JP3075353B2 - Information recording / reproducing apparatus and information recording / reproducing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording / reproducing apparatus or information recording / reproducing method for accurately extracting high-density recording information on a recording medium by a mark edge recording method or the like, and more particularly, to a reduction in size and weight. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording / reproducing apparatus and method capable of accurately extracting information with the apparatus.

[0002]

2. Description of the Related Art There are a mark position recording / reproducing method and a mark edge recording / reproducing method as information recording / reproducing methods using an optical disk or the like as a recording medium. 2. Description of the Related Art In recent years, a mark edge recording method in which information is provided at a leading edge and a trailing edge of a recording mark has attracted attention as a technique that enables high-density recording. A method of reproducing information recorded by the mark edge recording method involves slicing at an arbitrary reference level,
There are a slice detection type for performing a value conversion and a second-order differentiation detection type for detecting a zero-crossing point in order to perform second-order differentiation of a read signal and insert the read signal at an edge position.

In the mark edge reproducing method by the second-order differential detection type, various noises (medium noise, LD noise, circuit noise, etc.) which are problematic in the reading time are emphasized by differentiation, or the waveform is not good. There is a problem that the inflection point of the reproduction signal does not correspond to the edge position of the recording mark due to the influence of the distortion.

A technique for solving such a problem is described in, for example, Japanese Patent Application Laid-Open No. H4-232659.
In the mark edge reproducing method using the second-order differential detection type, amplitude limiting means is used. However, by using the amplitude limiting means, the margin for DC fluctuation, which is the original superiority of the mark edge reproducing method using the second-order differential detection type, is reduced.

In the slice detection type mark edge reproducing method, a slice level value is an important parameter for accurately reproducing recorded information on a recording medium. However, almost all of the reproduction system circuit is not constituted by a DC coupling circuit, and the bias point or D
In order to solve problems such as C offset, an AC coupling circuit configuration is employed.

In such a configuration, when a beam scans from an area without a recording mark, such as a defect in a recording medium or a GPA length, to an area with a recording mark, or abruptly, such as immediately after recording / erasing, a reproduction signal is reproduced. When the DC component fluctuates, a transient occurs due to the transient frequency response in the time constant of the AC coupling circuit. Transient response of the reproduced waveform such as a transient becomes an obstacle in determining the binarized slice level.

As described above, when reproducing the information recorded at the mark edge by using either the second-order differential detection type or the slice detection type, if the transient is large due to abrupt DC fluctuation, the information is obtained. The detection accuracy of the signal is reduced, and the reproduction error rate cannot be reduced. To solve this problem, reduce the time constant of the AC circuit to reduce the section in which a transient occurs, or conversely, increase the time constant of the AC circuit to reduce the amount of change in the transient. There are, but
Such countermeasures may cause problems such as envelope fluctuations in the reproduced signal due to the influence of the duty fluctuations of the recording data pattern, or saturation of the reproduction amplifier due to insufficient dynamic range. May increase the error rate.

A technique for reducing such a problematic transient is described in, for example, Japanese Patent Application Laid-Open No. 5-334755. Further, a technology for absorbing a transient is described in, for example, Japanese Patent Application Laid-Open No. 8-273163.

That is, in the means described in Japanese Patent Application Laid-Open No. 5-334755, a transient reduction circuit is provided between the sum-difference signal switching circuit and the AGC amplifier circuit to reduce a transient generation section using an arbitrary gate. ing.

In the means described in Japanese Patent Application Laid-Open No. Hei 8-273163, first, as shown in FIG. 5, an information detection unit 1 first extracts information from a recording medium using an optical head and generates an electric signal based on a current. Output. Next, this electric signal is converted into a voltage by the current-voltage conversion circuit 2 and output as a differential signal. This output is sent to the transient absorber 50 via the coupling capacitor.

The transient absorbing section 50 is formed by connecting an initial voltage generating circuit 51 and a charging current control circuit 52 in series, and by connecting the output to an AGC amplifier circuit 53, the current / voltage converting circuit 2 is connected via a coupling capacitor. It is AC-coupled to the AGC amplifier circuit 53. On the other hand, the output data of the AGC amplification circuit 53 is sent from the binarization circuit 55 via the waveform equalization circuit 54.

On the other hand, the comparator 56 compares each reproduction voltage of the differential signal output from the AGC amplifier circuit 53, and the charge current control circuit 52 of the transient absorption unit 50 receiving the result compares the reproduction voltages of both with AC grant. The transient is automatically absorbed by controlling the charging and discharging of each of the coupling capacitors based on the comparison output so as to match the above.

[0013]

In the conventional information recording / reproducing apparatus described above, the means described in Japanese Patent Laid-Open No. Hei 5-334755 discloses a transient reduction circuit for reducing a transient generation section using an arbitrary gate. However, this configuration has a problem in that since abrupt transients do not completely disappear, there is a limit to always extracting an accurate information signal.

In the means described in JP-A-8-273163, the coupling capacitor for the AC coupling circuit is only one stage on the input side of the transient absorbing section. In the reproduction system circuit, multiple stages of AC coupling circuits are configured in series, so if transients are absorbed only by the first stage amplification circuit coupling capacitor, new transients will occur when passing through the latter stage AC coupling circuit Therefore, there is a problem that an accurate information signal cannot be normally extracted.

As described above, since all the reproduction circuits in the apparatus are usually constituted by LSIs such as a read channel, it cannot be realized by only one stage of a DC coupling circuit or an AC coupling circuit. It has a coupling circuit configuration. In the reproduced signal waveform in this configuration, transient components having various time constants are generated and superimposed each time the signal passes through each AC circuit, so that the waveform responsiveness due to the AC time constant is complicated immediately before the reproduced pulsing circuit. It becomes.

With respect to such a condition, the method of controlling the charge and discharge of the coupling capacitor of the AC coupling circuit unit to reduce or absorb the transient amount as described above cannot sufficiently suppress the transient, If the control is to be suppressed, the control becomes complicated.

On the other hand, if a charge / discharge control circuit is added to each stage of the AC coupling circuit so that the waveform responsiveness due to the transient is not complicated, the circuit scale becomes enormous.

To solve this problem, it is conceivable to perform charge / discharge control not only on the first stage but also on the coupling capacitors of all the AC coupling circuits. However, in this case, the circuit scale becomes large, and it is difficult to reduce the size of the device. In addition, if charge / discharge control is performed only on the coupling capacitor of the AC coupling circuit unit immediately before pulse formation, the information signal passes through many stages of the AC coupling circuit, so the charge / discharge control mechanism for the capacitor can be simplified. There is a problem that it is difficult to realize the circuit with a simple circuit configuration.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to suppress information on abrupt transients so that accurate information can always be extracted, and an information recording apparatus capable of reducing the size and weight of the apparatus. It is to provide an apparatus and a method for reproduction.

That is, the present invention provides an information recording / reproducing method capable of accurately extracting high-density recorded information on a recording medium by a mark edge recording method or the like even in a reproduction environment with a low SN ratio or in a state where there is a sudden DC fluctuation. And an apparatus for the same. In particular, the apparatus and method according to the present invention reduce the reproduction error rate by suppressing the amount of transients that occur when a defect on a recording medium or a sudden fluctuation in the reproduction signal occurs, such as after recording or erasure. It is.

[0021]

An information recording / reproducing apparatus according to the present invention comprises: information detecting means for extracting information on a recording medium as a signal; and a signal which is converted by the information detecting means into a voltage to obtain a differential signal. Current-voltage conversion means, and AC amplification means for AC-coupling a differential signal output from the current-voltage conversion means via a capacitor to amplify an input reproduction signal amplitude and outputting the amplified signal as a differential signal. A waveform equalizing unit that performs resolution reduction correction due to intersymbol interference on the differential signal output from the amplifying unit and outputs the resulting signal as a differential signal, and a differential signal output from the waveform equalizing unit to determine the magnitude of a transient. A transient amount detecting means for detecting from the difference between the reproduction waveform amplitude center levels and outputting as a detection level difference, and a presence or absence of a reproduction margin for the transient. Storage means for storing in advance any allowable level difference, and comparing means for comparing the detection level difference output from the transient amount detection means with the allowable level difference extracted from the storage means to determine whether the level is positive or negative. Shift control means for performing shift control on the level of the differential signal output from the waveform equalization means in accordance with the positive / negative determination signal output from the comparison means, and level shift control output from the shift control means Reproduction pulse generating means for generating a pulse corresponding to the edge of the recording mark from the signal thus obtained.

In the information recording / reproducing apparatus, there is provided a transient signal for averaging differential signals on the positive polarity side and the negative polarity side input to the transient amount detecting means by sampling and holding each of a peak value and a bottom value. Absorption means may be provided.

One specific example of the reproduction pulse generating means is an amplitude limiting means for limiting the amplitude of a differential signal input from the waveform equalizing circuit, and a signal for each of the first and second derivatives. Two differentiating means for generating, a changing direction extracting means for extracting a changing direction from the first order differential signal, a zero cross comparing means for extracting zero crossing edge information from the second order differential signal, and a changing direction extracting means. Pulse generating means for taking in the obtained change direction and the edge information of the zero cross obtained from the zero cross comparing means, generating a binarized pulse and outputting it as a reproduction pulse.

One specific example of the storage means is to store an allowable level difference of a transient amount according to a degree of amplitude limitation of the reproduction pulse generating means, and the allowable level difference can be changed. .

The information recording / reproducing method according to the present invention comprises:
A storage means for storing in advance any allowable level difference defined by the presence or absence of a reproduction margin for a transient, extracting information on a recording medium as a signal, and then converting the extracted signal into a voltage to obtain a differential signal Then, the differential signal is AC-coupled through a capacitor to amplify the input reproduction signal amplitude, and then, following the waveform equalization procedure of correcting the resolution reduction of the amplified differential signal due to intersymbol interference, Comparing the magnitude of the amplitude center level difference detected from the reproduced waveform amplitude DC component obtained between the corrected differential signals and the allowable level difference extracted from the storage means,
When the detection level difference is larger than the allowable level difference, the level shift is performed to absorb the transient amount, and when the detection level difference is equal to or smaller than the allowable level difference, the signal is output without correction.

After the waveform equalization procedure, the peak value and the bottom value of the corrected differential signal on the positive polarity side and the corrected differential signal on the negative polarity side are respectively averaged by sample-and-hold. An information recording / reproducing method for obtaining the magnitude of the detection center level difference of the obtained reproduced waveform amplitude DC component can be added.

Further, one specific example of the range of any allowable level difference is a simple second-order differential detection type mark edge reproducing method that does not apply the amplitude limitation having a large margin to the change in the transient amount. It becomes wider and narrower with the increase in the degree of amplitude limitation provided as a measure for improving the S / N ratio of the mark edge reproduction method, and becomes zero in the slice detection type mark edge recording / reproduction method with no margin for a change in the transient amount. Is to be set.

With such a configuration, a state where the level difference of the DC component between the differential signals at the final stage in the AC coupling circuit exceeds the range of the transient amount allowable in generating the reproduction pulse is detected, and Since the transient amount can always be kept within an allowable range by such a simple level shift control circuit, the reproduction error rate can be reduced.

[0029]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a functional block diagram showing an embodiment of the present invention. In the information recording / reproducing apparatus shown in FIG. 1, the information detection unit 1, the current-voltage conversion circuit 2, the AC amplification circuit 3, the filter circuit 4, the waveform equalization circuit 5, the transient amount detection circuit 6, the storage circuit 7, and the comparison circuit 8, a level shift control circuit 9, a transient absorption circuit unit 20, and a reproduction pulse generation circuit unit 30 are provided.

The information signal extracted by the optical head by the information detection unit 1 passes through a series-connected current-voltage conversion circuit 2, an AC amplification circuit 3, a filter circuit 4, and a waveform equalization circuit 5, and outputs a differential signal. Output as A coupling capacitor is inserted on the output connection side of each of the current-voltage conversion circuit 2, the AC amplification circuit 3, the filter circuit 4, and the waveform equalization circuit 5.

The differential signal output from the waveform equalizing circuit 5 via the coupling capacitor is sent to the transient amount detecting circuit 6 via the level shift control circuit 9 and the transient absorbing circuit section 20. Outputs of the transient amount detection circuit 6 and the storage circuit 7 are connected to a comparison circuit 8, and an output of the comparison circuit 8 is sent to a level shift control circuit 9. The output of the level shift control circuit 9 is output by the reproduction pulse generation circuit unit 30 as a generated pulse signal.

That is, the information detecting section 1 extracts information recorded on the recording medium by the optical head, converts the information into a current, and generates a read signal. The current-voltage conversion circuit 2 converts the read signal of the information detection unit 1 into a voltage. The AC amplifier circuit 3 and the filter circuit 4 have a differential configuration and are provided to reduce the influence of disturbance or high-frequency noise superimposed on the read signal. The waveform equalization circuit 5 is of a linear phase type, and reduces intersymbol interference due to a decrease in resolution of the optical system.

The transient amount detecting circuit 6 detects the difference between the amplitude center levels of the differential signal waveform output from the waveform equalizing circuit 5. In FIG. 1, a differential signal waveform is received via the transient absorption circuit section 20. The transient absorption circuit section 20 will be described later with reference to FIG.

The storage circuit 7 stores an arbitrary allowable level difference defined in advance depending on whether or not there is a reproduction margin for a transient. The comparison circuit 8 compares the detection level difference of the transient amount detection circuit 6 and the storage level difference of the storage circuit 7 to determine whether it is positive or negative.

The level shift control circuit 9 performs a level shift according to the positive / negative judgment of the comparison circuit 8 and performs a level control so that the output signal of the comparison circuit 8 becomes zero. The reproduction pulse generation circuit unit 30 generates a pulse corresponding to the edge portion of the recording mark from the reproduction signal waveform whose level is controlled by the level shift control circuit 9, and outputs the pulse to the outside as a reproduction pulse signal.

The allowable range of an arbitrary level difference stored in the storage circuit 7 in advance is determined by the reproduction pulse generation circuit 30.
And it is determined by the size of the reproduction margin with respect to the change of the transient amount. Accordingly, in the reproduction method of the slice detection type having a small reproduction margin with respect to the change of the transient amount, the allowable level difference is set to a value close to zero as much as possible, while the reproduction of the second-order differential detection type having the large reproduction margin with the change of the transient amount In the method, the range of the allowable level difference is set to be wide.

With the above-described configuration, a state where the level difference of the DC component between the differential signals at the final stage in the AC coupling circuit exceeds the range of the transient amount allowable in the reproduction pulse generating circuit unit 30 is detected. Since the transient amount can always be kept within an allowable range by such a simple level shift control circuit 9, the reproduction error rate can be reduced. Therefore, complicated charge / discharge control as in the related art is not required, and the circuit scale does not increase. Therefore, when the device is implemented, reduction in size and weight and reduction in power consumption can be realized.

Next, the transient absorption circuit section 20 will be described with reference to FIG. 1 and FIG.

The transient absorption circuit section 20 detects the amount of transient from the differential signal output from the waveform equalization circuit 5 of FIG. 1 and suppresses only the transient that cannot be saved by the reproduction pulse generation circuit section 30. Yes,
Peak value sample / hold circuits 21, 23, bottom value sample / hold circuits 22, 24, and averaging circuit 2
5, 26 are provided.

The peak value sample and hold circuit 21 samples and holds the peak value of the positive polarity signal amplitude output from the waveform equalization circuit 5. The bottom value sample and hold circuit 22 samples and holds the bottom value of the positive polarity signal amplitude. The peak value sample and hold circuit 23 samples and holds the peak value of the negative polarity signal amplitude output from the waveform equalization circuit 5. The bottom value sample / hold circuit 24 samples and holds the bottom value of the negative polarity signal amplitude. The averaging circuit 25 extracts the center value of the signal amplitude based on the detection of the peak value and the bottom value of the positive polarity signal amplitude output from the waveform equalization circuit 5. The averaging circuit 26 includes the waveform equalizing circuit 5
The center value of the signal amplitude is extracted based on the detection of the peak value and the bottom value of the negative polarity signal amplitude output from.

The transient amount detection circuit 6 determines the magnitude of the transient by calculating the level difference between the center values of the averaging circuits 25 and 26. The storage circuit 7 and the comparison circuit 8 have already been described, and will not be described.

When the comparison circuit 8 determines that the level difference between the output signals from the transient amount detection circuit 6 is large, the level shift control circuit 9 performs waveform equalization so that the output signal of the comparison circuit 8 becomes zero. While the level shift control of the output signal of the circuit 5 is performed, if the level difference of the output signal from the transient amount detection circuit 6 is determined to be small or zero, no correction is performed, and the output of the waveform equalization circuit 5 is output. Outputs the same signal as the signal.

Next, FIG. 3 shows an example of a block configuration in the case where an edge extraction circuit of the second order differential detection type with an amplitude limit is applied as the reproduction pulse generation circuit unit 30 of FIG. 1, and this will be described.

In FIG. 3, as in FIG. 1, the information detecting section 1 extracts information recorded on the recording medium by the optical head and converts the information into a read signal. The current-voltage converter 2 converts the read signal of the information detector 1 into a voltage in a differential configuration. The AC amplification circuit 3 amplifies the voltage-converted read signal, and the linear-phase waveform equalization circuit 5 that receives the signal via the filter circuit 4 reduces intersymbol interference due to a decrease in resolution of the optical system. After the correction, the output is supplied to the reproduction pulse generation circuit 3 via the level shift control circuit 9 as described above.
Send to 0.

The reproduction pulse generating circuit 30 includes an amplitude limiting circuit 31, differentiating circuits 32 and 34, a change direction extracting circuit 33,
Zero cross comparison circuit 35 and binarized pulse generation circuit 3
6.

The signal corrected by the waveform equalizing circuit 5 is amplitude-limited by an amplitude limiting circuit 31, and the amplitude-limited signal is differentiated by a differentiating circuit 32 to obtain a first-order differential signal. From the first-order differential signal obtained by the differentiating circuit 32, the change direction extracting circuit 33 outputs positive and negative slice levels (+ VT, -V
A binary signal in the signal change direction is obtained by the level comparison of T).

On the other hand, the differentiating circuit 34
The second-order differential signal is obtained by differentiating the second-order differential signal. The zero cross comparison circuit 35 extracts the inflection point signal of the read signal as edge information based on the second derivative signal. The binarized pulse generation circuit 36 outputs a reproduction pulse signal to the outside from the binarized signal of the change direction extraction circuit 33 and the edge information of the zero cross comparison circuit 35.

Next, the circuit operation in FIG. 1 will be described with reference to FIG. 1 and FIG. 3 and FIG.

FIG. 4A is a waveform diagram showing an example of a reproduced signal waveform representing a transient, and FIG. 4B shows an example of an amplitude center level between differential signals and an allowable range of a transient amount in the reproduced signal waveform. Waveform diagram and FIG.
(C) is a waveform diagram showing an example of an amplitude center level and a transient amount allowable range only in the positive polarity of the reproduction signal waveform after the level shift.

The information recorded on the recording medium extracted by the optical head in the information detecting section 1 is read by the current-voltage conversion circuit 2,
By passing through a multi-stage AC coupling circuit composed of an AC amplification circuit 3, a filter circuit 4, and a waveform equalization circuit 5, FIG.
As shown in (a), the reproduced signal waveform of the information exhibits a transient time response, that is, a transient.

The transient correlation between the positive and negative differential signals is inverted with respect to each other, and as the amount of transient increases, the amplitude between the differential signals increases. The center level difference will widen. Therefore, the amplitude center level as shown in FIG. 4B is detected from the differential reproduction signal waveform in FIG. 4A, and the magnitude of the transient amount is recognized by comparing the levels of the polarities with each other. be able to. If the difference in the amplitude center level between the differential signals can be reduced by the level shift control circuit 9, the transient amount can be suppressed.

In this example, a second-order differential detection type edge extraction method having an amplitude limiting circuit function is a specific example. Depending on the magnitude of the transient amount, the amplitude limiting circuit can delete up to the original edge point. There is. The amount of transient suppression is determined by the magnitude of the reproduction margin for a change in the transient in the reproduction pulse generation circuit 30. Further, this magnitude differs depending on the amplitude limiting amount and the degree of the amplitude limiting symmetry.

Therefore, the allowable range of the transient amount stored in the storage circuit 7 in advance is determined from the amplitude limit amount and the amplitude limit symmetry, which are the parameters indicating the degree of the amplitude limit.

Therefore, assuming that the allowable range of the transient amount is set as shown in FIG. 4 (b), if the allowable range of the transient amount is set,
Level shift control as shown in FIG. 4C is performed. Since the transient amount allowable range in FIG. 4C shows only one signal of the differential signal, it is equivalent to 許 容 of the allowable range shown in FIG. 4B.

As described above, the level shift control circuit 9
The amplitude center level difference between the differential signals as shown in FIG. 4B is equal to the allowable transient amount range, or
The level is corrected so as to be smaller, and even if a steep transient occurs, such as immediately after recording or erasing or immediately after a recording medium defect, the original edge extraction point is not deleted in the amplitude limiting circuit 31. Information can be accurately extracted.

[0057]

As described above, according to the present invention, the following effects can be obtained.

The first effect is that even if a steep transient such as immediately after recording or erasing or immediately after a recording medium defect occurs, the transient can be suppressed in accordance with the degree of amplitude limitation. As a result, accurate information can be extracted.

The reason for this is that the level difference between the reproduced waveform amplitudes between the differential signals is compared with an arbitrary allowable level difference defined by the presence or absence of a reproduced margin for a transient stored in advance to determine whether the level is positive or negative. This is because when the level difference is larger than the allowable level, the level shift is performed within the allowable range, and when the detected level difference is smaller than the allowable level, the level shift control is performed to perform no correction. Specifically, by combining the transient suppression method in the level shift control method according to the amplitude limit amount and the edge extraction method by the second-order differentiation with the amplitude limit circuit, the original should be extracted even if the transient amount increases. This is because the edge extraction point is suppressed within the range of the output amplitude of the amplitude limiting circuit, and the edge information can be reliably extracted from the output signal waveform by the second-order differentiation.

The second effect is that the size and size of the device technology are small.
That is, weight reduction and low power consumption can be realized.

[0061] The reason is conventionally adopting a DC coupling circuit configured new transients does not occur at a later stage for thereby suppressing transients in the charge and discharge control of the AC coupling circuit of the first stage, or pulsed just before In contrast to providing a complicated charge / discharge control circuit because the transient is suppressed by the charge / discharge control of the AC coupling circuit of the present invention, in the present invention, the transient can be suppressed with a simple level shift circuit and a storage circuit. It is. Furthermore, since the transient suppression uses a simple level shift circuit in the AC coupling circuit just before pulsing instead of controlling the charge and discharge of the AC coupling circuit, this transient is suppressed even if the transient behavior is complicated. Because you can.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an embodiment of the present invention.

FIG. 2 is a functional block diagram illustrating one embodiment of a transient absorption circuit unit in FIG.

FIG. 3 is a functional block diagram illustrating one embodiment of a reproduction pulse generation circuit section of FIG. 1;

FIG. 4 is a waveform chart for explaining the operation of FIG. 1;

FIG. 5 is a functional block diagram showing an example of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Information detection part 2 Current-voltage conversion circuit 3 AC amplification circuit 4 Filter circuit 5 Waveform equalization circuit 6 Transient amount detection circuit 7 Storage circuit 8 Comparison circuit 9 Level shift control circuit 20 Transient absorption circuit parts 21 and 23 Peak value sample hold circuit 22, 24 Bottom value sample and hold circuit 25, 26 Averaging circuit 30 Reproduction pulse generation circuit unit 31 Amplitude limiting circuit 32, 34 Differentiating circuit 33 Change direction extraction circuit 35 Zero cross comparison circuit 36 Binarized pulse generation circuit

Claims (7)

(57) [Claims] 1. An information detecting means for extracting information on a recording medium as a signal, a current-voltage converting means for converting a signal extracted by the information detecting means into a voltage and outputting the voltage as a differential signal; AC amplification means for AC-coupling the differential signal output from the means via a capacitor, amplifying the amplitude of the input reproduction signal and outputting the amplified signal as a differential signal, and intersymbol interference for the differential signal output from the AC amplification means A waveform equalizing means for performing a resolution reduction correction accompanying the above and outputting as a differential signal, and a magnitude of a transient is detected from a difference level of a reproduced waveform amplitude center level between the differential signals output from the waveform equalizing means. A transient amount detecting means for outputting as a difference, and a memory means for previously storing an arbitrary allowable level difference defined by the presence or absence of a reproduction margin for the transient. Comparing means for comparing the detection level difference output from the transient amount detecting means with the allowable level difference extracted from the storage means to determine whether the level is positive or negative; and a positive / negative determination signal output from the comparing means. Shift control means for performing shift control on the level of the differential signal output from the waveform equalization means; and a pulse corresponding to the edge of the recording mark from the level-shift-controlled signal output from the shift control means. An information recording / reproducing apparatus comprising: a reproducing pulse generating means for generating the information. 2. A transient absorbing means according to claim 1, wherein the differential signal on the positive polarity side and the negative polarity side input to the transient amount detecting means are averaged by sampling and holding the peak value and the bottom value respectively. An information recording / reproducing device, comprising: 3. The reproducing pulse generating means according to claim 1, wherein said reproducing pulse generating means generates amplitude limiting means for limiting an amplitude of a differential signal input from said waveform equalizing circuit, and generates first and second order differential signals. Two differentiating means, a change direction extracting means for extracting a change direction from the first order differential signal, a zero cross comparing means for extracting zero cross edge information from the second order differential signal, and a change direction extracting means obtained from the change direction extracting means. An information recording / reproducing apparatus comprising: pulse generating means for taking in the change direction and zero-cross edge information obtained from the zero-cross comparing means, generating a binarized pulse, and outputting it as a reproduced pulse. 4. The apparatus according to claim 1, wherein said storage means stores an allowable level difference of a transient amount according to a degree of amplitude limitation of said reproduction pulse generating means, and said allowable level difference can be changed. Information recording and reproducing device. 5. A storage means for previously storing an arbitrary allowable level difference defined by the presence or absence of a reproduction margin for a transient, extracting information on a recording medium as a signal, and then converting the extracted signal to a voltage. A differential signal, and then AC-couple the differential signal via a capacitor to amplify the amplitude of the input reproduction signal, and then correct the amplified differential signal for a reduction in resolution due to intersymbol interference, etc. Following the conversion procedure, the magnitude of the detected level difference of the amplitude center level detected from the DC component of the reproduced waveform obtained between the corrected differential signals is compared with the allowable level difference extracted from the storage means, and the detection is performed. If the level difference is larger than the permissible level difference, a level shift is performed to absorb the transient amount, and if the detected level difference is smaller than the permissible level difference, it is output without correction. An information recording / reproducing method, comprising: 6. The method according to claim 5, wherein, after the waveform equalization procedure, the peak value and the bottom value of each of the corrected differential signals on the positive polarity side and the negative polarity side are averaged by sample and hold.
An information recording / reproducing method, wherein a magnitude of a detection center level difference of a reproduced waveform amplitude DC component obtained between differential signals is obtained. 7. The mark edge reproducing method according to claim 5, wherein an arbitrary allowable level difference range is wider as a simple second-order differential detection type mark edge reproducing method that does not apply an amplitude limit having a large margin to a change in a transient amount. In the slice detection type mark edge recording / reproducing method, which becomes narrower with an increase in the amplitude limit provided as a measure for improving the S / N ratio of the mark edge reproducing method and has no margin for a change in the transient amount, the value is set to zero. An information recording / reproducing method, comprising: