Printed image inspection device and printed image inspection method

Abstract

To provide a printed image inspection device which can inspect color information based on an environmental change by various and simple inspection methods.SOLUTION: A printed image inspection device acquires color information of a dot part of an image from the image obtained by imaging a recognition object with a dot pattern arrayed, and outputs a determination result based on the color information. The printed image inspection device includes: an image input part which captures the image obtained by imaging the recognition object including the dot pattern; a dot pattern recognition part which determines conformity with a predetermined reference dot pattern; a color information acquisition part which acquires the color information from pixel data of the dot part of the image; a correlation calculation part which calculates a correlation between color information data and predetermined reference color information data of ink; and an ink state determination part which determines an ink state of the recognition object from the correlation of the correlation calculation part.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an image inspection apparatus and an image inspection method, and more particularly to a print image inspection apparatus and a print image inspection method for inspecting an image printed by an inkjet recording device. [Background technology]

[0002] 2. Description of the Related Art Continuous jet charge-controlled inkjet recording devices are used in a wide range of fields, including food and electronic components, to print expiration dates, use-by dates, serial numbers, and other information attached to products.

[0003] A typical continuous-jet charge-controlled ink-jet recording apparatus is provided with an ink container for storing ink in its main body, and the ink in the ink container is supplied to a print head by an ink supply pump.

[0004] Ink supplied to the print head is continuously ejected from the ink nozzles and turned into ink droplets. The ink droplets used for printing are charged and deflected before flying to the desired printing position on the print target to form characters and symbols, while the ink droplets not used for printing are not charged or deflected, but are collected in a gutter and returned to the ink container by an ink recovery pump.

[0005] Such continuous-jet charge-controlled inkjet recording devices have a high printing speed, making them suitable for use in mass-produced product production processes. However, because printing using a continuous-jet charge-controlled inkjet recording device has a high printing speed, it is also necessary to inspect the printing at high speed to see if it is being printed correctly. For this reason, a print inspection device is used to inspect whether the characters printed on the printing device, such as the expiration date, use-by date, and serial number, are printed according to the set data.

[0006] In printing with a continuous-jet charge-controlled inkjet recording device, ink droplets ejected from a nozzle form dots when they land on the object to be recognized (printing surface). These dots are arranged in a set pattern to form printed characters and symbols. In order to support high-speed printing, dot patterns are often formed by arranging minute dots discretely.

[0007] Print inspection devices are required to quickly inspect whether or not the characters printed with these dot patterns are normal. Print inspection devices capture images of recognition targets on which characters printed with dot patterns are arranged, and use image processing to determine whether or not each dot position is printed normally in the resulting image.

[0008] As an image processing method, for example, a method is used in which a judgment is made based on the degree of match between image data of a dot pattern that has previously formed a correctly printed character and image data of an actually printed dot pattern.For example, Japanese Patent Laid-Open Publication No. 2008-89379 (Patent Document 1) discloses a print inspection device that captures defective print as an image in advance by an imaging means, inspects whether or not the print target recognizes the print as defective, and records the inspection result.Furthermore, Japanese Patent Laid-Open Publication No. 2011-16261 (Patent Document 2) discloses a method for inspecting the accuracy of the landing position of ink droplets, which judges whether or not a deviation has occurred in the landing position of ink droplets of an inkjet printer. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2008-89379 A [Patent Document 2] JP 2011-16261 A Summary of the Invention [Problem to be solved by the invention]

[0010] In recent years, it has been proposed to give printing ink a function other than the purpose of printing (for example, the purpose of identifying characters) and to use it for quality control of mass-produced products. For example, it is possible to use functional ink to control whether a product has been adversely affected by heat in an environment over time. It is also possible to control whether a product has been adversely affected by ultraviolet rays over a long period of time.

[0011] Commonly used inks with this type of functionality are color-changing inks, such as thermochromic inks that change color in response to thermal history, and fluorescent inks that emit light when exposed to ultraviolet light. These functional inks change hue or tone in response to some kind of environmental change, so by identifying the hue or tone (hereinafter sometimes referred to as color information) of the ink printed on a product, it is possible to know whether the product has been adversely affected by heat or ultraviolet light (the effects of environmental changes).

[0012] Therefore, when printing using functional inks, it is necessary to inspect the color information of the dots in addition to the print inspection. In the case of functional inks, it is possible to determine whether the product has been exposed to some environmental change by the color information of the dots printed on the product.

[0013] While print inspection is often used in manufacturing processes as described above, inspection of color information based on environmental changes is particularly required in environments that change over time, such as distribution and consumption processes. Therefore, it is desirable to be able to perform inspection using diverse and simple inspection methods. However, Patent Document 1 and Patent Document 2 do not take such issues into consideration, much less disclose or suggest solutions to the issues.

[0014] An object of the present invention is to provide a print image inspection device and a print image inspection method that can inspect color information based on environmental changes using a variety of simple inspection techniques. [Means for solving the problem]

[0015] The present invention is a print image inspection device that acquires color information of the dot portions of an image from an image obtained by imaging a recognition target on which a dot pattern is arranged, and outputs a judgment result based on this color information, and is characterized by having an image input unit that takes in the image obtained by imaging a recognition target including a dot pattern, a dot pattern recognition unit that judges the match with a predetermined reference dot pattern, a color information acquisition unit that acquires color information from pixel data of the dot portions of the image, a correlation value calculation unit that calculates the correlation between the color information data and predetermined reference color information data for an ink, and an ink state judgment unit that judges the ink state of the recognition target from the correlation value of the correlation value calculation unit. Effect of the Invention

[0016] According to the present invention, color information based on environmental changes can be inspected by a variety of simple inspection methods. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of an inkjet recording apparatus. [Diagram 2] FIG. 2 is an explanatory diagram illustrating an article delivery route and a network of print image inspection devices and a management server along the route. [Diagram 3] 1 is a block diagram showing a configuration of a print image inspection device according to an embodiment of the present invention; [Figure 4] 4 is a flowchart illustrating a processing procedure of the print image inspection device shown in FIG. 3. [Figure 5A] FIG. 4 is an explanatory diagram illustrating a state of a printed dot pattern before heat is applied. [Figure 5B] FIG. 11 is an explanatory diagram illustrating the state of a printed dot pattern after heat is applied thereto. [Figure 6] FIG. 2 is an explanatory diagram illustrating a first recognition method of a dot pattern. [Figure 7] FIG. 11 is an explanatory diagram illustrating a second recognition method of a dot pattern. [Figure 8] FIG. 11 is an explanatory diagram illustrating a third method for recognizing a dot pattern. [Figure 9] FIG. 13 is an explanatory diagram illustrating a fourth recognition method of a dot pattern. [Figure 10] FIG. 11 is an explanatory diagram for explaining a method for inspecting the color of printed dots. [Figure 11] FIG. 11 is an explanatory diagram illustrating a state in which an actual print dot color inspection is performed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments, and various modifications and application examples within the technical concept of the present invention are also included in the scope of the present invention. First, the configuration and operation of a typical continuous-jet charge-control type ink jet recording apparatus will be briefly described. FIG. 1 shows a schematic configuration of an inkjet recording device. In FIG. 1, ink liquid 11 stored in an ink container 10 is pressurized by an ink supply pump 12 and supplied to an ink nozzle 13. By periodically applying a voltage to a piezoelectric element 14 installed in the ink nozzle 13, the ink in the ink nozzle 13 is excited. The excited ink is ejected from the ink nozzle 13 as an ink column 15 and then becomes ink droplets. Here, in this embodiment, a "thermochromic ink" is used as the functional ink. Thermochromic ink is ink whose color information changes depending on the influence of temperature.

[0019] The ink used for printing is charged into ink droplets by a charging electrode 16 at the same time as the ink is turned into droplets. The charged ink droplets 17 are deflected by an electric field generated in a deflection space between a positive deflection electrode 18 and a negative deflection electrode 19, and then land on a print target 20. Ink droplets 17 not used for printing are not charged and are not deflected, so they are collected in a gutter 21.

[0020] Products printed by such inkjet recording devices are delivered to customers via a distribution route as shown in FIG. 2, and this distribution route is managed by a quality control system.

[0021] The quality control system includes an inkjet recording device (IJP) that prints thermosensing ink, a print image inspection device (IMG) (here, a print inspection device (PID) and a smartphone (SMT)) that acquires print information of the dot pattern printed on the article and color information of the thermosensing ink, and a management server (MSV). The inkjet recording device (IJP), print inspection device (PID), smartphone (SMT), and management server (MSV) are connected to each other so as to be able to communicate with each other via a network (NET).

[0022] For example, if the item is a plastic beverage bottle, the distribution route would be the manufacturing plant that produces the plastic beverage bottles, the storage warehouse that stores the plastic bottles, the shipping area from which the plastic bottles are shipped, the transport vehicles that transport the plastic bottles, the stores that sell the plastic bottles (convenience stores, etc.), and the customers who purchase the plastic bottles.

[0023] Print information is sent from the manufacturing plant and shipping area to the management server (MSV) by the print inspection device (PID), and color information is sent from the store and customers to the management server (MSV) by smartphone (SMT). The management server (MSV) collects the management data such as the print information and color information sent. At each location, an operator uses a print image inspection device (print inspection device or smartphone) to collect quality control data.

[0024] The management server (MSV) manages the following information as files: (1) dot pattern recognition information, (2) ink status determination information, (3) product information, (4) production information, (5) reading information, (6) quality information, (7) distribution information, and (8) distribution management information.

[0025] By checking the color tone and hue of the thermochromic ink, the operator can visually check the temperature management status of each process and the temperature load status of the item. In addition to the operator's visual confirmation, numerical information can be obtained as color tone / hue.

[0026] Furthermore, during each process, such as shipping, transportation, and storage, the operator uses the print image inspection device (IMG) to send quality control information such as the optical condition of the PET bottle and its thermochromic ink, as well as images, the reading location, and time to the management server (MSV).

[0027] At the store, the operator can visually check the temperature control status and temperature load status during the process of transportation, etc. from the time of shipment from the manufacturing factory by checking the hue / tone of the thermochromic ink on the transported PET bottles. Furthermore, by connecting to the management server (MSV) via the print image inspection device (IMG), it is possible to check information such as quality control information up to the time of delivery of the PET bottles.

[0028] The print image inspection device (IMG) can determine whether or not quality is being maintained based on the color information of the thermochromic ink, and display the determination result on an output unit such as a liquid crystal screen. Therefore, the operator can easily check the result. Furthermore, the quality control data including the determination result is sent to the management server (MSV), and the management server (MSV) stores it as quality control information.

[0029] In this embodiment, the quality judgment as to whether or not the quality is maintained is processed on the print image inspection device (IMG) side. This is to distribute the concentration of calculation processing such as judgment processing in a system that targets a large number of items. It goes without saying that if the processing capacity of the management server (MCV) is high, the quality judgment may be executed on the management server (MSV) side.

[0030] Next, an image inspection method in the inkjet recording system according to the embodiment of the present invention will be described. Fig. 3 shows the configuration of a print image inspection device (IMG) that inspects the dot pattern and color information.

[0031] As mentioned above, the print image inspection device (IMG) includes the print inspection device (PID) and the smartphone (SMT), but particularly when inspecting color information, it is done with the smartphone (SMT). Note that a smartphone (SMT) is used here, but a dedicated small mobile terminal may also be used in stores, etc. In particular, by using the print image inspection device (IMG) consisting of a smartphone (SMT) or a small mobile terminal, it becomes possible to inspect color information based on environmental changes in a diverse and simple manner.

[0032] This print image inspection device (IMG) is characterized by having at least an image input unit that captures an image obtained by imaging a recognition target including a dot pattern, a dot pattern recognition unit that determines the match with a predetermined reference dot pattern, a color information acquisition unit that acquires color information from pixel data of the dot portion of the image, a correlation calculation unit that calculates the correlation between the color information data and predetermined reference color information data of an ink, and an ink state determination unit that determines the ink state of the recognition target from the correlation calculated by the correlation calculation unit.

[0033] Next, the specific functions and actions of the above-mentioned components will be described. The print image inspection device (IMG) in Fig. 3 includes an input unit 30, an image input unit 31, an output unit 32, a communication unit 33, a processing unit 34, and a storage unit 35. The calculation results calculated by the processing unit 34 are stored in the storage unit 35.

[0034] The input unit 30 is a section that accepts instructions from an operator, and is composed of buttons, a touch panel, and the like.

[0035] When an image including a dot pattern printed on an object is captured by an image capturing device such as a camera, which is image input unit 31, dot pattern recognition unit 34A determines whether a dot pattern exists and records the dot pattern information in dot pattern memory unit 35A of memory unit 35.

[0036] The output unit 32 outputs instruction information, read images, inspection results, etc. to the operator, and is composed of a display and a communication device. This configuration is standard, and any one or all of the input unit 30, image input device 31, and output unit 32 may be connected to the outside of the print image inspection device (IMG).

[0037] The communication unit 33 has a function of transmitting the scanned image, the inspection result, the product information, etc. to the management server (MSV) via the network (NET). It is also possible to receive information necessary for dot pattern recognition, correlation value calculation, and ink condition determination from the management server (MSV). Quality information that is not to be presented to the operator is not output to the output unit 32, but is stored in the memory unit 35 and can be transmitted to the management server (MSV) via the communication unit 33.

[0038] The main functions of the print image inspection device (IMG) are executed by a processing unit 34 and a storage unit 35, but first the processing unit 34 will be described.

[0039] The processing unit 34 processes the data input from the input unit 30 and the image input unit 31, and outputs the results to the output unit 32 or records them in the storage unit 35, and is composed of the following calculation units.

[0040] Dot pattern recognition unit 34A has a function of recognizing a dot pattern in an image obtained from image input unit 31 by a method specified as a dot pattern recognition method, and recording an image of the dot pattern in dot pattern storage unit 35A. This dot pattern recognition method can be implemented by a method described later.

[0041] For example, recognition is possible by methods such as "specifying the dot size," "specifying the camera autofocus and image scale," "specifying the dot circularity," "specifying the dot size and the distance between dots," "specifying the dot periodicity," "specifying the number of dots," "specifying by consistency with a specified dot pattern," etc. Also, by combining these methods, it becomes possible to recognize dot patterns with a high degree of probability.

[0042] The color information inspection unit 34B has the function of acquiring color information data within a dot pattern in an image obtained by the dot pattern recognition unit 34A using a method specified as a color information inspection method, and recording the color information data in the color information storage unit 35B.

[0043] As will be described later, the location within the dot pattern from which color information data is obtained is not particularly limited, and in terms of numerical values, in addition to CIE color spaces such as L*a*b* and L*C*h*, RGB color space, HSV color space, Munsell color space, etc. are known.

[0044] The correlation value calculation unit 34C has a function of calculating the correlation between the color information data in the dot pattern obtained by the color information inspection unit 34B and a preset reference color information data of a temperature indicating ink, and recording the quality data of the temperature indicating ink obtained thereby in the correlation value information storage unit 35C. As will be described later, the method of calculating the correlation value with the preset reference color information data of the ink is not particularly limited. Note that color information data of the background near the dot pattern may be used when calculating the correlation value.

[0045] Ink condition determination unit 34D has a function of determining the quality of the ink obtained from correlation value calculation unit 34C using predetermined determination criteria, and recording the result data in ink condition storage unit 35D.

[0046] As described later, the predetermined judgment criteria are not particularly limited. For example, if the ink quality data is within a certain range, it can be judged as normal, and if it exceeds the certain range, it can be judged as abnormal. It is also possible to add criteria other than the ink quality data obtained by the correlation value calculation unit 34C to the judgment criteria.

[0047] For example, it is possible to add to the criteria the print information (lot number, manufacturing date, etc.), time information, location information, and environmental information such as temperature and humidity, which are extracted by read data acquisition unit 34E described later.

[0048] The read data acquisition unit 34E has a function of recording information other than the quality data extracted from the image obtained by the dot pattern recognition unit in the read data storage unit 35E. The information to be acquired is not particularly limited, and examples include print information (lot number, manufacturing date, etc.), time information, position information, and environmental information such as temperature and humidity.

[0049] The method of acquiring such information is not particularly limited, and in the case of printed information, a dot pattern may be acquired by image recognition, as in a normal print inspection method. The location, etc. may be acquired by inputting location information in advance, or by providing an image acquisition device (IMG) with a GPS (Global Positioning System) function and acquiring the location when the image is acquired. The temperature, etc. may be acquired by measuring the temperature at the time of image acquisition using a thermometer, or by recording temperature information from a weather forecast.

[0050] The output control unit 34F has a function of outputting the data recorded in the storage unit 35 to the output unit 32 or the communication unit 33. When the output destination is a screen or the like, it is preferable that the result is output each time a reading operation is performed. When the output destination is a communication destination such as a management server (MSV), the output process may be performed each time a reading operation is performed, or the data may be processed by summarizing several times of data or summarizing the data at predetermined intervals.

[0051] Next, a description will be given of the storage unit 35. The storage unit 35 is a section for storing various types of calculation data and the like, and is composed of the following storage units, etc. These storage units are composed of RAM, EEROM, etc.

[0052] The dot pattern storage unit 35A has a function of storing an image of a dot pattern input from an image input device and extracted by the above-mentioned dot pattern recognition unit 34A.

[0053] The color information storage unit 35B has a function of storing color information data within a dot pattern, which is extracted by the above-mentioned color information inspection unit 34B from the image recorded in the dot pattern storage unit 35A.

[0054] The correlation value information storage unit 35C has the function of storing ink quality data calculated from the color information data in the dot pattern extracted by the above-mentioned correlation value calculation unit 34C from the color information data recorded in the color information storage unit 35B.

[0055] The ink condition storage unit 35D has a function of storing result data of ink quality data determined by the ink condition determination unit 34D described above, which is extracted from the ink quality data recorded in the correlation value information storage unit 35C.

[0056] The read data storage unit 35E has a function of storing data extracted by the above-mentioned read data acquisition unit 34E. This read data has a function of recording information other than the quality data extracted from the color information data in the dot pattern, such as print information (lot number, manufacturing date, etc.), time information, position information, and environmental information such as temperature and humidity.

[0057] Next, an example of a flow of processing performed by the print image inspection device (IMG) will be described with reference to FIG.

[0058] <Step S10> In step S10, image data is input from image input unit 31 based on a command from dot pattern recognition unit 34A. Furthermore, this image data is stored in dot pattern storage unit 35A. When this process ends, the process proceeds to steps S11 and S12.

[0059] <Step S11> and <Step S12> In steps S11 and S12, the dot pattern recognition unit 34A recognizes the dot pattern, and further determines whether or not a dot pattern exists. Only when a dot pattern exists, the subsequent processing is executed.

[0060] If there is no dot pattern, no image is recorded, and the process returns to step S10 to again input image data from image input unit 31. When this process ends, the process proceeds to steps S13 and S14.

[0061] <Step S13> and <Step S14> In steps S13 and S14, if a dot pattern is present, the image stored in dot pattern storage unit 35A is used to obtain dot color information data in color information inspection unit 34B. This is then converted into ink quality data in correlation value calculation unit 34C. Using this ink quality data, ink quality status is determined in ink status determination unit 34D. The ink status is determined in one of three ways: "abnormal," "normal," or "outside normal / abnormal range." When this process is complete, the process proceeds to steps S15 to S18.

[0062] <Step S15> to <Step S18> In steps S15 and S18, if the ink is in an abnormal state, the output unit 32 displays the message "abnormal," and data such as the print information, reading time, reading location, and judgment results are transmitted to the management server (MSV) via the output unit 32 and communication unit 33, and the process is terminated.

[0063] Also, in steps S16 and S18, if the ink is in a normal condition, a message indicating that the ink is in a normal state is displayed on the output unit 32, and data such as the printing information, the reading time, the reading location, and the judgment result is transmitted to the management server via the output unit 32 and the communication unit 33, and the process is terminated.

[0064] Furthermore, in steps S17 and S18, if the ink is neither normal nor abnormal, a message stating that the ink is “unrecognizable” is displayed on the output unit 32, and data such as the print information, reading time, reading location, and judgment results are transmitted to the management server (MSV) via the output unit 32 and communication unit 33, and the process is terminated.

[0065] By executing the above-mentioned process, the print inspection device (PID) that becomes the print image inspection device (IMG) and the smartphone (SMT) can be accessed from the factory, shipping area, store, customer, etc., so color information based on environmental changes can be inspected using a variety of simple inspection methods. Furthermore, if the smartphone (SMT) is used as the print image inspection device (IMG), inspection can be easily performed at any time and in any place.

[0066] Below, the functions and operations of the main components constituting the print image inspection device (IMG) shown in FIG. 3 will be explained, but before this explanation, the functional ink will first be explained.

[0067] <Functional ink> The functional ink according to the present embodiment has a mechanism for changing color in response to some environmental change, and can be preferably used as an ink that can be printed by a continuous-jet charge-control type inkjet recording device. For example, functional inks that change color depending on the environmental conditions surrounding an item, such as temperature, humidity, vibration, gas concentration such as oxygen, and air pressure, are known.

[0068] In addition, it is possible to use inks that indicate the environmental conditions around an item by the color they display. Specifically, thermochromic inks that change color depending on thermal history, fluorescent inks that emit light when exposed to ultraviolet light, and the like are known. Furthermore, the color change mechanism of functional inks can be classified into reversible and irreversible. Reversible inks change color any number of times depending on temperature fluctuations, while irreversible inks do not return to their original state once the color changes at a specific temperature.

[0069] In the case of the present embodiment, when the purpose is quality control, by using an irreversible property in which the color does not return to its original state once it has changed, even if the environmental conditions surrounding the item change during distribution, etc., and then return to their original state, it is possible to know that the environmental conditions have deviated from the controlled environment.

[0070] Furthermore, if the ink color changes to an intermediate color, it is possible to grasp the change in the environmental condition around the item in detail. In other words, if the color changes over multiple stages according to the degree of change in the environmental condition, it is possible to trace the environmental change.

[0071] When detecting temperature as the environmental condition around an article, inks containing conventional materials such as inorganic thermochromic materials made of metal complex salts such as CoCl2, and organic thermochromic materials made of condensed aromatic ring substitutes such as spiropyran compounds can be used.

[0072] In addition, the change in color of the dots formed by the ink droplets can be used to detect changes in the temperature around the article. The functional ink is not limited to these materials and compositions, and any ink that changes color in response to environmental changes can be used.

[0073] Next, the functions and operations of the main components that make up the print image inspection device (IMG) shown in Figure 3 will be described.

[0074] <Image input unit 31> The image input unit 31 according to this embodiment has a function of capturing an image of a recognition target including a dot pattern by an image capturing device such as a camera. The image capturing device is not particularly limited, but it is preferable that the area of ​​the dots can be recognized as pixel data with high accuracy as a condition of the lens and resolution.

[0075] On the other hand, recent technological advances have made it possible to adequately inspect using a general-purpose image capture device. In particular, a camera terminal with a communication function is preferably used because the communication function can be utilized when defining the recognition conditions for the dot pattern. In addition, since an image capture device with a print inspection function for inspecting the quality of the print can be used, the mechanism of the present invention can also be provided in a print inspection device.

[0076] <Dot pattern recognition unit 34A> The dot pattern recognition unit 34A has a function of recognizing a dot pattern printed by a continuous jet charge control type ink jet recording device.

[0077] Figures 5A and 5B show an example of the arrangement of dot patterns printed on the background of the printing surface to be recognized. A continuous jet type charge control type inkjet recording device can print various characters, symbols, codes, and other printed information, all of which are formed by the arrangement of dot patterns.

[0078] When the ink forming the dot pattern (dots) is a thermochromic ink whose color changes in response to a change in temperature, the color of the dots changes with a change in temperature, as shown in Figures 5A and 5B. In this embodiment, by inspecting the color information of the dots in the dot pattern (dots) formed with such a thermochromic ink, it is possible to determine whether an item (recognition target) has been exposed to an environmental change due to temperature. Note that, although the color information of the dots is inspected using a thermochromic ink in this embodiment, other functional inks can also be used, and the present invention is not limited to the embodiment.

[0079] Although a continuous-jet charge-controlled inkjet recording apparatus was used as a method for forming the dot pattern, the method for forming the dot pattern is not limited to this embodiment as long as the dot pattern has a similar form.

[0080] The image obtained by capturing an image of a recognition target including a dot pattern is composed of dots and a background without dots, as shown in Fig. 5 A. When an image such as that shown in Fig. 5 A is captured by an image capture device, the dot pattern recognition unit 34A needs to distinguish the difference in color between the pixels of the dots and the background without dots.

[0081] Although there is no particular limitation on the method of this determination, a commonly used method is to binarize the color intensity of pixels using a certain threshold value and distinguish between dots and the background without dots. In this case, pixels with one of the two binary colors can be recognized as pixel data of the dots.

[0082] When clearly binarizing the dots and the background without dots, the greater the color difference between the dots and the background without dots, the easier it is to distinguish the color difference. It is also easy to automatically determine the binarization threshold. Therefore, for example, if a black ink dot pattern is formed on a white background and an image composed only of these is captured, it is easy to recognize the pixels in the dots in the image.

[0083] However, when multiple colors are used for the background color, such as for character information other than the dot pattern, there is a possibility that pixels other than the dot pattern may be recognized as pixel data of the dot portion. In addition, it is difficult to automatically determine the binarization threshold value, and correction by an expert is required.

[0084] Therefore, if the dot pattern recognition unit 34A can recognize a characteristic dot pattern from image data and determine the pixels in the area occupied by the dots, it will be possible to improve the accuracy of recognition of pixel data in the dot area. Also, when a characteristic dot pattern is recognized in setting the threshold for binarization, it is possible to correct the automatic determination so that the threshold is adopted.

[0085] In this way, the dot pattern recognition unit 34 has a function of extracting printed characters from an image obtained by capturing an image of a recognition target and judging the quality of the printed characters. Furthermore, the print information obtained from the printed characters can be used as a criterion for the judgment result.

[0086] Next, an example of an inspection using an actual print image inspection device (IMG) will be specifically described.

[0087] In the following description, methods for improving the recognition accuracy of pixel data in dot portions are described, but these are representative examples and the method for recognizing pixel data in dot portions is not limited to these.

[0088] (A) How to recognize dot patterns based on dot size: The dot area of ​​a dot pattern printed by a continuous-jet charge-control type inkjet recording device is limited to a certain extent. This is because the nozzle diameter of the continuous-jet charge-control type inkjet recording device is limited to several tens of μm to several hundreds of μm, which limits the volume of the ink droplets.

[0089] Therefore, the area of ​​the dot formed by the ink droplet landing on the recognition target depends on the surface tension of the recognition target, but is limited to a certain extent. Specifically, the dot diameter is about 100 μm to 1000 μm.

[0090] Therefore, if a dot of this size can be recognized within an image, the pixel data of the dot portion can be recognized without relying on the arrangement information of the dot pattern.

[0091] (B) Method of recognizing dot patterns based on the dot size and dot distance (Figure 6): When using various image capture devices, there is a possibility that the area of ​​the dots in the image cannot be accurately recognized. As shown in Figure 6, the dot pattern printed by a continuous-jet charge-control type inkjet recording device has a distance between the dots in addition to the area of ​​the dots, and the dots are arranged in a somewhat discrete manner.

[0092] It is possible to print dots adjacent to each other, but if the distance between dots is small, problems arise such as slow printing speed and ink splashing due to contact with each other, resulting in poor print quality.

[0093] Specifically, in a dot pattern, the distance between the centers of two dots is often about 1 to 5 times the diameter of the dots. Therefore, by recognizing the part in the image where the distance between the centers of two dots and the diameter of the dots meet this relationship, it becomes possible to recognize the pixel data of the dot part.

[0094] Furthermore, when reading the color of dots, if the dots are adjacent to each other and overlap, the color of the dots will be darker, and there is a possibility that the color will not be read accurately. Therefore, when recognizing the color of the dots, it is preferable to use a method that limits the setting to print dots with a certain distance between them as the printing method. This makes it easier to define the dot size and the distance between dots, and makes it possible to improve the recognition accuracy of the pixel data of the dots.

[0095] (C) Defining the number of pixels by controlling the camera lens, resolution, and focal length (Figure 7): The problem is that it is not possible to accurately recognize the area of ​​a dot in an image using an image capture device such as a camera. However, if the lens, resolution, and focal length control method of the image capture device are known, it becomes possible to specify to some extent the number of pixels required to form one dot.

[0096] As shown in Figure 7, once the lens, resolution, and focal length control method of the image capturing device are determined, when the focal length to the dot is adjusted automatically or manually during image capture, the length of the pixels in the image is determined to some extent, and it is therefore possible to specify the area of ​​a dot to be any number of pixels.

[0097] (D) Regulation of dot roundness (Fig. 8): When printing with a continuous-jet charge-controlled inkjet recording device, the dots formed are relatively perfectly circular. Based on this characteristic, by defining the circularity of the dots in image processing, it is possible to recognize the pixel data of the dots.

[0098] As shown in Figure 8, circularity is defined as "4π x dot area ÷ (square of dot perimeter)", with the closer the value is to 1.0, the closer it is to a perfect circle. For dots printed by a continuous-jet charge-controlled inkjet recording device, the dots can be recognized by specifying the value as 0.8 to 1.0.

[0099] Furthermore, if there is no pixel data within the background of the image that is relatively circular other than the dots, even if a relatively wide range is specified, such as a value of 0.2 to 1.0, there is little chance that pixels other than the dots will be recognized as pixel data of the dot portion.

[0100] By defining the circularity within a relatively wide range, even in a dot pattern in which dots are connected within an image and the circularity of the dots is low, the dots can be recognized as pixel data.

[0101] (E) Definition of dot periodicity (Figure 9): In printing using a continuous-jet charge-controlled inkjet recording device, the dot size and the distance between dots are determined to a certain extent, so a method of defining the periodicity of dots can also be used.

[0102] As shown in (a) of Figure 9, when printing a character or symbol in which at least three or more dots are arranged in a row, image processing will produce areas in which periodicity is observed in the intensity of color in one axial direction (shown by a white line) in a two-dimensional image. There are no particular limitations on the method of evaluating the periodicity, but for example, as shown in (b) of the figure, by evaluating the period and intensity of the power spectrum obtained by performing a Fourier transform in a two-dimensional image, it is possible to recognize the presence of an array of dots in one axial direction in which high-frequency correlation is observed.

[0103] Furthermore, as shown in (c), by evaluating the color intensity for the axis on which the array of dots exists, it is possible to recognize it as pixel data for the dot portion. The specified values ​​for the period and intensity of the power spectrum change depending on the color intensity of the dots and the number of dots to be inspected, so they must be set arbitrarily in advance.

[0104] (F) Number of dots: When an image obtained by capturing an image of a recognition target including a dot pattern is processed to recognize pixel data of the dot portion, the recognition accuracy can be improved by specifying the number of dots as a recognition condition.

[0105] When forming a dot pattern with a continuous jet charge control type inkjet recording device, the number of dots to be printed is determined when setting printing information such as various characters, symbols, codes, etc. By setting a prescribed condition including the number of dots, if the number of dots is recognized during image processing, it can be determined that a dot pattern exists, and the pixel data of the dots can be recognized.

[0106] A continuous-jet charge-controlled inkjet recording device usually prints some kind of character or symbol, so it is highly likely that it will print at least 10 dots, and it rarely prints one or two dots. Therefore, by setting the number of dots to 10 or more as a specified condition, it is possible to inspect the print dot patterns of any character or symbol without specifying the conditions in advance.

[0107] However, because it may be impossible to recognize more than 10 dots due to issues such as the accuracy of the image capture device or the peeling off of dots from the object to be recognized, it is acceptable to specify a smaller number, such as 5 or more dots.

[0108] By setting a dot number close to the number of dots to be printed in advance as the specified condition, it is possible to recognize only the condition with a dot number close to the dot pattern to be inspected, making it possible to recognize the dot pattern to be inspected with greater accuracy.

[0109] (G) Dot Pattern Regulations: In addition to the above-mentioned method, it is also possible to specify the dot patterns of characters, symbols, etc. to be printed by a continuous jet charge-controlled inkjet recording device. As with the print inspection device, a method can also be used in which image data of dot patterns that have formed normally printed characters is stored in advance, and the dot pattern is recognized based on the degree of match with that data.

[0110] If the image capture device has a print inspection function, color evaluation and print inspection can be performed simultaneously. When performing print inspection, the dot pattern is specified in advance, and the specified conditions can be preferably used.

[0111] <Color information inspection unit 34B> The color information inspection unit 34B, which is a feature of this embodiment, has a function of acquiring color information from pixel data of dot portions of the image obtained by the image input unit 31.

[0112] As a method for acquiring color information from pixel data of a dot portion, the image processing method is not particularly limited as long as it is a method for reading color information of pixel data of a dot portion recognized by dot pattern recognition unit 34A.

[0113] For example, the color of the pixel in the center of the dot portion of the read dot pattern may be evaluated, or the color of the dot portion of the read dot pattern may be evaluated based on the value with the largest color difference from the background color, or the color information of the read dot portion may be averaged for all pixels in the dot portion and this value may be evaluated.

[0114] Also, it is sufficient that at least a dot portion is included, and evaluation may be performed by averaging color information in pixels including a dot portion and a background portion around a pixel including a dot portion.

[0115] The method of evaluating the color of an image is not particularly limited. For example, the color tone can be calculated from the gradation of the pixels of the captured image. Alternatively, light may be projected by laser scanning or the like, an image may be acquired from the amount of reflection or absorption of the projected light, and color information may be calculated. * a * b * Or L * C * h * In addition to the CIE color spaces such as those listed above, the RGB color space, the HSV color space, the Munsell color space, and the like can also be used.

[0116] <Correlation value calculation unit 34C> The correlation value calculation section 34C, which is a feature of this embodiment, has a function of calculating a correlation value between the color information obtained by the color information inspection section 34B and preset reference color information data of an ink.

[0117] The method of calculating the correlation value with the preset reference color information data of the ink is not particularly limited, but for example, when evaluating the color by the average value of the RGB color space, it is possible to check whether the dots are inspected correctly by evaluating the difference between the normal color and the inspected color. When the color of the dot changes in response to some environmental change, such as with functional ink, only inks with colors within a preset range of discoloration can be recognized, and the extent of discoloration can be determined.

[0118] In color evaluation, measurement errors occur due to various factors such as the lighting environment, the transmission and reflection of the dots, the reflection of the background color of the recognition target, the effect of curvature, the casting of shadows, etc. In cases where the color intensity of the dot and the background color is large, or when the amount of discoloration of the dots to evaluate the discoloration of functional ink is large, the judgment tolerance can often be set large, and calculations can be made even if the measurement error is large.

[0119] In addition, as a method for reducing measurement errors in color evaluation, it is preferable to keep the lighting environment constant. On the other hand, if the lighting environment is limited, it becomes difficult to take pictures in a variety of environments. Therefore, it is also possible to reduce measurement errors by inspecting the background color and applying the correlation between the numerical value and the dot color to the inspection of color information.

[0120] In this case, it is preferable to predefine the background color, which can be determined by taking an image once under an appropriate lighting environment or by inputting a predefined value.

[0121] There is no particular limitation on the method for evaluating the correlation value between the color of the dot portion and the color of the background, but a method can be used in which the difference between the color of a dot of normal color and the color of the background is evaluated and specified in advance, and then the color of the dot portion and the color of the background are similarly inspected during inspection, and the color of the dot is evaluated based on the degree of change in that difference.

[0122] There is no particular limitation on the method of evaluating the background color. It is possible to use pixel data other than the pixel data of the recognized dot portion and evaluate the average value, or to evaluate the colors of pixels in a range a certain distance away from the dot portion, or to use the value of the pixel data other than the pixel data of the recognized dot portion that has the largest color difference from the dot color.

[0123] <Ink state determination unit 34D> The ink state determination unit 34D, which is a feature of this embodiment, has a function of determining the state of the recognition target represented by the ink based on the color evaluation result of the correlation value calculation unit 34C.

[0124] The method of judgment is not particularly limited, but it is necessary to predefine the judgment criteria. For example, when evaluating a color based on the average value of the RGB color space, if the average value of the RGB color space is a certain value, it is judged as judgment A, and if it is another certain value, it is judged as judgment B. Of course, judgment in multiple stages is also possible.

[0125] For example, when inspecting a dot pattern formed by printing functional ink for the purpose of managing the quality of a recognition object, the dots change color depending on the environmental temperature, as shown in Fig. 10 (a) showing before heating (0 minutes) and (b) showing after heating (10 minutes). In Fig. 10 (a), the dots were "blue," but in Fig. 10 (b), they have changed color to "yellow." Then, as shown in Fig. 10 (c), by comparing with a threshold value "(R+G+B) / 3=130," it is possible to determine from the color evaluation result whether the quality state of the recognition object has been exposed to an environment of "normal," "warning," or "abnormal."

[0126] As a result of the judgment, it is possible to display judgment results that are different from the judgment criteria for color evaluation, such as a recognition error of the dot pattern, the number of dots, etc. If it is equipped with a print inspection device function, it is also possible to display the print inspection results and information on the characters, symbols, and codes that have been read.

[0127] The image capture device, which is the image input unit 31 according to this embodiment, the correlation value calculation unit 34C, and the ink state determination unit 34D may be executed multiple times for one dot pattern, and multiple units may be used. In this case, a camera terminal with a communication function or the like can be preferably used. In this way, it is also one of the features that the image capture device is a camera terminal with a communication function.

[0128] Another feature is that when a dot pattern is inspected multiple times using a print image inspection device, either the same print image inspection device or different print image inspection devices, the image data, image inspection data, or judgment data obtained during the inspection can be shared and used for the inspection method, inspection results, and judgment results from the second time onwards.

[0129] Even if the camera terminal does not have a communication function, image data, calculation data, judgment data, etc. can be saved and shared among a plurality of image capturing devices using a terminal with a communication function, etc. For example, it is possible to inspect color information, printing information, etc. of a dot pattern of functional ink with a print inspection device, and after the color of the functional ink changes, the color information, printing information, etc. of the dot pattern can be inspected with a camera terminal with a communication function.

[0130] In this case, it is possible to use the inspection results from the first print inspection device as the inspection method and judgment criteria for the second camera terminal with communication function. For example, the difference in color information between the first and second inspections may be calculated, or the first print information (lot number, manufacturing date, etc.) may be added to the inspection conditions for the second dot pattern.

[0131] In this way, one of the features is that by performing an image inspection once, the dot pattern arrangement information and ink color information data are stored, and when an image inspection is performed again, the correlation between the dot pattern arrangement information and the ink color information data is calculated as the ink color information data preset in the correlation value calculation unit.

[0132] It is also possible to inspect the manufacturing date, which is the printed information, the first time, and if a certain period of time has passed since the manufacturing date at the time of the second inspection, to determine that there is an abnormality. In other words, it is possible to add environmental information (time, weather, location, etc.) at the time of inspection to the judgment result. In this way, one of the features is that environmental information such as the time, location, and temperature at the time of inspection is used as a criterion for the judgment result.

[0133] Next, an example of an inspection using an actual print image inspection device (IMG) will be specifically described.

[0134] [Creating dot patterns using functional inks] Thermochromic ink, which changes color depending on thermal history, was filled into an inkjet recording device (Hitachi Industrial Equipment Systems Co., Ltd., Inkjet Printer UX type), and printed on a glass substrate. The printed dots printed on the substrate were "blue" in the initial state. When the printed substrate was left to stand in an environment of 70°C, it was visually confirmed that the color slowly began to develop yellow after 1 minute, and that the color had completely developed to yellow after 10 minutes. The color of the dots on this printed substrate was examined.

[0135] [Dot pattern color inspection] Figure 10 shows the color change of the printed dots created by heating. A smartphone (Huawei, P8lite) was used as the image capture device, and the object to be recognized, including the dot pattern, was captured using the autofocus function. The captured image was binarized using image processing software (ImageJ) and the position of the dot pattern was detected.

[0136] The pixel data of the dots was detected under the following detection conditions for the dot pattern: dot pixel area (which depends on the dot diameter) is 50 to 200, dot circularity is 0.2 to 1.0, and the number of dots is 40 to 60. As shown in Figure 11(a), it can be seen that 52 printed dots were successfully inspected.

[0137] Using this method, the color of the detected dots was evaluated based on the average RGB values ​​of (b) before heating (0 minutes) and (c) after heating (10 minutes). The evaluation results are also shown in Figure 11. As shown in Figure 11, it can be seen that the change in the color of the dots was quantified.

[0138] As a judgment standard, as shown in Fig. 10, if the average value of RGB is less than 130, it is displayed as "before heating," and if it is 130 or more, it is displayed as "after heating." From the results, it was determined that the condition was before heating from 0 to 5 minutes after heating to 70°C, and that the condition was after heating from 5 to 10 minutes.

[0139] From the above, it was possible to confirm that the print image inspection device of this embodiment can be used to inspect the color of a dot pattern formed by a continuous injection charge-controlled inkjet recording device, and to determine the condition of the ink from the color information.

[0140] In this way, the print inspection device (PID) that becomes the print image inspection device (IMG) and the smartphone (SMT) can be accessed from factories, shipping areas, stores, customers, etc., so color information based on environmental changes can be inspected using a variety of simple inspection methods. Furthermore, if the smartphone (SMT) is used as the print image inspection device (IMG), inspection can be easily performed at any time and in any place.

[0141] Furthermore, by equipping the management server (MSV) with the function of the print image inspection device (IMG), it is possible to transfer captured images from a smartphone (SMT) or small mobile terminal to the management server (MSV) and perform image inspection on the management server (MSV). This is particularly effective when managing the thermal history of a large number of products during the distribution process in a store.

[0142] The present invention is not limited to the above-mentioned embodiments, but includes various modified examples. The above-mentioned embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those having all the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace other configurations with respect to the configuration of each embodiment. [Explanation of symbols]

[0143] 10...ink container, 11...ink liquid, 12...ink supply pump, 13...ink nozzle, 14...piezoelectric element, 15...ink column, 16...charging electrode, 17...ink droplet, 18, 19...deflection electrodes, 20...printing object, 21...gutter, 30...input section, 31...image input section, 32...output section, 33...communication section, 34...processing section, 34A...dot pattern recognition section, 34B...color information inspection section, 34C...correlation value calculation section, 34D...ink status determination section, 34E...read data acquisition section, 35...memory section, 35A...dot pattern memory section, 35B...color information memory section, 35C...correlation value information memory section, 35D...ink status memory section.

Claims

1. A print image inspection device that acquires color information of a dot portion of an image obtained by imaging a recognition target having a dot pattern arranged therein, and outputs a judgment result based on the color information, an image input unit that captures an image of a recognition target including the dot pattern; a dot pattern recognition unit that judges whether the dot pattern matches a predetermined reference dot pattern; a color information acquisition unit that acquires color information from pixel data of a dot portion of the image; a correlation value calculation unit that calculates a correlation value between the color information data of the color information and reference color information data of a preset ink; an ink state determination unit that determines the state of the ink to be recognized from the correlation value of the correlation value calculation unit; A print image inspection device characterized by:

2. The print image inspection device according to claim 1, The dot pattern is a dot pattern formed by a continuous jet charge control type ink jet recording device. A print image inspection device characterized by:

3. 3. The print image inspection device according to claim 2, The dot pattern is formed using a functional ink that changes color in response to environmental changes. A print image inspection device characterized by:

4. 3. The print image inspection device according to claim 2, The dots of the predefined standard dot pattern have a dot diameter of 100 nm to 1000 nm. A print image inspection device characterized by:

5. 3. The print image inspection device according to claim 2, The dot pattern recognition unit prestores information on the lens, resolution, and focal length control method of an image capture device that captures the recognition target on which the dot pattern is arranged, and recognizes the area of ​​dots in the dot pattern that is predefined from the stored information. A print image inspection device characterized by:

6. 3. The print image inspection device according to claim 2, In the dot pattern of a predetermined standard, the circularity of the dots is 0.2 or more. A print image inspection device characterized by:

7. 3. The print image inspection device according to claim 2, In the predetermined standard dot pattern, the distance between the centers of two dots is 1 to 3 times the diameter of the dots. A print image inspection device characterized by:

8. 3. The print image inspection device according to claim 2, In the predetermined reference dot pattern, at least three dots have periodicity in one axial direction. A print image inspection device characterized by:

9. 3. The print image inspection device according to claim 2, In the dot pattern of a predetermined standard, the number of dots is set to a predetermined number. A print image inspection device characterized by:

10. 3. The print image inspection device according to claim 2, In the dot pattern of a predetermined standard, the arrangement information of the dot pattern is defined as predetermined arrangement information. A print image inspection device characterized by:

11. 3. The print image inspection device according to claim 2, the color information acquisition unit acquires the color information from pixel data of the dot portion of the image, and also acquires the color information from pixel data of a background portion of the image; The correlation value calculation unit calculates the correlation value with the color information data of the ink and the color information data of a background color of the dot pattern that is set in advance. A print image inspection device characterized by:

12. 3. The print image inspection device according to claim 2, When the dot pattern is inspected multiple times, any one of image data, image inspection data, and judgment data obtained during the inspection is shared and used for the inspection method, inspection results, and judgment results from the second time onwards. A print image inspection device characterized by:

13. A print image inspection method for acquiring color information of a dot portion of an image obtained by imaging a recognition target having a dot pattern arranged therein, and outputting a judgment result based on the color information, comprising: an image input step of capturing the image obtained by capturing an image of a recognition target including the dot pattern; a dot pattern recognition step for determining whether the dot pattern matches a predefined reference dot pattern; a color information acquisition step of acquiring color information from pixel data of a dot portion of the image; a correlation value calculation step of calculating a correlation value between the color information data of the color information and a preset reference color information data of an ink; An ink state determination step is executed to determine the state of the ink of the recognition target based on the correlation value calculated in the correlation value calculation step. A print image inspection method comprising:

14. The print image inspection method according to claim 13, storing the arrangement information of the dot pattern and the color information data of the ink by performing an image inspection; When the image inspection is carried out again, the correlation value between the arrangement information of the previous dot pattern and the color information data of the ink is calculated as the color information data of the ink that is preset in the correlation value calculation step. A print image inspection method comprising:

Images