WO2023281923A1

WO2023281923A1 - Printed image inspection device and printed image inspection method

Info

Publication number: WO2023281923A1
Application number: PCT/JP2022/020703
Authority: WO
Inventors: 航平會田; 倫子前島; 雅彦荻野
Original assignee: 株式会社日立産機システム
Priority date: 2021-07-07
Filing date: 2022-05-18
Publication date: 2023-01-12
Also published as: JP2023009424A

Abstract

The present invention provides a printed image inspection device in which color information based on environmental changes can be inspected using various convenient inspection procedures.　The present invention pertains to a printed image inspection device which acquires, from an image obtained by capturing an image of a recognition target in which a dot pattern is arranged, color information for dot portions of the image, and outputs a determination result based on this color information, said inspection device having: an image input unit (31) which imports the image obtained by capturing an image of the recognition target including the dot pattern; a dot pattern recognition unit (34A) which determines matching with a pre-specified reference dot pattern; a color information acquisition unit (34B) which acquires color information from pixel data of the dot portions of the image; a correlation calculation unit (34C) which calculates the correlation between the color information data and pre-set ink reference color information data; and an ink state determination unit (34D) which determines an ink state of the recognition target on the basis of the correlation from the correlation calculation unit.

Description

PRINTED IMAGE INSPECTION DEVICE AND PRINTED IMAGE INSPECTION METHOD

The present invention relates to an image inspection device and image inspection method, and more particularly to a printed image inspection device and printed image inspection method for inspecting an image printed by an inkjet recording device.

In order to print expiration dates, use-by dates, manufacturing numbers, etc. given to products, continuous-jet charge control type inkjet recording devices are used in a wide range of fields such as food and electronic parts.

A typical continuous-jet charge-controlled inkjet recording apparatus has an ink container that stores ink in its main body, and the ink in the ink container is supplied to the print head by an ink supply pump.

The ink supplied to the print head is continuously ejected from the ink nozzles and formed into ink droplets. Of the ink droplets used for printing, the ink droplets that are used for printing are charged and deflected so that they fly to the desired printing position on the object to be printed to form characters and symbols. , the ink is collected by a gutter and returned to the ink container by an ink recovery pump without being charged or deflected.

Such a continuous ejection charge control type inkjet recording device has a high printing speed, so it is easy to apply to the production process of mass-produced products. On the other hand, printing by a continuous-jet charge control type ink jet recording apparatus has a high printing speed. Therefore, a print inspection device is used to inspect whether printed characters such as the expiration date, use-by date, manufacturing number, etc. are printed according to the set data.

In printing with a continuous-jet, charge-controlled inkjet recording device, dots are formed when ink droplets ejected from nozzles land on the object to be recognized (printing surface). By arranging these dots in a set pattern, printed characters and symbols are formed. At this time, in order to cope with high-speed printing, a dot pattern is often formed by discretely arranging fine dots.

A print inspection device is required to inspect at high speed whether printed characters made up of these dot patterns form normal dot patterns. The print inspection apparatus captures an image of an object to be recognized in which printed characters made up of dot patterns are arranged, and uses image processing to determine whether each dot position is normally printed in the obtained image.

As an image processing method, for example, a method is used in which determination is made based on the degree of matching between image data of a dot pattern in which printed characters are formed normally in advance and image data of a dot pattern that is actually printed. For example, Japanese Patent Application Laid-Open No. 2008-89379 (Patent Document 1) describes a method in which defective printing is captured as an image in advance by imaging means, whether or not a printing target is recognized as defective printing is inspected, and the inspection result is recorded. A print inspection device is disclosed. Further, Japanese Patent Application Laid-Open No. 2011-16261 (Patent Document 2) discloses an ink droplet landing position accuracy inspection method for determining whether or not the ink droplet landing position of an inkjet printer has deviated. .

JP 2008-89379 A JP 2011-16261 A

By the way, in recent years, it has been proposed to give printing ink a function different from the purpose of printing (for example, the purpose of identification as characters) and use it for quality control of mass-produced products. For example, functional inks may be used to control whether a product has been adversely affected by heat in the environment over time. In addition to this, it is conceivable to manage whether or not the body has been adversely affected by ultraviolet rays over a long period of time.

As inks with such functionality, color-changing inks such as temperature-indicating inks that change color according to heat history and fluorescent inks that emit light when exposed to ultraviolet light are often used. These functional inks change their hue and color tone depending on some environmental changes. can be known to have been adversely affected by heat and ultraviolet rays (effects of environmental changes).

Therefore, when printing with functional ink, it is necessary to inspect the dot color information 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.

As mentioned above, print inspections are often used in the manufacturing process, while color information inspections based on environmental changes are especially required in environments that change over time, such as distribution and consumption processes. Therefore, it is desirable to be able to perform inspections using various and simple inspection techniques. However, Patent Document 1 and Patent Document 2 do not consider such a problem, much less disclose or suggest a solution to the problem.

An object of the present invention is to provide a printed image inspection apparatus and a printed image inspection method that can inspect color information based on environmental changes using a variety of simple inspection techniques.

The present invention is a printed image inspection apparatus that acquires color information of the dot portion of the image from an image obtained by imaging a recognition target in which a dot pattern is arranged, and outputs a judgment result based on this color information. an image input unit that captures an image obtained by picking up a recognition target including a dot pattern; a dot pattern recognition unit that determines consistency with a predetermined reference dot pattern; and pixel data of the dot portion of the image. a color information acquisition unit that acquires color information from the , and an ink state determination unit that determines the ink state of the object to be recognized.

According to the present invention, color information based on environmental changes can be inspected by various and simple inspection methods.

1 is a configuration diagram showing a rough configuration of an inkjet recording apparatus; FIG. FIG. 2 is an explanatory diagram for explaining a delivery route of an article and a network of print image inspection apparatuses and a management server along the delivery route; 1 is a block diagram showing the configuration of a printed image inspection apparatus according to an embodiment of the present invention; FIG. FIG. 4 is a flowchart for explaining a processing procedure of the print image inspection apparatus shown in FIG. 3; FIG. FIG. 4 is an explanatory diagram illustrating a state of a printed print dot pattern before heat is applied; FIG. 10 is an explanatory diagram for explaining a state of a printed print dot pattern after heat is applied; FIG. 10 is an explanatory diagram for explaining a first dot pattern recognition method; It is an explanatory view explaining the 2nd recognition method of a dot pattern. It is an explanatory view explaining the 3rd recognition method of a dot pattern. It is an explanatory view explaining the 4th recognition method of a dot pattern. FIG. 4 is an explanatory diagram for explaining a method of inspecting the color of printed dots; FIG. 10 is an explanatory diagram for explaining a state in which the color of an actual print dot is inspected;

Hereinafter, 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 applications can be made within the technical concept of the present invention. First, the configuration and operation of a general continuous-jet charge control type inkjet recording apparatus will be briefly described. FIG. 1 schematically shows the configuration of an inkjet recording apparatus. In FIG. 1, an 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 the piezoelectric element 14 installed in the ink nozzle 13, the ink in the ink nozzle 13 is excited. The excited ink is ejected as an ink column 15 from the ink nozzle 13 and then becomes an ink droplet. Here, in this embodiment, "temperature indicating ink" is used as the functional ink. A temperature-sensitive ink is an ink whose color information changes depending on the temperature.

For the ink used for printing, the ink droplets are charged by the charging electrode 16 at the same time as the ink droplets are formed. The charged ink droplets 17 are deflected by the electric field generated in the deflection space between the positive deflection electrode 18 and the negative deflection electrode 19 and then land on the printing object 20 . In addition, the ink droplets 17 not used for printing are not charged and are not deflected, so they are collected by the gutter 21 .

Articles (products) printed by such an inkjet recording device are delivered to customers through the distribution route shown in Fig. 2, and this distribution route is managed by a quality control system.

The quality control system consists of an inkjet recording device (IJP) that prints temperature-sensitive ink, a printed image inspection device (IMG) that acquires the dot pattern printing information printed on the article, and the color information of the temperature-sensitive ink (here, printing inspection device (PID) and smart phone (SMT)), and a management server (MSV). An inkjet recording device (IJP), a print inspection device (PID), a smart phone (SMT), and a management server (MSV) are communicably connected via a network (NET).

For example, if the goods are PET bottles for beverages, the distribution route is the manufacturing plant that manufactures PET bottles for beverages, the storage warehouse that stores the PET bottles, the shipping area that ships the PET bottles, and the transportation that transports the PET bottles. Cars, stores that sell PET bottles (convenience stores, etc.), and customers who purchase PET bottles.

Printing information is sent to the management server (MSV) by the printing inspection device (PID) from the manufacturing factory and the shipping area, and color information is sent to the management server (MSV) from the store and the customer by the smart phone (SMT). It is The management server (MSV) collects the sent management data such as print information and color information. At each location, the operator uses a print image inspection device (print inspection device or smart phone) to collect quality control data.

In the management server (MSV), (1) dot pattern recognition information, (2) ink condition determination information, (3) product information, (4) production information, (5) reading information, (6) quality information, (7) ) distribution information, (8) distribution management information, etc. are managed as files.

By checking the color tone and hue of the temperature-indicating ink, the operator can visually check the temperature control status of each process and the temperature load status of the item. In addition to visual confirmation by the operator, numerical information can be obtained as tone/hue.

Furthermore, in each process such as shipping, transportation, and storage, the operator uses the print image inspection device (IMG) to check the optical state of the PET bottle and its temperature-indicating ink, as well as quality control information such as its image, reading place, and time. and send it to the management server (MSV).

At the store, the operator can visually check the temperature control status and temperature load status from the time of shipment from the manufacturing factory to the transportation process by checking the hue/color tone of the temperature-indicating ink of the transported PET bottles. can do. Furthermore, by connecting to the management server (MSV) via the printed image inspection device (IMG), it is possible to confirm information such as quality control information up to the time of delivery of the PET bottle.

The print image inspection device (IMG) can determine whether or not the quality is maintained based on the color information of the temperature-sensitive ink, and display the determination result on the output unit such as a liquid crystal screen. Therefore, the operator can easily confirm the result. The quality control data including the judgment result is transmitted to the management server (MSV), and the management server (MSV) stores it as quality control information.

In this embodiment, the print image inspection device (IMG) side processes the quality judgment as to whether or not the quality is maintained. This is to disperse the concentration of arithmetic processing such as determination processing in a system that handles a large number of articles. It goes without saying that if the management server (MCV) has a high processing capability, the quality judgment may be executed on the management server (MSV) side.

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 printed image inspection device (IMG) for inspecting dot patterns and color information.

As mentioned above, the print image inspection device (IMG) includes the print inspection device (PID) and the smartphone (SMT), but when inspecting color information in particular, the smartphone (SMT) is used. Note that although a smart phone (SMT) is used here, a dedicated small portable terminal may be used at a store or the like. In particular, by using a print image inspection device (IMG) consisting of a smart phone (SMT) or a small portable terminal, color information based on environmental changes can be inspected in a variety of ways and easily.

This printed image inspection device (IMG) includes at least an image input unit that takes in an image obtained by picking up an image of a recognition target including a dot pattern, and a dot pattern recognition unit that determines matching with a predetermined reference dot pattern. a color information acquisition unit that acquires color information from the pixel data of the dot portion of the image; and a correlation calculation unit that calculates the correlation between the color information data and the preset ink reference color information data. and an ink condition determination unit that determines the ink condition of a recognition target from the correlation of the correlation calculation unit.

Next, the specific functions and actions of the components mentioned above will be explained. The printed image inspection apparatus (IMG) in FIG. 3 includes an input section 30, an image input section 31, an output section 32, a communication section 33, a processing section 34, a storage section 35, and the like. A calculation result calculated by the processing unit 34 is stored in the storage unit 35 .

The input unit 30 is a part that receives instructions from the operator, and is composed of buttons, a touch panel, and the like.

When an image including a dot pattern printed on an article is captured by an image capturing device such as a camera, which is the image input unit 31, the dot pattern recognition unit 34A determines whether the dot pattern exists. 35 is recorded as dot pattern information in the dot pattern storage unit 35A.

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

The communication unit 33 has a function of transmitting read images, inspection results, article 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 state determination from the management server (MSV). Quality information that is not presented to the operator can be stored in the storage section 35 without being output to the output section 32 and transmitted to the management server (MSV) via the communication section 33 .

The main functions of the printed image inspection device (IMG) are executed by the processing unit 34 and the storage unit 35. First, the processing unit 34 will be described.

The processing unit 34 processes data input from the input unit 30 and the image input unit 31 and outputs the result to the output unit 32 or records it in the storage unit 35. The processing unit 34 is composed of the following calculation units. there is

The dot pattern recognition section 34A has a function of recognizing the dot pattern in the image obtained from the image input section 31 and recording the image image of the dot pattern in the dot pattern storage section 35A by a method designated as the dot pattern recognition method. have. This dot pattern recognition method can be implemented by a method described later.

For example, "regulation of dot size", "regulation of camera autofocus and image scale", "regulation of dot roundness", "regulation of dot size and distance between dots", "regulation of dot periodicity", Recognition is possible by methods such as "prescription of the number of dots" and "prescription based on matching with a designated dot pattern". Also, by combining these techniques, it is possible to recognize dot patterns with high probability.

The color information inspecting section 34B acquires the color information data in the dot pattern in the image obtained from the dot pattern recognizing section 34A by a method specified as the color information inspecting method, and records it in the color information storage section 35B. have a function.

As will be described later, the location where the color information data in the dot pattern is obtained is not particularly limited, and numerical values include the CIE color space such as L*a*b* and L*C*h*, as well as the RGB color space. , HSV color space, and Munsell color space.

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

The ink state determination unit 34D has a function of determining the ink quality data obtained from the correlation value calculation unit 34C using predetermined determination criteria, and recording the resulting data in the ink state storage unit 35D. there is

As will be described later, the predetermined criteria are not particularly limited. For example, if the ink quality data is within a certain range, it can be determined as normal, and if it exceeds the certain range, it can be determined as abnormal. It is also possible to add criteria other than the ink quality data obtained from the correlation value calculator 34C to the determination criteria.

For example, print information (lot number, date of manufacture, etc.), time information, location information, and environmental information such as temperature and humidity extracted by the read data acquisition unit 34E, which will be described later, can be added to the criteria. is.

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 printed information (lot number, date of manufacture, etc.), time information, location information, environmental information such as temperature and humidity, and the like.

The method of acquiring this information is also not particularly limited, and if it is print information, it can be obtained by image recognition of a dot pattern, like a normal print inspection method. Location information may be input in advance, or the image acquisition device (IMG) may be provided with a GPS (Global Positioning System) function and acquired at the time of image acquisition. As for the temperature and the like, the temperature at the time of image acquisition may be measured using a thermometer, or the temperature information of the weather forecast may be recorded.

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 collected several times or collected at predetermined time intervals. Also good.

Next, the storage unit 35 will be explained. The storage unit 35 is a portion that stores various types of calculation data and the like, and is composed of the following storage units and the like. These storage units are composed of RAM, EEROM, and the like.

The dot pattern storage unit 35A has a function of storing image images of dot patterns input from the image input device and extracted by the dot pattern recognition unit 34A described above.

The color information storage section 35B has a function of storing the color information data in the dot pattern extracted by the above-described color information inspection section 34B from the image recorded in the dot pattern storage section 35A.

The correlation value information storage unit 35C stores the ink quality data calculated from the color information data in the dot pattern extracted by the correlation value calculation unit 34C from the color information data recorded in the color information storage unit 35B. It has a memorization function.

The ink state storage unit 35D has a function of storing result data of ink quality data that is extracted by the ink state determination unit 34D from the ink quality data recorded in the correlation value information storage unit 35C. ing.

The read data storage unit 35E has a function of storing the data extracted by the read data acquisition unit 34E described above. This read data has a function to record information other than the quality data extracted from the color information data in the dot pattern. Examples include printing information (lot number, manufacturing date, etc.), time information, position information, and environmental information such as temperature and humidity.

Next, an example of the flow of processing performed by the print image inspection device (IMG) will be described using FIG.

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

<<Step S11>>, <<Step S12>>
In steps S11 and S12, the dot pattern recognition section 34A recognizes the dot pattern, determines whether or not there is a dot pattern, and executes the subsequent processes only when there is a dot pattern.

If there is no dot pattern, the image is not recorded, the process returns to step S10, and the image data is input from the image input unit 31 again. When this process ends, the process moves to steps S13 and S14.

<<Step S13>>, <<Step S14>>
In steps S13 and S14, if a dot pattern exists, the image recorded in the dot pattern storage section 35A is used to acquire dot color information data in the color information inspection section 34B. Further, the correlation value calculator 34C converts the data into ink quality data. Using this ink quality data, the ink quality determination section 34D determines the ink quality. The ink status is determined in three ways: "abnormal", "normal", and "out of normal/abnormal range". When this process ends, the process moves to steps S15 to S18.

<<Step S15>> to <<Step S18>>
In steps S15 and S18, if the ink is in an abnormal state, the output unit 32 displays "abnormal", and the output unit 32 or the output unit 32 displays data such as print information, reading time, reading location, and judgment result. It is transmitted to the management server (MSV) via the communication unit 33, and the process ends.

Further, in steps S16 and S18, if the ink is in a normal state, the message "normal" is displayed on the output unit 32, and data such as print information, reading time, reading location, and determination result are output. It is transmitted to the management server via the unit 32 and the communication unit 33, and the process ends.

Further, in steps S17 and S18, if the ink is neither normal nor abnormal, the message "not recognizable" is displayed on the output unit 32, and the printed information, reading time, reading location, judgment result, etc. are displayed. The data is transmitted to the management server (MSV) via the output unit 32 and the communication unit 33, and the process ends.

By executing the above process, access can be made from factories, shipping areas, stores, customers, etc., using a print inspection device (PID) and a smartphone (SMT) that become a print image inspection device (IMG), so environmental changes The color information based on the color can be inspected by various and simple inspection methods. If a smart phone (SMT) is used as a printed image inspection device (IMG), inspection can be easily performed at any time and at any place.

The functions and operations of the main components that make up the printed image inspection device (IMG) shown in FIG. 3 will be described below, but before this description, the functional ink will be described first.

<Functional ink>
The functional ink according to the present embodiment has a mechanism that changes 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. can. For example, functional inks are known that change color depending on the environmental conditions around the article, such as temperature, humidity, vibration, gas concentration such as oxygen, and atmospheric pressure.

In addition, it is possible to use colors that indicate the environmental conditions around the item. Specifically, temperature-indicating ink that changes color according to heat history, fluorescent ink that emits light when exposed to ultraviolet rays, and the like are known. Furthermore, there are reversible and irreversible discoloration mechanisms of functional inks. A reversible type changes color any number of times depending on temperature rise and fall, and an irreversible type does not return to its original color once it changes at a certain temperature.

For the purpose of quality control, as in the present embodiment, if a material having an irreversible property that once the color changes does not return to its original color, the color will return to its original state due to changes in the environmental conditions around the goods in the distribution route or the like. Even so, it is possible to know that the environmental state has deviated from the controlled environment.

Also, if the ink color changes to have an intermediate color, it is possible to finely grasp changes in the environmental conditions around the article. That is, environmental changes can be traced by performing color changes over a plurality of stages according to the degree of change in environmental conditions.

When detecting the temperature as the environmental condition around the article, for example, inorganic thermochromic materials made of metal complex salts such as CoCl2, organic thermochromic materials made of condensed aromatic ring substitutes such as spiropyran compounds, etc. Inks with conventionally used materials can be used.

Also, changes in the temperature around the article can be detected from changes in the color of the dots formed by the droplets of the ink. The functional ink is not limited to the types and configurations of these materials, and any ink can be used as long as it changes color in response to environmental changes.

Next, the functions and operations of the main components that make up the printed image inspection device (IMG) shown in FIG. 3 will be explained.

<Image input unit 31>
The image input unit 31 according to the present embodiment has a function of capturing an image obtained by imaging a recognition target including a dot pattern with an image capturing device such as a camera. Although the image capturing device is not particularly limited, it is preferable that the dot area can be accurately recognized as pixel data as conditions for the lens and resolution.

On the other hand, due to recent technological advances, it is possible to perform a sufficient examination with a general-purpose imaging device. In particular, a camera terminal with a communication function can be preferably used because the communication function can be utilized when defining the dot pattern recognition conditions. Further, since an image photographing device having a print inspection function for inspecting print quality can be used, the mechanism of the present invention can be provided in the print inspection device.

<Dot pattern recognition unit 34A>
The dot pattern recognizing section 34A has a function of recognizing a dot pattern printed by a continuous ejection charge control type ink jet recording apparatus.

　FIGS. 5A and 5B show an example of the arrangement of dot patterns (dots) printed on the background of the printing surface to be recognized. A continuous-jet charge control type ink jet recording apparatus can print various characters, symbols, codes, and other print information, all of which are formed by arraying dot patterns.

When the ink that forms the dot pattern (dot) is a temperature-indicative ink that changes color in accordance with changes in temperature, as shown in FIGS. 5A and 5B, the color of the dots changes as the temperature changes. In the present embodiment, it is possible to determine whether or not the article (recognition target) has been exposed to environmental changes due to temperature by inspecting the color information of the dot patterns (dots) formed with such temperature-indicating ink. can be done. In this embodiment, temperature-indicating ink is used to inspect dot color information, but other functional inks can be used, and the present invention is not limited to this embodiment.

As the dot pattern formation method, a continuous ejection type charge control type ink jet recording apparatus was used, but the dot pattern formation method is not limited to this embodiment as long as the dot pattern has the same form. .

An image obtained by imaging a recognition target including a dot pattern is composed of a dot portion and a background portion without dots, as shown in FIG. 5A. The dot pattern recognition unit 34A needs to determine the difference in pixel color between a dot portion and a dot-free background portion when an image such as that shown in FIG. 5A is captured by an image capturing device.

Although this determination method is not particularly limited, a method of binarizing the intensity of the color of a pixel with a certain threshold value and distinguishing between a dot portion and a background portion without dots is often used. At this time, pixels of one of the binary colors can be recognized as pixel data of the dot portion.

When binarizing a dot portion and a background portion without dots clearly, the greater the color difference between the dot portion and the background portion without dots, the more the color difference can be determined. becomes easier. Automatic determination of the binarization threshold is also easy. Therefore, for example, if a dot pattern of black ink is formed on a white background and an image composed only of them can be captured, it is easy to recognize the pixels in the portion occupied by the dots in the image.

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

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

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 determining the quality of the printed characters. Furthermore, printed information obtained from printed characters can also be used as a criterion for determination results.

Next, a specific example of inspection using an actual printed image inspection device (IMG) will be described.

In the following description, a technique for improving recognition accuracy of pixel data of the dot portion is described, but this is a typical method, and the method of recognizing pixel data of the dot portion is not limited to this. .

(A). Recognition method of dot pattern by dot size regulation:
A dot pattern printed by a continuous-jet charge control type ink jet recording apparatus has a limited dot area to some extent. This is because the diameter of the nozzle of the continuous-jet charge control type ink jet recording apparatus is limited to several tens of micrometers to several hundreds of micrometers, which limits the volume of ink droplets.

Therefore, the area of dots formed by ink droplets landing on the recognition object depends on the surface tension of the recognition object, but is limited to some extent. Specifically, dots having a diameter of about 100 μm to 1000 μm are formed.

Therefore, if a dot of this size can be recognized in an image, the pixel data of the dot portion can be recognized regardless of the arrangement information of the dot pattern.

(B). Recognition method of dot pattern by regulation of dot size and distance between dots (Fig. 6):
When applying various image capturing devices, there is a possibility that the dot area cannot be accurately recognized in the image. As shown in FIG. 6, the dot pattern printed by the continuous ejection charge control type ink jet recording apparatus has a distance between the dots in addition to the area of the dots, and is arranged discretely to some extent.

It is possible to print dots next to each other, but if the distance between dots is short, the printing speed will be slower, and the ink will splatter due to contact between the inks, resulting in poor print quality. It becomes a problem.

Specifically, in the dot pattern, the distance between the centers of two dots is often about 1 to 5 times the diameter of the dots. Therefore, it is possible to recognize the pixel data of the dot portion by recognizing the portion where the distance between the center of the dot and the diameter of the dot between the two dots have this relationship in the image.

Also, when reading the color of the dots, if the dots are adjacent to each other and overlap occurs, the color of the dots will become darker, and it may not be possible to read the color accurately. Therefore, when recognizing the color of the dots, it is possible to preferably use a method of limiting the setting of printing with a certain distance between the dots as the printing method of the dots. This makes it easier to define the dot size and the distance between dots, and it is possible to improve the recognition accuracy of the pixel data of the dot portion.

(C). Regulation of the number of pixels of dots by camera lens, resolution, and focal length control (Fig. 7):
The problem is that the image capturing device such as a camera cannot accurately recognize the area of the dot in the image. Therefore, it is possible to define the number of pixels to some extent.

As shown in FIG. 7, once the lens, resolution, and focal length control method of the image capturing device are determined, when the focal length of the dot is adjusted automatically or manually during image capturing, the pixel length in the image is is determined to some extent, it is possible to define the area of an arbitrary number of pixels as the area of a dot.

(D). Regulation of roundness of dots (Fig. 8):
In printing by a continuous-jet charge control type ink jet recording apparatus, the formed dots are relatively clean circles. Based on this feature, it is possible to recognize the pixel data of the dot portion by defining the roundness of the dots in the image processing.

As shown in FIG. 8, the roundness is defined by "4π×the area of the dot/(the square of the perimeter of the dot)", and the closer it is to 1.0, the closer it is to a perfect circle. In the case of dots printed by a continuous ejection type charge control type ink jet recording apparatus, the dots can be recognized by specifying a value of 0.8 to 1.0.

If there is no pixel data indicating a relatively circular shape other than dots in the background of the image, pixels other than dots can be defined even if the value is defined in a relatively wide range such as 0.2 to 1.0. is likely to be recognized as pixel data of the dot portion.

By defining the roundness in a wide range to some extent, even a dot pattern in which the dots are connected to each other in the image and the roundness of the dots is low can be recognized as the pixel data of the dot portion. can.

(E). Dot periodicity definition (Fig. 9):
In printing by a continuous-ejection charge control type ink jet recording apparatus, since the dot size and the distance between dots are determined to some extent, a method of defining the periodicity of dots can also be used.

As shown in FIG. 9(a), when printing characters or symbols in which at least three or more dots are arranged in a line, image processing can be performed in one axial direction (indicated by white lines) in a two-dimensional image. On the other hand, there are places where periodicity can be seen in the strength and weakness of the color. The periodicity evaluation method is not particularly limited, but for example, as shown in (b), by evaluating the period and intensity of the power spectrum obtained by performing Fourier transform in the two-dimensional image, It is possible to recognize that there is an array in which dots are arranged along one axis in which high-cycle correlation is observed.

Furthermore, as shown in (c), it is possible to recognize the pixel data of the dot portion by evaluating the intensity of the color for the axis where the array of dots exists. The prescribed values for the period and intensity of the power spectrum need to be arbitrarily set in advance because the values vary depending on the intensity of the dot color, the number of dots to be inspected, and the like.

(F). Regulation of the number of dots:
For an image obtained by imaging a recognition target including a dot pattern, when recognizing the pixel data of the dot portion by image processing, the recognition accuracy can be improved by specifying the number of dots as a recognition condition.

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

In a continuous-jet charge control type inkjet recording apparatus, since some characters or symbols are usually printed, it is rare to print one or two dots, and at least 10 dots or more are formed. Probability is high. Therefore, by setting the number of dots to be 10 or more as a prescribed condition, printed dot patterns of all characters and symbols can be inspected without prescribing conditions.

However, there is a possibility that 10 or more dots cannot be recognized due to problems such as problems with the accuracy of photographing by the image capturing device and problems such as dots peeling off from the recognition object. There is no problem even if the number is specified.

By setting the number of dots close to the number of dots to be printed as a prescribed condition in advance, it is possible to recognize only the condition of the number of dots close to the dot pattern to be inspected, so the dot pattern to be inspected can be inspected with higher accuracy. can be recognized.

(G). Dot pattern rules:
In addition to the above-described method, it is also possible to define dot patterns such as characters and symbols to be printed by a continuous ejection charge control type ink jet recording apparatus. Similar to the print inspection apparatus, a method of storing image data of a dot pattern in which printed characters are normally formed in advance and recognizing the dot pattern based on the degree of matching with the data can also be used.

If the image capturing device has a print inspection function, color evaluation and print inspection can be performed at the same time. Since the dot pattern is defined in advance when performing the print inspection, this defined condition can be preferably used.

<Color information inspection section 34B>
The color information inspection section 34B, which is a feature of this embodiment, has a function of acquiring color information from the pixel data of the dot portion of the image obtained by the image input section 31. FIG.

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

For example, the color of the pixel in the central portion 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 largest color difference from the background color. Alternatively, the read color information of the dot portion may be averaged for all pixels of the dot portion and the value thereof may be evaluated.

In addition, it is sufficient that at least the dot portion is included, and evaluation may be performed by averaging the color information of the pixels including the dot portion and the background portion around the pixel including the dot portion.

Also, the method for evaluating the color of the 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. In addition to the CIE color space such as L ^* a ^* b ^* and L ^* C ^* h ^* , RGB color space, HSV color space, Munsell color space, etc. can be used as numerical information of color tone.

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

The method of calculating the correlation value between preset ink and reference color information data is not particularly limited. For example, when evaluating a color based on the average value of the RGB color space, the difference between the normal color and the inspected color is evaluated. By doing so, it is possible to confirm whether or not normal dots have been inspected. When the color of a dot changes depending on some environmental change like functional ink, only the ink of the color within the range of the predetermined amount of color change is recognized and the degree of color change is determined. can be done.

In color evaluation, measurement errors occur due to various factors such as the lighting environment, transmission and reflection of dots, reflection of the background color of the recognition target, the influence of curvature, and the reflection of shadows. If there is a large difference between the dot color and the background color, or if the amount of discoloration of the dots used to evaluate the discoloration of the functional ink is large, it is often possible to set a large judgment tolerance, resulting in a large measurement error. can also be calculated.

Also, as a method of reducing measurement errors in color evaluation, it is preferable to keep the lighting environment constant at all times. On the other hand, if the lighting environment is limited, it becomes difficult to shoot in various environments. Therefore, it is also possible to reduce the measurement error by inspecting the color of the background color and applying the correlation between the numerical value and the color of the dots to the inspection of the color information.

In that case, it is preferable to predefine the background color. In order to specify the background color, an image may be captured once under an appropriate lighting environment, or a specified value may be entered.

The method of evaluating the correlation value between the color of the dot portion and the color of the background is not particularly limited. A method of inspecting the color of the part and the color of the background color and evaluating the color of the dot based on the degree of change in the difference can be used.

The method of evaluating the background color is also not particularly limited. Pixel data other than the pixel data of the recognized dot portion may be used to evaluate the average value thereof, or the color of pixels in a range separated by a certain distance from the dot portion may be evaluated. Among the pixel data other than the pixel data, the value with the largest color difference from the dot color may be evaluated.

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

The judgment method is not particularly limited, but the judgment criteria must be defined in advance. For example, when a color is evaluated based on the average value of the RGB color space, if the average value of the RGB color space is a certain constant value, it is determined as A, and if it is another constant value, it is determined as B. . Of course, multiple stages of determination are also possible.

For example, when inspecting a dot pattern formed by printing functional ink for the purpose of managing the quality of a recognition object, (a) before heating (0 minutes) and after heating (10 minutes) in FIG. The dots change color depending on the environmental temperature, as shown in (b) showing the minute). Although it was "blue" in FIG. 10(a), it has changed to "yellow" in FIG. 10(b). Then, as shown in (c), it is compared with the threshold "(R+G+B)/3=130", and the quality state of the recognition object is "normal", "warning", or "abnormal" from the color evaluation result. can be determined to be exposed to

It is also possible to display judgment results that differ from the judgment criteria for color evaluation, such as dot pattern recognition errors and display of the number of dots. When the function of the print inspection device is provided, it is also possible to display the print inspection result and also to display the information of read characters, symbols, and codes.

The image capturing device, which is the image input unit 31, the correlation value calculation unit 34C, and the ink condition determination unit 34D according to the present embodiment may be executed a plurality of times for one dot pattern, or may be used in a plurality of units. In this case, a camera terminal with a communication function or the like can be preferably used. Thus, one of the features is that the image capturing device is a camera terminal with a communication function.

When the dot pattern is inspected a plurality of times by the same print image inspection device or different print image inspection devices, any of the image data obtained during the inspection, the image inspection data, and the judgment data One of the features is that the data is shared and used for the second and subsequent inspection methods, inspection results, and judgment results.

Even if the camera terminal does not have a communication function, image data, calculation data, judgment data, etc. can be saved and shared by multiple image capturing devices using a terminal with a communication function. For example, a print inspection device inspects the color information and print information of the dot pattern of the functional ink. It is possible to inspect the direction, etc.

In this case, it is possible to use the inspection result of the first print inspection device as the second inspection method and criteria for the camera terminal with a communication function. For example, the difference in color information between the first inspection and the second inspection may be calculated, or the first printed information (lot number, date of manufacture, etc.) may be used as the inspection conditions for the second dot pattern. You can add

In this way, once the image inspection is performed, the dot pattern arrangement information and the ink color information data are stored, and when the image inspection is performed again, the previously set ink color information data in the correlation value calculation unit is stored. As another feature, the correlation between dot pattern arrangement information and ink color information data is calculated.

Also, it is possible to inspect the date of manufacture, which is the printed information for the first time, and determine that it is abnormal if a certain period of time has passed since the date of manufacture at the time of the second inspection. That is, environmental information (time, weather, location information, etc.) at the time of inspection can be added to the determination result. In this way, it is one of the features that environmental information such as the time, place, temperature, etc. at the time of inspection is used as criteria for determination results.

[Preparation of dot pattern using functional ink]
An inkjet recording apparatus (inkjet printer UX type manufactured by Hitachi Industrial Equipment Systems Co., Ltd.) was filled with temperature-indicating ink that changes color according to heat history, and printed on a glass substrate. The printed dots printed on the substrate were "blue" in the initial state. When the printing base material was allowed to stand in an environment of 70° C., it was confirmed visually that the color gradually began to develop yellow after 1 minute, and that the color developed completely yellow after 10 minutes. With respect to this printing base material, the examination of dot color was examined.

[Dot pattern color inspection]
FIG. 10 shows how the color of the printed dots produced changes due to heating. A smartphone (manufactured by HUAWEI, P8lite) was used as an image capturing device, and a recognition target object including a dot pattern was captured using an autofocus function. An attempt was made to binarize the photographed image using image processing software (ImageJ) and to detect the position of the dot pattern.

As the dot pattern detection conditions, the area of the pixel of the dot depending on the diameter of the dot is 50 to 200, the roundness of the dot is 0.2 to 1.0, and the number of dots is 40 to 60. detected the data. As shown in FIG. 11(a), it can be seen that 52 printed dots have been inspected.

By this method, the color of dots before heating (b) (0 minutes) and after heating (c) (10 minutes) was evaluated by the average values of RGB for the detected dot portions. The evaluation results are also shown in FIG. As shown in FIG. 11, it can be seen that the change in dot color can be quantified.

Of these, as a criterion, as shown in FIG. 10, when the average value of RGB is less than 130, it is indicated as before heating, and when it is 130 or more, it is indicated as after heating. From this result, it was determined that the sample was not heated until 0 to 5 minutes after heating to 70° C., and that the sample was determined to be after heating after 5 to 10 minutes.

As described above, the printed image inspection apparatus according to the present embodiment is used to inspect the color of the dot pattern formed by the continuous ejection type charge control type inkjet recording apparatus, and the printed image inspection to determine the state of the ink from the color information. I was able to check the device.

In this way, the print inspection device (PID) and smart phone (SMT) that become the print image inspection device (IMG) can be accessed from factories, shipping areas, stores, customers, etc., so that color information based on environmental changes can be diversified. can be inspected by a simple inspection method. If a smart phone (SMT) is used as a printed image inspection device (IMG), inspection can be easily performed at any time and at any place.

Furthermore, the function of the print image inspection device (IMG) is given to the management server (MSV), and the captured image is transferred from the smartphone (SMT) or small portable terminal to the management server (MSV) It is also possible to carry out an inspection. This is particularly effective when managing heat histories and the like in the course of distribution of many products in a store.

It should be noted that the present invention is not limited to the several embodiments described above, and includes various modifications. The above embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the described configurations. Moreover, 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. Other configurations can be added, deleted, or replaced with respect to the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 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... Deflecting electrode, 20 Print target 21 Gutter 30 Input unit 31 Image input unit 32 Output unit 33 Communication unit 34 Processing unit 34A Dot pattern recognition unit 34B Color information inspection unit 34C Correlation value calculation unit 34D Ink state determination unit 34E Read data acquisition unit 35 Storage unit 35A Dot pattern storage unit 35B Color information storage unit 35C Correlation value information storage unit 35D Ink State memory.

Claims

A printed image inspection apparatus that acquires color information of a dot portion of an image obtained by imaging a recognition target in which a dot pattern is arranged, and outputs a judgment result based on the color information,
an image input unit that captures the image obtained by imaging the recognition target including the dot pattern;
a dot pattern recognition unit that determines matchability with the 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 value calculation unit that calculates a correlation value between the color information data of the color information and preset reference color information data of the ink;
and 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.
The printed image inspection device according to claim 1,
A printed image inspecting apparatus, wherein the dot pattern is formed by a continuous ejection charge control type ink jet recording apparatus.
The printed image inspection device according to claim 2,
The printed image inspecting apparatus, wherein the dot pattern is a dot pattern formed with functional ink that changes color according to environmental changes.
The printed image inspection device according to claim 2,
A printed image inspection apparatus, wherein the dots of the predetermined standard dot pattern have a dot diameter of 100 nm to 1000 nm.
The printed image inspection device according to claim 2,
The dot pattern recognizing unit pre-stores information on a lens, resolution, and focal length control method of an image capturing device for photographing the recognition target on which the dot pattern is arranged, and pre-defines the dots from the stored information. A printed image inspection device characterized by recognizing the area of dots in a pattern.
The printed image inspection device according to claim 2,
A printed image inspecting apparatus, wherein, in the predetermined reference dot pattern, the roundness of dots is 0.2 or more.
The printed image inspection device according to claim 2,
A printed image inspecting apparatus, wherein in the predetermined reference dot pattern, the distance between the centers of two dots is 1 to 3 times the diameter of the dots.
The printed image inspection device according to claim 2,
A printed image inspection apparatus, wherein at least three dots in the predetermined reference dot pattern have periodicity with respect to one axial direction.
The printed image inspection device according to claim 2,
A printed image inspecting apparatus, wherein the number of dots is defined as a predetermined number in the predetermined reference dot pattern.
The printed image inspection device according to claim 2,
A printed image inspecting apparatus, wherein arrangement information of said dot pattern is defined as predetermined arrangement information in said dot pattern of a predetermined reference.
The printed image inspection device according to claim 2,
The color information acquisition unit acquires the color information from the pixel data of the dot portion of the image and also acquires the color information from the pixel data of the background portion of the image,
The printed image inspection apparatus, wherein the correlation value calculation unit calculates the correlation value of the color information data of the background color of the dot pattern set in advance in addition to the color information data of the ink.
The printed 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 at the time of inspection is shared, and used for the second and subsequent inspection methods, inspection results, and judgment results. A printed image inspection device characterized by:
A printed image inspection method for acquiring color information of a dot portion of an image obtained by imaging a recognition target in which a dot pattern is arranged, and outputting a determination result based on the color information, comprising:
an image input step of capturing the image obtained by imaging the recognition target including the dot pattern;
a dot pattern recognition step of determining conformity with the dot pattern of a predetermined reference;
a color information acquisition step of acquiring color information from pixel data of the dot portion of the image;
a correlation value calculating step of calculating a correlation value between the color information data of the color information and preset reference color information data of the ink;
A printed image inspection method, characterized by executing an ink condition determination step for determining the condition of the ink to be recognized from the correlation value obtained in the correlation value calculation step.
The printed 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 performed again, the arrangement information of the previous dot pattern and the correlation with the color information data of the ink are used as the preset color information data of the ink in the correlation value calculation step. A printed image inspection method characterized by calculating a value.