JPS6063168A - Synchronous deficiency correction for inspection of running printed matter - Google Patents

Abstract

PURPOSE:To elevate the inspection accuracy by differentiating the position of taking in sampling data and the position of taking in synchronous signal to reduce the synchronous deficiency to the level free from any practical problem. CONSTITUTION:Simultaneously with printing of individual patterns 3' of a printed matter 3, a start mark 7 is printed and read with a detecting section 4. Based on the mark 7, the position of starting a specified sampling of patterns 3' is made to coincide with the sampling start signal based on a timing pulse outputted from a rotary encoder 5 to fix the timing of starting the taking-in of pixel information on individual patterns 3'.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for correcting a synchronization failure that occurs when an abnormality in a printed matter is detected by inline comparing the state of a printed matter being printed with a standard state in a printing press.

Conventionally, the mainstream method for inspecting printed matter has been offline and relying on human vision. This is one printed item.
This comes from the fact that the dot patterns are different, and the subtle differences in inspection items on printed matter that require reliance on human vision have been thought to be a problem. 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 was. However, these means 1 (1) were not systems that could be called inspection machines in that they relied on the visual field for inspection.

Furthermore, attempts have been made to print a color batch at the same time as the pattern on the printed matter and inspect the color batch, thereby allowing the inspection of the printed matter to be carried out on behalf of the user. 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.

A system has been proposed in which the inspection is performed in-line using a line sensor. By using this method, the pattern itself of printed matter can be automatically inspected in-line, so it does not have the above-mentioned drawbacks (but can be expected to have excellent effects as an inspection machine.

However, this system handles a large amount of image data at high speed, which causes various problems. In particular, fluctuations in printing speed, synchronization of printing speed and inspection, etc. pose major problems in maintaining inspection accuracy. This issue will be explained in more detail.

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 printing press, but there is no problem in using a sheet-fed printing press as well. In Fig. 1, a strip of printing paper is fed from a roll-shaped web (2), and is printed in four colors (front and back) in the printing section (1).
After being printed in yellow, red, and black, it is transported to a dryer and a folding machine (not shown). The print inspection device is front and back 4
In order to inspect the printing condition after color printing, the rotary encoder (5) attached to the printing section measures the sampling timing and transfers the pattern information of each pattern (3') in a direction perpendicular to the print conveyance direction. Extending detection part (
4) A line sensor such as a CCD scans one line at a time and inputs it to the processing circuit (6).The processing circuit (6) compares the density level with the reference signal, and based on this result, determines whether the printing condition is normal. - Perform work to determine abnormalities. As a result, if the printing condition is determined to be abnormal, an alarm
This makes it possible to take measures such as marking and rejecting.

However, when scanning pattern information using only the timing pulse from the rotary encoder (5), there is no problem as long as the timing pulses are completely synchronized, but in actual inspection, the position of the rotary encoder that takes the timing and the position of the pattern information detection section are very different. Because of the difference in printing speed, tension fluctuations, elastic deformation and plastic deformation of the printing paper, temperature fluctuations in the dryer section, etc., it becomes very difficult to synchronize.

Figure 2 shows normal operation (400 rt) on an off-cent rotary press.
Results of measuring the amount of synchronization deviation of p M ) (synchronization characteristics)
This shows a model diagram of the standard length of several meters/
This shows that there is a variation of about f11.

Further, it can be seen that this variation is a combination of a wave with a large period of several hundred patterns and a wave with a small period of several patterns, and each has a range of approximately several m/I'r1.

In an actual printed matter inspection device, in order to detect minute printing defects such as scratches and stains, it is desirable that one pixel of pattern information taken in from a detection unit such as a CCD line sensor is 2 m/mφ1 or less. However, if it is less than 1 rn/nψ, the amount of information to be handled becomes enormous, making it unreasonable in terms of printing speed.

For example, one pixel is 0.5 m/ImpIF, and the entire AY version (88 m/m wide x 625 m/m long) (1) If it is a printed matter, the amount of information is 2.2 MB, and the printing speed of a rotary printing press is 50 ORPM. If there is, the transfer time per pixel is 5
This is 4.3 nsec, which means that the transfer rate (IQMHz) of a normal line sensor is insufficient.

Therefore, the size of the inspection pixel of printed matter is 1m/mjb ~
Although 2 m/m f is appropriate, the above-mentioned synchronization deviation amount of approximately m/m can be considered to be a major problem in signal processing.

In other words, the scanning lines sampled in accordance with the timing pulses from the rotary encoder will vary each time the signal is taken in, as shown in FIG. In other words, in one scan, pixel information was captured overflowing into scanning lines n, n+1, -, but in the next scan, pixel information was absorbed into scanning lines n', n'+1, -... This will result in: In this state, it is impossible to compare the detected pixel information and the reference signal to determine printing defects.

In addition, the causes of the synchronization failure mentioned above, such as printing speed fluctuations, tension fluctuations, elastic deformation and plastic deformation of the printing paper, and temperature fluctuations in the dryer section, are fluctuations based on the basic mechanism of the printing press, so these It can be said that it is impossible at present to eliminate them completely.

Therefore, the purpose of the present invention is to correct synchronization failures caused by various causes as described above, and to be able to always capture pixel information on a constant inspection line for all printed matter, thereby enabling highly accurate inspection. An object of the present invention is to provide a method for correcting synchronization defects in inspection of printed matter.

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

The present invention is applied, for example, to the print inspection device shown in FIG. According to the present invention, synchronization failures (synchronization deviations) in inspection of printed matter can be corrected by combining the methods described below.

First, as shown in FIG. 4, a start mark (7) is printed at the same time as the individual patterns (3') of the printed matter (3) are printed. The printing position of the start mark (7) is in the side margin of the printed material (3), and is slightly upstream along the printed material conveyance direction A with respect to the upper side (3'') of each pattern (3'). located at or at the same location.

Therefore, each start mark (7) is an individual symbol (3'
) with a physically constant positional relationship with the pattern ( ).
3') will be present on the printed material (3).

Such a start mark (7) is read by the detection unit (4), and based on this, a predetermined sampling start position for the pattern (3') is determined and sampling is started based on the timing pulse output from the rotary encoder (5). By matching the signals, the timing of starting to capture pixel information for each pattern (3') is made constant.

FIG. 5 shows the relationship between the image signals that are actually input continuously from the fixed position B of the detection section (4) and the timing pulses from the rotary encoder.

As a result, as shown in FIG. 5, the rotary encoder (
In response to the timing nozzle from 5), the pixel information from the detection unit (4) is taken in according to the distance in the transport direction between the start mark (7) and the upper side (3#) of the pattern (3'). If the sampling is started with a delay of N pulses (in this example, 6 pulses), sampling can always be started from a fixed position with respect to the picture (3), and the image signal can be input in a stable state.

Next, among the changes in the amount of synchronization shown in FIG. 2, the influence of large waves with a cycle of several hundred pictures is excluded. For this purpose, as shown in Fig. 6, the average value (indicated by the dotted line) of the amount of synchronization in one cycle length of a plurality of pictures (for example, a set of 5 to 20 pictures) is calculated. Calculate,
This is fed back to correct the amount of synchronization difference between the pattern and period length of the next set. This makes it possible to substantially eliminate the influence of long-cycle waves. Note that using the average value of the synchronization difference between a certain number of pictures and the cycle length to correct the IQ synchronization difference of the next picture is difficult because the wave cycle is long, several hundreds of pictures, so There is no problem because the difference between the average values of ℃・ is extremely small.

This process will be explained in more detail using a model case.

The noise emitted from the rotary encoder between the detection of the start mark (7) provided for each pattern (3') of the printed matter (3) and the next start mark (between force detection (that is, corresponding to the length of one cycle of the pattern)) Assume that the number of pulses is normally 1006, and that a synchronization deviation amount as shown in Table 1 below occurs.

The amount of synchronization deviation in Table 1 is a measurement of how much each picture is out of synchronization compared to a state where there is no synchronization deviation.

First, as described above, as a means to stabilize the sampling start timing, if scanning is started with a delay of N pulses, for example, 6 pulses, after the start mark is detected, in effect, the 6 pulses are Since it is excluded from the sampling target, the actual sampling area is for the next 1000 nm.

Assuming that the number of samplings is 100 scans for one picture, state S where the synchronization difference is 0 is 1000 pulses/scanning.
It would be better to send a sampling start signal that scans once every 10 pulses in 10 scans to the pattern detection section (4), but in reality, due to the synchronization difference shown in Table 1, the scanning line will be incorrect if left as is. It is stable, and large deviations occur for each pattern. For this purpose, in this model case, the average value of the synchronization deviation in the pattern-period length of 10 pictures is calculated based on the normal state. Taking Table 1 as an example, the 1st to 10th sheets are 16th pulse, and the 11th to 20th sheets are 15th pulse.

In other words, the 1000 pulses during normal operation become 994 pulses on average for the 1st to 10th sheets, and 995 pulses for the 11th to 20th sheets, causing synchronization failure.

In order to correct this deviation, if the necessary correction amount is 16 pulses, this value is fed back, and the next set of symbols is 10 pulses.
0 scan/6 pulses - 17 scans, and the sampling start signal is transferred every 17 scans (6 times in total) with 9 pulses instead of 10 pulses.

Also, if the required amount of correction is 15 pulses, similarly 100
The sampling start signal is set to be transferred at an interval of 1 scan and 9 pulses every 20 scans (5 times in total) so that the scan is 15 pulses minus 20 scans.

By sequentially performing such processing, it is possible to almost eliminate the synchronization difference in the average of 10 pictures, and therefore, when viewed as a whole, the long-period synchronization difference can be eliminated. In addition, in this specific example, we have explained a case in which it is combined with a means for making the sampling start timing constant, but even if such a means is not adopted, this processing can be applied, and in that case, starting from the start mark Since the period until the first sampling is not determined, the entire area from one start mark detection to the next start mark detection (1006 pulses in this example) becomes the sampling target area, and the following steps are followed in the above explanation. By determining the sampling timing, it is possible to almost eliminate the average synchronization difference between multiple pictures.

In this way, by calculating the average value of the synchronization deviation amount of the pattern-period length in units of multiple images, and correcting the synchronization deviation amount of the next set of multiple images based on this average value, it is possible to As shown in FIG. 7, the synchronization failure that appears as a large wave with a long period can almost be eliminated.

Further, according to the present invention, the influence of short-cycle waves every several pictures is reduced to a negligible level.

As shown in FIG. 3, n,
It is assumed that the scanning lines n+1, n+2, .

By averaging the pixel information captured in these two scans, a virtual scanning line is set between the two, and therefore, in this case, the amount of deviation can be suppressed to M/2m/m.

The number of scans to be averaged to obtain a virtual scan line (
The number of symbols) is not limited to two, but may be three or more. However, when looking at the occurrence characteristics of printing defects, for example, printing defects due to water dripping may occur only on the minimum number of prints. The level may be absorbed by the density level of the remaining normal image, making it impossible to detect printing defects. Therefore, the number of target patterns for the averaging process is set such that printing defects that occur randomly on the pattern (
Considering the frequency of occurrence of oil dripping, water dripping, etc., it is preferable to use about several sheets.

Figure 8 shows the state in which the averaging process (number of target pictures: 2) has been performed using the above method on the synchronization characteristics in the state where the long-cycle synchronization deviation shown in Figure 7 has been resolved. ing. As a result, the amount of synchronization deviation is approximately 11% compared to the state shown in Figure 6.
5, and was hardly affected by the synchronization deviation, and it can be said that the synchronization failure was substantially eliminated at this point.

The method described above makes it possible to suppress synchronization failures to a level that causes no practical problems, but in actual inspection, the reference signal to be compared with the inspection signal is first captured from a normal printed matter. It turns out. If this reference signal is taken in with a synchronization difference, the reference signal itself is not accurate, and subsequent testing becomes essentially meaningless. To prevent this from happening, it is necessary to take in as a reference signal a signal at the time when the amount of synchronization deviation is 0, or to take in the average of the test signals of a plurality of sheets (sufficiently large) as a reference signal. As a result, the print inspection apparatus can compare and discriminate between the inspection signal and the reference signal while minimizing the amount of error in the detection signal due to synchronization deviation. For comparison and discrimination, see ``Printed material inspection device'' in Japanese Patent Application No. 55-1051, ``Printed material inspection device'' in Japanese Patent Application No. 58-2540, or ``Printed material inspection device'' in Japanese Patent Application No. 58-4047. Although such a processing circuit has been proposed, since the main purpose of the present invention is to correct synchronization failure in a print inspection device, detailed explanation thereof will be omitted here.

Next, an example of the apparatus used in the method according to the present invention will be described in detail with reference to FIG. 9.

FIG. 9 shows a block diagram of a signal processing circuit in one embodiment of the present invention. Here, based on the method described above, the reference signal is an average signal of signals captured from several consecutive pictures, and the feedback value for eliminating waves with a large period among the synchronization deviations is the continuous 10
In addition, the averaging process for eliminating waves with small cycles among the synchronization deviations is performed by averaging the test signals of two consecutive pictures. Note that the present invention is not limited to the above conditions and can be carried out without problems within the conditions given in the above explanation.

A detection unit (4) consisting of a CCD line sensor etc. and a rotary encoder (5) installed in the positional relationship shown in FIG. The pattern information and timing pulse of the printed matter (3) are taken into the processing circuit.The timing pulse TP from the rotary encoder (5) is detected by the detection section (4) prior to or simultaneously with the detection of the pattern (3I). The start mark (start mark pulse SMP generated by detecting the force) is counted at the counter (22).

The first comparison circuit (23) receives the count value of the counter (22) and outputs the first reference count memo! J (24)
(According to the embodiment shown in FIG. 5, N
When a pulse) is reached, this signal is sent to the sampling control section (25), and first, the first sampling start signal SSS is transferred to the detection section (4). Counter (22
), the timing pulse TP from the rotary encoder (5) continues to be counted as the printed matter (3) runs, and ends when the start mark (7) for the next pattern (3') is detected. , a count value using such a start mark pulse SMP as a start, stop, and reset signal is sequentially sent to the difference circuit (26), and the number of pulses N in the first reference count memory (24) is subtracted from this count value. , this result is sent to the averaging circuit (27), which averages the count values for 10 consecutive pictures.

Next, the pulse count value from the start mark to the next start mark excluding the pulse number N up to the first sampling averaged over these 10 pictures and the synchronization difference from the second reference count memory (29) are calculated. A second comparison circuit (2
8), the actual count value (average of 10 sheets) is compared with the reference count value, and the number of additions and deficiencies (i.e., the amount of synchronization deviation) is calculated, and this number of additions and deficiencies ΔP is calculated in the correction circuit (30). Pattern (3') By equally allocating the sampling timing for each image and transmitting the sampling signal CP corrected in this way to the sampling control section (25), the sampling control section (25) sends the signal to the detection section. At this timing (4), the sampling start signal SSS is transferred.

As a result, the long-period synchronization deviation among the synchronization failures is eliminated, and the detection section (4) samples the picture (3').

The analog target signal AO8 taken in from the detection section (4) at such timing is sent to the A/'D controller (-ta (1).
The signal is transferred to the averaging circuit (12) as the digital target signal DO3 that has been digitally converted in step 1). On the other hand, the person in charge of the printing machine can access the CPU (
10), NOP (no inspection) 5IN (
Instructs to switch between three modes: standard signal import) and MNT (under inspection). By switching this mode, the CPU
The mode switching signal MC8 from (10) is sent to the memory control (2).

In the memory control (20), the averaging circuit is set to NO.
In the P mode, no signal is taken in, and in the SIN mode, MN, and T modes, the average value for a predetermined number of sheets is calculated. In the SIN mode, a predetermined number of averaged signals are captured and stored in the reference memory 05) as the reference signal STS. When the reference signal STS is loaded into the reference memory, the SIN mode is automatically switched to the M N 'l' mode. However, there is no problem in manually switching to MNT mode. In the MNT mode, a signal obtained by averaging a predetermined number of digital target signals DO3 from the A/D converter 11 is sequentially transferred to the difference circuit 16 as a monitoring signal. This transfer timing is controlled by the memory control (2), and at the same time, the reference signals ST and S from the reference memory 15 are transferred to the difference circuit 16. As a result, the difference circuit (16) receives the standard signal STS and the standard signal STS shown in FIG. This means that the monitoring signal MNS with countermeasures against synchronization deviation as shown has been sent.

After differential processing is performed in the differential circuit (16) based on the above-mentioned two signals, abnormality in the printed matter is determined in the discrimination circuit (17) according to a preset threshold value. The difference processing and discrimination processing described above are not limited to the methods described above, and may be a combination of differential processing, integral processing, and the like.

c P U (17) is the abnormal signal IR8 from the discrimination circuit.
Based on this, alarms, markings, rejects (21), etc. are performed.

Although the synchronization failure correction method according to the present invention can be achieved by such a processing device, the present invention is not limited to this circuit configuration in any way, and may include other circuit configurations that can achieve the same purpose.
Alternatively, programming using a microcomputer is also possible.

Table 1 below shows an example of model calculation in which synchronization deviation is corrected according to the present invention.

Table 1 As is clear from Table 1, it is understood that a considerable amount of synchronization deviation can be improved to a state where there is virtually no synchronization deviation by the method of the present invention.

As described in detail above, according to the present invention, printed matter is sampled in synchronization with the running state immediately after printing, and printing failures occurring in the printed matter are detected based on the sampling data. Because the synchronization signal acquisition positions are different, it is possible to reduce synchronization failures that occur due to various fluctuations such as tension fluctuations, speed fluctuations, and elastoplastic deformation of printed matter to a level that does not pose a practical problem. Since the inspection can be performed in an accurately synchronized state, the inspection accuracy can be significantly improved.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1 is a schematic diagram of a printed matter inspection device, FIG. 2 is a model diagram of synchronization deviation,
Fig. 3 is a relationship diagram between synchronization deviation and scanning line, Fig. 4 is an example of a start mark, Fig. 5 is a timing chart, and Fig. 6 is a model diagram of feedback amount in a synchronization deviation state.
FIG. 7 is a model diagram of synchronization deviation after feedback, FIG. 8 is a diagram of a synchronization deviation model after averaging processing, and FIG. 9 is a circuit block diagram of a device to which the present invention is applied. 1...Printing machine, 2--roll paper, 3...Printed material, 31
・-Picture, 311...Picture top side, 4・-Detection part, 5・
・Rotary encoder, 6・-processing circuit, 7...
Start Mark Patent Applicant Toppan Printing Co., Ltd. Figures 1-3, 11-11''''''2LLL Todo V Keiyo''-, I9.
B; J++

Claims (1)

[Claims] 1) Occurs during inspection of printed matter, in which printed matter is sampled immediately after printing in a running state in synchronization with timing pulses from a pulse generating means, and the sampling data is processed to detect printing failures that occur in printed matter. In the method of correcting synchronization failure, a value is calculated by averaging the amount of consecutive synchronization deviations in one cycle length of a pattern in a printed matter for a set of multiple images, and this value is fed back to calculate the amount of consecutive synchronization deviations in one cycle length of a pattern in a printed matter. Synchronization failure correction in inspection of running printed matter, characterized by correcting sampling timing, averaging data sampled at the corrected timing for two or more patterns, and using this averaged data as inspection target data. Method.