is recorded by forming a mark and space limited in run length by irradiating laser light intensity-modulated into a pulse train composed of pulses having levels,
In the optical disk medium in which the value of the parameter that specifies the start time and the time width of each pulse in the recording pulse train for forming the mark is stored in a disk information area arranged at a location different from the user data recording area,
When at least one of the parameter values specifying the start time, end time, or time width of each pulse in a pulse train corresponding to a mark of n = 4 or more is n = 4 or n = 6 or more And n is an odd number of 5 or more, and is stored in the disk information area.

  This is an optical disc medium that enables the optical disc recording method (1) to be carried out in an optical disc recording apparatus. In other words, the drive device can perform high-quality recording by reading and setting the designated value of the recording pulse parameter stored in the control information recording area of the optical disk medium having this configuration.

(9) Medium: When at least one of the control parameters is controlled, the difference format n is an integer of 2 or more, and the quotient obtained by dividing n by 2 is q, the pulse train corresponding to the mark of length nT is q. Information is recorded by forming a mark and space limited in run length by irradiating laser light intensity-modulated into a pulse train composed of pulses having a write power level of
In the pulse train corresponding to the mark of n = 5 or more, when at least one of the parameter values specifying the start time, end time, or time width of each pulse is an even number of n = 6 or more and n = 5 or more A difference value between the value of the parameter in the pulse train corresponding to the mark of n = 4 and the value of the parameter in the case of an even number of n = 6 or more is stored in the disc information area and is divided in the case of an odd number. , And stored in the disk information area.

  This configuration is basically the same as the configuration of (8) above, except that the value of the control parameter of the group with a recording mark length of 4T is the difference between the control parameter value of the even group of 6T or more. Is stored in the disk information area. This is because the specified value range is smaller in the difference between the control parameter value of the 4T group and the control parameter value of the even group of 6T or more than the control parameter value itself. This is because the value of the control parameter can be expressed as follows. Thus, there is an advantage that the amount of data stored in the disk information area can be reduced as compared with the configuration (4).

(10) medium; control of at least one of dTlp, Tlp, dTs (dTe), and the start time and time width of the last pulse, which is a pulse of the final write power level, in a pulse train corresponding to a mark of control n = 4 or more, When at least one of the parameter values that specify the end time of the cooling pulse that is the pulse immediately after the last pulse is n = 4, n = 6 or more, and n = 5 or more It was divided into three cases and each was stored in the disk information area.

  This is an optical disc medium that enables the optical disc recording method (2) to be carried out in an optical disc recording apparatus. In other words, the drive device can perform high-quality recording by setting the designated value read from the disk.

  Further, compared with the configuration (4), since the types of control parameters stored in the disk information area on the optical disk medium are reduced, there is an advantage that the data amount of the disk information area can be saved.

(11) Medium; controlling at least one of dTlp, Tlp, dTs (dTe), and the start time of the last pulse, which is the pulse of the final write power level, in the pulse train corresponding to the mark of the difference format n = 5 or more At least one of the parameter values that specify the end time of the cooling pulse, which is the pulse immediately after the last pulse, is divided into an even number of n = 6 or more and an odd number of n = 5 or more, Each is stored in the disk information area,
A difference value between the value of the at least one parameter in the pulse train corresponding to the mark of n = 4 and the value of the at least one parameter when n = 6 or more is stored in the disc information area. It was assumed.

  This configuration is basically the same as the configuration of (10) above, except that the value of the control parameter of the group with a recording mark length of 4T is the difference between the control parameter value of the even group of 6T or more. Is stored in the disk information area. Thus, for the same reason as the configuration (9), there is an advantage that the amount of data stored in the disk information area can be reduced compared to the configuration (10).

(12) Medium; only dTs (dTe) control When the value of a parameter that specifies the end time of a cooling pulse that is a pulse immediately after the last pulse in a pulse train corresponding to a mark of n = 4 or more is n = 4, It is divided into three cases, an even number of n = 6 or more and an odd number of n = 5 or more, which are respectively stored in the disk information area.

  This is an optical disc medium that enables the optical disc recording method (3) to be carried out in an optical disc recording apparatus. In other words, the drive device can perform high-quality recording by setting the designated value read from the disk.

  In addition, since the number of types of control parameters stored in the disc information area on the optical disc medium is further reduced as compared with the configuration in the predetermined case (8), there is an advantage that the data amount of the disc information area can be further saved. .

(13) Medium; dTs (dTe) only, parameter value for specifying the end time of the cooling pulse, which is the pulse immediately after the last pulse, in the pulse train corresponding to the mark of the difference format n = 5 or more is n = 6 or more Are divided into an even number of cases and an odd number of n = 5 or more, which are respectively stored in the disk information area,
The value of the difference between the parameter value in the pulse train corresponding to the mark of n = 4 and the value of the parameter when n = 6 or more is stored in the disc information area.

  This configuration is basically the same as the configuration in (12) above, but the difference between the control parameter value of the group with a recording mark length of 4T and the control parameter value of an even group with a recording mark length of 4T or more. Is stored in the disk information area. Thus, for the same reason as the configuration (9), there is an advantage that the amount of data stored in the disk information area can be reduced compared to the configuration (12).

(14) Medium: A recording capacity of 30 GB or more per high-density recording layer.
As described above, the edge shift split between the group having the recording mark length of 4T and the even group having the recording mark length of 6T or more becomes particularly noticeable at a high recording density of 30 GB / layer or more. The configuration of the optical disk medium of (13) becomes more effective when applied to an optical disk medium of 30 GB / layer or more.

(15) Medium; RE
It was assumed to be rewritable.

  The N / 2 recording strategy is particularly effective for rewritable discs. This is because, as described above, the N / 2 recording strategy has a large pulse interval and a sufficiently long cooling period, so that an amorphous phase mark can be stably formed on a rewritable disc using a phase change recording film. Therefore, the configuration of the optical disk medium (8) to (13) described above becomes more effective when applied to a rewritable disk. In the rewritable disc, the contribution of the cooling pulse width to the trailing edge position of the mark is the largest. Therefore, the effects of the optical disc medium of (12) and (13) are particularly improved by applying the configuration to the rewritable disc. It will be something like that.

  As described above, when the control parameters of the recording pulse are divided into n = 4, even number of n = 6 or more, and odd number of n = 5 or more, the edge shift split is appropriately corrected. As a result, the bit error rate is expected to improve.

The figure which showed the recording pulse waveform of the conventional N / 2 recording strategy. The figure which showed the power level of the recording pulse. The figure which showed the recording pulse parameter table of the conventional N / 2 recording strategy. The figure which showed the edge shift calculation method. The figure which showed the conventional recording pulse adjustment flow. The figure which showed the table of the edge shift value corresponding to the conventional N / 2 recording strategy. The figure which showed the setting value of the control parameter of the pulse at the time of using the conventional N / 2 recording strategy. The figure which showed the setting value of the control parameter of the pulse at the time of using the conventional N / 2 recording strategy. The figure which showed the detected edge shift value at the time of using the conventional N / 2 recording strategy. The figure which showed edge shift distribution of the rear edge at the time of using the conventional N / 2 recording strategy. The figure which showed typically the distribution of the edge shift at the time of using the conventional N / 2 recording strategy. The figure which showed the setting value of the control parameter of the pulse at the time of applying this invention. The figure which showed the setting value of the control parameter of the pulse at the time of applying this invention. The figure which showed the edge shift detection table of this invention. The figure which showed the table of the edge shift value at the time of applying this invention. The figure which showed distribution of the edge shift at the time of applying this invention. The figure which showed the structural example of the optical disk apparatus of this invention. The figure which showed the Example of the pulse control parameter table of this invention. The figure which showed the recording pulse adjustment flow of this invention. The figure which showed the Example of the pulse control parameter table of this invention. The figure which showed the Example of the pulse control parameter table of this invention. The figure which showed edge shift distribution of the front edge at the time of using the conventional N / 2 recording strategy. The figure which showed the setting value of the control parameter of the pulse at the time of applying this invention. The figure which showed the setting value of the control parameter of the pulse at the time of applying this invention. The figure which showed the table of the edge shift value at the time of applying this invention. The figure which showed distribution of the edge shift at the time of applying this invention. The figure which showed the setting value of the control parameter of the pulse at the time of applying this invention. The figure which showed the setting value of the control parameter of the pulse at the time of applying this invention. The figure which showed the data structure of the disc information area | region in the optical disc medium of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  This will be described using experimental results as follows. The experiment was performed according to the following procedure.

  First, an appropriate initial value is given to each control parameter dTtop, Ttop, dTmp, Tmp, dTlp, Tlp, and dTe of the recording pulse using an N / 2 recording strategy on a commercially available rewritable BD (BD-RE) disc. Record random data. The recording capacity per recording layer is 33.4 GB (channel bit length = 55.8 nm). The adjustment unit of each parameter is 1/16 of the channel bit period. For dTmp and Tmp, dTmp (4T, 6T, 8T) = 0, dTmp (5T, 7T, 9T) = 0 and Tmp = 6 are given, respectively, and these are fixed values and are not adjusted thereafter.

  Next, the recorded location is reproduced and an edge shift is detected from the reproduced signal. The detected edge shifts are classified into (a) mark front edge shift and (b) mark rear edge shift according to the table shown in FIG.

  Next, parameters dTtop, Ttop, dTlp, Tlp, and dTe that control the front edge or the rear edge of the mark are adjusted so that the absolute value of each edge shift in the edge shift detection table is minimized.

  The above experiment was performed using two types of control parameter tables based on the present invention.

  The first table is based on the solution (2), with the last pulse start time dTlp, the last pulse time width Tlp, and the cooling pulse end time dTE, the recording mark length is a group of 4T and an even number of 6T or more. It is specified by dividing into groups.

  At this time, the value of each control parameter was as shown in FIGS. 11A and 11B as a result of adjustment. In addition, the edge shift value of each pattern at this time is as shown in FIG.

  FIG. 14 is a histogram showing the edge shift distribution. According to FIG. 14, by using the N / 2 recording strategy to which the pulse control parameter of the present invention is applied, the conventional N / 2 recording mark length is divided into 4T groups and even (6T, 8T) groups of 6T or more. The split of the edge shift of the trailing edge of the mark seen in between was corrected appropriately, and the total distribution of even (4T, 6T, 8T) groups of 4T or more was gathered.

Moreover, the estimate of the bit error rate, the conventional N / 2 recording strategy whereas was 1.7 × 10 ^-7 in the case of using, by applying the present invention 6.3 × 10 ^- Improved to ⁸ .

  In the second table, only the end time dTE of the cooling pulse is specified based on the solution (3), divided into a group with a recording mark length of 4T and an even number group with 6T or more.

  At this time, the values of the control parameters were as shown in FIGS. 21A and 21B as a result of the adjustment. In addition, the edge shift value of each pattern at this time is as shown in FIG.

FIG. 23 is a histogram showing an edge shift distribution. As described above, even when the parameter controlled separately when the recording mark length is 4T and when the recording mark length is an even number of 6T or more is limited only to the end time of the cooling pulse, the edge shift split at the trailing edge of the mark is appropriate. The total distribution of the even (4T, 6T, 8T) groups of 4T or more has been gathered in one mountain.
In addition, the bit error rate when this configuration is applied is 6.1 × 10 ^−8, which is an improvement over the conventional N / 2 recording strategy.

  It is clear that the improvement of the bit error rate is due to the fact that the edge shift distribution is corrected to an ideal distribution as shown in FIG. 10B, regardless of which table is used. The improvement of the bit error rate increases the margin for various disturbances during the operation of the drive device, and contributes to higher recording / reproducing speed and higher recording density. From the above results, the effect of the present invention was shown.

  In the present embodiment, an example in which 4T is separated for all parameters will be described.

  A configuration example of an optical disc apparatus suitable for carrying out the present invention will be described. Here, a BD system is assumed. FIG. 15 is a schematic diagram showing a configuration example of an optical disc apparatus to which the present invention is applied. The optical disk medium 100 mounted on the apparatus is rotated by a spindle motor 160. During reproduction, the laser power / pulse controller 120 controls the current flowing to the semiconductor laser 112 via the laser driver 116 in the optical head 110 so that the light intensity commanded by the dTs (dTe) U 140 is obtained. Is generated. The laser beam 114 is condensed by the objective lens 111 to form the light spot 101 on the optical disc medium 100. The reflected light 115 from the light spot 101 is detected by the photodetector 113 via the objective lens 111. The photodetector is composed of a plurality of photodetecting elements. The reproduction signal processing circuit 130 reproduces information recorded on the optical disc medium 100 using the signal detected by the optical head 110. The entire apparatus is controlled by the system controller 200.

  The reproduction signal processing circuit 130 generates a channel bit clock signal by performing processing such as a band limiting filter, an auto slicer, and a PLL (Phase Locked Loop) on the signal detected by the optical head 110, and binarizes the signal. A reproduction signal is generated. The edge shift detector 135 uses the channel bit clock signal and the binarized reproduction signal generated by the reproduction signal processing circuit 130 to calculate the time difference between the binarized reproduction signal and the channel bit clock signal at the reproduction signal edge. The value normalized by the clock cycle is measured as an edge shift. Further, the edge shift value at each measurement edge is classified by a combination pattern of the mark length, the preceding space length, and the preceding mark length based on the data pattern of the binarized reproduction signal, and is summed up for each pattern to perform edge shift. Calculate and output the average value.

  Next, a configuration example of the laser power / pulse control unit 120 will be described. Here, it is assumed that the N / 2 recording strategy shown in FIG. 1 is used as the recording method.

Output power level P _W of the laser _{light, P} S (P _E), as P _B and P _C, using the value specified by data recorded in the control information storage area of the optical disc medium. If there is no specified power level, each power level is determined by performing trial writing.

  As for the pulse parameters, the set values of the time dTtop at the start of the first pulse and the time width Ttop of the first pulse are given according to the table shown in FIG. 16A, and the multipulses are set according to the table shown in FIG. A set value of the start time dTmp is given, and a set value of the multi-pulse time width Tmp is given according to the table shown in FIG. 16C, and the time dTlp at the start of the last pulse is given according to the table shown in FIG. , A set value of the time width Tlp of the last pulse is given, and a set value of the end time dTs (dTe) of the cooling pulse is given according to the table shown in FIG. That is, dTtop and Ttop are set for each combination pattern of the mark length and the preceding space length according to the parameter table of FIG. 16A, and dTlp, Tlp, and dTs (dTe) are the parameters of FIG. Set according to the table for each combination of mark length and trailing space length.

  Next, an embodiment of the recording pulse adjusting method according to the present invention will be described. FIG. 17 is a flowchart showing an example of a procedure for adjusting a pulse control parameter. The N / 2 recording strategy is used as the recording strategy, and the parameters dTtop and Ttop relating to the control of the front edge position according to the table shown in FIG. 16 are the recording mark length (an even number of 2T, 3T, 4T, 6T or more and an odd number of 5T or more). The leading space lengths (2T, 3T, 4T, and 5T or more) are classified into 5 × 4 patterns, and the parameters dTlp, Tlp, and dTs (dTe) relating to the control of the trailing edge are recorded mark lengths (2T, 3T, 4T, The pattern is classified into a 5 × 4 combination pattern of an even number of 6T or more and an odd number of 5T or more) and a subsequent space length (2T, 3T, 4T, and 5T or more).

  After starting the processing, in step 21, initial values of pulse control parameters dTtop, Ttop, dTmp, Tmp, dTlp, Tlp, and dTs (dTe) are set. The control parameter setting value table is the same as that shown in FIG. In step 22, random data is recorded at a predetermined location on the optical disk medium, and the recorded data is reproduced. In step 23, edge shifts are calculated using the reproduction signal, and are classified into combinations of recording mark lengths and preceding / following space lengths. Here, the edge shift of the front edge of the mark is classified into the same form as the table of FIG. 16A, and the edge shift of the rear edge of the mark is the same as the table of FIGS. 16D and 16E. Classified into shapes. In step 24, it is determined whether or not the absolute values of the edge shifts of all the patterns are minimum, and if yes, the process ends. If no, it corresponds to the pattern in which the edge shift remains in step 25. The value of the control parameter of the pattern to be updated is updated, and the process returns to step 22.

  As described above, the control parameters are determined so that the absolute values of the edge shifts of all patterns are minimized.

  In the present embodiment, an embodiment of an optical disk medium in which specified values of control parameters are stored in a disk information area will be described.

  The specified value of the control parameter is compiled into “disc information” which is a set of various information necessary for recording and reproduction of the disc, and is recorded in the disc information area located on the inner circumference of the user data recording area on the optical disc medium. The

  FIG. 25 is a schematic diagram showing the data structure of disk information. One unit of disk information (the upper part of FIG. 25) is composed of a header, a main body of disk information, and a footer.

  Of these, the disc information body includes information relating to the medium type, information relating to the data transfer speed, parameters relating to the recording / reproducing power, etc. in addition to the recording pulse control parameters.

  The configuration of the recording pulse control parameters (shaded area in the figure) will be described. Here, as an example, a configuration is used in which the values of dTlp, Tlp, and dTe are specified separately for a group with a recording mark length of 4T and an even group of 6T or more based on the solution (11). In this configuration, each control parameter is classified as shown in FIG. 18, and data of 1 byte is assigned to each classified parameter.

  The breakdown of 1-byte (8-bit) data is, for example, as shown in the lower part of FIG. This figure is an example in the case of the time width Ttop of the first pulse. Of the 8 bits, the upper 6 bits (bit 7 to bit 2) store the quotient (integer value) obtained by dividing the designated time width by 1/16 of the channel bit clock period in binary form. In this case, the time width is specified in the range of 0 to 63. The remaining 2 bits (bit 1 to bit 0) are unused bits, and “00” is stored as a fixed value.

  The specified values of other control parameters are also stored in the disk information area in the same manner. However, since dTtop, dTlp, and dTe can take positive and negative values, 2's complement expression is used to specify an integer value. For example, in the case of the start time dTtop of the first pulse, although not shown, the integer value is specified in the range of −16 to 15 by using the upper 5 bits of 8 bits.

  Further, when the optical disk medium having this configuration is used in a drive device, the value of each control parameter is calculated by multiplying the integer value by the channel bit period.

  Next, an embodiment of an optical disk medium in which the difference between the control parameter value of a group with a recording mark length of 4T and an even group of 6T or more is stored in the disk information area will be described.

  Here, as in the third embodiment, as an example, a configuration in which the values of dTlp, Tlp, and dTe are specified separately for a group with a recording mark length of 4T and an even group of 6T or more is used based on the solution (11). . Each control parameter is classified as shown in FIG.

  In this configuration, the difference from the third embodiment is that in the case of dTlp, Tlp, and dTe, when the recording mark length is a group of 4T, the difference between the value of the 4T group and the value of the even group of 6T or more is calculated as the disc information area. It is a point to store in.

  The difference value is assigned to 4 bits, and is specified in the range of -4 to +3 in the case of 2's complement expression. This designated range is large enough to designate the difference between the 4T group and the even group of 6T or more.

Assume that the designated values of the control parameters are as shown in FIGS. 11A and 11B. At this time, the values stored in the disk information area are as shown in FIGS. 24A and 24B. That is, for a group with a recording mark length of 4T, the value stored in the disc information area is the difference between the value of the 4T group and the value of the even group of 6T or more, 0−0 = 0 for dTlp and 0−1 for Tlp. For 6-7 = (− 1) and dTe, (−1) − (− 2) = (+ 1).
Since the range of the specified value becomes smaller, it can be expressed with a smaller number of bits.

  Here, as in this configuration, the difference value is designated by 4 bits, one parameter is set for the upper 4 bits (bit 7 to bit 4) in 1 byte data, and the lower 4 bits (bit 3 to bit 0) are set. By assigning another parameter, it is possible to store the specified values for two parameters in one byte. In this configuration, in this configuration, there are a total of 12 types of control parameters for the group having a recording mark length of 4T with respect to dTtop, dTlp, and dTe. Therefore, the data amount of the disc information is 6 bytes less than the configuration of the third embodiment. Become.

  Further, when the optical disk medium of this configuration is used in a drive device, an integer value when the recording mark length is 4T can be obtained by adding the above difference to the integer value when the recording mark length is an even group of 6T or more. By multiplying this by the channel bit period, the value of the control parameter when the recording mark length is 4T is calculated.

  The effects of the present invention are not limited to the embodiments described above.

  In the above embodiment, the edge shift calculated based on the time difference between the channel bit clock signal and the binarized reproduction signal is used as the edge shift. However, the present invention is not limited to this. As the edge shift in a broad sense, an edge shift calculated based on the Euclidean distance difference between the target signal and the reproduction signal in the reproduction system using PRML may be used. Needless to say, the same effect can be obtained not only with RLL (1, 7) but also with an N / 2 recording strategy.

100: optical disk 101: light spot 110: optical head 111: objective lens 112: semiconductor laser 113: photodetector 114: laser light 115: reflected light 116: laser driver 120: laser power / pulse controller 130: reproduction signal processor 135: Edge shift detector 140: dTs (dTe) U
160: spindle motor 200: system controller

Claims (15)

An optical disk recording method for recording information by irradiating an optical disk medium with laser light intensity-modulated in a pulse train to form marks and spaces between the marks,
In the optical disk recording method in which the pulse train corresponding to the mark of length nT is composed of pulses having q write power levels, where n is an integer greater than or equal to 2 and n is a quotient divided by 2;
Parameters for designating at least one of the start time, end time, and time width of each pulse in a pulse train corresponding to a mark of n = 4 or more, when at least n = 4, when n = 6 or more, and An optical disc recording method, wherein control is performed separately for each odd number of n = 5 or more. In the pulse train corresponding to the mark of n = 4 or more, at least one of the start time and time width of the last pulse that is the pulse of the last write power level, and the end time of the cooling pulse that is the pulse immediately after the last pulse is selected. 2. The optical disk recording method according to claim 1, wherein the control is performed in three cases: n = 4, n = 6 or more, and n = 5 or more. In the pulse train corresponding to the mark of n = 4 or more, the end time of the cooling pulse that is a pulse immediately after the last pulse is set to n = 4, n = 6 or more, and n = 5 or more. 2. The optical disk recording method according to claim 1, wherein the control is performed separately for each of three cases. The edge shifts of the front edge and the rear edge corresponding to the mark of n = 4 or more are calculated separately for an even group of 6T or more and an odd group of 5T or more when n = 4, respectively.
4. The optical disc recording method according to claim 1, wherein the parameter is adjusted so that an absolute value of each edge shift is minimized. The edge shift of the rear edge corresponding to the mark of n = 4 or more is calculated separately for an even group of 6T or more and an odd group of 5T or more when n = 4,
4. The optical disc recording method according to claim 1, wherein the parameter is adjusted so that an absolute value of each edge shift is minimized. 6. The optical disc recording method according to claim 1, wherein the optical disc has a recording capacity of 30 GB or more per recording layer. 7. The optical disc recording method according to claim 1, wherein the optical disc medium is a rewritable type. When n is an integer of 2 or more and n is a quotient obtained by dividing 2 by q, a pulse train corresponding to a mark of length nT is intensity-modulated into a pulse train composed of pulses having q write power levels. Information is recorded by forming marks and spaces with run length limited by irradiating the laser beam.
In the optical disc medium in which the value of the parameter that specifies the start time and the time width of each pulse in the pulse train for forming the mark is stored in a disc information area arranged at a location different from the user data recording area,
In the pulse train corresponding to the mark of n = 4 or more, when at least one of the parameter values specifying the start time, end time or time width of each pulse is n = 4, an even number of n = 6 or more And an odd number of n = 5 or more, and each is stored in the disk information area. When n is an integer of 2 or more and n is a quotient obtained by dividing n by 2, the pulse train corresponding to the mark of length nT is intensity modulated into a pulse train composed of pulses having q write power levels. Information is recorded by forming marks and spaces limited in run length by irradiating the laser beam.
In the optical disc medium in which the value of the parameter that specifies the start time and the time width of each pulse in the pulse train for forming the mark is stored in a disc information area arranged at a location different from the user data recording area,
In the pulse train corresponding to the mark of n = 5 or more, when at least one of the parameter values specifying the start time, end time, or time width of each pulse is an even number of n = 6 or more and n = 5 or more Are stored in the disk information area, respectively.
An optical disc characterized in that a difference value between the value of the parameter in the pulse train corresponding to the mark of n = 4 and the value of the parameter when n = 6 or more is stored in the disc information area Medium. The value of the parameter that specifies the start time and time width of the last pulse that is the pulse of the last write power level, and the end time of the cooling pulse that is the pulse immediately after the last pulse in the pulse train corresponding to the mark of n = 4 or more At least one of them is divided into three cases: n = 4, even number of n = 6 or more, and odd number of n = 5 or more, each of which is stored in the disk information area. 9. The optical disk medium according to claim 8, wherein the optical disk medium is characterized. Parameter values specifying the start time and time width of the last pulse that is the pulse of the last write power level and the end time of the cooling pulse that is the pulse immediately after the last pulse in the pulse train corresponding to the mark of n = 5 or more At least one of them is divided into an even number of n = 6 or more and an odd number of n = 5 or more, which are respectively stored in the disk information area,
A difference value between the value of the at least one parameter in the pulse train corresponding to the mark of n = 4 and the value of the at least one parameter when n = 6 or more is stored in the disc information area. 10. The optical disk medium according to claim 9, wherein In the pulse train corresponding to the mark of n = 4 or more, the value of the parameter that specifies the end time of the cooling pulse that is the pulse immediately after the last pulse is n = 4, n = 6 or more, and n 9. The optical disc medium according to claim 8, wherein the optical disc medium is divided into three cases of an odd number of 5 or more and each is stored in the disc information area. In the pulse train corresponding to the mark of n = 5 or more, the value of the parameter that specifies the end time of the cooling pulse that is the pulse immediately after the last pulse is an even number of n = 6 or more, and an odd number of n = 5 or more. Divided into cases, each stored in the disk information area,
The difference value between the value of the parameter in the pulse train corresponding to the mark of n = 4 and the value of the parameter when n = 6 or more is stored in the disc information area. Item 10. An optical disk medium according to Item 9. The optical disk medium according to any one of claims 8 to 13, wherein the optical disk medium has a recording capacity of 30 GB or more per recording layer. The optical disk medium according to claim 8, wherein the optical disk medium is a rewritable type.

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