JPH04299147A - Device for inspecting printed matter - Google Patents

Abstract

PURPOSE:To inspect the quality of printed matters without using sample data, and to make detection of abnormalities in a printing machine possible according to the results of said inspection. CONSTITUTION:Images in all shades on a printed matter P printed with a printer 21 are collected by a image inputting device 24, then converted into binary images having a density value being intermediate between the printing and ground paper with a binary coding circuit 25, and are stored afterward in a frame memory 17. On the other hand, a CPU 11 converts the aforementioned binary images into range images by applying repeatedly slendering processing to said binary images in accordance with a processing program in a program memory 14. Then faultiness of the printing is found based on the number of defective pixels in said range images and at the same time, abnormalities in the printer 21 is detected when the faultiness continues.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed matter inspection apparatus for inspecting the quality of printed matter, such as checking for poor printing of characters.

0002

2. Description of the Related Art Conventionally, as a method for inspecting the quality of printed matter, there is a method and apparatus for inspecting patterns of printed matter, as disclosed in, for example, Japanese Patent Publication No. 1-20477. This is to correct the positional deviation between sample data and specimen data of a printed matter, and then compare them pixel by pixel to determine the quality of the image.

[0003] However, this method has a drawback in that the flexibility of the test is low because sample data is required to perform the test.

Furthermore, since the printed matter itself is inspected, in order to understand the condition of the printing press that produces defective printed matter, other methods such as analyzing the printed matter determined to be defective and estimating the cause are necessary. Work was needed.

[0005]

As described above, in the past, specimen data was required for testing, and therefore there was a drawback that the flexibility of testing was low.

Furthermore, since data having a low degree of similarity to the sample data is simply treated as defective, there is a drawback in that additional work is required to estimate the cause of the printing defect from there.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a printed matter inspection apparatus that can increase the flexibility of inspection and easily diagnose the condition of a printing press.

[Configuration of the invention]

[0009]

[Means for Solving the Problems] In order to achieve the above object, the printed matter inspection apparatus of the present invention includes a collecting means for collecting grayscale images from printed matter printed by a printing machine, and this collecting means. a generating means for generating a binary image from the grayscale image collected by the generating means; a converting means for converting the binary image generated by the generating means into a distance image; The apparatus is comprised of a determining means for determining quality, and a diagnostic means for diagnosing the condition of the printing press based on the determination results of the determining means for a plurality of printed materials.

0010

[Operation] By using the above-described means, the present invention makes it possible to eliminate the need for sample data, thereby making it possible to inspect various miscellaneous printed materials.

Furthermore, since the inspection results can be used as they are, the cause of printing defects can be easily estimated.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a printed matter inspection apparatus according to the present invention.

[0014] In the figure, C controls the entire device.
The PU 11 has a data bus 12 and an address bus 13.
A program memory 14, a working memory 15, an output circuit 16, and a frame memory 17 are connected to each other.

On the other hand, the printed matter P printed by the printing machine 21 is irradiated with light from a light source (not shown) in the middle of the conveyance path 22 . The reflected light from the printed matter P due to this light irradiation is imaged on the line sensor 23.

The output of this line sensor 23 is captured by an image input device 24 and collected as a grayscale digital image. The output of this image input device 24 is the output of the binarization circuit 2.
5 and is binarized according to two types of binarization thresholds A and B, and then stored in the frame memory 17.

The above-described image input device 24 and binarization circuit 2
5 and the frame memory 17 are synchronized with the output from the timing circuit 26.

Further, the printed matter P that has passed through the line sensor 23 is conveyed as it is through the conveyance path 22 to the stacking device 2.
7.

The program memory 14 includes the CPU 11
It stores processing programs, various control data, reference values, judgment values, etc.

Here, the above-mentioned processing program includes, for example, the setting of the binarization thresholds A and B, the quality determination of the printed matter P, and the detection of abnormalities in the printing press 21.
This is to cause the PU 11 to perform the operations. As the binarization thresholds A and B, values are set such that, for example, a density value intermediate between the print density value and the background density value of the grayscale digital image can be extracted.

The working memory 15 stores the results of each process performed according to the above-described processing program.

The output circuit 16 detects abnormalities in the printing machine by detecting defects or abnormalities in printed matter through the above-mentioned pass/fail judgment, and outputs them to an external device (
(not shown).

FIGS. 2 and 3 show examples of binary image generation in the binarization circuit 25.

The binarization circuit 25 converts the grayscale digital image 201 collected by the image input device 24 into CP
A pixel that takes a density value between the binarization thresholds A and B set by U11 is set to "1", and other pixels are set to "0".
By doing so, a binary image 301 as shown in FIG. 3 is generated. As a result, the frame memory 17 stores the print boundary portion 302 and the faded print portion 303 as “1”.
", otherwise a binary image 301 having a density value of "0" is stored.

When writing of the binary image 301 to the frame memory 17 is thus completed, control of the frame memory 17 is transferred to the CPU 11.

[0026] The CPU 11 executes the processing according to the processing program stored in the program memory 14 described above.
The quality of the printed matter P is determined by specifying the faded portion 303 on the binary image 301, and an abnormality in the printing press 21 is detected based on the determination results for a plurality of printed matter P. Then, these results are controlled to be outputted to an external device (not shown) via the output circuit 16 described above.

Next, the processing by the CPU 11 described above will be explained.

FIG. 4 shows the relationship between the binary image 301 and the distance image 401 for determining the quality of the printed matter P.

The conversion from the binary image 301 to the distance image 401 is performed by repeating the thinning process described later to obtain a density value of "1".
This is achieved by storing the number of times the process is repeated for pixels whose density value changes from 0 to 0.

As shown in FIG. 5, the narrowing process focuses on the attention points 50.
When the density f(x, y) of a pixel 1 is "1", the densities f(x, y-1), f(x-1) of the pixels of four neighboring points 502, 503, 504, 505 are "1". ,y),f(
x+1, y), f(x, y+1) are all "1", the density value g(x, y) of the pixel at the point of interest 501 is set to "1".
”. Also, four neighboring points 502, 503,
The density of pixels 504 and 505 f(x, y-1), f(x
-1, y), f(x+1, y), 1 of f(x, y+1)
If the density value g(x,y) of the pixel at the noted point 502 is always "0", converting the density value g(x,y) of the pixel at the noted point 502 to "0" is specified in the binary image 30.
This is done by applying it to all pixels of one. As a result, for example, as shown in FIG.
1 is converted into a distance image 401 composed of multivalued distance values.

Here, when the binary image 301 in which the density value of the printing boundary portion 302 and the faded printing portion 303 is extracted as “1” is converted into a distance image 401, the distance value of the printing boundary portion 302 becomes , is smaller than the distance value of the faded portion 303 of printing. This is because the print part forming the print boundary part 302 and the background part coexist within one pixel range of the line sensor 23, resulting in an intermediate density value. This is because the portion 302 spans at most several pixels and can only take a small distance value. Therefore, by setting a certain reference value that exceeds the distance value of the print boundary portion 302, pixels in the print boundary portion 302 and pixels in the faded print portion 303 can be distinguished.

Once the pixels in the print boundary portion 302 and the pixels in the faded print portion 303 are distinguished, the number of defective pixels with large distance values in the distance image 401 is then counted. That is, defective pixels in the blurred portion 303 of printing are detected according to the above-mentioned reference value, and the number thereof is counted. For example, if the reference value is "2", the number of defective pixels having a distance value of "2" or more will be counted as "9" in the distance image 401 shown in FIG. 4(b).

The counted value of the number of defective pixels in the faded portion 303 of printing is used to inspect the quality of printed characters, that is, to judge whether the printed matter P is good or bad. That is, a defect due to blurred printing is detected depending on whether the counted value of the number of defective pixels in the blurred portion 303 of printing exceeds a certain determination value. Therefore, the printed matter P can be inspected without using sample data.

Note that FIGS. 6 and 7 show the flow of a series of processes related to determining the quality of the printed matter P described above.

On the other hand, based on the result of determining whether the printed matter P is good or bad, abnormality in the printing press 21 is detected. That is, when the inspection results of a plurality of printed matter P are examined and it is determined that blurring has occurred in a plurality of printed matter P in succession,
It is estimated that an abnormality has occurred in the printing press 21. In this way, the condition of the printing press 21 can be easily diagnosed based on the determination result of the quality of the printed matter P.

Next, the operation of the above configuration will be explained.

FIG. 8 schematically shows the procedure for inspecting the printed matter P.

First, a grayscale image on the printed matter P is formed on the line sensor 23 by light irradiation from a light source. Then, the grayscale image is captured by the image input device 24 and converted into a grayscale digital image. This grayscale digital image is sent to the binarization circuit 25, and pixels having a density value between the density of the backing paper and the density of the ink used for printing are extracted using two types of binarization thresholds A and B. After being regenerated as a binary image 301, it is stored in the frame memory 17.

The binary image 301 stored in the frame memory 17 is converted into a distance image 401 by the narrowing process described above. In this case, since the above-mentioned binary image 301 is made up of pixels from the print boundary area and the faded area of the print, by measuring the shortest distance from the extracted pixel to the unextracted pixel, , the two are distinguished.

Subsequently, the number of defective pixels in the distance image 401 having a distance value exceeding the reference value, that is, the number of pixels classified as a faded portion of printing, is counted. Then, based on this count value, the quality of the printed matter P is determined. That is, when the number of defective pixels exceeds an allowable determination value, a defect is determined.

[0041] If no defect is determined, the above-mentioned processes are repeated until there are no more printed matter P to be inspected.

On the other hand, if the printed material P is determined to be defective, the output circuit 16 outputs "Printed material defective" as the inspection result for the printed material P. In addition, if the determination of failure continues, the output circuit 16 outputs "printing press abnormality" as a result of the diagnosis of the printing press 21.

As described above, sample data can be made unnecessary.

That is, blurred printing is detected from the difference in shading of pixels. This makes it possible to inspect various miscellaneous printed materials without using sample data. Therefore, the flexibility of testing can be increased.

Furthermore, since the test results are used as they are to estimate the cause of printing defects, it is possible to easily diagnose the condition of the printing press.

Furthermore, since it is possible to detect abnormalities in the printing press at the same time as inspecting printed matter, it is possible to reduce the occurrence of printed waste.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without departing from the gist of the invention.

[0048]

As described in detail above, according to the present invention, it is possible to provide a printed matter inspection device that can increase the flexibility of inspection and also easily diagnose the condition of a printing press. .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a printed matter inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram similarly shown for explaining generation of a binary image.

FIG. 3 is a diagram showing an example of a generated binary image.

FIG. 4 is a diagram showing the relationship between a binary image and a distance image.

FIG. 5 is a diagram similarly shown for explaining conversion to a distance image.

FIG. 6 is a flowchart similarly shown to explain the first half of a series of processes related to determining the quality of printed matter.

FIG. 7 is a flowchart similarly shown to explain the second half of a series of processes related to determining the quality of printed matter.

FIG. 8 is a flowchart similarly shown to explain the procedure of processing related to inspection.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11...CPU, 12...Data bus, 13...Address bus, 14...Program memory, 16...Output circuit, 17...Frame memory, 21...Printing machine, 23...Line sensor, 2
4... Image input device, 25... Binarization circuit, 201... Grayscale digital image, 301... Binary image, 302... Boundary portion of printing, 303... Blurred portion of printing, 401... Distance image.

Claims (1)

[Claims] Claim 1: A collection means for collecting grayscale images from printed matter printed by a printing press, a generation means for generating a binary image from the grayscale images collected by the collection means, and a binary image generated by the generation means. a converting means for converting a value image into a distance image; a determining means for determining the quality of the printed matter from the distance image converted by the converting means; 1. A printed matter inspection device characterized by comprising a diagnostic means for diagnosing the condition of the machine.