JP4289773B2 - Apparatus for reproducing magnetic recording data - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for reducing a reproduction error due to the influence of variation or fluctuation in the amplitude of a signal output from a magnetic head in a reproducing apparatus for reproducing data recorded on a magnetic recording medium such as a magnetic card.
[0002]
[Prior art]
Reproduction of data recorded on a magnetic recording medium such as a magnetic card is performed by relatively moving the magnetic head in contact with the magnetic recording surface of the medium to change the magnetic strength of the magnetic recording surface from the magnetic head. A signal whose amplitude changes according to the output signal is output and demodulated based on the period of the output signal.
[0003]
However, since the output level of the magnetic head is generally low, it is necessary to amplify the output signal of the magnetic head to a level that can be demodulated. Further, the magnetic holding force of the magnetic recording surface of the magnetic recording medium varies from medium to medium, and decreases with time.
[0004]
For this reason, as shown in FIG. 10, in the conventional reproducing apparatus 10, the magnetic head 11 in contact with the magnetic recording surface 1a of the magnetic recording medium 1 on which data is magnetically recorded is relatively moved to move the magnetic recording surface 1a. A signal corresponding to the change in magnetism is output, this output signal is amplified by the gain-controllable amplifier 12 and output to the demodulation circuit 13, and the gain of the amplifier 12 is controlled by the gain control unit 14, and the output signal I am trying to stabilize the amplitude.
[0005]
Here, the gain control unit 14 includes a detection circuit 15 that detects the output signal of the amplifier 12, a low-pass filter 16 that detects an average value of the output of the detection circuit 15, and a control unit 17. When the average value of the amplitude of the output signal of the amplifier 12 is larger than the predetermined value, the control means 17 lowers the gain of the amplifier 12, and when the obtained average value of the amplitude is smaller than the predetermined value, the control means 17 The gain is increased and control is performed so that the average value of the amplitude always approaches a predetermined value.
[0006]
[Problems to be solved by the invention]
However, in the conventional reproducing apparatus that controls the gain by obtaining the average value of the amplitude of the output signal of the amplifier 12 by the low-pass filter 16 as described above, the response to the fluctuation in the amplitude of the signal is slow, so that reading of the magnetic recording medium 1 Therefore, it takes a long time for the amplitude of the signal input to the demodulation circuit 13 to be stabilized after the signal is output from the magnetic head 11, and the initial input portion of the signal cannot be demodulated correctly.
[0007]
In order to prevent this, it is conceivable to increase the number of dummy data to be inserted in order to synchronize before the original data that needs to be read and write it on the magnetic recording medium. However, the recording capacity is small like a magnetic card. In some cases, the increase in the number of invalid dummy data results in a substantial decrease in the original data recording amount.
[0008]
An object of the present invention is to solve this problem and provide a reproducing apparatus for magnetic recording data that can quickly stabilize the amplitude of a signal input to a demodulation circuit.
[0009]
[Means for Solving the Problems]
  In order to achieve the above object, a reproducing apparatus for magnetic recording data according to claim 1 of the present invention comprises:
  A magnetic head that moves relative to a magnetically recorded medium and outputs a signal corresponding to a change in magnetism of the magnetic recording surface of the medium;
  An amplifier capable of gain control for amplifying an output signal of the magnetic head;
  A gain control unit that controls the gain of the amplifier based on a signal output from the amplifier and adjusts the amplitude of the signal output from the amplification within a predetermined range;
  In a magnetic recording data reproducing apparatus comprising: a demodulating circuit that demodulates data recorded on the medium based on a period change of a signal output from the amplifier;
  The gain controller is
  A first comparator for comparing a first threshold value set within an allowable amplitude range of an input signal with which the demodulation circuit can normally demodulate magnetic recording data and a signal output from the amplifier;
  A second comparator that compares a signal that is output from the amplifier with a second threshold value that is greater than the first threshold value within the allowable amplitude range;
  Based on the timing at which the outputs of the first comparator and the second comparator change,A time difference from when the signal output from the amplifier exceeds the first threshold value until it exceeds the second threshold value is determined, and the time difference is calculated.Amplitude correspondence value corresponding to the amplitude of the signal output from the amplifierAsAn amplitude corresponding value detecting means for detecting;
  Control means for controlling the gain of the amplifier so that the amplitude corresponding value detected by the amplitude corresponding value detecting means approaches a reference value set in advance.
[0010]
  A magnetic recording data reproducing apparatus according to claim 2 of the present invention is the magnetic recording data reproducing apparatus according to claim 1,
  The control means includes
  The relationship between the amplitude corresponding value output by the amplitude corresponding value detecting means for each moving speed of the medium with respect to the magnetic head, and the gain variable coefficient of the amplifier necessary for matching the amplitude corresponding value to the reference value A storage table for storing in advance,
  Means for determining a relative moving speed of the medium with respect to the magnetic head from a time between peaks of an initial read signal of the magnetic head with respect to the medium;
  By determining a gain variable coefficient corresponding to the amplitude corresponding value from the storage table corresponding to the determined relative movement speed, and setting a new gain obtained by multiplying the current variable by the gain variable coefficient in the amplifier. , And control so that the amplitude corresponding value matches the reference value.
  A magnetic recording data reproducing apparatus according to claim 3 of the present invention is the magnetic recording data reproducing apparatus according to claim 1,
  The control means includes
  When the moving speed of the medium with respect to the magnetic head is a reference speed, the amplitude corresponding value output by the amplitude corresponding value detecting means and the gain variable of the amplifier necessary for matching the amplitude corresponding value with the reference value A storage table for storing the relationship with the coefficients in advance;
  Means for determining a relative moving speed of the medium with respect to the magnetic head from a time between peaks of an initial read signal of the magnetic head with respect to the medium;
  Means for obtaining a ratio between the obtained relative movement speed and the reference speed, and further multiplying the amplitude correspondence value by this ratio to obtain a new amplitude correspondence value;
  By detecting a gain variable coefficient corresponding to the newly obtained amplitude corresponding value from the storage table and setting a new gain obtained by multiplying the current variable by the gain variable coefficient, the amplitude corresponding value detection The amplitude corresponding value output by the means is controlled so as to coincide with the reference value.
[0011]
  Further, the claims of the present invention4Magnetic recording data playback device,
  A magnetic head that moves relative to a magnetically recorded medium and outputs a signal corresponding to a change in magnetism of the magnetic recording surface of the medium;
  An amplifier capable of gain control for amplifying an output signal of the magnetic head;
  A gain control unit that controls the gain of the amplifier based on a signal output from the amplifier and adjusts the amplitude of the signal output from the amplification within a predetermined range;
  In a magnetic recording data reproducing apparatus comprising: a demodulating circuit that demodulates data recorded on the medium based on a period change of a signal output from the amplifier;
  The gain controller is
  A first comparator for comparing a first threshold value set within an allowable amplitude range of an input signal with which the demodulation circuit can normally demodulate magnetic recording data and a signal output from the amplifier;
  A second comparator that compares a signal that is output from the amplifier with a second threshold value that is greater than the first threshold value within the allowable amplitude range;
  Based on the timing at which the outputs of the first comparator and the second comparator change,The ratio of the time when the signal output from the amplifier exceeds the first threshold value to the time when the signal exceeds the second threshold value is expressed as the ratioCorresponding to the amplitude of the signal output from the amplifierDetect as amplitude correspondence valueAn amplitude corresponding value detection means;
  Control means for controlling the gain of the amplifier so that the amplitude corresponding value detected by the amplitude corresponding value detecting means approaches a reference value set in advance.
  A magnetic recording data reproducing apparatus according to claim 5 of the present invention is the magnetic recording data reproducing apparatus according to claim 1 or 4,
  The control means includes
  A storage table for storing in advance the relationship between the amplitude corresponding value output by the amplitude corresponding value detection means and the gain variable coefficient of the amplifier necessary for matching the amplitude corresponding value to the reference value;
  It is determined whether or not the amplitude corresponding value output by the amplitude corresponding value detecting means is within a preset allowable range, and when it is within the allowable range, the gain of the amplifier is maintained as it is and is not within the allowable range. Sometimes, the amplitude corresponding value detecting means outputs a variable gain coefficient corresponding to the amplitude corresponding value from the storage table, and setting a new gain obtained by multiplying the gain variable coefficient by the current gain in the amplifier. The amplitude corresponding value is controlled so as to coincide with the reference value.
[0012]
  Further, the claims of the present invention6An apparatus for reproducing magnetic recording data of claim 1 is provided.To any of ~ 5In the magnetic recording data reproducing apparatus described above,
  An encryption means for encrypting the data demodulated by the demodulation circuit;
  The amplifier, demodulation circuit, gain control means and encryption means are accommodated in the case of the magnetic head,Blocking extraction of data before encryption, magnetic head and amplifier output signal by resin filled in the gap in the case,The data encrypted by the encryption means is output to the outside of the case.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the configuration of a magnetic recording data reproducing apparatus 20 according to an embodiment of the present invention.
[0014]
The reproducing apparatus 20 relatively moves the magnetic head 21 in contact with the magnetic recording surface 1a of the magnetic recording medium 1 such as a magnetic card, and the amplitude corresponds to the change in the magnetic strength of the magnetic recording surface 1a. A signal that changes is output.
[0015]
When the magnetic recording medium 1 is a magnetic card, the magnetic recording medium 1 is moved with respect to the magnetic head 21 by a transport device (not shown) or is slid by manual operation along a guide groove or the like.
[0016]
The signal output from the magnetic head 21 is input to the gain controllable amplifier 22 to be amplified, and input to the demodulation circuit 23 and the gain control unit 24. The amplifier 22 includes a voltage control amplifier (VCA) whose gain is determined by an analog control voltage or a programmable amplifier whose gain is determined by a digital control value.
[0017]
The demodulation circuit 23 demodulates data from the output signal of the amplifier 22. This demodulation is performed based on the period of the output signal of the amplifier 2.
[0018]
That is, when a data string as shown in FIG. 2A, for example, is recorded on the magnetic recording medium 1 such as a magnetic card, the inversion period of the magnetization direction becomes data “1” as shown in FIG. On the other hand, T and data “0” are written by a signal that changes at 2T. This writing method is generally called an MFM method or 1F2F method.
[0019]
With respect to the data written in this way, the frequency from the magnetic head 21 is 1 / T in the section of data “1” and 1 / T in the section of data “0” as shown in FIG. A sinusoidal signal of 2T is output.
[0020]
With respect to this output signal, the demodulation circuit 23 obtains positive and negative peak timings as shown in FIG. 2D, and if there are two peaks in the predetermined period Ts, the data in that period is determined as “1”. If there is only one peak in the predetermined period Ts, the data for that period is determined as “0”, and the determination result is output as demodulated data.
[0021]
As described above, when the magnetic recording medium 1 is transported and read by the transport device, the moving speed of the magnetic recording medium 1 with respect to the magnetic head 21 is always constant, and the determination period Ts is known. When 1 is manually slid and read, the moving speed varies, so the determination period Ts is varied according to the moving speed. In this case, the relative movement speed of the magnetic recording medium 1 with respect to the magnetic head 21 is obtained from the time between the peaks of the initial read signal (for example, the read signal for the dummy data) to determine the determination period Ts.
[0022]
However, in the following description, the relative movement speed of the magnetic recording medium 1 with respect to the magnetic head 21 is assumed to be substantially constant.
[0023]
On the other hand, the gain control unit 24 controls the gain of the amplifier 22 so that the amplitude of the signal output from the amplifier 22 is within the allowable amplitude range of the input signal that allows the demodulation circuit 23 to correctly demodulate data.
[0024]
The gain control unit 24 includes a first comparator 25, a second comparator 26, an amplitude corresponding value detection means 27, and a control means 28.
[0025]
The first comparator 25 generates a first threshold value V1 set at, for example, the center of an allowable amplitude range of an input signal in which the demodulation circuit 23 can normally demodulate magnetic recording data, and a signal output from the amplifier 22. A signal of a level representing the magnitude relationship between the two is output. For example, when the signal output from the amplifier 22 is equal to or higher than the first threshold value V1, a high level signal is output, and when the signal is lower than the first threshold value V1, a low level signal is output.
[0026]
The second comparator 26 compares the second threshold value V2 that is larger than the first threshold value V1 in the allowable amplitude range and the signal output from the amplifier 22, and has a level that indicates the magnitude relationship between the two. Output a signal. For example, when the signal output from the amplifier 22 is equal to or higher than the second threshold value V2, a high level signal is output, and when the signal is lower than the second threshold value V2, a low level signal is output.
[0027]
Outputs of the first comparator 25 and the second comparator 26 are input to the amplitude corresponding value detection means 27.
[0028]
The amplitude corresponding value detection means 27 detects the amplitude corresponding value P corresponding to the amplitude of the signal output from the amplifier 22 based on the timing when the output states of the first comparator 25 and the second comparator 27 change. To do.
[0029]
The amplitude corresponding value P is monotonously changed with respect to the change in the amplitude Va of the signal E output from the amplifier 22 and is based on the timing at which the output states of the first comparator 25 and the second comparator 27 change. Any value that can be detected.
[0030]
For example, as shown in FIG. 3, a time ΔT from when the signal E output from the amplifier 22 exceeds the first threshold value V1 until it exceeds the second threshold value V2 is output from the amplifier 22. Since the signal Va has a shorter amplitude Va, the time ΔT may be detected as the amplitude corresponding value P.
[0031]
In this case, for example, the time from when the output of the first comparator 25 changes from the low level to the high level until the output of the second comparator 25 changes from the low level to the high level is measured. The measurement result is used as the amplitude correspondence value.
[0032]
As shown in FIG. 4, the ratio T2 / of the time T1 when the signal E output from the amplifier 22 exceeds the first threshold value V1 and the time T2 when it exceeds the second threshold value V2 Since T1 increases as the amplitude Va of the signal E output from the amplifier 22 increases, the ratio T2 / T1 may be detected as the amplitude corresponding value P.
[0033]
In this case, for example, the time from when the output of the first comparator 25 changes from low level to high level until it returns to low level, and the output of the second comparator 25 changes from low level to high level. Then, the time until returning to the low level is measured, and the ratio of the measurement results is set as the amplitude corresponding value.
[0034]
The amplitude correspondence value P detected by the amplitude correspondence value detection means 27 is input to the control means 28.
[0035]
The control unit 28 controls the gain of the amplifier 22 so that the amplitude corresponding value P detected by the amplitude corresponding value detecting unit 27 falls within a preset allowable range Pr ± β with respect to the predetermined reference value Pr.
[0036]
The reference value Rr is output from the amplitude corresponding value detection means 27 when the amplitude Va of the signal E output from the amplifier 22 is the optimum value Vr within the amplitude range and larger than the second threshold value V2. Is set to be equal to the corresponding amplitude value. The allowable deviation β is set corresponding to the deviation in recording intensity of a series of data magnetically recorded on the magnetic recording medium 1.
[0037]
The control means 28 stores the relationship between the amplitude correspondence value P output from the amplitude correspondence value detection means 27 and the gain variable coefficient α of the amplifier 22 necessary to make the amplitude correspondence value P coincide with the reference value Pr. When the amplitude corresponding value P is detected by the amplitude corresponding value detecting means 27, it is determined whether or not the amplitude corresponding value P is within the allowable range Pr ± β. In this case, the gain variable coefficient α corresponding to the amplitude corresponding value P is read from the storage table 28 a, and a new gain obtained by multiplying the current gain G by the gain coefficient α is set in the amplifier 22 and output from the amplifier 22. The amplitude Va of the signal E to be applied is made substantially equal to the optimum value Vr.
[0038]
For example, as shown in FIG. 3, the time ΔT from when the signal E output in a sine wave form from the amplifier 22 exceeds the first threshold value V1 until it exceeds the second threshold value V2 is represented by the amplitude corresponding value P As shown in FIG. 5, the relationship between the amplitude corresponding value P and the gain variable coefficient α of the amplifier 22 necessary for making the amplitude corresponding value P coincide with the reference value Pr is as shown in FIG. When the value P (= ΔT) is the reference value Pr, the gain variable coefficient α is 1, and as the amplitude corresponding value P (= ΔT) increases (that is, the amplitude of the output signal of the amplifier 22 decreases), the gain variable coefficient α Becomes a monotonically increasing characteristic F1.
[0039]
Therefore, for example, as shown in FIG. 5, when the amplitude corresponding value P1 smaller than the lower limit value Pr-β of the allowable range is detected by the amplitude corresponding value detecting means 27, it is smaller than 1 corresponding to the amplitude corresponding value P1. A lower gain obtained by multiplying the current gain G by the gain variable coefficient α1 is set in the amplifier 22, and the amplitude Va of the signal E output from the amplifier 22 is lowered to the optimum value Vr.
[0040]
Further, as shown in FIG. 4, the ratio T2 / T1 between the time T1 when the signal E output from the amplifier 22 exceeds the first threshold value V1 and the time T2 when it exceeds the second threshold value V2. Is detected as the amplitude corresponding value P, the relationship between the amplitude corresponding value P and the gain variable coefficient α of the amplifier 22 required to make the amplitude corresponding value P coincide with the reference value Pr is shown in FIG. Thus, when the amplitude corresponding value P (= T2 / T1) is the reference value Pr, the gain variable coefficient α is 1, and the amplitude corresponding value P (= T2 / T1) becomes larger (that is, the output signal of the amplifier 22). A characteristic F2 in which the gain variable coefficient α monotonously decreases as the amplitude increases.
[0041]
Therefore, for example, when the amplitude corresponding value P2 larger than the upper limit value Pr + β of the allowable range is detected by the amplitude corresponding value detecting means 27, the current gain G is multiplied by a gain variable coefficient α2 smaller than 1 corresponding to the amplitude corresponding value P2. The lower gain obtained in this way is set in the amplifier 22, and the amplitude Va of the signal E output from the amplifier 22 is lowered to the optimum value Vr.
[0042]
When the amplifier 22 is constituted by a voltage control amplifier (VCA), the control means 28 sets an analog control voltage signal corresponding to a necessary gain to the amplifier 22, and the amplifier 22 is configured by a programmable amplifier. If configured, the necessary gain is set as a digital value.
[0043]
FIG. 7 is a flowchart showing a processing procedure of the gain control unit 24 of the reproducing apparatus 20 when the amplitude corresponding value P is obtained by the time difference ΔT.
[0044]
Hereinafter, the operation of the reproducing apparatus 20 will be described based on this flowchart.
When reading on the magnetic recording medium 1 is started, the gain control unit 24 sets the gain G of the amplifier 22 to the maximum Gm (S1, S2).
[0045]
Here, a signal for data (for example, dummy data) recorded on the magnetic recording medium 1 is output from the magnetic head 21, and for example, a signal E shown in FIG. When the first threshold value V1 is exceeded at time t0, the output of the first comparator 25 changes from low level to high level as shown in FIG. 8B, and the time t0 is stored (S3). , S4).
[0046]
When the voltage of the signal E further rises and exceeds the second threshold value V1 at time t1, the output of the second comparator 26 changes from the low level to the high level as shown in FIG. 8C. The time t1 is stored (S5, S6).
[0047]
Here, the difference ΔT = t1−t0 between time t0 and time t1 is obtained as the amplitude corresponding value P1 (S7).
[0048]
Next, it is determined whether or not the detected amplitude corresponding value P1 is within the allowable range Pr ± β. If the detected amplitude corresponding value P1 is not within the allowable range, a gain variable coefficient α1 corresponding to the amplitude corresponding value P1 is obtained (S8, S9).
[0049]
Here, since the initial gain of the amplifier 22 is maximum, the amplitude of the signal E output from the amplifier 22 is very large, and the amplitude corresponding value P1 (= ΔT) is the upper limit value of the allowable range set with respect to the reference value Pr. It becomes larger than Pr + β, and the gain variable coefficient α1 becomes a value smaller than 1.
[0050]
At time t2, the gain of the amplifier 22 is changed to a lower gain obtained by multiplying the gain variable coefficient α1 by the current gain G (= Gm), and the amplitude of the output signal E of the amplifier 22 is reduced and optimal. It approaches the value Vr (S10).
[0051]
Similarly, the processing of S3 to S7 is repeated to detect the amplitude corresponding value P1, and if the amplitude corresponding value P1 is within the allowable range Pr ± β, the gain of the amplifier 22 is not changed and the processing returns to processing 3. When the detected amplitude corresponding value P1 is out of the allowable range Pr ± β, the gain variable coefficient α corresponding to the amplitude corresponding value P1 is obtained and the gain of the amplifier 22 is varied to return to the processing 3. This is performed until the reading of the magnetic recording data of the recording medium 1 is completed (S11).
[0052]
In this way, the amplifier 22 so that the amplitude corresponding value P detected based on the timing at which the output states of the first comparator 25 and the second comparator 26 receiving the output signal of the amplifier 22 change approaches the reference value Pr. Therefore, the amplitude of the output signal of the amplifier 22 can be quickly converged to an optimum value for the demodulation processing of the demodulation circuit 23.
[0053]
For this reason, even when the variation in the recording level of the data for each magnetic recording medium 1 is large or when the variation in the recording level of a series of data in one magnetic recording medium 1 is large, the data can be correctly demodulated.
[0054]
Further, it is not necessary to increase the dummy data inserted before the original data of the magnetic recording medium 1 such as a magnetic card, and it is not necessary to sacrifice the amount of data to be recorded.
[0055]
Further, in the flowchart shown in FIG. 7, the amplitude correspondence value P (= ΔT) is detected only by simple time measurement processing without using multiplication / division calculations, and thus all processing of the reproducing apparatus 20 is made into one chip. Even when executed by the microprocessor, the gain of the amplifier 22 can be controlled without greatly affecting other processes.
[0056]
Further, in this way, when the amplitude corresponding value P detected by the time difference ΔT is controlled so as to approach the reference value Pr, the relative moving speed of the magnetic recording medium 1 with respect to the magnetic head 21 may always be substantially constant. As described above, when the magnetic recording medium 1 such as a magnetic card is manually slid to reproduce the magnetic recording data, the frequency of the signal output from the amplifier 22 will vary if the speed of the sliding movement varies greatly for each magnetic recording medium. However, even if the magnetic recording medium 1 has the same recording level, the detected time difference ΔT changes greatly and the amplitude cannot be controlled correctly.
[0057]
In order to improve this point, two methods are conceivable.
In the first method, the amplitude correspondence value P (= ΔT) output from the amplitude correspondence value detection means 27 and the amplitude correspondence value P to the reference value Pr are stored in the storage table 28a of the control means 28 for each moving speed. The relationship with the gain variable coefficient α of the amplifier 22 necessary for matching is stored, and the magnetic recording medium 1 for the magnetic head 21 is determined from the time between the peaks of the initial read signal as described in the demodulating circuit 23. (When the demodulation circuit 23 has a speed detection function, this is also used), and a gain variable coefficient α corresponding to the time difference ΔT is obtained from the storage table 28a corresponding to this speed v. In the same manner as described above, the gain of the amplifier 22 is controlled.
[0058]
Since this first method only increases the selection process of the storage table 28a with respect to the above process, it is possible to cope with variations in the relative movement speed without substantially reducing the response speed.
[0059]
  In the second method, the amplitude correspondence value P (= ΔT) output by the amplitude correspondence value detection means 27 for the reference speed vr and the amplitude correspondence value P are matched with the reference value Pr in the storage table 28a of the control means 28. The relationship with the gain variable coefficient α of the amplifier 22 required for the recording is stored, and as described in the demodulating circuit 23, the time between the peaks of the initial read signal is determined from the time of the magnetic recording medium 1 with respect to the magnetic head 21. The relative moving speed v is obtained (when the demodulating circuit 23 has a speed detecting function, this is also used), and this speed v and the reference speed vrAnd the result obtained by multiplying the time difference ΔT by the ratio γ is used as the amplitude corresponding value P, and the gain variable coefficient α corresponding to the amplitude corresponding value P is determined from the storage table 28a. Similarly, it is a method of controlling the gain of the amplifier 22.
[0060]
In this method, data about the reference speed vr may be stored in the storage table 28a, so that it is possible to cope with variations in relative movement speed with a small memory capacity.
[0061]
In the flowchart of FIG. 7, the amplitude corresponding value P is detected by the time difference ΔT. However, as described above, the amplitude corresponding value P may be detected by the time ratio T2 / T1. In this case, the processes of S21 to S25 of FIG. 8 may be used instead of the process S7 of the flowchart of FIG.
[0062]
Here, since both the times T2 and T1 are values inversely proportional to the relative movement speed v, the ratio T2 / T1 between them does not depend on the relative movement speed v.
[0063]
Accordingly, when the amplitude corresponding value P is obtained by the time ratio T2 / T1, the variation in the relative movement speed of the magnetic recording medium 1 with respect to the magnetic head 21 as described above need not be considered.
[0064]
Note that, in the reproducing apparatus that reproduces data recorded on the magnetic recording medium 1 as described above, when it is necessary to prevent the reproduced data from being illegally extracted, for example, the reproducing apparatus 20 shown in FIG. ', An encryption unit 30 that encrypts and outputs the data demodulated by the demodulation circuit 23 is provided, and the amplifier 22, the demodulation circuit 23, the gain control unit 24, and the encryption unit 30 are provided in the case of the magnetic head 21. The data stored in 21a may be configured so that only the data encrypted by the encryption means 30 is output. In this case, the gap in the case 21a is filled with epoxy resin so that the data before encryption and the output signals of the magnetic head 21 and the amplifier 22 cannot be extracted from the outside of the case 21a.
[0065]
Further, if the circuit including the amplifier 22, demodulating circuit 23, gain control unit 24, and encryption means 30 is constituted by an integrated circuit formed on a single chip, it is accommodated in a case 21a having the same external dimensions as a conventional magnetic head. be able to.
[0066]
【The invention's effect】
  As described above, the reproducing apparatus for magnetic recording data according to claim 1 of the present invention provides:
  A magnetic head that moves relative to a magnetically recorded medium and outputs a signal corresponding to a change in magnetism of the magnetic recording surface of the medium;
  An amplifier capable of gain control for amplifying an output signal of the magnetic head;
  A gain control unit that controls the gain of the amplifier based on a signal output from the amplifier and adjusts the amplitude of the signal output from the amplification within a predetermined range;
  In a magnetic recording data reproducing apparatus comprising: a demodulating circuit that demodulates data recorded on the medium based on a period change of a signal output from the amplifier;
  The gain controller is
  A first comparator for comparing a first threshold value set within an allowable amplitude range of an input signal with which the demodulation circuit can normally demodulate magnetic recording data and a signal output from the amplifier;
  A second comparator that compares a signal that is output from the amplifier with a second threshold value that is greater than the first threshold value within the allowable amplitude range;
  Based on the timing at which the outputs of the first comparator and the second comparator change,A time difference from when the signal output from the amplifier exceeds the first threshold value until it exceeds the second threshold value is determined, and the time difference is calculated.Amplitude correspondence value corresponding to the amplitude of the signal output from the amplifierAsAn amplitude corresponding value detecting means for detecting;
  Control means for controlling the gain of the amplifier so that the amplitude corresponding value detected by the amplitude corresponding value detecting means approaches a reference value set in advance.
[0067]
  thisAs described above, the time difference from the time when the signal output from the amplifier exceeds the first threshold to the time when the signal exceeds the second threshold is detected as an amplitude corresponding value, and the amplifier Control gainTherefore, the amplitude of the output signal of the amplifier can be quickly converged to the optimum value for the demodulation process of the demodulation circuit, and the data recorded on the magnetic recording medium can be accurately demodulated.
  Also, it is not necessary to increase the dummy data inserted before the original data of the magnetic recording medium such as a magnetic card more than necessary, and it is not necessary to sacrifice the original data amount.
[0068]
  A magnetic recording data reproducing apparatus according to claim 2 of the present invention is the magnetic recording data reproducing apparatus according to claim 1,
  The control means includes
  The relationship between the amplitude corresponding value output by the amplitude corresponding value detecting means for each moving speed of the medium with respect to the magnetic head, and the gain variable coefficient of the amplifier necessary for matching the amplitude corresponding value to the reference value A storage table for storing in advance,
  Means for determining a relative moving speed of the medium with respect to the magnetic head from a time between peaks of an initial read signal of the magnetic head with respect to the medium;
  By determining a gain variable coefficient corresponding to the amplitude corresponding value from the storage table corresponding to the determined relative movement speed, and setting a new gain obtained by multiplying the current variable by the gain variable coefficient in the amplifier. , And control so that the amplitude corresponding value matches the reference value.
  For this reason, it is possible to cope with variations in the relative movement speed of the medium with respect to the magnetic head without substantially reducing the response speed.
[0069]
  A magnetic recording data reproducing apparatus according to claim 3 of the present invention is the magnetic recording data reproducing apparatus according to claim 1,
  The control means includes
  When the moving speed of the medium with respect to the magnetic head is a reference speed, the amplitude corresponding value output by the amplitude corresponding value detecting means and the gain variable of the amplifier necessary for matching the amplitude corresponding value with the reference value A storage table for storing the relationship with the coefficients in advance;
  Means for determining a relative moving speed of the medium with respect to the magnetic head from a time between peaks of an initial read signal of the magnetic head with respect to the medium;
  Means for obtaining a ratio between the obtained relative movement speed and the reference speed, and further multiplying the amplitude correspondence value by this ratio to obtain a new amplitude correspondence value;
  By detecting a gain variable coefficient corresponding to the newly obtained amplitude corresponding value from the storage table and setting a new gain obtained by multiplying the current variable by the gain variable coefficient, the amplitude corresponding value detection The amplitude corresponding value output by the means is controlled so as to coincide with the reference value.
  Therefore, it is possible to cope with variations in the relative moving speed of the medium with respect to the magnetic head with a small memory capacity.
[0070]
  According to a fourth aspect of the present invention, there is provided a magnetic recording data reproducing apparatus according to the present invention.
  A magnetic head that moves relative to a magnetically recorded medium and outputs a signal corresponding to a change in magnetism of the magnetic recording surface of the medium;
  An amplifier capable of gain control for amplifying an output signal of the magnetic head;
  A gain control unit that controls the gain of the amplifier based on a signal output from the amplifier and adjusts the amplitude of the signal output from the amplification within a predetermined range;
  In a magnetic recording data reproducing apparatus comprising: a demodulating circuit that demodulates data recorded on the medium based on a period change of a signal output from the amplifier;
  The gain controller is
  A first comparator for comparing a first threshold value set within an allowable amplitude range of an input signal with which the demodulation circuit can normally demodulate magnetic recording data and a signal output from the amplifier;
  A second comparator that compares a signal that is output from the amplifier with a second threshold value that is greater than the first threshold value within the allowable amplitude range;
  Based on the timing at which the outputs of the first comparator and the second comparator change, the time during which the signal output from the amplifier exceeds the first threshold and the second threshold Amplitude corresponding value detecting means for detecting a ratio with a time exceeding the amplitude corresponding value corresponding to the amplitude of the signal output from the amplifier,
  Control means for controlling the gain of the amplifier so that the amplitude corresponding value detected by the amplitude corresponding value detecting means approaches a reference value set in advance.
[0071]
  As described above, the ratio of the time when the signal output from the amplifier exceeds the first threshold value and the time when the signal exceeds the second threshold value is detected as the amplitude corresponding value, and the value is the reference value. The gain of the amplifier is controlled so that the amplitude of the output signal of the amplifier is not affected by variations in the relative moving speed of the medium with respect to the magnetic head. The data recorded on the magnetic recording medium can be accurately demodulated.
[0072]
  Further, the claims of the present invention6An apparatus for reproducing magnetic recording data of claim 1 is provided.To any of ~ 5In the magnetic recording data reproducing apparatus described above,
  An encryption means for encrypting the data demodulated by the demodulation circuit;
  The amplifier, demodulation circuit, gain control means and encryption means are accommodated in the case of the magnetic head,Blocking extraction of data before encryption, magnetic head and amplifier output signal by resin filled in the gap in the case,The data encrypted by the encryption means is output to the outside of the case.
[0073]
For this reason, there is no possibility that data recorded on the magnetic recording medium is illegally used.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.
FIG. 2 is a diagram for explaining the operation of the main part of the embodiment;
FIG. 3 is a diagram for explaining the operation of the main part of the embodiment;
FIG. 4 is a diagram for explaining the operation of the main part of the embodiment;
FIG. 5 is a diagram for explaining the operation of the main part of the embodiment;
FIG. 6 is a diagram for explaining the operation of the main part of the embodiment;
FIG. 7 is a flowchart illustrating a processing procedure of a main part of the embodiment.
FIG. 8 is a flowchart illustrating a processing procedure of a main part of the embodiment.
FIG. 9 is a diagram showing the configuration and the accommodation state of another embodiment.
FIG. 10 is a block diagram showing a configuration of a conventional apparatus.
[Explanation of symbols]
1 Magnetic recording media
20 Playback device
21 Magnetic head
21a case
22 Amplifier
23 Demodulator
24 Gain controller
25 First comparator
26 Second comparator
27 Amplitude corresponding value detection means
28 Control means
28a storage table
30 Encryption means

Claims (6)

A magnetic head that moves relative to a magnetically recorded medium and outputs a signal corresponding to a change in magnetism of the magnetic recording surface of the medium;
An amplifier capable of gain control for amplifying an output signal of the magnetic head;
A gain control unit that controls the gain of the amplifier based on a signal output from the amplifier and adjusts the amplitude of the signal output from the amplification within a predetermined range;
In a magnetic recording data reproducing apparatus comprising: a demodulating circuit that demodulates data recorded on the medium based on a period change of a signal output from the amplifier;
The gain controller is
A first comparator for comparing a first threshold value set within an allowable amplitude range of an input signal with which the demodulation circuit can normally demodulate magnetic recording data and a signal output from the amplifier;
A second comparator that compares a signal that is output from the amplifier with a second threshold value that is greater than the first threshold value within the allowable amplitude range;
Based on the timing when the outputs of the first comparator and the second comparator change, the signal output from the amplifier exceeds the first threshold and then exceeds the second threshold. obtains a time difference of up to an amplitude corresponding value detecting means for detecting the amplitude corresponding value corresponding to the amplitude of the signal output of the difference between said time from said amplifier,
An apparatus for reproducing magnetic recording data, comprising: control means for controlling the gain of the amplifier so that the amplitude correspondence value detected by the amplitude correspondence value detection means approaches a preset reference value. The control means includes
The relationship between the amplitude corresponding value output by the amplitude corresponding value detecting means for each moving speed of the medium with respect to the magnetic head, and the gain variable coefficient of the amplifier necessary for matching the amplitude corresponding value to the reference value A storage table for storing in advance,
Means for determining a relative moving speed of the medium with respect to the magnetic head from a time between peaks of an initial read signal of the magnetic head with respect to the medium;
By determining a gain variable coefficient corresponding to the amplitude corresponding value from the storage table corresponding to the determined relative movement speed, and setting a new gain obtained by multiplying the current variable by the gain variable coefficient in the amplifier. 2. The reproducing apparatus for magnetic recording data according to claim 1 , wherein the amplitude corresponding value is controlled to coincide with the reference value . The control means includes
When the moving speed of the medium with respect to the magnetic head is a reference speed, the amplitude corresponding value output by the amplitude corresponding value detecting means and the gain variable of the amplifier necessary for matching the amplitude corresponding value with the reference value A storage table for storing the relationship with the coefficients in advance;
Means for determining a relative moving speed of the medium with respect to the magnetic head from a time between peaks of an initial read signal of the magnetic head with respect to the medium;
Means for obtaining a ratio between the obtained relative movement speed and the reference speed, and further multiplying the amplitude correspondence value by this ratio to obtain a new amplitude correspondence value;
By detecting a gain variable coefficient corresponding to the newly obtained amplitude corresponding value from the storage table and setting a new gain obtained by multiplying the current variable by the gain variable coefficient, the amplitude corresponding value detection 2. A reproducing apparatus for magnetic recording data according to claim 1, wherein said amplitude corresponding value output by said means is controlled to coincide with said reference value . A magnetic head that moves relative to a magnetically recorded medium and outputs a signal corresponding to a change in magnetism of the magnetic recording surface of the medium;
An amplifier capable of gain control for amplifying an output signal of the magnetic head;
A gain control unit that controls the gain of the amplifier based on a signal output from the amplifier and adjusts the amplitude of the signal output from the amplification within a predetermined range;
In a magnetic recording data reproducing apparatus comprising: a demodulating circuit that demodulates data recorded on the medium based on a period change of a signal output from the amplifier;
The gain controller is
A first comparator for comparing a first threshold value set within an allowable amplitude range of an input signal with which the demodulation circuit can normally demodulate magnetic recording data and a signal output from the amplifier;
A second comparator that compares a signal that is output from the amplifier with a second threshold value that is greater than the first threshold value within the allowable amplitude range;
Based on the timing at which the outputs of the first comparator and the second comparator change, the time during which the signal output from the amplifier exceeds the first threshold and the second threshold Amplitude corresponding value detecting means for detecting a ratio with a time exceeding the amplitude corresponding value corresponding to the amplitude of the signal output from the amplifier,
An apparatus for reproducing magnetic recording data , comprising: control means for controlling the gain of the amplifier so that the amplitude correspondence value detected by the amplitude correspondence value detection means approaches a preset reference value . The control means includes
A storage table for storing in advance the relationship between the amplitude corresponding value output by the amplitude corresponding value detection means and the gain variable coefficient of the amplifier necessary for matching the amplitude corresponding value to the reference value;
It is determined whether or not the amplitude corresponding value output by the amplitude corresponding value detecting means is within a preset allowable range, and when it is within the allowable range, the gain of the amplifier is maintained as it is and is not within the allowable range. Sometimes, the amplitude corresponding value detecting means outputs a variable gain coefficient corresponding to the amplitude corresponding value from the storage table, and setting a new gain obtained by multiplying the gain variable coefficient by the current gain in the amplifier. 5. The reproducing apparatus for magnetic recording data according to claim 1, wherein the amplitude corresponding value is controlled so as to coincide with the reference value. An encryption means for encrypting the data demodulated by the demodulation circuit;
The amplifier, demodulation circuit, gain control means, and encryption means are accommodated in the case of the magnetic head, and the data before encryption, the output signal of the magnetic head and the amplifier are filled with resin filled in the gap in the case. The reproduction of magnetic recording data according to any one of claims 1 to 5, wherein extraction is prevented and data encrypted by the encryption means is output to the outside of the case. apparatus.

Images