JPH09311030A - Method and apparatus for inspection of quality - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus by which a defect part is detected with high accuracy, by which a waste to throw away the whole is eliminated when a defect exists only in an unused part or an unimportant part, by which the defect part is evaluated flexibly, by which an object to be thrown away is reduced to a minimum and whose economical efficiency is enhanced. SOLUTION: Gray levels in the corresponding part of a multigradation area image formed by imaging a face, to be inspected, on a sheet printed object 1 to a reference multigradation area image are compared, and a defect part is judged on the basis of an allowable value from a compared result. Since the defect part is judged on the basis of the allowable value from the compared result of the gray levels, the defect part can be detected without being influenced by the condition such as the shade of the color of the ground, the uneven shape or the like of the face to be inspected, and the defect part can be evaluated flexibly. In addition, when they are compared, a part whose inspection is not required such as an unused part other than a packing box structure 2 in a multigradation area image to be inspected or an unimportant part which is hidden in the use of the packing box structure 2 is mask-treated 70 so as to be removed from an object to be inspected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a long printed material in which a plurality of packaging box components are repeatedly printed as one set,
Such as sheet-fed printed matter in which a plurality of packaging box components are printed, printed matter such as labels attached to release paper, printed matter in which a lid of a food container is printed on a long film of aluminum, etc. Various inspected products in a state where the product part is integrated with unused parts, and printing stains on various inspected products such as wallpaper that can be excluded from the inspection target by overlapping parts when using, The present invention relates to a quality inspection method and a quality inspection device used for detecting various defects such as adhesion of foreign matter.

[0002]

2. Description of the Related Art For example, a sheet-fed printed matter 1 shown in FIG. 12 is formed by repeatedly printing a plurality of packaging box constituents 2 on a cardboard as a set, and then cutting the packaging box constituents 2 into a square. To be done. The above set of packaging box constructions 2 is printed in a predetermined arrangement so as not to waste material as much as possible (in FIG. 12, four packaging box constructions 2 are shown as one set, but the number is Optional.) Each packaging box structure 2 is shown in FIG.
As shown in, after being punched by a press machine,
As it is obtained by forming a fold line or a perforation line, the outline to be punched, the fold line, and the perforation line are not displayed in the printed state, but in FIG. Indicates the planned punched outline by a one-dot chain line, and the planned folds and perforated cut-off lines by a two-dot chain line.

In each packaging box structure 2, side pieces 6 and 7 are connected to one side edge and the other side edge of the long side of the front piece 3 via folds 4 and 5, respectively. On the opposite side of the front piece 3, a back piece 9 is continuously provided via a fold 8, and on the back piece 9 an adhesive piece 11 is provided on the opposite side of the side piece 7 via a fold 10. . A top surface piece 14 and a bottom surface piece 15 are continuously provided on one side edge and the other side edge of the front surface piece 3 via folds 12 and 13, respectively. Insertion pieces 17 are continuously provided on the opposite side via folds 16, and insertion pieces 19 are provided on the bottom surface piece 15 on opposite sides of the front piece 3 via folds 18. Folding pieces 22 and 23 are continuously provided on both side short side edges of the side surface piece 6 through folds 20 and 21, respectively, and foldable pieces 22 and 23 are formed on both side short side edges of the side surface piece 7 via folds 24 and 25, respectively. 26, 27
Are continuously installed. A perforation line 2 is provided on the upper side of the back piece 9.
8 forms a sealing and opening piece 29.

The front piece 3, the side pieces 6, 7, the back piece 10, the top piece 14, the bottom piece 15, and the sealing / unsealing piece 29 include letters, numbers, symbols 30, bar codes 31, etc. for explaining stored items. Is printed.

From the sheet-fed printed matter 1 is punched out along the predetermined outline as described above, and the folds 4, 5, 8, 1 are formed.
0, 12, 13, 16, 18, 20, 21, 24, 25
By forming the perforation cut line 28, the packaging box structure 2 is obtained.

Then, as shown in FIG.
Bend the side pieces 6 and 7 in a right angle direction, bend the back piece 9 in a right angle direction along the fold line 8, and bend the sticking piece 11 in a right angle direction along the fold line 10 The piece 11 is attached to the inner surface of the side piece 6. Then, the folding pieces 23 and 27 are bent at right angles along the folds 21 and 25, the bottom piece 15 is bent at right angles along the folds 13, and the insertion pieces are further bent along the folds 18. The bottom of the packaging box can be closed by bending 19 at a right angle, inserting it into the inside of the back piece 9, and adhering it. Next, store items from the upper opening,
Bend the folding pieces 22 and 26 at right angles along the folds 20 and 24, bend the top surface piece 14 at right angles along the folds 12, and further insert the insertion pieces 17 along the folds 16. It is bent at a right angle, inserted into the back piece 9 and sealed and opened 2
By affixing to 9, the packaging box 32 in a sealed state can be constructed.

Conventionally, in order to detect various defects such as print stains and adherence of foreign matter on the above-mentioned sheet-fed printed matter 1, a linear C is detected.
An image of the surface to be inspected (printing surface on the front side) of the sheet-fed printed matter 1 traveling using a CD line sensor or the like is imaged, the image signal obtained by imaging is differentiated to detect the density change of the surface to be inspected, and this differentiation A method is known in which a defective portion of the sheet-fed printed material 1 is detected by comparing and comparing a signal pattern obtained by binarizing a waveform with a master pattern which is created in advance in a storage means. There is.

[0008]

However, in the quality inspection method by the binarization processing of the above-mentioned conventional example, not only the portion of the packaging box structure 2 used as a product but also the portion not used as a product is inspected. The unused part cannot be removed from the inspection target. Therefore, as shown in FIG. 12, even if there is no defect in the part of the packaging box structure 2 that is a product and there is a defect 33 only in the unused part, a sheet-fed printed product including the packaging box structure 2 that is a product. 1 is defective and will be disposed of, which is uneconomical.

Further, as described above, when the packaging box structure 2 constitutes the packaging box 32, the front piece 3 and the back piece 9 are particularly conspicuous, not only affecting the product image, but also the stored items are particularly medicines. In some cases, it is necessary to detect with a strict accuracy because it may be dangerous because the numerical value such as the content display changes to another numerical value due to dirt, so it is necessary to detect it with strict accuracy. Although it is not necessary to perform detection with strict precision as in No. 9, it is necessary to perform detection with normal precision because it is relatively conspicuous and affects the product image. In contrast,
Since each piece other than the front piece 3, the back piece 9, and the side pieces 6, 7 is inconspicuous or hidden in the assembled state as the packaging box 32, it is not so important as each piece such as the front piece 3 and the like. It should be detected with a moderate accuracy. However, in the quality inspection method by the binarization processing of the above-mentioned conventional example, it is difficult to detect at the determination level with different accuracy in the important part and the non-weight part,
Even if there is a defect in an unimportant portion, the whole sheet-fed printed matter 1 is discarded, which is uneconomical as in the above case.

Further, in the quality inspection method using the binarization process, the setting of the judgment level is delicate, and the defect detection accuracy is greatly influenced by the suitability or unsuitability of the setting of the judgment level. Further, since the defective portion is detected only by the density change obtained by the differential waveform, the detection accuracy differs depending on whether the background color is dark or light.

If a defect is detected only by the density change obtained by the differential waveform as described above, FIG.
As shown in FIG. 15A, the stain 101 having a relatively large area and a relatively large area on the line J-J shown in FIG.
(B), (c), the density on the JJ line shown in (d), the differential processing (converting the temporal change amount into a voltage value), the difference (the constant voltage or more is set to "1" by binarization). As is clear from the above, since the signal pattern is gentle, it is determined that it is not a defective portion. On the other hand, not only the dark stain 102 having a relatively small area on the line K-K as shown in FIG. 16A, but also the light stain having a relatively small area, and the light dirt having a relatively small area are also included. 16 (b), (c),
As is clear from the concentration on the KK line shown in (d), the differential processing (converting the temporal change amount into a voltage value), and the difference (binarization, a certain voltage or more is set to “1”), it is sharp. Since it becomes a signal pattern, it is determined that it is a defective portion.

However, such a detection method does not always correspond to human visual defect recognition. For example,
Even if the stain range on the surface to be inspected is extremely narrow, if the density difference between the inside and the outside of the stain range is large, it is recognized as "conspicuous stain" by human vision. Further, even if the stain concentration is about the same, it is recognized as "conspicuous stain" or "not noticeable stain" depending on whether the stain range is large or small. And, while "conspicuous stains" need to be reliably excluded from products, on the other hand, "conspicuous stains" often do not need to be excluded, and it is extremely difficult to judge defects in consideration of such human visual sensibilities. Met.

The present invention solves the above-mentioned conventional problems, and can detect a defective portion with high accuracy regardless of the conditions such as the shade of the ground color of the surface to be inspected. It is possible to eliminate the waste of disposing of the whole by only having defects in unused parts and insignificant parts that are hidden during use, and moreover, because the defective parts can be evaluated flexibly, the disposal target is minimized. Therefore, it is an object of the present invention to provide a quality inspection method and a quality inspection device which can be improved in economic efficiency.

[0014]

The quality inspection method of the present invention for achieving the above object is based on multi-gradation image data output from the image pickup means by picking up an image of an object to be inspected by the image pickup means. A multi-gradation area image is created on the target multi-tone area image, and an unnecessary portion of the inspection multi-tone area image is masked and removed from the inspection target. The level is compared with the density level of each corresponding portion of the reference multi-gradation area image, and the defective portion is judged based on the allowable value at each judgment level from this comparison result.

According to another quality inspection method of the present invention for achieving the above object, in the above quality inspection method, when comparing the density levels of respective portions of the inspection required portion in the inspected multi-gradation area image, according to the importance level. Therefore, the comparison is made at the judgment levels with different accuracy.

In the above quality inspection method, when the defective portion is determined in consideration of the amount of deviation between the inspected multi-gradation area image and the reference multi-gradation area image, and the image is picked up by the image pickup means. It is preferable to detect the brightness of the inspection object and change the brightness of the density level of the reference multi-gradation area image in accordance with the detection result.

Further, the density level difference between the inspected multi-tone area image and the reference multi-tone area image is cumulatively added in a desired direction by a certain amount, emphasized and compared, or the density of the inspected multi-tone area image is calculated. It is preferable to cumulatively add a certain amount in the desired direction for emphasis and compare the density with the density level of the reference multi-tone area image for which a certain amount has been cumulatively added in the desired direction.

Further, the density level difference is used as the allowable value, and as the allowable value of this density level difference, the density of each multi-gradation line image forming each row of the reference multi-gradation area image is determined for each determination level with different accuracy. The allowable density level is added to the level to create a bright defect multi-gradation line image, while the allowable density level is subtracted from the density level of the multi-gradation line image of the reference multi-gradation area image to dark defect multi-gradation It is possible to create a line image and use the bright defect multi-tone line image and the dark defect multi-tone line image as the upper limit value and the lower limit value of the allowable range.

Further, the permissible value of the density level difference is set to the heavy defect level and the light defect level for each judgment level having different accuracy, and when the density level difference exceeds the heavy defect level, it is a defective portion. If the difference in the density level is between the light defect level and the heavy defect level, the light defect level is deviated at a level common to the judgment levels with different accuracies, or at a level different for each judgment level with different accuracies. By analyzing the shape of the existing portion, it is preferable to determine that the deviation portion is a defect portion when the deviation portion is wide, and to determine that the deviation portion is not a defect portion when the deviation portion is narrow. It is also possible to set the light defect level in multiple stages.

The permissible value can also be defined by the sum of the density difference and the area, or the reference value of the size in the horizontal and vertical directions.

A quality inspection apparatus according to the present invention for achieving the above object comprises an image pickup means for picking up an image of an object to be inspected, and an object to be inspected based on multi-tone image data output from the image pickup means. A storage means for storing the gradation area image and the reference multi-gradation area image, and a mask processing is performed on an unnecessary portion of the inspection multi-gradation area image to remove it from the inspection object, The density level of each part of the area requiring inspection in the area image is compared with the density level of each corresponding part of the reference multi-tone area image, and the defect location is judged based on the allowable value at each judgment level from this comparison result. And means.

In the above-mentioned quality inspection apparatus, a correction means for correcting the amount of displacement between the inspected multi-tone area image and the reference multi-tone area image is provided, and the inspected object when the image is picked up by the image pick-up means. It is possible to provide a detection unit that detects the brightness of the image and changes the brightness of the density level of the reference multi-gradation area image in accordance with the detection result.

Then, the determination means, when comparing the density levels of the respective portions of the inspection-needed area in the inspected multi-gradation area image as described above, compares at different determination levels with different accuracy according to the importance, and the determination is made. The density level difference is used as the tolerance value at that time, and the tolerance value is divided by the bright defect multi-gradation line image and the dark defect multi-gradation line image, and the shape can be analyzed to make a determination, or The allowable value used for the determination can be divided by the reference value of the density difference and the total area.

According to the present invention, a multi-gradation area image is created on the basis of multi-gradation image data obtained by picking up an image of the surface to be inspected, and the multi-gradation area image is inspected. Pattern matching with the reference multi-tone area image is performed to compare the density levels of the corresponding portions of both images, and the defective portion is determined based on the allowable value from the comparison result. In this way, the defect location is determined based on the allowable value from the density level comparison result.
The defect location can be flexibly evaluated. Further, in the above comparison, the unnecessary portions in the multi-tone area image to be inspected, unimportant portions such as hidden portions when used, are removed from the inspection target by masking, so that there is no defect in that portion. Even if there is, it is possible to eliminate the waste of discarding the whole.

Further, when comparing the density levels of the respective portions of the inspection-needed area in the inspected multi-gradation area image, the determination levels with different precisions are compared according to the importance, and the portions that do not affect the commercial value are compared. By determining that a light defect is not a defect, it is possible to eliminate the waste of discarding the whole.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment of the present invention will be described. 1 and 2 are a schematic plan view and a partially cutaway schematic side view showing a transport mechanism section of a quality inspection device according to a first embodiment of the present invention, and FIG. 3 is a CCD line sensor camera and a light source in the quality inspection device. FIG. 4 is a front view showing an arrangement example, and FIG. 4 is a block diagram showing a processing unit of the quality inspection apparatus.

First, a quality inspection apparatus according to an embodiment of the present invention will be described. In FIG. 1 and FIG. 2, 41 is a setting section for setting the sheet-fed printed matter 1 in a stacked state, 42 is a feeding section for feeding the sheet-fed printed matter 1 of the setting section 41, 43 is a sheet-fed printed matter fed from the feeding section 42. 1 is a conveying belt, 44 is a roller group for guiding the traveling of the conveying belt 43, 45
Is an inspection unit for the sheet-fed printed matter 1 to be conveyed, and 46 is an inspection unit 45.
The sorting unit for sorting the non-defective product and the defective product of the sheet-fed printed matter 1 inspected in 1., the collecting box 47 for collecting the defective sheet-fed printed matter 1, 48 the stock section for stocking the non-defective sheet-fed printed matter 1, and 49 for each section It is the control panel of.

In the inspection section 45, as shown in FIGS. 1 to 3, an image pickup section 50 is arranged above the printing surface of the traveling sheet-fed printed matter 1. Reflection illumination light sources 51 are arranged on both sides of the image pickup section 50 in the traveling direction of the sheet-fed printed matter 1, and transmission illumination light sources 52 are arranged so as to face the image pickup section 50 with the sheet-fed printed matter 1 interposed therebetween. In the illustrated example, the reflective illumination and the transmissive illumination are used together, but either one may be used depending on the type of the inspection object. Further, visible light, infrared rays, ultraviolet rays, γ rays, χ rays and the like can be used for these illuminations. In the illustrated example, the imaging unit 50 has five
Five CCD line sensor cameras (hereinafter, simply referred to as cameras) 50a to 50e, which are linear sensors of 12, 1024, 2048, 5000 bits, etc., are installed and run along the width direction of the plain paper 1 on which they run. The entire width of the sheet-fed printed matter 1 is sequentially imaged.

In FIG. 4, 60 is an image memory,
The inspected image on the print display surface of the sheet printed matter 1 output from the cameras 50a to 50e is stored as a multi-valued image. For example, 256 sequentially output from the cameras 50a to 50e
While storing the data of the multi-gradation line image of the stage,
Create a multi-tone area image. 61 is an X correction circuit, 62
Is a Y correction circuit, which stores a print display position serving as an inspection reference from the images output from the cameras 50a to 50e, extracts a correction amount by comparing it with the print display position of the inspection target, and stores it in the image memory 60. A correction amount is added when the gradation area image is read out to move the multi-gradation area image so that the positions of the inspection target image and the inspection target reference image are the same. The X correction circuit 61 corrects the image in the direction perpendicular to the traveling direction of the sheet printed matter 1, and the Y correction circuit 62 corrects the image in the same direction as the traveling direction of the sheet printed matter 1.

In order to perform the above correction, either or both of the inspection image and the reference image are moved inside the storage means so that the inspection image and the reference image are superposed on each other and both the images are superposed. To be compared. As a method of moving an image, known means can be appropriately adopted, and any of software processing on a memory and hardware processing using a dedicated logic circuit can be arbitrarily used. As the software processing, for example, a method of recognizing a feature point of an image and moving the image based on the feature point or a method of moving the image based on the roughly extracted image contour can be adopted. . Alternatively, a large number of reference images assuming image shifts are stored in memory in advance,
It is possible to employ a method of sequentially comparing the inspected image with the reference image, extracting a correction amount when they match, and moving the inspected image.

Reference numeral 63 denotes an average density detection circuit, which is used by the camera 5
Based on the print display images output from 0a to 50e, the print display average density serving as the inspection reference is detected, and the correction amount is extracted by comparing with the print display average density of the inspection target.
An image reference memory 64 stores a print display image serving as an inspection reference as a multi-valued image. For example, a reference (master) image 2 of a normal sheet-fed printed matter 1 captured in advance
A multi-tone area image of 56 steps is stored. Reference numeral 65 denotes a permissible value selection memory, which is a multi-tone area image to be inspected output from the image memory 60 and the reference image memory 6 as described later.
A plurality of density allowable values for comparing each pixel with the reference multi-tone area image output from No. 4 are stored and selected.

As described above, the packaging box structure 2 includes the packaging box 32.
When configuring the above, since the front piece 3 and the back piece 9 are not only particularly conspicuous parts but also important for the content display and the product image, the tolerance value of the density level is strictly set, and the side pieces 6, 7 are Since the weight is a product image in a place that stands out next to the front piece 3 and the back piece 9, the allowable value of the concentration level is set normally, and the other pieces are inconspicuous or hidden when assembled as the packaging box 32. Since it is not as important as the above-mentioned pieces at the place to be performed, the allowable value of the density level is set to be relaxed so that the window processing can be performed at each judgment level. That is, the permissible value of the density level difference is lightened on the “bright” side obtained by adding a certain permissible value to the reference density level, which is the true value of the reference multi-gradation line image data, for each determination level having different accuracy. The light defect density level and the heavy defect density level are set on the "dark" side obtained by subtracting a certain allowable value from the defect density level and the heavy defect density level, and the reference density level. In addition, a determination level based on the shape in the x direction (width direction) and the y direction (flow direction) at a portion deviating from the light defect level is set for each determination level with different accuracy. The determination levels in the x direction and the y direction in the portion deviating from the light defect density level may be common to determination levels having different precisions. Table 1 shows an example of the determination level when different, and Table 2 shows an example of the determination level when common. In addition, the packaging box structure 2 in the sheet-fed printed matter 1
The other parts are set so that the allowable value becomes maximum so that the mask processing can be performed in the determination.

[0033]

[Table 1]

[0034]

[Table 2]

Reference numeral 66 denotes an image calculation circuit, which is an image memory 6
The density of each portion of the inspected multi-gradation area image to which the correction amount detected by the average density detection circuit 63 after position correction extracted from 0 is added corresponds to the reference multi-tone area image extracted from the reference image memory 64. The density level of each part is compared, and the defective portion is determined based on the allowable value extracted from the allowable value selection memory 65 for this comparison result. That is, since the maximum allowable value is obtained for the portion of the sheet-fed printed material 1 other than the packaging box constituent 2, it is masked and excluded from the comparison target, and the density level obtained by comparison in the packaging box constituent 2 is compared. If the difference exceeds the allowable value, it is determined to be a defect, and if it does not exceed the allowable value, it is determined that there is no defect. Reference numeral 67 denotes a defect detection circuit, which measures defect dimensions in the x direction and the y direction from the defect image extracted by the image calculation circuit 66, and determines the determination levels in the x direction and the y direction set in the allowable value selection memory 65. Information exceeding the position and size of the detected defect is stored. Each of the memories 60, 6
4, 65, each circuit 61, 62, 63, 66, 67 is CP
It is controlled by U (not shown).

Next, a quality inspection method according to the first embodiment of the present invention will be described together with the operation of the quality inspection apparatus. 5 to 9 are explanatory views of the principle of the quality inspection method according to the first embodiment of the present invention.

As shown in FIGS. 1 and 2, the sheet-fed printed matter 1 stacked on the setting section 41 is successively fed by the operation of the feeding section 42, and is conveyed by the guide of the roller group 44.
Transport by 3. During this period, the inspection unit 45 inspects the sheet printed matter 1 for defects, and the defective sheet-fed printed matter 1 is collected in the collection box 47 by the operation of the sorting unit 46 according to a command from the inspection unit 45. The leaf print 1 is stocked in the stock section 48.

The inspection method in the inspection section 45 will be described in detail. The sheet-fed printed matter 1 traveling as described above.
Is irradiated by the illumination light sources 51 and 52, and the surface to be inspected of the sheet-fed printed matter 1 extends over the entire length in the width direction of the camera 50a.
Images are sequentially captured by 50e. The image memory 60 is the camera 5.
Data of 256 gradation multi-gradation line images sequentially output from 0a to 50e is stored and a multi-gradation area image is created. On the other hand, the X correction circuit 61 and the Y correction circuit 62
Stores the print display position serving as the inspection reference from the image data output from the cameras 50a to 50e, and extracts the correction amount by comparing with the print display position of the inspection target. Further, the average density detection circuit 63 detects the print display average density serving as the inspection reference from the image data output from the cameras 50a to 50e, and compares it with the print display average density of the inspection target to extract the correction amount.

The reference image memory 64 is an X correction circuit 62 and a Y correction circuit 6 for the inspected multi-tone area image of the image memory 60.
The image is moved by the correction amount of 3, and the reference multi-tone area image which is the inspection reference and the print display position are matched and stored. And
The image calculation circuit 66 masks unnecessary portions of the multi-tone area image to be inspected, and compares the density levels of the other portions with the density levels of the corresponding portions of the reference multi-tone area image. Then, the defective portion is determined based on the allowable value of the density level difference between the corresponding portions of both images. The defect detection circuit 67 analyzes the shape of the defective portion in the inspected multi-tone area image, which is determined to be a light defect by the image calculation circuit 66, and determines whether or not it is a defect. During this period, the multi-tone area image of the surface to be inspected created as described above is displayed on the monitor TV.
It is displayed on the screen (not shown) and can be visually inspected by an inspector.

To explain these determination operations in more detail, as described above, the unnecessary value on the outside of each packaging box structure 2 in the sheet-fed printed product 1 is maximized by the maximum allowable value.
As indicated by the diagonal lines in FIG. 5, since the mask processing 70 is performed to exclude from the inspection target, even if there is a defect such as the stain 71 in this unnecessary portion, it is not detected.

FIGS. 6A, 6B and 7A,
(B) shows the principle of image density detection. FIG. 6 (a)
And one of the two letters V in the reference image 72 and the inspected image 73 shown in FIG.
Is on the “dark” side, and the other white letter “V” is on the “bright” side, the waveform on the LL line is as shown in FIG.
7B and FIG. 7B. Here, FIG.
Defects 71 such as stains in the inspection image 73 shown in (a)
Appears as a waveform shape portion 74 different from the waveform shape in the reference image 72. Then, if the density difference exceeds the heavy defect density level at the set judgment level, or if the size condition is also satisfied between the light defect density level and the heavy defect density level, the sheet-fed printed matter 1 as the inspection object has a defect. Therefore, the X correction circuit 61,
It is important to prevent the characters 30 and the bar code 31 from expanding by the position correction of the Y correction circuit 62 and to perform automatic density correction by the average density detection circuit 63.

FIGS. 8 and 9 (a) to 9 (e) show the case of determining the presence / absence of a defect of the surface piece 3 in one packaging box construct 2 for convenience. 9 (a) to 9 (e)
In, the density levels of the inspected multi-gradation line image and the reference multi-gradation line image data of each packaging box structure 2 in the sheet printed matter 1 (printed characters etc. 30, bar code 3
For the sake of convenience, the waveform shape of No. 1 is the same as that of the waveform 81, which is deleted and shown on the flat surface). Strictly speaking, the density levels of these multi-gradation line image data (hereinafter, referred to as reference density levels). ) 81, if it appears as a change in the waveform shape on either the “dark” side or the “bright” side, it will be a defect as the packaging box structure 2 itself, but the inconspicuous defect as described above will be a defect. A certain permissible value is set for the density level difference for the multi-gradation line image data of the reference image so as not to recognize it.

As the above-mentioned allowable value, the light defect density level 82a and the heavy defect density level 82a on the "bright" side obtained by adding a certain allowable value to the reference density level 81 which is the true value of the multi-gradation line image data. 82b and a light defect concentration level 83a and a heavy defect concentration level 83b on the "dark" side obtained by subtracting a certain allowable value from the reference concentration level 81. And, in principle, this light defect concentration level 82
If the inspected multi-gradation line image data is contained in the area defined by a and 83a, it is determined that it is not a defect, and if there is a portion deviating from the above area, this portion is light or It is determined to be a serious defect (the density levels 81, 82, and 83 are curved because the illuminance by the light sources 51 and 52 becomes weaker on both outer sides).

According to this criterion, the portion of the dirt 75 having a relatively small area and located on the line AA in FIG.
As shown in FIG. 9A, the change in the waveform shape is “dark”.
Since it is within the light defect concentration level 83a on the side, it is detected that it is not a defect. As shown in FIG. 9 (b), the change in the waveform shape of the comparatively narrow area and thick dirt 76 on the line BB in FIG. 8 deviates from the heavy defect concentration level 83 b on the “dark” side. Therefore, it is detected as a serious defect. C-C in FIG.
A relatively large area of relatively light dirt 77 on the line
As shown in FIG. 9C, the change in the waveform shape is “dark”.
Since it deviates from the light defect concentration level 83a on the side, it is detected as a light defect. As shown in FIG. 9D, the waveform 78 of the comparatively small area 78 having a relatively small area on the line D-D in FIG. 8 deviates from the light defect concentration level 83 a on the “dark” side. Therefore, it is detected as a light defect.
Light-reflecting stain (or hole) on the line EE in FIG.
As shown in FIG. 9E, since the change of the waveform shape deviates from the heavy defect concentration level 82b on the "bright" side, 79 is detected as a heavy defect.

According to the above determination method, it is possible to detect a defect to some extent realistically, but this determination method alone may not be sufficient. For example, depending on the density range and the density difference between the stained area and the color of the stain and the ground color, it may be relatively inconspicuous or relatively conspicuous on human vision, and therefore, such a stain is targeted for removal, Alternatively, the following determination is made in order to address the problem of whether or not to remove from the removal target.

As shown in FIG. 9C, the light defect concentration level 82a on the "bright" side and the light defect concentration level 83 on the "dark" side.
If the shape of the portion deviating from the area defined by a, i.e., the dimensions of x and y (see FIG. 8) are relatively large, the stained state is recognized as a light defect. As shown in FIG. 9 (d), when the shape of the deviated portion, that is, the dimensions of x and y (see FIG. 8) are relatively small, the stained state is recognized as not being a defect and sorting is performed. Although the determination can be made by monitoring the density level and the shape of the deviated portion, the determination can be made by recognizing the density level and the area of the deviated portion.

Similarly to the front surface piece 3, the back surface piece 9 is also detected as to whether or not there is a defect, and the side surface pieces 6 and 7 are detected as to whether or not there is any defect at the normal level in Table 1 as described above. For each piece, the presence or absence of defects is detected at the relaxation level in Table 1 in the same manner as above.

In the above detection example, when the density level difference is between the light defect level and the heavy defect level, the shape of the portion deviating from the light defect level at a different level is analyzed for each judgment level having different accuracy. According to this, when the deviation portion is wide, it is determined to be a defective portion, and when it is narrow, it is determined to be not a defective portion. However, as shown in Table 2, the light defect is at a level common to determination levels having different accuracies. By analyzing the shape of the portion that deviates from the level, it is possible to determine that the deviation portion is a defect portion when it is wide and to determine that it is not a defect portion when it is narrow.

According to the present embodiment, the dark stains 76 in a relatively small area, the relatively light stains 77 in a relatively large area, and the light-reflecting stains (or holes) 79 are determined to be defective portions. It is determined that the light stain 75 having a relatively small area and the light stain 78 having a relatively small area are not defective. On the other hand, in the inspection method using the differential binarization processing of the above-mentioned conventional example, the comparatively wide area, which is conspicuous, and the relatively pale stain 77 is shown in FIG.
Since it becomes a gentle signal pattern as shown in (3), it is determined that it is not a defective portion, and not only light reflectivity (or hole) 79 and dark stain 76 in a relatively small area, but also relatively light in a relatively small area. The stain 76, and also the light stain 75 having a relatively small area has a rapid signal pattern as shown in FIG. 16, and is therefore determined to be a defective portion. From this, it is apparent that the present embodiment can detect a defective portion with high accuracy and can flexibly evaluate the defective portion. Further, since the position shift of the image to be inspected with respect to the reference image is corrected, the characters 30, the bar code 31, etc. printed on the packaging box structure 2 can be clearly identified, and it is a defect due to expansion if not corrected. It is possible to prevent erroneous recognition of.

Next, a quality inspection method according to the second embodiment of the present invention will be described. FIGS. 10A to 10F are principle explanatory views showing the quality inspection method according to the second embodiment of the present invention.

FIG. 10A shows the reference multi-gradation area image 9
1, FIG. 10B shows the inspected multi-tone area image 92, and the inspected multi-tone area image 92 has a discontinuous linear defect 93 along the feeding direction Y. . FIG. 10C shows a multi-tone area image 94 in which the inspected multi-tone area image 92 is pattern-matched with a reference multi-tone area image 91. The multi-tone area image 94 has the discontinuous linear shape. Defect 93 and random noise 95 exist.

The signal waveform on the FF line of the multi-tone area image 94 after the pattern matching is as shown in FIG. 10D, and the defect 93 cannot be distinguished from the noise 95. Therefore, as shown in FIG. 10E, the density level difference after pattern matching between the inspected multi-tone area image 92 and the reference multi-tone area image 91 is a constant amount Y in the Y direction.
L is cumulatively added to obtain an emphasized image. The waveform of the cumulative addition signal having the length YL in this emphasized image is as shown in FIG. 10F, and the discontinuous linear defect 93 becomes one continuous linear shape, and is clearly distinguished from the random noise 95 and detected. can do. Then, the detected density level is set to the first
Similar to the above embodiment, it is determined whether or not there is a defect based on the allowable value.

Next, a quality inspection method according to the third embodiment of the present invention will be described. 11A to 11E are principle explanatory views showing the quality inspection method according to the third embodiment of the present invention.

FIG. 11A shows that Y is added to the input multi-gradation area image.
The reference multi-tone area image 97 is shown by cumulatively adding a fixed amount YL in the direction, and FIG. 11B shows the inspected multi-tone area image 98 which has been processed in the same manner as the reference multi-tone area image 97. The horizontal line of the edge portion of the character V in each of the images 97 and 98 indicates that sharpness is lost due to cumulative addition. When the inspection multi-tone area image 98 has a discontinuous linear defect 93 as in the second embodiment by the above processing, it becomes one continuous linear defect. FIG. 11C shows a signal waveform on the GG line of the reference multi-tone area image 97, and FIG. 11D shows 32000 levels of the signal waveform on the H-H line of the inspected multi-tone area image 98. Three
A waveform of 5000 levels is shown.

In the present embodiment, the inspected multi-tone area image 98 in which the densities are cumulatively added before the pattern matching as described above is pattern-matched with the reference multi-tone area image 97 which has been subjected to the same processing. Detect the density level difference. Then, similarly to the first embodiment, it is determined whether the detected density level is a defect based on the allowable value.

In the above second and third embodiments, the case where the cumulative addition of the density is performed in the feeding direction Y of the sheet printed matter 1 has been described, but the cumulative addition of the density may be performed in the horizontal direction X. Alternatively, the cumulative addition of the densities may be performed in both the X and Y directions.

As still another embodiment of the present invention, the permissible value of the density level difference is the sum (volume) of the density difference and the area on the “bright” side and the “dark” side, or the horizontal direction X and the vertical direction (feed direction). ) Defects can be detected more reliably by partitioning by the reference value of the Y size.

In the above-described embodiment, not only the case of printing in black on a white background but also the case of color printing can similarly determine the defective portion based on the allowable value.

In each of the above embodiments, for example,
Since the sticking piece 11 of the packaging box structure 2 is not exposed to the outside after the packaging box 32 is assembled, it can be masked during inspection. Also, when performing a quality inspection of a printed product in which a lid of a food container is printed on an aluminum film, there is a problem in hygiene if insects are attached to unnecessary parts other than the lid, and it is necessary to mask and inspect. Since it is not possible to remove it from above, it is necessary to inspect this unnecessary part with a judgment level with a moderate accuracy, to judge that the adhesion of insects is a defect, and to judge that other minor stains are not a defect. You can do this. Further, instead of using a plurality of line sensor cameras 50a to 50e, one line sensor camera may be moved in a swinging manner to continuously change the imaging target site,
In short, the surface to be inspected of the inspection object and the line sensor camera may be moved relatively. Further, in the above embodiment, the multi-gradation line image data of 256 steps is obtained, but it is also possible to obtain the multi-gradation line image data of 512 steps, 1024 steps or the like. Further, the image pickup means is not limited to the above CCD line sensor camera, and any means may be used as long as it can pick up an image of the object to be inspected and obtain multi-tone image data. Further, in the above-described embodiment, the case where the position of the multi-tone area image to be inspected is corrected in the X direction and the Y direction has been described, but reference multi-tone area images having different rotation angles are stored in advance, and these reference multi-tone area images are stored. By performing pattern matching between the multi-tone area image and the multi-tone area image to be inspected, position correction in the rotation direction (θ direction) can also be performed. Further, in addition to this, the present invention can be modified without departing from the basic technical idea thereof.

[0060]

As described above, according to the present invention, a multi-tone area image is created based on multi-tone image data obtained by picking up an image of the surface of the object to be inspected. The inspection multi-tone area image is pattern-matched with the reference multi-tone area image to compare the density levels of the corresponding portions of both images, and the defective portion is determined based on the allowable value from the comparison result. Since the defect location is determined based on the allowable value from the density level comparison result in this manner, the defect location can be detected without being affected by the conditions such as the shade of the ground color of the surface to be inspected and the uneven shape. In addition, it is possible to flexibly evaluate the defective portion. Further, in the above comparison, the unnecessary portions in the multi-tone area image to be inspected, unimportant portions such as hidden portions when used, are removed from the inspection target by masking, so that there is no defect in that portion. Even if there is, it is possible to eliminate the waste of discarding the whole. Therefore, economic efficiency can be improved and effective use of resources can be contributed.

Further, in comparing the density levels of the respective portions of the inspection required portion in the multi-tone area image to be inspected, the determination levels having different precisions are compared according to the importance, and the portions that do not affect the commercial value are compared. By determining that a light defect is not a defect, it is possible to eliminate the waste of discarding the whole. Therefore, it is possible to further improve the economical efficiency and contribute to the effective use of resources.

Further, the density level difference between the inspected multi-tone area image and the reference multi-tone area image is cumulatively added in a desired direction by a certain amount, emphasized and compared, or the density of the inspected multi-tone area image is determined. It is effective for light defects and faint defects by comparing the density level of a standard multi-tone area image that has been cumulatively added in a desired direction by a certain amount and emphasized and comparing the density by a certain amount in a desired direction. In the former case, the partial level mask function can be effectively used, and in the latter case, the detection can be performed with higher sensitivity.

Further, the density level difference is used as the allowable value, the allowable value of the density level difference is set to the heavy defect density level and the light defect density level, and when the density level difference exceeds the heavy defect density level, the defect location is detected. If the density level difference is between the light defect concentration level and the heavy defect concentration level, the shape of the portion deviating from the light defect concentration level is analyzed. It is possible to obtain a judgment result close to the visual judgment by judging that it is a spot, and if it is narrow, it is judged that it is not a defect spot.

By dividing the allowable value by the reference value of the total of the density difference and the area, the defective portion can be detected more reliably.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing a conveyance mechanism section of a quality inspection device according to an embodiment of the present invention.

FIG. 2 is a schematic side view of a partially broken section showing a transport mechanism section of the quality inspection device.

FIG. 3 is a front view showing an arrangement example of a CCD line sensor camera and a light source in the quality inspection apparatus.

FIG. 4 is a block diagram showing a processing unit of the quality inspection device.

FIG. 5 shows the quality inspection method according to the first embodiment of the present invention, and is an explanatory diagram showing a state in which unnecessary portions outside a packaging box structure in a sheet-fed printed matter are masked.

6A and 6B are reference images and their density distribution waveform charts for explaining the principle of image density detection in the same quality inspection method.

7A and 7B are diagrams of an image to be inspected and its concentration distribution waveform diagram for explaining the principle of image density detection in the same quality inspection method.

FIG. 8 is an explanatory view showing the same quality inspection method and stains on the front piece of the packaging box assembly.

9 (a) to 9 (e) show the same quality inspection method and are explanatory diagrams of the principle of detecting dirt.

10A to 10F are principle explanatory views showing a quality inspection method according to a second embodiment of the present invention.

11A to 11E are principle explanatory views showing a quality inspection method according to a third embodiment of the present invention.

FIG. 12 is a plan view showing a sheet-fed printed matter which is an example of an inspection object.

FIG. 13 is a plan view showing a packaging box structure punched from the same sheet printed matter.

FIG. 14 is a schematic perspective view of a packaging box assembled from a packaging box constituent punched out from the same printed matter.

15A to 15D are principle explanatory views in the case of detecting a defect with respect to a relatively light stain in a relatively large area which is conspicuous by a quality inspection method using a conventional differential binarization process.

16 (a) to 16 (d) are explanatory views of the principle in the case of detecting a defect with respect to thick dirt in a relatively narrow area by a quality inspection method using a conventional differential binarization process.

[Explanation of symbols]

 1 Sheet-fed printed matter (object to be inspected) 2 Packaging box structure 50 Imaging unit 50a to 50e CCD line sensor camera 60 Image memory 61 X correction circuit 62 Y correction circuit 63 Average density detection circuit 64 Reference image memory 65 Allowable value selection memory 66 Image calculation circuit 67 Defect detection circuit 70 Mask processing unit 71 Stain 72 Reference image 73 Inspected image 75 Relatively light stain in a relatively small area 76 Dark stain in a relatively small area 77 Relatively light stain in a relatively wide area 78 Comparison Comparatively light stain in a relatively small area 79 Light-reflecting stain 81 Reference concentration level 82a Light defect concentration level on the "bright" side 82b Heavy defect concentration level on the "bright" side 83a Light defect concentration level on the "dark" side 83b " Heavy defect concentration level on the "dark" side

Claims (14)

[Claims] 1. An image of an object to be inspected is picked up by an image pickup means, a multi-tone area image is created based on multi-tone image data output from the image pick-up means, and a multi-tone area image is inspected. The portion not requiring inspection is masked and removed from the subject to be inspected, and the density level of each portion of the portion requiring inspection in the inspected multi-tone area image is compared with the density level of each corresponding portion of the reference multi-tone area image, A quality inspection method for determining a defective portion based on an allowable value at each determination level from the comparison result. 2. The quality inspection method according to claim 1, wherein when comparing the density levels of respective portions of the inspection-required portion in the inspected multi-gradation area image, the determination levels are different in accuracy according to the degree of importance. 3. The quality inspection method according to claim 1, wherein the defective portion is determined in consideration of a deviation amount such as a position between the inspected multi-tone area image and the reference multi-tone area image. 4. The brightness of an object to be inspected when an image is picked up by the image pickup means, and the brightness of the density level of the reference multi-gradation area image is changed according to the detection result. Quality inspection method described in either. 5. The quality according to claim 1, wherein the density level difference between the inspected multi-tone area image and the reference multi-tone area image is cumulatively added in a desired direction by a certain amount and emphasized and compared. Inspection methods. 6. A density level of a multi-tone area image to be inspected is cumulatively added in a desired direction by a certain amount to emphasize and compared with a density level of a reference multi-tone area image in which a certain amount of density is cumulatively added in a desired direction. The quality inspection method according to any one of claims 1 to 4. 7. The density level difference is used as the allowable value.
7. The quality inspection method according to any one of 1 to 6. 8. The bright defect multi-level, which is created by adding the permissible density level difference to the density level of the multi-gradation line image of the reference multi-gradation area image for each judgment level with different accuracy. 8. The quality inspection method according to claim 7, wherein the tone defect line image and the dark defect multi-tone line image are created by subtracting an allowable density level from the density level of the multi-tone line image of the reference multi-tone area image. . 9. An allowable value of the density level difference is set to a heavy defect level and a light defect level for each determination level having different accuracy, and when the density level difference exceeds the heavy defect level, it is determined as a defective portion. If the density level difference is between the light defect level and the heavy defect level, the shape of the part that deviates from the light defect level at the level common to the judgment levels with different accuracy is analyzed, and the deviation part is analyzed. 9. The quality inspection method according to claim 8, wherein when the value is wide, it is determined that it is a defective portion, and when it is narrow, it is determined that it is not a defective portion. 10. An allowable value of the density level difference is set to a heavy defect level and a light defect level for each determination level with different accuracy, and when the density level difference exceeds the heavy defect level, it is a defective portion. If the density level difference is between the light defect level and the heavy defect level, the shape of the part that deviates from the light defect level at a different level for each judgment level with different accuracy is analyzed. 9. The quality inspection method according to claim 8, wherein when the value is wide, it is determined that it is a defective portion, and when it is narrow, it is determined that it is not a defective portion. 11. The quality inspection method according to claim 1, wherein the allowable value is defined by a sum of density difference and area, or a reference value of horizontal and vertical sizes. 12. An image pickup means for picking up an image of an object to be inspected, and an inspected multi-tone area image and a reference multi-tone area image created based on multi-tone image data output from the image pick-up means are stored. The storing means and the inspection unnecessary portion in the inspected multi-tone area image are masked and removed from the inspection object, and the density level of each portion of the inspection necessary portion in the inspected multi-tone area image is set to the above. A quality inspection apparatus comprising: a determination unit that compares a density level of each corresponding portion of a reference multi-gradation area image and determines a defective portion based on an allowable value at each determination level based on the comparison result. 13. The quality inspection apparatus according to claim 12, further comprising a correction unit that corrects a displacement amount such as a position between the inspected multi-tone area image and the reference multi-tone area image. 14. A detection means for detecting the brightness of an object to be inspected when an image is picked up by the image pickup means and changing the brightness of the density level of the reference multi-gradation area image in accordance with the detection result. Item 12. The quality inspection device according to item 12 or 13.