JPS5814705B2 - Print inspection equipment - Google Patents

Description

[Detailed Description of the Invention] The present invention irradiates printed matter with X-rays, detects fluorescent X-rays corresponding to specific contained elemental substances in the inspected printed matter, and detects characteristics such as the distribution pattern and concentration of contained elemental substances. detect,
The present invention relates to a printed matter inspection device that determines the correctness or type of printed matter.

Conventionally, the commonly used method of determining whether a printed matter is correct or incorrect is to irradiate light onto a predetermined location of the certified printed material and detect the proportion of reflected or transmitted light.

However, with the recent progress and widespread use of copying machines and the like, it is now relatively easy to make sophisticated copies of printed matter, and it is no longer always sufficient to use conventional optical means to determine whether a printed matter is correct or not.

Furthermore, as a means for detecting a specific element among the elemental substances contained in the certification printed material, there is an inspection apparatus using a fluorescent X-ray analyzer as shown in FIG. 1 as a conventional example.

This is a device for testing a quantized pattern obtained by binarizing a content distribution pattern of a specific contained element substance contained in a test paper using a certain threshold value to determine whether the test is correct or not.

In the figure, reference numeral 1 denotes an X-ray generator that irradiates a certain area C on a predetermined course of test paper A.

The test paper A is transported at a constant speed by an automatic transport device such as a transport belt B, and an X-ray detector 2 detects fluorescent X-rays generated when passing through the X-ray irradiation area C.

The pulse signal obtained from this X-ray detector 2 is transmitted to an amplifier 3.
The width will be increased to a certain level ■2.

The pulse signal ■2 obtained at this time is the predetermined area C of the test paper.
Since the pulse height corresponding to the various elemental substances contained in the substance and the number of pulses proportional to the content concentration are output, the discriminator 4 is used to detect the pulse with the wave height corresponding to the specific elemental substance to be detected. , 5.

Each discriminator 4, 5 detects only a pulse signal having a predetermined peak value, and outputs a pulse with the pulse height normalized.

Next, the pulse outputs Va, Vb obtained by the discriminators 4, 5 are led to rectifier circuits 6, 7, and converted into analog signals Va (t), Vb(t).

At this time, since the pulse input signals Va and Vb are pulse compression waves proportional to the concentration of each contained elemental substance, by optimally selecting the integration time constants of the rectifier circuits 6 and 7, the rectified outputs Va(t), Vb(t) is an analog voltage signal that substantially corresponds to the concentration distribution of the specific elements a and b.

In order to binarize this analog signal, the rectified output Va(t)
, Vb(t) are supplied to Schmitt circuits 8 and 9. Threshold value Sa set with Schmitt level setters 10 and 11,
A quantization pattern binarized with Sb is obtained.

Next, the outputs Wa and Wb of the Schmitt circuits 8 and 9 are supplied to an n-stage shift register 12.13, and are sent to the shift register 12.13 in the form of a quantized pattern according to the timing signal T1 supplied from the control pulse generation circuit 14. Stored.

At this time, timing T1 is the leading edge detection signal T of the test paper.

This occurs multiple times during the period in which the printed material passes through the X-ray irradiation area C.

The quantization patterns SRa and SRb stored in the soft registers 12 and 13 are compared with the quantization patterns of genuine printed matter stored in advance by the determination circuit 15, and a determination of authenticity is made based on whether the patterns match or do not match.

FIG. 2 is a waveform diagram of each part for explaining the above operation.

Figure a shows the detection area C, in which element a is uniformly contained and the printed pattern 1
Part 6 contains element b.

Although element C is contained in the frame 17, it is not detected in this example and is not detected.

At this time, the rectified output Va(
t), Vb(t) are shown in FIG. 2C and f.

Therefore, the quantization patterns Wa and Wb obtained from the Schmitt circuits 8 and 9 are shown by waveforms d and g.

These quantized patterns Wa, Wb are accommodated in the shift registers 12 and 13 by the timing signal T1 shown by waveform b.

The contents SRa and SRb are shown in Figure 2 e and h.

The authenticity or type of test paper A is determined using these quantization patterns SRa and SRb.

However, such discrimination methods cannot be used to precisely verify the fine features of the distribution pattern or the distribution concentration gradient of the contained elements, and are not sufficient in cases where the content concentration has decreased due to changes in the printed material over the years. Therefore, we could not expect sufficient adaptability and reliability of the device.

Therefore, as an even more reliable testing device, there is a need for an assay method that uses a more accurate distribution pattern based on a multilevel signal of the content distribution pattern, but it is difficult to obtain a highly accurate elemental distribution pattern. has a drawback that cannot be obtained by the method using the rectifier circuits 6 and 7 using integrators as described above.

The present invention has been developed in view of these demands, and it examines the characteristics of the content distribution pattern of specific elemental substances contained in the printed matter, printing ink, etc. by irradiating the printed matter to be inspected with X-rays.
An object of the present invention is to provide a printed matter inspection device that can highly reliably determine the authenticity or type of a certified printed matter by detecting the content concentration.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a schematic diagram of a printed matter inspection apparatus according to an embodiment of the present invention.

Reference numeral 19 is a detector for detecting fluorescent X-rays caused by X-rays irradiated onto the test paper from an X-ray generator (not shown), and includes, for example, a proportional counter, a scintillation counter, a semiconductor detector, etc.

The detector 19 converts the detected fluorescent X-rays into electrical pulse signals and supplies them to the amplifier 20.

The amplifier 20 converts this electrical pulse signal to the required voltage level.
The width is increased to 2 and supplied to the discriminators 21a to 21n, respectively.

Since the specific elemental substance contained in the test paper is obtained as an electrical pulse signal consisting of a specific peak value, as many discriminators as the number of elements required for determination are provided.

That is, the discriminators 21a to 21n pass only pulse signals having peak values corresponding to specific n types of elemental substances among the elements contained in the test paper.

For example, the discriminator 21a is composed of two comparators 211 and 212 and a logic circuit 213.

The comparator 211 sets the input pulse signal V2 to the upper limit threshold V
When compared with aH, the output VaH becomes logic "1" when V2>VaH.

In addition, the comparator 212 compares the input pulse signal ■2 with the lower limit threshold ■aL, and if ■2>VaI, the output V a
L becomes logic "1".

The logic circuit 213 consists of an AND circuit of VaH and (2)aL.

Therefore, the input pulse signal ■2 is V a L < V 2
Discriminator 2 only if < V a H
1a outputs a signal Va.

Therefore, by optimally setting the upper limit threshold and the lower limit threshold according to the peak value corresponding to the specific element a, the discriminator 21a generates the output signal Va every time the pulse signal 2 due to the element a is obtained.

The other discriminators 21b to 21n can be similarly configured, and the signal 2 is discriminated for each element by the discriminators 21a to 21n.

Outputs Va to Vn of the discriminators are supplied to data counters 22a to 22b, respectively, and are counted.

For example, the data counter 22a is connected to the control pulse generation circuit 2.
It is controlled by the counter clear pulse RS supplied from 6.

RS is output at every fixed sampling time Ts, and the count value by the output pulse Va of the disk limiter 22a is cleared at every fixed time Ts.

The count value in each sampling period is DATA0,
DATA1...DATAE, these count values are once sequentially written to each address of the data buffer memory 23a.

The address signals into which the count values are to be written are sequentially generated by the address counter 27.

In this way, the content distribution pattern of the specific element a in the test paper is obtained in the memory 23a.

Other data counters 22a to 22n also store count values obtained by counting pulse signals vb to Vn corresponding to specific elements at regular sampling time intervals Ts in data expansion memories 23b to 23n.

The content distribution patterns of various specific yc elements obtained in these memos 'J 2 3 a to 23 n are shown in the interface circuit 2.
4, the data is transferred to a determining unit 25, which is, for example, a microcomputer.

The determination unit 25 compares these content distribution patterns with a standard pattern that is a content distribution pattern of a specific element of an authentic test paper prepared in advance to determine the correctness or type of the test paper.

The above operation will be explained using the timing chart shown in FIG.

The passage signal TM is supplied to the pulse generation circuit 26 only during the period when the test paper A passes through the detection area of the X-ray detector 19.

The test paper A passes through the detection area at a constant speed by a transport mechanism (not shown), and a signal TM is generated by a photoelectric switch (not shown) or the like during this passing period.

Signal TM is shown in FIG. 4a.

The control pulse generation circuit 26 has this signal TM at logic “1”.
A signal RS is output at every fixed sampling time Ts.

Signal RS simultaneously clears data counters 22a-22n.

The sampling time Ts means the data reading resolution determined by the relationship with the transport speed Vm/s of the test paper A.

Therefore, at each sampling time Ts, the data counter 22
a to 22n count input pulses Va to Vn, respectively.

Changes in the contents of the data counter 22a (count 1 shift) are conceptually shown in FIG. 4e.

Although the contents of the other data counters 22b to 22n change differently, they operate at the same timing.

FIG. 4C shows a write enable signal W for writing the contents of data counters 222-22n to memories 23a-23n, which is generated by pulse generator 26 at the end of each sampling period.

Further, FIG. 4d shows a clock pulse CP which is output every N sampling times Ts before the signal W.

The signal CP is supplied to the address counter 27, as shown in FIG.
The address signal ADRS supplied to the memories 23a to 23H is sequentially updated as shown in FIG.

Therefore, the count values are sequentially stored in the memories 23a to 23n as shown in FIG. 4g.

Next, referring to FIG. 5, FIG. 5a shows the signal TM, and the time axis is larger than that in FIG. 4.

The period from when the test paper A passes until the next test paper B passes is allocated to transfer the element distribution patterns stored in the memories 23a to 23b to the determination section 25.

FIG. 5C shows write enable signals Ra to Rn generated from the pulse generator 26.

The memory 23a is controlled by the signals Ra, Rb,...,Rn.
, 23bt...23n are sequentially read out.

The data are then transferred sequentially as shown in FIG. 5b.

Referring to FIG. 6, the test paper A has a predetermined printed pattern (not shown) drawn on it.

The printing ink for printing the pattern contains various metal elements and the like.

When such test paper A is detected, for example, the memory 23
Data as shown by waveforms 28 and 29 are stored in a and 23b.

At this time, by setting the discriminators 21a and 21b to pass only the pulse signals 2 with peak values corresponding to elements a and b, respectively, the waveforms 28 and 29
represent the distribution patterns of elements a and b contained in test paper A, respectively.

As described above, according to the present invention, it is possible to obtain an element distribution pattern with extremely high accuracy, and it is possible to provide a highly reliable printed matter inspection equipment.

FIG. 7 is a diagram showing a modification of the signal processing section.

Two comparators 30 and 31 are used instead of the discriminator 21a and the data counter 22a shown in FIG.
, two counters 32 and 33, and a subtraction circuit 34 are provided.

The comparator 30 is the upper limit threshold V of the input pulse ■2.
Output pulse VaH is generated only when a pulse with a peak value exceeding aH is input.

This pulse V a H is counted by a counter 32 .

On the other hand, the comparator 31 generates the output pulse ■aL only when a pulse having a peak value exceeding the lower limit threshold value ■aL is inputted among the input pulses v2.

This pulse V a L is counted by a counter 33 .

Therefore, if the count value of the counter 32 is subtracted by the subtraction circuit 34 from the count value of the counter 33, the difference in the count value effectively becomes V a L < V 2 < V a H
This is the count value of input pulses with a peak value of .

The difference between these counts is written in the memo ') 2 3 a.

Note that the counters 32 and 33 operate at the time Ts according to the signal RS.
Cleared every time.

FIG. 8 shows a modification of the discriminator, and FIG. 9 is a timing chart thereof.

It has two comparators 211 and 212 having the same configuration as the discriminator shown in FIG. 3.

Now, as shown in FIG. 9A, when the input pulse 2 with VaL<V2<VaH is supplied, the output aL of the comparator 211 is logic TI O 11 (Figure 9A) The output VaI of the comparator 212 is logic +1 1 I+ (Figure 9 C).

The monostable FF 214 is triggered by the rise of VaL, and a pulse P1 having a constant width Td as shown in FIG. 9-2 is output.

This pulse P1 is used to monitor the output VaH of the comparator 211 during the pulse width period Td, and to prevent chattering of (2)aL.

Therefore, the output P1 of the FF 214 and the signal VaH obtained by the gate 215 are ANDed by the AND gate 216.

This gate 216 directly sets the FF 217 if there is even one output V a H of the comparator 211 during the period Td.

Now, when the input voltage 2 shown by the solid line in Figure 9A is applied, V a H remains "0" as shown by the solid line in the figure, so the output P of the FF 217 is the same. Figure 4
It remains "0" as shown by the solid line.

On the other hand, the FF 218 is directly set by the pulse P1 obtained from the terminal circuit of the FF 214.

Further, the pulse P1 obtained from the terminal Q of the FF 214 is passed through the delay circuit 219 to obtain the pulse P2 obtained by delaying the pulse P1 by a time Δt (FIG. 9(e)).

The pulse P2 is supplied to the FF 218 via the gate 220, and the FF 218 is reset at the falling edge of the pulse P2.

Therefore, the output pulse P3 of the FF 21B becomes as shown in FIG.

This pulse P3 is supplied to the clear terminal of FF217 and P
Clearing of FF217 is canceled only for the period of 3.

Further, the pulses P1, P2, and P3 are used to create a judgment pulse P4 with a constant width Δt by the AND gate 221, and the gate 22
Supply to 2.

Pulse P4 is shown in FIG.

The other input to the gate 222 is the pulse obtained by the gate 223, which is configured to pass the determination pulse P4 only when VaH5 does not appear and output it to the data counter 22a as a signal Va.

In this way, the dead time (dead time) with a constant width Td
e), it is possible to remove the effects of chattering caused by the comparator and harmonic noise contained in the input pulse V2, and obtain an output pulse Va equal to the number of input pulses in a predetermined range of VaL<V2<VaH.

In addition, in Fig. 9, the broken line indicates the input pulse ■2 is V a H
This shows a case where the peak value is <V2. In this case, since the FF 217 is set, the gate 222 prevents the judgment pulse P4 from passing, and the output Va does not appear.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams showing the prior art, Figure 3 is a diagram showing an embodiment of the present invention, and Figures 4 to 6 are diagrams for explaining the operation of an example of a real axis of the present invention. 7 and 8 are diagrams showing variations of the present invention, respectively, and FIG. 9 is an operation waveform diagram of the variation shown in FIG. 8. 19...X-ray detector, 20...Amplifier, 21a-21n...Discriminator, 2
2a~22n...Data counter, 23a~2
3n...Data buffer memory, 24...
. . . Interface circuit, 25 . . . Judgment unit.

Claims (1)

[Scope of Claims] 1. An X-ray generator that irradiates X-rays to the printed material to be inspected that is being conveyed; an X-ray detector that outputs a signal with a number of pulses proportional to the number of pulses, and a pulse peak value signal corresponding to the specific contained elemental substance is extracted from the pulse signal of this X-ray detector, which is provided corresponding to the specific contained elemental substance. a discriminator, and a counter that is provided for each discriminator and counts the pulse peak value signal at regular time intervals in order to detect the content distribution concentration of the specific contained element substance on the printed matter to be inspected in minute division units. , a memory for storing the count output for each minute classification unit, and a determination circuit that compares the stored contents of this memory with pre-stored characteristic data of genuine printed matter and determines whether the printed matter is correct or not. A printed matter inspection device characterized by: 2 The discriminator sets a dead time close to the pulse width of the output pulse from the X-ray detector using a comparator for upper and lower limit values of the wave height and an output pulse obtained from this comparator for the lower limit value, and sets a dead time close to the pulse width of the output pulse from the X-ray detector. Printed matter inspection according to claim 1, further comprising a logic circuit that determines the appropriateness of the pulse height value depending on whether or not there is an output of the upper limit value comparator within a time. Device. 3. An X-ray generator that irradiates X-rays to the printed material to be inspected that is being transported, an X-ray detector that extracts the fluorescent X-rays generated from the printed material as an electrical pulse signal, and an output pulse of this X-ray detector. a first counter that counts the number of pulses of the signal whose peak value is above a predetermined upper limit threshold; and a first counter that counts the number of pulses of the output pulse signal of the X-ray detector whose peak value is above a predetermined lower limit threshold. a second counter for counting, a means for clearing the first and second counters at every fixed sampling time, and a count value of the second counter to a count value of the first counter at every sampling time; 1. A printed matter inspection device comprising: a subtraction circuit for subtracting , and a memory for sequentially storing the output of the subtraction circuit.