JPH0443468A - Method for inspecting printing of character - Google Patents

Abstract

PURPOSE:To easily and speedily retrieve a reference picture by comparing the compression pattern of character to be inspected with respective compression patterns of a standard compression pattern group, retrieving the most approximated compression pattern, setting a picture equivalent to the approximated compression pattern to be the reference picture, comparing it with the picture to be inspected and judging whether it is good or not. CONSTITUTION:Compression patterns WH, WL, SH and SL are formed by compressing a binarization picture and second patterns SIH and SIL obtained by shifting the standard compression patterns SH and SL in all directions for respective pixels at every pixel are formed. The standard compression pattern group is formed by the standard compression patterns SH and SL and the second patterns SIH and SIL. The inspection compression patterns WH and WL to be inspected are compared with the standard compression pattern group. The most approximated and shifted compression pattern is selected among the pattern group and the shifted picture is compared the picture to be inspected with the shifted picture equivalent to the compression pattern as reference so as to decide it to be good or not. Thus, the reference picture can easily and speedily be retrieved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a character printing method for determining the quality of printing of characters (including symbols, etc.) such as a product number printed on a carton or the like. .

[Conventional technology]

Generally, visual inspection is used to judge the quality of printing of the above-mentioned characters, but this is extremely inefficient.Recently, methods have been attempted in which images are taken with a camera and compared with standard characters.

The test procedure in this case is to superimpose the standard characters and the sample characters, and then start with the standard characters.

It is determined whether the area of the protruding portion is within an allowable value. However, the printed characters on the specimen are not always in a fixed position, and it is common for the characters to be misaligned.

For this reason, the present inventor has previously proposed a method for accurately determining pass/fail even if the sample character group is misaligned with respect to the standard position (Japanese Patent Application No. 2-9754).

[nM that the invention attempts to solve]

This involves imaging a standard character group, constructing a standard image group from this character group and an auxiliary standard image group obtained by shifting this character group by a predetermined pixel in all directions, and then The image is compared with each of the image groups, and the most similar image among the standard IIN image group is used as the reference image to determine the quality.

However, in this case, in order to search for a reference image, it is necessary to compare a large number of images in the standard image group and detect differences therebetween, which poses problems such as the need for a considerable amount of time.

In view of this, the present inventor aims to simplify the detection of the positional deviation of the specimen with respect to the position of the standard, and to quickly perform the search for the reference image.

[Means for Solving the Problems] The present invention has been made to achieve the above object, and consists of photographing standard characters and sample characters with a camera, binarizing each image, and converting each image into a binary image. A compressed pattern is formed by compressing the image, a second pattern is formed by shifting the standard compressed pattern by one pixel at a time in all directions, and the standard compressed pattern and the second pattern form a standard compressed pattern group. , select the most similar shifted compression pattern from this pattern group by comparing the specimen compression pattern with a group of standard compression patterns, and then combine this shifted image and the specimen image using the shifted image corresponding to this compression pattern as a reference. It is designed to compare the quality and quality of the product to determine whether it is good or bad.

In this case, the compression pattern is a horizontal compression pattern in which the binarized image is divided into equal intervals in the vertical and horizontal directions, and the number of binarized images in each division is accumulated and arranged in the vertical direction. , and vertically compressed patterns arranged in a multiplicative manner in the horizontal direction.

[For production]

The compression pattern of the sample character is compared with each compression pattern of the standard compression pattern group, and the most similar compression pattern is searched. Unlike the comparison of entire characters, the comparison in this case can be performed in a short time because it is a compressed pattern.

Once the approximate compression pattern is determined, an image corresponding to this is used as a reference image and compared with the sample image to determine whether it is good or bad.

〔Example〕

The figure shows an embodiment of the character print inspection method of the present invention.
The figure is a flowchart. The character to be inspected is the character "4", and FIGS. 2 and 3 show images of the standard character S and the sample character W, respectively, and their binarized images. However, A is a mask that surrounds the characters, and PI is a mask that does not detect images.
FF pixel, P2 is standard image detection pixel, P3
P4 is a reference pixel for position measurement, which will be described later, and P4 is a sample image detection 1iii. In addition, each IN element is
Although actually there are a plurality of pixels, the screen is divided into equal intervals in the vertical and horizontal directions, and a plurality of pixels in each division are shown as one pixel.

Further, the lower sub-pixel P3 is, for example, the upper left pixel in the mask A as shown in the figure. Note that the mask A is made to have an appropriate size compared to the character image. Below, the standard @Cumulative P3 is shown as a prison seal.

The quality of printing of the sample character W is determined by matching it with the standard character S, but the print position of the sample character does not always match the position of the standard character, and usually misalignment occurs. Therefore, the standard character is shifted in all directions to form a second standard, and the standard character that matches or is in a similar position to the sample character is detected and compared.The present invention serves as a means for detecting the standard character that matches or is in a similar position to the sample character. The user creates a compression pattern (described later) for each IN series and searches using this pattern.

That is, the binarized values in the mask A are accumulated in the vertical and horizontal directions (hereinafter referred to as compression). As a result, the standard character S has compressed numbers in the vertical direction as *012251000 (hereinafter referred to as vertical compression pattern SH), and compressed numbers in the horizontal direction as *00122510 (hereinafter referred to as horizontal compression pattern SL), and the sample character W has as follows: The compressed character is *001226110 (hereinafter referred to as vertical compression pattern WH), and the horizontally compressed character is *11226100 (hereinafter referred to as horizontal compression pattern WL).

Next, the standard character S is shifted vertically and diagonally by n pixels (hereinafter referred to as 1 pixel) in each division section to form second images Sl, 82°S3, etc. (Fig. 4). Vertical compression pattern SIH, S2H
...and horizontal compression pattern SIL.

S2L... (hereinafter collectively referred to as the second pattern group) and the above standard compression pattern SH
, SL form a standard compression pattern group B.

However, St is an image shifted upward by 1, and the vertical compression pattern SIH is the same as the vertical compression pattern SH of the standard character S, but the horizontal compression pattern SIL is
* The bifurcated pattern S3 of 01225100 is an image shifted one pixel to the right, and the horizontal compression pattern S3L is the same as the standard horizontal compression pattern SL, but the vertical compression pattern S3H is 01223410.

Further, S7 is shifted by one pixel to the right and upward, and the vertical compression pattern S7H is *00123
4100, or the horizontal compression pattern S7L is *012
It becomes 25100.

Next, the compression patterns WH, WI of the specimen W are combined with the standard characters of the standard compression pattern group B and the second pattern group S.
t, S2... Each vertical compression pattern SH, SIH, S
2H... Lateral compression pattern SL, SIL,
Compare with S2L...

According to the above embodiment, the compression pattern of S7 of the second image and the compression pattern of the specimen are compared as follows.

Comparisons with other second images will be omitted, but when using this example, it can be seen that the above S7 is the most approximated position (by adding the absolute value of the difference, the one with fewer salmon was approximated) The pattern of the second image S7 is assumed to be the reference pattern SS (FIG. 1).

Next, an image provided with this reference pattern is selected from the standard compression pattern group B, the image S7 is used as the reference image, and this binarized image and the sample binarized image are superimposed and compared. The outline is shown in Figure 5.

However, the binarized detection pixel P5 of the reference image S7 is indicated by an O symbol, and the specimen detection pixel P4 is indicated by an
Pixels where the sample character W does not exist (hereinafter referred to as mismatched pixels), and only X marks indicate sample characters W that protrude from the reference image S7 (hereinafter referred to as protruding pixels), and these numerical values are measured. On the kindergarten side, there is one mismatched pixel and three protruding pixels.

A pass/fail judgment circuit examines whether this number is within a preset tolerance range and judges whether it is good or bad.

Note that in the above embodiment, the compression pattern is a binary value (O
Although an example has been shown in which the numbers N ) are integrated, as other compression patterns, only the presence or absence of the ON value may be input. FIG. 6 shows the vertical compression pattern SH2 and the horizontal compression pattern SL2 of the standard image shown in FIG. 2 above.

The comparison may be made in the same manner as above.

〔Effect of the invention〕

As described above, in accordance with the present invention, when superimposing a specimen image onto a standard image to determine pass/fail, the images of the specimen and the standard are binarized and then compressed as a means for detecting a reference image that matches the specimen image position. A standard compression pattern group is formed by a standard compression pattern and a second pattern group obtained by shifting this compression pattern in all directions, and the sample compression pattern is sequentially checked on this pattern group to determine whether it matches the specimen. Since the shifted image at the position to be detected is selected and the image at this position is used as a reference image and compared with the specimen to determine the quality, detection of the shifted image described above is extremely easy compared to comparing the entire image by only comparing the compressed pattern. This can be done in a short time, and the reference image can be obtained easily and quickly.

Note that when the above-mentioned compressed pattern is formed from a vertically compressed pattern in which binarized images are accumulated and arranged in the vertical direction and a horizontally compressed pattern in which the binarized images are accumulated and arranged in the horizontal direction, the features of the image can be determined by measuring both patterns. It's enough to understand.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention. Figure 1 is a flowchart of the character print inspection method of the present invention, Figure 2 is an explanatory diagram of the procedure for forming a compressed pattern for standard characters, and Figure 3 is a compressed pattern for sample characters. FIG. 4 is an explanatory diagram of the standard image shift procedure; FIG. 5 is an explanatory diagram of the overlapping of the reference image and the standard image; and FIG. 6 is an explanatory diagram of the compressed pattern formation procedure of another embodiment. . S is a standard image. W is the sample character image, SH, SL
are the vertical compression pattern and horizontal compression pattern of standard characters, respectively. WH and WL are the vertical compression pattern and horizontal compression pattern of the sample character, respectively. B i is a standard compression pattern group.

Claims (2)

[Claims] (1) Photograph the standard characters and sample characters with a camera, binarize each image, compress each binarized image to form a compressed pattern, and apply the standard compressed pattern to one image in all directions. A second pattern is formed by shifting a plurality of pixels pixel by pixel, a standard compression pattern group is formed by this standard compression pattern and the second pattern, and the sample compression pattern and the standard compression pattern group are compared to determine the difference from this pattern group. 1. A character print inspection method, which comprises selecting the most similar compression pattern, and then comparing the reference image with the sample image using the image corresponding to this compression pattern as a reference to determine quality. (2) The compression pattern is a horizontal compression pattern in which the binarized image is divided into equal intervals in the vertical and horizontal directions, and the number of binarized images in each division is accumulated and arranged in the vertical direction. ,
2. The method for inspecting the printing of characters according to claim 1, wherein the character print inspection method is formed from vertically compressed patterns arranged in a horizontal direction.