JP3333364B2 - Readout of recorded information from security paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a security paper, such as securities, tickets, and prepaid cards, in which a security line in which specific information is recorded to prevent forgery and enhance security is recorded. The present invention relates to a reading device for reading information.

[0002]

2. Description of the Related Art It has been well known that a security line is inserted into a sheet to form a security protection sheet as a countermeasure for forgery of securities and tickets. In this case, it is possible to use a ferromagnetic foil of an amorphous alloy or the like for the safety filament and to use the magnetic properties of the material and the non-rewritable recording information to produce a highly safe security paper. [See Japanese Unexamined Patent Publication No. Hei 7-32778 "Safety protection paper and its authenticity judging device" and Japanese Unexamined Patent Publication No. Hei 6-286368 "Record carrier card and its authenticity judging device" proposed by some of the inventors of the present application]

FIG. 6 (a) is a schematic diagram showing an outline of a signal reading device according to a conventional system which was partially proposed by the present inventor. Here, 1 is a magnetic detector, 2 is an information recording medium serving as a security line, 3 is a substrate serving as a security paper, and 5 is an amplifier. In the prior art proposed by some of the inventors of the present invention, generally, a read signal from the information recording medium 2 is processed as a time-series signal as shown in FIG. That is, after the output of the magnetic detector 1 is amplified by the amplifier 5 and waveform-shaped, it is binarized at a constant voltage level and used as digital information. For this reason, if the read output often contains noise, the recorded information is given redundancy and a method of automatically correcting even if a part of the information is missing or changed, or reducing the amount of information per unit area. Some scratches have been taken in a negligible way.

[0004]

However, when the security paper is used frequently on a daily basis, it is necessary to fold the paper.
Loss of information or change in recording state (so-called noise) due to wrinkles or the like may occur, and the reliability of the read result of the written information may be reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for reading recorded information from a security paper, which enables accurate reading of information even when the information recording medium is worn due to bending, wrinkling, or the like. .

[0006]

In order to solve this object, a method of reading recorded information from a security paper according to the present invention uses a method in which information is recorded in a predetermined repetition pattern on a security line of a ferromagnetic material. The main components of the security paper are a magnetic detector that reads the change in magnetic flux density due to external excitation and a frequency analyzer that extracts the frequency component of the periodic signal read from the repetitive pattern. It is configured to detect that the distribution pattern of the frequency component obtained from the frequency analyzer matches a predetermined pattern and determine that the paper is genuine security protection paper.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be clarified,
To facilitate understanding of the present invention, first, the principle of the present invention will be described. The present invention is characterized in that, instead of the conventional time-series information, a method is employed in which the shape of the entire pattern is regarded as one piece of information and distinguished from the others. When information written at regular intervals is read, as shown in FIG. 1A, a spectrum Pa whose frequency component is a main component proportional to the period can be observed. As shown in FIG. 1 (b), in the case of two types of intervals, spectra Pb and Pc, which are two frequency components, can be observed. In a pattern of N kinds of intervals, N frequency components P
n can be observed. As shown in FIG. 1C, in the case where the read signal intensity and the period of each pattern are recorded so as to change, the variance value of the spectrum (the degree of spread of the foot)
Px is observed differently. Many types such as those having different pattern intervals and intensities can be created, and meaningful information may be assigned to each pattern.
In addition, by combining a plurality of methods in addition to these, a large amount of information can be recorded in a limited area.
Note that POW on the vertical axis indicates the intensity of the spectrum.

The reason why the embodiment in which the frequency pattern is read information is resistant to noise is as follows.
From the Fourier transform formula

(Equation 1) H (f): Fourier transform of function h (t) Since information obtained from a writing pattern is a frequency function

H (t) = Acos (2πf ₀ t) (2)

Assuming that the added noise is r (t), from equation (1)

(Equation 3) δ (f): delta function R (f) is a Fourier transform of noise function r (t),
Assuming white noise, the constant is k. Therefore, it can be proved that the separation of the periodic signal buried in the noise by the Fourier transform is easy. However, in reality, the signal is of finite length and the noise also includes periodic ones.
Although it cannot be completely separated, the S / N ratio can be improved.

[0010]

FIG. 2 shows an embodiment of the present invention. Reference numeral 1 denotes a magnetic detector, which converts a magnetic intensity or a magnetic flux density into a voltage using a magnetic head or a Hall element or an MR (magnetic resistance) element to which a magnetostatic bias is applied. Reference numeral 2 denotes an information recording medium serving as a safety line, which is formed by attaching a ferromagnetic material to an insulating material such as plastic by vapor deposition, coating, plating, or the like.
Information is written on the ferromagnetic film in a repetitive interval pattern, and the way of writing is to change magnetic properties such as magnetic permeability in a manner such as thermal, pressure, slit, and partial deletion. 3 is a substrate on which the information recording medium 2 is mounted,
It is made of non-insulating material such as paper and plastic, and can be used as safety protection paper for banknotes, stock certificates, cash vouchers, prepaid cards, cash cards and the like. Reference numeral 4 denotes a feeder which conveys the substrate 3 for reading from the information recording medium 2. Instead of moving the substrate 3, the magnetic detector 1 may be moved and read to perform the same operation. Reference numeral 5 denotes an amplifier for amplifying a signal from the magnetic detector 1. Reference numeral 6 denotes a frequency analyzer for examining the frequency components of the amplified detection signal S. The result of the analysis is sent to a main controller CS such as a microcomputer, where it is determined what repetition period information was written.

FIG. 3 is a diagram for explaining the operation of the embodiment of FIG.
(A) is a cross-sectional view of the information recording medium 2, wherein when a magnetic field parallel or perpendicular to the surface is applied from the outside, the difference between the magnetic permeability of the black line portion α and the magnetic permeability of the non-black line portion (white line portion) β. A change in magnetic flux density occurs at the interface. (B) is an example of the waveform of the detection signal S obtained by reading the change in the magnetic flux density by the magnetic detector 1. The pattern interval is L ₁ , L ₂ , L ₃ and the feed speed is Vm
/ S, the intervals of the detection signals are T ₁ = L ₁ / V, T ₂
= L ₂ / V, obtained in the T ₃ = L ₃ / V becomes time interval.
Since this signal is repeatedly generated, the detection spectrum becomes f ₁ = 1 / T ₁ , f ₂ = 1 / T ₂ , f ₃ = 1 / T ₃ . Assuming that the number of changes that each frequency can take is N ₁ , N ₂ , N ₃ , the number of combinations is N = N ₁ × N ₂ × N _3. For example, assume three types of N ₁ , N ₂ , N ₃ Then
There are 27 possible combinations, which correspond to an information volume of about 4.5 bits. In the pattern in which the interval is changed as shown in FIG. 1C, the effect is the same as that obtained by frequency modulation.
The detection spectrum is in a state where the base is widened, and the degree of the spread is proportional to the degree of change of the time interval, so that this can also be used as a combination of states.

FIG. 4 shows an embodiment of the frequency analyzer 6.
An aliasing filter 61 composed of a low-pass filter that cuts frequencies equal to or higher than the sampling frequency, an A / D converter 62 that converts an analog signal into a digital signal,
A memory 63 for storing the converted digital signal, and an FF for performing an FFT operation (fast Fourier transform) on the stored signal
It consists of a T calculator 64. As the FFT operation unit 64, a DSP (digital signal processor), a microcomputer, or the like can be used. The same can be done by using an autocorrelation function operation instead of the FFT operation, or by using an IIR type or FIR type digital filter operation. The calculation result is stored in the memory as each frequency component.
The main control unit CS such as a microcomputer compares this with a table corresponding to a combination of frequencies prepared in advance and recognizes the information in which a match is written. Also,
The purpose of the frequency analyzer 6 can be similarly achieved by having a band-pass analog filter of a frequency expected to be detected from its principle in parallel.

FIG. 5 shows an example of a detected spectrum of an actual example in which the FFT processing is performed. (A) is a waveform P ₁ and its spectrum of time series signal before the noise is added. This is a readout of a pattern in which two patterns are repeatedly recorded with different intervals, and the two main spectra S
P ₁ and SP ₂ are observed. (B) shows noise N in the waveform P ₁ of the time-series signal which is a read output from this medium.
Are mixed in, and it is difficult to distinguish them with a time-series signal. However, the two spectra SP ₁ and SP ₂ are correctly observed, which is sufficient for discrimination. That is,
Lack of stored information due to folding or wrinkling of safety protection paper,
Even when noise is generated in the read output due to a change in the storage state or the like, information is written at pattern intervals as in the present invention, and the read output is determined based on the frequency spectrum. It is possible to detect reading of recorded information.

[0014]

As described above in detail, according to the present invention, the present invention is applied to a safety protection paper in which a security line in which information is written at a predetermined repetition pattern interval is embedded on a ferromagnetic information recording medium. Analyzing the signal read by the magnetic detector with a frequency analyzer and comparing the frequency component pattern with a predetermined standard frequency component pattern to determine whether they match. Thus, accurate judgment information can be easily obtained by preventing the influence of noise which is easily mixed. Therefore, there is an effect that the recording medium of the security line embedded in the security paper can be read stably and reliably to give an accurate determination result even if the security paper has a practical use fatigue.

[Brief description of the drawings]

FIG. 1 is a diagram showing a pattern interval written on an information recording medium and a frequency spectrum of a read output thereof.

FIG. 2 is a schematic diagram showing one configuration example of a reading device of the present invention.

FIG. 3 is a waveform chart for explaining the operation of the embodiment of FIG. 2;

FIG. 4 is a block diagram showing a configuration example of a frequency analyzer used in the present invention.

FIG. 5 is a characteristic diagram illustrating an example of a detection spectrum according to the present invention when noise is not added (a) and when noise is added (b).

FIG. 6 is a schematic perspective view (a) showing a conventional reading apparatus and a time chart for explaining data recording and detection methods thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic detector 2 Information recording medium 3 Substrate 4 Feeder 5 Amplifier 6 Frequency analyzer 61 Aliasing filter 62 A / D converter 63 Memory 64 FFT calculator

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kohei Enomoto 1-41 Kugayama, Suginami-ku, Tokyo Iwasaki Communication Equipment Co., Ltd. Examiner Kenichi Kiyota (56) References JP-A-7-32778 (JP, A) Patent 3271865 (JP, B2) Table 10-509394 (JP, A) Table 9-506566 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G06K 17 / 00 G09F 3/00 G06K 19/00 G07D 7/00

Claims (2)

(57) [Claims] 1. A magnetic detector for reading information on a safety protection paper in which information is recorded in a predetermined repetition pattern on a safety filament made of a ferromagnetic material, wherein the information is read out by reading a change in magnetic flux density due to external excitation; The main component is a frequency analyzer that extracts the frequency component of a signal having periodicity read from, and detects that the distribution pattern of the frequency component obtained from the frequency analyzer matches a predetermined pattern. A method for reading recorded information from security paper configured to determine that the paper is genuine security paper. 2. The method according to claim 1, wherein the predetermined repetition pattern includes a plurality of types of patterns having different repetition periods.