JP3245771B2 - Printing inspection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting a printed state such as a production date or a product number printed on a product.

[0002]

2. Description of the Related Art On a bottom portion of a can product such as a beverage can or a food can, a printing device prints a manufacturing date, a product number, etc. in about 5 × 7 dots in numbers, alphabets, symbols or a combination thereof. However, if the printing state is defective, the date of manufacture or product number cannot be read depending on the degree, and it is necessary to remove the defective product. In the case where the products with defective printing continue, the printing device must be adjusted. Therefore, the product with defective printing is eliminated following the printing by the printing device.

In order to eliminate such defective printing products, the following devices have been put to practical use. That is, a plurality of cans are placed on a conveyor at predetermined intervals with the bottom part facing upward,
The cans convey each can in a line. In the transport area of the can, a print head for ejecting ink to a plurality of positions is arranged so as to face the bottom of the can, and a predetermined number and symbol are set on the bottom of each can by the print head. Printed. Above the conveyor downstream of the print head, an image pickup device provided in the print inspection device is supported by a support member, and when the can conveyed by the conveyor reaches a position directly below the image pickup device, the image pickup device Images the bottom of the can. On the exit side of the imaging device, an exclusion cylinder that pushes the side of the can in a direction orthogonal to the direction in which the can is transported is arranged facing the transport area of the can.

[0004] The print inspection device is provided with a dictionary,
In the dictionary, for example, an image obtained by imaging a can that is normally printed with 5 × 7 dots is binarized, the character portion is expanded, and each dot is combined, and then the printing direction is determined based on the printing position. , And a plurality of reference patterns obtained by performing a process of sequentially cutting out each character in a predetermined character frame are registered in advance. The print inspector calculates the degree of coincidence between each of a plurality of target patterns obtained by performing the same processing as before on the image obtained by imaging the can to be inspected and the corresponding reference pattern in the dictionary, and calculates If the degree of coincidence is lower than a predetermined threshold value, it is determined that there is a serious defect such as no printing, erroneous printing, or missing characters, and the exclusion cylinder is operated to remove the heavy defective can from the conveyor.

[0005]

By the way, as the temperature changes from a low temperature to a high temperature, the color changes due to a change in temperature, for example, gradually changes from black to red, or the color changes almost even when the temperature changes. In some cases, an appropriate mark is applied to the bottom of the can using ink that does not
If the date of manufacture or product number is printed on the bottom of such a can, the mark may overlap with the date of manufacture or product number. For cans where the mark is overlapped with the date of manufacture or product number, etc., when the printed state of the date of manufacture or product number is inspected by the conventional print inspection device as described above, the actual printed state is good. There has been a problem that erroneous detection of judging that a portion overlapping a mark is a heavy defect occurs frequently.

For this reason, it is conceivable that a filter having a color corresponding to the color of the mark is provided in the image pickup apparatus, and the image of the mark is erased to obtain only an image such as a production date or a product number. However, in such a print inspection apparatus, an image of a mark using ink that is not affected by a change in temperature can be erased, but a mark using ink that changes color due to a change in temperature can be erased by an environmental temperature. Since the color changes, it is difficult to erase the image of the mark.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a partial image of a predetermined area from an image obtained by imaging a plurality of characters printed on an object to be printed. From the image of the character included in the image from which the partial image has been erased, by selecting a character image to be subjected to pass / fail judgment, or a character image whose matching degree is equal to or less than the threshold. counting the number, Ma its count value reaches a predetermined
If the number of characters superimposed on the mark is equal to or greater than the maximum number of characters, the printing state is determined to be defective, and if the count value is equal to or less than the maximum number of characters, the printing state is determined to be good. It is an object of the present invention to provide a print inspection apparatus capable of inspecting a print state with high accuracy even when a mark using ink whose color changes due to a change is provided.

[0008]

According to a first aspect of the present invention, there is provided a print inspection apparatus configured to capture an image of a printed portion of a printing object on which a plurality of characters are printed, Cutting means for individually cutting out the image of each character from the obtained image, and judging means for judging the quality of the printing state based on the result of comparing the pattern of the cut out image of each character with a preset standard pattern And a means for erasing a partial image of a predetermined area from the image, and selecting a character image to be subjected to pass / fail judgment from the image of the character included in the image from which the partial image has been erased. Means.

FIG. 10 is an explanatory diagram for explaining an example of an image obtained by imaging a main part of a printing object. As shown in FIG. 10, an annular mark is provided concentrically with the center of the product on an object to be printed such as a can having a circular outline.
7.9.25 "and a plurality of characters of" Serial No. 970925011 "are printed in two upper and lower rows so as to intersect with the mark in a direction substantially in the diameter of the product from a position separated from the edge of the product by a predetermined distance. I have.

In such a case, the relative position between the outline of the print object, the mark, and each printed character does not change regardless of the rotation of the print object. Therefore, the relative position between the contour of the print object and the area corresponding to the annular mark is set in advance, the image of the contour of the print object is specified in the image, and the mark is formed based on the specified image of the contour. The image of the mark is removed from the image by erasing the corresponding image area. From the image from which the mark image has been removed, a character image having a size equal to or greater than a predetermined threshold size is cut out, respectively, or, of the character images cut out from the image from which the mark image has been removed, characters having a size greater than or equal to the threshold size Select an image. As a result, it is possible to prevent the quality of a character image partially overlapping the mark image from being determined, and to avoid erroneous determination of the printing state.

If the degree of coincidence between the character image pattern selected in this way and the preset standard pattern is equal to or greater than a predetermined value, it is determined that the printing state is good, and if the coincidence is less than the predetermined value. If the degree exists, it is determined that printing is defective.

When printing a plurality of characters on each print object by ejecting ink onto the print objects while transporting a plurality of print objects in one direction, character distortion in which characters are printed obliquely. , Printing defects such as ink dripping from each character or streaks that cause lines to enter characters occur. If such printing defects occur only in one of a plurality of characters included in a character string, Almost no printing failure occurs for each character. Therefore, as described above, by removing the characters overlapping the mark, erroneous detection of a printing failure relating to the character printed on the printing object on which the mark using any kind of ink is applied can be prevented, and highly accurate. The printing condition can be inspected.

[0013] The print inspection apparatus according to the second aspect of the present invention has a predetermined mark.
An imaging device configured to capture an image of a printed portion of a printing object on which a mark and a plurality of characters are printed, and separately cut out an image of each character from an image obtained by imaging the imaging device. Means, means for calculating the degree of coincidence between the pattern of the image of each character cut out and the preset standard pattern, and printing based on a result of comparing each degree of coincidence obtained by calculation with a preset threshold value A print inspecting apparatus comprising: a determination unit configured to determine whether the state is good or bad, wherein the determination unit counts the number of character images whose coincidence is equal to or less than a threshold value, the count value, and the plurality of characters. Superimposed on the predetermined mark in
Means for comparing the maximum number of characters to be performed, and means for judging that the printing state is bad when the former is equal to or greater than the latter, and judging that the printing state is good when the former is equal to or less than the latter. It is characterized by the following.

FIG. 11 is an explanatory diagram for explaining another example of an image obtained by imaging the main part of the printing object. As shown in FIG. 11, a circular mark is formed on a print target such as a can having a circular contour so that the center of the mark is eccentric from the center of the print target, and the "expiration date 1997.7.9.25" and A plurality of characters of "manufacturing number 970925011" are printed in upper and lower two stages in a substantially diametric direction of the printing object from a position separated by a predetermined distance from the edge of the printing object. And in this example,
"Taste expiration date" of a plurality of characters included in the upper character string and "suffix number" of a plurality of characters included in the lower character string
And the mark overlap.

As described above, a plurality of printing objects having marks of appropriate shapes at appropriate positions are transported to the position of the printing device by the transport device, and a plurality of characters are printed on each printing object by the printing device. In this case, the direction in which the object is placed on the transport device is different for each object to be printed, and since each object to be printed rotates while being transported by the transport device, the relative position between the character and the mark printed on each object to be printed is Are different.

In the second invention, the maximum number of characters in which a plurality of characters included in each character string can overlap the mark is set in advance. For each character string, the degree of coincidence of each of the images of the plurality of characters cut out from the character string is calculated, and each degree of coincidence is compared with a preset threshold. Count the number. If the counted value is equal to or less than the maximum number of characters, it is determined that the printing state is good because it is determined that the degree of coincidence is low because the character overlaps the mark. On the other hand, if the counted value exceeds the maximum number of characters, it is determined that there is a character with a low degree of coincidence even though it does not overlap with the mark, and the printing state is defective. This makes it possible to inspect the printing state of the characters printed on the printing object having the mark of the appropriate shape at the appropriate position with high accuracy.

[0017]

Embodiments of the present invention will be specifically described below with reference to the drawings. (Embodiment 1) FIGS. 4 and 5 are a side view and a plan view showing a case where a print inspection apparatus according to the present invention is applied to a defective printing product elimination system. FIG. It is a block diagram which shows a system. On the conveyor 1 supported by a plurality of legs erected on the moving table 33,
A plurality of cans C, C,... Are sequentially placed with their bottoms facing upward, and each can C, C,. The belt-shaped guides 31, 31 are provided in parallel to each other at a distance corresponding to the diameter of the cans C, C,.
The cans C, C,... Are conveyed in a line by 31.

In the transport area of the cans C, C,..., The printing nozzle head 5 provided in the printing device 4 is moved up and down by the support member 35 so as to face the bottom of the can C transported by the conveyor 1. A pair of first photoelectric sensors 21 for detecting the presence / absence of the can C are provided at a predetermined distance upstream of the print nozzle head 5 so as to be freely supported. The detection signals of the first photoelectric sensors 21 and 21 are provided to a printing device main body 6 in which characters to be printed are set in advance,
After a predetermined time elapses according to the conveyance speed of the conveyor 1 after the detection signal is given, the printing apparatus main body 6 ejects ink from the printing nozzle head 5 to print predetermined characters on the bottom of the can C. .

On the support member 35, an image pickup device 8 provided in the print inspection device 7 is supported on the downstream side of the print nozzle head 5, and the image pickup device 8 includes a can C printed by the print nozzle head 5. Of the bottom of the image. The imaging device 8 includes a video camera and a strobe. The second photoelectric sensors 22 and 22 are disposed slightly downstream of the imaging center of the video camera of the conveyor 1, and the second photoelectric sensors 22 and 22
When the end of is detected, the strobe of the imaging device 8 operates,
The bottom of the can C is imaged by a video camera, and the obtained image is provided to a print inspection apparatus main body 9 for inspecting a print state.

Downstream of the image pickup device 8 on one side of the conveyor 1 by a predetermined distance (buffer zone), an exclusion cylinder 11 for reciprocating the pusher 12 is moved in the reciprocating direction of the pusher 12 in the transport direction of the cans C, C,. , And a pusher 12 is disposed so as to abut the peripheral surface of the cans C, C,..., And a little downstream from the rejection cylinder 11 on the other side of the conveyor 1 by the pusher 12. A discharge path 38 for discharging the pressed can C from the conveyor 1 is provided. A third photoelectric sensor 23, 23 is provided slightly upstream of the exclusion cylinder 11 of the conveyor 1, and a detection signal of cans C, C,... By the third photoelectric sensor 23, 23 is given to the exclusion control unit 10. Fourth photoelectric sensors 24, 24 are provided on both side edges of the entrance of the discharge passage 38, and the fourth photoelectric sensors 24, 24 enable the pusher
The discharge of the can C into the discharge path 38 by the device 12 is detected and confirmed.

FIG. 1 is a block diagram showing the configuration of a print inspection apparatus according to the present invention, and FIGS. 2 and 3 are flowcharts showing a print inspection procedure by the print inspection apparatus shown in FIG. In this embodiment, the state of printing on the cans C, C,... Marked with the marks as shown in FIG. 10 is inspected. The imaging device 8 converts an image signal obtained by imaging the bottom of the can C as described above into analog / digital (A /
D) The signal is supplied to the converter 18, and the A / D converter 18 converts the supplied image signal into a digital signal of a predetermined gradation, supplies the converted signal to the image memory 92 of the print inspection apparatus main body 9, and stores it therein (step S1). ~ S3).

When the image of the bottom of the can C is stored in the image memory 92, the CPU 91 activates the binarizing section 94 and activates the binarizing section 94.
Is to binarize the image of the bottom of the can C stored in the image memory 92 according to a preset threshold value (step S
4) Generate a binarized image and give it to the partial image erasing unit 95. In the partial image erasing section 95, a relative position between the contour of the bottom of the can C and the mark area, and an erasing area corresponding to the mark area are set in advance. The partial image erasing unit 95
A binarized image of the outline of the bottom of the can C is specified in the binarized image (step S5), and based on the binarized image of the specified outline and the relative position, the binarized image of the erasure area corresponding to the mark area is determined. The erased image is erased (step S6), and the binarized image after the erase is provided to the step cutout unit 96 that extracts a character string from the image.

When the binarized image subjected to the erasing process is given from the partial image erasing unit 95, the column cutout unit 96 specifies each character string including a plurality of characters, and converts the specified character string into one from the image. A character extracting unit that extracts characters one by one from each character string (steps S7 and S8).
Give to 97. The character cutout unit 97 has a predetermined character width for cutting out characters, and the character cutout unit 97 specifies each character included in the character string each time a character string is given from the column cutout unit 96, It is determined whether or not the width of the specified character is equal to or greater than the character width, and the operation of cutting out only such characters one by one (Steps S9, S10, S11) is repeated, and the binarized image of the plurality of cut out characters is repeated. To the filter unit 98. The filter unit 98 expands a plurality of dots constituting each of the given characters (step S12), combines the dots, and provides the character in which the dots are combined to the matching degree calculation unit 99.

The print inspection apparatus main body 9 is provided with a dictionary 93 in which a plurality of reference character patterns are registered. The matching degree calculation unit 99 calculates the degree of matching between the pattern of each character provided from the filter unit 98 and the corresponding reference character pattern in the dictionary 93 by a pattern matching method (step S13). Each of the obtained coincidences is given to a judgment unit 100 for judging the quality of the printing state.

A threshold for determining whether the printing state is good or bad is set in the determining unit 100 in advance. The determining unit 100 compares each degree of coincidence with the threshold (step S14), and determines a match that is lower than the threshold. If there is a degree, it is a serious defect to be excluded (step S17), and if all the coincidences are higher than the threshold, it is determined to be good (step S16), and the determination result is output to the output unit 102 and described later. This is given to the judgment result inspection unit 103. The output unit 102 provides the exclusion control unit 10 with a determination end signal, which is a pulse of a predetermined length, every time a determination result is provided from the determination unit 100. If the determination result is a serious failure, the output unit 102 is slightly faster than the determination end signal. At the timing, a rejection signal of a pulse shorter than the determination end signal is given to the rejection control unit 10 (step S18).

The judgment result inspection unit 103 includes a judgment unit 100
Is stored (step S19), and it is determined whether or not the stored determination results are continuously serious defects (step S20). If so, a stop signal is sent to the operation control unit 3. Then, the operation of the conveyor 1 is stopped (step S21).

The exclusion control unit 10 determines whether or not an exclusion signal has been provided prior to the determination signal each time a determination end signal is provided from the print inspection apparatus main body 9. While generating a non-operation command that does not operate the pusher 12 and storing it, when an exclusion signal is given, it generates an operation command to operate the pusher 12 and stores it, and also stores the stored operation command or non-operation. The command is tracked in accordance with the transport of the cans C, C,... In the buffer zone.

When the detection signal of the can C located immediately before the position of the pusher 12 is given from the third photoelectric sensors 23, 23, the exclusion control unit 10 reads the corresponding command, and if it is a non-operation command. , And waits until a new detection signal is given from the third photoelectric sensor 23. On the other hand, the exclusion controller 10
When the read command is an operation command, the operation command is issued at a timing when the time required for the can C to be conveyed to the center of the pusher 12 has elapsed after the detection signal is given from the third photoelectric sensor 23, 23. Give to the exclusion cylinder 11 and
From the conveyor 1 to the discharge path 38,
Eliminate cans C with poor printing.

(Embodiment 2) FIG. 7 is a block diagram showing Embodiment 2, and FIGS. 8 and 9 are flowcharts showing an inspection procedure by the print inspection apparatus main body shown in FIG. In the present embodiment, as shown in FIG. 11, a mark of an appropriate shape can be applied to the bottom of the can, with the center or the center of gravity of the mark being decentered from the center of the bottom of the can. It has been done. In the figure, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

The image of the bottom of the can C is stored in the image memory 92 in the same manner as before (steps S31 to S33).
94 binarizes the image of the bottom of the can C stored in the image memory 92 according to a preset threshold value (step S
34) to generate a binarized image and give it to the step segmentation unit 96. The column cutout unit 96 cuts out a plurality of character strings from the binarized image one by one (steps S35 and S36), and supplies them to the character cutout unit 97. Each time a character string is provided from the column cutout unit 96, the character cutout unit 97 cuts out a plurality of characters included in the character string one by one (steps S37 and S38), and supplies them to the filter unit 98.

The filter section 98 expands a plurality of dots constituting each given character (step S39) to combine the dots, and determines the character in which the dots are combined to obtain a matching degree calculation section.
The matching degree calculation unit 99 calculates the matching degree between each character pattern provided from the filter unit 98 and the corresponding reference character pattern in the dictionary 93 by a pattern matching method (step S40). Is given to the determination unit 101.

The determination unit 101 includes a threshold value for determining the quality of the printing state, the number of characters included in each character string, and a threshold value applied to the bottom of the can C among a plurality of characters included in each character string. The maximum number of characters that can overlap the marked mark is set in advance. The determination unit 101 compares the degree of coincidence of a plurality of characters included in each character string with a threshold value (step S41), and counts the number of characters whose degree of coincidence is equal to or greater than the threshold value (step S42). The determination unit 101 compares the number of characters obtained by the counting with the number of characters included in the character string (step S43),
If they are the same, in other words, they overlap the mark
If it is determined that there are no characters to be printed , it is determined that the printing state is good (step S46).

On the other hand, when the former is smaller than the latter, the determining unit 101 counts the number of characters whose matching degree is less than the threshold (step S44), and compares the obtained number of characters with the above-mentioned maximum number of characters (step S44). Step S45). When the number of characters whose matching degree is less than the threshold is equal to or less than the maximum number of characters, in other words, the character overlapping the mark is set in advance.
If it is determined that the number of characters is less than the maximum number of characters, the printing state is determined to be good (step S46). If the number of characters whose matching degree is less than the threshold exceeds the maximum number of characters,
In other words, the character that overlaps the mark is set in advance.
If it is determined that the number is larger than the maximum number of characters, the printing state is determined to be defective (step S47). Then, the determination unit 101 outputs the determination result to the output unit 102 and the determination result inspection unit.
Give to 103.

The output unit 102 sends a judgment end signal, which is a pulse of a predetermined length, to the exclusion control unit 10 each time a judgment result is given from the judgment unit 101. At a slightly faster timing, an exclusion signal of a pulse shorter than the determination end signal is given to the exclusion controller 10 (step S48). The judgment result inspection unit 103 judges whether the judgment result of the heavy defect is continuously given from the judgment unit 100 (steps S49 and S50), and if so, sends a stop signal to the operation control unit 3. Then, the operation of the conveyor 1 is stopped (step S51).

[0035]

As described in detail above, in the printing inspection apparatus according to the first aspect of the present invention, by removing a character overlapping a mark, printing is performed on a printing object on which a mark using any kind of ink is applied. It is possible to prevent erroneous detection of a printing failure relating to the character thus set, and to inspect the printing state with high accuracy.

In the print inspection apparatus according to the second invention,
The present invention has an excellent effect such that the printing state of characters printed on a product having a mark of a suitable shape at a suitable position can be inspected with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a print inspection apparatus according to the present invention.

FIG. 2 is a flowchart showing a print inspection procedure by the print inspection apparatus shown in FIG.

FIG. 3 is a flowchart showing a print inspection procedure performed by the print inspection apparatus shown in FIG. 1;

FIG. 4 is a side view showing a case where the print inspection apparatus according to the present invention is applied to a defective print product elimination system.

FIG. 5 is a plan view showing a case where the print inspection apparatus according to the present invention is applied to a defective print product elimination system.

FIG. 6 is a block diagram showing a control system of the defective printing product elimination system.

FIG. 7 is a block diagram showing a second embodiment.

FIG. 8 is a flowchart showing an inspection procedure by the print inspection apparatus main body shown in FIG.

FIG. 9 is a flowchart illustrating an inspection procedure performed by the print inspection apparatus main body illustrated in FIG. 7;

FIG. 10 is an explanatory diagram illustrating an example of an image obtained by imaging a main part of a print target.

FIG. 11 is an explanatory diagram illustrating another example of an image obtained by imaging a main part of a print target.

[Description of Signs] 8 Imaging device 9 Print inspection device main body 92 Image memory 95 Partial image erasing unit 96 Step cutout unit 97 Character cutout unit 99 Matching degree calculation unit 100 Judgment unit C can

Continued on the front page (72) Inventor Masayuki Hase 1-7-131 Nagara Nishi, Kita-ku, Osaka-shi, Osaka Hitachi Nishi Service Engineering Co., Ltd. Inside Osaka Service Station (72) Inventor Sumi Ishikawa Sachi-cho, Hitachi-shi, Ibaraki JP-A-9-131951 (JP, A) JP-A-9-95028 (JP, A) JP-A-6-83943 (JP, A) Kaihei 4-3722084 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G06T 1/00 310 G06K 9/03 JICST file (JOIS)

Claims (2)

(57) [Claims] An image pickup device configured to image a printed portion of a print target on which a plurality of characters are printed, and an image of each character is separately obtained from an image obtained by the image pickup device. In a print inspection apparatus, comprising: a cutout unit that cuts out, and a judgment unit that determines whether a printing state is good or not based on a result of comparing a pattern of an image of each cutout character and a preset standard pattern, Means for erasing the partial image of the area, and a character image included in the image from which the partial image has been erased,
Means for selecting a character image to be subjected to pass / fail determination. 2. An image pickup device for picking up an image of a printed portion of a printing object on which a predetermined mark and a plurality of characters are printed, and each character from an image obtained by the image pickup device. Means for individually cutting out the image of each character, means for calculating the degree of coincidence between the pattern of the image of each character cut out and the preset standard pattern, and comparing each degree of coincidence obtained by calculation with a preset threshold value A determination unit that determines whether the printing state is good or bad based on the result, wherein the determination unit counts the number of character images whose degree of coincidence is equal to or less than a threshold, and the count value. , Of the plurality of characters
Means for comparing the maximum number of characters to be superimposed with the predetermined mark in the above, and if the former is equal to or greater than the latter, the printing state is determined to be defective, and if the former is equal to or less than the latter, the printing state is good. A print inspection device comprising: