JPS60107549A - Inspection of printed matter - Google Patents

Abstract

PURPOSE:To remove quickly the cause of a printing fault and to decrease paper loss by calculating differentially a scanned detection signal and a reference signal and discriminating the kind of the printing fault from the generating sequence of the rise and fall in the change part of the resulted signal and the time between the same. CONSTITUTION:A pulse appears at the upper limit threshold with a delay for specified time after generation of the pulse exceeding the lower limit threshold level as shown in the figure (a) in the case of water sagging or oil sagging. The lower limit threshold pulse appears conversely after generation of a pulse at the upper limit threshold as shown in the figure (b) in the case of ink staining. A pulse is generated on the opposite side in the state of having virtually no time delay after generation of a pulse at the threshold of either the upper or lower limit as shown in the figure (c) in the case of sticking. The king of the printing fault is thus discriminated from the two data; the sequence of the rising pulse and falling pulse appearing with one printing fault and the time between the two rising and falling pulses appearing with one printing fault.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a printed matter inspection method for in-line comparing the state of a printed matter being printed with a standard state in a printing press to detect abnormalities in the printed matter.

Traditionally, inspection of printed materials relies on human vision offline.
The mainstream method is to just do it. This is printed 1
This comes from the fact that each point has a different pattern, and the inspection items on printed matter have been thought to involve subtle differences that require relying on human vision. On the other hand, in response to the desire to evaluate printed matter while it is being printed, attempts have been made to use strobe lighting synchronized with the printing speed and to use mirrors that rotate synchronously at high speed to judge printed matter being printed as a still image. It's been coming. However, these methods were not systems that could be called inspection machines in that they relied on human vision for inspection. Attempts have also been made to print a color punch at the same time as the pattern on the printed matter and to perform the inspection of the printed matter instead of inspecting the color punch. However, with this method, if a printing problem (oil dripping, stains, etc.) occurs in the pattern area, it will be overlooked, and it could not be said that the function of the inspection machine was fully fulfilled.

On the other hand, recently, Japanese Patent Application No. 1051/1983 or Japanese Patent Application No. 1987-
As seen in ``Print Inspection Apparatus'' published in Japanese Patent No. 2201515, a system has been proposed in which printed matter is inspected inline using a line sensor. By using this method, the pattern itself of printed matter can be automatically inspected in-line, which eliminates the above-mentioned drawbacks (but can be expected to have excellent effects as an inspection machine).

However, there is a growing desire to not only detect printing failures (but also to automatically analyze the causes of printing failures).In other words, there is a need to automatically detect and analyze the causes of printing failures.In other words, there is a need to automatically perform alarms, markings, and rejects on defective prints found by inspection machines. Even if countermeasures are taken, it is possible to detect and eliminate defective printed matter, but if the cause of the printing failure cannot be discovered quickly, it will take time to remove the cause of the printing failure, resulting in a large number of defective printed matter. For this reason, a function is required to classify and display to the operator the type of printing failure that has occurred.If such a function works effectively, the operator can quickly eliminate the cause of the printing failure. , paper waste is reduced.

Therefore, an object of the present invention is to provide a printed matter inspection method that makes it possible to determine the type of printing failure (ink stain, water drip, oil drip, cypress, etc.) that has occurred on the printed matter. be.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 shows a schematic diagram of a print inspection device to which the present invention is applied. In FIG. 1, the printed matter inspection device is attached to a rotary press, but there is no problem even if it is a single-fed printing press.

In Figure 1, a strip of printing paper (3) fed from a roll of paper (2) is sent to the printing section (1) in four colors (black, indigo,
After each color (red, yellow) is printed, the dryer and folding machine (
(not shown). The printed matter inspection device inspects the printing condition after the front and back sides have been printed in four colors.The rotary encoder (5) attached to the printing section is used to determine the timing of sampling, and the image information is sent to the detection section (
4) Each pixel divided by a licensor such as COD is input into a processing circuit (6) and a judgment operation is performed. As a result,
If the printing condition is determined to be abnormal, an alarm will be issued.
This makes it possible to take measures such as marking and rejecting.

Further, in the present invention, by performing the following processing on the detection signal from the detection unit (4), it is possible to automatically analyze the cause of printing failures.

For example, on the display, oil drips, water drips, ink stains, etc.
A display function for cypress, etc. is added. Here, oil sauce,
We will explain the classification of water drips, ink stains, and cypress, but omit explanations about other factors.

FIG. 2 shows a model diagram of the reference signal BS (indicated by a solid line) and the detection signal DS (indicated by a dashed-dotted line) when each printing failure occurs. As shown in FIG. 2(A), water dripping and oil dripping have the characteristic of causing printing failure over a wide area and reducing the density. In addition, as shown in Figure 2 (B), ink stains have a characteristic of increasing in concentration over a wide range, and as shown in Figure 2 (C), multiple small obstacles occur on cypress. It is understood that there are characteristics in which both an increase in concentration and a decrease in concentration can occur.

It is the task of the present invention to accurately detect and classify these printing faults. For this reason, the present invention first extracts a signal whose level changes only in the abnormality area of the printed matter by performing a difference between the detection signal and the reference signal,
Second, detection of the rise and fall of the level change portion of the resulting difference signal is performed, for example, differential processing is performed. Printing failures can be classified based on the signals obtained as a result.

FIG. 3 is a model diagram showing the state of the signal DIS after performing the difference between the detection signal and the reference signal described above.

Figure 3 (A), (B), (・→ are respectively Figure 2 (A), (
This corresponds to (b) and (c), and corresponds to water drips, oil drips, ink stains, and cypress. As is clear from FIG. 3, by such differential processing, it is possible to obtain a signal in which a sudden signal change is observed only in the portion where the printing failure has occurred.

Further, FIG. 4 shows a signal obtained by performing differential processing, for example, in a differentiating circuit on the signal after differential processing as described above. Note that the dotted line indicates the threshold level. According to FIG. 4, each signal waveform has characteristics unique to the cause of the occurrence, with respect to the threshold level provided for detecting the occurrence of each printing failure. That is, as shown in Figure 4 (a),
For water and oil sauces, after a pulse is generated that exceeds the lower threshold level, it is held for a certain period of time, and then a pulse appears at the upper threshold. As shown in FIG. 4(B), in the case of ink stains, on the contrary, a pulse is generated at the upper threshold and then a pulse is generated at the lower threshold. In addition, as shown in FIG. 4(A) for Hinoki, pulse generation can be observed on the opposite side with almost no time delay after pulse generation at either the upper or lower threshold level. This is because the image information captured by the line sensor of the detection unit (4) is 1 to 2%φ per pixel, whereas the size of the cypress is about 1 to 4Xφ, which is 1
This is because the time delay phenomenon does not appear.

Therefore, for a print fault, which of the upper and lower thresholds is exceeded by the pulse that appears first, i.e. in the order of rising, falling, and
It becomes possible to determine the type of printing fault from two data of the time between the two rising and falling pulses that appear for each printing fault.

It should be noted that the detection of rising and falling edges of printing faults by the differential processing described above is not limited to the literal differential processing (other processing methods that can achieve the same purpose, such as differential processing) It is also possible to use a method of detecting rising and falling edges by subtracting a detection signal obtained by delaying the detection signal by several pixels and a detection signal without delay processing.

Furthermore, although it deviates from the gist of the present invention,
Set the image information to be input as R (red), G (green), or B.
By classifying which signal the abnormality occurred in as a 6-branch signal through a (blue-violet) filter, it is possible to determine whether the problem occurred with yellow, red, indigo, or black ink. be. In other words, R
If there is an abnormality in the signal passed through the filter, indigo ink,
If the signal has passed through the G filter, then the ink is red, if the signal has passed through the B filter, the ink has been yellow, and if all of the R, G, and B signals are present, the ink is black, and so on.

As described above, by separating into three signals of RGB, it becomes possible to classify each ink by color.

Next, one embodiment of the method of the present invention will be described based on the block diagram of FIG. Although FIG. 5 shows a block diagram of a processing circuit that can implement the method of the present invention, the present invention is not limited to this embodiment (the circuit may be modified without departing from the spirit of the present invention). It is possible to change the configuration and process using software.

As shown in FIG. 1, based on the line 7 y pulse T M P K generated by the rotary encoder (5) attached to the printing section, the timing control section α
η controls the memory control section α0 and the sampling control section α mark. Memory control section (
161 is the signal of the timing control section 07) and the CP
Controls the difference circuit (9) (reference signal import mode and inspection mode) by importing the reference signal SSS to the reference memo IJ-(8) according to the mode switching signal MSS from U (141). Sampling control unit α Bile detection Department (
4) Transfer lock and sampling start signals to the CCD line sensor. Timing and switching are controlled by the above circuit.

Next, the inspection signal SI8 input from the CCD line sensor of the detection unit (4) is converted into a digital signal via the A/D converter (7), and then stored in the reference memo IJ-(8) in the reference signal import mode. be done. On the other hand, in the test mode, the digitized test signal (s) is directly transferred to the difference circuit (9). At this time, the reference signal SSS is read out based on the control signal from the memory control section and simultaneously transferred to the difference circuit (9). The relationship between the test signal SIS and the reference signal SSS at this time is, for example, as shown in FIG. is obtained.

This differential test signal DIS is transferred to a differentiator circuit 00) and subjected to differentiation processing to become a differential test signal DDS. The differential test signal DDS has a signal form as shown in the model diagram of FIG. 4, for example. This differential test signal DDS is branched into two and transferred to an upper limit threshold circuit (ID) and a lower limit threshold circuit (12+). The value of is set.

When a pulse exceeding this upper/lower threshold threshold level is generated, the counter (
A pulse signal indicating that the upper and lower limits have been exceeded is sent to the counter (I3), which causes the counter (I3) to use the odd-numbered signal as a start signal and the even-numbered signal as a stop/reset signal. count.

The counter (13) outputs as the abnormality detection signal IR8 whether the pulse signal from the upper threshold threshold circuit U is used as the count start signal or the pulse signal from the lower threshold threshold circuit (12j) is used as the count start signal. The distinction and count amount are transferred to the CPU (141).The CPU Q41 outputs the abnormality detection signal IR8.
Based on the following criteria, it is determined whether the abnormality is caused by oil dripping, water dripping, ink stains, or cypress. That is, the pulse signal from the lower limit threshold circuit f121 is used as a start signal, and the upper threshold circuit generated by opening for a certain period of time [111] is used as a stop/reset signal for water dripping or oil dripping. On the other hand, if the pulse signal from the upper limit threshold circuit 021 is used as the start signal, and the pulse signal from the lower limit threshold circuit 021, which is generated by opening for a certain period of time, is used as the stop/reset signal, it is an ink stain. It can also be considered as an upper limit thread.

The pulse signal from either the threshold circuit I or the lower limit threshold circuit +121 is used as the start signal, and the lower limit threshold circuit (
121 or the upper limit threshold circuit (LD) as a stop/reset signal can be determined to be a cypress.

In addition, the counter [
31 (as described above) (without serving as both a stop signal and a reset signal, and acting only as a stop signal, and a reset signal as a pulse signal emitted by detecting the end of one picture, for example. If you use If we adopt a method that determines that there is a printing failure when the print quality exceeds this level, it will be possible to appropriately detect cases where the overall design is defective due to the occurrence of many small abnormalities that are not considered to be printing failures individually. can be dealt with.

Furthermore, the detection unit (4) divides the detection signal into three colors R = o, B, and passes them through the processing circuits described above to the CPU α.
If the abnormality occurrence signal IR8 is inputted separately for bleeding, it can be determined whether the abnormality has occurred in black, indigo, red, or yellow ink.

As a result, the CPU (141) can display on the display circuit (I5) the presence or absence of a printing failure and the color of the ink that caused the occurrence of the problem to the printing press operator, and the operator can quickly correct the printing failure by following the instructions on the display circuit. can be removed and printing paper loss can be minimized.

As detailed above (1) According to the present invention, it is not only possible to detect whether or not a printing fault has occurred in a printed matter (but also to detect whether or not a printing fault has occurred in a printed matter). This makes it possible to quickly identify the cause of printing failures, such as oil drips, water drips, oil drips, water drips, etc., allowing the cause of printing problems to be quickly discovered, allowing for smooth removal of the causes, and more efficient printing operations. This is what makes it possible.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the schematic configuration of the print inspection device, Figure 2
The figure is a signal model diagram of a printing failure, Figure 6 is a signal model diagram after differential processing, Figure 4 is a signal model diagram after differential processing, and Figure 5 is a signal model diagram after differential processing.
The figure shows a block diagram of a processing circuit according to one embodiment of the invention. (4)...Detection section (8)...Reference memory (6)
... Rotary encoder (9) ... Differential circuit tl (1) ... Differential circuit Q4
1...CPTJ Patent Applicant Figure 1, Singing 1, Figure 3, Figure 4, Figure 5

Claims (1)

[Claims] 1) In a method of inspecting abnormalities occurring in a printed matter by comparing a detection signal obtained by optically scanning a traveling printed matter with a reference signal, by calculating a difference between the detection signal and the reference signal. Extract the signal whose level changes only in the abnormality area of the printed matter, detect the rising edge and falling edge of the level changing area for the signal obtained by differential calculation, and determine the order in which the rising edge and the falling edge of the level changing area occur, as well as the rising edge. and a method for inspecting printed matter, characterized in that the type of printing failure is determined based on the time between falling edges.