JPH08272082A - Dot printing and evaluating device of zigzag arrangement - Google Patents

Abstract

PURPOSE: To provide an automatic evaluating means of dot printing of zigzag arrangement. CONSTITUTION: The magnified image of the specified area of a sample subjected to dot printing of zigzag arrangement at a specified density is picked up and the number of the dots ought to exist within this area is previously counted. The presence or absence of chipping, drop-out, etc., is checked with the individual dots by the picked up video signals and the number of the defect dots is investigated, then the ratio of the number of the defect dots to the total number of the dots ought to exist is determined. Since this evaluation is automated, the evaluation of printing is not subjective.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for automatic inspection of staggered dot printing.

[0002]

2. Description of the Related Art When a halftone dot print is enlarged and seen, a halftone dot is originally circular, but a part of the halftone dot is missing, or one halftone dot is completely missing. This is related to the problem of the printing plate, the problem of the ink and printing plate, and the problem of the paper. In order to take measures against each problem, the halftone printing cannot be performed. It is necessary to inspect. However, it takes time for humans to do this visually, and subjectivity tends to be included in the determination. Therefore, in Japanese Patent Publication No. 4-2104, the applicant of the present patent application proposed an automatic evaluation device for halftone dot printing. However, this device is intended for the case where halftone dots are arranged in a square lattice, and cannot be applied to the commonly used staggered halftone dot printing. This is because in the case of the staggered arrangement, it is difficult to count the total number of halftone dots within a certain area.

[0003]

DISCLOSURE OF THE INVENTION The present invention is intended to improve the above-mentioned proposed method of dot printing evaluation so that it can be applied when the dot array is a staggered array.

[0004]

[Means for Solving the Problems] First, a certain area is set on a halftone dot printing surface printed at a constant density, and an enlarged image of the halftone image is picked up. After the data is stored in the memory, the binarized image data is processed to obtain an evaluation value for halftone dot printing. In the binarized video data, the value obtained by counting the number of halftone dots in one row or column of odd number and multiplying it by the number of odd number rows or columns in either the row or column of halftone dots. And the number of halftone dots in an even-numbered row or column, and then multiplying by the value multiplied by the number of even-numbered rows or columns is taken as the total number of halftone dots that should be within the set area. . After that, regarding the above-mentioned binary image data, each halftone dot is judged to be good or bad by a certain criterion, and the total number of halftone dots determined to be defective is obtained.
The ratio to the total number of halftone dots described above is calculated. Or above 2
In the video of the binarized data, the product of the number of the matrix of the remaining halftone dot array with the even numbered rows or columns erased and the number of the matrix of the remaining halftone dot array with the odd numbered rows or columns erased The ratio with the defective halftone dot is calculated as the total halftone dot number by the sum of the product.

[0005]

In the above-mentioned Japanese Patent Publication No. 4-2104, the number of halftone dots that should be within a certain area can be easily obtained by the product of the numbers of rows and columns. In the staggered arrangement, the number of halftone dots is different between the odd-numbered rows and the even-numbered rows. Depending on how to set the boundary of the area set in advance, the number of halftone dots may be the same regardless of whether the lines are odd or even, but the number of lines is different between odd and even. Therefore, it is impossible to uniformly determine the total number of halftone dots. However, if you divide it into odd-numbered rows and even-numbered rows, find the product of the number of halftone dots per row and the number of rows for each, and add both, the number of rows will be Even if it is odd and even, it can be calculated uniformly and all halftone dots can be obtained.

[0006]

【Example】

(Overview) FIG. 1 shows an apparatus according to an embodiment of the present invention.
1 is a main body of a microscope with a television camera or an imaging device,
Reference numeral 2 is an image pickup device, and 3 is a monitor CRT for displaying a microscope image or the contents of an image memory. The sample stage 4 of the microscope is provided with a fine movement device in the x and y directions and a rotation device around the z axis. 5 is a computer (CPU) for data processing,
Reference numeral 6 is an image memory, 7 is a keyboard for setting various parameters and inputting operation commands, and 8 is a display CRT. If you look at a paper with halftone dots printed at a certain density with a microscope,
You can see the array of dots as shown. In the following description, a horizontal arrangement of halftone dots is a row and a vertical arrangement is a column. On the screen of the monitor CRT 3, bright and dark signals in the range of A × B shown in FIG. 2 are stored in the image memory 6. The operator sets a test paper piece printed at a constant density on the sample table 4 and monitors the CRT.
Focus the microscope while looking at 3, rotate the sample stage 4 so that the halftone dot line is parallel to the horizontal scanning line of the CRT 3, and make sure that the halftone dot image does not lie on the boundary line between A and B. As shown in FIG. 2, the sample table 4 is finely adjusted in the x direction and the y direction, and after the adjustment operation is completed, when a start command is given by the keyboard, the CPU 5 stores the image data in the image memory 6. The data processing described later is performed and the result is output to the display CRT 8 and the printer 9. The image memory 6 stores the brightness of the enlarged image of the test paper as, for example, 8-pit data. First, the CPU 5 uses the data in the image memory 6 to binarize the brightness of the image. This binarization is an operation of discriminating into two values that one pixel is a white background portion of a test paper or a printed halftone dot portion. That is, a black and white discrimination level is set, and if it is black above that level, it is black, and if it is below that level, it is white.

Next, the CPU 5 determines the number of rows and columns of halftone dots in the image stored in the image memory 6, that is, the total number of halftone dots that should be included in the A × B range of the image shown in FIG. decide. The number of halftone dots that should be this means that there are missing halftone dots or defective halftone dots that cannot be recognized as halftone dots on the actual printed surface, and the actual number of halftone dots is calculated. Since it is less than the number, it is called a regular halftone dot number. line,
The method of detecting and counting the columns will be described later.

After that, the CPU 5 sets the coordinate range of the inspection area where each halftone dot should exist. As shown in FIG. 3, by setting a square surrounding each halftone dot on the image memory, the addresses x1 and x in the x direction on the two-dimensional memory are set.
2, x3, ... And y-direction addresses y1, y2, y3, .. The range in which one halftone dot should exist is represented by (x1 to x2), (y1 to y2), for example. This range may be set to be wide so that the halftone dots will fit gently, but it is easier to execute the halftone dot evaluation algorithm if it is set as narrow as possible, and the edge of the correct halftone dot will be bitten. You may set it to the rank. This setting is performed in connection with the row and column detection operation described above.

Finally, the CPU 5 evaluates the printed halftone dots in each halftone dot existence range, that is, each halftone dot evaluation area set by the above-mentioned place, and counts the number of defects and missing halftone dots,
Calculate and display% of the total number of halftone dots. The method of halftone dot evaluation is arbitrary. The simplest way of thinking is to count the total number of black pixels from the binarized image data within the halftone dot existing range. This number is the maximum for the correct printed halftone dot, and is reduced if there is a portion lacking in the halftone dot. Therefore, if the number of black pixels is less than or equal to a preset number, it is determined as a defective halftone dot.

(First embodiment of counting the total number of halftone dots) It is difficult to count the total number of halftone dots in the case of the zigzag arrangement, as compared with the case of the halftone dot arrangement in a square lattice. This is because there are various cases as shown in FIG. 4 depending on how the inspection area is set. If you simply count and multiply the number of rows and columns, you will get too many. Therefore, the following method is adopted. Detection of rows and columns of halftone dots is performed using the above-mentioned binary data. Image memory 6
Scan all addresses in the x direction and sum the binarized data of each address for each scanning line in the x direction, with black being 1 and white being 0, y as shown by F (y) in FIG. A periodic function type histogram with the direction address as an independent variable is obtained. Each mountain in this histogram represents a row of dots. Similarly, all addresses of the image memory 6 are scanned in the y direction to obtain a histogram F (x). This histogram is also CR
It can be displayed at T8.

In the above-mentioned F (y), peaks from top to bottom are 1, 2
Are assigned to obtain the y-coordinate of the center of the odd-numbered peak, for example, the first peak, the binary data in the x-direction along the y-coordinate is read, and the number of halftone dots is counted. To do this, add data to the binarized data with the same data shifted by about 1 bit, go from x = 0, and add 1 to the counter when the data changes from 0 to 1, After that, when the data becomes 0 and becomes 1 again, 1 is added to the counter over the entire range of B, and the number of halftone dots in the odd-numbered row is obtained. Therefore, the number of peaks of odd number is counted in F (y) and multiplied by the number of halftone dots obtained above to obtain the number of halftone dots of all odd rows. Similarly, the same procedure as described above is performed for even-numbered rows, for example, the second row from the top, to obtain the number of halftone dots of all even-numbered rows, and by adding both, the halftone dots in the area A × B Get the total number. To count the halftone dots in one row, the binary data read out along one line were shifted and added together. This is because there is a certain area, and if it is left as it is, the halftone dots may be over-counted, so that the binarized data is averaged to eliminate the white spots and the like. In addition, when the number of halftone dots is counted in only one line, the halftone dots may be missing. Therefore, when the halftone dots are counted in three lines and the halftone dots match in at least two lines, the halftone dot number is calculated. It is better to use a method such as the halftone dot number.

(Second Embodiment of Counting the Total Number of Halftone Points) Another embodiment of counting the total number of halftone dots will be described. First, the above-mentioned binarized data is displayed as an image, and the even-numbered halftone dot sequence (vertical arrangement) is completely erased and the odd-numbered halftone dot data is completely erased.
Create seed image data. This operation is performed, for example, in paragraph [0
010], the x-coordinates of the rising points on both sides of the odd-numbered peak are obtained when the odd-numbered columns are left, and the rising points on the right side of the i-number (odd) -th peak are obtained. It is sufficient to set all the data having the x-coordinate from to the rising point on the left side of the i + 2nd peak to 0. In these image data, each halftone dot has a square lattice array.
Therefore, regarding these two image data, the paragraph [001
0], the histograms F (x), F
Make (y). When the product of the peak numbers of F (x) and F (y) is obtained for each image data, the number of halftone dots in all odd-numbered columns and the number of halftone dots in all even-numbered columns are obtained. Therefore, if the sum of these is obtained, the total number of halftone dots is obtained. .

(Evaluation of halftone dots) To evaluate halftone dots, it is first necessary to determine an inspection area for each halftone dot on the binarized data. In the case of the first embodiment, the above-mentioned histogram F
The coordinates of the center of the valleys of (y) and F (x) are found, and every other halftone dot enters the grid formed by the x and y lines passing through these coordinates. The eye is used as the evaluation area for each halftone dot. However, it is troublesome to set every other evaluation area in this way, so leave the blank grid as the evaluation area as it is and count the number of normal halftone dots as the evaluation, and the total number of halftone dots that should exist. It is easier to obtain the number of defective halftone dots by subtracting from. The halftone dot evaluation method described in the section of (Overall overview) sums up the binarized data of the image with all the pixels within the range where the set halftone dot should exist as the designated points, and this is the predetermined value or more. Whether or not it is a normal halftone dot or a defective halftone dot is determined based on the presence or absence. However, the evaluation method is not limited to this. It is possible to determine even if a smaller number of points are specified in the evaluation area. For example, when halftone dots are represented by binarized image data, normal halftone dots have a circular shape and defective halftone dots have a worm-eaten circular shape, as shown in FIG. Therefore, consider a grid-like line passing through the center of each halftone dot in the image memory, and center each intersection of this halftone dot as 9 points included in normal halftone dots, 25
A point (or 5 points may be specified) is specified, the sum of the binarized data at that point is calculated, and if it is not 9,25 (or 5), it may be a defective halftone dot. Alternatively, even if all the designated points such as 9 points and 25 points are not examined, they are sequentially examined and a white dot (binarization 0) is found, it is judged as a defective halftone dot, and the remaining points are examined. You may stop. The operation of detecting the center lines of the rows and columns of the halftone dots may be performed by setting the centers such as x1 to x2 in the setting operation of the coordinate range in which the halftone dots should exist.

In the case of the second embodiment, F (x) and F (y) for two image data in a square lattice array and respectively
Since the coordinates of the rising points on both sides of each peak of F (x) and F (y) are calculated for each data of each square lattice array using these, a vertical line passing through these coordinates, Since each halftone dot is surrounded by a horizontal line with a rectangular frame, this rectangular frame is used as an evaluation area. In this case, since a blank evaluation area as in the first embodiment is not included, it is sufficient to detect and count defective halftone dots for each of the image data of these two square lattice arrays.

In both the first and second embodiments, the histogram is smoothed when setting the evaluation area of the halftone dot from the histograms F (x), F (y) and the like. The method is arbitrary, but for example, the data obtained by shifting the histogram by one pixel to the left and right is added to the histogram data, and the result is divided by 3. The maximum value and the minimum value are detected by using the averaged histogram in this way, and a value obtained by adding, for example, 20% of the difference to the minimum value is used as a reference level, and the averaged histogram is used for each peak for the reference value. The halftone dot evaluation area is set in the address range that holds data equal to or more than the value. The evaluation range set in this way is a square range that is slightly embedded from the normal halftone dot.

In the present invention, the number of rows and columns of the halftone dot array and the number of halftone dots in one row or column are arbitrary and are not limited to the above-described embodiment. Further, the present invention is Japanese Patent Publication No.
-2104 is an improvement of the invention, various techniques described in the publication are also incorporated in the present invention,
Not described here one by one.

[0017]

According to the present invention, since the quality of the halftone dot printing in which the halftone dots are arranged in a staggered pattern is automatically determined irrespective of human subjectivity, it is highly reliable and efficient. Basic data for quality inspection and improvement studies of printing paper, ink, printing, etc. can be easily obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an example of an apparatus for carrying out the present invention.

FIG. 2 is an enlarged pattern of dot printing.

FIG. 3 is a diagram illustrating the meaning of a coordinate range in which halftone dots should exist.

FIG. 4 shows an example of how halftone dots are arranged in a peripheral portion of a set area in a staggered arrangement.

FIG. 5 is a diagram illustrating the meaning of histograms F (x) and F (y).

FIG. 6 is an enlarged view of a binarized halftone dot.

[Explanation of symbols]

 1 Microscope 2 Imaging Device 3 Monitor CRT 4 Specimen Table 5 CPU 6 Image Memory 7 Keyboard 8 Display CRT 9 Printer

Claims (2)

[Claims] 1. A magnified image of a printing surface is picked up, imaged data in a fixed area is binarized according to a determination level with or without halftone dots, the binarized image data is stored, and the binarized image data is used. The number of halftone dots in one odd-numbered row or column of halftone dots and the number of odd-numbered rows or columns are counted and multiplied by the halftone dot number and the number of rows or columns. Row or column halftone dot number is multiplied by an even numbered row or column number, and the result of these two multiplications is taken as the total halftone dot number in the above-mentioned fixed area, and in the above-mentioned binarized image data halftone dot Specify a plurality of pixel points in the area where should be, and determine the quality of the halftone dot by whether or not a predetermined number of signals with halftone dots are obtained at the above-mentioned pixel points for each halftone dot. A zigzag array halftone dot printing evaluation apparatus, wherein halftone dot printing is evaluated based on a ratio to the total number of halftone dots. 2. An enlarged image of a printing surface is picked up, imaged data in a fixed area is binarized according to a determination level with or without halftone dots, and the binarized image data is stored. The image data of the square lattice halftone dot array remaining after erasing all the halftone dot images of all even-numbered rows or columns is used to obtain the product of the number of rows and columns, and in the same manner, all odd-numbered rows or columns. The product of the number of rows and columns is obtained from the image data of the square lattice-shaped halftone dot array remaining after deleting all the halftone images of the columns, and the sum of the above two products is taken as the total number of halftone dots in a certain area, and A zigzag array halftone dot printing evaluation apparatus, characterized in that the quality of each halftone dot is determined for each of the two square grid halftone dot array image data to obtain the ratio of the number of defective halftone dots to the total number of halftone dots.