JP2011253604A - Optical information recording and playback equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide optical information recording and playback equipment capable of calculating the edge shift length of a combination of a mark including 2T and space in the case of using a playback system by PRML processing using a PR equalizer of constraint length 5.SOLUTION: As an intersection level, an intersection level selecting device of optical information recording and playback equipment selects a 2T intersection level that can intersect a playback waveform when a combination of a detected mark and space includes 2T, and selects a standard intersection level when the combination does not include 2T. In the optical information recording and playback equipment, an edge shift length calculation device calculates edge shift length on the basis of an amplitude value of playback waveform information before and after intersecting the selected intersection level, and a statistical processing device reflects the edge shift length on a recording strategy, thereby recording of optimum quality is achieved.

Description

  The present invention relates to an optical information recording / reproducing apparatus. In particular, the present invention relates to an optical information recording / reproducing apparatus having means for measuring an edge shift length of a signal reproduced from an information recording medium and adjusting a recording strategy based on the measured edge shift length.

  On the optical disk medium, data to be recorded is encoded by various prescribed methods, and recording is performed in a binary state of a plurality of marks and spaces having a predetermined length. For example, Blu-ray uses 1-7PP modulation to modulate and record binary data having a length of 2T to 10T. Here, T is a channel clock cycle. During reproduction, this signal is read, the lengths of marks and spaces are detected, decoded by various prescribed methods, and restored to the original data.

  Here, if the mark length and space length detected at the time of reproduction are exactly the same as the recorded length, the performance will not deteriorate, but marks of an undesired shape are easily formed due to thermal interference, etc. The edge position shifts to a slightly different length. That is, jitter occurs. This affects the reproduction performance, and the larger the jitter, the more likely the error occurs in the reproduced data, unlike the recorded data. This actual condition is described in Patent Document 1.

  In Patent Document 1, each time a reproduction data string crosses the intersection level with the center of the ideal signal amplitude as the intersection level, mT mark and nT space (m and n are integers of 2 or more, T is a channel clock period). Classification. Further, for each mark and space, the phase error from the reference level at the time of polarity inversion is integrated, and the accumulated value is divided by the number of occurrences to obtain the jitter amount. Then, paying attention to the combination of mT mark and nT space, adjust the leading edge edge position and trailing edge edge position of the recording mark, find the edge shift length that will be the optimum recording condition with little jitter at the time of reproduction, and record again Yes.

  Further, Patent Document 2 describes a method for obtaining the edge shift length from the slope of data values before and after the intersection as a calculation method when the intersection level is intersected.

  The mainstream of regeneration processing in recent years is PRML (Partial Response and Maximum Likelihood). As shown in FIG. 8, PRML is composed of a two-step process in which a reproduction signal is equalized to PR characteristics by a PR equalizer 4 and then Viterbi decoded by a Viterbi decoder 5. Originally, intersymbol interference is a factor that degrades mark and space identification performance, but PRML actively uses intersymbol interference. As shown in FIG. 8, the output of the PR equalizer 4 is set to a signal P having intersymbol interference, and is decoded by the Viterbi decoder 5 to obtain a binary signal V. As described above, PRML has an advantage that mark and space identification performance can be improved in the entire PRML by a combination of PR equalization and Viterbi decoding.

  As shown in FIG. 8, for example, when the PR equalizer coefficient is (1221), when the output P of the PR equalizer 4 outputs 1, 2, 2, 1 having code interference, Viterbi decoding is It is adjusted to output an impulse. The PR equalizer 4 is composed of an FIR filter, and the output of the PR equalizer is adjusted to 1, 2, 2, 1 by adjusting the filter coefficient.

  In this specification, a PR equalizer having a PR equalization coefficient of (abba) is represented as PR (abba). Further, the length of the PR equalization coefficient is called a constraint length. For example, PR (abba) is PR equalization with a constraint length of 4, and PR (abcba) is PR equalization with a constraint length of 5.

  FIG. 9 shows an example of an ideal waveform of PR (1221) having a constraint length of 4. Here, the recording data string in FIG. 9 has a pattern in which marks and spaces repeat every 3T. That is, when expressed in binary data, the recording data string is a repeating pattern of 0, 0, 0, 1, 1, 1. In this specification, such a recording data string is expressed as S3T and M3T repetition. When this recording data is reproduced, the output P of the PR equalizer 4 in FIG. 8 is ideally a convolution calculation result of the recording data string and the PR equalization coefficient. The output of the PR equalizer thus obtained is called a PR ideal waveform. In PRML, the FIR filter coefficient of the PR equalizer 4 is adjusted so that the output signal P of the PR equalizer 4 reproduced from the actually recorded optical disk medium is close to an ideal waveform. The output signal P of the PR equalizer has a waveform close to the PR ideal waveform. A signal NRZI shown in the lower part of FIG. 9 represents the output V of the Viterbi decoder, and FIG. 9 shows that the original recording data string can be accurately reproduced.

  The jitter of the optical recording / reproducing apparatus is usually performed by measuring the position coordinates of the point where the output signal of the PR equalizer 4 crosses zero. In the recorded data sequence, when the frequency of 0 and 1 is equal, the DC component is zero, so the PR ideal waveform and the actual PR equalizer output signal are also normalized so that the DC component is zero. Turn into. At that time, the PR ideal waveform and the output signal of the actual PR equalizer usually have a positive value at the mark position and a negative value at the space position, and therefore cross zero. Therefore, the crossing level is set to zero, the rising position of the leading edge of the recording mark and the trailing edge of the trailing edge of the recording mark are measured from the position coordinates of the point where the crossing level and the output signal of the PR equalizer cross, and the edge shift is performed. The length can be calculated.

  By performing this method on combinations of mT marks and nT spaces, the edge shift lengths of all combinations are calculated. Then, adjustment for optimum recording is performed by correcting the correction parameter for recording strategy adjustment according to the edge shift length.

International Publication No. 02/084653 JP 2006-120208 A JP 2004-213862 A JP 2003-006864 A

  The following analysis is given by the present invention.

  As shown in FIGS. 9, 10, and 11, in the PR equalizer of PR (1221), the output waveform of the PR equalizer is a waveform having a positive value at the mark position and a negative value at the space position. Become. In FIG. 10, the mark length of the recording data string is 2T, and in FIG. 11, the space length of the recording data string is 2T. In the PR ideal waveforms of FIGS. 10 and 11, the positive part and the negative part are asymmetric, but the condition of zero crossing can be secured.

  However, in recent years, a PR equalizer having a constraint length of 5 has come to be frequently used due to a demand for higher density. For example, a PR (12221) PR equalizer is employed in an HD-DVD that realizes high-density recording. As shown in FIGS. 13 and 14, when either the mark or the space is 2T of the shortest specification, the output waveform P of the PR equalizer 4 is a waveform having amplitudes up and down centering on zero. Therefore, when the intersection level is set to zero, the intersection cannot be detected. Even in a coefficient other than (12221), when the constraint length is 5, when either mark or space includes 2T, the output waveform P of the PR equalizer 4 is generally centered on zero. Therefore, if the intersection level is zero, the intersection cannot be detected. That is, there are many cases where the condition of zero crossing is not satisfied.

  Here, the problem of the conventional optical information recording / reproducing apparatus is that, in a PR equalizer with a PR (abcba) constraint length of 5, if either of consecutive marks or spaces includes 2T, the edge shift length is This means that the recording strategy cannot be adjusted and the recording strategy cannot be adjusted for optimal recording.

  An optical information recording / reproducing apparatus according to a first aspect of the present invention is an apparatus for recording and reproducing binary data on an information recording medium by marks and spaces, and a signal obtained by reproducing the data of the information recording medium is restrained length. 5, a PR equalizer for PR equalization, a Viterbi decoder for restoring the binary data by Viterbi decoding the PR equalized signal, and a continuous restored by the Viterbi decoder with T as a channel clock period When the lengths of the marks and spaces are both 3T or more, a predetermined standard crossing level is set as the crossing level, and when either length is 2T, 2T different from the predetermined standard crossing level is set. An edge signal for obtaining an edge shift length based on a position at which the output signal of the intersection level selector having the intersection level as the intersection level and the PR equalizer intersects the intersection level. It has a preparative length calculator, on the basis of the edge shift length, and a recording strategy adjuster for adjusting the rising position and falling position of the mark trailing edge of the mark leading edge.

  A recording strategy adjusting method according to a second aspect of the present invention is a recording strategy adjusting method for an optical information recording / reproducing apparatus that records and reproduces binary data by using marks and spaces on an information recording medium, from the information recording medium. A step of reproducing data, a step of PR equalizing a read signal from the information recording medium with a constraint length of 5, and a signal equalized by PR in the step of PR equalization are Viterbi-decoded and the binary data , A step of detecting whether the length of a continuous mark or space includes 2T from the recovered binary data with T as a channel clock period, and the continuous mark and space If both are 3T or longer, the step of setting a predetermined standard intersection level as the intersection level and the continuous If either of the first and second space lengths is 2T, a step of setting a 2T crossing level different from the predetermined standard crossing level as the crossing level, and the PR equalized signal crosses the crossing level. Calculating the edge shift length based on the position to be adjusted, and adjusting the rising position of the mark leading edge or the trailing edge of the mark based on the edge shift length.

  According to the present invention, the following effects can be obtained. The first effect is that it is possible to provide a high-quality optical information recording / reproducing apparatus capable of adjusting a recording strategy including 2T when a reproducing method using a PR equalizer with a constraint length of 5 is used. That is. The reason is that the optical information recording / reproducing apparatus of the present invention has a 2T crossing level different from a predetermined standard crossing level even if the length of either a continuous mark or space includes 2T. This is because the edge shift length can be obtained from the point where it intersects with the output signal of the PR equalizer as the intersection level, so that it is possible to adjust the recording strategy including 2T.

  The second effect is that a recording strategy adjustment method including 2T can be provided in a reproduction method using a PR equalizer with a constraint length of 5. This is because the recording strategy adjustment method of the present invention uses a 2T crossing level different from a predetermined standard crossing level even if the length of either a continuous mark or space includes 2T. This is because the edge shift length can be obtained from the point that intersects with the output signal of the PR equalizer, so that the recording strategy including 2T can be adjusted.

It is a block diagram which shows the optical information recording / reproducing apparatus by Example 1 of this invention. It is a flowchart which shows the recording strategy adjustment method in the optical information recording / reproducing apparatus by Example 1 of this invention. It is a figure for demonstrating the recording strategy adjustment of this invention. It is a figure for demonstrating the edge shift length calculation in Example 1 of this invention. FIG. 6 is a relationship diagram between an edge shift length and a PRSNR in Embodiment 1 of the present invention. It is a block diagram of 2T crossing level calculation in Example 2 of the present invention. It is a figure for demonstrating the PR ideal waveform generation part in Example 2 of this invention. It is a principle figure for demonstrating PR equalization and Viterbi decoding. It is a figure which shows PR ideal waveform. It is a figure which shows PR ideal waveform. It is a figure which shows PR ideal waveform. It is a figure which shows PR ideal waveform. It is a figure which shows PR ideal waveform. It is a figure which shows PR ideal waveform. It is a figure which shows PR ideal waveform. It is a figure which shows PR ideal waveform. It is a figure which shows PR ideal waveform. It is a figure which shows PR ideal waveform. It is a figure which shows PR ideal waveform. It is a figure which shows the correction table of the recording strategy adjustment of this invention. It is a figure which shows the correction table of the conventional recording strategy adjustment.

  Embodiments of the present invention will be described with reference to the drawings as necessary. In addition, drawing quoted in description of embodiment and the code | symbol of drawing are shown as an example of embodiment, and, thereby, the variation of embodiment by this invention is not restrict | limited. An embodiment of the present invention will be described with reference to FIGS. 1 and 2 as necessary.

  As shown in FIG. 1, an optical information recording / reproducing apparatus 16 according to the first embodiment of the present invention is an apparatus for recording and reproducing binary data on an information recording medium 1 with marks and spaces. A PR equalizer 4 for PR equalizing a signal reproduced from one data with a constraint length of 5, a Viterbi decoder 5 for restoring the binary data by Viterbi decoding the PR equalized signal, and T for a channel clock As a cycle, when the lengths of consecutive marks and spaces restored by the Viterbi decoder 5 are both 3T or more, a predetermined standard crossing level is set as a crossing level, and when either length is 2T, The edge shift length is obtained based on the position where the output signal of the cross level selector 9 and the PR equalizer 4 crossing the cross level with a 2T cross level different from the predetermined standard cross level. That has an edge shift length calculator 11, based on the edge shift length, a recording strategy adjuster 14 for adjusting the trailing edge point of the rising edge position and mark trailing edge of a mark leading edge, a.

  As shown in FIG. 2, the recording strategy adjusting method of the second embodiment according to the present invention is a recording strategy adjusting method for an optical information recording / reproducing apparatus that records and reproduces binary data by using marks and spaces on an information recording medium 1. In step S20 for reproducing data from the information recording medium 1, a read signal from the information recording medium 1 is PR equalized in step S21 for PR equalization with a constraint length of 5, and in step S21 for PR equalization. Step S22 for recovering the signal by Viterbi decoding and recovering the binary data, and detecting whether the length of the continuous mark or space includes 2T from the recovered binary data with T as the channel clock period If the length of both the continuous mark and the space is 3T or more, the predetermined standard intersection level is set to the intersection level. If the length of the continuous mark or space is 2T, step S25 that sets a 2T crossing level different from a predetermined standard crossing level, and PR equalization Step S26 for calculating the edge shift length based on the position where the signal crosses the intersection level; Step S27 for adjusting the rising position of the mark leading edge or the trailing edge of the mark based on the edge shift length; including.

  Hereinafter, embodiments will be described in detail with reference to the drawings.

[Configuration of Example 1]
FIG. 1 is an overall block diagram showing Embodiment 1 of the present invention. The RF waveform reproduced by the optical head 2 from the information recording medium 1 such as an optical disk is sampled by the A / D converter 3 and converted into a digital signal. The digitized RF signal is decoded by the PR equalizer 4 and the Viterbi decoder 5 into the most likely binary data by PRML processing.

  The PR equalization coefficient in the PR equalizer 4 is configured to be freely settable. In the first embodiment, a constraint length of 5 (12221) is set. Further, according to the set PR equalization coefficient, as shown in FIG. 8, the FIR filter coefficient in the PR equalizer 4 is adjusted so as to obtain a desired PR equalization characteristic.

  A recording data pattern for adjusting the recording strategy is given by the recording data generator 13, and in the first embodiment, a 2T mark length and a 2T space length are included.

  The binary data subjected to the Viterbi decoding is supplied to the 2T detector 6 and the 3T or more detector 7. First, the 2T detector 6 detects whether the length of the binary data subjected to Viterbi decoding matches 2T. The 3T or more T length detector 7 detects the data length when the binary data is 3T or more. The delay unit 8 holds the output of the PR equalizer 4 for the time required for calculation and detection processing in the Viterbi decoder 5, 2T detector 6, 3T or more T length detector 7. In the intersection level selector 9, in the combination of consecutive marks and spaces, the 2T detector 6 selects the 2T intersection level when either length is 2T, and the standard intersection level when both are 3T or more. Select as intersection level. The selected value is the intersection level at the intersection level pre- and post-point detector 10, and the pre- and post-points when the equalized waveform of the output of the delay unit 8 crosses the cross level are detected. The edge shift length calculator 11 calculates the edge shift length using the points before and after the intersection level.

  The statistical processor 12 for each mTnT combination discriminates the transition combination of mark and space from mT to nT based on the results of the 2T detector 6, 3T or more T length detector 7, and the edge shift length at that time Get. Then, the edge shift length is statistically processed for each mTnT combination, reflected in the recording strategy adjuster 14, and the recording phase adjustment is performed on the recording data from the recording data generator 13, via the optical head 2. Then, recording on the information recording medium 1 such as an optical disk is performed.

[Operation of Embodiment 1]
FIG. 2 is a flowchart illustrating the recording strategy adjustment operation according to the first embodiment. Data is reproduced from the optical disc by the data reproduction in step S20, the reproduction data is PR equalized by the PR equalization process of step S21, and the PR equalization output signal is viterbi decoded by the Viterbi decoding of step S22. Then, in step S23, it is determined whether any of the consecutive marks or spaces is a combination including 2T. If it is determined as Yes, the 2T intersection level is selected as the intersection level in step S25, and it is determined as No. In step S24, the standard intersection level is selected as the intersection level. After steps S24 and S25, in step S26, the edge shift length is calculated based on the points before and after the intersection level intersects the PR equalization waveform. The PR equalization waveform used in step S26 uses the PR equalization output signal obtained in step S21. In step S27, the rising / falling position of the mark is adjusted based on the edge shift length obtained in step S26. As described above, optimum quality recording is performed.

  Next, in the first embodiment, a method for calculating the edge shift length of the output signal P of the PR equalizer including 2T in the PR equalizer having the constraint length 5 of PR (12221) will be described in more detail. FIG. 13 shows an ideal waveform of the PR equalizer for the S3T and M2T repetitive data strings of PR (12221), where the mark includes a 2T length. FIG. 14 shows an ideal waveform of the PR equalizer for the S2T and M3T repetitive data strings of PR (12221), and is a case where the space includes 2T length. Although both the waveforms in FIGS. 13 and 14 are in contact with zero but do not intersect, the position where they intersect cannot be calculated.

  Therefore, in the present invention, when both the mark length and the space length are 3T or more, the standard intersection level is set as the intersection level. When either the mark length or the space length is 2T, the standard intersection is used. A 2T crossing level different from the level is set as a crossing level. Here, zero is used as the standard intersection level. In particular, when the DC data of the output signal of the PR equalizer is normalized so that the recording data sequence having the same frequency of 0 and 1 becomes 0, both the mark length and the space length are 3T. Since the above PR equalization waveform has amplitudes up and down around 0, it is desirable to set the standard crossing level to zero. However, the present invention is not limited to this, and any value that satisfies the condition that both the mark length and the space length intersect with a PR equalization waveform of 3T or more is acceptable.

  On the other hand, the 2T crossing level is set to −0.125, which is the middle between the points E and F and the middle between the points G and H, for example, in the case of FIG. In the case of FIG. 14 including this, the crossing occurs when the distance is set to 0.125 which is the middle between the points E ′ and F ′ and between the points G ′ and H ′. Here, it is necessary to set different values for the 2T intersection level when the mark length includes 2T and when the space length includes 2T.

  Also, since the PR equalization waveform including 2T changes depending on the PR equalization coefficient, it is desirable to set the 2T intersection according to the set PR equalization coefficient. For example, FIG. 15 shows an ideal waveform of the PR equalizer for the S3T and M2T repetition data strings of PR (23332). In this case, 2T crosses between point I and point J and between point K and point L. It is desirable to set the level. In that case, the optimal 2T crossing level is different from the optimal 2T crossing level −0.125 in FIG. 13.

  In summary, three intersection levels are set: the standard intersection level, the 2T intersection level when 2T is included in the mark length, and the 2T intersection level when 2T is included in the space length. These three values are set in the cross selector of FIG. 1, and the crossing level is switched according to the result of the 2T detector 6. Further, step S25 in the flowchart of FIG. 2 will be described in more detail. When the mark includes 2T, the 2T intersection level when the mark length includes 2T, and when the space includes 2T, the space length is 2T. The 2T crossing level is selected when including.

  Further, the 2T crossing level for each PR equalization coefficient is obtained in advance based on the PR ideal waveform, stored in the crossing level selector 9, and used by referring to the set PR equalization coefficient. .

  Next, the cross-level pre- and post-point detector 10 detects the pre- and post-points where the PR equalization output signal and the cross level cross based on the cross level selected by the cross level selector 9. In FIG. 12, the front and rear points at the rising edge are point A and point B, and the front and rear points at the falling edge are point C and point D. In FIG. 13, the front and rear points at the rising edge are point E and point F, and the front and rear points at the falling edge are point G and point H. In FIG. 14, the front and rear points at the rising edge are point E 'and point F', and the front and rear points at the falling edge are point G 'and point H'.

  Next, calculation of the edge shift length performed by the edge shift length calculator 11 will be described. FIG. 4 is an enlarged view of points A and B in FIG. The corresponding recorded mark positions are shown in the lower part of FIG. Here, the case where the recorded mark is in the proper position is indicated by a solid line, the case where the mark is shifted leftward from the proper position is indicated by a broken line, and the case where the recorded mark is shifted rightward is indicated by a one-dot chain line. Further, the PR equalization waveform when shifted to the left from the proper position is a line segment A′B ′ indicated by a broken line, and the PR equalization waveform when shifted to the right from the proper position is a one-dot chain line A ″ B ″. become.

There are several methods for calculating the edge shift length. The first method is to calculate the coordinates of the intersection between the PR equalization waveform and the intersection level. The coordinates of point A are (XA, YA), the coordinates of point B are (XA + ΔX, YB), the coordinates of point A ′ are (XA, YA ′), the coordinates of point B ′ are (XA + ΔX, YB ′), and point A "(XA, YA"), point B "(XA + ΔX, YB"), line AB intersects the intersection level (XP, 0), and line A'B 'intersects If the point that intersects the level is (XP ′, 0) and the point where the line segment A ″ B ″ intersects the intersection level is (XP ″, 0), first, the line segment AB, A′B ′, A ″ B The inclinations of “” are expressed by the equations (1), (2), and (3), respectively.

m = (YB−YA) / ΔX Formula (1)

m ′ = (YB′−YA ′) / ΔX Formula (2)

m ″ = (YB ″ −YA ″) / ΔX Equation (3)

The coordinates of the positions where the line segments AB, A′B ′, and A ″ B ″ intersect with the intersection level are expressed by Equation (4), Equation (5), and Equation (6), respectively.

XP = XA + ΔX / 2 Formula (4)

XP ′ = XA−YA ′ / m ′ Formula (5)

XP ″ = XA−YA ″ / m ″ Equation (6)

The edge shift length of XP ′ with reference to XP is expressed by equation (7), and the edge shift length of XP ″ with reference to XP is expressed by equation (8).

ES1 ′ = XP′−XP Formula (7)

ES1 ″ = XP ″ −XP Formula (8)

By substituting Equation (4) and Equation (5) into Equation (7), Equation (9) is obtained. Further, Expression (10) is obtained by substituting Expression (4) and Expression (6) into Expression (8).

ES1 ′ = − 1/2 ((YA ′ + YB ′) / (YB′−YA ′))
Formula (9)

ES1 ″ = − 1/2 ((YA ″ + YB ″) / (YB ″ −YA ″))
Formula (10)

Equations (9) and (10) calculate the intersection point of the PR equalizer output signal and the crossing level from the output signal of the PR equalizer before and after the crossing level crosses the PR equalizer output signal. , Represents the edge shift length calculated from the difference between the intersection points of the ideal waveform of the PR equalizer and the intersection level. Here, from FIG. 4, since YA ′ + YB ′> 0 and YA ″ + YB ″ <0, ES1 ′ <0, ES1 ″> 0. In other words, the PR equalized waveform has an amplitude larger than the proper position. When it is above the axis, the rising edge is shifted to the left, the edge shift length is negative, and when the PR equalization waveform is below the appropriate position on the amplitude axis, the rising edge is shifted to the right. The edge shift length is a positive value.

  In FIG. 4, the case where the intersection level is the standard intersection level zero has been described. However, when the intersection level is the 2T intersection level, first, the point A, the point B, the point A ′, the point B ′, the point A ″, the point The intersection level value is subtracted from the Y coordinate of B ″. Thereafter, similarly, the edge shift length may be calculated using Expression (9) and Expression (10).

Next, the second method for calculating the edge shift length will be described with reference to FIG. The second edge shift length is defined by Expression (11), Expression (12), and Expression (13).

ES2 = YB / (YB-YA) Formula (11)

ES2 ′ = YB ′ / (YB′−YA ′) Formula (12)

ES2 ″ = YB ″ / (YB ″ −YA ″) Formula (13)

Here, the Y coordinate of each point in FIG. 4 is YA = −0.25, YB = 0.25, YA ′ = − 0.20, YB ′ = 0.30, YA ″ = − 0.30, YB ″. Substituting as = 0.20, ES2 = 0.5, ES2 ′ = 0.6, ES2 ″ = 0.4. If the rising edge is shifted to the left with respect to the appropriate position, it is appropriate The edge shift length is larger than the position, and when the rising edge is shifted to the right with respect to the proper position, the edge shift length is smaller than the proper position. However, in the case of the 2T intersection level, after subtracting the value of the 2T intersection level from the Y coordinate of each point in advance, the calculation according to the equations (11), (12), and (13) is performed. Good.

Next, the third method for calculating the edge shift length will be described with reference to FIG. The third edge shift length is expressed by Expression (14) and Expression (15).

ES3 ′ = (YA ′ + YB ′) − (YA + YB) Formula (14)

ES3 ″ = (YA ″ + YB ″) − (YA + YB) Formula (15)

Expressions (14) and (15) indicate that the added value of the output signal of the PR equalizer before and after the intersection level of the PR equalizer output signal intersects the ideal waveform of the PR equalizer and the intersection level. The edge shift length is calculated based on the difference between the added values of the ideal waveforms of the PR equalizer before and after. Substituting the Y coordinate of each point in FIG. 4 into Equations (14) and (15) yields ES3 ′ = 0.1 and ES3 ″ = − 0.1. The edge shift length is such that the rising edge is on the left. 4 is a negative value when the rising edge is shifted to the right, and is a positive value when the rising edge is shifted to the right. ) And Expression (15) can be applied as they are.

  As described above, the rising edge in FIG. 4 is considered for the three edge shift lengths, but the same calculation method can be applied to the falling edge.

  Next, examples of PR ideal waveforms for PR equalization coefficients and recording data strings other than those shown in FIGS. 12, 13, 14, and 15 are shown in FIGS. 16, 17, 18, and 19. FIG.

  FIG. 16 shows the S3T and M2T repetitive ideal waveforms of PR (12321). In this case, the mark 2T has a positive amplitude exceeding zero, but if the crossing level is set to the standard crossing level zero, the points before and after the crossing of the ideal waveform are not vertically symmetrical positions, so that the ideal is the same as PR12221 and PR23332. The midpoint of the signal value or a value close to it is more appropriate. Therefore, when a combination of a mark and a space including 2T is detected, it is desirable to set the optimal 2T intersection level for PR (12321) as the intersection level.

  FIG. 17 shows 3T, 2T and 2T repeated ideal waveforms of PR (12221). In PR (12221), if 2T continues as in M2T, S2T or S2T, M2T, the amplitude value of the mark and space becomes zero, and there is no difference because there is no amplitude. The combination of 3T and 2T can be detected by using the 2T intersection level in the combination of 2T and 3T, but the combination of 2T and 2T cannot detect the points before and after the intersection, and the edge shift length cannot be detected. Therefore, in this case, it cannot be adjusted.

  FIG. 18 shows 3T, 2T, and 2T repeated ideal waveforms of PR (23332). In this case, when two 2Ts continue, unlike PR (12221), different amplitudes are indicated by marks and spaces. However, unlike the amplitude of 3T or more, it does not have the amplitude amount of the expected polarity, but in this case, the edge shift length can be calculated by setting the 2T crossing level to zero. In this way, PR (12221) and PR (23332) are handled differently when 2T and 2T are combined, but since this is determined by the PR class, the handling when 2T and 2T are combined depends on the PR equalization coefficient used. What should you do?

  FIG. 19 shows an actual intersection level selection operation example in a combination including 2T and not including 2T. The combination of the space 3T and the mark 3T in (1) and the combination of the mark 3T and the space 3T in (2) do not contain 2T. . Since the combination of the space 3T and the mark 2T in (3) and the combination of the mark 2T and the space 3T in (4) includes 2T, the 2T crossing level is set as the crossing level, and the respective edge shift lengths are obtained from the front and back points. In the case of the mark 2T, the 2T intersection level is a negative value. In the combination of the space 3T and the mark 3T in (5), the standard crossing level zero not including 2T is set as the crossing level, and the edge shift length is obtained from the front and rear points. Since the combination of the mark 3T and the space 2T in (6) and the combination of the space 2T and the mark 3T in (7) include 2T, the 2T crossing level is set as the crossing level, and the respective edge shift lengths are obtained from the front and back points. In the case of the space 2T, the 2T intersection level is a positive value. Thus, the edge shift length can be obtained from the front and rear points by appropriately switching the intersection level depending on whether the combination includes 2T.

  The edge shift lengths thus obtained are classified for each combination of mark and space mT and nT, and statistical processing is performed. That is, the recording data generator 13 repeats recording and reproduction several times with a recording data string composed of a combination of mT and nT of marks and spaces, stores the obtained edge shift length data, and stores the marks and spaces. For each combination of mT and nT, an average, a variance value, and the like are obtained. Here, the dispersion value is used as an evaluation value for evaluating the variation of the edge shift length. Further, although the average edge shift length is used for strategy adjustment, the average length of all data may be used, or any length information can be obtained, and various statistical processing methods can be considered.

  Next, the recording strategy adjuster 13 will be described. FIG. 3 is a diagram for explaining the recording strategy adjustment. FIG. 3 quotes FIG. 22 of Patent Document 4. The recording pulse in the optical head 2 is composed of multi-pulses as shown in FIG. Here, the first pulse width and the last pulse width are adjustable. The rising position of the leading edge of the mark is adjusted by the first pulse width. For example, when the first pulse width is increased, the rising position of the mark leading edge is shifted to the left, and when the first pulse width is decreased, the rising position of the mark leading edge is shifted to the right. On the other hand, the falling position of the trailing edge of the mark is adjusted by the last pulse width. For example, when the last pulse width is widened, the trailing edge of the mark trailing edge shifts to the right, and when the last pulse width is narrowed, the trailing edge of the mark trailing edge shifts to the left.

  In the recording strategy adjuster 13, based on the edge shift length obtained by the statistical processor 12 for each mTnT combination, the rising position of the mark leading edge and the trailing edge of the mark trailing edge for each mTnT combination are made appropriate. The correction amounts of the first pulse width and the last pulse width are obtained, and the correction table shown in FIG. 20 is updated. 20A is a first pulse correction amount table for adjusting the rising position of the leading edge of the mark, and FIG. 20B is the last pulse for adjusting the falling position of the trailing edge of the mark. It is a correction amount table. In the first embodiment, since it is possible to adjust the recording strategy when either one of continuous marks or spaces is 2T, 2T rows and columns are added. When both the continuous mark and the space are 2T, the contrast for calculating the intersection cannot be obtained in the PR output waveform, and the edge shift length cannot be calculated. . However, depending on the recording data string and the PR equalization coefficient, there are cases where detection is possible even with a combination of 2T2T, as shown in FIG. 18. In this case, correction data may be put into the 2T2T combination of the correction table. On the other hand, FIG. 21 is a correction table for conventional recording strategy adjustment. In FIG. 21, which is a correction table of the prior art, when the constraint length of PR (abcba) is 5, the edge shift length including 2T cannot be calculated, so 2T rows and columns are not included in the correction table. Here, FIG. 21 cites FIG. 23 of Patent Document 4. As described above, in the first embodiment, when a PR equalizer having a constraint length of 5 of PR (abcba) is used, even when one of continuous marks and spaces is 2T length, The recording strategy can be adjusted, and an optical information recording / reproducing apparatus capable of optimum recording can be realized.

  Next, the relationship between the edge shift length and the signal quality will be described below. In order to generate an edge shift, a value in the amplitude data of the N-point PR waveform is added or subtracted intentionally when a combination of S3T and S2T is generated. FIG. 5 shows the relationship between the edge shift length and the PRSNR obtained by setting the 2T crossing level to −0.125 for the PR waveform data. PRSNR is a signal evaluation index for PRML, and details are disclosed in Patent Document 3. Here, addition of −3α, −2α, −α, 0, α, 2α, and 3α is performed on the amplitude of the N point. FIG. 5 shows the leading edge shift length and PRSNR of the mark 2T obtained at that time. Here, the leading edge means a rising edge. In addition, the edge shift length uses the third method shown in the equations (14) and (15), and the edge shift length increases in proportion to the added / subtracted amplitude. According to FIG. 5, a waveform having a peak PRSNR is drawn according to the leading edge shift length of the mark 2T. A higher value of PRSNR indicates that the signal quality is better. If the mark 2T leading edge shift length is appropriate, the recording signal quality can be improved. Therefore, based on the result of calculating the edge shift length, if the edge shift length is less than ideal, adjust the recording strategy by an appropriate amount in the increasing direction, and if it is more than ideal, adjust the recording strategy by an appropriate amount in the decreasing direction. It shows that the signal quality can be improved.

  Next, Example 2 will be described. In the second embodiment, the PR ideal waveform generation unit 20 and the 2T intersection level calculation unit 21 in FIG. 6 are further included in the first embodiment in FIG. Here, the PR ideal waveform generation unit 20 outputs a PR ideal waveform based on the recording data sequence generated by the recording data generator 13 and the PR equalization coefficient. FIG. 7 shows the processing contents performed by the PR ideal waveform generation unit 20. FIG. 7 shows a case where the recording data string is S3T and M3T repetition and the PR equalization coefficient is 1221. As shown in FIG. 7, PR ideal waveform (before normalization) data is obtained by performing a convolution operation of the recording data string and the PR equalization coefficient. Next, PR ideal waveform normalization y = ax + b is performed to obtain a PR ideal waveform (after normalization). Calculation of the PR ideal waveform in FIGS. 9 to 19 of the present specification is performed by the method shown in FIG.

  Thereafter, for example, in the case of PR (12221), the 2T intersection level calculation unit 21 automatically calculates an optimal 2T intersection level from the PR ideal waveform of FIG. For example, in the case of FIG. 13, the points F and G in the 2T mark are obtained, then the points E and H adjacent to each other are obtained, and the midpoint between the points E and F or the points G and H The 2T intersection level may be calculated from the midpoint. The two intersection levels 2T calculated by the 2T intersection level calculator 21 in this way are supplied to the intersection level selector 9 as the mark intersection level and 2T as the space intersection level. The second embodiment has an advantage that an optimum 2T intersection level can be automatically calculated and set for a PR equalization coefficient or the like for which an optimum 2T intersection level is not obtained in advance.

  The present invention is used in a recording / reproducing apparatus using a high-density, large-capacity optical recording medium.

  It should be noted that the embodiments and examples can be changed and adjusted within the scope of the entire disclosure (including claims) of the present invention and based on the basic technical concept. Various combinations and selections of various disclosed elements are possible within the scope of the claims of the present invention. That is, the present invention of course includes various variations and modifications that could be made by those skilled in the art according to the entire disclosure including the claims and the technical idea.

DESCRIPTION OF SYMBOLS 1 Information recording medium 2 Optical head 3 A / D converter 4 PR equalizer 5 Viterbi decoder 6 2T detector 7 3T or more T length detector 8 Delay device 9 Cross level selector 10 Cross level front-and-rear point detector 11 Edge Shift length calculator 12 Statistical processor 13 for each mTnT combination Recording data generator 14 Recording strategy adjuster 15 T length detectors 16, 17 Optical information recording / reproducing apparatus 18 PRSNR
19 Mark 2T leading edge shift length 20 PR ideal waveform generator 21 2T crossing level calculator

Claims (14)

An apparatus for recording and reproducing binary data by using marks and spaces on an information recording medium,
A PR equalizer for PR equalizing a signal obtained by reproducing the data of the information recording medium with a constraint length of 5,
A Viterbi decoder that restores binary data by Viterbi decoding the PR equalized signal;
When the length of the continuous mark and space restored by the Viterbi decoder is 3T or more with T as the channel clock period, the predetermined standard crossing level is set as the crossing level, and either length is 2T. A crossing level selector having a 2T crossing level different from the predetermined standard crossing level,
An edge shift length calculator for determining an edge shift length based on a position where an output signal of the PR equalizer crosses the intersection level;
An optical information recording / reproducing apparatus comprising: a recording strategy adjuster that adjusts the rising position of the leading edge of the mark and the falling position of the trailing edge of the mark based on the edge shift length.   2. The 2T intersection level is set to a different value depending on whether the mark length is 2T or the space length is 2T among the continuous marks and spaces. Optical information recording / reproducing apparatus.   3. The optical information recording / reproducing apparatus according to claim 1, wherein the 2T intersection level is set based on a condition capable of intersecting with an ideal waveform of the PR equalizer. 4.   The edge shift length calculator calculates the edge shift length from output signals of the PR equalizer before and after a position where the output level of the PR equalizer and the intersection level intersect. Item 4. The optical information recording / reproducing apparatus according to any one of Items 1 to 3.   In the edge shift length calculator, from the output signal of the PR equalizer before and after the position where the output signal of the PR equalizer intersects the intersection level, the output signal of the PR equalizer and the intersection level An intersection is calculated, and the edge shift length is calculated based on a difference between an output signal of the PR equalizer and the intersection of the intersection level, and an ideal waveform of the PR equalizer and the intersection of the intersection level. The optical information recording / reproducing apparatus according to claim 4. In the edge shift length calculator, the output signal of the PR equalizer and the output signal of the PR equalizer before and after the position where the intersection level intersects are added to obtain a first addition value,
A signal of the ideal waveform of the PR equalizer before and after the position where the ideal waveform of the PR equalizer and the intersection level intersect is added to obtain a second addition value,
5. The optical information recording / reproducing apparatus according to claim 4, wherein the edge shift length is calculated based on a difference between the first addition value and the second addition value.   The edge shift length used in the recording strategy adjuster is calculated by performing average and variance statistical processing for each combination of mark length and space length for the edge shift length calculated by the edge shift length calculator. The optical information recording / reproducing apparatus according to any one of claims 1 to 6. A method for adjusting a recording strategy of an optical information recording / reproducing apparatus for recording and reproducing binary data by using marks and spaces on an information recording medium,
Reproducing data from the information recording medium;
PR equalizing a read signal from the information recording medium with a constraint length of 5;
Viterbi decoding the PR equalized signal in the PR equalizing step to restore the binary data;
Detecting whether any of the continuous mark and space length includes 2T from the restored binary data with T as a channel clock period;
When the lengths of the continuous marks and spaces are both 3T or more, a predetermined standard intersection level is set as the intersection level; and
When either the continuous mark or space length is 2T, a 2T intersection level different from the predetermined standard intersection level is set as the intersection level;
Calculating an edge shift length based on a position at which the PR equalized signal intersects an intersection level;
Adjusting the rising position of the leading edge of the mark or the falling position of the trailing edge of the mark based on the edge shift length;
A recording strategy adjustment method comprising:   The 2T intersection level selected by the intersection level selector is set to a different value depending on whether the mark length is 2T or the space length is 2T among the continuous marks and spaces. The recording strategy adjusting method according to claim 8.   10. The recording strategy adjusting method according to claim 8, wherein the 2T crossing level is set based on a condition capable of crossing the ideal waveform for PR equalization.   The step of calculating the edge shift length calculates the edge shift length from the PR equalized signals before and after the position where the PR equalized signal and the intersection level cross each other. 11. The recording strategy adjustment method according to any one of 10 above.   The step of calculating the edge shift length calculates an intersection between the PR equalized signal and the intersection level from the PR equalized signal before and after the position where the PR equalized signal and the intersection level intersect. 12. The recording strategy adjustment method according to claim 11, wherein the edge shift length is calculated based on a difference between the ideal waveform of the PR equalization and the intersection of the intersection levels. The step of calculating the edge shift length adds the PR equalized signal and the PR equalized signal before and after the position where the intersection level intersects to obtain a first addition value,
Adding the signals of the ideal waveform of PR equalization before and after the position where the ideal waveform of PR equalization and the intersection level intersect to obtain a second addition value;
12. The recording strategy adjustment method according to claim 11, wherein the edge shift length is calculated based on a difference between the first addition value and the second addition value.   The leading edge position of the mark leading edge or the trailing edge of the mark is obtained by performing statistical processing such as averaging and dispersion for each combination of mark length and space length with respect to the edge shift length calculated in the step of calculating the edge shift length. The recording strategy adjustment method according to claim 8, wherein an edge shift length used in the step of adjusting the trailing edge position is calculated.

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