JP2002124031A - Data reproducing device and data reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data reproducing device and a data reproducing method which can easily improve the reliability of reproduced data. SOLUTION: In the data reproducing device and the data reproducing method which binarize an alternate current(AC) signal obtained by reading data recorded on a recording medium by using the center of amplitude of the AC signal as a slice level, a direct current(DC) component is removed from the AC signal. The signal processing of a prescribed second signal characteristic which offsets a first signal characteristic given to the AC signal when the DC component is removed from the AC signal, is applied to the AC signal from which the DC component is removed. Either of the AC signal from which the DC component is removed and the AC signal to which the signal processing is performed, is binarized selectively. The AC signal is monitored, and the AC signal to which the signal processing is performed only when the signal level of the AC signal fluctuated more than a prescribed threshold, is binarized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data reproducing apparatus and a data reproducing method, and is suitably applied to, for example, an optical disk apparatus for reproducing data from an optical disk.

[0002]

2. Description of the Related Art Conventionally, in this type of optical disk reproducing apparatus, a CD (Compact Disc) or a DVD (Digital Versatile) is used.
Disc) or the like, and reproduces data recorded on the recording surface of an optical disc and sends it to a personal computer.

That is, as shown in FIG. 9, in an optical disk reproducing apparatus 1, a laser diode 3 of an optical pickup unit 2 transmits a light beam L1 through a collimator lens 4, a beam splitter 5, and an objective lens 6 in order in a reproducing mode. Irradiate the optical disk 7. And this light beam L1
The reflected light L2 from the optical disk 7 is incident on the light detection unit 9 via the collimator lens 8.

The light detecting section 9 has, for example, a light receiving surface of 6 to 8
The divided photodetector converts the reflected light L2 incident on each divided area into a current corresponding to the amount of reflected light, and sends each current signal S1 thus obtained to the current-voltage converter 10.

The current-to-voltage converter 10 converts the given 6 to 8 current signals S1 into current-to-voltage, and sends out the respective signals S3 thus obtained to the band dividing unit 13.

The band dividing section 13 is composed of a parallel circuit of a capacitor section 13A and a resistor section 13B.
The main signal S3 is subjected to band division processing.

[0007] The band dividing unit 13 includes the capacitor unit 1.
Passing four signals S3 out of six to eight signals S3 given to 3A (these four voltage signals are called A signal, B signal, C signal, and D signal, respectively) Thus, the frequency band is divided on the high frequency side, and each voltage signal having a high frequency is obtained.

[0008] Subsequently, the band dividing section 13 includes the capacitor section 1
In an adder circuit (not shown) provided at the subsequent stage of 3A,
By performing the addition process (A signal + B signal + C signal + D signal), an RF (Radio Frequency) signal S5 (high-frequency component of the sum signal) is generated, and the RF signal S5 thus obtained is transmitted to the AC coupling unit 14.

[0009] On the other hand, the band dividing section 13 outputs six to eight signals S3 (hereinafter referred to as A, B,
C, D, E, F, G, and H signals), thereby dividing the band on the low frequency side, and transmitting the low frequency voltage signals thus obtained to the servo signal processing unit 11.

The servo signal processing section 11 generates a low-frequency component of a sum signal (hereinafter referred to as a DC signal S6), a focus error signal, a tracking error signal, and the like based on the applied low-frequency voltage signals. Generate various servo error signals.

Subsequently, the servo signal processing section 11 sends the generated DC signal S6 to the result detecting section 32, and based on the generated various servo error signals, the spindle motor 15, the thread motor 16 and the biaxial actuator 17
, While the optical disk 7 is driven to rotate at a predetermined speed, processing such as tracking control and focus control necessary for reproducing data recorded on the optical disk 7 is performed.

The AC coupling section 14 is a differentiation circuit as shown in FIG. 10, and removes the DC component of the RF signal S5 by AC coupling the supplied RF signal S5. RF signal S7 consisting only of components
To the binarization circuit 18. In this case, the RF signal S7
Is an AC signal that fluctuates around the voltage value of _Vcenter .

The binarization circuit 18 initializes the slice level with the voltage value of _Vcenter , and supplies the supplied R level.
By comparing the value of the F signal S7 with the slice level, "0" and "1" digital signals are generated from the RF signal S7, and the RF signal S7 is applied to a so-called binary signal S9.

More specifically, the binarizing circuit 18 outputs the RF signal S7
Generates a "1" digital signal if is greater than the slice level, while generating a "0" digital signal if the RF signal S7 is less than the slice level, S7 is converted into a binary signal S9.

In this case, the binarization circuit 18 sets a condition (duty 50 [%) that the slice level passes through the center of the amplitude of the RF signal S7 and the ratio of the amplitude of the RF signal S7 to the slice level is 1: 1. ]) Can accurately generate a digital signal.

A PLL (Phase Lock Loop) 19 includes a phase comparator (not shown), an LPF (Low Pass Flilter), and a voltage controlled oscillator (VCO).
and a phase shift (reproduction clock) is monitored so that a reference clock signal S8 can be extracted from a binarized signal S9 obtained by binarizing an RF signal. This is for automatically adjusting the phase of the clock signal S8.

After the phase of the pulse signal coincides with the phase of the clock signal S8, the PLL 19
8 to maintain (lock) the output timing. In the following, after the phase of the pulse signal generated based on the RF signal S7 and the phase of the clock signal S8 match, the process from locking the output timing of the clock signal (hereinafter referred to as a reproduction clock signal) S8 is locked. It shall be called retraction.

Next, the reproduced clock signal S8 and the binary signal (reproduced data signal) S9 of the RF signal S7 generated by the PLL 19 are sent to the reproduction processing unit 20, where the data is determined, and the EFM demodulation and the error are performed. After a predetermined process such as a correction process is performed, it is output to the outside as a reproduction signal S10.

As described above, the optical disk reproducing apparatus 1
The data recorded on the optical disk 7 can be read without error.

[0020]

[Problems to be solved by the invention]

In the optical disk reproducing apparatus 1, when reproducing data on the optical disk 7 when reproducing a portion of the optical disk 7 where scratches and dust are present, the light beam L1 applied to the optical disk 7 is irregularly reflected by the scratch, or The amount of light L2 reflected by the light beam L1 decreases due to absorption by dust and the like.
As shown in (1), a dent occurs in the waveform of the signal S3. In FIG. 11, the horizontal axis represents time.

Then, the optical disk reproducing apparatus 1 outputs the signal S3
It is necessary for the AC coupling unit 14 to AC-couple the RF signal S5 (FIG. 11 (2)) obtained by dividing the signal S3 into bands and performing an addition operation in the process until the reproduction signal S10 is output based on Actually, since the AC coupling section 14 is mainly composed of a differentiating circuit, the dent portion of the RF signal S5 is adversely affected by the differential characteristics.

That is, the RF signal S7 obtained by the AC coupling
As shown in FIG. 11 (3), at a position corresponding to such a concave portion, a waveform is largely disturbed, and the center of amplitude is shifted, so-called rampage (hereinafter, this portion on an RF signal is referred to as a rampage region). ).

In this case, in the optical disk reproducing apparatus 1, in order to secure a duty of 50 [%] which is a condition for accurately generating a digital signal based on the RF signal S7, the deviation of the center of the amplitude due to the runaway of the RF signal S7. It is necessary to make the slice level follow in accordance with.

Therefore, in the optical disk reproducing apparatus 1, R
After the ramp-up of the F signal S5, whether or not a digital signal can be accurately generated based on the RF signal S7 depends on the slice level tracking performance.

That is, in the binarization circuit 18, when the follow-up performance of the slice level is poor, the RF signal S7 is binarized before the slice level becomes 50% of the duty of the RF signal S7. As shown in FIG. 12, there is a problem that an erroneous digital signal is generated. In FIG. 12, the horizontal axis represents time.

The PLL 19 pulls in the RF signal S7 based on a pulse signal generated when the RF signal S7 crosses the slice level.
Such a slice level has a duty with respect to the RF signal S7.
Until the relationship becomes 50%, the clock signal S8 synchronized with the digital signal cannot be generated.

Thus, in the optical disk reproducing apparatus 1, the binary signal S is reproduced in the reproduction processing section 20 until the slice level has a duty ratio of 50% with respect to the RF signal S7.
9 has a problem that the clock signal S8 used for the predetermined processing of No. 9 cannot be obtained.

The present invention has been made in view of the above points, and it is an object of the present invention to propose a data reproducing apparatus and a data reproducing method which can easily improve the reliability of reproduced data.

[0030]

According to the present invention, there is provided a data reproducing apparatus having a binarizing means, comprising: a first DC component removing means for removing a DC component from an AC signal; Signal processing means for performing, on the AC signal from which the component has been removed, signal processing of a second signal characteristic for canceling the first signal characteristic given to the AC signal by the removing means, an AC signal and a signal from which the DC component has been removed; Selecting means for selectively outputting one of the processed AC signals to the binarizing means; and monitoring the AC signal, and performing signal processing only when the signal level of the AC signal fluctuates by a predetermined threshold or more. And control means for controlling the selection means so as to select the AC signal subjected to. As a result, the data reproducing apparatus can binarize with high accuracy.

According to the present invention, in the data reproducing method, a first step of removing a DC component from the AC signal, and a first step of applying the AC signal from which the DC component has been removed to the AC signal in the first step. A second step of performing signal processing of a second signal characteristic for canceling the signal characteristic of the above, and selectively binarizing any one of the AC signal from which the DC component has been removed and the AC signal subjected to the signal processing And a third step of monitoring the AC signal and binarizing the AC signal subjected to the signal processing only when the signal level of the AC signal fluctuates by a predetermined threshold or more. As a result, according to this data reproducing method, 2
Can be valued.

[0032]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention;

In FIG. 1 in which parts corresponding to those in FIG. 9 are assigned the same reference numerals, reference numeral 30 denotes an optical disk reproducing apparatus according to the present embodiment as a whole.
Defect detection unit 3 for detecting the runaway of DC signal S6 of signal S3
The configuration is the same as that of the optical disk reproducing apparatus 1 shown in FIG.

As shown in FIG. 2, the defect detection section 32 is composed of a comparator 33, and determines whether or not the DC signal S6 supplied from the servo signal processing section 11 and a rampage have occurred. The signal is compared with a level reference signal S11 set as a reference, and the comparison result thus obtained is sent to the RF signal processing unit 31 as a gate signal S12.

The defect detector 32 detects the supplied DC signal S
6, the magnitude of the amplitude of the DC signal S6 is compared based on the level reference signal S11 which is a set value. If the DC signal S6 is smaller than the level reference signal S11, the logic " Output an "H" level comparison signal,
When the DC signal S6 is larger than the level reference signal S11, a comparison signal of a logical "L" level is output, and these comparison signals thus obtained are used as the gate signal S12 in the switch 34 (in the RF signal processing unit 31). 2).

In actuality, in the optical disc reproducing apparatus 30, when reproducing a portion on the optical disc 7 where a scratch, dust, or the like exists, as shown in FIG. 3, a signal S3 (FIG. 3A)
Alternatively, the RF signal S5 (FIG. 3B) and the DC signal S6 (FIG. 3B) output from the band division unit 13 (FIG.
(C)) is affected by such scratches, dust and the like. In FIG. 3, the horizontal axis represents time.

The RF signal processing section 31 also provides an AC coupling section (hereinafter referred to as a first AC coupling section) 14 based on the gate signal S12 given from the defect detection section 32.
By performing integration processing on the runaway region of the RF signal S7 given by the above, the differential characteristic that causes the runaway is removed by multiplying the integral characteristic. And the RF signal processing unit 31
Converts the signal from which the rampage has been removed as described above into the RF signal S.
The signal 13 is sent to a binarizing circuit 18 constructed in the same manner as in the prior art.

That is, the RF signal processing unit 31 includes a buffer circuit 35 to which the RF signal S7 is given and a switch 34.
And an AC coupling unit 3 provided after the switch 34.
1, a path simply connecting the buffer circuit 35 and the switch 34 (hereinafter, referred to as a normal connection path) 37, and an integration circuit 3 having the same configuration as the normal connection path 37.
8 (hereinafter, this path is referred to as an integral connection path) 39.

The switch 34 of the RF signal processing unit 31
Is composed of an analog multiplexer, and the defect detection unit 32
The normal connection path 37 or the integration connection path 39 is selected as a connection path to the buffer circuit 35 based on the gate signal S12 given by the control circuit 30.

Specifically, when the gate signal S12 provided from the servo signal processing unit 11 is a logical "L" level comparison signal, the switch 34 selects the normal connection path 37 based on the gate signal S12, and selects And the buffer circuit 35 via the normal connection path 37.

On the other hand, the switch 34 is
In the case where the gate signal S12 given from 1 is a logical "H" level comparison signal, the integration connection path 39 is selected based on the gate signal S12, and the selected integration connection path 3 is selected.
9 and a buffer circuit 35.

At this time, the buffer circuit 35
When the connection path is switched based on the selection of the connection path by the switch 4, the mismatch between the buffer circuit 35 and the switch 34 due to the switching is absorbed. Thus, when sending the RF signal S7 supplied from the first AC coupling unit 14 to the switch 34, the buffer circuit 35 can suppress distortion generated in the waveform of the RF signal S7 due to such a mismatch or the like.

Subsequently, the buffer circuit 35 is connected to the switch 34.
The RF signal S7 supplied via the normal connection path 37 or the integration connection path 39 selected by the
To send to.

Here, the integration circuit 38 inserted in the integration connection path 39 is configured as shown in FIG. 4, and has an integration characteristic which is a property opposite to the differential characteristic of the first AC coupling section 14 described above. are doing. The integration connection path 39 is connected to the supplied R
By integrating the F signal S7, the fluctuation of the RF signal S7 caused by the differential characteristic is contained, and the RF signal S7 is transmitted to the second AC coupling unit 36 as the RF signal S13.

Next, the second AC coupling section 36 has the same configuration as that of the above-described first AC coupling section 14, and there is a possibility that a bias is applied to the supplied RF signal S13 by disturbance. Therefore, the RF signal S13 is again AC-coupled to generate an RF signal S14 whose amplitude center matches the slice level, and sends it to the binarization circuit 18.

Incidentally, since the second AC coupling section 36 receives the RF signal S13 in which the rampage is always contained via the normal connection path 37 or the integration connection path 39, the second AC coupling section 36 receives the RF signal S13.
The differential characteristic is not affected again on the signal S13.

In this way, the binarizing circuit 18 suppresses the center of the amplitude from being rubbed by the integration circuit 38 to suppress the runaway of the RF signal S7.
The slice level is easily made to follow the center of the amplitude of the signal S14.

The binarizing circuit 18 does not need to accurately follow the slice level in the ramping area of the RF signal S5 because the ramping area of the RF signal S5 does not originally include the data. What is necessary is just to have performance.

Further, the PLL 19 can maintain the synchronization with the RF signal S14 by suppressing the fluctuation of the slice level, and can finish the pull-in in a short time even after the synchronization with the RF signal S14 is lost.

(2) Operation and Effect of the Embodiment In the above configuration, the optical disk reproducing apparatus 30 uses the RF signal S5 and the DC signal S6 based on the signal S3.
Is generated, and the defect detector 32 compares the magnitude of the DC signal S6 with the level reference signal S11 to determine whether or not the RF signal S7 is rampant.

When determining that the DC signal S6 is larger than the level reference signal S11, the optical disk reproducing apparatus 30 leaves the RF signal S7 unprocessed via the normal connection path 37 and converts the RF signal S7 into a post-stage binarization circuit 18. And when it is determined that the DC signal S6 is smaller than the level reference signal S11, the R signal is transmitted through the integration circuit 38 of the integration connection path 39.
By performing an integration process on a rampage area generated in the F signal S7, a ramp generated based on the differential characteristic is removed by the integration characteristic, and the ramp obtained in this manner is corrected.
13 is sent to a binarization circuit 18 at the subsequent stage.

Therefore, according to the optical disk reproducing apparatus 30, the integration circuit 3 is used only during the period when the RF signal S7 is ramped.
8 through which the RF signal S7 is passed and the RF signal S7 having a stable waveform is always given to the binarization circuit 18,
The center of the amplitude of the RF signal S7 in the binarization circuit 18;
The slice level can be matched in a short period of time.

In the optical disk reproducing apparatus 30, since the RF signal S7 originally has no data due to scratches or dust existing on the optical disk 7 in the violent area, the slice level must be made to follow the violent area with high precision. There is no. On the contrary, in the optical disc reproducing apparatus 30, the movement of the slice level in the rampage area is reduced if the tracking precision of the slice level is not so high, and the slice level can be stabilized in a short period after the rampage area.

Then, the optical disk reproducing apparatus 30
As is clear from the experimental result shown in (2), by adding the integral characteristic to the RF signal S5 in which the ramping has occurred due to the differential characteristic, the RF signal without the integral characteristic is added.
Compared with the signal S5 (FIG. 7 (2)), rampage can be suppressed, and the pull-in period of the PLL 19 can be shortened. 5 and 7, the horizontal axis represents time.

Also, the optical disk reproducing apparatus 30 has the configuration shown in FIG.
As is evident from the experimental results shown in (5), by adding the integration characteristic to the RF signal S7 in which the rampage has occurred due to the differential characteristic, the center of the amplitude of the RF signal S7 after the rampage region is the conventional slice level. 8 (5), the binarization circuit 18 can easily adjust the slice level to the center of the amplitude of the RF signal S14. 6 and 8, the horizontal axis represents time.

According to the above configuration, the integrating circuit 38 is connected to the RF circuit.
By removing the differential characteristics generated in the signal S7, it is possible to shorten the period until the slice level matches the center of the amplitude of the RF signal S7, thus reducing data loss and improving data reproduction reliability. An optical disk reproducing device that can be improved can be realized.

(3) Other Embodiments In the above-described embodiment, the case where the integration circuit 38 having the integration characteristic is used as means for suppressing the runaway of the RF signal has been described, but the present invention is not limited to this. Any circuit or element having an integral characteristic may be used.

In the above embodiment, the case where the data reproducing apparatus is used as the optical disk reproducing apparatus 30 has been described. However, the present invention is not limited to this. May be used for the above device.

Furthermore, in the above-described embodiment, a case has been described in which a switch composed of an analog multiplexer is used as the transmission path conversion means. However, the present invention is not limited to this, and the transmission path can be converted according to a received signal. A switch is sufficient.

Further, in the above-described embodiment, a case has been described where two paths including a normal connection path and an integration path provided with an integration circuit are used as transmission paths.
The present invention is not limited to this, and a plurality of paths may be used as necessary, such as providing a plurality of integration paths having different effects due to the integration characteristics.

Further, in the above embodiment, the case where data is reproduced from the optical disk 7 has been described.
The present invention is not limited to this, and data may be reproduced from another medium such as a magneto-optical disk.

Further, in the above embodiment, the integration connection path 39 provided with the integration circuit 38 and the normal connection path 37 are configured to be switched by the switch 34, and when a signal having a differential characteristic is received. Although the case where the differential characteristic is canceled by switching to the integration connection path 39 has been described, the present invention is not limited to this, and the differential characteristic can be changed by changing the capacitance of the integration circuit 38 provided in the integration connection path 39. You may make it offset.

Further, in the above embodiment, the case where the RC integration circuit is used as the integration circuit 38 has been described. However, the present invention is not limited to this, and the RL integration circuit and the OP (Ope
rational Amplifier) An integrating circuit composed of an amplifier may be used.

Further, in the above embodiment, the case where the RC integration circuit is used as the integration circuit has been described. However, the present invention is not limited to this, and an RL integration circuit may be used.

Further, in the above-described embodiment, the case has been described where the disturbance of the DC signal generated from the sum signal used as the reproduction signal is detected and the switch is switched based on the detection result. However, the present invention is not limited to this. Instead, a ramp may be detected using another signal such as a sum signal or a servo signal, and the switch may be switched based on the detection result.

[0066]

As described above, according to the present invention, the binarizing means for binarizing an AC signal obtained by reading data recorded on a recording medium with the amplitude center of the AC signal as a slice level. And a first DC component removing means for removing a DC component from an AC signal, and a first signal characteristic given to the AC signal by the removing means for the AC signal from which the DC component has been removed. Second
Signal processing means for performing signal processing of the signal characteristic of (1), and either one of the AC signal from which the DC component has been removed by the removing means and the AC signal which has been subjected to signal processing by the signal processing means, are selectively supplied to the binarizing means. Selecting means for outputting, and controlling the selecting means to monitor the AC signal and to select the AC signal subjected to signal processing by the signal processing means only when the signal level of the AC signal fluctuates by a predetermined threshold or more. By providing the control means, it is possible to realize a data reproducing apparatus which can binarize with high accuracy and thus can significantly improve the reliability of data reproduced simply.

According to the present invention, an AC signal obtained by reading data recorded on a recording medium is
In the data reproducing method for binarizing the AC signal with the amplitude center as a slice level, a first step of removing a DC component from the AC signal, and an AC signal in which the DC component has been removed in the first step. A second step of performing signal processing of a second signal characteristic for canceling the first signal characteristic given to the signal, and selecting one of an AC signal from which a DC component has been removed and an AC signal subjected to the signal processing And a third step of monitoring the AC signal and binarizing the signal-processed AC signal only when the signal level of the AC signal fluctuates by a predetermined threshold or more. By doing so, it is possible to realize a data reproducing method that can binarize with high precision and thus can significantly improve the reliability of data that is simply reproduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an optical disc reproducing device according to the present embodiment.

FIG. 2 is a block diagram illustrating a configuration of an RF signal processing unit and a defect detection unit.

FIG. 3 is a schematic diagram showing a state of a reproduction signal of an optical disk having a defect.

FIG. 4 is a schematic diagram illustrating a configuration of an integration circuit.

FIG. 5 is a waveform chart showing an experimental result in the present embodiment.

FIG. 6 is a waveform chart showing an experimental result in the present embodiment.

FIG. 7 is a waveform chart showing an experimental result in the conventional embodiment.

FIG. 8 is a waveform chart showing an experimental result in the conventional embodiment.

FIG. 9 is a block diagram showing a configuration of an optical disk reproducing device according to a conventional embodiment.

FIG. 10 is a schematic diagram illustrating a configuration of an AC coupling unit.

FIG. 11 is a schematic diagram illustrating a state of each signal.

FIG. 12 is a schematic diagram illustrating how a digital signal is generated.

[Explanation of symbols]

1, 30 optical disk reproducing device, 2 optical pickup unit, 7 optical disk, 11 servo signal processing unit,
13 ... band division unit, 14, 36 ... AC coupling unit, 18
... Binarization circuit, 19 PLL, 31 RF signal processing unit 32 defect detection unit 33 comparator 3
4 switch, 35 buffer circuit, 37 normal connection path, 38 integration circuit, 39 integration connection path.

Claims (6)

[Claims] 1. A data reproducing apparatus having a binarizing means for binarizing an AC signal obtained by reading data recorded on a recording medium with a center of an amplitude of the AC signal as a slice level. First DC component removing means for removing a DC component from the signal, and a predetermined second signal for canceling a first signal characteristic given to the AC signal by the removing means with respect to the AC signal from which the DC component has been removed. Signal processing means for performing characteristic signal processing; and selectively one of the AC signal from which the DC component has been removed by the removal means and the AC signal subjected to the signal processing by the signal processing means. Selecting means for outputting to the binarizing means; and monitoring the AC signal, and the signal processing means performs the above only when the signal level of the AC signal fluctuates by a predetermined threshold or more. Control means for controlling the selection means so as to select the AC signal subjected to the signal processing. 2. The data reproducing apparatus according to claim 1, wherein said first signal characteristic is a differential characteristic, and said second signal characteristic is an integral characteristic. 3. A DC component removing means provided between said selecting means and said binarizing means, for removing a DC component from said AC signal with respect to said AC signal output from said selecting means. 2. The data reproducing apparatus according to claim 1, wherein the data is reproduced. 4. A data reproducing method for binarizing an AC signal obtained by reading data recorded on a recording medium with the amplitude center of the AC signal as a slice level, wherein a DC component is removed from the AC signal. A first step of determining a predetermined second signal characteristic of the AC signal from which the DC component has been removed to cancel the first signal characteristic given to the AC signal when removing the DC component from the AC signal; A second step of performing signal processing; and selectively selecting one of the AC signal from which the DC component has been removed and the AC signal having been subjected to the signal processing.
A third step of monitoring the AC signal and binarizing the AC signal subjected to the signal processing only when the signal level of the AC signal fluctuates by a predetermined threshold or more. A data reproducing method characterized in that the data is reproduced. 5. The data reproducing method according to claim 4, wherein said first signal characteristic is a differential characteristic, and said second signal characteristic is an integral characteristic. 6. In the second step, after the first signal characteristic given to the AC signal is canceled using the predetermined second signal characteristic, the AC signal that has been subjected to the cancellation processing is re-started. 5. The data reproducing method according to claim 4, wherein a DC component is removed.