JP2004045228A - Method and apparatus for inspecting stain in print - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a practical method and a practical apparatus for inspecting stain in prints that prevent erroneous determination due to misalignment and variable information and reducing inspection omission in an important region by increasing a region to be inspected. <P>SOLUTION: The method for inspecting stain in prints and the apparatus to which the method is applied comprise an inspection region setting process for setting a specific region to be inspected in the imaged picture of the prints; a binarization process for binarizing a picture in the region to be inspected to generate a binary picture; a number calculation process for calculating the number of patterns that cross the region to be inspected in the binary picture; and a stain decision means for deciding the presence or absence of the stain in the prints in the region to be inspected based on the number. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention belongs to the technical field of inspecting printed matter. In particular, the present invention relates to a print smear inspection method and apparatus for inspecting a printed matter including variable information printed by a printer.
[0002]
[Prior art]
As a method of inspecting a printed matter for stains, a method of comparing a printed image with a reference image is known. In this method, a reference image obtained by imaging a proper printed matter is stored in a memory, and an absolute value of a difference between the reference image obtained by imaging the printed matter to be inspected and the difference image is calculated. The presence / absence of contamination is determined based on the number of pixels generated and having a large pixel value in the difference image.
[0003]
In addition, a method of inspecting only a margin is known. In this method, an inspection area included in a blank portion is set in a captured image of a printed matter, and the presence or absence of contamination is determined based on the number of pixels having a pixel value exceeding a predetermined threshold value in the inspection area in the inspection target image. Done.
[0004]
[Problems to be solved by the invention]
In the method of comparison with the reference image, erroneous determination that a non-defective product is a defective product is likely to occur due to a positional shift of a picture due to meandering of a sheet or the like. In order to avoid this, it is necessary to lower the dirt detection performance or to perform a position shift correction process. However, even if it is performed, the direct mail contains variable information to be printed by the printer, and different printing is performed for each page. In such printed matter, variable information and stain cannot be distinguished in principle, and this method cannot be applied as it is.
[0005]
Also, in the method of inspecting only the margin, the practicality is low because the area that can be inspected is large because the area leaking from the inspection is wide. That is, the margins are small on the paper surface of a general printed matter, and the vicinity of the top, bottom, left and right sides of a page where a relatively large margin is seen is a prohibited area of printing by a printer, and the occurrence of dirt does not become a quality problem. Often.
[0006]
The present invention has been made in order to solve such a problem, and has as its object that there is no misjudgment due to misregistration or variable information, and that the area that can be inspected can be widened so that inspection omissions in areas of high importance are reduced. An object of the present invention is to provide a printing stain inspection method and apparatus with high practicality.
[0007]
[Means for Solving the Problems]
The above object is achieved by the present invention described below. That is,
According to a first aspect of the present invention, there is provided a print smear inspection method, wherein an inspection area setting step of setting a predetermined inspection area in a captured image of a printed material, and binarizing the image of the inspection area by a predetermined threshold value. Binarizing step of generating a digitized image, a number calculating step of calculating the number of patterns traversing the inspection area in the binarized image, and determining the presence or absence of print smear in the inspection area based on the number And a dirt determination step.
[0008]
According to the present invention, a predetermined inspection region is set in a captured image of a printed material in an inspection region setting process, and an image of the inspection region is binarized by a predetermined threshold value in a binarization process to obtain a binarized image. Is generated, the number of patterns traversing the inspection area in the binarized image is calculated in the number calculation step, and the presence or absence of print stains in the inspection area is determined based on the number in the stain determination step. In a proper printed matter, the inspection area can be set appropriately so that the number of patterns crossing the inspection area is not affected by the positional deviation or the variable information. The setting of the inspection area is not limited to the margin. When such setting is performed, the number of patterns changes when dirt crosses the inspection area. Accordingly, there is no misjudgment due to misalignment or variable information, and the area that can be inspected can be widened, so that a highly practical print smear inspection method with less omission of inspection in a highly important area can be provided.
[0009]
According to a second aspect of the present invention, in the method for inspecting print smudges according to the first aspect, the predetermined inspection area is an area where there is no transverse pattern in a proper printed matter. Things. According to the present invention, the presence / absence of a print stain is immediately determined based on the presence / absence of a traversing pattern, so that the algorithm can be simplified and the inspection speed can be increased.
[0010]
According to a third aspect of the present invention, there is provided the printing smear inspection method according to the first or second aspect, wherein the predetermined inspection area includes two horizontal sides perpendicular to a printing direction and a printing direction. Is a rectangular area consisting of two vertical sides parallel to. ADVANTAGE OF THE INVENTION According to this invention, setting of an inspection area is easy, an algorithm is simplified and an inspection speed can be improved.
[0011]
According to a fourth aspect of the present invention, in the method for inspecting print smear according to the third aspect, the number is the number of patterns crossing from one of the two horizontal sides to the other. It is. According to the present invention, generally, the frequency of occurrence of print stains flowing in the printing direction is high, so that the algorithm can be simplified and the inspection speed can be increased without substantially lowering the inspection performance.
[0012]
According to a fifth aspect of the present invention, there is provided the printing stain inspection method according to any one of the first to fourth aspects, wherein the captured image is an image captured through a complementary color filter of an ink color. It was done. ADVANTAGE OF THE INVENTION According to this invention, the contrast of printing dirt in a picked-up image improves and inspection performance can be improved.
[0013]
According to a sixth aspect of the present invention, there is provided a print smear inspection method according to any one of the first to fifth aspects, wherein the smudge determination step includes determining the number in the inspection reference print and the number in the inspection target print. Is determined to be a process in which it is determined that there is no print stain when the values match, and that there is print stain in other cases. According to the present invention, a strict determination is made that a printed matter is proper only when the number of patterns crossing the inspection area matches.
[0014]
According to a seventh aspect of the present invention, in the print smear inspection method according to any one of the first to sixth aspects, a plurality of the inspection areas are set in a captured image of the printed matter. The above-described series of processes is performed for each of the regions. ADVANTAGE OF THE INVENTION According to this invention, the area | region which can be inspected can be made large and the omission of the inspection of a highly important area | region is small, and since each inspection area | region can be narrowed, a small print stain is also detected.
[0015]
According to another aspect of the present invention, there is provided a print smear inspection apparatus, comprising: an inspection area setting unit configured to set a predetermined inspection area in a captured image of a printed material; Binarizing means for generating a binarized image, number calculating means for calculating the number of patterns crossing the inspection area in the binarized image, and judging the presence or absence of print stains in the inspection area based on the number And a dirt determination unit that performs the determination.
[0016]
According to the present invention, a predetermined inspection area is set in the captured image of the printed matter by the inspection area setting means, and the image of the inspection area is binarized by the predetermined threshold value by the binarization means, thereby obtaining a binarized image. Is generated by the number calculation means, the number of patterns crossing the inspection area in the binarized image is calculated, and the presence / absence of printing stains in the inspection area is determined based on the number by the stain determination means. In a proper printed matter, the inspection area can be set appropriately so that the number of patterns crossing the inspection area is not affected by the positional deviation or the variable information. The setting of the inspection area is not limited to the margin. When such setting is performed, the number of patterns changes when dirt crosses the inspection area. Therefore, there is no misjudgment due to misregistration or variable information, and the area that can be inspected can be widened, so that there is provided a highly practical printing stain inspection apparatus with less inspection omissions in areas of high importance.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described. FIG. 1 shows an example of the configuration of the print smear inspection apparatus of the present invention. In FIG. 1, 1 is a camera, 2 is a photoelectric sensor, 3 is a data processing unit, 4 is an alarm, 5 is a keyboard, 6 is a mouse, 7 is a display, 11 is a printer, and 100 is a printed matter.
The printer 11 prints variable information on a printed material that has already been printed with fixed information but has not printed variable information, and obtains a printed matter 100 in which both fixed information and variable information have been printed. Printer. As the printer, for example, an ink jet printer, a laser printer, or the like is used. The printer 11 prints variable information by inputting print data, generating a print data image corresponding to an image to be actually printed from the print data, and printing the print data image in a variable print area of the printed matter 100. Process.
[0018]
The printed material 100 is discharged and transferred when the variable information is printed by the printer 11. Immediately after the printed matter 100 is discharged from the printer 11, an image is taken by the camera 1 of the print smear inspection apparatus.
[0019]
The camera 1 is an imaging unit that captures the entire printed matter 100 to obtain an entire captured image, or at least captures a set inspection region to obtain an inspection region image. When setting the inspection area in the printed matter 100, the entire captured image is used. Further, when performing the print smear inspection, it is generally configured to cut out the set inspection region from the entire captured image and perform data processing. Of course, it is also possible to configure so that only the set inspection area is imaged.
[0020]
As the camera 1, an area sensor camera or a line sensor camera having an image sensor of a charge coupled device (CCD) type or a metal oxide semiconductor (MOS) type, an imaging optical system (lens), a driving / amplifying circuit, and the like is used. can do. When the line sensor camera is used, a two-dimensional image is captured by the main scanning and the sub-scanning by transferring the printed matter 100. When a line sensor camera is used, high resolution is easily obtained.
The image forming optical system of the camera 1 is provided with a complementary color filter for the ink color of the printed matter 100, and an image is taken through the complementary color filter. With this configuration, the contrast of the print stain can be improved, and the inspection performance can be improved.
[0021]
The photoelectric sensor 2 is a sensor for detecting a characteristic portion (a contour, a mark, or the like of a picture) of the transferred printed matter 100. The detection signal of the photoelectric sensor 2 gives an image pickup timing by the camera 1.
[0022]
The data processing unit 3 performs operations such as controlling the operation of the print smear inspection apparatus, extracting print smudges, and determining whether the printed matter 100 is good or bad (details will be described later). The data processing unit 3 can be realized by hardware and software of a data processing device such as a personal computer and an image processing device.
[0023]
The alarm 4 is an alarm for issuing an alarm sound to notify the operator when the data processing unit 3 determines that the printed matter 100 is defective. The operator can understand the situation and take necessary measures by listening to the alarm sound.
The keyboard 5 and the mouse 6 are parts for the operator to input settings for the data processing unit 3 and the like.
The display 7 performs display of an input screen for performing the input, display of a captured image, display of print stain detection, and the like.
[0024]
With the above configuration, the operation of the print smear inspection apparatus of the present invention will be described with reference to FIGS. The operation of the printing smudge inspection apparatus according to the present invention can be roughly divided into a setting process and an inspection process. FIG. 2 is a flowchart showing a setting process in the print smear inspection apparatus of the present invention. FIG. 3 is a flowchart showing an inspection process in the print smear inspection apparatus of the present invention. 4 to 6 are schematic diagrams showing an inspection area set in the print smudge inspection apparatus of the present invention, or a relationship between the inspection area and the stain.
[0025]
First, the setting process will be described. In step S1 (imaging) of FIG. 2, the camera 1 images one unit (one round of the plate cylinder, one page) of the printed matter 100. The data processing unit 3 outputs a command for capturing an image of the printed matter 100 to the camera 1 when the photoelectric sensor 2 detects and outputs a characteristic portion of the printed matter. The printed matter 100 to be imaged in this setting process is an appropriate printed matter free from defects such as print stains. Then, the data processing unit 3 inputs an image pickup signal output from the camera 1, converts the signal into analog-to-digital (A / D), and stores the image in a memory.
[0026]
Next, in step S2 (inspection area setting), the data processing unit 3 displays a captured image on the display 7. The operator sets a test area by operating a mouse or the like while watching the display 7. A plurality of inspection areas can be set. FIG. 4 shows an image of one unit in the printed matter 100 displayed on the display and an example of the inspection area (inspection area a) set in the image. In the example shown in FIG. 4, one of the inspection areas is set as a rectangular area.
[0027]
FIG. 5 shows an example of an image for one unit in the printed matter 100 displayed on the display and an inspection area set in the image. In the example shown in FIG. 5, a plurality of inspection areas (inspection areas a to g) are set as rectangular areas. In addition, in the example shown in FIGS. 4 and 5, this inspection area is set as an area where there is no crossing pattern in a proper printed matter.
[0028]
The entire inspection process will be described later. However, if there is no traversing pattern, if even one traversing pattern occurs in the inspection area, it can be determined that the pattern is caused by dirt. Further, when there is a traversing pattern, if the number of traversing patterns existing in the inspection area changes, it can be determined that the number is caused by dirt.
[0029]
In order to obtain uniform inspection accuracy, the inspection area is generally rectangular. This inspection area may include the entire pattern or a part of the pattern. However, when the imaging is repeated, a displacement occurs between the imaging region and the inspection region. When the position shift correction is not performed, it is necessary to select an area in the captured image where the number of traversing patterns does not change with respect to the position shift that normally occurs, and set the inspection area.
[0030]
As the size of the inspection area, the entire printed matter for one unit can be set as one inspection area. However, actually, the load of data processing in the image processing apparatus increases. In addition, detection cannot be performed unless the pattern is a long pattern that traverses the entire printed matter for one unit. Therefore, this is not an effective method of setting the inspection area. Conversely, even when a large number of narrow strip-shaped inspection areas are arranged, even point-like stains that do not cause a defect in quality are detected, which is not practical. In conclusion, in general, print stains are often linear in the direction of paper transport. Therefore, an area with a width about the lower limit of print stains to be detected is set in areas other than large pictures and ruled lines. Is preferred.
[0031]
Next, in step S3 (binarization), the image of the inspection area in the captured image is binarized with a predetermined threshold. For the threshold value, for example, a frequency distribution of pixel values is obtained in an image of an inspection area, and two peaks of a distribution of large (bright) pixel values and a peak of small (dark) pixel values can be clearly distinguished. It is determined as a pixel value that becomes a valley of such a distribution.
[0032]
Next, in step S4 (crossing pattern extraction), a crossing pattern existing in the set inspection area is extracted. The crossing pattern is a pattern that traverses the inspection area. When the inspection area is a rectangle as shown in FIGS. 4 and 5, two sides in the vertical direction (in the example shown in FIGS. Side) from one side and into the other.
[0033]
An example of the extraction of the crossing pattern will be described. First, pixels that are adjacent to each other are assigned the same number, and pixels that are not adjacent to each other are assigned different numbers. When this is performed for all the pixels in the inspection area, the number is a number that specifies an independently existing pixel group (including one pixel group). Then, it is determined whether or not each pixel group includes pixels on two sides in the vertical direction. When both pixels on both sides are included, the pixel group is a crossing pattern, otherwise it is not a crossing pattern.
[0034]
Next, in step S5 (number registration), the number of crossing patterns extracted for the inspection area is registered in association with the inspection area. In FIG. 4, there is one inspection area, but when there are a plurality of inspection areas as shown in FIG. 5, the number of crossing patterns in the inspection area is registered in association with each inspection area.
[0035]
The setting process has been described above. Next, an inspection process in the operation of the print smear inspection apparatus of the present invention will be described with reference to FIG. First, in step S101 (imaging) of FIG. 3, the camera 1 images one unit (one round of the plate cylinder, one page) of the printed matter 100. The data processing unit 3 outputs a command for capturing an image of the printed matter 100 to the camera 1 when the photoelectric sensor 2 detects and outputs a characteristic portion of the printed matter. The printed material 100 imaged in this setting process is a printed material to be inspected. Then, the data processing unit 3 inputs an image pickup signal output from the camera 1, converts the signal into analog-to-digital (A / D), and stores the image in a memory.
[0036]
Next, in step S102 (examination of an inspection area), the data processing unit 3 extracts an area of a captured image corresponding to the set inspection area (see FIG. 4). When a plurality of inspection areas are set, a plurality of areas of the captured image corresponding to the plurality of inspection areas are cut out (see FIG. 5).
[0037]
Next, in step S103 (binarization), the image of the inspection area in the captured image is binarized with a predetermined threshold. For the threshold value, for example, a frequency distribution of pixel values is obtained in an image of an inspection area, and two peaks of a distribution of large (bright) pixel values and a peak of small (dark) pixel values can be clearly distinguished. It is determined as a pixel value that becomes a valley of such a distribution. If there are a plurality of inspection areas, a threshold is determined for each of the inspection areas.
[0038]
Next, in step S104 (crossing pattern extraction), a crossing pattern existing in the inspection area is extracted. When the inspection area is a rectangle as shown in FIGS. 4 and 5, it is a continuous pattern that goes out of one of two sides in the vertical direction (the long side of the rectangle in the example shown in FIG. 4) and enters the other.
[0039]
Next, in step S105 (quality judgment), the number of crossing patterns extracted for the inspection area is compared with the number registered in association with the inspection area. If the numbers match, the data processing unit 3 does not detect the print smear, that is, determines that the print is good. On the other hand, if the numbers do not match, the data processing unit 3 determines that the print smear has been detected, that is, is “bad”. Although one inspection area is shown in FIG. 4, when there are a plurality of inspection areas as shown in FIG. 5, the quality of each inspection area is determined.
[0040]
When there is at least one "bad" inspection area, the printed matter for one unit is "bad", and only when all the inspection areas are "good", the printed matter for one unit is not printed. A pass / fail judgment is made to be “good”. If one unit of printed matter is “bad”, the process proceeds to step S107. On the other hand, when the print of one unit is “good”, the process proceeds to step S106.
[0041]
Next, in step S106 (alarm output), the data processing unit 3 activates the alarm device 4 to output an alarm. In addition, the data processing unit 3 displays the captured image of the printed matter for one unit and the boundary of the inspection area determined to be defective on the display 7. The operator can know the occurrence of the print stain by the alarm, and can know the position by the display.
[0042]
Next, in step S107 (end), it is determined whether the inspection of all the inspection targets (for all units) in the printed matter has been completed. If the processing has not been completed, the process returns to step S101, and the above-described subsequent steps are repeated. When the operation is completed, the operation in the inspection process is completed.
[0043]
With reference to FIG. 6, a description will be given of print smear that can be detected in the above-described example of the inspection process. In FIG. 6, dirt a is an oblique wavy line, dirt b is an oblique thick line, and dirt c is a vertical wavy line. In any case, since they cross the inspection area a, they are print stains that can be detected in the above-described inspection process.
[0044]
【The invention's effect】
As described above, according to the print smear inspection method according to claim 1 of the present invention, there is no misjudgment due to misregistration or variable information, and the area that can be inspected can be widened. A printing stain inspection method which is small and highly practical is provided.
Further, according to the printing stain inspection method according to the second aspect of the present invention, the presence / absence of printing stain is immediately determined based on the presence / absence of a traversing pattern, so that the algorithm can be simplified and the inspection speed can be increased.
Further, according to the printing stain inspection method according to the third aspect of the present invention, the inspection area can be easily set, the algorithm can be simplified, and the inspection speed can be increased.
Further, according to the printing stain inspection method according to the fourth aspect of the present invention, since the frequency of print stains flowing in the printing direction is generally high, the algorithm is simplified and the inspection speed is increased without substantially lowering the inspection performance. be able to.
Further, according to the print stain inspection method according to the fifth aspect of the present invention, the contrast of the print stain in the captured image is improved, and the inspection performance can be improved.
Further, according to the print smear inspection method according to the sixth aspect of the present invention, it is strictly determined that the printed matter is proper only when the number of patterns crossing the inspection area matches.
Further, according to the printing stain inspection method according to the present invention, the area that can be inspected can be widened, so that there is little inspection omission in areas of high importance, and each inspection area can be narrowed, so that small printing stains can be obtained. Is also detected.
Further, according to the printing stain inspection apparatus according to the present invention, there is no misjudgment due to misregistration or variable information, and the area that can be inspected can be widened. A contamination inspection method is provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a configuration of a print smear inspection apparatus of the present invention.
FIG. 2 is a flowchart showing a setting process in the print smear inspection apparatus of the present invention.
FIG. 3 is a flowchart showing an inspection process in the print smear inspection apparatus of the present invention.
FIG. 4 is a schematic diagram showing an inspection area (one place) set in the print smear inspection apparatus of the present invention.
FIG. 5 is a schematic diagram showing an inspection area (a plurality of locations) set in the printing smear inspection apparatus of the present invention.
FIG. 6 is a schematic diagram showing a relationship between an inspection area set in the print smear inspection apparatus of the present invention and detectable smear.
[Explanation of symbols]
Reference Signs List 1 camera 2 photoelectric sensor 4 alarm 5 keyboard 6 mouse 7 display 11 printer 100 printed matter 101 dirt

Claims (8)

An inspection area setting step of setting a predetermined inspection area in a captured image of a printed matter,
A binarizing step of binarizing the image of the inspection area with a predetermined threshold value to generate a binarized image;
A number calculating step of calculating the number of patterns crossing the inspection area in the binary image;
A stain determination step of determining the presence or absence of print stains in the inspection area based on the number,
A printing stain inspection method, comprising: 2. The print smear inspection method according to claim 1, wherein the predetermined inspection area is an area where a crossing pattern does not exist in a proper printed matter. 3. The printing smear inspection method according to claim 1, wherein the predetermined inspection area is a rectangular shape including two horizontal sides perpendicular to the printing direction and two vertical sides parallel to the printing direction. A print smear inspection method characterized by being an area. 4. The method according to claim 3, wherein the number is the number of patterns crossing from one of the two horizontal sides to the other. 5. The print smear inspection method according to claim 1, wherein the captured image is an image captured through a complementary color filter of ink color. 6. The print smear inspection method according to claim 1, wherein the smudge determination step includes no print smear when the number in the inspection reference print matches the number in the inspection target print, and prints in other cases. A printing stain inspection method, which is a step of determining that there is stain. 7. The print smear inspection method according to claim 1, wherein a plurality of inspection areas are set in a captured image of the printed matter, and the series of processes is performed on each of the plurality of inspection areas. 8. A printing stain inspection method characterized by the above-mentioned. Inspection area setting means for setting a predetermined inspection area in a captured image of a printed matter, binarization means for binarizing the image of the inspection area with a predetermined threshold value to generate a binarized image, Print stains comprising: a number calculating means for calculating the number of patterns crossing the inspection area in the coded image; Inspection equipment.

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