JPS5966795A - Magnetic reading with semiconductor magnetic sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic information reading method using a semiconductor magnetic sensor.

Recently, a banknote identification device using an InSb magnetoresistive element as a magnetic sensor has been put into practical use and is likely to be widely used. The background to this is that the InSb magnetoresistive element has the advantages of good air gap characteristics, good S/N, and low speed dependence as a detection means that requires high reliability such as banknote detection. This is because the fact that there is no such thing fits very well.

Recently, various papers and new applications describing the air gap characteristics of this 1nsb magnetic sensor have been reported. However, this good void characteristic may be a drawback depending on the recognition method when the object to be detected is a banknote. In other words, in a detection device that mainly uses surface information, the magnetic sensor has good air-gap tactility, so it may read even the magnetic information configured on the back surface of the object to be detected, resulting in an erroneous signal. This is because that.

Conventionally, this type of identification device has frequently used an optical center or a magnetic head, so that only information on the front surface of the banknote could be recognized. With the recent development of copying technology and improved accuracy, it has become difficult to identify counterfeit bills made by copying in banknote identification devices using these paperbacks. For this reason, identification accuracy has been improved by combining an optical center and a magnetic head, but for example, by simply sprinkling iron powder on a counterfeit banknote, the accuracy is only so high that it becomes impossible to identify a counterfeit banknote. I can't.

The present invention has been made in view of the above points, and handles magnetic information configured on the front and back sides of a paper leaf-like medium as magnetic information of the same grade, and absorbs erroneous signals that occur due to printing misalignment of magnetic information on the front and back sides. The present invention also provides a method for reading magnetic information using a semiconductor magnetic sensor that greatly improves identification accuracy.

Hereinafter, please refer to the drawings for an embodiment of the present invention.

This will be explained in detail.

FIG. 1 is a cross-sectional view of a detected object in which magnetic information is configured on the front surface 1a and the back surface 1b of a sheet-like medium 1, and (A) of the same figure shows magnetic information A and B on the front surface 1a and magnetic information on the back surface 1b. The figure shows a detected object with a normal positional relationship between U and D with no printing misalignment, and (B) shows the back side magnetic information (2 and D slightly misaligned with respect to the front side magnetic information A and H). Indicates an object to be detected with printing misalignment.Therefore, the magnetic information is divided into different codes, Zunawachi A, B, C, D and A', B', C1, D.
Displayed in ゛City Arca, A and xSB and B', CtoC', D
and d are magnetic t'#J signals having the same size and shape. In the figure, reference numeral 2 denotes a semiconductor magnetic sensor, and this magnetic sensor 2 includes a pair of, for example, InSb magnetoresistive elements and 4, and a permanent magnet for magnetically biasing this element. That is, a change in the output voltage of the magnetic sensor 2 is obtained by influencing the magnetic flux density of the magnetic flux passing through the magnetoresistive element 4 by alternating FZ with magnetic information printed with magnetic ink or the like.

In such a configuration, when the sheet-shaped medium 1 is transported in the direction of the arrow, the magnetoresistive element filter and the magnetoresistive element filter 4 of the magnetic sensor 2
is subjected to alternating arsenic field changes due to the magnetic information A=D, A~ □■)' of the medium 1, and the magnetic sensor output end P5
From this, the output waveforms shown in FIGS. 2(A,) and (B) are obtained. Figure 2 (A,) is the same as Figure 1 (AJ magnetic information A-
Figure 2 (B) shows the waveform according to Figure 1 (■3
) shows waveforms based on magnetic information A-D.

In the case of magnetic information A to D shown in FIG. 1(A), the trailing edge of A and the leading edge of C and the trailing edge of B and the leading edge of D are 1" M
t U) tVn*f! v ”CB D, C(DT
ia'A"11°7.

It is considered to be equivalent to the magnetic information shown in , and is obtained. A pair of magnetoresistive elements 6 and 4 of the magnetic sensor 2 shown in FIG. 11 are connected in series, and terminals 6 and 7 at both ends thereof are connected to a power source 11 as shown in FIG. Therefore, the first
When the magnetic information shown in FIG. 6 is read by the magnetic sensor 2 having the configuration shown in the figure, the output voltage between the sensor output terminal 5 and the ground terminal 7 has a double-headed waveform as shown in FIG. 2(A). Note that E indicates the power supply voltage.

By the way, in a banknote recognition device, various types of recognition are performed by shaping the output waveform shown in FIG. 2. For example, if the waveform is shaped by the threshold voltage vth shown in FIG. Corresponding to (B), Fig. 4 (
The output waveforms shown in A) and (B) are obtained. In other words, the magnetic information C and D have almost the same shape with only a slight positional deviation BlC, D and A', B', d, ■)
The output signals obtained from ' are significantly different as shown in FIGS. 4A and 4B.

Therefore, in the above detection method, if there is a slight positional shift in the magnetic information provided on the front and back surfaces of the paper sheet medium 1, a large difference will occur in the number of detected pulses. The above-mentioned detection method should be adopted for this type of identification device as it will be identified as a counterfeit note.
I can't.

In view of this point, in the present invention, the output terminal -P5 of the magnetic sensor 2
The output waveform obtained from (Fig. 2) is differentiated, and Fig. 5 (A
) and (B) are obtained. In FIG. 5(A), the first positive peak P1 is the magnetic information A
The second positive peak P2 corresponds to the leading edge of
Corresponding to the leading edge of 1#C, the sixth positive beak P
3 corresponds to the trailing edge of the magnetic information A, and the fourth positive peak P
4 corresponds to the trailing edge of the magnetic signal C. Also, Figure 5 (B)
, the first positive beak P/ corresponds to the leading edge of the magnetic information A, the second positive beak 1'' corresponds to the trailing edge of the magnetic information A, and the sixth positive beak P/ .

corresponds to the leading edge of the magnetic information C, and the fourth positive peak 1''4 corresponds to the trailing edge of the magnetic information C. Next, the waveforms in FIGS. 5A and 5B are shaped at zero crossings to obtain pulse waveforms shown in FIGS. 6A and 6B.

FIG. 7 shows a waveform shaping circuit embodying an embodiment of the invention described above. Power source 11 is a magnetic sensor! 2 and an amplifier, in this example an operational amplifier, which is provided with the required power, and usually a value of about 5 to 24 V is determined to suit the characteristics of the sensor and the characteristics of the operational amplifier. Magnetic sensor 2
The output terminal 5 of is coupled to an intensifying dJ circuit 16 via a decoupling capacitor 14. For example, when the sheet-shaped medium 1 is a banknote, the output voltage obtained from the sensor 2 due to the alternating field change caused by the magnetic information applied to the front and back surfaces of the sheet passing through the sensor is 04 at the peak value. ~0.
Since the voltage is as low as 8rr+V, the amplifying circuit 16 increases the voltage by about 20 to 50 times to obtain the desired output level. This output voltage is differentiated by a differentiating circuit 15 to obtain the differential output shown in FIG. This differential output is amplified by an amplification circuit 16 and then supplied to a waveform shaping circuit 17 that generates a zero-crossing wave. In this circuit 17, the differential output is shaped to zero level by the capacitor C1 and the driver D. After that, the width increasing circuit 18
6 (A) and (B).
The output waveform shown in is taken out from the output terminal 19.

As described above, according to the present invention, even if there is a slight deviation in the magnetic information generated on the front and back surfaces of paper leaf-like media such as banknotes, it is possible to obtain an output signal with the same number of pulses.
It is possible to completely eliminate defects that would cause a genuine bill to be distinguished from a counterfeit one.

In addition, since the magnetic information on the front and back sides of the paper leaf-like medium can be detected from one direction, the operation is easy. Furthermore, since the output signal from the magnetic sensor is differentiated, the differentiated signal is taken out as a zero-crossing wave, and the pulse is shaped. be.

-1- Recording+a In the example, the case where magnetic information ((information) is detected is explained. When overprinted on the same leaf-like medium (non-magnetic material) 1,
Alternatively, as shown in Figure 4, the present invention can be applied to the case where the sheet-like medium 1 is on the same plane as the sensor surface and is shifted in the width direction, and the desired effect can be achieved. What you can get is not even soil.

Further, although an In5b magnetoresistive element was used as the semiconductor magnetic sensor, other magnetoresistive elements with good air gap characteristics may be used. Of course, various other modifications and changes can be made as necessary.

[Brief explanation of drawings]

Figures 1 (A) and (B) are schematic configuration diagrams for explaining the method of the present invention, and Figures 2 (A) and (B) are Figure 1 (A).
) and (B), FIG. 6 is an explanatory diagram equivalently showing the magnetic information of FIG. 1 (A), and FIG. Figures 5 and 6 are output pulse waveform diagrams obtained by shaping the waveforms of Figures (A) and (B) by a conventional method, and are for explaining the method of the present invention. A) and (B)
are the differential waveform diagrams of Figures 2 (A, ) and (B), and Figure 6 (
A) and (B) are output pulse waveform diagrams obtained by shaping the differential waveform, FIG. 7 is a circuit diagram showing an example of a magnetic reading device implementing the method of the present invention, and FIGS. 8 and 9 are diagrams of the present invention. FIG. 7 is a schematic side view and a top view, respectively, showing other configurations of magnetic information on a sheet-like medium to which the invention method can be applied. 1 in the figure is a paper leaf-like medium, 2 is a semiconductor magnetic sensor, 6.4
is a 1nsb magnetic resistance element, and A to D, A' to 1 are magnetic information. Patent applicant Denki Onchi Co., Ltd. No. (A) No. (A)

Claims (1)

[Claims] A step of reading magnetic information configured on at least one side of a sheet-shaped medium with a semiconductor magnetic sensor, a step of differentiating an output signal from the semiconductor magnetic sensor, and a step of extracting the differential signal as a zero-crossing wave and pulse-shaping it. and the shaped pulse signal,? - A magnetic reading method using a semiconductor magnetic sensor, characterized in that magnetic information of the sheet-like medium is determined by: