JPH09330412A - Picture inspecting method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a picture inspecting method and a device applying the method, by which a picture inspection can be performed by reliably correcting positional deviation a short time with respect to wide inspecting conditions and inspecting object. SOLUTION: As a method for evaluating the coincidence between a line segment of a reference picture and that on an inspecting objective picture, a correlation coefficient, the sum of the absolute values of differences and the sum of the square value of differences are used. An area for evaluating coincidence between a line segment on the reference picture and that on an inspecting objective picture is an area of a prescribed width with a line segment of maximum coincident in a center, which is obtained by last evaluation. In addition, the position of at least a line segment referred to in order to evaluate the coincidence of a line segment in a direction to be processed first is corrected based on the positional deviation quantity of a direction orthogonal to that of last time. In addition, in a method respectively calculating the positional deviation quantity by the combination of plural line segments and making its intermediate value a final positional deviation quantity, a positional deviation quantity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image inspection method and apparatus for correcting a positional shift between a reference image and an image to be inspected, and comparing and inspecting the images.

[0002]

2. Description of the Related Art Defects in printed matter are caused by defects such as wrinkles, foreign substances, and stains on printing paper, ink stains, hickies, doctor streaks, poor density, poor color tone, etc. that occur during printing. is there. Conventionally, the inspection of the printed matter is mainly a visual inspection performed by a human.For example, in the case of the printed matter discharged from the folding unit of the sheet-fed printing press or the rotary printing press, the operator of the printing press pulls it out at a proper time. Then, a visual inspection was performed. If continuous printed matter is ejected from the printing machine and cannot be extracted, the printed matter is irradiated with strobe light that instantaneously emits light in synchronization with the running speed of the printed matter, and the afterimage of the human eye is used to stop the printed matter. Was being visually inspected.

The visual inspection imposes a very heavy work load on the person to be inspected, and since it is performed by a person, it is unavoidable to overlook defects. Therefore, various techniques have been disclosed by making a proposal for automatically inspecting a printed matter. For example, in Japanese Examined Patent Publication No. 1-47823, the image data read from the pattern of the running print at the time when the normal printed matter is printed is stored in the image memory as reference image data, and the reference image data read from the image memory is stored. There is disclosed a technique relating to a printed matter inspection apparatus of a system in which the quality of printing is determined by comparing, in pixel units, with the inspection target image data read from the pattern of the printed matter of the inspection target being printed.

However, when the reference image data and the image data to be inspected are compared on a pixel-by-pixel basis, if the accuracy of defect detection is increased, even if there is a slight misalignment between the two data when reading the pattern from the printed matter, the position The deviation is erroneously detected as a defect. Therefore, in order to prevent the misregistration of the misregistration as a defect, it is necessary to lower the accuracy of the defect detection. If the displacement between the two data cannot be avoided to some extent, the requirement is satisfied. Insufficient inspection performance was obtained. Therefore, Japanese Patent Publication No. 1-20477
In, the inspection target image data or the reference image data is displaced by one pixel in the left-right direction with respect to the traveling direction of the printed matter, and the inspection target image data and the reference image data are compared.
A technique is disclosed in which, after the positional deviation is corrected based on the positional deviation value between the two data when the two data are most matched, the inspection target image data and the reference image data are compared.

[0005]

However, in the conventional method for correcting the positional deviation of the image in the automatic inspection technique, the inspection target image data and the reference image data are compared.
There is a problem that an enormous amount of processing time is required because the image data having an extremely large amount of data is processed. Further, in view of the problem, Japanese Patent Laid-Open No. 7-249122 by the present inventor discloses a method for correcting an image position shift that shortens the processing time. However, this method has a problem in that sufficient correction accuracy cannot be obtained when large positional deviations occur simultaneously in the horizontal direction and in the case where the content of the design of the printed matter mismatches the correction method. Therefore, an object of the present invention is to perform an image inspection by performing a highly reliable positional deviation correction with a short processing time even when there is a special tendency of positional deviation or a special content of a printed matter. An object of the present invention is to provide a possible image inspection method and an apparatus to which the method is applied. The image inspection method and apparatus of the present invention can be applied to a wide range of inspection conditions and inspection objects.

[0006]

To achieve the above object, the present invention provides a method of evaluating the degree of coincidence between a line segment on a reference image and a line segment on an image to be inspected. The sum of values and the sum of squared differences are used. Further, the area for evaluating the degree of coincidence between the line segment on the reference image and the line segment on the inspection target image is an area having a predetermined width centered on the line segment having the highest degree of coincidence obtained by the previous evaluation. Further, at least the position of the line segment referred to in order to evaluate the degree of coincidence of the line segment in the first processing direction is corrected based on the position shift value in the direction orthogonal to the previous direction. Further, in the method of calculating the misregistration value for each combination of a plurality of line segments and using the median value as the final misregistration value, the misalignment value based on the line segment with a low degree of coincidence is excluded. The median value of the displacement values based on the high line segment is set as the final displacement value.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to embodiments. FIG. 1 is a flow chart showing an image inspection process in an image inspection method and apparatus according to the present invention. The process of image inspection will be described with reference to FIG. First, in step S1, line segment position selection is performed to select a line segment position that is a position of a pixel row corresponding to a line segment in a direction parallel to the direction in which the positional deviation is to be corrected. Further, the line segment position selected by the line segment position selecting means may be plural (see FIG. 4). By doing so, in a step described later, a positional deviation value is selectively obtained with respect to each of the line segment positions having a high evaluation value of the degree of coincidence, and the positional deviation of the middle value of the positional deviation values is performed. The inspection target image can be inspected by correcting the positional deviation based on the value and comparing it with the reference image. As a result, the positional deviation correction accuracy can be improved.

Next, in step S2, the first data extraction for extracting the reference pixel data string on the reference image at the line segment position selected by the line segment position selection is performed. Next, in step S3, a plurality of inspection target pixel data strings on the inspection target image are extracted from a plurality of positions including the line segment position and changed in position in pixel units from the line segment position in the direction in which the displacement correction is performed. The second data extraction is performed. The line segment position referred to when the plurality of inspection target pixel data strings are extracted by the second data extracting means is the displacement value of the previous line segment position in the direction orthogonal to the line segment. The line segment position can be corrected based on the above (see FIGS. 2 and 3). There is a case where a large amount of misalignment occurs between the line segment positions selected at the beginning and this time due to the accumulation of misalignments, but by doing so, the accumulation disappears and the width of the misalignment becomes smaller. Therefore, it is possible to improve the accuracy of positional deviation correction in the steps described below. Further, the range of the plurality of inspection target pixel data strings can be set as an inspection target pixel data string of a predetermined range centered on the line segment position corrected based on the positional deviation value of the previous line segment position ( See FIG. 2). By doing so, it is not necessary to perform the calculation for obtaining the evaluation value of the degree of coincidence, which will be described later, for the entire range in which there is a possibility of misalignment, and the processing can be done within a limited range, thus shortening the processing time.

Next, in step S4, an evaluation value for evaluating the degree of coincidence is calculated from the reference pixel data string extracted by the first data extraction and the plurality of inspection object pixel data strings extracted by the second data extraction. The evaluation numerical operation to obtain is performed. The evaluation value of the degree of coincidence may be any one of a correlation coefficient, a sum of absolute differences, and a sum of squared differences. If the evaluation value is a correlation coefficient, the closer the evaluation value is to “1”, the greater the degree of agreement. If the evaluation value is either the sum of the absolute values of the differences or the sum of the squares of the differences, the evaluation value is “ The closer to 0 ", the greater the degree of coincidence.

The above correlation coefficient is calculated by the following equation 1.

[Equation 1] The sum of the absolute values of the differences described above is calculated by the following equation 2.

[Equation 2] Further, the sum of squared differences described above is calculated by the following expression 3.

(Equation 3)

Next, in step S5, from the data of the position of the pixel data string to be inspected and the data of the line segment position, which gives the evaluation numerical value with the highest degree of coincidence among the evaluation numerical values obtained in the evaluation numerical value calculation process. A positional deviation value calculation for obtaining the positional deviation value is performed. Finally, in step S6, a positional deviation correction comparison is performed in which the positional deviation is corrected based on the positional deviation value obtained in the positional deviation value calculation process and compared with the reference image to inspect the inspection target image. In the process of this image inspection, when two-dimensional positional deviation correction is performed, the directions to be corrected are two directions. In the first processing step (S1 to S5), the positional deviation value is obtained for one of the two directions, and then in the second processing step (S1 to S5), the position is determined for the remaining one direction. The displacement value is obtained, and the displacement is corrected in two directions based on each of the displacement values and compared with the reference image to inspect the inspection target image (S6).

FIG. 2 is a diagram showing a line segment position corrected based on the position shift value and a predetermined range in which the degree of coincidence is evaluated to detect the position shift value centered on the line segment position. In FIG. 2, n, n + 1, n + 2, n + 3, n +
4, n + 5 indicate the order of inspection. nth to n
The status at the + 5th test is illustrated by the figures below, in order. The respective figures in the order given below show pixel data strings, and the numbers attached to the left side of each figure show the addresses of pixels (as relative addresses). A black circle indicates a line segment position (center position) selected when the line segment position is selected. The fact that the position of the black circle changes in the order of inspection indicates that the line segment position selected based on the position shift correction value in the direction parallel to the direction of the previous line segment has been corrected. .

In FIG. 2, a predetermined range centering on the position of the black circle is indicated by a dotted line. This range is the range in which the degree of coincidence is evaluated to detect the displacement value. The range in which there is a possibility of displacement is -3 in FIG.
2 to +32 (address of pixel attached to image data string)
The black circle is based on the previous misregistration correction value.
If the selected line segment position is not corrected, the positional deviation is accumulated and the maximum positional deviation becomes the boundary of this range. However, if the selected line segment position indicated by the black circle ● is corrected based on the previous misalignment correction value, there is no significant misalignment in one inspection cycle, so the degree of coincidence is evaluated. The range can be narrowed. In the direction parallel to the image data string shown in FIG.
In the evaluation of the degree of coincidence with respect to a plurality of line segments centering on the position of the black circle, it is possible to reduce the number of line segments to be evaluated in this way, and the processing time of the evaluation numerical value calculation is shortened.

FIG. 3 is a diagram showing a line segment position corrected on the basis of the positional deviation value and an inspection target pixel data string centered on the line segment position. The address of the vertical direction line is corrected by the lateral displacement value in the previous inspection image. By correcting the line address in the vertical direction, the luminance data string on the line is maintained to some extent even if the paper surface meanders, and the positional deviation correction accuracy can be improved. 2 and 3 are mainly applied in the vertical direction (the direction parallel to the web transfer direction), but are not particularly limited. The positional deviation in the vertical direction is caused by the variation of the web path length between the plate cylinder final unit and the camera position, and the positional deviation value is relatively large, so the method of FIG. 2 is effective.
In addition, since the top-bottom direction position shift correction with a large position shift value is performed before the left-right correction, when the image has a left-right position shift, the top-bottom direction position shift correction becomes unstable.
Therefore, the method of FIG. 3 is effective. When performing the lateral displacement correction, since the positional displacement value in the vertical direction is known in advance, the address of the lateral line segment of the inspection target image is corrected accordingly. Therefore, the method of FIG. 3 is not necessary. The methods of FIGS. 2 and 3 do not have to be selectively applied and can be applied simultaneously.

Next, a case will be described in which the positional deviation is corrected at a plurality of sets of line segment positions. When performing the positional deviation correction in one direction, a plurality of sets of line segment positions are selected, the positional deviation correction value is calculated for each, and the positional deviation correction is performed based on the median value. However, in that case, an inappropriate misregistration correction value obtained by the calculation is reflected in the middle value despite the evaluation value having a low degree of coincidence, and the misregistration correction accuracy is reduced accordingly. It will be. In the present invention, since any one of the correlation coefficient (normalized cross-correlation coefficient), the sum of the absolute values of the differences, and the sum of the squares of the differences is used as the evaluation value of the coincidence, the absolute evaluation of the coincidence is performed. You can get the numerical value. Therefore, the median value of the positional deviation correction value calculated based on the predetermined number of line segment positions that give the evaluation numerical value with a high degree of coincidence is set as the positional deviation correction value used for the actual positional deviation correction.

FIG. 4 is a table showing the evaluation values of the degree of coincidence and the positional deviation correction values for a plurality of sets of line segment positions.
In FIG. 4, the line No. 1 to 5 are numbers given to each of the five line segment positions. Further, the correction value (positional deviation correction value) and the normalized correlation value (correlation coefficient) are evaluation numerical values of the positional deviation correction value and the degree of coincidence calculated at each line segment position.
In the example shown in FIG. 2 and No. The line of 5 is an evaluation value with a low degree of coincidence and is determined to be unsuitable. If three of the highest correlation coefficients are adopted, the line segment position selected is No. 1, No. 3, No. Since the median value of the positional deviation correction value is -1, it becomes the positional deviation correction value used for the actual positional deviation correction. Note that, instead of the median value of the misregistration correction value, a similar miscellaneous effect can be obtained by using a misregistration correction value that gives an evaluation numerical value with the highest degree of coincidence as an actual misalignment correction value.

In the above description, a line segment on the reference image is sequentially compared with a plurality of line segments in a predetermined range of the image to be inspected, and the degree of coincidence is evaluated over the entire predetermined range. However, even if the relationship between the reference image and the image to be inspected is exchanged, there is no change in the meaning of positional deviation correction. Therefore, even if the terms “reference” and “inspection target” are replaced with each other including the claims, the same effect can be obtained. For convenience of description, the description has been limited to the above, but in the present invention, the relationship between the reference image and the inspection target image can be interchanged, and any case is included in the present invention. However, in a strict sense, they are not the same. The reason is that the pixel data on the line segment on the reference image is guaranteed to have a change (select such an intersection), but the pixel data on the line segment on the inspection target image does not change. However, the existence of the change is not guaranteed due to the displacement. Therefore, at that point, it is better to specify the line segment position in the first data extraction on the reference image.

[0018]

EXAMPLE FIG. 5 is a schematic diagram showing an outline of the apparatus configuration of the present invention. In FIG. 5, 1 is a printing unit, 2 is a printed matter, 3 is a guide roller, 4 is a light source for illumination, 5 is a camera unit for imaging, 6 is a camera control unit for controlling the camera unit, and 7 is a machine of the printing unit. A rotary encoder for detecting a target position (rotational position of the plate cylinder), and 8 is a main body of a printed matter inspection apparatus for processing image data obtained by imaging by a camera unit. The printing paper passes through the printing unit 1, where printing is performed and becomes printed matter 1,
It is guided by the guide roller 3 and reaches a position illuminated by the light source 4. The guide roller 3 is usually in that position.
Therefore, the position of the printed matter 2 is defined. The printed matter 2 is imaged by the camera unit 5 at that position. The camera unit 5 is a linear sensor camera that captures an image by one-dimensional scanning in the example of FIG.

A rotary encoder 7 is installed in the plate cylinder of the printing unit 1 or in a portion which rotates in synchronization with the plate cylinder, and outputs a pulse signal in synchronization with a printing cycle.
This pulse signal is input to the camera control unit 6, and the camera control unit 6 outputs an imaging start signal to the camera unit 5 every time the printed matter 2 travels a predetermined amount in synchronization with the printing cycle, and the camera unit 5 captures an image. Data, that is, analog data is input, A / D (analog to digital) conversion is performed to convert it into digital data, and the data is transferred to the printed matter inspection apparatus main body 8. In this way, two-dimensional scanning is performed at a timing synchronized with the printing cycle, and digital image data is read into the printed matter inspection apparatus main body 8. Further, since the image is captured in synchronization with the printing cycle in this manner, If there is no disturbance factor or error factor, the imaging data read in each printing cycle will always be the imaging data at the same print pattern position if the imaging data is at the same cycle timing.

The printed matter inspection apparatus main body 8 to which the digital image signal is input stores the digital image data of the printed matter 1 when a non-defective product is printed in the memory as a reference image. Then, it is determined whether or not a defect of the printed material 1 has occurred by using the digital image data input thereafter as the inspection target image data.

FIG. 6 is a block diagram showing the structure of the main body of the printed matter inspection apparatus. In FIG. 6, 8 is a printed matter inspection apparatus main body, 5 is a camera unit, 6 is a camera control unit, 9 is a reference image data memory, 10 is an inspection target image data memory, 11 is a reference input command input unit, and 12 is a misregistration detection. Reference numeral 13 is a positional deviation correction comparison unit, and 14 is a parameter input unit. Each of the reference image data memory 9 and the inspection target image data memory 10 has a storage capacity capable of storing at least one unit of printed matter (a printing screen for one cycle performed by the printing unit). Further, the reference input command input unit 11 is a command for taking a reference image to start the image inspection and inputting data to the reference image data memory 9, and then taking an inspection target image to be stored in the inspection target image data memory 10. Switch the command to input.

When the reference input command input unit 11 commands the input of the reference image data, the selector of FIG. 4 connects the image data to the reference image data memory 9, and at this time, the misregistration detection unit 12, And misregistration correction comparison unit 13
Does not work. On the other hand, when the input of the inspection target image data is commanded by the reference input command input unit 11, the selector makes an input connection of the imaging data to the inspection target image data memory 10. Then, the positional deviation detecting unit 12 detects the positional deviation between the inspection target image and the reference image, and sends the resulting positional deviation correction value to the positional deviation correction comparing unit 13. Then, the misregistration correction comparison unit 13 that has received the misregistration correction value performs a collation comparison inspection of the inspection target image data and the reference image data in consideration of the misregistration correction value. In addition, the parameter input unit 1
Reference numeral 4 is an input for setting parameters used in the positional deviation detecting unit 12 and the positional deviation correction comparing unit 13. As a parameter, for example, a threshold value for performing a pass / fail judgment by comparing the inspection target image data with the reference image data in the positional deviation correction comparing unit 13 is input.

FIG. 7 is a block section showing the structure of the positional deviation detecting section. In FIG. 5, reference numeral 12 denotes a positional deviation detection unit,
Reference numeral 9 is a reference image data memory, 10 is an inspection target image data memory, 11 is a reference input command input unit, 13 is a positional deviation correction comparing unit, 15 is a line segment position selecting unit, 16 is a first data extracting unit, and 17 is a first data extracting unit. 2 is a data extraction unit, 18 is a first pixel data string memory, 19 is a second pixel data string memory, 20 is an evaluation numerical value calculation unit, and 21 is a middle value calculation unit. Further, FIG. 8 is a flowchart showing a flow of data processing in the positional deviation detecting unit 12.

In FIGS. 7 and 8, the line segment position selection unit 15 first selects five line segment positions in the vertical direction by referring to the reference image data in the reference image data memory 9 (S1). First
The data extraction unit 16 of (1) inputs the line segment position and extracts the reference pixel data string of each line segment position in the vertical direction from the reference image data memory 9 (S2). In addition, the second data extraction unit 1
7 inputs the line segment position and extracts a plurality of inspection target pixel data strings at each line segment position in the vertical direction from the inspection target image data memory 10 (S3).

One of the reference pixel data strings extracted by the first data extracting section 16 is stored in the first image data string memory 18. Further, one of the inspection target pixel data strings extracted by the second data extracting unit 17 is stored in the second image data string memory 19. Evaluation numerical value calculation unit 20
Calculates the evaluation numerical values of the reference pixel data string and the inspection pixel data string stored in the first image data string memory 18 and the second image data string memory 19. Such calculation of evaluation numerical values is repeated a plurality of times for a plurality of inspection target pixel data strings corresponding to each reference pixel data string to obtain a plurality of evaluation numerical values (S4).

The median value calculator 21 includes an evaluation value calculator 20.
Among the plurality of evaluation numerical values calculated in step S1, the inspection target pixel data string that gives the evaluation numerical value with the highest degree of coincidence for each line segment position is obtained and stored together with the evaluation numerical value (S5). Further, the median value calculation unit 21 obtains a positional deviation value based on each line segment position exceeding a predetermined value from the evaluation numerical values for each line segment position obtained by the evaluation numerical value calculation unit 20, and further calculates the positional deviation value. Obtain the unit value and use it as the displacement value in the vertical direction.
The position shift value in the vertical direction is output to the position shift correction comparison unit 13 (S6). The steps of obtaining the positional deviation value in the vertical direction described in S1 to S6 can be performed in the same manner in the horizontal direction. Therefore, steps S7 to S1 for obtaining the displacement value in the left-right direction
The description of 2 is omitted. However, when performing the horizontal correction as described above, the positional deviation value in the vertical direction is known in advance, so that the line segment address in the horizontal direction is corrected in step S8.

As described above, in this example, the positional deviation in the horizontal direction is corrected after the positional deviation in the vertical direction is corrected.
When inspecting printed matter, the behavioral state of the printed matter due to running is more than the positional displacement in the left-right direction due to meandering. The displacement of is usually larger. Therefore, as in this example, it is possible to perform the positional deviation correction with higher reliability by performing the positional deviation correction in the vertical direction first.

In this example, the number of line segment positions is 5 in both the vertical direction and the horizontal direction. Since the median value of these five misregistration correction values is used as the final misregistration correction value, a correct correction value can be obtained even if an error occurs in up to two of the five results. In this way, by using a plurality of line segment positions, it is possible to improve the reliability of positional deviation correction. The selection of such a line segment position by the line segment position selection unit 15 is performed in the vertical direction line segment in which there is little data change when the position shifts in the left and right directions from the reference image data, and in the left and right direction where the data change is little when the position shifts in the up and down direction. Select a line segment. As a method for selecting this line segment, the method described in Japanese Patent Application Laid-Open No. 7-249122 filed by the present inventor can be applied.

FIG. 9 is a block diagram showing the configuration of the positional deviation correction comparison unit. In FIG. 9, 13 is a positional deviation correction comparison section, 6 is a camera control section, 9 is a reference image data memory, 10 is an inspection target image data memory, 12 is a positional deviation detection section, 22 is an expansion processing circuit, and 23 is degeneration processing. Circuit, 2
4 is an upper threshold setting circuit, 25 is a lower threshold setting circuit, 26
Is an upper threshold image buffer, 27 is a lower threshold image buffer, 28 is an image shift circuit, 29 is an upper threshold comparison circuit,
Reference numeral 30 is a lower threshold comparison circuit. In the above configuration,
The image shifting circuit 28 includes the inspection target image data memory 10
The image is shifted according to the positional deviation correction value obtained by the positional deviation detection unit.

The degeneracy processing circuit 23 performs a process of narrowing an area corresponding to a bright area of the image data written in the reference image data memory 9. vice versa,
The expansion processing circuit 22 performs processing for thickening a bright area. As an example of the actual processing, the degeneration processing circuit 23 is expressed by the following expression 4 and the expansion processing circuit 22 and the following expression 5 are shown.

## EQU00004 ## f (x, y) = min {f (x-1, y-
1), f (x, y-1), f (x + 1, y-1), f
(X-1, y), f (x, y), f (x + 1, y), f
(X-1, y + 1), f (x, y + 1), f (x + 1,
y + 1)} However, the function min {} indicates that the minimum value of the listed variables is taken.

## EQU00005 ## f (x, y) = max {f (x-1, y-
1), f (x, y-1), f (x + 1, y-1), f
(X-1, y), f (x, y), f (x + 1, y), f
(X-1, y + 1), f (x, y + 1), f (x + 1,
y + 1)} However, the function max {} indicates that the maximum value among the listed variables is taken.

Expression 4 represents that the darkest brightness value is newly set as the brightness of the target pixel from the brightness of the target pixel and the pixels in the vicinity of the target pixel. Expression 5 represents that the brightest luminance value is newly set as the luminance of the target pixel from among the luminances of the target pixel and pixels in the vicinity of the target pixel. The lower limit threshold setting circuit 25 has a lower limit value of the brightness variation set in advance by the parameter input unit 14, and the lower limit value is subtracted from the output of the degeneration processing circuit 23.
7 is written. Similarly, the upper limit threshold setting circuit 24
The upper limit value of the brightness variation is set in advance by the parameter input unit 14, and the upper limit value is added to the output of the expansion processing circuit 22 and written in the upper threshold image buffer 26.

In the lower threshold comparison circuit 30, the luminance value of the lower threshold image buffer 27 and the inspection target image data memory 10 are compared.
Are compared for each corresponding pixel, and when the brightness value of the inspection target image data memory 10 is lower than the brightness value of the lower limit threshold image buffer 27, it is determined that a defect has occurred. Further, the upper threshold comparison circuit 29 compares the luminance value of the upper threshold image buffer 26 and the luminance value of the inspection target image data memory 10 for each corresponding pixel, and the luminance value of the inspection target image data memory indicates the upper threshold image buffer. If the brightness value is higher than 26, it is determined that a defect has occurred.

Since the positional deviation correction processing of the present invention is correction for each pixel, the positional deviation of less than one pixel cannot be corrected even if the correction processing is performed. Therefore, in the misregistration correction comparison unit 13, the degeneration processing circuit 23 and the expansion processing circuit 22.
With this feature, erroneous detection was allowed in the edge part where the brightness change in the image is drastic. The configuration of the misregistration correction comparing unit 13 of the present invention is not limited to this embodiment, and the brightness of each pixel of the reference image memory and the brightness of each pixel of the image to be inspected can be simply calculated according to the misregistration value. It may be compared to.

[0034]

As described above, according to the present invention, even when there is a special tendency of misregistration or a special content of the pattern of the printed matter, the misregistration correction with a short processing time and high reliability is performed. Provided are an image inspection method and an apparatus to which the method is applied, which can inspect an image. Also,
According to the present invention, the line segment position selected when the line segment position is selected is the line segment position that is corrected based on the displacement value of the previous line segment position in the direction orthogonal to the line segment. Since the displacement value of the inspection image is not so large as compared with the previous inspection image, it is not necessary to evaluate the entire displacement calculation range, and the processing time is shortened. Also, by correcting the address of the vertical line based on the horizontal displacement value in the previous inspection image, the brightness data string on the line is maintained to some extent even if the web (printing paper) meanders, and the displacement correction is performed. The accuracy can be improved. Further, according to the present invention having a plurality of line segment positions selected by the line segment position selection means, selectively obtain a positional deviation value for those having a high evaluation numerical value of the degree of coincidence with respect to these line segment positions, The image to be inspected can be inspected by correcting the positional deviation based on the median value of the positional deviation values and comparing it with the reference image. As a result, the positional deviation correction accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a flow chart showing an image inspection process in an image inspection method and apparatus according to the present invention.

FIG. 2 is a line segment position corrected based on a displacement value,
It is a figure which shows the predetermined range which evaluates a coincidence degree in order to detect the position shift value centering on the line segment position.

FIG. 3 is a line segment position corrected based on a displacement value,
It is a figure which shows the inspection object pixel data string centering on the line segment position.

FIG. 4 is a diagram showing a table of evaluation values of coincidence and misalignment correction values for a plurality of sets of line segment positions. It is a block diagram showing the composition of the printed matter inspection device body.

FIG. 5 is a schematic diagram showing an outline of a device configuration of the present invention.

FIG. 6 is a block diagram showing a configuration of a printed matter inspection apparatus main body.

FIG. 7 is a block unit showing a configuration of a position shift detection unit.

FIG. 8 is a flowchart showing a flow of data processing in the positional deviation detection unit 12.

FIG. 9 is a block diagram showing a configuration of a positional deviation correction comparison unit.

[Explanation of symbols]

 1 printing unit 2 printed matter 3 guide roller 4 light source 5 camera unit 6 camera control unit 7 rotary encoder 8 printed matter inspection apparatus main body 9 reference image data memory 10 inspection target image data memory 11 reference input command input unit 12 position shift detection unit 13 position shift Correction comparison unit 14 Parameter input unit 15 Line segment position selection unit 16 First data extraction unit 17 Second data extraction unit 18 First image data string memory 19 Second image data string memory 20 Evaluation numerical value calculation unit 21 Medium value calculation unit 22 Expansion Processing Circuit 23 Degeneration Processing Circuit 24 Upper Threshold Setting Circuit 25 Lower Threshold Setting Circuit 26 Upper Threshold Image Buffer 27 Lower Threshold Image Buffer 28 Image Shifting Circuit 29 Upper Threshold Comparison Circuit 30 Lower Threshold Comparison Circuit

Claims (8)

[Claims] 1. An image inspecting method for inspecting an image to be inspected by comparing with a reference image, wherein a line segment position which is a position of a pixel row corresponding to a line segment in a direction parallel to a direction in which positional deviation is to be corrected is selected. A line segment position selection process, a first data extraction process of extracting a reference pixel data string on the reference image at the line segment position selected in the line segment position selection process, the line segment position, and pixels from the line segment position A second data extracting step of extracting a plurality of inspection object pixel data strings on an inspection object image from a plurality of positions whose positions are changed in units of line segments, and a reference pixel data string extracted in the first data extracting step And an evaluation numerical value calculation process for obtaining an evaluation numerical value for evaluating the degree of coincidence from the plurality of inspection target pixel data strings extracted in the second data extraction process, and the evaluation numerical value calculation process obtained in the evaluation numerical value calculation process. Maximum degree A position shift value calculation process for obtaining a position shift value from the position data of the inspection target pixel data string giving the evaluation value and the line segment position data, and the position shift based on the position shift value obtained in the position shift value calculation process. And an image inspection method for inspecting an image to be inspected by comparing with the reference image. 2. An image inspection method for inspecting an image to be inspected by comparing with a reference image, wherein a line segment position, which is a position of a pixel row corresponding to a line segment in a direction parallel to a direction in which positional deviation is to be corrected, is selected. Line segment position selecting means, first data extracting means for extracting a reference pixel data string on the reference image at the line segment position selected by the line segment position selecting means, the line segment position and pixels from the line segment position Second data extracting means for extracting a plurality of inspection object pixel data strings on the inspection object image from a plurality of positions whose positions have been changed in the direction of the line segment, and reference pixel data strings extracted by the first data extracting means And an evaluation numerical value calculating means for obtaining an evaluation numerical value for evaluating the degree of coincidence from the plurality of inspection object pixel data strings extracted by the second data extracting means, and the evaluation numerical value matching means obtained by the evaluation numerical value calculating means. Maximum degree A positional deviation value calculating means for obtaining a positional deviation value from the data of the position of the inspection target pixel data string giving the evaluation numerical value and the data of the line segment position, and the positional deviation based on the positional deviation value obtained by the positional deviation value calculating means. An image inspection apparatus, comprising: a positional deviation correction comparing unit that corrects the image and compares the image with the reference image to inspect the inspection target image. 3. The directions to be corrected are two directions, and the positional deviation value is obtained for one of the two directions,
7. The inspecting target image is inspected by obtaining the misalignment value for the remaining one direction, correcting the misalignment in two directions based on each of the misalignment values, and comparing with the reference image. 2. The image inspection device according to 2. 4. The image inspection apparatus according to claim 2, wherein the evaluation numerical value is a correlation coefficient. 5. The image inspection apparatus according to claim 2, wherein the evaluation numerical value is a sum of absolute values of differences. 6. The image inspection apparatus according to claim 2, wherein the evaluation value is a sum of squared differences. 7. A line segment position referred to when a plurality of inspection object image data strings are extracted by the second data extracting means is a displacement value of a previous line segment position in a direction orthogonal to the line segment. 7. The image inspection apparatus according to claim 2, wherein the line segment position is corrected based on the above. 8. A plurality of line segment positions selected by the line segment position selecting means are provided, and a position shift value is selectively selected with respect to each of the line segment positions having a high evaluation value of the degree of coincidence. 8. The image according to claim 2, wherein the image to be inspected is obtained by correcting the positional deviation based on the positional deviation value of the median of the positional deviation values and comparing it with the reference image. Inspection device.