JPS5850391B2 - Authenticity determination method for printed matter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a printed matter, particularly a printed matter having a color pattern,
For example, it relates to a method for determining the authenticity of banknotes.

For example, as a method to determine the authenticity of banknotes, a light beam is scanned across the banknote, and the short wavelength light (5500 angstroms) and the long wavelength light (9500 angstroms) of the light transmitted through the banknote or the light reflected from the banknote.
000 angstroms), but the ratio of the amount of transmitted light or reflected light between short wavelength green light and long wavelength infrared light is the following value in the case of banknotes. .

Here, G is the amount of transmitted light (or reflected light) of 5500 angstroms, and R is the amount of transmitted light (or reflected light) of 9000 angstroms.

In such cases where the colors are not uniform, the change in the ratio of G and R due to the color pattern is small, so a highly accurate divider is required to determine the change in the ratio, that is, the color pattern. There were drawbacks.

An object of the present invention is to provide a method that can accurately determine the color pattern of printed matter and determine its authenticity even for items such as banknotes, which are not brightly colored, without using a highly accurate divider.

In order to achieve the above object, the present invention scans the pattern of a printed matter in a fixed direction with light beams of two different wavelengths (for example, 5500 angstroms and 9000 angstroms) that are lit alternately, and the reflected light or transmitted light of this light beam is Light is received by a photoelectric element, the ripple component of the output signal of this photoelectric element is extracted by a bandpass filter, and detected by a detector, and the output signal from which the ripple component of the photoelectric element has been removed is extracted by a low-pass filter, and the output signal is detected by a low-pass filter. The ratio between the output of the filter and the output of the low-pass filter is determined and compared with a predetermined pattern.

First, the principle of this method will be explained with reference to FIG.

The horizontal axis in FIG. 1 indicates time.

42 holes of 5500 angstroms and 9000 angstroms respectively
The projection light is projected alternately from a light source with angstroms, and when a banknote is scanned in a certain direction with these projection lights, and the light transmitted through the banknote is received by a photoelectric element, the photoelectric element outputs the waveform shown in C. It will be done.

Since banknotes generally have a slightly reddish tint, the amount of transmitted light R through the infrared light aperture is greater than the amount G of transmitted light through the green light aperture. Therefore, when the green light amount and the infrared light aperture are projected alternately, the photoelectric element The output will include ripple.

The area where the ripple is high is proportional to the amount of transmitted infrared light R,
The low value is proportional to the transmitted light amount G of the green light.

If the ripple component is removed from the waveform shown in C, it is shown in +
An R+G waveform is obtained, and the sharpness of each point of this waveform is proportional to □.

Next, by extracting only the ripple component from the waveform shown in C and appropriately amplifying it, the waveform shown in E is obtained, and when this waveform is detected, the waveform shown in E is obtained.

Since the waveform is detected by amplifying the ripple portion of waveform C, that is, RG, this is proportional to RG.

By the way, if you divide the waveform by the waveform 2, However, A is a constant of proportionality becomes.

As can be seen from the right side, this value is a function of G/R.

By setting a pattern of 1 and comparing it with the pattern obtained by dividing the output waveform of 2 by the output waveform of 2, it is possible to determine the authenticity of a banknote or the like.

In this case, A(RG) is used as the dividend,
By choosing the constant A appropriately, even if the value of RG is small, A(R
If the value of -G) is set to the same level as the value of R+G, the value of the color pattern of the banknote will change considerably, so the divider used to perform the division in equation (1) must be of high precision. Errors caused by the divider can be reduced.

An embodiment illustrating the present invention will be described in detail below.

FIG. 2 is a block diagram showing the configuration of an example of an apparatus for implementing the present invention, in which 1 is a 9000 angstrom infrared light source, 2 is a 5500 angstrom green light source, and 3 is a light source 1. .2 is a photoelectric element from which light is projected; 4 is an amplifier to which the output of the photoelectric element 3 is input; 5;
is a bandpass filter to which the output of the amplifier 4 is input; 6 is an amplifier to which the output of the filter 5 is input; 7 is a detector to which the output of the amplifier 6 is input; 8 is a low-pass filter to which the output of the amplifier 4 is input; Reference numeral 9 denotes a divider to which the output of the wave detector 7 is inputted as a dividend, and the output of the low-pass filter 8 is inputted as a divisor.

10 is a printed matter, which will hereinafter be referred to as a banknote.

It is assumed that the banknote 10 is transferred between the light sources 1 and 2 and the photoelectric element 3 in the direction of the arrow 11.

Next, the operation will be explained.

The light sources 1 and 2 emit light alternately as shown in Figure 1, A2, and their light amounts are made equal.

The lights from light sources 1 and 2 are projected onto substantially the same point on banknote 10.

In the part marked ■ in FIG. 1, the bill 10 is connected to the light sources 1 and 2 and the photoelectric element 3
, ■ indicates a period in which the white edge of the banknote 10 passes, ■ indicates a period in which the reddish pattern part of the banknote 10 passes, and ■ indicates a period in which the bluish pattern of the banknote 10 passes. It shows the waveforms of each section as they pass through.

When the bill 10 is transferred to the position of the light sources 1 and 2, the light source 1
, 2 passes through the bill 10 and is received by the photoelectric element 3, and the photoelectric element 3 generates an electrical output proportional to the amount of projected light.

Generally, the paper for banknotes has a reddish tint, and the amount of light that passes through the banknote 10 when the light source 1 is turned on is slightly smaller than the amount of light that passes through the banknote 10 when the light source 2 is turned on, and therefore the output of the photoelectric element 3 Waveform C includes ripples.

The frequency of this ripple is determined by the period at which the light sources 1.2 are alternately switched.

The output of the photoelectric element 3 is suitably amplified by an amplifier 4 and then input to a bandpass filter 5 and a low-pass filter 8.

A low pass filter 8 removes ripple from the output of the photoelectric element 3.

Therefore, only the ripple portion of the output of the output element 3 of the low-pass filter 5 is passed.

Therefore, the output of the bandpass filter 5 becomes the ripple portion of the waveform C.

This output is amplified to an appropriate level by amplifier 6.

Waveform E shows the output of the bandpass filter 5 amplified by the amplifier 6.

The output of the amplifier 6 is detected by a detector 7, and the detector 7 provides an output with a waveform shown in FIG.

This output is A'(RG).

However, A' is a constant determined by the amplification degree of the amplifier 6, etc.

The output of the detector 7 and the output of the low-pass filter 8 are input to a divider 9, and the output of the detector 7 is divided by the output of the low-pass filter 8.

This output changes over time as the banknote 10 is transferred in the direction of the arrow 11, and the output pattern is set in advance in a pattern setting device (not shown) based on the color pattern of the banknote. Then, in synchronization with the transfer of the banknotes 10, a comparison circuit (not shown) compares this set pattern with the output of the divider 9.

), the authenticity of the banknote 10 can be determined by comparing the output of the divider 9 with a set pattern using a comparison circuit.

As explained above, in general, for banknotes, etc., the change in the ratio of the amount of transmitted light between green light and infrared light due to the pattern is small, so it is difficult to accurately determine the pattern of the ratio. Since the value of this ratio changes considerably in response to a slight change in the value of G/R, it is possible to accurately and easily obtain the pattern of the above ratio without increasing the precision of the divider. It is possible to accurately determine the authenticity of banknotes, etc.

In the above embodiment, the transmitted light from the light sources 1 and 2 that has passed through the printed material is made to enter the photoelectric element 3.
The reflected light from the printed matter may be incident on the photoelectric element 3.

[Brief explanation of drawings]

FIG. 1 is an output waveform diagram of a main part of the device shown in FIG. 2, and FIG. 2 is a block diagram showing an example of the configuration of the device for carrying out the present invention. DESCRIPTION OF SYMBOLS 1...Short wavelength light source, 2...Long wavelength light source, 3...Photoelectric element, 5...Band filter, 7...・Detector, 8...Low pass filter, 9...Divider.

Claims (1)

[Claims] 1 A pattern on a printed matter is scanned in a fixed direction by two light beams of different wavelengths that are lit alternately, the reflected light or transmitted light of the light beam is received by a photoelectric element, and the ripple portion of the output signal of the photoelectric element is detected. The output signal is extracted by a bandpass filter and detected by a detector, and the ripple component of the photoelectric element is removed by a low-pass filter, and the ratio of the output of the detector and the output of the low-pass filter is determined. A method for determining the authenticity of printed matter, which is characterized by comparison with a predetermined pattern.