JPS5951031B2 - Signal ternary method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for reading patterns on sheet-like printed matter such as banknotes and certificates.

Conventionally, when detecting patterns on banknotes, the signal level changes depending on whether the banknote is old or new or dirty, which has an adverse effect on denomination discrimination and authenticity discrimination. Particularly when using optical detection means, it has been a big problem to obtain a stable signal against such level changes. An object of the present invention is to provide a device that obtains a stable signal even with such level changes.

According to the present invention, the effect is particularly remarkable when a transmitted light sensor is used as the sensor, and it is also very effective when used as a reflected light sensor.

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 is a diagram showing the arrangement of sensors of the present invention. Banknote 1
will be explained assuming that it is conveyed at high speed in its lateral direction, that is, in the direction of arrow 2. P,,P,...,Pn
-, , Pn is a pattern sensor that detects patterns by transmitted light or reflected light by wavy arrows 3-1, 3-2, . . . in the figure.
...3-n-1, arranged along 3-n. From a practical point of view, the number n of sensors is n=2
~4 is appropriate. As mentioned above, the signals from sensors P1, P2, ..., Pn change depending on whether the banknote is old or new or dirty, but the signal from each sensor is uniformly high level for the difference between old and new banknotes. In addition, if there is a large amount of dirt, the effect of that dirt will be felt on two or more sensors. Therefore, in order to reduce the influence of old and new sensors and such contamination, the present invention calculates the difference in signals between adjacent sensors, differentiates the difference signal, and then calculates the difference between two appropriate thresholds. I converted it into a value.
In this way, by taking the difference between the signals from two sensors, uniform differences between the sensors can be canceled out, by differentiation, large contamination can be ignored, and by converting into three values, it is possible to eliminate obvious pattern changes. Only parts can be extracted. FIG. 2 shows one embodiment of the present invention, and FIG. 3 shows a second embodiment of the present invention.
It shows signal waveforms from each part in the figure.

In Figure 2, 10-1, 10-2, ......, 1
0-n is an amplifier circuit that can adjust the sensitivity variations of each sensor as necessary, and the sensor P
The analog output waveforms corresponding to Pl and Pl+1 are shown at 20-1 and 20-1+1 in FIG. 3a. As shown in Figure 3a, each waveform is 2''
-1,2 Changes like -1+1・. Therefore, as shown in Figure 2, 11-1,..., 11-n-1
Take the difference between the signals corresponding to adjacent sensors in the part,
Further, by taking the differential, 2]-1, 21 in Figure 3 b
A waveform like ``-1 is obtained.As can be seen from this waveform, there are some differences in the signal level depending on whether the banknote is new or old or dirty, but if we focus on the behavior of the polarity of the signal, the difference between the two waveforms is It can be seen that it is stable.Therefore, we set two thresholds with different signs, such as 24 and 25 in Figure 3b, and the differential signal of the difference becomes "1" when each threshold value is 24 or higher. Two binarized signals 26-1 and 27-1 are outputted so that the value becomes ゜゜1'' below the threshold value 25 (Fig. 3C, d).Such two binarized signals are This means that the original difference signal is ternarized, and each binary signal 26-1, 27-1 is the original signal 20-1, 20.
It becomes "1" only when there is a clear difference between -1+1.
12-1, 12-2,...12-n in Figure 2
-1 is the signal 21-1, 21-2,...21-n
Positive side of -1, 14-1, 142,..., 14
-n-1 is a circuit for performing binarization on the negative side, and performs binarization using 24 and 25 from 13 and 15 as thresholds, respectively. By performing the signal processing described above, it is possible to cancel out differences in signal levels due to differences between old and new banknotes, dirt, etc., and to obtain stable signals, which is effective, for example, in determining the denomination of banknotes and determining authenticity. signals.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the arrangement of the sensor of the present invention, FIG. 2 is a diagram showing an embodiment of the present invention, and FIG. 3 is a diagram of signal waveforms from each part of FIG. 2.

Claims (1)

[Claims] 1. A first step of converting patterns at a plurality of locations on a paper sheet into electrical signals, and a second step of outputting a signal corresponding to the difference between the electrical signals at designated locations; and a third step of converting the signal output in the second step into a ternary signal.
Value method. 2. The signal ternarization method according to item 1, wherein the specified locations are two locations adjacent to each other. 3. The signal corresponding to the difference is a signal obtained by spatially differentiating the difference between the electric signals.
Value method.