JPH0230536A - Checking method of density fluctuation in printed matter - Google Patents

Abstract

PURPOSE:To check the abnormality occurring in a printed matter to enhance a checking speed by comparing a detection signal obtained by optically scanning the printed matter running with a detection signal of a normally printed matter as a reference signal which has been previously detected by the same method and stored. CONSTITUTION:Image information of a printed matter which is running is accumulated in a processing circuit 6. The processing circuit 6 has both reference information storing the image pattern of a normally printed matter and check information storing the image pattern of a printed matter successively fed. An ink density fluctuation is caused by the excess or shortage of an ink amount supplied to a plate cylinder 8 from an ink key mounted on a printing part 1. Therefore, the density fluctuation may be detected by every width of the ink key controlling the ink amount. Then, the reference information is divided correspondingly to the respective ink keys, the representative reference information in the respective blocks are extracted, and reference data is formed. Additionally, the check information is extracted correspondingly to the reference data, and check data is formed. Then, the reference data and the check data are compared with each other. If the difference is more than a predetermined value, the printed matter is judged to be of unsatisfactory density.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applied to a printed matter quality inspection device for inspecting the deprinting of a pattern such as a single character on printed matter, and various stains occurring on printed matter. This invention relates to a method for testing concentration fluctuations.

[Conventional technology]

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 methods were not systems that could be called inspection machines in that they relied on human vision for inspection. Attempts are still being made to print color notches at the same time as the pattern on the printed matter and inspect the color patches instead of inspecting the printed matter. However, with this method, printing failure (
If oil drips, dirt, etc.) occur on the pattern, it will be missed, and the inspection machine cannot function properly.

On the other hand, recently, Japanese Patent Application No. 1051/1983 or Japanese Patent Application No. 1987-
22051.5, etc., a system that inspects printed matter in-line using a line sensor has been proposed, as seen in the "Printed Material Inspection Apparatus" proposed in No. 22051.5. The outline of this system will be explained based on FIG.

A strip of printing paper (3) is fed from a roll of paper (2) attached to a part of the feeder of the printing machine, and after being printed in the printing section (1), machine (not shown). In order to inspect the printing condition after printing, the printed matter inspection device uses a rotary encoder (5) attached to the printing section to determine the sampling timing, and the image information is sent to the processing circuit from the line sensor of the detection section (4). (6) Perform 1 judgment work.

As a result, if it is determined that the printing condition is abnormal, it becomes possible to take measures such as alarms, markings, and rejects.

[Problems to be Solved by the Invention] In FIG. 1, the image information input from the detection unit (4) plays two roles in the processing circuit (6): reference information and inspection information. Ru. The reference information is the image information of the pattern of the printed matter at the time when the printer determines that the printing is normal, and the image information is stored in the reference information memory,
This is the standard for inspection. On the other hand, inspection information is information that is input from the detection unit (4) after the reference information has been stored in the memory, and is compared (difference, differentiation, etc.) with the reference information to determine a predetermined tolerance range. By determining whether the printed matter is good or bad by determining whether it exceeds the above limit, it becomes possible to inspect the printed matter in-line.

According to such a system, it is possible to inspect the entire pattern of a printed matter, but the amount of reference information and inspection information to be processed is enormous. Therefore, conventional inspection devices have complicated structures, slow inspection speeds, and insufficient inspection accuracy. Therefore, the present invention was made in order to study such problems, and its purpose is to provide a method for inspecting density fluctuations of printed matter, which has a relatively simple structure and has sufficient inspection speed and inspection accuracy. It is in.

[Means to solve the problem]

The density variation test according to the present invention, which was carried out in order to solve the above-mentioned problem, is shown in FIG. is the reference data. A portion corresponding to this is extracted from the inspection information and set as an inspection take. The standard data and inspection data are then compared to determine quality defects in the printed matter.

[For production]

Image information of the running printed matter is stored in the processing circuit (6) in FIG. The processing circuit (6) has reference information that stores the patterns of normal printed matter and inspection information that stores the patterns of the printed matter from moment to moment. Changes in ink density can be seen in the printing section (see Figure 1).
1), an ink key (not shown) allows the plate cylinder (8) to
This occurs when the amount of ink supplied to the printer is too little or too much. Therefore, density fluctuations can be detected for each width of the ink key that controls the amount of ink.

Therefore, the above reference information is divided so as to correspond to each ink key, representative reference information is extracted within each ink key, and reference data is created.

That's too lenient, we also extract the portion of the test information that corresponds to the standard data and create test data. When the reference data and inspection data are compared and there is a difference of more than a predetermined value, the printed matter is determined to have poor density.

〔Example〕

One embodiment of the present invention will be described with reference to FIGS. 1, 2, 3, and 4. Figure 2 shows an overview of the printed matter. Second
In the figure, one page (9) is a printing unit equivalent to one rotation of the plate cylinder (8) or blanket cylinder (9) in FIG.

The ink control width α corresponds to the width of an ink key (not shown) that controls the amount of ink supplied to the plate cylinder (7) in the printing section (1) in FIG.

Figure 3 shows the storage arrangement of the reference information for 1-:) (9) shown in Figure 2 that was not input to the processing circuit (6) in Figure 1.
This is an example. FIG. 4 shows an example of the storage arrangement of test information for the IR circuit (9) in FIG. 2 that is input to the processing circuit (6) in FIG. 1.

In FIG. 3, the paper width direction is divided into n pieces according to the number of detection elements of a line camera or the like of the detection section (4), and the running direction is divided into m pieces according to the sampling time of the rotary encoder (5). Therefore, the 14-page inspection information is composed of mXn pixels.

Here, it is assumed that the ink control width α■ in FIG. 2 is composed of 2 columns, and there are N columns for the printing paper width.

Here, the reference information for an arbitrary pixel row 1 and j column in the storage array is set as R(i, j), and one column is arbitrarily selected from each ink control width aα. For example, if the sum of the reference information of the ink control width corresponding to the first column is used as reference data and is expressed as RFe, RFe can be expressed by the following equation.

Similarly, in FIG. 4, the sum total of test information in the first column in the test information storage array is set as test data, and D
When expressed as Te, DTe can be expressed by the following formula.

During printing, if the amount of ink supplied by the ink key corresponding to the row is too little or too much, RFe-%DTe will occur.

As normal printing approaches, DTe approaches RFe.

Therefore, if the allowable value for one row in the running direction for normal printed matter is ε, then when DTe-NRe l <,, t --(3), it corresponds to the ink key width of the first row of printed matter. The part can be determined to be normal.

If the above method is applied to all N ink control widths, the entire printed matter will be covered! ! can be inspected.

Here, the comparison unit of the reference data and inspection data in each ink control width 00) may be not only one column unit but also two or more columns as described above.

Divide any one column within the ink control width (10) into M pieces.

You may compare each block.

〔Effect of the invention〕

An ink key width unit generated on a printed matter in a quality inspection method for printed matter that detects the shade of the printed matter by optically combining the printed pattern onto a light receiving element and extracting the intensity of light incident on each light receiving element as an electrical quantity. The detection signal obtained by optically scanning a running printed matter for density fluctuations is compared with the detection signal of a normal printed matter, that is, a reference signal, detected and stored in advance using a similar method. As a result, the first effect is produced by inspecting the abnormality that occurs in the printed matter.

(1) With a small number of comparative tests, it is possible to test for variations in the density of the image of the entire printed matter.1 In addition, it is possible to improve the test speed.

(2) Because it uses numerical control without relying on the visual intuition of the printed matter inspector, it becomes possible to perform density inspections with fixed standards that are independent of the inspector.

(3) It is possible to detect density fluctuations that occur during printing. 1. It is possible to quickly respond to printing defects that occur.
Printing waste paper is reduced.

[Brief explanation of the drawing]

FIG. 1 is an overall view of a general print quality inspection apparatus, and FIG. 2 is an explanatory diagram of a print according to an embodiment of the present invention. FIG. 3 is a storage layout diagram of reference information according to an embodiment of the present invention;
FIG. 4 is a storage layout diagram of inspection information according to an embodiment of the present invention.

Claims (1)

[Claims] Ink key width that occurs on printed matter is a quality inspection method for printed matter that detects the density of printed matter by optically combining the printed pattern on a light receiving element and extracting the intensity of light incident on each light receiving element as an electrical quantity. Compare the detection signal obtained by optically scanning a running printed matter for a unit density variation with the detection signal of a normal printed matter, which has been detected and stored in advance using a similar method, that is, a reference signal. 1. A method for inspecting density fluctuations in a printed matter, the method comprising: inspecting abnormalities occurring in the printed matter.