JP2011044798A - Apparatus and method for processing filter, optical recording medium drive unit, and evaluation value measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an effect equivalent to one to be obtained when a tap coefficient is extended without extending the bit width of the tap coefficient settable in a multiplier in a digital filter. <P>SOLUTION: A target tap coefficient made to be a numeric value in which the number of digits of a lower digit side is larger than that of a settable tap coefficient settable in the multiplier is set. Then, a partial value of settable digits being a numeric value of a part to be the minimum digit or more of the settable tap coefficient and an added numeric value of the minimum digit obtained by adding 1 to the value of the minimum digit with respect to the partial value of settable digits in the target tap coefficient are set in the multiplier such that a setting ratio on the time base thereof is a setting ratio corresponding to a settable numeric value less than the minimum digit being a numeric value of a part to be a digit side lower than the settable digit part in the target tap coefficient. Consequently, an effect equivalent to one to be obtained when a tap coefficient is extended is obtained. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a filter processing apparatus that includes a digital filter and performs filter processing on an input signal, and a method thereof.
The present invention also relates to an optical recording medium driving apparatus that measures a quality evaluation value that is an evaluation index of signal quality based on a reproduction signal from an optical recording medium, and an evaluation value measuring method thereof.

JP 2008-471181 A JP-A-5-55875

A so-called high recording density disc such as a BD (Blu-ray Disc: registered trademark) is widely used as an optical disc recording medium on which a recording signal is reproduced by light irradiation.
For such a high recording density disc, PRML (Partial Response Maximum Likelihood) decoding (partial response maximum likelihood decoding) may be performed in reproducing the recorded information.

As is well known, the PRML decoding method is a method for detecting a partial response sequence that minimizes the Euclidean distance from a reproduction signal, and is a technique in which a process of partial response and a process of maximum likelihood detection are combined.
The partial response sequence is obtained by applying a weighted addition defined by the target response to the bit sequence. In the optical disk system, PR (1, 2, 2, 1) is often used, and this returns a value obtained by adding a weight of 1, 2, 2, 1 to the bit sequence as a partial response value.

In performing PRML decoding, equalization processing (PR equalization processing) is performed on the reproduction signal so that a predetermined PR characteristic is given to the reproduction signal.
In PRML decoding, Viterbi detection is performed as the maximum likelihood detection. In this Viterbi detection, a reproduction signal adjusted so as to become a partial response process by the equalizing process is input, and the reproduction signal and a bit that can be assumed The Euclidean distance between the partial responses of the sequences is examined, and the bit sequence having the closest distance is obtained as a detection result.

  On the other hand, in the optical disk system, a calibration operation relating to recording waveform adjustment parameters such as so-called OPC (Optimum Power Control) and write strategy adjustment is performed during recording.

  Among these calibration operations related to the waveform adjustment parameters, particularly when performing write strategy adjustment, as an evaluation value for evaluating the recording signal quality, for example, dSAM disclosed in the above-mentioned Patent Document 1 etc. An evaluation value representing an error of the edge position is used.

FIG. 8 shows a configuration as a conventional example for obtaining an evaluation value representing an error of an edge position such as the dSAM in an optical disc system that performs PRML decoding corresponding to a high recording density disc such as a BD.
First, an equalizer 100 and a Viterbi decoder 101 are provided as a configuration for realizing the above-described PRML decoding.
The equalizer 100 receives a digitally sampled reproduction signal (hereinafter referred to as a reproduction signal DS) and gives the reproduction signal DS a desired frequency characteristic by an FIR filter 100a (FIR: Finit Impulse Response). The PR equalization process is performed.

The reproduced signal DS (hereinafter referred to as equalized signal yk) that has been equalized by the equalizer 100 is supplied to the Viterbi decoder 101.
The Viterbi decoder 101 performs Viterbi decoding processing (maximum likelihood decoding processing) based on the equalized signal yk to obtain decoded data DT.

Here, the decoded data DT obtained by the Viterbi decoder 101 is also supplied to the equalizer 100. This is because the equalizer 100 performs so-called adaptive equalization processing.
That is, as will be described later, the equalizer 100 in this case is obtained by performing weighted addition based on predetermined PR characteristics such as PR (1, 2, 2, 1), for example, on the decoded data DT (bit series). Equalization processing is performed using a signal waveform (partial response series) as a target waveform.

The equalized signal yk obtained by the equalizer 100 is also supplied to the evaluator 102.
The evaluator 102 measures a quality evaluation value representing an error of the edge position such as dSAM described above based on the equalized signal yk.
Specifically, the evaluator 102 in this case includes an evaluation value measuring unit 102a for each mark length that measures the quality evaluation value for each mark length based on the equalized signal yk, the reproduction clock CK, and the decoded data DT. Further, an averaging unit 102b is provided for averaging the evaluation values measured for each mark length by the evaluation value measuring unit 102a for each mark length.
For confirmation, the measured quality evaluation values are averaged in order to increase the accuracy and stability of the evaluation values.
For confirmation, the decoded data DT is used by the evaluation value measuring unit 102a for each mark length to identify the mark length of the input equalized signal yk.

Here, as described above, the equalizer 100 in this case is supposed to perform adaptive equalization processing. By performing such adaptive equalization processing, the frequency characteristics (and the reproduction signal frequency characteristics of each individual optical disk) Variation in phase characteristics) can be effectively absorbed, and the reproduction signal quality can be improved.
However, when performing a calibration operation such as the write strategy adjustment described above, such adaptive equalization processing may have an adverse effect. Specifically, in write strategy adjustment, for example, trial writing is performed under different recording conditions such as trial writing at different positions on the optical disk while changing recording parameters such as the recording pulse edge position, and those recording portions are recorded. On the basis of the result of obtaining the evaluation value, the optimum recording condition is derived. When such an operation is performed, if an adaptive equalization process is performed, a difference in recording conditions may be absorbed, and as a result, an appropriate adjustment operation may not be performed. There is.

  For this reason, in the conventional optical disk system, an adaptive equalization process in which the tap coefficient is made variable only during normal data reproduction is executed for the equalization process by the equalizer 100, and a fixed tap coefficient is used during the calibration operation. Equalization processing (i.e., tap coefficient invariant equalization processing) is performed.

  At this time, as the fixed tap coefficient set corresponding to the calibration operation, for example, the tap coefficient convergence result of the adaptive equalization process on the optical disc is measured in advance at a plurality of times and the result is obtained. Exceptional value elimination (for example, sorting to eliminate some of the upper and lower values) and averaging, etc., to find the tap coefficient so that the desired partial response equalization is performed and the difference in recording conditions is not absorbed This is to be held on the device side.

FIG. 9 illustrates an internal configuration of the equalizer 100 corresponding to the case where switching between the adaptive equalization process using variable tap coefficients as described above and the equalization process using fixed tap coefficients is performed.
In this figure, the Viterbi decoder 101 shown in FIG. 8 is also shown.

As shown in the figure, within the equalizer 100, the reproduction signal DS is input to the FIR filter 100a. The FIR filter 100a includes a delay circuit 105, a multiplier 106, and an adder 107. In this case, the FIR filter 100a includes two delay circuits 105A and 105B and three multipliers 106-1, 106-2, and 106-3 as shown in the figure, and is an FIR filter with the number of taps = 3. .
In the FIR filter 100a, the addition result by the adder 107 in the figure is supplied to the Viterbi decoder 101 as an equalized signal yk.
The equalized signal yk output from the adder 107 is also supplied to the tap coefficient update processing unit 108.

The tap coefficient update processing unit 108 weights and adds a coefficient based on a predetermined PR characteristic such as (1, 2, 2, 1) to the decoded data DT supplied from the Viterbi decoder 101. Using (partial response series) as a target waveform, an error (that is, an equalization error) between the target waveform and the waveform of the equalized signal yk is calculated, and a tap coefficient that minimizes the error is calculated.
The tap coefficients calculated in this way are the tap coefficient setting units 109-1, 109-2, 109-3 provided corresponding to the multipliers 106-1, 106-2, 106-3, respectively. Supplied against.

The tap coefficient setting units 109-1, 109-2, and 109-3 are provided with selectors 111-1, 111-2, and 111-3, respectively.
These selectors 111-1, 111-2, and 111-3 receive the tap coefficients from the tap coefficient update processing unit 108 and the fixed coefficients 110-1, 110-2, and 110-3. The The fixed coefficients 110-1, 110-2, and 110-3 are fixed tap coefficients obtained in advance as described above.

Each selector 109 is supplied with a reproduction / evaluation value measurement identification signal from the outside. This reproduction / evaluation value measurement identification signal is a signal indicating whether the reproduction state is the normal reproduction state or the evaluation value measurement state accompanying the calibration operation.
Each selector 109 selects and outputs the tap coefficient supplied from the tap coefficient update processing unit 108 when the reproduction / evaluation value measurement identification signal indicates that it is in the normal reproduction state.
On the other hand, when the reproduction / evaluation value measurement identification signal indicates that the evaluation value is being measured, the tap coefficient as the fixed coefficient 110 is selectively output.
As a result, adaptive equalization processing can be performed so as to improve the reproduction signal quality in response to normal reproduction, while equalization processing using a predetermined fixed tap coefficient is performed during evaluation value measurement. By performing the above, it is possible to perform a desired PR equalization and perform a proper calibration operation without absorbing the difference in recording conditions.

For confirmation, the operation corresponding to the calibration realized by the configuration of the conventional example shown in FIGS. 8 and 9 will be described with reference to FIG.
FIG. 10 illustrates a case where test writing is performed for two different recording conditions as recording condition 1 and recording condition 2 along with calibration.
As described above, in the conventional example, since a fixed tap coefficient is set during the calibration operation, the fixed coefficient is set as the tap coefficient setting state under either of the recording conditions 1 and 2 as shown in the figure. The setting state is maintained.

  Further, as is clear from the figure, the evaluator 102 performs an operation of measuring an edge position error for each mark length and averaging the measured edge position error for each mark length under the setting of each recording condition. . Thereby, an evaluation value (average evaluation value) for each mark length can be obtained for each recording condition.

  By the way, in the equalizer 100 shown in FIG. 9, the equalization accuracy (frequency / phase characteristic resolution) to the target characteristic of the equalization process depends on the number of taps of the FIR filter 100a and the number of bits of the tap coefficient (bit width). To be determined. That is, if the number of taps or the number of bits of the tap coefficient is larger, the equalization accuracy to the target characteristic is improved, and conversely if the number is smaller, the equalization accuracy is lowered.

On the other hand, evaluation values representing edge position errors such as dSAM disclosed in Patent Document 1 may be T / 32 or T / 64 (here, in order to improve the adjustment accuracy of recording parameters such as write strategy). And T represents a channel bit).
In order to realize such high error detection accuracy, the equalizer 100 needs to be able to obtain equalization accuracy higher than the equalization accuracy required for data reproduction by PRML decoding. Therefore, it is required to increase the number of taps of the FIR filter 100a and the number of bits of tap coefficients more than necessary for data reproduction.

  However, in a digital filter, an increase in the number of taps and the number of bits of tap coefficients helps increase the cost of the device. In particular, when the number of bits of the tap coefficient is increased, the cost of the digital multiplier circuit as the multiplier 106 is generally increased by considering that the scale of the digital multiplication circuit increases by a power of 2 with respect to the increase in the number of input bits. Will be invited.

  The present invention has been made in view of the above problems, and an effect equivalent to that obtained when the tap coefficient is expanded without expanding the bit width of the tap coefficient that can be set in the multiplier in the digital filter is obtained. The challenge is to make it possible.

In order to solve the above problems, the present invention is configured as follows as a filter processing apparatus.
That is, the filter processing apparatus of the present invention is a filter processing apparatus that includes a digital filter and performs filter processing on an input signal, and includes a multiplier in which tap coefficients are variably set.
In addition, a target tap coefficient holding unit is provided that holds a target tap coefficient that has a number of digits on the lower digit side that is larger than the settable tap coefficient that can be set in the multiplier.
Further, a settable digit partial value that is a numerical value of a portion that is equal to or larger than the minimum digit of the settable tap coefficient in the target tap coefficient, and a minimum obtained by adding 1 to the value of the minimum digit for the settable digit partial value A coefficient alternative setting unit that alternatively outputs one of the digit value added numerical values and sets the value in the multiplier is provided.
Then, the setting ratio on the time axis between the minimum digit value addition value and the settable digit part value for the multiplier is a part on the lower digit side of the settable digit part in the target tap coefficient. A coefficient setting ratio control unit that controls the coefficient selection setting unit so as to obtain a setting ratio corresponding to a numerical value less than the minimum settable digit that is a numerical value of

As described above, in the present invention, the target tap coefficient that is set to a numerical value having more digits on the lower digit side than the settable tap coefficient that can be set in the multiplier constituting the digital filter is held. . For example, if the settable tap coefficient is an integer, the target tap coefficient including a numerical value after the decimal point (having a larger number of bits) is held (set).
Then, in the numerical value as the target tap coefficient, a settable digit partial value that is a numerical value of a portion that is greater than or equal to the minimum digit of the settable tap coefficient, and 1 is set to the value of the minimum digit for the settable digit partial value About the added minimum digit value addition numerical value, one of them can be alternatively output and set in the multiplier. If the numerical value of the target tap coefficient is “1.4”, for example, one of “1” (settable digit partial value) and “2” (minimum digit value addition numerical value) is used as a multiplier. On the other hand, it can be set alternatively.
In addition, the setting ratio on the time axis between the minimum digit value addition value (for example, “2”) and the settable digit partial value (for example, “1”) for the multiplier is set as the value in the target tap coefficient. The setting ratio is set in accordance with the numerical value less than the minimum settable digit, which is the numerical value on the lower digit side of the settable digit portion. For example, when the value obtained by subtracting the settable digit partial value from the target tap coefficient value is X, the setting ratio on the time axis between the minimum digit value added value and the settable digit partial value is “X : 1-X ". According to this, in the above example, the setting ratio of “2” and “1” is 4: 6.
As will be described in detail later, such variable setting of the tap coefficient on the time axis allows at least integration as in the measurement evaluation value averaging process described earlier in the subsequent stage of the filter processing device. When the accompanying process is performed, an effect equivalent to the case where the target tap coefficient is set for the multiplier can be obtained. That is, it is possible to obtain an effect equivalent to extending the bit width of the tap coefficient more than the bit width of the settable tap coefficient.
As a result, for example, even when only a tap coefficient using an integer can be set in the multiplier, a filtering process in which a tap coefficient (a tap coefficient having a larger number of bits) including the decimal part as the target tap coefficient is performed is performed. The same effect as the case can be obtained.

  As described above, according to the filter processing apparatus (filter processing method) of the present invention, in the case where processing involving at least integration, such as the averaging processing of the measurement evaluation value conventionally performed in the subsequent stage, is performed. An effect equivalent to the case where the target tap coefficient is set for the multiplier can be obtained, that is, an effect equivalent to that the bit width of the tap coefficient is expanded beyond the bit width of the settable tap coefficient. Can be obtained. In other words, an effect equivalent to the expansion of the bit width of the tap coefficient set in the multiplier can be obtained without expanding the bit width of the tap coefficient set in the multiplier.

  As described above, according to the filter processing apparatus of the present invention, it is possible to obtain an effect equivalent to the improvement of the accuracy of the filter processing, while greatly increasing the hardware scale of the digital filter and the accompanying significant increase. Can prevent cost increase.

Further, the optical recording medium driving apparatus (evaluation value measuring method) of the present invention performs the filtering process according to the present invention on the reproduction signal from the optical recording medium, and the signal is based on the reproduction signal subjected to the filtering process. A quality evaluation value serving as a quality evaluation index is measured a plurality of times per unit time, and at least the evaluation values measured a plurality of times are integrated.
According to such an optical recording medium driving device of the present invention, the accuracy equivalent to that when the bit width of the tap coefficient set in the multiplier is expanded without expanding the bit width of the tap coefficient set in the multiplier. The evaluation value can be obtained.
That is, according to the optical recording medium driving device of the present invention, it is possible to improve the measurement accuracy of the evaluation value while preventing the hardware scale of the digital filter from being significantly increased and the accompanying cost increase. it can.

It is the figure which showed the internal structure of the optical recording medium drive device as embodiment. It is the figure which showed the internal structure of the equalizer (filter processing apparatus as embodiment) with which the optical recording medium drive device as embodiment is provided. It is a figure for demonstrating the evaluation value measuring method as embodiment. It is a figure for demonstrating the improvement of the measurement precision of the quality evaluation value as an edge position error by the variable setting operation | movement of the tap coefficient as embodiment. It is the figure which showed the internal structure of the tap coefficient setting part. It is a timing chart for demonstrating operation | movement of a tap coefficient setting part. It is the figure which showed the internal structure of the tap coefficient setting part as a modification. It is the figure which showed the structure as a prior art example for obtaining the evaluation value showing the error of the edge position of a reproduction signal in the optical disk system which performs PRML decoding. It is the figure which showed the internal structure of the equalizer as a prior art example. It is a figure for demonstrating the operation | movement which the equalizer as a prior art example respond | corresponds at the time of evaluation value measurement.

Hereinafter, the best mode for carrying out the invention (hereinafter referred to as an embodiment) will be described.
The description will be made in the following order.

<1. Device configuration>
[1-1. Internal configuration of disk drive unit]
[1-2. Internal structure of equalizer]
<2. Evaluation Value Measuring Method as Embodiment>
[2-1. Specific method]
[2-2. Configuration and operation of tap coefficient setting unit]
[2-3. Summary of Embodiment]
<3. Modification>

<1. Device configuration>
[1-1. Internal configuration of disk drive unit]

FIG. 1 shows an internal configuration of a disk drive device 1 as an embodiment of an optical recording medium driving device of the present invention.
In FIG. 1, a configuration mainly relating to recording / reproduction and evaluation value measurement in the disk drive device 1 is extracted and shown, and other configurations such as various servo systems such as tracking and focusing are not shown. ing.

In FIG. 1, an optical disk D is a disk-shaped optical recording medium. An optical recording medium refers to a recording medium on which a recording signal is reproduced by light irradiation.
The optical disk D is rotated by a spindle motor (SPM) 2 in the drawing during recording / reproduction.

  The optical head 3 (optical pickup) irradiates the optical disc D with laser light emitted from a laser diode via an objective lens by a predetermined optical system. Further, the optical head 3 guides the reflected light from the optical disc D to a photodetector through a predetermined optical system, and obtains an electrical signal corresponding to the amount of reflected light. Further, arithmetic processing is performed on each light quantity signal detected by a plurality of photodetectors, and a reproduced signal sA (reproduced RF signal) of recorded information and various servo error signals such as tracking and focus are generated.

At the time of recording, a recording signal DL is supplied from the recording signal generator 8 to the optical head 3. The recording signal DL is a driving signal for the laser diode in the optical head 3, and the laser diode is driven to emit light in accordance with the recording signal DL.
At the time of recording, the recording data to be recorded on the optical disc D is subjected to an encoding process such as RLL (1, 7) modulation by the recording data encoder 9, and the encoded signal DR is supplied to the recording signal generator 8. . The recording signal generator 8 generates a recording signal DL as a laser drive signal corresponding to the encode signal DR.
Here, so-called write strategy setting such as pulse level, pulse width, and pulse edge timing as a laser drive signal is instructed from the controller 10. That is, the recording signal generator 8 has a function of setting the intensity for emitting the laser and a function of setting the light emission time / timing. By adjusting the recording signal DL as the laser driving signal, the recording signal generator 8 Recording conditions can be adjusted.

During reproduction, the reproduction signal sA read by the optical head 3 is supplied to the reproduction clock generation / sampling unit 4. The reproduction clock generation / sampling unit 4 generates a reproduction clock CK synchronized with the reproduction signal sA by using a PLL (Phase Locked Loop) circuit, and also performs digital sampling of the reproduction signal sA to obtain a sampling signal (digital reproduction signal) DS. Is output.
The recovered clock CK is used for processing in the equalizer 5, Viterbi decoder 6, and evaluator 11.
The sampling signal DS is supplied to the equalizer 5.

The equalizer 5 includes an FIR (Finit Impulse Response) filter 5a, and performs PR (Partial Response) equalization processing by giving a required frequency characteristic to the reproduction signal DS.
Similarly to the equalizer 100 described as the conventional example, the equalizer 5 of the present embodiment is also adapted to perform adaptive equalization processing corresponding to the time of data reproduction. Therefore, the equalizer 5 receives the decoded data DT from the Viterbi decoder 6 as shown in the figure.
The internal configuration of the equalizer 5 will be described later.

  A reproduction signal DS (hereinafter referred to as equalized signal yk) that has been equalized by the equalizer 5 is supplied to the Viterbi decoder 6 and the evaluator 11.

  The Viterbi decoder 6 performs binarization processing of the reproduction signal by so-called Viterbi decoding processing. That is, the Viterbi decoder 6 uses the equalized signal yk and the bits that can be assumed for the equalized signal yk that has been waveform-shaped so that the reproduction signal DS conforms to a predetermined PR class by the equalization processing in the equalizer 5. The Euclidean distance with the partial response of the sequence is checked, and the bit sequence with the closest distance is output as the detection result.

  The decoded data (binary data string) DT obtained by the decoding process by the Viterbi decoder 6 is supplied to the reproduction data decoder 7, and a demodulation process, error correction process, deinterleave, etc. for RLL (1, 7) modulation and the like. Thus, the demodulated reproduction data is obtained.

The decoded data DT output from the Viterbi decoder 6 is also supplied to the evaluator 11.
The evaluator 11 measures a quality evaluation value representing an error in the edge position of the reproduction signal based on the equalized signal yk, the decoded data DT, and the reproduction clock CK.
Specifically, the evaluator 11 includes an evaluation value measuring unit 11a for each mark length that measures the quality evaluation value for each mark length (recording mark length) based on the equalized signal yk, the reproduction clock CK, and the decoded data DT. An averaging unit 11b is provided for averaging the evaluation values measured for each mark length by the evaluation value measuring unit 11a for each mark length.

In this case, the evaluation value measuring unit 11a measures the quality evaluation value as an error between the zero cross timing of the equalized signal yk and the edge timing of the reproduction clock CK.
Specifically, the evaluation value measuring unit 11a for each mark length measures, for each zero cross point of the equalized signal yk, an error between the timing of the zero cross point and the edge timing of the reproduction clock CK as a quality evaluation value, Based on the decoded data DT, the measured quality evaluation value is stored separately for each mark length.

  For confirmation, in order to divide the quality evaluation value measured as described above for each mark length based on the decoded data DT, the equalized signal yk and the decoded signal for the evaluation value measuring unit 11a for each mark length are decoded. The input timing with the data DT is synchronized. For this reason, the equalized signal yk is actually input to the evaluation value measuring unit 11a for each mark length after being delayed by a predetermined time (viterbi decoding processing time).

Of course, the evaluation value measuring unit 11a for each mark length can also be configured to measure dSAM as described in Patent Document 1 as a quality evaluation value representing the error of the edge position.
As described in Patent Document 1, the evaluation value can be measured not only for the mark length but also for each combination of the mark length and the space length.

In the evaluator 11, the averaging unit 11b averages the quality evaluation values measured for each mark length by the evaluation value measuring unit 11a for each mark length as described above. Specifically, the quality evaluation values stored separately for each mark length as described above are averaged.
The quality evaluation value for each mark length obtained by the evaluator 11 is supplied to the controller 10.

The controller 10 includes a microcomputer having a CPU (Centeral Processing Unit), ROM, RAM, and the like. The controller 10 performs overall control of the disk drive device 1 by executing control and processing in accordance with a program stored in the ROM or the like.
Particularly in the case of the present embodiment, the controller 10 evaluates the reproduction signal quality based on the quality evaluation value obtained by the evaluator 11, and performs recording condition setting processing (write strategy setting) according to the evaluation result.

Here, during the write strategy adjustment operation, the controller 10 instructs the recording data encoder 9 to output test writing data (test pattern data), and instructs the recording signal generator 8 to specify the recording waveform adjustment parameters. The test writing operation is executed while sequentially changing the conditions.
Then, reproduction is performed for the portion where test writing has been performed in this way, and a quality evaluation value measured (calculated) by the evaluator 11 is acquired along with this, and each recording condition is determined based on the acquired quality evaluation value. The reproduction signal quality is evaluated, and the optimum recording condition setting process is performed based on the result.

Further, the controller 10 generates and outputs a reproduction / evaluation value measurement identification signal. This reproduction / evaluation value measurement identification signal indicates whether normal data reproduction is performed or whether a quality evaluation value measurement operation is performed in accordance with the write strategy adjustment operation as described above. Signal.
As shown in the figure, the reproduction / evaluation value measurement identification signal is supplied to the equalizer 5.

[1-2. Internal structure of equalizer]

FIG. 2 shows an internal configuration of the equalizer 5 shown in FIG.
FIG. 2 also shows the Viterbi decoder 6 shown in FIG. 1 together with the internal configuration of the equalizer 5.
First, the equalizer 5 is provided with an FIR filter 5a.
As shown in the figure, the reproduction signal DS is given to the FIR filter 5a as an input signal. In the FIR filter 5a, a delay circuit 15A and a delay circuit 15B are inserted into a line for inputting the reproduction signal DS, and a tap T1 for branching and outputting the reproduction signal DS before being input to the delay circuit 15A, and A total of three taps are formed: a tap T2 for branching and outputting the reproduction signal DS that has passed through the delay circuit 15A, and a tap T3 for branching and outputting the reproduction signal DS that has passed through the delay circuit 15B.
Further, the FIR filter 5a is provided with a multiplier 16-1, a multiplier 16-2, and a multiplier 16-3 for giving tap coefficients corresponding to the taps T1, T2, and T3, respectively.
Further, an adder 17 is provided which adds the multiplication results of the multipliers 16-1, 16-2 and 16-3 to obtain an equalized signal yk which is an output signal of the FIR filter 5a.
As shown in the figure, the equalized signal yk obtained by the adder 17 is supplied to the Viterbi decoder 6.

  Here, in the FIR filter 5a of the present embodiment, it is assumed that only a tap coefficient can be set for each multiplier 16 by an integer. That is, the hardware scale of each multiplier 16 is set to allow only setting of tap coefficients by integers.

  Further, the equalizer 5 receives the tap coefficient update processing unit 18 and the tap coefficients as adaptive equalization coefficients obtained by the tap coefficient update processing unit 18 from the multipliers 16-1, 16-2, 16-3. Tap coefficient setting units 19-1, 19-2, 19-3 are provided.

As shown in the figure, the tap coefficient update processing unit 18 receives the equalized signal yk from the FIR filter 5 a and the decoded data DT obtained by the decoding process by the Viterbi decoder 6.
The tap coefficient update processing unit 18 calculates tap coefficients (coefficients for adaptive equalization) to be set in each multiplier 16 in order to realize the adaptive equalization process described above. Specifically, the tap coefficient update processing unit 18 obtains a signal waveform (partial response sequence) obtained by weighting and adding a coefficient based on a predetermined PR characteristic such as (1, 2, 2, 1) to the decoded data DT. Is a target waveform, an error (that is, an equalization error) between the target waveform and the waveform of the equalized signal yk is calculated, and a tap coefficient that minimizes the error is calculated.

  For confirmation, for the equalization signal yk input to the tap coefficient update processing unit 18 in order to correctly calculate the equalization error based on the decoded data DT, A delay of a predetermined time (viterbi decoding processing time) is given.

  The tap coefficients calculated by the tap coefficient update processing unit 18 as described above (tap coefficients for each multiplier 16) are tap coefficient setting units 19-1, 19-2, 19-3 as adaptive equalization coefficients. Supplied against. For confirmation, the adaptive equalization coefficient to be set in the multiplier 16-1 is applied to the tap coefficient setting unit 19-1, and the adaptive equalization coefficient to be set in the multiplier 16-2. Is supplied to the tap coefficient setting unit 19-2, and the adaptive equalization coefficient to be set to the multiplier 16-3 is supplied to the tap coefficient setting unit 19-3.

Similar to the tap coefficient setting unit 109 described above as the conventional example, the tap coefficient setting unit 19 indicates that the reproduction / evaluation value measurement identification signal indicates normal data reproduction, and a tap coefficient update processing unit. The coefficient for adaptive equalization supplied from 18 is output (set) to the corresponding multiplier 16.
That is, also in this embodiment, adaptive equalization processing is executed in response to normal data reproduction, and this point is the same as in the conventional example.

Here, the internal configuration of the tap coefficient setting unit 19 as the present embodiment and the operation performed in response to the evaluation value measurement will be described later.

<2. Evaluation Value Measuring Method as Embodiment>
[2-1. Specific method]

As described above, the evaluation value representing the edge position error is required to have very high error detection accuracy such as T / 32 or T / 64 (T represents a channel bit).
In order to achieve such high error detection accuracy, it is necessary for the equalizer 5 to obtain higher accuracy than the equalization accuracy required for data reproduction by PRML decoding.
At this time, the equalization accuracy by the equalizer 5 is determined depending on the number of taps of the FIR filter 5a and the number of bits of the tap coefficient. Therefore, in realizing the above high error detection accuracy, the number of taps and the tap coefficient are used. The number of bits should be increased.

  However, as described above, when the number of taps and the number of tap coefficient bits are increased, the cost of the device cannot be avoided. In particular, when the number of tap coefficient bits is increased, the cost of the digital multiplier circuit as the multiplier 16 is generally increased by considering that the scale of the digital multiplier circuit increases by a power of 2 with respect to the increase in the number of input bits. Will be invited.

  In addition, high accuracy is required only during evaluation value measurement, and if the number of taps or the number of tap coefficient bits is increased as described above, equalization processing becomes overspec when normal data is reproduced. In that sense, it can be said that waste occurs.

  Therefore, in the present embodiment, the number of tap coefficient bits of the FIR filter 5a is increased (the bit width is expanded) by performing variable setting of the tap coefficient as described below in response to the evaluation value measurement. Without effect, an effect equivalent to the case where the bit width of the tap coefficient is expanded is obtained.

FIG. 3 is a diagram for explaining an evaluation value measurement technique as the present embodiment including the tap coefficient variable setting operation.
First, when performing write strategy adjustment, test writing is performed under different recording condition settings as described above, and evaluation values are measured for signals recorded under these different recording conditions. Will do.
As shown in FIG. 3, here, a case where trial writing is performed under two different recording conditions of recording condition 1 and recording condition 2 is illustrated.

Here, in the conventional example described above, a predetermined fixed coefficient is set as a tap coefficient when measuring the quality evaluation value (see FIG. 10).
That is, as the fixed tap coefficient, for example, the tap coefficient convergence result of the adaptive equalization process on the optical disc D is measured in advance at a plurality of times and at a plurality of positions, and the result is excluded (for example, sorted to the upper and lower (Excludes some of the values) and averages, etc., to obtain a coefficient that achieves the desired partial response equalization and does not absorb the difference in the recording conditions. A fixed tap coefficient is set.
As described above, by performing equalization processing (that is, no adaptive equalization processing is performed) in which a fixed tap coefficient is set in advance corresponding to the evaluation value measurement, the difference in recording conditions is absorbed. It is possible to prevent the proper calibration operation from being performed.

Also in the present embodiment, the fixed tap coefficient to be set corresponding to the evaluation value measurement in advance is obtained in advance and is retained on the apparatus side in the same manner as in the conventional example. It becomes.
However, in the present embodiment, as the fixed tap coefficient to be set corresponding to the evaluation value measurement in this way, a more detailed value including a numerical value on the lower digit side than the conventional example is given to the apparatus. It shall be retained.
Specifically, for example, in the conventional example, it is assumed that only the integer tap coefficient can be set in the multiplier (106), and only the value of the integer part is held as the fixed tap coefficient. In this embodiment, the value after the decimal point is held together with the value of the integer part.

FIG. 3 illustrates a case where the tap coefficient obtained in advance by actually measuring the convergence result of the tap coefficient as described above is “1.4”, for example.
In the present embodiment, the tap coefficient previously obtained in this way is held on the apparatus side as a target coefficient.

In the present embodiment, when the evaluation value is measured, the target coefficient held as described above is not set as it is to the multiplier 16, and the tap coefficient can be changed according to the value of the target coefficient. Set up.
Specifically, in the case of this example, only the integer tap coefficient can be set in the multiplier 16, so that the value of the integer part and the value of the integer part are set according to the numerical value of the target coefficient. On the other hand, the numerical value obtained by adding “1” is variably set such that the setting ratio on the time axis becomes a setting ratio corresponding to the value of the decimal part of the target coefficient.

  More specifically, if the target coefficient is “1.4”, the value of the integer part is “1”, and the value obtained by adding “1” to the value of the integer part is “2”. These values are variably set so that the setting ratio on the time axis becomes a setting ratio corresponding to the value of the decimal part of the target coefficient.

Here, in order to set the coefficient “2” and the coefficient “1” in a time-sharing manner and equivalently set the coefficient “1.4”, the coefficient “2” as shown in FIG. The setting ratio on the time axis with the coefficient “1” may be 4: 6.
In this example, the setting ratio on the time axis between the value of the integer part of the target coefficient and the value obtained by adding “1” to the value of the integer part is set as follows.
That is, the value obtained by adding “1” to the value of the integer part of the target coefficient is A, the value of the integer part of the target coefficient is B, and the value obtained by subtracting the value of the integer part from the value of the target coefficient (above In the example, when “0.4”) is x,

A: B = x: 1-x

Is set to

  Such coefficient variable setting based on the setting ratio is performed independently for each recording condition as shown in the figure. That is, in this case, the evaluation value measurement period for one recording condition is set as one unit period, and the coefficient setting ratio on the time axis in the unit period is set to the above ratio. Variable setting is performed.

  While the coefficients A and B are variably set, the quality evaluation value (edge position error) is measured by the evaluator 11 described above during each evaluation value measurement period for each recording condition. Is done. Specifically, in each evaluation value measurement period for each recording condition, an edge position error is measured for each mark length, and the measured edge position error is averaged for each mark length.

  According to the evaluation value measurement method as the present embodiment including the variable setting operation of the tap coefficient as described above, the measurement accuracy of the quality evaluation value as the edge position error is the case where the tap coefficient is set to the target coefficient. Equivalent accuracy can be achieved.

  FIG. 4 is an image diagram for explaining this point. FIG. 4A shows an image of the target characteristic of the equalization processing by the equalizer 5, and FIG. 4B shows the coefficient A (target coefficient integer part) described above. FIG. 4C shows a waveform image after equalization processing when the above-described coefficient B (value of the target coefficient integer part) is set. Show.

Here, if the target coefficient originally includes a numerical value after the decimal point, it is possible to set only an integer tap coefficient in the multiplier 16 as in this example. An error occurs.
In view of this point, for example, in FIG. 4B, an equalization error has occurred due to the equalization process in which the tap coefficient “2” is set for the target coefficient that is originally “1.4”. It can also be understood that it shows a waveform image of the case. Similarly, FIG. 4C shows a waveform image when an equalization error occurs due to the equalization process in which the tap coefficient “1” is set for the target coefficient that is originally “1.4”. Can be taken as an indication.

  Then, as can be seen by comparing FIG. 4 (b), FIG. 4 (c) and FIG. 4 (a), when an equalization error accompanying the tap coefficient quantization error as described above occurs, etc. Corresponding errors also occur at the edge position (zero cross position) of the digitized signal yk. That is, due to this error, the measurement accuracy of the quality evaluation value as the edge position error is lowered.

  As can be understood from this, in order to improve the measurement accuracy of the quality evaluation value as the edge position error, the quantization error of the tap coefficient is reduced, that is, an equalization process in which the target coefficient is set equivalently. This means that it is necessary to create a state in which is performed.

According to the method of the present embodiment described above, the edge position error values measured under the setting of the coefficient A and the setting of the coefficient B are averaged. This corresponds to the averaging of the edge position error value measured for the waveform of FIG. 4B and the edge position error value measured for the waveform of FIG. 4C.
At this time, in the present embodiment, the setting ratio of the coefficient A and the coefficient B on the time axis is set to be equivalent to the case where the target coefficient is set equivalently. By averaging the edge position error values measured under the setting of A and the coefficient B, the edge position error value finally obtained is equivalent to that when the target coefficient is set. It can be a numerical value. That is, as a result, the measurement accuracy of the quality evaluation value as the edge position error can be equal to that when a target coefficient including a numerical value after the decimal point is set.

By the way, in this embodiment, the quality evaluation value as the edge position error is measured for each mark length.
At this time, when focusing on one mark length, if the appearance frequency of the signal of the mark length is significantly different under the setting of the coefficient A and the setting of the coefficient B, the coefficient A and the coefficient The measurement result at the time of setting one of the coefficients of B becomes dominant, and it may be impossible to effectively improve the measurement accuracy of the evaluation value.
Considering this point, the test pattern data to be recorded on the optical disc D for one recording condition includes the appearance frequency under the setting of the coefficient A and the appearance frequency under the setting of the coefficient B for each mark length signal. Is ideally set to be equivalent to each other.
For this reason, in the present embodiment, random data such that signals of respective mark lengths appear at random is adopted as test pattern data used as test writing data for write strategy adjustment. Thereby, the measurement accuracy of the quality evaluation value as the edge position error can be improved more effectively.

[2-2. Configuration and operation of tap coefficient setting unit]

The tap coefficient variable setting operation according to the present embodiment described above is realized by the tap coefficient setting unit 19 in the equalizer 5 shown in FIG.
FIG. 5 shows the internal configuration of the tap coefficient setting unit 19.
In FIG. 5, the multiplier 16 shown in FIG. 2 is also shown.

In FIG. 5, the tap coefficient setting unit 19 includes a selector 20.
The selector 20 receives the adaptive equalization coefficient from the tap coefficient update processing unit 18 shown in FIG. Also, the selector 20 receives a reproduction / evaluation value measurement identification signal from the controller 10 shown in FIG. 1 as its switching control signal.
The selector 20 sets / not sets the adaptive equalization coefficient based on the reproduction / evaluation value measurement identification signal, similarly to the selector 111 provided in the tap coefficient setting unit 109 as the conventional example shown in FIG. It functions as a selector for switching.

Further, the tap coefficient setting unit 19 of the present embodiment has a target coefficient holding unit 21, a configuration for giving the selector 20 a coefficient to be set to the multiplier 16 corresponding to the evaluation value measurement. An adder 22, a selector 23, a counter 24, and a comparator 25 are provided.
First, the target coefficient holding unit 21 is set with a tap coefficient obtained in advance by actually measuring the tap coefficient convergence result as described above, as the target coefficient.
In this example, since the target coefficient has an integer part value and a decimal part value, the target coefficient holding part 21 holds the integer part value and the decimal part value of the target coefficient. Become.

  For confirmation, in FIG. 5, tap coefficient setting units 19-1 to 19-3 that are actually provided for the respective multipliers 16 of the multipliers 16-1 to 16-3 are shown in FIG. Are collectively shown as the tap coefficient setting unit 19, but the target coefficient obtained in advance as described above is obtained for each multiplier 16 of the multipliers 16-1 to 16-3. Accordingly, the target coefficient holding unit 21 holds one corresponding coefficient among these target coefficients.

  The value of the integer part of the target coefficient held by the target coefficient holding unit 21 is supplied to the selector 23 and the adder 22. The adder 22 adds “1” to the value of the integer part of the target coefficient and outputs the addition result to the selector 23.

On the other hand, the value of the decimal part of the target coefficient held in the target coefficient holding unit 21 is supplied to the comparator 25. Further, the count value by the counter 24 is also supplied to the comparator 25. The counter 24 is a free-run counter that repeatedly counts from 0 to n-1 (n is a natural number).
The output signal of the comparator 25 is supplied to the selector 23 as a switching control signal for the selector 23.

The output from the selector 23 is supplied to the selector 20.
The selector 20 alternatively outputs (sets) one of the output from the selector 23 and the above-mentioned adaptive equalization coefficient to the multiplier 16 based on the reproduction / evaluation value measurement identification signal. ).
Specifically, when the reproduction / evaluation value measurement identification signal indicates that normal data reproduction is in progress, the adaptive equalization coefficient is selected and output. If the reproduction / evaluation value measurement identification signal indicates that the evaluation value is being measured, the output from the selector 23 is selectively output.

  FIG. 6 is a timing chart for explaining the operation of the tap coefficient setting unit 19 shown in FIG. 5. The count value of the counter 24 (counter in the figure), the output of the comparator 25 (comparator output), and the output of the selector 23 ( (Selector output) on each time axis.

First, as described above, the counter 24 repeatedly counts from 0 to n-1. As shown in the figure, the counter 24 counts from 0 to n-1 within an evaluation value measurement period for one recording condition. In other words, the count cycle by the counter 24 is a cycle obtained by dividing the evaluation value measurement period for one recording condition into n equal parts.
In the case of this example, the evaluation value measurement period for one recording condition (that is, the recording length of trial writing performed for one recording condition) is set to a predetermined length. Therefore, based on the period length, for example, the reproduction clock CK Is multiplied to generate a clock of 1 / n period of the evaluation value measurement period, which is given as an operation clock of the counter 24. As a result, the counter 24 counts from 0 to n−1 in the evaluation value measurement period for one recording condition.

  Here, in this example, the case where the setting of a numerical value up to the first decimal place is permitted as the target coefficient is illustrated. Corresponding to this, “10” is set as the value of n, and the counter 24 is made to count from 0 to 9 in the evaluation value measurement period for one recording condition.

As shown in FIG. 5, the count value of the counter 24 and the value of the decimal part of the target coefficient are input to the comparator 25. That is, as described above, the count value that changes between 0 and 9 within the evaluation value measurement period for one recording condition, and, for example, the fractional part when the target coefficient is “1.4” as exemplified above. “4”, which is the value of, is input.
At this time, if the value of the decimal part of the target coefficient is set to “i”, the comparator 25 sets the level of the output signal to H when the count value is less than “i” and when it is greater than or equal to “i”. Operates to switch at / L. That is, in the example of the target coefficient = “1.4”, the level of the output signal is switched between H / L depending on whether the count value of the counter 24 is less than or equal to “4”.

  On the other hand, as described above, the output signal from the comparator 25 serves as a switching control signal for the selector 23. Therefore, the selector 23 determines that when the count value is less than “i” and “i”. When this is the case, the output of the coefficient (coefficient A) based on the value of the integer part + 1 of the target coefficient and the output of the coefficient (coefficient B) based on the value of the integer part of the target coefficient are switched.

As illustrated in FIG. 6, in this example, when the count value of the counter 24 is less than “i”, the comparator 25 sets the output signal to the H level, and the count value is “i” or more. In some cases, the output signal is set to L level.
The selector 23 selectively outputs a coefficient based on the value of the integer part + 1 of the target coefficient when the output signal from the comparator 25 is H level, and a coefficient based on the value of the integer part of the target coefficient when the output signal is L level. Is selected and output.
That is, by this, when the count value is less than “i”, the selector 23 to the selector 20 is given the coefficient A as the value of the integer part + 1 of the target coefficient, and the count value is equal to or greater than “i”. In some cases, the coefficient B is given as the value of the integer part of the target coefficient. Accordingly, when the evaluation value is measured, the multiplier 16 is set with the coefficient A when the count value is less than “i”, and with the coefficient B when the count value is greater than or equal to “i”. .

  As described above, according to the tap coefficient setting unit 19 shown in FIG. 5, at the time of evaluation value measurement, the setting ratio on the time axis between the coefficient A and the coefficient B for the multiplier 16 is set to the decimal part of the target coefficient. Can be set according to the value. Specifically, when the value obtained by subtracting the value of the integer part from the target coefficient value is x, the ratio of coefficient A: coefficient B can be set to “x: 1−x”.

In the above example, the target coefficient is set to n = 10 as the target coefficient is allowed to be set to the first decimal place. However, for example, the setting to the second decimal place is allowed. When the number of digits on the lower digit side of the target coefficient increases, the number of digits of n may be increased accordingly. For example, when the target coefficient is “1.45”, n = 100, and 0 to 99 are counted in the evaluation value measurement period for one recording condition. Since i = 45 at this time, the setting ratio of the coefficient A: the coefficient B on the time axis is set to 45:55 (x: 1−x = 0.45: 0.55).

[2-3. Summary of Embodiment]

As described above, according to the present embodiment, an effect equivalent to the case where the bit width of the tap coefficient is expanded can be obtained without expanding the bit width of the tap coefficient. Specifically, the measurement accuracy of the quality evaluation value as the edge position error can be improved without extending the bit width of the tap coefficient.
In other words, according to the present embodiment, it is possible to improve the equalization processing accuracy while preventing the hardware scale of the FIR filter 5a from being greatly increased by extending the bit width of the tap coefficient and the accompanying cost increase. An effect equivalent to that described above, specifically, an effect of improving the measurement accuracy of the quality evaluation value as an error of the edge position can be obtained.

  Further, if the measurement accuracy of the quality evaluation value is improved as described above, the accuracy of the adjustment operation of the recording waveform adjustment parameter such as the write strategy performed using the quality evaluation value can be improved.

In addition, since this embodiment does not improve the measurement accuracy of the evaluation value by extending the bit width of the tap coefficient, the equalization process at the time of normal data reproduction becomes overspec, and this point is wasted. Can be avoided.

<3. Modification>

Although the embodiments of the present invention have been described above, the present invention should not be limited to the specific examples described above.
For example, the configuration of the tap coefficient setting unit 19 can be changed as shown in FIG.
In FIG. 7, the tap coefficient setting unit 19 in this case omits the adder 22 shown in FIG. In this case, in place of the coefficient holding unit 21 shown in FIG. 5, a coefficient holding unit 30 for holding the integer part value (coefficient B) of the target coefficient and a value of the integer part + 1 of the target coefficient (coefficient A) are held. And a coefficient holding unit 32 for holding the decimal part value of the target coefficient.
A coefficient A held by the coefficient holding unit 31 and a coefficient B held by the coefficient holding unit 30 are input to the selector 23. In this case, the selector 23 alternatively outputs one of the coefficient A and the coefficient B to the selector 20 based on the output signal of the comparator 25.
In this case, the value of the decimal part of the target coefficient held by the coefficient holding unit 32 is input to the comparator 25 together with the count value of the counter 24. Also in this case, the operations of the counter 24 and the comparator 25 are the same as those described with reference to FIG.

  In the above description, in FIG. 3, the coefficient A is set continuously for a period corresponding to the ratio x within the evaluation value measurement period for one recording condition, and then the remaining period coefficient B is continuously set. However, in the present invention, the setting ratio of the coefficient A and the coefficient B on the time axis is, as a result, x: x−1 (a ratio according to a numerical value less than the settable minimum digit). The order of setting the coefficients A and B and the switching timing thereof are not particularly limited.

Moreover, although the case where the FIR filter 5a is used for the equalization process by the equalizer 5 was illustrated in the above description, an IIR filter can be used instead.
Further, the numerical values such as the number of taps and the number of digits of the tap coefficient (bit width) exemplified in the above description are merely examples, and should not be limited to them.

  In the description so far, the case where the quality evaluation value measured based on the equalized signal yk is averaged is illustrated. However, in order to improve the accuracy of the quality evaluation value, the measured quality evaluation value is used. Should be integrated at least.

  Further, in the description so far, the case where the quality evaluation value representing the error of the edge position of the reproduction signal is measured based on the equalized signal yk obtained by the filter processing of the equalizer 5 is exemplified. As an evaluation value obtained by measuring a quality evaluation value, which is an evaluation index of signal quality, a plurality of times per unit time based on a reproduction signal filtered by a filter processing unit such as the equalizer 5 and a plurality of times As long as it integrates at least.

In the above description, the case where the filter processing apparatus of the present invention is applied to a drive device for an optical recording medium has been exemplified. However, the filter processing apparatus of the present invention is also widely suitable for other apparatuses. Can be applied.
According to the filter processing device of the present invention, the evaluation value measured a plurality of times per unit time as described above for the signal after the filter processing by the filter processing device, and the evaluation value measured a plurality of times in this way Corresponding to the case where at least integration is performed, an effect equivalent to the expansion of the bit width of the tap coefficient can be obtained.

  DESCRIPTION OF SYMBOLS 1 Disc drive apparatus, 2 Spindle motor, 3 Optical head, 4 Reproduction clock generation / sampling part, 5 Equalizer, 5a FIR filter, 6 Viterbi decoder, 7 Reproduction data decoder, 8 Recording signal generation part, 9 Recording data encoder, 10 Controller, 11 Evaluator, 11a Evaluation unit for each mark length, 11b Averaging unit, 15A, 15B Delay circuit, 16-1 to 16-3 multiplier, 17,22 Adder, 18 Tap coefficient update processing unit, 19 -1 to 19-3 Tap coefficient setting unit, 20, 23 selector, 21 target coefficient holding unit, 24 counter, 25 comparator, 30, 31, 32 coefficient holding unit

Claims (9)

A filter processing apparatus that includes a digital filter and performs a filtering process on an input signal,
A multiplier whose tap coefficient is variably set;
A target tap coefficient holding unit that holds a target tap coefficient that is set to a numerical value having a larger number of digits on the lower digit side than the settable tap coefficient that can be set in the multiplier;
A settable digit partial value that is a numerical value of the portion of the target tap coefficient that is greater than or equal to the minimum digit of the settable tap coefficient, and a minimum digit value obtained by adding 1 to the value of the minimum digit for the settable digit partial value A coefficient alternative setting unit that alternatively outputs one of them and sets it in the multiplier for the added numerical value,
The setting ratio of the minimum digit value addition value and the settable digit part value for the multiplier on the time axis is a numerical value of a part on the lower digit side of the settable digit part in the target tap coefficient. A filter processing apparatus comprising: a coefficient setting ratio control unit that controls the coefficient alternative setting unit so as to obtain a setting ratio according to a numerical value that is less than the minimum settable digit. The coefficient setting ratio control unit
When a value obtained by subtracting the settable digit partial value from the target tap coefficient value is X, a setting ratio on the time axis between the minimum digit value added value and the settable digit partial value is X: 1- The filter processing apparatus according to claim 1, wherein control is performed so that X is set. A filter processing method in a filter processing apparatus that includes a digital filter and performs filter processing on an input signal,
The numerical value of the portion of the target tap coefficient that has more digits than the settable tap coefficient that can be set in the multiplier included in the digital filter and that is greater than the minimum digit of the settable tap coefficient. A settable digit partial value and a minimum digit value added value obtained by adding 1 to the minimum digit value of the settable digit partial value are set to the multiplier with a setting ratio on the time axis. A filter processing method for setting so as to have a setting ratio corresponding to a numerical value less than a minimum settable digit that is a numerical value of a lower digit side of the settable digit portion in the target tap coefficient. An optical head unit that irradiates the optical recording medium with laser light and receives reflected light to obtain a reproduction signal for the signal recorded on the optical recording medium;
A filter processing unit that includes a digital filter and performs filter processing on the reproduction signal,
A multiplier whose tap coefficient is variably set;
A target tap coefficient holding unit that holds a target tap coefficient that is set to a numerical value having a larger number of digits on the lower digit side than the settable tap coefficient that can be set in the multiplier;
A settable digit partial value that is a numerical value of the portion of the target tap coefficient that is greater than or equal to the minimum digit of the settable tap coefficient, and a minimum digit value obtained by adding 1 to the value of the minimum digit for the settable digit partial value A coefficient alternative setting unit that alternatively outputs one of them and sets it in the multiplier for the added numerical value,
The setting ratio of the minimum digit value addition value and the settable digit part value for the multiplier on the time axis is a numerical value of a part on the lower digit side of the settable digit part in the target tap coefficient. A filter processing unit comprising: a coefficient setting ratio control unit that controls the coefficient alternative setting unit so as to obtain a setting ratio according to a numerical value less than the minimum settable digit;
Based on the reproduction signal filtered by the filter processing unit, a quality evaluation value serving as an evaluation index of signal quality is measured a plurality of times per unit time, and at least the quality evaluation value measured a plurality of times is integrated. An optical recording medium driving device comprising: an evaluation unit. The evaluation section
The optical recording medium driving device according to claim 4, wherein an evaluation value representing an error in an edge position of the reproduction signal is measured as the quality evaluation value. The evaluation section
The optical recording medium driving device according to claim 5, wherein an evaluation value representing an error in the edge position is measured at least for each recording mark length. The evaluation section
The optical recording medium driving device according to claim 6, wherein an evaluation value representing an error of the edge position measured at least for each recording mark length is averaged for at least each recording mark length. The coefficient setting ratio control unit
When a value obtained by subtracting the settable digit partial value from the target tap coefficient value is X, a setting ratio on the time axis between the minimum digit value added value and the settable digit partial value is X: 1- The optical recording medium driving device according to claim 4, wherein control is performed so that X is set. An optical head unit for irradiating the optical recording medium with laser light and receiving reflected light to obtain a reproduction signal for the signal recorded on the optical recording medium, and a digital filter, and filtering the reproduction signal An evaluation value measuring method in an optical recording medium driving device comprising a filter processing unit to be applied,
The numerical value of the portion of the target tap coefficient that has more digits than the settable tap coefficient that can be set in the multiplier included in the digital filter and that is greater than the minimum digit of the settable tap coefficient. A settable digit partial value and a minimum digit value added value obtained by adding 1 to the minimum digit value of the settable digit partial value are set to the multiplier with a setting ratio on the time axis. A tap coefficient setting procedure for setting a setting ratio according to a numerical value less than a settable minimum digit that is a numerical value of a lower digit side of the settable digit part in the target tap coefficient;
Based on the reproduced signal filtered by the filter processing unit in which the tap coefficient is set by the tap coefficient setting procedure, a quality evaluation value serving as an evaluation index of signal quality is measured a plurality of times per unit time. And an evaluation procedure for integrating at least the quality evaluation values measured a plurality of times.

Images