JP5914645B2 - Waveform equalizer, information reproducing apparatus and method, and computer program - Google Patents

Description

  The present invention relates to a waveform equalizer that performs waveform equalization such as filtering processing on a read signal obtained by reading data recorded on an information recording medium such as an optical disc, an information reproducing apparatus including the waveform equalizer, and information The present invention relates to a reproduction method and a computer program technical field.

  In an information reproducing apparatus equipped with this type of apparatus, for example, asymmetry of a reproduced signal is detected using sample data, or jitter of a reproduced signal is detected using sample data when the polarity of a plurality of sample data changes. Or Here, in particular, the slope of the rising or falling edge of the playback signal is obtained from the sample values before and after the zero cross point, and the sample data corresponding to the zero cross point is normalized to obtain the phase error and phase error absolute value. (See Patent Document 1).

  Limit equalizer as an example of this type of device sets upper and lower limits of amplitude limit value, for example, forcibly suppress variation of sample points before and after the reference sample point, which is the zero cross point, for example, to improve jitter value Has been proposed (see Patent Document 2).

JP 2001-250341 A International Publication No. WO2008 / 053543

  However, the above-described background art has a technical problem that, for example, there is a possibility that the jitter value varies greatly for each information reproducing apparatus or for each measurement.

  The present invention has been made in view of the above-described problems, for example. A waveform equalizer, an information reproducing apparatus and method, and a computer program that can improve the measurement accuracy of a jitter value while suppressing variations between apparatuses. It is an issue to provide.

  In order to solve the above-described problem, the waveform equalizer of the present invention samples an read signal read from a recording medium and acquires a plurality of sample points, and among the acquired plurality of sample points The amplitude values of the plurality of sample points before the zero-cross sample point are close to each other, and the amplitude values of the plurality of sample points after the zero-cross sample point are close to each other. Filtering means for performing a filtering process on the read signal.

  In order to solve the above problems, an information reproducing apparatus of the present invention samples an read signal read from a recording medium and acquires a plurality of sample points, and among the acquired plurality of sample points The amplitude values of the plurality of sample points before the zero-cross sample point are close to each other, and the amplitude values of the plurality of sample points after the zero-cross sample point are close to each other. A waveform equalizer having filtering means for performing a filtering process on the read signal.

  In order to solve the above-described problem, the information reproducing method of the present invention samples a read signal read from a recording medium to acquire a plurality of sample points, and among the acquired plurality of sample points The amplitude values of the plurality of sample points before the zero-cross sample point are close to each other, and the amplitude values of the plurality of sample points after the zero-cross sample point are close to each other. A filtering step of performing a filtering process on the read signal.

  In order to solve the above problems, the computer program of the present invention is a computer installed in an information reproducing apparatus, which samples a read signal read from a recording medium and acquires a plurality of sample points; Among the plurality of acquired sample points, the amplitude values of the plurality of sample points before the zero cross sample point are close to each other, and the amplitude values of the plurality of sample points after the zero cross sample point are It is made to function as a filtering means for performing a filtering process on the read signals so as to approach the same value.

  The effect | action and other gain of this invention are clarified from the form for implementing demonstrated below.

It is a block diagram which shows the structure of the information reproduction apparatus which concerns on 1st Example. It is a block diagram which shows the structure of the variable limit equalizer as an example of the signal amplitude adjustment part which concerns on 1st Example. It is a block diagram which shows the structure of the conversion factor measurement part which concerns on 1st Example. It is a conceptual diagram which shows an example of the signal waveform output from the analog-digital conversion circuit which concerns on 1st Example. It is a conceptual diagram which shows an example of the signal waveform output from the signal amplitude adjustment part which concerns on 1st Example. It is a figure which shows an example of the measured jitter. It is a conceptual diagram which shows an example of the signal waveform output from the analog-digital conversion circuit which concerns on a comparative example. It is a figure which shows an example of the measured jitter which concerns on a comparative example. It is a figure which shows the other example of the measured jitter which concerns on a comparative example. It is a flowchart which shows the jitter measurement process which concerns on 1st Example. It is a figure which shows an example of the determination method of the conversion factor which concerns on the modification of 1st Example. It is a block diagram which shows the structure of the information reproduction apparatus which concerns on 2nd Example. It is a block diagram which shows the structure of the waveform equalizer which concerns on 2nd Example. It is a flowchart which shows the jitter measurement process which concerns on 2nd Example.

  Hereinafter, embodiments according to the waveform equalizer, the information reproducing apparatus, the information reproducing method, and the computer program of the present invention will be described.

(Embodiment of waveform equalizer)
The waveform equalizer according to the embodiment includes an acquisition unit that samples a read signal read from a recording medium to acquire a plurality of sample points, and a plurality of sample points before the zero-cross sample point among the acquired sample points. The read signal is filtered so that the amplitude values of the respective sample points approach the same value, and the amplitude values of the plurality of sample points after the zero-cross sample point approach the same value. Filtering means.

  The reading unit samples a read signal read from a recording medium such as an optical disk, and acquires a plurality of sample points. Note that the reading signal may be sampled by performing A / D (Analog to Digital) conversion on the reading signal, which is an analog signal, for example. Various known modes can be applied to the sampling of the read signal.

  The filtering means is arranged so that the amplitude values of the plurality of sample points before the zero-cross sample point among the plurality of obtained sample points approach the same value, and each of the plurality of sample points after the zero-cross sample point The read signal is subjected to a filtering process so that the amplitude values of the two approaches the same value. The “zero cross sample point” means a point where the level (amplitude value) of the sample point should ideally be zero level.

  According to the inventor's research, the following matters have been found. That is, a plurality of types of data patterns (for example, “2T mark”, “3T mark”, “4T mark”, etc.) having different run lengths are formed on the recording medium. When the jitter value in the time axis direction is measured from the amplitude information of the zero cross sample point, a jitter conversion coefficient is required. Since this jitter conversion coefficient is determined based on, for example, the amplitude values of sample points before and after the zero cross sample point, if no measures are taken, it must be prepared for each of a plurality of types of data patterns. Providing a jitter conversion coefficient for each of a plurality of types of data patterns leads to an increase in circuit scale, and the jitter value may vary depending on the detection accuracy of the data pattern.

  However, in the present embodiment, as described above, the filtering means makes the amplitude values of the plurality of sample points before the zero-cross sample point approach each other, and each of the plurality of sample points after the zero-cross sample point by the filtering unit. The read signal is subjected to a filtering process so that the amplitude values of the read signal approaches the same value. As a result, it is possible to determine a jitter conversion coefficient that can be applied to all of a plurality of types of data patterns. In other words, it is possible to measure jitter values for all of a plurality of types of data patterns using one jitter conversion coefficient. Therefore, if the jitter value is measured using the signal output from the waveform equalizer according to the present embodiment, the measurement accuracy of the jitter value can be improved while suppressing variations between apparatuses.

  In one aspect of the waveform equalizer according to the present embodiment, the filtering unit is configured so that the amplitude values of the plurality of sample points immediately before the zero cross sample point among the plurality of acquired sample points approach the same value. In addition, the filtering process is performed on the read signal so that the amplitude values of the plurality of sample points immediately after the zero-cross sample point are close to the same value.

  According to this aspect, it is possible to determine a jitter conversion coefficient that can be applied to all of a plurality of types of data patterns with ease of comparison.

  In another aspect of the waveform equalizer according to this embodiment, the average value of the amplitude values of each of the plurality of sample points before the zero cross sample point and the average value of the amplitude values of each of the plurality of sample points after the zero cross sample point And calculating means for calculating a conversion coefficient that is a value used when the jitter value related to the read signal is calculated.

  According to this aspect, the conversion coefficient can be calculated relatively easily, which is very advantageous in practice.

  In another aspect of the waveform equalizer according to the present embodiment, a plurality of types of data patterns having different run lengths are formed on the recording medium, and the plurality of sample points before the zero cross sample point are The sample points immediately before the zero-cross sample point for each of the plurality of read signals corresponding to the plurality of types of data patterns, and the plurality of sample points after the zero-cross sample point are a plurality of samples corresponding to the plurality of types of data patterns, respectively. This is the sample point immediately after the zero-cross sample point for each read signal.

  According to this aspect, since it is not necessary to prepare a jitter conversion coefficient for each of a plurality of types of data patterns, it is relatively easy to improve jitter value measurement accuracy while suppressing variations between apparatuses. .

  In another aspect of the waveform equalizer according to the present embodiment, the sample point immediately before the zero cross sample point for the read signal corresponding to the data pattern having the shortest run length among the plurality of types of data patterns, and the shortest run A calculation unit that calculates a conversion coefficient that is a value used when a jitter value related to the read signal is calculated based on a sample point immediately after a zero cross sample point for a read signal corresponding to a data pattern having a length. Is further provided.

  According to this aspect, the conversion coefficient can be calculated relatively easily, which is very advantageous in practice.

  Alternatively, in another aspect of the waveform equalizer according to the present embodiment, a plurality of sample points before a zero cross sample point for a read signal corresponding to a data pattern having a long run length among the plurality of types of data patterns, Based on a plurality of sample points after the zero cross sample point for a read signal corresponding to a data pattern having a long run length, a conversion coefficient that is a value used when a jitter value related to the read signal is calculated A calculation means for calculating is further provided.

  According to this aspect, the conversion coefficient can be calculated relatively easily, which is very advantageous in practice.

(Embodiment of information reproducing apparatus)
An information reproducing apparatus according to an embodiment includes an acquisition unit that samples a read signal read from a recording medium to acquire a plurality of sample points, and a plurality of sample points before the zero-cross sample point among the acquired plurality of sample points. The read signal is filtered so that the amplitude values at the respective sample points approach the same value, and the amplitude values at the plurality of sample points after the zero-cross sample point approach the same value. And a waveform equalizer having filtering means for performing processing.

  According to the information reproducing apparatus according to the present embodiment, it is possible to improve the measurement accuracy of the jitter value while suppressing the variation between apparatuses as in the waveform equalizer according to the present embodiment described above.

  The information reproducing apparatus according to the present embodiment can also adopt various aspects similar to the various aspects according to the waveform equalizer according to the present embodiment.

(Embodiment of information reproduction method)
An information reproducing method according to an embodiment includes an acquisition step of sampling a read signal read from a recording medium to acquire a plurality of sample points, and a plurality of sample points before the zero-cross sample point among the acquired plurality of sample points. The read signal is filtered so that the amplitude values at the respective sample points approach the same value, and the amplitude values at the plurality of sample points after the zero-cross sample point approach the same value. And a filtering step for performing processing.

  According to the information reproducing method according to the present embodiment, it is possible to improve the measurement accuracy of the jitter value while suppressing the variation between the devices as in the waveform equalizer according to the present embodiment described above.

  Note that the information reproduction method according to the present embodiment can also adopt various aspects similar to the various aspects according to the waveform equalizer according to the present embodiment.

(Embodiment of computer program)
The computer program according to the embodiment includes an acquisition unit that acquires a plurality of sample points by sampling a read signal read from a recording medium by a computer installed in the information reproducing apparatus, and the acquired plurality of sample points. Of the plurality of sample points before the zero-cross sample point so that the amplitude values of the plurality of sample points approach the same value, and the amplitude values of the plurality of sample points after the zero-cross sample point approach each other. And a filtering means for performing a filtering process on the read signal.

  According to the computer program according to the present embodiment, information is reproduced from a recording medium such as a CD-ROM (Compact Disc Read Only Memory) or a DVD-ROM (DVD Read Only Memory) that stores the computer program. If the computer provided in the apparatus is read and executed, or if the computer program is executed after being downloaded via the communication means, the information reproducing apparatus according to the present embodiment described above can be made relatively easy. realizable. As a result, as with the information reproducing apparatus according to the present embodiment described above, it is possible to improve the measurement accuracy of the jitter value while suppressing variations between apparatuses.

  Embodiments according to the information reproducing apparatus of the present invention will be described with reference to the drawings.

<First embodiment>
A first embodiment of the information reproducing apparatus of the present invention will be described with reference to FIGS.

  First, the configuration of the information reproducing apparatus according to the present embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of the information reproducing apparatus according to the first embodiment.

  In FIG. 1, an information reproducing apparatus 10 includes an optical pickup (OPU) 11 that can irradiate light to an optical disk 50 such as a Blu-ray Disc, a DVD, and a current-voltage conversion amplifier (I / V) 12. , An analog equalizer 13, an analog-digital converter (A / D) 14, a signal amplitude adjusting unit 15, a conversion coefficient measuring unit 16, and a jitter measuring unit 17.

  For example, a variable limit equalizer as shown in FIG. 2 can be applied to the signal amplitude adjusting unit 15. FIG. 2 is a block diagram showing a configuration of a variable limit equalizer as an example of a signal amplitude adjusting unit according to the first embodiment.

  As shown in FIG. 2, the variable limit equalizer includes a plurality of delay units (D) that add a delay of one clock and a plurality of variable multiplication coefficients (here, “−1.92” and “1.92”). The high-frequency emphasis block having a coefficient multiplier and an adder. The high frequency read sample value output from the high frequency emphasis block is added to the read sample value series input to the adder via a delay unit (3D) that adds a delay of 3 clocks. As a result, the high-frequency emphasized read sample value series is output from the variable limit equalizer.

  As shown in FIG. 3, the conversion factor measurement unit 16 includes a zero-cross sample detection circuit and an averaging circuit. Then, the conversion coefficient measurement unit 16 outputs the conversion coefficient Twa based on the input signal. FIG. 3 is a block diagram illustrating a configuration of the conversion coefficient measurement unit according to the first embodiment.

The zero cross sample detection circuit detects a zero cross sample based on the signal Sa, the signal Sb, and the signal Sc. Specifically, the zero cross sample detection circuit detects the signal Sb as a zero cross sample when all of the following conditions (i) to (iv) are satisfied.
(I) The absolute value of the signal Sa is larger than a predetermined value.
(Ii) The absolute value of the signal Sb is smaller than a predetermined value.
(Iii) The absolute value of the signal Sc is larger than a predetermined value.
(Iv) The sign of the signal Sa is different from the sign of the signal Sc.

  Here, the “predetermined value” is a common value. Such a “predetermined value” may be set, for example, as a value near the half value of the absolute value of the sample value immediately before or after the zero crossing. If zero cross sample detection is performed using a signal before the variable limit equalizer, a desired zero cross sample value can be detected without pattern discrimination. In order to detect a run-length zero cross sample excluding the shortest run length, the “predetermined value” may be set larger than the shortest run-length amplitude sample value and smaller than the shortest run-length + 1T amplitude value.

If two predetermined values (predetermined value 1 and predetermined value 2) are used, only the shortest run-length zero cross sample can be detected. In this case, the conditions (i) to (iv) may be as follows.
(I) 'The absolute value of the signal Sa is larger than the predetermined value 1 and smaller than the predetermined value 2.
(Ii) The absolute value of the signal Sb is smaller than the predetermined value 1.
(Iii) The absolute value of the signal Sc is larger than the predetermined value 1 and smaller than the predetermined value 2.
(Iv) The sign of the signal Sa is different from the sign of the signal Sc.
Here, “predetermined value 1” is, for example, a half value of the shortest run-length amplitude sample value, and “predetermined value 2” is, for example, a value greater than the shortest run-length amplitude sample value and smaller than the shortest run-length + 1T amplitude value. , Can be set as

  The jitter measuring unit 17 measures jitter based on the integrated value of the absolute value of the zero cross sample and the conversion coefficient Twa output from the conversion coefficient measuring unit 16.

  Here, the jitter measurement will be described with reference to FIG. FIG. 7 is a conceptual diagram illustrating an example of a signal waveform output from the analog-digital conversion circuit according to the comparative example.

  In jitter measurement, jitter in the time axis direction (that is, σ / Tw × 100, “Tw” is the clock period, “σ” is the edge of the reproduction signal (the recording data pattern is “0” → “1” or “1” → Standard deviation of fluctuation distribution in the time direction (transient waveform changing to “0”) and jitter in the amplitude axis direction (that is, σ ′ / Tw ′ × 100, “Tw ′” is the window width in the amplitude direction, “σ "" Is required to match the standard deviation of the fluctuation distribution in the amplitude direction of the zero-cross sample value corresponding to the edge of the reproduction signal. This is because the circuit scale becomes relatively large in order to directly make the jitter in the time axis direction.

  The window width Tw ′ (corresponding to the “conversion coefficient Twa” according to the present embodiment) is the amplitude of the sample immediately before the zero cross sample (see “S (n−1)”) and the sample immediately after the zero cross sample (“ S (n + 1) ")). However, as shown in FIG. 7, since the amplitudes of the samples immediately before and after the zero-cross sample vary, it is difficult to uniquely determine the window width Tw ′. That is, it is difficult to indirectly measure the jitter in the time axis direction from the jitter in the amplitude axis direction.

  For this reason, the measured jitter may deviate greatly from the jitter of the standard player as shown in FIG. 8, for example. For example, as shown in FIG. 9, even when a predetermined conversion coefficient is used and the jitter when “Power” is “0%” matches the jitter of the standard player, the accuracy is improved in all regions. It is difficult to measure jitter well.

  Next, the operation of the signal amplitude adjusting unit 15 according to the present embodiment will be specifically described with reference to FIGS. FIG. 4 is a conceptual diagram illustrating an example of a signal waveform output from the analog-digital conversion circuit according to the first embodiment. FIG. 5 is a conceptual diagram illustrating an example of a signal waveform output from the signal amplitude adjustment unit according to the first embodiment.

  As shown in FIG. 4, in the state output from the analog-digital conversion circuit 14, the shortest run length (in this case, “3T”, in the case of Blu-ray Disc, in each of the samples immediately before and after the zero-cross sample, respectively. The amplitude of the sample corresponding to the recording data of “2T”) and the amplitude of the sample corresponding to the recording data other than the shortest run length (for example, 4T, 5T, etc.) are different from each other.

  Therefore, the signal amplitude adjusting unit 15 is configured so that the amplitude of each of the plurality of samples corresponding to all the run-length recording data in the sample immediately before and after the zero-cross sample approaches the same value. Apply high-frequency emphasis filtering. As a result, as shown in FIG. 6, the signal waveform output from the signal amplitude adjusting unit 15 includes a sample immediately before the zero-cross sample (see “S (n−1)”) and a sample immediately after the sample (“S (n + 1)). "See") In each case, the amplitudes of the samples are substantially the same.

  For this reason, if the signal output from the signal amplitude adjustment unit 15 is used, the conversion coefficient Twa (corresponding to “window width Tw” according to the comparative example) can be uniquely determined. Specifically, for example, the conversion factor measurement unit 16 calculates a value that is half the difference between the average value of the amplitude immediately before the zero-cross sample and the average value of the amplitude immediately after the zero-cross sample. It is determined as the conversion coefficient Twa. Alternatively, the conversion factor measurement unit 16 converts the half value of the difference between the amplitude of the sample immediately before the zero cross sample corresponding to the shortest run length recording data and the amplitude of the sample immediately after the zero cross sample. The coefficient is determined as Twa. As a result, for example, as shown in FIG. 6, jitter can be obtained with high accuracy.

  Next, the jitter measurement process in the information reproducing apparatus 10 configured as described above will be described with reference to the flowchart of FIG.

  In FIG. 10, first, the control unit (not shown) of the information reproducing apparatus 10 controls the analog equalizer 13 so that the frequency corresponding to the measurement double speed of the optical disc to be measured becomes the frequency enhancement frequency (step S101). . In parallel with or in parallel with the processing of step S101, the control unit controls the analog equalizer 13 so that the frequency enhancement amount becomes a value during normal reproduction (step S102).

  Next, the control unit refers to the signal output from the signal amplitude adjustment unit 15, the amplitude of the sample immediately before the zero cross sample is substantially the same for all the run lengths, and immediately after the zero cross sample. It is determined whether the amplitudes of the samples are substantially the same (step S103).

  When it is determined that at least one of the amplitude of the sample immediately before the zero-cross sample and the amplitude of the sample immediately after the zero-cross sample is not substantially the same (step S103: No), the control unit controls the frequency related to the signal amplitude adjustment unit 15 The enhancement amount is adjusted (step S104), and the process of step S103 is performed.

  On the other hand, when it is determined that the amplitude of the sample immediately before the zero-cross sample is substantially the same and the amplitude of the sample immediately after the zero-cross sample is substantially the same (step S103: Yes), the control unit The jitter measuring unit 17 is controlled so as to obtain the integrated value of the absolute values (step S105).

  In parallel with the processing in step S105, the control unit 16 calculates the conversion coefficient measurement unit 16 so as to obtain the integrated value of the absolute value of the sample immediately before the zero cross sample and the integrated value of the absolute value of the sample immediately after the zero cross sample. Is controlled (step S106). At this time, the conversion coefficient measurement unit 16 also calculates the conversion coefficient Twa in parallel.

  Next, the control unit determines whether or not the integration of the absolute values of the zero cross samples has been completed (step S107). When it is determined that the integration of the absolute values of the zero cross samples has not ended (step S107: No), the control unit performs the process of step S105.

  On the other hand, when it is determined that the integration of the absolute values of the zero-cross samples has been completed (step S107: Yes), the control unit obtains an average value obtained by dividing the calculated integrated value of the absolute values of the zero-cross samples by the number of integrations. Based on the obtained conversion coefficient Twa, the jitter measuring unit 17 is controlled to calculate jitter (step S108).

  The “signal amplitude adjusting unit 15” and the “conversion coefficient measuring unit 16” according to the present embodiment are examples of the “waveform equalizer” according to the present invention. The “input of the signal amplitude adjusting unit 15”, the “high frequency emphasis block”, and the “conversion coefficient measuring unit 16” according to the present embodiment are respectively “acquisition unit”, “filtering unit”, and “calculation unit” according to the present invention. Is an example.

  The technique according to the present embodiment is not limited to a home information reproducing apparatus, but can be applied to, for example, a business-use jitter measuring apparatus and a jitter measuring method.

<Modification>
Next, a modification of the first embodiment will be described with reference to FIG. FIG. 11 is a diagram illustrating an example of a conversion coefficient determination method according to the modification.

  In this modification, the average value of the absolute values of a plurality of samples before the zero-cross sample corresponding to the recording data of a long run length (for example, “5T”), and the absolute value of the plurality of samples after the zero-cross sample A conversion coefficient Twa is determined based on at least one of the average amplitude values.

  Specifically, the conversion coefficient measuring unit 16 calculates the average value (“Twa_Mark”) of the absolute values of a plurality of samples before the zero cross sample corresponding to 5T recording data, and the plurality of samples after the zero cross sample. The smaller value of the average absolute value amplitudes (“Twa_Space”) is obtained as the conversion coefficient Twa.

<Second embodiment>
Next, a second embodiment according to the information reproducing apparatus of the present invention will be described with reference to FIGS. FIG. 12 is a block diagram showing the configuration of the information reproducing apparatus in the second example. FIG. 13 is a block diagram showing a configuration of a waveform equalizer according to the second embodiment. FIG. 14 is a flowchart showing a jitter measurement process according to the second embodiment.

  First, the configuration of the information reproducing apparatus according to the present embodiment will be described with reference to FIG. As shown in FIG. 12, the information reproducing apparatus 20 according to the present embodiment includes a waveform equalizer 21 instead of the signal amplitude adjusting unit 15 and the conversion coefficient measuring unit 16.

  As shown in FIG. 13, the waveform equalizer 21 includes a plurality of delay units (D) for adding a delay of one clock, a plurality of coefficient multipliers having a multiplication coefficient (here, “a”), an adder, , And a coefficient multiplier (here, a multiplication coefficient “b”). That is, a variable limit equalizer can be applied to the waveform equalizer 21.

  Here, according to the inventor's research, the following matters have been found. That is, when the multiplication coefficient b is fixed (for example, “b = 1”) and the multiplication coefficient a is changed, the DC gain (that is, the signal amplitude related to the recording data corresponding to the long run length) is not changed, and the high The region (that is, the signal amplitude related to the recording data corresponding to the short run length) can be emphasized. On the other hand, if the multiplication coefficients a and b are controlled independently, the amplitude value of the sample immediately before the zero cross sample and the amplitude value of the sample immediately after the zero cross sample can be set to predetermined values.

  For this reason, in the second embodiment, the conversion coefficient Twa is determined in advance, and the signal amplitude is adjusted so as to become the determined conversion coefficient Twa. With this configuration, it is not necessary to provide the conversion coefficient measuring unit 16 (see FIG. 1) for obtaining the conversion coefficient Twa from the signal amplitude, which is very advantageous in practice.

  The jitter measurement processing according to the present embodiment will be specifically described with reference to the flowchart of FIG.

  In FIG. 14, first, the control unit (not shown) of the information reproducing apparatus 20 determines the amplitude value of the sample immediately before the zero cross sample of the recording data corresponding to the long run length and the amplitude value of the sample immediately after the zero cross sample. Then, it is determined whether or not it is substantially equal to a predetermined value (for example, the same value as a predetermined conversion coefficient Twa) (step S201).

  When it is determined that the amplitude value of the sample immediately before the zero cross sample of the recording data corresponding to the long run length and the amplitude value of the sample immediately after the zero cross sample are not substantially the same as the predetermined value (step S201: No). The control unit adjusts the multiplication coefficient b of the waveform equalizer 21 (step S202).

  On the other hand, when it is determined that the amplitude value of the sample immediately before the zero cross sample of the recording data corresponding to the long run length and the amplitude value of the sample immediately after the zero cross sample are substantially the same as the predetermined value (step S201: Yes). The control unit determines whether or not the amplitude of the sample immediately before the zero cross sample is substantially the same and the amplitude of the sample immediately after the zero cross sample is substantially the same for each of the run lengths (see FIG. Step S203).

  When it is determined that at least one of the amplitude of the sample immediately before the zero-cross sample and the amplitude of the sample immediately after the zero-cross sample is not substantially the same (step S203: No), the control unit performs the multiplication coefficient a of the waveform equalizer 21. Is adjusted (step S204).

  On the other hand, when it is determined that the amplitude of the sample immediately before the zero-cross sample is substantially the same and the amplitude of the sample immediately after the zero-cross sample is substantially the same (step S203: Yes), the control unit The jitter measurement unit 17 is controlled so as to obtain the integrated value of the absolute values (step S205).

  Next, the control unit determines whether or not the integration of the absolute values of the zero cross samples has been completed (step S206). When it is determined that the integration of the absolute values of the zero cross samples is not completed (step S206: No), the control unit performs the process of step S205.

  On the other hand, when it is determined that the integration of the absolute values of the zero cross samples has been completed (step S206: Yes), the control unit obtains an average value obtained by dividing the integrated value of the obtained absolute values of the zero cross samples by the number of integrations in advance. Based on the determined conversion coefficient Twa, the jitter measuring unit 17 is controlled to calculate the jitter (step S207).

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit or idea of the invention that can be read from the claims and the entire specification. An information reproducing apparatus and method, and a computer program are also included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 10, 20 ... Information reproduction | regeneration apparatus, 11 ... Optical pick-up, 12 ... Current-voltage conversion amplifier, 13 ... Analog equalizer, 14 ... Analog-digital converter, 15 ... Signal amplitude adjustment part, 16 ... Conversion factor measurement part, 17 ... Jitter measuring unit, 21 ... waveform equalizer, 50 ... optical disc

Claims (8)

An acquisition means for sampling a read signal read from a recording medium and acquiring a plurality of sample points;
Among the plurality of acquired sample points, the amplitude values of the plurality of sample points before the zero-cross sample point are close to each other, and the amplitude values of the plurality of sample points after the zero-cross sample point Filtering means for performing a filtering process on the read signal so that the values approach each other.
Based on the average value of the amplitude values of each of the plurality of sample points before the zero cross sample point and the average value of the amplitude values of each of the plurality of sample points after the zero cross sample point, a jitter value related to the read signal is obtained. A calculation means for calculating a conversion coefficient which is a value used when being calculated;
A waveform equalizer comprising:   The filtering means includes a plurality of samples immediately after the zero-cross sample point so that amplitude values of the plurality of sample points immediately before the zero-cross sample point are close to the same value among the plurality of sample points obtained. The waveform equalizer according to claim 1, wherein the filtering process is performed on the read signal so that the amplitude value of each point approaches the same value. A plurality of types of data patterns having different run lengths are formed on the recording medium,
The plurality of sample points before the zero-cross sample point are sample points immediately before the zero-cross sample point for each of the plurality of read signals respectively corresponding to the plurality of types of data patterns,
The waveform according to claim 1, wherein the plurality of sample points after the zero-cross sample point are sample points immediately after the zero-cross sample point for each of the plurality of read signals respectively corresponding to the plurality of types of data patterns. Equalizer. The calculation means includes a sample point immediately before a zero cross sample point for a read signal corresponding to a data pattern having the shortest run length among the plurality of types of data patterns, and a read corresponding to the data pattern having the shortest run length. a sample point just after the zero cross sampling points for the signal, based on the waveform equalizer according to claim 3, wherein the benzalkonium to calculate the conversion factor. The calculation means includes a plurality of sample points before a zero cross sample point for a read signal corresponding to a data pattern having a long run length among the plurality of types of data patterns, and a reading corresponding to the data pattern having the long run length. a plurality of sample points after the zero cross sampling points for the signal, based on the waveform equalizer according to claim 3, wherein the benzalkonium to calculate the conversion factor. Sampling the read signal read from the recording medium to obtain a plurality of sample points, and among the obtained plurality of sample points, the amplitude values of the plurality of sample points before the zero-cross sample point are mutually to approach the same value, and such that said zero amplitude values of a plurality of sample points each after cross sample point approaches the same value to each other, and filtering means for performing filtering processing on the read signal, the zero-crossing Based on the average value of the amplitude values of each of the plurality of sample points before the sample point and the average value of the amplitude values of each of the plurality of sample points after the zero cross sampling point, a jitter value related to the read signal is calculated. An information reproducing apparatus comprising: a waveform equalizer having calculation means for calculating a conversion coefficient that is a value used when performing the calculation . Sampling the read signal read from the recording medium to obtain a plurality of sample points; and
Among the plurality of acquired sample points, the amplitude values of the plurality of sample points before the zero-cross sample point are close to each other, and the amplitude values of the plurality of sample points after the zero-cross sample point Filtering step of performing a filtering process on the read signal so that they are close to each other,
Based on the average value of the amplitude values of each of the plurality of sample points before the zero cross sample point and the average value of the amplitude values of each of the plurality of sample points after the zero cross sample point, a jitter value related to the read signal is obtained. A calculation step of calculating a conversion coefficient that is a value used when being calculated;
An information reproducing method comprising: A computer mounted on an information playback device
An acquisition means for sampling a read signal read from a recording medium and acquiring a plurality of sample points;
Among the plurality of acquired sample points, the amplitude values of the plurality of sample points before the zero-cross sample point are close to each other, and the amplitude values of the plurality of sample points after the zero-cross sample point Filtering means for performing a filtering process on the read signal so that the values approach each other.
Based on the average value of the amplitude values of each of the plurality of sample points before the zero cross sample point and the average value of the amplitude values of each of the plurality of sample points after the zero cross sample point, a jitter value related to the read signal is obtained. A calculation means for calculating a conversion coefficient which is a value used when being calculated;
A computer program that functions as a computer program.

Images