JP2007066412A - Device, method and computer program for evaluating reproducing signal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To evaluate a reproducing signal with high accuracy even when the recording density of a digital signal is increased in an optical disk. <P>SOLUTION: A computer 20 stores amplitude values HSW and LSW and amplitude value reaching periods HST and LST each time a reproducing signal crosses trigger levels TRu and TRd set on a polarity side opposed to an amplitude value to be extracted. The computer 20 also stores amplitude values HLW and LLW and amplitude value reaching periods HLT and LLT corresponding to an evaluation target pulse width 11T each time the reproducing signal crosses slice levels SLu and SLd. Then, frequency distributions are calculated for amplitude values HSW and LSW corresponding to the amplitude value reaching periods HST and LST belonging to a predetermined time range, and extraction amplitude values HSW1 and LSW2 corresponding to an evaluation target pulse width 2T are extracted. Then, the reproducing signal is evaluated by using the extracted amplitude values HSW2 and LSW2 and the stored amplitude values HLW and LLW. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention analog-reproduces a digital signal composed of a series of pulses having a plurality of types of pulse widths recorded on an optical disk such as a Blu-ray disc or HD DVD, and evaluates the reproduced analog reproduction signal. The present invention relates to a reproduction signal evaluation apparatus, a reproduction signal evaluation method, and a reproduction signal evaluation computer program.

  Conventionally, for reproducing analog signals of an optical disc such as a Blu-ray Disc, HD DVD, or the like recorded with a digital signal composed of a series of pulses having a plurality of pulse widths, or the digital signal recorded on the optical disc. In order to inspect a reproducing apparatus such as an optical pickup, it is well known to analog-reproduce a digital signal recorded on an optical disc and evaluate an analog reproduced signal corresponding to a pulse width to be evaluated.

  Evaluation items of this type of analog reproduction signal include modulation amplitude, asymmetry, and the like. The modulation amplitude is evaluated by, for example, a ratio between the amplitude of the signal having the longest pulse width and the amplitude of the signal having the shortest pulse width. Asymmetry is evaluated, for example, by the difference between the center level of the signal having the longest pulse width and the center level of the signal having the shortest pulse width. In the evaluation of such an analog reproduction signal, it is necessary to accurately extract an analog reproduction signal having a pulse width to be evaluated from digital signals sequentially recorded on the optical disk. In the current DVD system, a high-frequency component is emphasized by a waveform equalization circuit (that is, an equalizer) in an analog reproduction signal, and then the signal is binarized by slicing at an appropriate level. According to the width, the analog reproduction signal is classified according to the pulse width.

  However, in recent years, the recording density of optical discs has been improved. Due to this improvement in recording density, there is a problem that the amplitude of a signal with a short pulse width is reduced and interference between adjacently recorded digital signals, that is, intersymbol interference, is increased, and the analog reproduction signal is sliced at an appropriate level. In the binarization method, it is becoming difficult to classify analog reproduction signals by pulse width. This problem becomes more serious as the signal has a shorter pulse width.

In order to solve this problem, for example, in Patent Document 1 below, an analog reproduction signal is decoded into a binary signal by a PRML (Partial Response and Maximum Likelihood) method, and the analog signal is converted into an analog signal based on the pulse width of the decoded binary signal. It is shown that the reproduction signal is classified by pulse width. Further, in Patent Document 1 below, when a signal is recorded on an optical disk by an RLL (Run Length Limited) (1, 7) modulation method, the shortest pulse width is 2T. It is also shown that a binary signal having a pulse width of 3T is used instead of a binary signal having a width of 2T. In other words, the amplitude of the signal corresponding to the pulse width 2T is extremely small, and even if the analog reproduction signal is decoded into the binary signal by the PRML method, the binary signal with the pulse width 2T after decoding has a pulse before reproduction. There is a high possibility that a binarized signal having a width of 3T is included. Therefore, even if the analog reproduction signal is evaluated using a signal corresponding to the pulse width 2T obtained by classifying the analog reproduction signal, a highly accurate evaluation result cannot be obtained. A signal corresponding to the pulse width 3T is used for the evaluation of the analog reproduction signal.
JP 2001-291325 A

  However, the higher the recording density of an optical disc, the smaller the amplitude of a signal with a short pulse width. Therefore, for inspection of a reproducing device such as an optical disc or an optical pickup, the shortest pulse width among analog reproduced signals is reduced. It is important to make an assessment on the amplitude of the corresponding signal. Therefore, it is necessary to classify the signal having the shortest pulse width with high accuracy.

  The present invention has been made to cope with the above-described problems. The purpose of the present invention is to obtain a signal having the shortest pulse width from a signal having another pulse width with high accuracy even if the recording density of the digital signal on the optical disk is improved. An object of the present invention is to provide a reproduction signal evaluation apparatus, a reproduction signal evaluation method, and a reproduction signal evaluation computer program which can classify analog reproduction signals with high accuracy by classification.

  In order to achieve the above object, the present invention is characterized by analog reproduction of a digital signal composed of a series of pulses having a plurality of types of pulse widths recorded on an optical disc and corresponding to the pulse width to be evaluated. In an optical disk reproduction signal evaluation apparatus, a reproduction signal sampling means for sampling an analog reproduction signal at a predetermined sampling rate and A / D converting it into a digital signal, and a digital signal A / D converted by the reproduction signal sampling means A plurality of digital signals representing amplitude values in the analog reproduction signal are extracted and stored as first amplitude values, and a frequency distribution of the first amplitude values stored in the amplitude data storage means is calculated. The amplitude distribution is calculated using the frequency distribution calculation means and the frequency distribution calculated by the frequency distribution calculation means. The amplitude value extracting means for extracting the first amplitude value corresponding to the first pulse width to be evaluated as the extracted amplitude value from the first amplitude value stored in the data storage means, and the amplitude value extracting means There is provided reproduction signal evaluation means for evaluating an analog reproduction signal based on the extracted amplitude value.

  In this case, the reproduction signal evaluation means calculates an analog reproduction signal evaluation parameter value using the extracted amplitude value extracted by the amplitude value extraction means, and the analog reproduction signal is calculated based on the calculated evaluation parameter value. Should be evaluated. In this case, the average value, median value, high frequency value, average value ± standard deviation σ, maximum value or minimum value of the extracted amplitude values may be used as the evaluation parameter value.

  According to the feature of the present invention configured as described above, a plurality of amplitude values in the analog reproduction signal are extracted from the digital signal A / D converted by the reproduction signal sampling means, and a frequency distribution of the plurality of extracted amplitude values is obtained. I'm calculating. In this case, the amplitude of the analog playback signal becomes smaller as the signal length is shorter. Particularly, a signal with a shorter signal length has a different amplitude value depending on the signal length, and therefore, a plurality of extracted amplitude values are classified for each pulse width by the frequency distribution. The As a result, a signal having the shortest pulse width can be classified and extracted from signals having other pulse widths with high accuracy. Since the reproduction signal evaluation means evaluates the analog reproduction signal based on the extracted amplitude value extracted with high precision, the analog reproduction signal obtained by analog reproduction of the digital signal having the shortest pulse width recorded on the optical disk is also evaluated with high accuracy. Thus, even if the recording density of the digital signal on the optical disk is improved, the analog reproduction signal is evaluated with high accuracy.

  Another feature of the present invention is that in the reproduction signal evaluation apparatus, the amplitude data storage means further includes the analog data every time the analog reproduction signal reaches a predetermined first threshold value within the amplitude range of the analog reproduction signal. The amplitude value of the reproduction signal is extracted from the digital signal A / D converted by the reproduction signal sampling means and stored as the first amplitude value. The analog reproduction signal reaches the first threshold value after reaching the first threshold value. And the frequency distribution calculating means stores the first amplitude value corresponding to the amplitude value arrival time representing the time belonging to a predetermined time range. A frequency distribution is calculated every time to generate a plurality of frequency distributions, and the amplitude value extracting means stores the plurality of frequency distributions generated by the frequency distribution calculating means in the amplitude data storage means The first amplitude value corresponding to the first pulse width to be evaluated is extracted from the obtained first amplitude values, and the first amplitude value for each of the extracted frequency distributions is used as the extracted amplitude value. is there.

  According to the feature of the present invention configured as described above, the amplitude data storage means generates the first threshold value every time the analog reproduction signal reaches the first threshold value set within the amplitude range of the analog reproduction signal. And the amplitude value arrival time, which is the time until reaching the amplitude value (first amplitude value) to be extracted, is stored in association with the first amplitude value. Then, a plurality of frequency distributions are calculated for each first amplitude value corresponding to the amplitude value arrival time included in the predetermined time, and the first amplitude values are extracted and extracted for each of the plurality of frequency distributions. One amplitude value is used as the extracted amplitude value. In this case, even if the amplitude value is the same between the pulse widths, the arrival time of the amplitude value to reach the same amplitude value is different for each pulse width. Therefore, the frequency of the first amplitude value is biased for each pulse width in each frequency distribution, and evaluation is performed. Only the first amplitude value corresponding to the target pulse width can be extracted. Then, the first amplitude values extracted every predetermined time are collectively used as the extracted amplitude value. For this reason, even if the first amplitude value extracted from the reproduction signal sampling means is widely distributed for each pulse width, the extracted amplitude value can be obtained with high accuracy by the frequency distribution of the first amplitude value within a predetermined time. Can be extracted. Thereby, an effect similar to the above can be expected.

  In this case, the first threshold value is shifted from the central level of the analog reproduction signal by a predetermined amount to the opposite polarity side to the extracted amplitude value, and the amplitude data storage means is opposite to the first threshold value. The amplitude value on the polarity side may be extracted from the digital signal A / D converted by the reproduction signal sampling means and stored as the first amplitude value. In this case, the center level of the analog reproduction signal may be set to the median value of positive and negative amplitude values in a signal having a long period among the analog reproduction signals. Further, the predetermined amount from the center level of the analog reproduction signal may be half the difference between the maximum amplitude value in the analog reproduction signal and the center level.

  According to this, the first threshold value is set on the side opposite to the amplitude value to be extracted, and the analog reproduction signal amplitude value that has reached the first threshold value is converted from A / D converted digital data. Extracted from. That is, a first threshold value for detecting an analog reproduction signal is provided on the opposite polarity side of each amplitude value. In other words, the first threshold value is opposite to the amplitude value for extracting a predetermined amount from the central level in the analog reproduction signal. The amplitude value of a signal with a small amplitude (specifically, a signal with a short pulse width) is easily detected. Then, the amplitude value of the analog reproduction signal that has reached the first threshold is classified for each pulse width using the frequency distribution. Thereby, an effect similar to the above can be expected.

  In another aspect of the present invention, the amplitude data storage means is further within the amplitude of the analog reproduction signal corresponding to the second pulse width to be evaluated and has the same polarity as the amplitude value to be extracted. A threshold excess time calculating means for measuring the time until the predetermined instantaneous value is reached after the analog reproduction signal crosses the second threshold value as a threshold excess time, and the threshold excess time measured by the threshold excess time calculating means, A threshold excess time determination unit that determines whether or not the second pulse width to be evaluated corresponds to the second pulse width, and the threshold excess time determined by the threshold excess time determination unit is the second pulse to be the evaluation target. When it is determined that it corresponds to the width, the extracted amplitude value is stored as the second amplitude value, and the reproduction signal evaluation means further adds the second amplitude value stored in the amplitude data storage means to perform analog reproduction. signal It lies in the fact that evaluation to.

  In this case, the predetermined instantaneous value in the threshold excess time calculating means may be the amplitude value to be extracted or the second threshold value. Further, the reproduction signal evaluation means calculates an analog reproduction signal evaluation parameter value using the second amplitude value stored in the amplitude data storage means, and the analog reproduction signal is calculated based on the calculated evaluation parameter value. Should be evaluated. In this case, as an evaluation parameter value, an average value, median value, high frequency value, average value ± standard deviation σ, maximum value or minimum value of the second amplitude value may be used.

  According to another feature of the present invention configured as described above, the analog reproduction signal crosses the second threshold having the same polarity as the amplitude value to be extracted, which is the amplitude level corresponding to the second pulse width to be evaluated. The amplitude value corresponding to the second pulse width to be evaluated is extracted from the A / D converted digital data according to the amplitude value to be extracted or the time until the second threshold is reached, that is, the threshold excess time. ing. For this reason, analog reproduction signals that do not reach the second threshold, that is, analog reproduction signals having an amplitude smaller than the amplitude corresponding to the second pulse width to be evaluated are excluded, and the second pulse width to be evaluated is supported. Only the amplitude value of the analog reproduction signal having the amplitude to be extracted can be extracted as the second amplitude value. Thereby, the amplitude value of the analog reproduction signal having the amplitude corresponding to the pulse width to be evaluated can be extracted efficiently, and the analog reproduction signal can be evaluated efficiently. In this case, among the plurality of pulse widths to be evaluated, by associating the second threshold value with the larger amplitude, the analog reproduction signal corresponding to the pulse width with the larger amplitude is evaluated. The amplitude value can be extracted efficiently.

  The present invention can be implemented not only as an apparatus invention but also as a method invention and a computer program invention.

  Hereinafter, an embodiment of a reproduction signal evaluation apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is an overall schematic diagram of an optical disc inspection apparatus for inspecting an optical disc DK such as a Blu-ray Disc and an HD DVD.

  This optical disk inspection apparatus targets the optical disk DK for inspection, and places the optical pickup 12 at a position facing the turntable 11 on which the optical disk DK is mounted and fixed and the optical disk DK mounted and fixed on the turntable 11. I have. The turntable 11 is rotationally controlled by a spindle motor (not shown) so that a light spot formed on the optical disc DK rotates with a constant linear velocity with respect to the optical disc DK. Further, the light spot formed on the optical disk DK moves in the radial direction with respect to the optical disk DK by moving the spindle motor or the optical pickup 12 in the radial direction of the optical disk DK. Move in a spiral.

  The optical pickup 12 reproduces a digital signal recorded on the optical disk DK, and includes a laser light source, a collimating lens, a beam splitter, a quarter wavelength plate, an objective lens, a condensing lens, a cylindrical lens, and a four-divided photo detector. , Focus actuator, tracking actuator and so on. The optical pickup 12 irradiates the optical disk DK with laser light from a laser light source to form a light spot on the optical disk DK, and receives reflected light from the light spot from the optical disk DK with a four-divided photodetector. The light spot formed on the optical disc DK is subject to focus servo control by the focus servo control circuit, tracking servo control circuit, focus actuator, and tracking actuator based on the received light signal output from the four-divided photodetector, and tracking servo. Although these servo controls are not directly related to the present invention, a detailed description thereof will be omitted.

  The light reception signal from the quadrant photodetector of the optical pickup 12 is amplified by the amplifier circuit 13 and guided to an analog / digital converter (hereinafter referred to as A / D converter) 15 via the reproduction signal generation circuit 14. The reproduction signal generation circuit 14 generates and outputs a reproduction signal (a so-called SUM signal) obtained by adding up all four received light signals from the four-divided photodetector. The reproduction signal output from the reproduction signal generation circuit 14 corresponds to the analog reproduction signal of the present invention, and this reproduction signal represents a digital signal recorded on the optical disc DK. For example, in the case of an RLL (2, 11) modulated signal, this digital signal includes nine types of binarized signals each having a pulse width of 2T to 11T.

  The A / D converter 15 samples and holds the reproduction signal from the reproduction signal generation circuit 14 every time the clock signal is input from the clock signal generation circuit 16, and A / D converts the instantaneous value of the reproduction signal sampled and held. In addition, a digital signal representing the same instantaneous value, specifically, waveform data composed of waveform value data representing the voltage value of the reproduction signal at the time of sampling and timing data representing timing at the time of the sampling is output for each cycle of the clock signal. To do. In this embodiment, HD DVD is adopted as the optical disc, and the reference clock frequency (that is, sampling frequency) of HD DVD is 64.8 MHz. Therefore, the frequency of the clock signal from the clock signal generation circuit 14 is HD DVD. However, in this embodiment, it is about 200 MHz. Further, this clock signal is independent of the reference clock of the signal recorded on the optical disc DK.

  The A / D converter 15 is connected to an external storage circuit 17 for storing a digital signal (waveform data) obtained by A / D converting the reproduction signal. The external storage circuit 17 is controlled by the computer 20 to write and read data. In this embodiment, a RAM is used as the external storage circuit 17, but other recording media may be used as long as data can be written and read.

  The computer 20 is constituted by a microcomputer composed of a CPU, ROM, RAM, hard disk, etc., and a reproduction signal evaluation program (shown in FIGS. 4 to 8) shown in FIG. The reproduction signal is evaluated and the optical disc DK is inspected by executing the amplitude data extraction subprogram shown in FIG. 11 and the amplitude value extraction subprogram shown in FIG. In addition, the computer 20 causes the display device 22 such as a CRT (or a liquid crystal display) or a printer to appropriately display the execution process and execution result of the inspection of the optical disc DK. A RAM, a hard disk, and the like built in the computer 20 are provided with a storage area for reading and temporarily storing waveform data stored in the external storage circuit 17. 20a.

  Next, the operation of the embodiment configured as described above will be described. First, the operator starts operation of various circuits of the optical disk inspection apparatus including the computer 20 by turning on a power switch (not shown), and mounts the optical disk DK (HD DVD in this embodiment) to be inspected on the turntable 11. The computer 20 is instructed to inspect the optical disk DK by operating the input device 21 while being fixed. In this case, an inspection signal for the optical disc DK including a series of digital signals having a plurality of types of pulse widths is recorded in advance in a part of the recording area of the optical disc DK to be inspected. Further, in the inspection of the optical disc DK, the reproduction signal corresponding to the shortest pulse width (2T in the present embodiment) and the longest pulse width (11T in the present embodiment) of the inspection signals recorded on the optical disc DK. Using the amplitude values (peak value and bottom value), evaluation items such as modulation amplitude and asymmetry are calculated and the reproduction signal is evaluated to determine whether the optical disc DK is good or bad.

  In response to an instruction to start inspection of the optical disk DK, a light spot is formed on the optical disk DK by the laser light from the optical pickup 12, and a light reception signal by reflected light from the optical spot is reproduced from the optical pickup 12 via the amplifier circuit 13. The signal is output to the signal generation circuit 14. The reproduction signal generation circuit 14 generates a reproduction signal from the received light signal and outputs it to the A / D converter 15. FIG. 2 shows a part of the reproduction signal output from the reproduction signal generation circuit 14. The A / D converter 15 performs A / D conversion on the instantaneous value of the reproduction signal at the cycle of the clock signal from the clock signal generation circuit 16 (a cycle corresponding to about 200 MHz) and repeatedly outputs it to the external storage circuit 17. At this time, the optical spot is spirally rotated at a constant linear velocity relative to the optical disk DK by rotating the turntable 11 and moving the turntable 11 (or optical pickup 12) in the radial direction of the optical disk DK. Move up.

  On the other hand, the computer 20 starts execution of the reproduction signal evaluation program shown in FIG. 3 in step S100, and instructs the external storage circuit 17 to store the waveform data of the reproduction signal in step S102. In the instruction for storing the waveform data of the reproduction signal, storage of a predetermined amount of data (in this embodiment, data corresponding to one rotation of the optical disk DK) is instructed, and the external storage circuit 17 The reproduction signal is A / D converted by the A / D converter 15 to store a predetermined amount of waveform data represented by the digital signal. As described above, the waveform data includes waveform value data representing a voltage value at the time of sampling and timing data representing timing at the time of sampling (a timing representing an elapsed time from a predetermined time).

Next, in step S104, the computer 20 calculates the trigger levels TRu and TRd and the slice levels SLu and SLd using the waveform value data in the series of waveform data stored in the external storage circuit 17. The trigger levels TRu and TRd are levels set for extracting positive and negative amplitude values in the reproduction signal, and correspond to the first threshold value according to the present invention. In the present embodiment, the trigger levels TRu and TRd are calculated by the following equations 1 and 2. In the following formulas 1 and 2, Max represents a positive maximum amplitude value (peak value) among a series of waveform value data stored in the external storage circuit 17, and Min represents a series of waveforms stored in the external storage circuit 17. Of the value data, it represents the negative maximum amplitude value (bottom value), and Ave represents the median value obtained by dividing the sum of Max and Min by 2.
TRu = (Ave + Max) / 2 Formula 1
TRd = (Ave + Min) / 2 Formula 2

  The center level Ave may be a value near the center value of the positive and negative amplitude values of a relatively long period in the series of waveform value data stored in the external storage circuit 17. For example, in this embodiment, the center level Ave is 5T. A value obtained by dividing the positive or negative amplitude value of any one of ˜11T by 2 may be used. Further, the average value of the central levels of the amplitudes of 5T to 11T may be set as the central level Ave.

  That is, the trigger level TRu is set to an intermediate level between Ave and Max, and the trigger level TRd is set to an intermediate level between Ave and Min. In this case, the trigger level TRu is used for extracting a negative amplitude value (bottom value) in the reproduction signal, and the trigger level TRd is used for extracting a positive amplitude value (peak value) in the reproduction signal. In order to extract the positive and negative amplitude values in the reproduction signal, a level for detecting the reproduction signal is provided on the opposite polarity side of each amplitude value. In other words, the level for detecting the reproduction signal is set to be positive or negative in the reproduction signal. The amplitude value of a signal with a small amplitude (specifically, a signal with a short pulse width) is further reduced by lowering (or raising) the amplitude value to a side opposite to the amplitude value extracted by a predetermined amount from the central level Ave of the maximum amplitude value. This is to extract more. Therefore, if the trigger levels TRu and TRd are set to be shifted by a predetermined amount from the central level Ave of the maximum positive and negative amplitude values in the reproduction signal on the opposite polarity sides of the respective amplitude values to be extracted, the above formulas 1 and 2 It is not limited to. In this case, the predetermined amount by which the trigger levels TRu and TRd are shifted is an intermediate level (in the present embodiment) where the trigger levels TRu and TRd are from the central level Ave of the positive and negative maximum amplitude values in the reproduction signal to the positive and negative maximum amplitude values. An amount located in the vicinity of the trigger levels TRu, TRd) is preferred.

The slice levels SLu and SLd are levels set for extracting the amplitude value of the reproduction signal corresponding to the longest pulse width (11T) among the pulse widths to be evaluated. Corresponds to the threshold. In this embodiment, it is calculated by the following formulas 3 and 4. In the following formulas 3 and 4, Max, Min, and Ave are the same as the above formulas 1 and 2.
SLu = Ave + (Max−Ave) × 2/3 Formula 3
SLd = Ave + (Min−Ave) × 2/3 Formula 4

  That is, the slice level SLu is set to a 2/3 level between Ave and Max, and the slice level SLd is set to a 2/3 level between Ave and Min. In this case, the slice level SLu is used for extracting a positive amplitude value in the reproduction signal, and the slice level SLd is used for extracting a negative amplitude value in the reproduction signal. Specifically, the amplitude value of the reproduction signal corresponding to the pulse width to be evaluated is extracted based on the time during which the reproduction signal exceeds the slice levels SLu and SLd. Therefore, if the slice levels SLu and SLd are set within the amplitude range of the reproduction signal corresponding to the pulse width to be evaluated and set to the same polarity side as the amplitude value to be extracted, the slice levels SLu and SLd are limited to the above formulas 3 and 4. Not. Note that the slice levels SLu and SLd are set according to the amplitude of the reproduction signal corresponding to the pulse width to be evaluated, and the pulse width to be evaluated is the longest pulse among the pulse widths as in this embodiment. In the case of the width (11T), the slice levels SLu and SLd are preferably in the vicinity of a level of 2/3 between Ave and Max or Min.

  Next, the computer 20 extracts amplitude data from the series of waveform data stored in the external storage circuit 17 in step S106. The amplitude data includes amplitude values LSW and HSW and amplitude value arrival times LST and HST corresponding to positive and negative amplitude values after the reproduction signal crosses the trigger level TRu or TRd from the outside to the inside, and the reproduction signal It comprises amplitude values HLW and LLW and amplitude value arrival times HLT and LLT corresponding to positive and negative amplitude values after the slice level SLu or SLd is crossed from the inside to the outside. Among these, the amplitude value LSW represents a negative amplitude value (bottom value) immediately after the reproduction signal crosses the trigger level TRu from the upper side to the lower side, and the amplitude value HSW represents the reproduction signal from the lower side of the trigger level TRd. The amplitude value (peak value) on the positive side immediately after crossing to the upper side is shown. The amplitude value arrival time LST represents the time until the reproduction signal crosses the trigger level TRu from the upper side to the lower side to reach the amplitude value LSW. The amplitude value arrival time HST represents the reproduction signal from the lower side of the trigger level TRd. It represents the time taken to cross the upper side and reach the amplitude value HSW.

  The amplitude value HLW represents the positive amplitude value (peak value) immediately after the reproduction signal corresponding to the longest pulse width (11T) of the evaluation target pulse width crosses the slice level SLu from the lower side to the upper side. The amplitude value LLW represents a negative amplitude value (bottom value) immediately after the reproduction signal corresponding to the longest pulse width (11T) crosses the slice level SLd from the upper side to the lower side. The amplitude value arrival time HLT represents the time until the reproduction signal corresponding to the longest pulse width (11T) crosses the slice level SLu from the lower side to the upper side and reaches the amplitude value HLW. The amplitude value arrival time LLT Represents the time until the reproduction signal corresponding to the longest pulse width (11T) crosses the slice level SLd from the upper side to the lower side and reaches the amplitude value LLW. The amplitude values HSW and LSW correspond to the first amplitude value according to the present embodiment, and the amplitude values HLW and LLW correspond to the second amplitude value according to the present embodiment. Further, the amplitude value arrival times HST and LST correspond to the amplitude value arrival times according to the present embodiment. This amplitude data is extracted by the amplitude data extraction subprogram shown in FIGS.

  The amplitude data extraction subprogram starts execution in step S200, and in step S202, detects the change state of the index value S indicating the range to which the amplitude value of the reproduction signal to be detected belongs and the instantaneous value of the reproduction signal. Count value p, e for performing, address n for designating a series of waveform data stored in the external storage circuit 17, variable k for designating the positive amplitude value HSW and amplitude value arrival time HST of the reproduction signal , A variable m for designating the negative amplitude value LSW and amplitude value arrival time LST of the reproduction signal, the positive amplitude value HLW and amplitude of the reproduction signal corresponding to the longest pulse width (11T) to be evaluated In order to designate the negative amplitude value LLW and amplitude value arrival time LLT of the reproduction signal corresponding to the variable v for designating the value arrival time HLT and the longest pulse width (11T). The variable t, is set to "0", respectively.

  Next, the computer 20 increments the address n in step S204, and then in step S206, the computer 20 increments the address value n and n + 1 in the waveform value data in the waveform data stored in the external storage circuit 17 in succession. Two waveform value data are stored in the memory 20a as the first waveform value W1 and the second waveform value W2, respectively. Then, the waveform value data immediately before and after the reproduction signal crosses from the outer side of the trigger level TRu or TRd to the inner side of the trigger level TRu or TRd is detected by the determination processes in steps S208 to S214.

  Specifically, in step S208 and step S210, it is determined whether or not the first waveform value W1 and the second waveform value W2 are each greater than or equal to the trigger level TRu, and the first waveform value W1 is greater than or equal to the trigger level TRu (“ If the second waveform value W2 is less than the trigger level TRu (determined as “No”), the process proceeds to step S216. That is, if the trigger level TRu is crossed from the upper side to the lower side (including the case of contact) while changing from the first waveform value W1 to the second waveform value W2, the process proceeds to step S216. If the first waveform value W1 is less than the trigger level TRu (determined as “No”) in the determination process in step S208, the process proceeds to the determination process in step S212. In the determination process of step S210, when the second waveform value W2 is equal to or higher than the trigger level TRu (determined as “Yes”), that is, when both the first waveform value W1 and the second waveform value W2 are equal to or higher than the trigger level TRu. Return to step S204.

  On the other hand, in step S212 and step S214, it is determined whether or not the first waveform value W1 and the second waveform value W2 are each less than or equal to the trigger level TRd, and the first waveform value W1 is less than or equal to the trigger level TRd (“Yes”). If the second waveform value W2 is greater than the trigger level TRd (determined “No”), the process proceeds to step S216. That is, if the trigger level TRd is crossed from the lower side to the upper side (including the case of contact) while changing from the first waveform value W1 to the second waveform value W2, the process proceeds to step S216. When the first waveform value W1 is greater than the trigger level TRd (determined “No”) in the determination process of step S212, that is, when the first amplitude value W1 is a value between the trigger level TRu and the trigger level TRd. Returns to step S204. If the second waveform value W2 is equal to or lower than the trigger level TRd in the determination process of step S214, that is, if both the first waveform value W1 and the second waveform value W2 are equal to or lower than the trigger level TRd, the process returns to step S204.

  By the cyclic processing in steps S204 to S214, the waveform value data immediately before and after the reproduction signal crosses from the outer side to the inner side of the trigger level TRu or TRd are set as the first waveform value W1 and the second waveform value W2, respectively. Detected. Next, in step S216, two successive timing data designated by addresses n and n + 1 from the timing data in the waveform data stored in the external storage circuit 17 are set as the first timing value T1 and the second timing value T2. Store in the memory 20a. In this case, two continuous timing data designated by addresses n and n + 1 among the timing data are the first waveform value W1 and the first waveform value W1 which are waveform value data immediately before and after the reproduction signal crosses the trigger level TRu or TRd. Timing data corresponding to two waveform values W2.

  Next, after incrementing the address n in Step S218, the computer 20 determines whether or not the second waveform value W2 is smaller than the first waveform value W1 in Step S220, and the second waveform value W2 is determined. If it is smaller than the first waveform value W1, “Yes” is determined in the determination, and the process proceeds to step S300. That is, when the reproduction signal crosses the trigger level TRu from the upper side to the lower side, the process proceeds to step S300. On the other hand, when the second waveform value W2 is larger than the first waveform value W1, it is determined as “No” in the same determination, and the process proceeds to Step S400. That is, when the reproduction signal crosses the trigger level TRd from the lower side to the upper side, the process proceeds to step S400.

  In this case, each process of steps S300 to S386 is a step for extracting and calculating negative amplitude values LSW and LLW and amplitude value arrival times LST and LLT in the waveform data, and each process of steps S400 to S486 is performed. This is a step for extracting and calculating positive amplitude values HSW and HLW and amplitude value arrival times HST and HLT in the waveform data. First, each process of steps S300 to S386 will be described.

In step S300, a timing TRP at which the reproduction signal crosses the trigger level TRu is calculated. Specifically, the waveform value data and timing data specified by the addresses n and n + 1, that is, the first waveform value W1, the second waveform value W2, and the first timing value T1 immediately before and after the reproduction signal crosses the trigger level TRu. , Using the second timing value T2, the calculation is performed by the interpolation calculation of Equation 5 below.
TRP = T1 + (T2−T1) × (TRu−W1) / (W2−W1) Equation 5

  Next, after erasing the first amplitude value W1, the second amplitude value W2, the first timing value T1, and the second timing value T2 from the memory 20a in step S302, the address n in step S304 shown in FIG. Is stored in the memory 20a as the second waveform value W2, and the address n is incremented in step S306.

  Next, in step S308, the computer 20 determines whether or not the next waveform value data of the waveform value data stored as the second waveform value W2 in step S304 exists, and the same waveform value data. As long as exists, the determination is “Yes” and the process proceeds to step S310. In step S310, the waveform value data specified by the address n, that is, the waveform value data next to the waveform value data stored as the second waveform value W2 is stored. In step S312, it is determined whether or not the first waveform value W1 is smaller than the second waveform value W2. If the first waveform value W1 is smaller than the second waveform value W2, “Yes” is determined in the determination. Is determined to proceed to step S313. That is, if the reproduction signal has changed to the negative side, the process proceeds to step S313. On the other hand, if the first waveform value W1 is greater than or equal to the second waveform value, it is determined as “No” in the determination, and the process proceeds to step S334. That is, if the amplitude value of the reproduction signal does not change or changes to the positive side, the process proceeds to step S334. In other words, the determination processing in step S312 detects a negative amplitude value (bottom value) in the reproduction signal.

  First, the case where the negative amplitude value (bottom value) in the reproduction signal is not detected in the determination processing in step S312 (when it is determined “Yes”), that is, the case where the reproduction signal has changed to the negative side will be described. To do. The computer 20 determines whether or not the index value S is “1” or more in step S314 through the process of step S313 described later in detail, and the index value S is “1” or more. If there is, it is determined as “Yes” in the same determination, and step S316 and step S318 are skipped and the process proceeds to step S320. On the other hand, when the value of the index value S is less than “1”, that is, “0”, it is determined as “No” in the same determination, and the process proceeds to step S316. In step S316, it is determined whether or not the first waveform value W1 is equal to or lower than the trigger level TRd. If the first waveform value is equal to or lower than the trigger level TRd, “Yes” is determined in the determination. Proceeding to step S318, the index value S is set to “1” at step S318. On the other hand, if the first waveform value W1 is greater than the trigger level TRd, it is determined as “No” in the determination, and step S318 is skipped and the process proceeds to step S320. That is, the index value S (“1”) indicates that the reproduction signal crosses the trigger level TRd from the upper side to the lower side by the processes of steps S314 to S318.

  Next, in step S320, it is determined whether or not the index value S is “2”. If the index value S is “2”, the determination is “Yes”. Steps S322 to S330 are skipped and the process proceeds to step S332. On the other hand, if the value of the index value S is other than “2”, it is determined as “No” in the same determination, and the process proceeds to step S322. In step S322, it is determined whether or not the first waveform value W1 is equal to or lower than the slice level SLd. If the first waveform value W1 is equal to or lower than the slice level SLd, it is determined as “Yes” in the determination. Proceeding to step S324, "2" is set to index value S at step S324. On the other hand, when the first waveform value W1 is larger than the slice level SLd, it is determined as “No” in the same determination, and steps S324 to S330 are skipped and the process proceeds to step S332. That is, the index value S (“2”) indicates that the reproduction signal crosses the slice level SLd from the upper side to the lower side by the processes of steps S320 to S324.

When it is determined as “Yes” in the determination process of step S322, that is, when the reproduction signal crosses the slice level SLd from the upper side to the lower side, the computer 20 designates the addresses n−1 and n in step S326. Two pieces of continuous timing data, that is, timing data immediately before and after the reproduction signal crosses the slice level SLd are stored in the memory 20a as the second timing value T2 and the third timing value T3, respectively. In step S328, the waveform value data designated by the address n-1, that is, the waveform value data immediately before the reproduction signal crosses the slice level SLd is stored in the memory 20a as the third waveform value W3. Next, in step S330, the computer 20 calculates a timing SLP1 at which the reproduction signal crosses the slice level SLd. Specifically, the waveform value data and timing data specified by the addresses n-1 and n, that is, the third waveform value W3, the first waveform value W1, and the third timing immediately before and after the reproduction signal crosses the slice level SLd. The value T3 and the second timing value T2 are used for calculation by interpolation calculation according to the following equation 6.
SLP1 = T3 + (T2−T3) × (Sld−W3) / (W1−W3) Equation 6

  In step S332, the first waveform value W1 is stored as the second waveform value W2, and the timing data designated by the address n corresponding to the first waveform value W1 and the second waveform value W2 is stored as the first timing. After storing the value T1, the process returns to step S306. That is, in the cyclic processing of steps S306 to S332, the reproduction signal that crosses the trigger level TRu is repeatedly executed until it reaches the negative amplitude value (bottom value), during which the reproduction signal is transmitted to the negative trigger level TRd and Whether or not the slice level SLd is crossed is detected. Then, the waveform value data of the negative maximum amplitude in the reproduction signal is updated and stored as the second waveform value W2, and the timing data corresponding to the waveform value data is updated and stored as the first timing value T1. When the reproduction signal crosses the slice level SLd, the crossing timing SLP1 is calculated.

  Next, when the negative amplitude value (bottom value) in the reproduction signal is detected in the determination processing in step S312 (when it is determined as “No”), that is, the amplitude value of the reproduction signal does not change, or The case where it changes to the positive side is demonstrated. In step S334, the computer 20 determines whether or not the index value S is “1” or more, and the index value S is “1” or more, specifically “1” or “2”. If YES, the determination is “Yes” and the process proceeds to step S342. That is, if the reproduction signal crosses the trigger level TRd or the slice level SLd, the process proceeds to step S342. On the other hand, when the value of the index value S is less than “1”, specifically “0”, it is determined as “No” in the same determination, and the process proceeds to step S336. In step S336, the count value e is set. Increment. That is, if the reproduction signal does not reach the trigger level TRd and the slice level SLd, the process proceeds to step S336.

  Next, in step S338, it is determined whether or not the count value e is greater than “5”. In the same determination, “No” is determined until the count value e is greater than “5”, and the process returns to step S306. When the determination process in step S338 is executed, as described above, the reproduction signal changes to the positive side via the negative amplitude value (bottom value) without crossing the trigger level TRd and the slice level SLd. This is the case. The reason why the processes in steps S306 to S312 are executed five times until the count value e becomes larger than “5” is six reasons after the second waveform value W2, which is the negative amplitude value (bottom value). This is because it is confirmed whether the waveform value data includes waveform value data having an instantaneous value smaller than the second waveform value W2.

  Therefore, when waveform value data having an instantaneous value smaller than the second waveform value W2 is generated while the processes of steps S306 to S312 are performed five times, “Yes” is determined in the determination process of step S312. After the determination and the count value e is reset to “0” in step S313, the execution is shifted to the processing after step S314. On the other hand, if the six waveform value data after the second waveform value W2 does not include waveform value data having an instantaneous value smaller than the second waveform value W2, “Yes” is determined in the determination process of step S338. The determination proceeds to step S340, where the count value e is reset to “0” in step S340. Note that the number of times each process of steps S306 to S312 is executed by the determination process of step S338 is appropriately set according to the state of the reproduction signal, and is not limited to five times.

  If “Yes” is determined in step S334, that is, if the reproduction signal crosses the trigger level TRd or the slice level SLd, in step S342, the first waveform value W1, that is, the negative amplitude value (bottom) It is determined whether the waveform value data next to (value) is greater than the trigger level TRd. In this case, if the first waveform value W1 is greater than the trigger level TRd, it is determined as “Yes” in the same determination, and the process proceeds to step S344. On the other hand, when the first waveform value W1 is equal to or lower than the trigger level TRd, “No” is determined in the determination, and the process returns to step S306. Thereby, it is confirmed whether the waveform value data after the second waveform value W2 includes waveform value data having an instantaneous value smaller than the second waveform value W2. If the waveform value data after the second waveform value W2 is greater than the trigger level TRd, the process proceeds to step S344 assuming that waveform value data having an instantaneous value smaller than the second waveform value W2 is not included.

  In step S344, it is determined whether or not the value of the index value S is “2”. If the value of the index value S is “2”, it is determined as “Yes” in the same determination, and step S358 is performed. Proceed to That is, when the reproduction signal crosses the slice level SLd, the process proceeds to step S358 shown in FIG. The processing after step S358 will be described later. On the other hand, if the value of the index value S is other than “2”, specifically “1”, “No” is determined in the same determination, and the process proceeds to step S346. That is, when the reproduction signal crosses the trigger level TRd, the process proceeds to step S346. Therefore, the processing after step S346 is executed when the reproduction signal changes to the positive side through the negative amplitude value (bottom value) without crossing the trigger level TRd and the slice level SLd. Alternatively, the reproduction signal crosses the trigger level TRd and changes to the positive side via the negative amplitude value (bottom value).

  In step S346, the variable k is incremented. Next, in step S348, the second waveform value W2, that is, the negative amplitude value (bottom value) is stored as the amplitude value LSW (k) specified by the variable k. Also, the time until the reproduction signal crosses the trigger level TRu and reaches the second waveform value W2 is stored as the amplitude value arrival time LST (k) specified by the variable k. In this case, the timing TRP at which the reproduction signal crosses the trigger level TRu is subtracted from the first timing value T1 corresponding to the second waveform value W2. The amplitude value LSW and the amplitude value arrival time LST are stored in the memory 20a.

  Next, in step S350, the computer 20 determines whether or not the index value S is “0”. If the index value S is “0”, the computer 20 determines “Yes” in the determination. Is returned to step S206. That is, when the reproduction signal has changed to the positive side through the negative amplitude value (bottom value) without crossing the trigger level TRd, the process returns to step S206, and the reproduction signal again has the trigger level TRu or TRd. Detection processing of waveform value data immediately before and after crossing from each outer side to each inner side is executed. On the other hand, if the value of the index value S is other than “0”, specifically “1”, it is determined as “No” in the same determination, and the process proceeds to step S352. That is, when the reproduction signal crosses the trigger level TRd, the process proceeds to step S352.

  In step S352, the index value S is reset to “0”. In step S354, the waveform value data specified by the address n-1 is stored as the first waveform value W1, and the waveform value data specified by the address n is stored as the second waveform value W2. That is, the waveform value data specified by the address n−1 in the determination process in step S342 is the waveform value data immediately before the reproduction signal crosses the trigger level TRd, and the waveform value data specified by the address n Is waveform value data immediately after the reproduction signal crosses the trigger level TRd. Next, in step S356, timing data corresponding to the first waveform value W1 and the second waveform value W2, respectively, is stored as the first timing value T1 and the second timing value T2, respectively. Specifically, the timing data specified by the address n−1 is stored as the first timing value, and the timing data specified by the address n is stored as the second timing value.

  In other words, when the determination process of step S350 is “No”, in other words, when the reproduction signal crosses the trigger level TRd, the reproduction signal is triggered by the processes of steps S204 to S214. This is the same as when waveform value data immediately before and after crossing from the lower side to the upper side of level TRd is detected. Therefore, step S352 corresponds to step S202, step S354 corresponds to step 206, and step S356 corresponds to step S216. Then, the computer 20 returns to the determination process of step S220 after the process of step S356, but in the same determination process, the determination is always “No” and the process proceeds to step S400.

  If “Yes” is determined in step S344, that is, if the reproduction signal crosses the slice level SLd, the first waveform value W1, that is, the negative amplitude value (bottom value) is determined in step S358. It is determined whether the next waveform value data of) is smaller than the slice level SLd. In this case, the first waveform value W1 is a value larger than the trigger level TRd by the determination processing in step S342, more specifically, the waveform value immediately after the reproduction signal crosses from the lower side to the upper side of the trigger level TRd. It is data. Therefore, in the determination process of step S358, the determination is “No” until the first waveform value W1 becomes smaller than the slice level SLd, and the processes of steps S360 to S364 are repeatedly executed. Specifically, the address n is decremented in step S360, and the count value p is incremented in step S362. In step S364, the waveform value data specified by the address n is stored as the first waveform value W1, and then the process returns to step S358. That is, the waveform value data immediately before the reproduction signal crosses the slice level SLd is stored as the first waveform value W1 by the cyclic processing in steps S358 to S364. The count value p represents the number of times the address n has been decremented.

  If the first waveform value W1 is waveform value data immediately before crossing the slice level SLd, “Yes” is determined in the determination process of step S358, and the process proceeds to step S366. In step S366, the timing data specified by the address n is stored as the second timing value T2, and the timing data specified by the address n-1 is stored as the third timing value T3. That is, the timing data immediately before the reproduction signal crosses the slice level SLd is stored as the second timing value T2, and the timing data immediately after the reproduction signal crosses the slice level SLd is stored as the third timing value T3. In step S368, the waveform value data designated by the address n + 1, that is, the waveform value data immediately after the reproduction signal crosses the slice level SLd is stored as the third waveform value data W3.

Next, in step S370, the computer 20 calculates a timing SLP2 when the reproduction signal crosses the slice level SLd again after crossing the slice level SLd. Specifically, the waveform value data and timing data specified by the addresses n and n + 1, that is, the first waveform value W1 and the third waveform value immediately before the reproduction signal crosses the slice level SLd from the lower side to the upper side. Calculation is performed by the interpolation calculation by the following equation 7 using W3, the second timing value T2, and the third timing value T3.
SLP2 = T2 + (T3-T2) × (W3-SLd) / (W3-W1) Equation 7

  In step S372, a time WL from when the reproduction signal crosses the slice level SLd from the upper side to the lower side until the slice level SLd crosses the lower side from the lower side again is calculated. Specifically, the timing SLP1 at which the reproduction signal crosses the slice level SLd from the upper side to the lower side is subtracted from the timing SLP2 when the reproduction signal crosses the slice level SLd from the lower side to the upper side. This time WL corresponds to the threshold excess time according to the present embodiment.

  Next, in step S374, the computer 20 determines whether or not the reproduction signal crossing the slice level SLd is a reproduction signal corresponding to the longest pulse width (11T) to be evaluated. Specifically, it is determined whether or not the value of time WL calculated in step S372 is within the range of pulse width (11T−β) ± α, and the value of time WL is determined as pulse width (11T−β). If within the range of ± α, “Yes” is determined in the determination, and the process proceeds to step S376. On the other hand, if the value of time WL is outside the range of pulse width (11T−β) ± α, it is determined as “No” in the same determination, and steps S376 to S378 are skipped and the process proceeds to step S380.

  In this case, the reason why β is subtracted from 11T is that the time from the timing when the signal having the longest pulse width (11T) crosses the central level Ave to the timing when the signal crosses the central level Ave is a value near 11T. Since the slice level SLd is set to a level of 2/3 between the central level Ave and the minimum level Min, the time from the timing when the slice level SLd is crossed to the timing when the slice level SLd is crossed again is shorter than 11T. Become. Therefore, this short amount is reduced from 11T as β. The value of β is measured in advance with a digital oscilloscope or the like, and is a value of about 2.6 T when the optical disc DK is HD DVD (about 2.0 T when it is a Blu-ray disc). ± α is a predetermined allowable range for determining the pulse width 11T. In the present embodiment, whether or not the reproduction signal is a reproduction signal corresponding to the longest pulse width (11T) to be evaluated is determined by the time WL while the reproduction signal exceeds the slice level SLd. It is not limited to. For example, after the reproduction signal crosses the slice level SLd, it may be determined using the time until the negative amplitude value (bottom value) is reached, that is, the amplitude value arrival time LLT.

  In step S376, the variable t is incremented. In step S378, the second waveform value W2, that is, the negative amplitude value (bottom value) is stored as the amplitude value LLW (t) specified by the variable t. Further, the time until the reproduction signal crosses the trigger level TRu and reaches the second waveform value W2 is stored as the amplitude value arrival time LLT (t) specified by the variable t. Specifically, the timing TRP at which the reproduction signal crosses the trigger level TRu is subtracted from the first timing value T1 corresponding to the second waveform value W2. The amplitude value LLW and the amplitude value arrival time LLT are stored in the memory 20a.

  Next, in step S380, the count value p is added to the address n to obtain a new address n. As described above, the count value p is the number of times the address n has been decremented in the circulation process in steps S358 to S364. Therefore, the address n is a value greater than the trigger level TRd determined in the determination process of step S342, more specifically, waveform value data immediately after the reproduction signal crosses from the lower side to the upper side of the trigger level TRd. Next, in step S382, the count value p is cleared to “0”. In step S384, the first waveform value W1, the second waveform value W2, the third waveform value W3, the first timing value T1, the second timing value T2, the third timing value T3, the timings SLP1, SLP2, and the time WL. Then, the process returns to step S352.

  In this case, the address n is an address for designating the waveform value data immediately after the reproduction signal crosses from the lower side to the upper side of the trigger level TRd. Therefore, the reproduction signal is obtained by the processes of steps S204 to S214. This is the same as the case where the waveform value data immediately before and after crossing from the lower side to the upper side of the trigger level TRd is detected. Therefore, the computer 20 executes the processes of steps S352 to S356 in the same manner as described above, and then returns to step S220. However, in the determination process, the determination is always “No” and the process proceeds to step S400.

  If “No” is determined in the determination process of step S220, that is, if the reproduction signal crosses from the lower side to the upper side of the trigger level TRd, the process proceeds to step S400. Each process of steps S400 to S486 is the same as each process of steps S300 to S386. Therefore, steps different from the processes in steps S300 to S386 will be described.

Step S400 corresponds to step S300, and calculates a timing TRP at which the reproduction signal crosses the trigger level TRd. Specifically, it is calculated by an interpolation calculation according to the following equation 8. In the following formula 8, the trigger level TRu in the formula 5 is set as the trigger level TRd.
TRP = T1 + (T2−T1) × (TRd−W1) / (W2−W1) Equation 8

  Next, step S412 shown in FIG. 7 corresponds to step S312, and it is determined whether or not the first waveform value W1 is larger than the second waveform value W2, and the positive amplitude value ( Peak value) is detected. Therefore, the direction of the sign is opposite to that of step 312. Next, Step 416 corresponds to Step S316, determines whether or not the first waveform value W1 is equal to or higher than the trigger level TRu, and indicates whether or not the reproduction signal crosses the trigger level TRu. This is represented by the value of S (“1”). Accordingly, in step S416, the trigger level TRd in step S316 is set as the trigger level TRu.

Next, Step S422 corresponds to Step S322, and determines whether or not the first waveform value W1 is equal to or higher than the slice level SLu, and indicates whether or not the reproduction signal crosses the slice level SLu. This is represented by the value of S (“2”). Therefore, in step S422, the slice level SLd in step S322 is set to the slice level SLu. Next, step S430 corresponds to step S330, and calculates a timing SLP1 at which the reproduction signal crosses the slice level SLu. Specifically, it is calculated by an interpolation calculation according to the following formula 9. In Expression 9, the slice level SLd in Expression 6 is set as the slice level SLu.
SLP1 = T2 + (T2-T3) × (SLu−W3) / (W1−W3) Equation 9

  Next, step S442 corresponds to step S342, and whether or not the first waveform value W1, specifically the waveform value data next to the positive amplitude value (peak value) is smaller than the trigger level TRu. Determine. That is, the waveform value data after the second waveform value W2, which is the positive amplitude value (peak value), has an amplitude larger than the second waveform value W2, in other words, a waveform value with an amplitude value larger than the second waveform value W2. Checks whether data is included. Therefore, in step S442, the direction of the sign in step S342 is reversed, and the trigger level TRd is set to the trigger level TRu. Next, step S448 corresponds to step S348, and the amplitude value specified by the variable m (corresponding to the variable k) is the second waveform value W2 that is the positive amplitude value (peak value). It is stored in the memory 20a as HSW (m). Further, the time until the reproduction signal crosses the trigger level TRd and reaches the second waveform value is stored in the memory 20a as the amplitude value arrival time HST (m) specified by the variable m.

  Next, step S458 shown in FIG. 8 corresponds to step S358, and when it is determined “Yes” in step S444, that is, when the reproduction signal crosses the slice level SLu, the first step S458 is performed. It is determined whether or not the waveform value W1, that is, the waveform value data next to the positive amplitude value (peak value) is smaller than the slice level SLu. In this case, the first waveform value W1 is a value smaller than the trigger level TRu by the determination processing in step S442, more specifically, the waveform value data immediately after the reproduction signal crosses from the upper side to the lower side of the trigger level TRu. It has become. Accordingly, in step S458, the sign direction in step S358 is reversed and the slice level SLd is set to the slice level SLu.

Next, Step S470 corresponds to Step S370, and calculates the timing SLP2 when the reproduction signal crosses the slice level SLu from the lower side to the upper side and then crosses the slice level SLu from the upper side to the lower side again. To do. Specifically, the calculation is performed by an interpolation calculation according to the following equation (10). In Expression 10, the slice level SLd in Expression 7 is set as the slice level SLu. In step S472, a time WL (= SLP2-SLP1) from when the reproduction signal crosses the slice level SLu to when it crosses the slice level SLu again is calculated.
SLP2 = T2 + (T3-T2) × (W3-SLd) / (W3-W1) Equation 10

  Next, step S478 corresponds to step S378, and the amplitude value specified by the variable v (corresponding to the variable t) is the second waveform value W2 which is the positive amplitude value (peak value). Stored as HLW (v) in the memory 20a. Further, the time until the reproduction signal crosses the trigger level TRd and reaches the second waveform value W2 is stored in the memory 20a as the amplitude value arrival time HLT (v) specified by the variable v.

  The case where “No” is determined in the determination process in step S450 and the case where each process in steps S458 to S484 is performed are cases where the reproduction signal crosses the trigger level TRu. This is the same as the case where the waveform value data immediately before and after the reproduction signal crosses from the upper side to the lower side of the trigger level TRu is detected by the processes of S204 to S214. Accordingly, the computer 20 returns to the determination process of step S420 after the process of step S456, but in the determination process, the determination is always “Yes” and the process proceeds to step S300.

  The processes in steps S206 to S220, steps S300 to S384, and steps S440 to S484 are repeatedly executed, and the amplitude values HSW, LSW, HLW, LLW and the amplitude value arrival times LST, HST, HLT, LLT are externally determined. Extracted and calculated from the waveform data of the reproduction signal stored in the storage circuit 17. When the waveform value data in the waveform data of the reproduction signal stored in the external storage circuit 17 no longer exists in the execution processes of steps S206 to S220, steps S300 to S384, and steps S440 to S484, step In the determination process of S308 or S408, it is determined as “No”, the execution of the amplitude data extraction subprogram is terminated in Step S386 or Step S486, and the process returns to Step S108.

  Thereby, the amplitude values HSW (1 to m), LSW (1 to k), HLW (1 to v), LLW (1 to t) and the amplitude value arrival time HST (1) are obtained from the waveform data stored in the external storage circuit 17. ~ M), LST (1 to k), HLT (1 to v), and LLT (1 to t) are extracted and calculated. In this case, the amplitude values HSW (1 to m) and LSW (1 to k) and the amplitude value arrival times HST (1 to m) and LST (1 to k) relate to a reproduction signal in which slice levels SLu and SLd are crossed. The amplitude value and the amplitude value arrival time corresponding to the amplitude value are not included. Also, the amplitude values HLW (1 to v), LLW (1 to t) and the amplitude value arrival times HLT (1 to v) and LLT (1 to t) are evaluated among the reproduction signals crossing the slice levels SLu and SLd. Only the amplitude value related to the target pulse width 11T and the amplitude value arrival time corresponding to the same amplitude value are shown.

  Next, in step S108, the computer 20 calculates the frequency distribution of the amplitude values HSW (1 to m) and LSW (1 to k) extracted in step S106. FIGS. 9A and 9B show the frequency distribution for the amplitude value HSW (1 to m). The frequency distribution of the amplitude value LSW (1 to k) is similar. In FIG. 9A, the frequency peak that appears first from the smaller one of the amplitude values HSW (1 to m) (left side in the figure) is a frequency distribution with a pulse width of 2T, and the frequency peak that appears second is the pulse width. The frequency distribution is 3T, and the third frequency peak appears in the frequency distribution having a pulse width of 4T to 6T. In the frequency distribution of the amplitude value HSW (1 to m) (or LSW (1 to k)), the frequency of the valley portion between the peaks of each frequency does not become “0” in FIG. This is because, as shown in A), the same amplitude value may be obtained between adjacent pulse widths.

  Next, in step S110, the computer 20 calculates the amplitude values HSW (1 to m) and LSW (1 to k) from the amplitude values HSW (1 to m) and LSW (1 to k). Remove noise data. Specifically, as shown in FIG. 9A, the amplitude value HSW (1 to m) (or LSW (1 to k) corresponding to a frequency (broken line in the figure) of 1/10 or less of the maximum frequency in each frequency distribution. )) Is deleted from the memory 20a as noise data. In step S112, in each frequency distribution of the amplitude values HSW (1 to m) and LSW (1 to k), the amplitude value corresponding to the highest frequency of the frequency distribution in the pulse widths 2T and 3T is set to the maximum frequency amplitude value. Extracted as FHSW2, LSW2, HSW3, LSW3. Specifically, the amplitude value corresponding to the peak value of the frequency distribution that appears first from the smaller amplitude value in each frequency distribution of the amplitude values HSW (1 to m) and LSW (1 to k) is the pulse width 2T. The maximum frequency amplitude values FSW2 and FLSW2 are used, and the amplitude value corresponding to the peak value of the frequency distribution that appears second is the maximum frequency amplitude value FHSW3 and FLSW3 of the pulse width 3T.

  Next, in step S114, the computer 20 determines each of positive and negative values corresponding to the pulse width (2T) to be evaluated from the amplitude values HSW (1 to m) and LSW (1 to k) stored in the memory 20a. Extracted amplitude values HSW2 and LSW2 are extracted. In this case, since the extracted amplitude values HSW2 and LSW2 on the positive side and the negative side are extracted in the same manner, the extraction of the positive amplitude value HSW2 will be described. The extracted amplitude values HSW2 and LSW2 correspond to the extracted amplitude values according to the present invention.

  The computer 20 starts the amplitude value extraction subprogram shown in FIG. 11 in step S500, and sets “0” to the variable A in step S502. Next, in step S504, the frequency distribution is calculated using the amplitude value HSW (1 to m) corresponding to the amplitude value arrival time HST (1 to m) belonging to a predetermined time range. In this case, as shown in FIG. 10B, the predetermined time range includes a minimum value Tmin to a maximum value Tmax of the amplitude value arrival time HST (1 to m) corresponding to the pulse width (2T) to be evaluated. This is the time divided for each minute time ΔT, and is expressed by (Tmin + variable A × ΔT) to (Tmin + (variable A + 1) × ΔT). Note that the predetermined time range (Tmin + variable A × ΔT) to (Tmin + (variable A + 1) × ΔT) shown in FIG. 10B is exaggerated for convenience of explanation.

  9B is calculated using the amplitude value HSW (1 to m) in the predetermined time range (Tmin + variable A × ΔT) to (Tmin + (variable A + 1) × ΔT) shown in FIG. 10B. The frequency distribution is shown. That is, the frequency calculated by the amplitude value HST (1 to m) corresponding to the amplitude value arrival time HST (1 to m) belonging to the predetermined time (Tmin + variable A × ΔT) to (Tmin + (variable A + 1) × ΔT) range. According to the distribution, there is no case where the adjacent amplitudes have the same amplitude value as in the frequency distribution shown in FIG. 9A. Therefore, the frequency distribution peaks and pulse widths corresponding to the pulse width 2T are not obtained. The frequency distribution peaks corresponding to 3T can be clearly separated. Thereby, the amplitude value corresponding to the pulse width 2T can be accurately extracted from the amplitude value HSW (1 to m).

  Next, in step S506, the computer 20 calculates a boundary α between the pulse width 2T and the pulse width 3T in the frequency distribution calculated in step S504. Specifically, as shown in FIG. 9B, between the maximum frequency amplitude values FHSW2 and FHSW3 extracted in step S112, the frequency is “0 ± β” in the center of the range. Let the amplitude value be the boundary α. In this case, ± β is an allowable range when the frequency is not completely “0”. As shown in FIG. 9B, when the frequency distribution peak corresponding to the pulse width 2T and the frequency distribution peak corresponding to the pulse width 3T appear clearly, the maximum frequency amplitude values FHSW2, FHSW3 are not necessarily obtained. Is not necessary, but since the number of amplitude values HSW (1 to m) is small in the vicinity of the minimum value Tmin and the maximum value Tmax in the amplitude value arrival time HST (1 to m), the maximum frequency is calculated when calculating the boundary α. It is effective to use the amplitude values FHSW2 and FHSW3. In step S508, the computer 20 extracts and stores the amplitude value HSW (1 to m) equal to or less than the boundary α in the frequency distribution. Thereby, the amplitude value corresponding to the pulse width 2T can be accurately extracted from the amplitude value HSW (1 to m).

  Next, in step S510, it is determined whether or not the predetermined time range (Tmin + variable A × ΔT) to (Tmin + (variable A + 1) × ΔT) has reached the maximum value Tmax of the amplitude value arrival time HST (1 to m). judge. That is, until (Tmin + (variable A + 1) × ΔT) reaches the maximum value Tmax, “No” is continuously determined in the same determination, and the cyclic processing of steps S504 to S510 is repeated through the variable A increment processing in step S512. Executed. As a result, the frequency distribution is calculated for each amplitude value HSW (1 to m) corresponding to the amplitude value arrival time HST (1 to m) belonging to the predetermined time range, and the evaluation target is calculated for each of the plurality of calculated frequency distributions. A plurality of sets of amplitude values HSW (1 to m) corresponding to the pulse width 2T are extracted.

  If (Tmin + (variable A + 1) × ΔT) reaches the maximum value Tmax, “Yes” is determined in the determination process of step S510, and the process proceeds to step S514. In step S514, a plurality of sets of amplitude values HSW (1 to m) corresponding to the pulse width 2T to be evaluated extracted by the circulation process in steps S504 to S510 are set as a set of extracted amplitude values HSW2. That is, the amplitude value HSW (1 to m) extracted by the circulation process in steps S504 to S510 is equal to each frequency distribution for each amplitude value arrival time HST (1 to m) belonging to a predetermined time range. This is aggregate data of amplitude values HSW (1 to m) to be set. Therefore, the set data of the amplitude values HSW (1 to m) of each set is used as a set of set data. In step S516, the computer 20 ends the execution of the amplitude value extraction subprogram and returns to step S116. Note that the negative extracted amplitude value LSW2 corresponding to the pulse width 2T to be evaluated is also extracted by a similar amplitude value extracting subprogram (not shown).

  Next, in step S116, the computer 20 calculates an evaluation parameter value for evaluating the reproduction signal. The evaluation parameter values are the average values of the extracted amplitude values HSW2 and LSW2 corresponding to the pulse width 2T extracted by the execution of the amplitude value extraction subprogram and the pulse width 11T extracted by the execution of the amplitude data extraction subprogram. The average values of the corresponding amplitude values HLW and LLW. Thus, the average value of the positive and negative extracted amplitude values HSW2, LSW2, HLW, and LLW respectively corresponding to the 2T pulse width and the 11T pulse width to be evaluated is calculated as the evaluation parameter value. In addition to the average value, the parameter value for evaluation uses the median value, high frequency value, average value ± standard deviation σ, and maximum value or minimum value of each amplitude value HSW, LSW, HLW, LLW. Also good.

  In step S118, the computer 20 evaluates the reproduction signal using the four evaluation parameter values. Specifically, using the same four evaluation parameter values, each evaluation item such as the modulation amplitude or asymmetry described in the conventional example is calculated to evaluate the reproduction signal, and to determine whether the optical disc DK is good or bad. In this case, the computer 20 displays the evaluation result of the reproduction signal and the quality determination result of the optical disc DK on the display device 22. Further, the computer 20 displays a correlation diagram showing the relationship between the amplitude values HSW and HLW (LSW and LLW) and the amplitude value arrival times HST and HLT (LST and LLT) shown in FIG. Let The amplitude value arrival time HLT (LLT) is data used to display this correlation diagram, and is not the threshold excess time according to the present invention.

  After step S118, the computer 20 ends the reproduction signal evaluation program in step S120. Thereby, the inspection of the optical disk DK is completed. When the inspection of another optical disk DK is executed, the other optical disk DK is placed and fixed on the turntable 11, and the inspection is performed in the same manner.

  As can be understood from the above description of operation, according to the above embodiment, the trigger levels TRu and TRd are set on the opposite polarity side to the amplitude value to be extracted, and the trigger levels TRu and TRd are reached. The amplitude value (peak value or bottom value) of the reproduction signal is extracted from the sampled waveform data. That is, trigger levels TRu and TRd for detecting a reproduction signal are provided on the opposite polarity side of each amplitude value. In other words, the trigger levels TRu and TRd are extracted by a predetermined amount from the center level Ave in the reproduction signal. Is lowered (or raised) to the opposite polarity side to facilitate detection of an amplitude value corresponding to the shortest pulse width (2T) to be evaluated.

  Further, the time (amplitude value arrival time HLT, LLT) until the reproduction signal reaches the trigger level TRu, TRd and reaches the negative amplitude value or the positive amplitude value is stored in correspondence with the amplitude values HSW, LSW. ing. Then, the frequency distribution is calculated for each of the amplitude values HSW and LSW corresponding to the amplitude value arrival times HLT and LLT belonging to a predetermined time range, and is classified for each pulse width. That is, the amplitude values HSW and LSW are classified for each pulse width by time division every predetermined time. In this case, since the amplitude value arrival times HLT and LLT reaching the same amplitude value are different for each pulse width even if the amplitude value is the same between the pulse widths, the frequency of the amplitude values HSW and LSW is different for each pulse width in each frequency distribution. Therefore, only the amplitude values HSW and LSW corresponding to the pulse width 2T to be evaluated can be extracted. For this reason, even when the amplitude values HSW and LSW are widely distributed for each pulse width, the signal having the shortest pulse width due to the frequency distribution of the amplitude values HSW and LSW within a predetermined time is also applied to other pulses. It can be classified with high accuracy from the width signal. As a result, an analog reproduction signal obtained by analog reproduction of a digital signal having the shortest pulse width recorded on the optical disc DK can be accurately evaluated. Even if the recording density of the digital signal on the optical disc is improved, the analog reproduction signal Evaluation is performed with high accuracy.

  The trigger level TRu is determined by the time WL from when the reproduction signal crosses the slice levels SLu and SLd corresponding to the longest pulse width (11T) of the pulse widths to be evaluated until the slice levels SLu and SLd are crossed again. , TRd, the reproduction signal having an amplitude smaller than the amplitude corresponding to the pulse width (11T) to be evaluated is excluded, and the reproduction signal having the amplitude corresponding to the pulse width (11T) to be evaluated is excluded. Only the amplitude values HST and LST are extracted. Thereby, the amplitude value of the amplitude corresponding to the pulse width (11T) to be evaluated can be extracted efficiently, and the reproduction signal can be evaluated efficiently.

  Furthermore, in carrying out the present invention, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the object of the present invention.

  In the above embodiment, the amplitude values (peak value and bottom value) of the reproduction signal corresponding to the longest pulse width (11T) to be evaluated are extracted as the amplitude values HLW and LLW. Instead of the bottom value), the average value of the reproduction signal exceeding the slice levels SLu, SLd can be extracted as the amplitude values HLW, LLW. Specifically, the process indicated by the broken line in FIGS. Among these figures, FIGS. 5 and 6 are flowcharts for extracting the negative amplitude value LLW, and FIGS. 7 and 8 are flowcharts for extracting the positive amplitude value LLW, and the processing contents are the same as each other. Therefore, extraction of the negative amplitude value LLW shown in FIGS. 5 and 6 will be described.

  In step S202 shown in FIG. 4, a process of setting “0” to the variable a is added. Then, in the determination process of step S320 shown in FIG. 5, when it is determined “Yes”, that is, when the reproduction signal has already crossed the slice level SLd, the process returns to step S306. When the reproduction signal first crosses the slice level SLd, the processes of steps S322 to S330 are executed, and then the value of the address n is set to the address x in step S600 instead of step S332. The process returns to step S306. That is, the address where the waveform value data immediately after the reproduction signal crosses the slice level SLd is stored in the address x.

  Next, in the determination process of step S374 shown in FIG. 6, if “Yes” is determined, that is, if the reproduction signal crossing the slice level SLd corresponds to the pulse (11T) to be evaluated, step S376 is performed. Instead of S378, the processes in steps S602 to S618 are executed. In step S602, the value of address n is set to address y. That is, the address where the waveform data immediately before the reproduction signal crosses the slice level SLd is stored is stored in the address y. Next, in step S604, the value of the address x, that is, the address where the waveform value data immediately after the reproduction signal first crosses the slice level SLd is stored is set to the address n. In step S606, the variable a is incremented.

  Next, in step S608, the waveform value data and timing data specified by the address n, that is, the waveform value data and timing data immediately after the reproduction signal first crosses the slice level SLd is used as the waveform value specified by the variable a. Store as PLW (a) and timing PLT (a). In step S610, the address n is incremented. Next, in step S612, it is determined whether or not the address y is equal to or less than the address n, and “No” is continuously determined in the same determination until the address y reaches the address n, and each process of steps S606 to S610 is performed. Is repeatedly executed. That is, waveform value data and timing data in a range exceeding the slice level SLd are stored as the waveform value PLW (a) and the timing PLT (a), respectively. If the waveform value data and timing data in the range exceeding the slice level SLd are stored as the waveform value PLW (a) and the timing PLT (a), it is determined as “Yes” in the same determination, and the step In step S614, the variable t is incremented in step S614.

  Next, in step S616, the average value of the waveform value PLW (a) and the timing PLT (a) in the range exceeding the slice level SLd extracted in steps S606 to S612 is calculated, and the variable t Are stored as the amplitude value LLW (t) and the amplitude value arrival time LLT (t) specified by. In this case, the timing TRP at which the reproduction signal crosses the trigger level TRu is subtracted from the average value of the timing PLT (a). In step S618, “0” is set to the variable a, and then the process proceeds to step S380. Thereby, the average value of the reproduction signal exceeding the slice levels SLu and SLd can be extracted as the amplitude values HLW (1 to t) and LLW (1 to t), and the reproduction signal can be evaluated from various aspects.

  In the above embodiment, the extracted amplitude values HSW2 and LSW2 corresponding to the pulse width 2T to be evaluated are extracted from the amplitude values HSW (1 to m) and LSW (1 to k) extracted by the amplitude data extraction subprogram. Therefore, the frequency distribution of the amplitude values HSW (1 to m) and LSW (1 to k) is calculated by time division using the amplitude value arrival times HST (1 to m) and LST (1 to k). However, it is not always necessary to calculate a time-division frequency distribution. That is, the extracted amplitude values HSW2 and LSW2 corresponding to the pulse width 2T to be evaluated can be extracted using the frequency distribution (FIG. 9A) calculated in step S108 shown in FIG.

  For example, in the frequency distribution shown in FIG. 9A, the first frequency after the first frequency peak appears from the lower one (left side in the figure) of the amplitude value HSW (1 to m) (LSW (1 to m)). The bottom value of the frequency can be set as the boundary α, and the amplitude value equal to or less than the boundary α can be extracted as the extracted amplitude value HSW2 (LSW3) corresponding to the pulse width 2T to be evaluated. Also, the amplitude value at the position of standard deviation ± 2σ (95%) in the frequency distribution of amplitude values below the boundary α can be extracted as the extracted amplitude value HSW2 (LSW2) corresponding to the pulse width 2T to be evaluated. According to this, for example, as shown in FIG. 12, in the adjacent pulse widths, the ranges of the amplitude values HSW and HLW (LSW, LLW) do not overlap with each other or the overlapping range is small (for example, HD This is effective when using a DVD (RW). In these cases, the extracted amplitude value HSW2 (LSW) may be extracted by excluding the amplitude values HSW and LSW corresponding to the frequency equal to or lower than the bottom value of the same frequency.

  Further, for example, in the noise data removal processing in step S110, the frequency level (dotted line in the figure) to be removed as noise data may be increased. Then, from the lower value (left side in the figure) of the amplitude value HSW (1 to m) (or LSW (1 to m)), the frequency “0 ± β” (β is an allowable range) after the frequency peak that appears first. ) Can be extracted as an extracted amplitude value HSW2 (LSW2) corresponding to the pulse width 2T to be evaluated.

  Moreover, in the said embodiment, although the shortest pulse width 2T was used as a pulse width used as evaluation object, the extraction amplitude value HSW3 (LSW3) corresponding to the pulse width of 3T other than this can also be extracted, for example. In this case, for example, in the frequency distribution shown in FIG. 9B, a boundary α ′ is provided at the bottom value of the frequency after the frequency distribution of 3T, and the amplitude value in the range from the boundary α to the boundary α ′ is set as the evaluation target. What is necessary is just to extract as extraction amplitude value HSW3 (LSW3) corresponding to the following pulse width 3T.

  In the above-described embodiment, the amplitude value arrival time HST, LST, HLT, LLT is set to the positive or negative amplitude value (peak) after the reproduction signal crosses the trigger levels TRu, TRd or the slice levels SLu, SLd. Value or bottom value), that is, the time until the amplitude values HSW, LSW, HLW, and LLW to be extracted are calculated. However, the present invention is not limited to this. The amplitude value arrival times HST, LST, HLT, and LLT may be times until the reproduction signal changes to a predetermined amplitude value. For example, after the reproduction signal crosses the trigger levels TRu and TRd, the center level Ave is reached. Alternatively, it may be a time until the trigger levels TRd and TRu on the other polarity side are crossed. Further, the amplitude value arrival times HLT and LLT may be the time until the slice levels SLu and SLd are crossed again after the reproduction signal crosses the slice levels SLu and SLd, that is, the time WL.

  Furthermore, in the above embodiment, the present invention is applied to an optical disk inspection apparatus for inspecting the optical disk DK. However, the present invention is an apparatus for reproducing a signal stored on the optical disk DK and evaluating a reproduction signal. If there is, it is not limited to this. For example, the present invention can be widely applied to an optical pickup inspection apparatus for inspecting a reproducing apparatus such as the optical pickup 20 for analog reproduction of a digital signal recorded on the optical disk DK.

1 is a block diagram schematically showing an entire optical disk inspection apparatus according to an embodiment of the present invention. FIG. 4 is a waveform diagram showing the relationship between a reproduction signal reproduced from an optical disc and a center level, a trigger level, and a slice level. It is a flowchart which shows the reproduction signal evaluation program run by the computer of FIG. It is a flowchart which shows the amplitude data extraction subprogram performed in step S106 of FIG. FIG. 5 is a flowchart showing steps of extracting a negative amplitude value in the amplitude data extraction subprogram shown in FIG. 4. FIG. FIG. 5 is a flowchart showing steps of extracting a negative amplitude value in the amplitude data extraction subprogram shown in FIG. 4. FIG. 5 is a flowchart showing steps for extracting a positive amplitude value in the amplitude data extraction subprogram shown in FIG. 4. 5 is a flowchart showing steps for extracting a positive amplitude value in the amplitude data extraction subprogram shown in FIG. 4. (A) is a frequency distribution diagram of extracted amplitude values, and (B) is a frequency distribution of amplitude values time-divided every predetermined time. (A) is a correlation distribution diagram showing the relationship between the extracted amplitude value and the amplitude value arrival time. (B) is explanatory drawing for demonstrating a mode that the extracted amplitude value is time-divided. It is a flowchart which shows the amplitude data extraction subprogram performed in step S114 of FIG. It is the correlation distribution figure which showed the relationship between the amplitude value by an optical disk different from the optical disk in this embodiment, and an amplitude value arrival time.

Explanation of symbols

DK ... optical disc, 12 ... optical pickup, 14 ... reproduction signal generation circuit, 15 ... A / D converter, 16 ... clock signal generation circuit, 17 ... external storage circuit, 20 ... computer, 20a ... memory, 21 ... input device, 22: Display device.

Claims (27)

In an optical disk reproduction signal evaluation apparatus for analog reproduction of a digital signal composed of a series of pulses having a plurality of types of pulse widths recorded on an optical disk and evaluating an analog reproduction signal corresponding to the pulse width to be evaluated,
Reproduction signal sampling means for sampling the analog reproduction signal at a predetermined sampling rate and A / D converting it into a digital signal;
Amplitude data storage means for extracting a plurality of digital signals representing amplitude values in the analog reproduction signal from the digital signals A / D converted by the reproduction signal sampling means and storing them as first amplitude values;
Frequency distribution calculating means for calculating a frequency distribution of the first amplitude value stored in the amplitude data storage means;
The first amplitude value corresponding to the first pulse width to be evaluated is extracted from the first amplitude values stored in the amplitude data storage means using the frequency distribution calculated by the frequency distribution calculating means. Amplitude value extracting means for extracting as a value;
A reproduction signal evaluation device comprising reproduction signal evaluation means for evaluating the analog reproduction signal based on the extracted amplitude value extracted by the amplitude value extraction means. The reproduction signal evaluation apparatus according to claim 1,
The amplitude data storage means further includes
Each time the analog playback signal reaches a predetermined first threshold within the amplitude range of the analog playback signal, the amplitude value of the analog playback signal is extracted from the digital signal A / D converted by the playback signal sampling means Is stored as the first amplitude value, and the time until the analog reproduction signal reaches the amplitude value after reaching the first threshold value is measured, and the amplitude value arrival time is made to correspond to the first amplitude value. Remember,
The frequency distribution calculating means calculates a frequency distribution for each of the first amplitude values corresponding to the amplitude value arrival time representing a time belonging to a predetermined time range, and generates a plurality of frequency distributions,
The amplitude value extracting means corresponds to the first pulse width to be evaluated from among the first amplitude values stored in the amplitude data storage means for each of a plurality of frequency distributions generated by the frequency distribution calculating means. A reproduction signal evaluation apparatus that extracts the first amplitude value that has been extracted and uses the extracted first amplitude value for each of the plurality of frequency distributions as the extracted amplitude value. In the reproduction signal evaluation apparatus according to claim 2,
The first threshold value is shifted to the opposite polarity side from the amplitude value to be extracted by a predetermined amount from the central level of the analog reproduction signal,
The amplitude data storage means extracts the amplitude value on the side opposite to the first threshold value from the digital signal A / D converted by the reproduction signal sampling means and stores it as a first amplitude value. apparatus. In the reproduction signal evaluation apparatus according to claim 3,
The reproduction signal evaluation apparatus, wherein the central level of the analog reproduction signal is a median value of positive and negative amplitude values in a signal having a long period among the analog reproduction signals. In the reproduction signal evaluation apparatus according to claim 3 or 4,
The reproduction signal evaluation apparatus, wherein the predetermined amount from the central level of the analog reproduction signal is half the difference between the maximum amplitude value in the analog reproduction signal and the central level. In the reproduction signal evaluation apparatus according to any one of claims 1 to 5,
The amplitude data storage means further includes
A second threshold value within the amplitude of the analog reproduction signal corresponding to the second pulse width to be evaluated and having the same polarity as that of the extracted amplitude value is crossed over the analog reproduction signal to a predetermined instantaneous value. An over-threshold time calculating means for measuring the time to reach as the over-threshold time;
Threshold excess time determination means for determining whether or not the threshold excess time measured by the threshold excess time calculation means corresponds to the second pulse width to be evaluated;
When the threshold excess time determination unit determines that the threshold excess time corresponds to the second pulse width to be evaluated, the extracted amplitude value is stored as a second amplitude value,
The reproduction signal evaluation means further evaluates the analog reproduction signal by adding the second amplitude value stored in the amplitude data storage means. In the reproduction signal evaluation apparatus according to claim 6,
The reproduction signal evaluation apparatus, wherein the predetermined instantaneous value in the threshold excess time calculation means is the extracted amplitude value or the second threshold. In the reproduction signal evaluation apparatus according to claim 6 or 7,
The reproduction signal evaluation unit calculates an evaluation parameter value of the analog reproduction signal using the second amplitude value stored in the amplitude data storage unit, and the analog reproduction based on the calculated evaluation parameter value A reproduction signal evaluation device for evaluating a signal. In the reproduction signal evaluation apparatus according to any one of claims 1 to 8,
The reproduction signal evaluation unit calculates an evaluation parameter value of the analog reproduction signal using the extracted amplitude value extracted by the amplitude value extraction unit, and the analog reproduction signal is calculated based on the calculated evaluation parameter value. Reproduction signal evaluation device for evaluating In an optical disk reproduction signal evaluation method for analog reproduction of a digital signal composed of a series of pulses having a plurality of types of pulse widths recorded on an optical disk and evaluating an analog reproduction signal corresponding to the pulse width to be evaluated,
A reproduction signal sampling step of sampling the analog reproduction signal at a predetermined sampling rate and A / D converting it into a digital signal;
An amplitude data storage step for extracting a plurality of digital data representing amplitude values in the analog reproduction signal from the digital signals A / D converted in the reproduction signal sampling step and storing them as first amplitude values;
A frequency distribution calculating step of calculating a frequency distribution of the first amplitude value stored in the amplitude data storing step;
The first amplitude value corresponding to the first pulse width to be evaluated is extracted from the first amplitude values stored in the amplitude data storage step using the frequency distribution calculated in the frequency distribution calculating step. An amplitude value extracting step to extract as a value;
A reproduction signal evaluation method comprising: a reproduction signal evaluation step for evaluating the analog reproduction signal based on the extracted amplitude value extracted by the amplitude value extraction step. The reproduction signal evaluation method according to claim 10,
The amplitude data storing step further includes:
Each time the analog reproduction signal reaches a predetermined first threshold value within the amplitude range of the analog reproduction signal, the amplitude value of the analog reproduction signal is extracted from the digital signal A / D converted in the reproduction signal sampling step. Is stored as the first amplitude value, and the time until the analog reproduction signal reaches the predetermined amplitude value after reaching the first threshold value is measured, and is made to correspond to the first amplitude value as the amplitude value arrival time. Remember,
The frequency distribution calculating step calculates a frequency distribution for each of the first amplitude values corresponding to the amplitude value arrival time representing a time belonging to a predetermined time range, and calculates a plurality of frequency distributions,
The amplitude value extracting step corresponds to the first pulse width to be evaluated from among the first amplitude values stored in the amplitude data storing step for each of a plurality of frequency distributions generated by the frequency distribution calculating step. A reproduction signal evaluation method in which the extracted first amplitude value is extracted, and the extracted first amplitude value for each of the plurality of frequency distributions is extracted. The reproduction signal evaluation method according to claim 11,
The first threshold value is shifted to the opposite polarity side from the amplitude value to be extracted by a predetermined amount from the central level of the analog reproduction signal,
In the amplitude data storing step, the amplitude value on the opposite polarity side to the first threshold value is extracted from the digital signal A / D converted in the reproduction signal sampling step and stored as the first amplitude value Method. The reproduction signal evaluation method according to claim 12,
The method for evaluating a reproduction signal, wherein the central level of the analog reproduction signal is a median value of positive and negative amplitude values in a signal having a long period among the analog reproduction signals. In the reproduction signal evaluation method according to claim 12 or 13,
The reproduction signal evaluation method, wherein the predetermined amount from the central level of the analog reproduction signal is half the difference between the maximum amplitude value in the analog reproduction signal and the central level. In the reproduction signal evaluation method according to any one of claims 10 to 14,
The amplitude data storing step further includes:
A second threshold value within the amplitude of the analog reproduction signal corresponding to the second pulse width to be evaluated and having the same polarity as that of the extracted amplitude value is crossed over the analog reproduction signal to a predetermined instantaneous value. An over-threshold time calculating step for measuring the time to reach as the over-threshold time;
A threshold excess time determination step for determining whether the threshold excess time measured in the threshold excess time calculation step corresponds to the second pulse width to be evaluated;
When it is determined in the threshold excess time determination step that the threshold excess time corresponds to the second pulse width to be evaluated, the extracted amplitude value is stored as a second amplitude value,
The reproduction signal evaluation step further includes adding the second amplitude value stored in the amplitude data storage step to evaluate the analog reproduction signal. The reproduction signal evaluation method according to claim 15,
The reproduction signal evaluation method, wherein the predetermined instantaneous value in the threshold excess time calculation step is the extracted amplitude value or the second threshold value. The reproduction signal evaluation method according to claim 15 or 16,
In the reproduction signal evaluation step, an evaluation parameter value of the analog reproduction signal is calculated using the second amplitude value stored in the amplitude data storage step, and the analog reproduction is calculated based on the calculated evaluation parameter value. A reproduction signal evaluation method for evaluating a signal. The reproduction signal evaluation method according to any one of claims 10 to 17,
In the reproduction signal evaluation step, an evaluation parameter value of the analog reproduction signal is calculated using the extracted amplitude value extracted in the amplitude value extraction step, and the analog reproduction signal is calculated based on the calculated evaluation parameter value. A reproduction signal evaluation method to be evaluated. A reproduction unit for analog reproduction of a digital signal composed of a series of pulses having a plurality of types of pulse widths recorded on an optical disc, a reproduction signal evaluation unit for evaluating an analog reproduction signal corresponding to the pulse width to be evaluated, and a memory device And a computer program that is applied to an optical disk reproduction signal evaluation apparatus that includes a computer unit that executes a computer program, the computer unit including:
The analog reproduction signal reproduced in analog by the reproduction unit is sampled at a predetermined sampling rate and A / D converted into a digital signal,
A plurality of digital signals representing amplitude values in the analog reproduction signal are extracted from the A / D-changed digital signals and stored in the memory device as first amplitude values.
Calculating a frequency distribution of the first amplitude value stored in the memory device;
From the first amplitude value stored in the memory device using the calculated frequency distribution, a first amplitude value corresponding to the first pulse width to be evaluated is extracted as an extracted amplitude value,
A reproduction signal evaluation computer program which causes the reproduction signal evaluation unit to evaluate the analog reproduction signal based on the extracted extracted amplitude value. In the reproduction signal evaluation computer program according to claim 19,
In the computer unit,
Each time the analog reproduction signal reaches a predetermined first threshold value within the amplitude range of the analog reproduction signal, an amplitude value of the analog reproduction signal is extracted from the A / D converted digital signal to obtain a first amplitude value. And the time until the analog reproduction signal reaches the amplitude value after reaching the first threshold value is measured and stored in the memory device as the amplitude value arrival time corresponding to the first amplitude value. ,
Calculating a frequency distribution for each of the first amplitude values corresponding to the amplitude value arrival time representing the time belonging to the predetermined time range to generate a plurality of frequency distributions;
For each of the plurality of generated frequency distributions, a first amplitude value corresponding to the first pulse width to be evaluated is extracted from the first amplitude values stored in the memory device, and the plurality of extracted frequencies A computer program for evaluating a reproduction signal that uses a first amplitude value for each distribution as an extracted amplitude value. In the reproduction signal evaluation computer program according to claim 20,
The first threshold value is shifted to the opposite polarity side from the amplitude value to be extracted by a predetermined amount from the central level of the analog reproduction signal,
In the computer unit,
A reproduction signal evaluation computer program for extracting an amplitude value having a polarity opposite to the first threshold value from the A / D converted digital signal and storing the extracted value as a first amplitude value. In the reproduction signal evaluation computer program according to claim 21,
A computer program for evaluating a reproduction signal, wherein the central level of the analog reproduction signal is a central value of positive and negative amplitude values in a signal having a long period among the analog reproduction signals. The reproduction signal evaluation computer program according to claim 21 or claim 22,
The computer program for evaluating a reproduction signal, wherein the predetermined amount by which the threshold value is shifted from the central level is half the difference between the maximum amplitude value in the analog reproduction signal and the central level. 24. A reproduction signal evaluation computer program according to any one of claims 19 to 23, wherein:
In the computer unit,
A second threshold value within the amplitude of the analog reproduction signal corresponding to the second pulse width to be evaluated and having the same polarity as that of the extracted amplitude value is crossed over the analog reproduction signal to a predetermined instantaneous value. The time to reach is measured as the threshold overtime,
Determining whether the measured threshold excess time corresponds to the second pulse width to be evaluated;
When it is determined that the threshold excess time corresponds to the second pulse width to be evaluated, the extracted amplitude value is stored in the memory device as a second amplitude value;
A computer program for evaluating a reproduction signal, wherein the reproduction signal evaluation unit is also added with the second amplitude value stored in the memory device so as to evaluate the analog reproduction signal. In the reproduction signal evaluation computer program according to claim 24,
The computer program for evaluating a reproduction signal, wherein the predetermined instantaneous value is the amplitude value to be extracted or the second threshold value. In the reproduction signal evaluation computer program according to claim 24 or claim 25,
In the computer unit,
An evaluation parameter value of the analog reproduction signal is calculated using the second amplitude value stored in the memory device, and the reproduction signal evaluation unit is configured to evaluate the analog reproduction signal based on the calculated evaluation parameter value. A computer program for evaluating a reproduced signal. 27. A reproduction signal evaluation computer program according to any one of claims 19 to 26, wherein:
In the computer unit,
A reproduction signal in which an evaluation parameter value of the analog reproduction signal is calculated using the extracted extracted amplitude value, and the reproduction signal evaluation unit evaluates the analog reproduction signal based on the calculated evaluation parameter value Computer program for evaluation.

Images