JP2018163421A - Segmenting method of printing character and printing inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a segmenting method of printing characters capable of conducting a setting work to be conducted prior to printing inspection in a short period of time and further inspecting printing with high accuracy by absorbing variation due to persons in charge.SOLUTION: When segmenting characters being an object of printing inspection from an image obtained by imaging characters composed of dot patterns, before a coupling process and a noise cut process, characters estimated to be maximum and minimum among a series of print characters in the imaged image are selected, the selected characters are encircled with a rectangular bounding box in which the dots are inscribed, and parameters necessary for the coupling precess and noise cut process are calculated according to a previously prepared formula by using lateral and longitudinal dimensions of the two bounding boxes.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a method for cutting out a target printed character from a photographed image in inspection of characters printed on a product or a packaging container, and a print inspection apparatus adopting the method, and more particularly to a character printed with a dot pattern. The present invention relates to a cutting method and a print inspection apparatus.

  In order to manage the date of manufacture, production lot, expiration date (expiration date, expiry date), etc. at the production site of food and medicine, such information is stored in products or packaging containers using a printing device such as an inkjet printer. Printed.

  In the printing device described above, in order to check whether printing is performed correctly, characters printed on products and packing containers are photographed with a camera, and the obtained printed image is collated with a registered template image. Thus, the suitability of printing is determined (see, for example, Patent Document 1).

  In the same inspection, it is necessary to cut out a print character from a photographed image as a pre-process for comparing a dot pattern print image with a template image. In the cut-out of the print character, each process of dot connection and noise cut is performed. Is called.

  Here, dot linking is a process of virtually linking adjacent dots to extract a group of dots that are considered as one character. Only those in which the vertical and horizontal sizes of the subsequent dot group are equal to or smaller than a predetermined value are the targets of the print inspection.

  On the other hand, the noise cut is a process of excluding, as noise, a group of dots whose vertical and horizontal sizes are out of a predetermined range from a group of dots regarded as one character after the connection process. .

  The print character cut out by the cut-out process described above is checked against the template image to determine whether the print character is appropriate.

JP, 2006-186766, A

  Conventionally, parameters (threshold values) are set according to the number of pixels in the concatenation process and the noise cut process. For example, in an image with a VGA resolution (640 pixels × 480 pixels), the minimum interval in the vertical direction is 3 in the concatenation process. The maximum interval is set to about 60 pixels.

  However, since the size of the printed character varies depending on the distance from the camera to the product, etc., the method of setting the parameter with the number of pixels always keeps the distance between the camera and the product constant or the size of the character image. Accordingly, it is necessary to change the parameter accordingly, which hinders the efficiency of the setting work performed prior to the print inspection.

  Even if the distance between the camera and the product can be kept constant, the person in charge causes variations in parameters, which causes a decrease in the accuracy of the print inspection.

  The present invention has been made in view of such a situation, and can complete a setting operation prior to a print inspection in a short time, and can also inspect a print with high accuracy by absorbing variations by a person in charge. An object of the present invention is to provide a printing character cutting method and a printing inspection apparatus.

In order to achieve the above object, a method for cutting out printed characters according to the present invention includes:
A concatenation process for extracting a group of dots regarded as one character by virtually concatenating adjacent dots from an image obtained by photographing a character consisting of a dot pattern;
A noise cut process for removing a dot group regarded as noise from a dot group regarded as one character by the connection process,
A cutout method of a print character for cutting out a character to be subjected to print inspection from the photographed image,
Prior to the concatenation process and the noise cut process, a character that is estimated to be the maximum and minimum among a series of print characters in the photographed image is selected, and the selected character is bounded by a rectangular bounding box with a dot inscribed therein Surrounded by
Using the vertical and horizontal dimensions of the two bounding boxes, parameters necessary for the connection process and the noise cut process are calculated according to a calculation formula prepared in advance.

  Here, it is preferable that the calculation formula for calculating the parameter varies depending on the dot pattern printing method to be employed and the number of dots constituting the character.

  In the connection process, dots adjacent to each other in which the distance between the dots in the vertical direction and the horizontal direction is equal to or less than a predetermined value are extracted to extract a dot group regarded as one character, and It is preferable to exclude those in which the sizes of the virtually connected dot groups in the vertical and horizontal directions exceed a predetermined value from the inspection target.

  Further, in the noise cut process, among the dot groups regarded as one character by the connection process, a dot group whose vertical and horizontal sizes are out of a predetermined range is regarded as noise and excluded from the inspection target. Is preferred.

  Furthermore, it is preferable to set an area for performing the connection process and the noise cut process in the captured image prior to the connection process and the noise cut process.

Moreover, the print inspection apparatus according to the present invention is a print inspection apparatus that realizes the print character cutting method described in any of the above,
An interface that captures printed images taken with the camera;
A storage unit for storing images captured by the interface;
An input / display unit for inputting data necessary for the print inspection and displaying the print image and the result of the print inspection;
A print inspection processing unit that cuts out a print character to be inspected from the image stored in the storage unit and compares the print character with a template image prepared in advance to determine whether print quality is appropriate or not. It is characterized by that.

  According to the method for cutting out printed characters according to the present invention, since it is not necessary to consider the distance between the product and the camera, the setting operation can be completed in a short time, and parameter variations by the person in charge can be achieved. The accuracy of the print inspection can be maintained at a high value.

It is the schematic which shows the example of installation of the printing inspection apparatus concerning embodiment of this invention. It is a block diagram which shows the structure of the printing inspection apparatus concerning embodiment of this invention. It is a flowchart which shows the procedure of a printing test | inspection. It is a figure which shows an example of the binarized print character and the cut out print character. It is a figure explaining a connection process. It is a figure explaining a noise cut process. It is a flowchart which shows the flow of the setting operation | work performed before a printing test | inspection. It is explanatory drawing (the 1) of the process which surrounds a printing character with a bounding box. It is explanatory drawing (the 2) of the process which surrounds a printing character with a bounding box.

  Hereinafter, a method for cutting out printed characters and a printed inspection apparatus according to embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not construed as being limited to the description of the embodiments. Various modifications can be made without departing from the spirit and scope of the present invention.

<Installation example of print inspection device>
FIG. 1 shows an installation example of a print inspection apparatus according to the present embodiment. The printing inspection apparatus 1 is installed adjacent to a conveyor 3 that conveys containers 4 packed with products, and prints the date of manufacture, lot number, and the like on the side of the packaging container 4 on the upstream side of the conveyor 3. An ink jet printer 2 is installed. In the figure, the camera installation structure which is not related to the print inspection is described in a simplified manner.

  First, the inkjet printer 2 will be described. The inkjet printer 2 includes a photoelectric sensor 20, a controller 21, and a print head 22.

  Ink jet printers are roughly classified into a continuous type and an on-demand type. In this embodiment, a continuous type ink jet printer is employed. The continuous ink jet printer ejects ink from a nozzle provided on the print head 22 by a pump, charges the ink droplet at a position where the ejected ink is separated into ink droplets, and further tracks the ink droplet charged by the deflection electrode. Is bent to collide with a predetermined position on the print surface to form ink dots.

  By forming ink dots continuously on the side surface of the packing container 4 with reference to the time when the light output from the photoelectric sensor 20 is blocked by the packing container 4 conveyed by the conveyor 2, FIG. As shown in FIG. 4, a character having a dot pattern is formed.

  The controller 21 is equipped with a touch panel display, and the operator instructs the contents of printing by touching the touch surface of the display. The ink is supplied from the ink tank built in the controller 21 to the print head 22 via a pipe, and the ink collected by the gutter is transferred to the ink tank and reused.

  Next, the print inspection apparatus 1 will be described. The print inspection apparatus 1 installed on the downstream side of the conveyor 3 includes a photoelectric sensor 10, a controller 11, a camera 12, and a lighting fixture 13. The camera 12 and the lighting fixture 13 are integrated by a metal fitting.

  The photoelectric sensor 10 is installed on the edge of the conveyor 3, and the camera 12 is activated after a predetermined time from when the packing container 4 blocks the light output from the photoelectric sensor 10, and is printed on the side surface of the packing device 4. Take a picture of the letters. The luminaire 13 is used to illuminate the photographing surface brightly during photographing.

  FIG. 2 shows the configuration of the controller 11. The controller 11 includes a control unit 14, an interface 15, an input / display unit 16, a storage unit 17, a print inspection processing unit 18, and a hard disk drive (hereinafter referred to as “HDD”) 19.

  The controller 11 includes a CPU and a RAM in the same manner as a general personal computer in terms of hardware, and the functions of the control unit 14, interface 15, and print inspection processing unit 18 are stored in programs stored in the HDD 19. This is realized by reading and executing by a microprocessor.

  The control unit 14 controls the operation of each unit of the camera 12 and the controller 11 as indicated by broken lines. An image photographed by the camera 12 is taken into the controller 11 via the interface 15.

  The input / display unit 16 is configured by a touch panel display, and is used by an operator to input data necessary for the print inspection. Further, the input / display unit 16 displays an image photographed by the camera 12 and displays a result of the print inspection. Used for.

  The storage unit 17 is composed of a RAM, temporarily stores image data taken by the camera 12, and then transfers it to the HDD 19 as necessary. Conversely, image data read from the HDD 19 and data necessary for executing inspection are temporarily stored and transferred to the print inspection processing unit 18 or the like.

  As listed in the block, the print inspection processing unit 18 performs processing necessary for print inspection and setting work, specifically, parameter setting, binarization, character segmentation, similarity calculation, and print adequacy determination. Perform each process. The contents of these processes will be described in detail later with reference to the drawings.

<Print inspection procedure>
Next, with reference to FIG. 1 and FIG. 2 and the flowchart of FIG.

  First, the operator operates the input / display unit 16 of the controller 11 to photograph a character image printed on the side surface of the packaging container 4 conveyed on the conveyor 3 (step S11). As described above, since the shutter of the camera 12 is released after a lapse of a predetermined time after the packaging container 4 blocks the light of the photoelectric sensor 10, the print image is always displayed at the same position on the screen.

  The image data photographed by the camera 12 is transferred to the print inspection processing unit 18 via the interface 15 and the storage unit 16, where binarization processing is performed (step S12). The binarization process is a process for converting a gradation image captured by the camera 12 into a black and white image that can be processed by the CPU, and a threshold value is set according to the brightness of the image.

  FIG. 4A shows an example of binarized print characters. In the following description, the size of the print image is represented by the number of pixels. For example, a VGA resolution screen is composed of 480 × 640 pixels.

  Subsequently, characters are cut out from the binarized print characters (step S13). As described above, cutting out characters from a captured image is a process of cutting out a print character to be inspected by dot connection processing and noise cut processing. The connection process and the noise cut process will be described with reference to FIGS.

  FIG. 5 is an image obtained by photographing the number “1” printed by the dot pattern with the camera 12. Prior to the connection process, the print inspection processing unit 18 creates data indicating the position and shape of dots in the image based on the binarized image, and the connection process is performed based on the data.

  In the connection process, when the distance h1 between the vertical dots is equal to or less than a predetermined value (for example, h1 ≦ 3 pixels), the two dots are virtually surrounded by a rectangular frame, Continue from the first dot to the bottom dot.

  Similar processing is performed in the horizontal direction. When the distance w1 between the dots in the horizontal direction is equal to or less than a predetermined value (for example, w1 ≦ 2 pixels), the two dots are virtually surrounded by a rectangular frame, and the work is performed from the left dot to the right dot. Continue until.

  At this time, when the height h2 of the rectangular frame surrounding the dot exceeds a predetermined value (for example, 60 pixels), the operation of surrounding the dot with the rectangular frame is stopped. Similarly, when the width w2 of the rectangular frame surrounding the dot exceeds a predetermined value (for example, 30 pixels), the operation of surrounding the dot with the frame is stopped.

  Finally, a dot group in which a plurality of dots are virtually connected and surrounded by a rectangular frame is generated.

  Next, the noise cut processing will be described with reference to FIG. In the printing formed by the dot pattern, there are a character in which the dots are separated as shown in FIG. 5 and a character in which the dots are connected as shown in FIG. Here, a noise cut process performed for printing in which dots are connected will be described. The connection process is also performed for such characters. In this case, the connected dot group is surrounded by a rectangular frame F as shown in FIG.

In the noise cut processing, the height h3 and width w3 of the rectangular frame F formed by the concatenation processing are within a predetermined range (for example, h3 _max = 65 pixels, h3 _min = 5 pixels, w3 _max = A dot group deviating from (35 pixels, w3 _min = 5 pixels) is excluded from the inspection target as noise rather than printing. Here, h3 _max and h3 _min are the height of the upper limit and lower limit frames, and w3 _max and w3 _min are the upper and lower limit frame widths.

In the example shown in FIG. 6, the characters shown in (a) are h3 _max >h3a> h3 _min and w3 _max >w3a> w3 _min . On the other hand, the characters shown in (b) are excluded from the inspection target as noise because h3b ≧ h3 _max and w3b ≧ w3 _max . The characters shown in (c) are excluded from the inspection target as noise because h3c ≦ h3 _min and w3c ≦ w3 _min .

  Return to the description of the flowchart. FIG. 4B shows a print character after the connection process and the noise cut process are completed. As shown in the figure, all printed characters to be inspected are surrounded by a rectangular frame F, and all characters to be inspected for printing are cut out from the photographed image.

  Next, each character clipped in this way is compared with the template image of the corresponding character read from the HDD 19 to calculate the similarity, that is, how much the character is similar (step S14).

  Subsequently, the calculated similarity is compared with a reference similarity (for example, 80%) read from the HDD 19, and it is determined that a character with a higher similarity is appropriate and a character with a lower similarity is inappropriate (step S15). ).

  The above-described similarity calculation and suitability determination are performed for all the characters shown in FIG. 4B (Yes in step S16), and the determination result is displayed on the screen of the input / display unit 16. For example, by displaying a frame of characters determined to be appropriate in blue and displaying a frame of characters determined to be inappropriate in red, it is possible to easily grasp whether there is an inappropriate character.

<Print inspection setting work>
In the above-described print inspection, the procedure for continuously inspecting the packaging containers 4 conveyed by the conveyor 3 has been described, but there is an operation that must be performed prior to the print inspection. Hereinafter, this work is referred to as “setting work”. FIG. 7 shows the flow of setting work.

  First, the same state as when the characters printed on the side surface of the packing container 4 conveyed by the conveyor 3 is inspected is reproduced with the conveyor 3 being stationary. That is, the packaging container 4 mounted on the conveyor 3 as a sample is set at the same position as when the camera 12 is used for inspection, and then is captured using the camera 12 (step S21).

  On the screen of the input / display unit 16 of the controller 11, characters printed on the side surface of the packaging container 4 are displayed at the same position as when the packaging container 4 is being conveyed by the conveyor 3. FIG. 8A shows a print image displayed on the screen of the input / display unit 16.

  In this state, the operator operates the input / display unit 16 to set the inspection character string (step S22). Specifically, a character string to be inspected is registered. In the example shown in FIG. 8A, numbers, periods, and slashes are registered in the order shown in the figure. The inspection character string is set in order to finish the processing in a short time by limiting the inspection target.

  Next, as shown in FIG. 8B, when the operator touches the screen of the input / display unit 16 with a touch pen or a finger, the printed character displayed on the screen is surrounded by a frame (step F23).

  The reason why the character to be inspected is surrounded by a frame is to reduce the time when the character to be inspected is cut out from the screen, and is included in the region A surrounded by the frame in the cutting process. Only the dots are connected and noise cut.

  Next, the operator touches the screen of the input / display unit 16 with a touch pen or the like, and surrounds the characters estimated to be the maximum and the minimum among the printed characters with a bounding box. FIG. 8C shows a state in which the maximum estimated character “2” is surrounded by the bounding box B. FIG. 8D shows a state where the character “.” Estimated to be the minimum is surrounded by a bounding box B.

  FIG. 9 is an enlarged view of a part of FIG. The bounding box B is a rectangular GUI tool used to enclose characters and figures displayed on the screen. The bounding box B is moved in a state where the touch pen or the like is in contact with the rectangular handles B2 arranged on the top, bottom, left and right of the box B1. Thus, the height and width of the box B1 can be easily changed. As shown in FIGS. 8C and 8D, the operator adjusts the dots so as to be inscribed in the upper, lower, left and right frames of the box B1 while moving the touch pen or the like.

  The reason why the character to be inspected is surrounded by the bounding box B will be described. In the connection process and the noise cut process described with reference to FIGS. 5 and 6, the parameter (threshold value) is set according to the number of pixels. As described above, when the parameter is set by the number of pixels, it is necessary to keep the distance between the inspection object and the camera constant, so that the efficiency of the inspection is reduced, and further, there is a problem that the operator varies. is there.

  Therefore, in the present invention, the parameters necessary for the connection process and the noise cut process are automatically calculated by using the vertical and horizontal dimensions of the bounding box surrounding the maximum character and the minimum character and a calculation formula prepared in advance. Yes.

When printing a character by the dot pattern, vertical, horizontal dots D _h, D _w, vertical dimension H _L of the bounding box surrounding the maximum character, lateral dimension W _L, vertical bounding box enclosing the smallest character Assuming that the dimension is H _S and the horizontal dimension W _S , the above-described parameters are calculated by the following equations.

That is, the parameters h1, h2, w1, and w2 necessary for the above-described connection process are
h1 = H _L / D _h
h2 = H _L + H _L / D _h
w1 = W _L / D _w
w2 = W _L + W _L / D _w

On the other hand, parameters h3 _min , h3 _max , w3 _min , w3 _max necessary for noise cut processing are
h3 _min = 0.8 × H _S
h3 _max = 0.8 × H _S + H _L
w3 _min = 0.8 × W _S
w3 _max = 0.8 × W _S + W _L

  In calculating the parameters, the operator need only surround the prints estimated as the maximum and minimum characters with a bounding box. The parameters required for the concatenation process and noise cut process are automatically calculated based on the bounding box dimension data, greatly reducing the time required for setting work and eliminating variations due to personal factors. The quality of print inspection is increased.

  It should be noted that the operation of surrounding the print with the bounding box is not necessarily strict, and even if there is a slight gap between the frame and the dot, the calculation of the parameter is hardly affected.

  In the above formula, the coefficient of the calculation formula is set to 1 in the concatenation process and the coefficient is set to 0.8 in the noise cut process, but for this value, an optimum value may be determined by repeated trials.

  Further, in the present embodiment, a CIJ (Continuous Ink Jet) method is employed as a method for printing characters using a dot pattern. Since the above calculation formula changes depending on the printing method employed and the number of dots constituting the character, when a printing method such as DOD (Drop On Demand) or vector is adopted, the calculation formula is changed accordingly. There is a need.

  Returning to the description of FIG. 7, in order to convert the photographed gradation image into a monochrome image that can be processed by the controller, parameters necessary for binarization are set (step S25). Since the binarization method is generally widely known, a description thereof is omitted here.

  Next, a passing score is set (step S26). As described above, the suitability of the printed character is determined by calculating the similarity with the template image. For example, if the similarity is 80% or more, it is determined that the printing is appropriate. Therefore, it is necessary to set a passing score. The set passing score data is stored in the HDD 19 and read out to the storage unit 17 as necessary.

  Finally, the images used for the inspection from the template images stored in the HDD 19 in advance, in the example shown in FIG. 8, the template images “2” “0” “1” “7” “.” And “5” are read out. The data is temporarily stored in the storage unit 17.

  With the setting operation described above, preparation for inspecting the suitability of the characters printed on the packing containers 4 conveyed by the conveyor 3 is completed. Thereafter, if the conveyor 3 is driven to transport the packing container 4 and the ink jet printer 2 and the print inspection apparatus 1 are driven in accordance with this, the printing on the packing container 4 and the print inspection are continuously performed. Suitability is determined.

  As described above, when the method for cutting out printed characters according to the present invention is used, the parameters necessary for the dot linking process and the noise cutting process are such that the operator encloses the printed characters displayed on the screen with a binding box. After that, it is automatically calculated using the vertical and horizontal dimensions of the box, so the work time required for setting can be greatly reduced. And the accuracy of the print inspection can be increased.

DESCRIPTION OF SYMBOLS 1 Print inspection apparatus 2 Inkjet printer 3 Conveyor 4 Packing container 10 Photoelectric sensor 11, 21 Controller 12 Camera 13 Lighting fixture 14 Control part 15 Interface 16 Input / display part 17 Storage part 18 Print inspection process part 19 HDD

Claims (6)

A concatenation process for extracting a group of dots regarded as one character by virtually concatenating adjacent dots from an image obtained by photographing a character consisting of a dot pattern;
A noise cut process for removing a dot group regarded as noise from a dot group regarded as one character by the connection process,
A cutout method of a print character for cutting out a character to be subjected to print inspection from the photographed image,
Prior to the concatenation process and the noise cut process, a character that is estimated to be the maximum and minimum among a series of print characters in the photographed image is selected, and the selected character is bounded by a rectangular bounding box with a dot inscribed therein Surrounded by
A printing character cutting method, characterized in that parameters necessary for the connection processing and noise cutting processing are calculated according to a calculation formula prepared in advance using vertical and horizontal dimensions of the two bounding boxes.   The printing character cutout method according to claim 1, wherein the calculation formula for calculating the parameter varies according to a dot pattern printing method to be employed and the number of dots constituting the character.   In the concatenation process, dots that are considered to be one character are extracted by virtually concatenating dots in which the distance between the dots in the vertical direction and the horizontal direction is equal to or smaller than a predetermined value among adjacent dots, and the virtual group The method for cutting out printed characters according to claim 1 or 2, wherein a group of dots connected in a vertical direction and a horizontal size exceeding a predetermined value is excluded from inspection targets.   In the noise cut processing, among the dot groups regarded as one character by the connection processing, a dot group whose vertical and horizontal sizes are out of a predetermined range is regarded as noise and excluded from the inspection target. Item 4. A method for cutting out printed characters according to any one of Items 1 to 3.   5. The method for cutting out printed characters according to claim 1, wherein an area for performing a connection process and a noise cut process is set in the captured image prior to the connection process and the noise cut process. A print inspection device that realizes the method for cutting out printed characters according to any one of claims 1 to 5,
An interface that captures printed images taken with the camera;
A storage unit for storing images captured by the interface;
An input / display unit for inputting data necessary for the print inspection and displaying the print image and the result of the print inspection;
A print inspection processing unit that cuts out a print character to be inspected from the image stored in the storage unit and compares the print character with a template image prepared in advance to determine whether print quality is appropriate or not. A printing inspection apparatus characterized by that.

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