Image processing device, method for processing image, and program

Abstract

To solve such the problem that inspection accuracy for an image on a recording medium constituted of a plurality of layers deteriorates.SOLUTION: An image processing device includes: acquisition means for acquiring a read image that is acquired by reading a printed recording medium; correction means for correcting colors of the read image and colors of a reference image to be a reference of inspection on the basis of a target value corresponding to a combination of a printing layer and a substrate layer constituting the printed recording medium; and inspection means for inspecting the printed recording medium on the basis of a difference between the corrected read image and the corrected reference image.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a technique for inspecting print results. [Background technology]

[0002] When forming an image on a recording medium by a printing device, for example, stains may occur due to the adhesion of color materials such as ink or toner to unintended locations, or color loss may occur due to insufficient color materials being attached to locations where an image is to be formed, making it impossible to reproduce the intended color. Since so-called printing defects such as stains and color loss reduce the quality of printed matter, it is necessary to inspect for the presence or absence of printing defects. As a system for inspecting the presence or absence of printing defects, for example, there is a printing system that reads a printed matter output by a printing device with a camera or a line sensor of a scanner, and automatically inspects whether printing is performed normally based on the read image. In such a printing system, the presence or absence of printing defects in the inspection target can be detected based on the difference between a reference image showing image data of a defect-free printed matter and a read image showing image data of the printed matter to be inspected. However, in the inspection of printed matter composed of multiple layers such as label paper, if the surface base material of the top layer on which printing is performed is a transparent material or a thin material, there is a problem that the color of the release paper or backing paper that is the layer below is visible, making it impossible to properly inspect the printed matter for defects. Hereinafter, the upper layer, such as a transparent film or a seal paper used as a surface substrate, will be referred to as the print layer, and the lower layer, such as a glassine paper or a wood-free paper used as a release paper or a mount, will be referred to as the base layer. Regarding the inspection of label paper consisting of such multiple layers, Patent Document 1 discloses a method for comparing a color target value calculated based on the characteristics of the print layer and base layer that compose the recording medium with a color measurement value obtained by reading an image on the recording medium. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7225887 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 describes a method of comparing color target values ​​and measured values ​​for a gradation pattern, which can detect macro defects such as color variations, but cannot detect minute defects such as point-like or linear stains or scratches. SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to improve the inspection accuracy of an image on a recording medium that is made up of multiple layers. [Means for solving the problem]

[0005] An image processing device according to one aspect of the present disclosure is characterized in having an acquisition means for acquiring a read image obtained by reading a printed recording medium, a correction means for correcting the color of the read image and the color of a reference image that serves as a reference for inspection based on a target value corresponding to a combination of a printing layer and a base layer that constitute the printed recording medium, and an inspection means for inspecting the printed recording medium based on the difference between the corrected read image and the corrected reference image. Effect of the Invention

[0006] According to the present disclosure, it is possible to improve the inspection accuracy of an image on a recording medium that is composed of multiple layers. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 illustrates an example of the configuration of a printing system. [Diagram 2] 1 is a block diagram showing an example of a functional configuration of an image processing device; [Diagram 3] 13 is a flowchart showing a flow of an inspection process. [Figure 4] FIG. 13 is a diagram showing an example of a UI screen. [Diagram 5] 11A and 11B are diagrams illustrating an example of the relationship between a print layer, a base layer, and a target value. [Figure 6] 10 is a flowchart showing a detailed flow of a process for correcting the color of an inspection image. [Figure 7] 10 is a flowchart showing a detailed flow of an inspection process. [Figure 8] 13 is a diagram showing an example of the relationship between a print layer, a base layer, a backing, and a target value. FIG. [Figure 9] FIG. 11 is a diagram for explaining a method of calculating a target value. [Figure 10] 10 is a flowchart showing a detailed flow of an inspection process. [Figure 11] 13 is a diagram showing an example of the relationship between a special layer (top), a printed layer, a special layer (bottom), a base layer, a backing, and target values. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the embodiments will be described in detail with reference to the drawings. Note that the components described in the following embodiments are merely examples, and the configuration and various conditions of the device to which the present disclosure is applied can be appropriately modified or changed within the scope of the gist of the present disclosure, and are not limited to the following embodiments. For example, the dimensions, materials, shapes, and relative positions of the components described in the following embodiments can be appropriately changed depending on the configuration and various conditions of the device to which the present disclosure is applied, and unless otherwise specified, the present disclosure is not limited to the following embodiments. Furthermore, in the drawings, the same reference numbers are given to the same or similar configurations, and duplicated explanations are omitted. In addition, each process (step) in the flow chart is represented with an "S" at the beginning.

[0009] <<Embodiment 1>> In this embodiment, a target value for correcting the color of an inspection image based on a combination of a printing layer and a base layer is calculated, and the presence or absence of a printing defect is detected using the inspection image corrected based on the calculated target value.

[0010] (Printing system configuration) 1 is a diagram showing an example of the overall configuration of a printing system. The printing system is a system that outputs and inspects printed matter, and includes an image processing device 100, a printing server 180, and a printing device 190 according to this embodiment.

[0011] The printing server 180 has a function of generating a print job for a document to be printed, and inputting the generated print job to the printing device 190. The printing server 180 may be communicably connected to a plurality of external devices (not shown) via a network, and may receive requests for generating print jobs, print data, and the like from these external devices.

[0012] The printing unit 194 of the printing device 190 forms an image on roll paper (recording medium) based on a print job input from the printing server 180. The recording medium is, for example, label paper. The printing layer of the label paper is made of a transparent film or a seal paper, and the base layer of the label paper is made of a release paper or a backing paper. As the printing method in the printing unit 194, known printing methods such as offset printing, electrophotography, and inkjet printing can be applied. In this embodiment, the case where the electrophotography method is adopted will be described as an example, but is not limited to this. The printing device 190 has a paper feed unit (unwinding unit) 191, and the user sets (stores) the roll paper in the paper feed unit 191 in advance. When a print job is input, the printing device 190 forms an image specified by the print job on the front or both sides of the roll paper while transporting the roll paper set (stored) in the paper feed unit 191 along the transport path 192, and transports the roll paper on which the image has been formed to the image processing device 100.

[0013] The image processing device 100 performs an inspection process to check for printing defects on the printed roll paper transported from the printing device 190. In other words, the image processing device 100 functions as an inspection processing device for printed matter. The image processing device 100 has a paper discharge section (winding section) 193, and winds up the printed roll paper that has been inspected. The recording medium to be inspected is obtained by the printing device 190 forming an image on the recording medium, and is transported through a transport path 192 inside the printing device 190.

[0014] The image processing device 100 internally comprises a CPU 101, a RAM 102, a ROM 103, and an image reading device 105. The image processing device 100 also comprises an interface (I / F) 106 with a printing device 190, a general-purpose interface (I / F) 107, a user interface (UI) panel 108, and a main bus 109. The image processing device 100 further comprises a conveying path 110 connected to a conveying path 192 of the printing device 190, and a paper discharge unit (winding unit) 193 that winds up and stores printed roll paper that has passed through the conveying path 110.

[0015] (Hardware configuration of image processing device) The image processing device 100 can be realized by a computer including a processor and a memory. For example, the CPU 101 is a processor that controls the entire image processing device 100. The RAM 102 functions as a main memory, a work area, etc. of the CPU 101. The RAM 102 temporarily stores applications executed by the CPU 101, or data used in image processing. The ROM 103 stores a group of programs executed by the CPU 101. A processor such as the CPU 101 can realize the functions of each part by executing a program stored in a memory such as the RAM 102 or the ROM 103. The processor such as the CPU 101 can also control each module in the image processing device 100 as necessary. The image processing device 100 may be configured by a plurality of processing devices connected via a network, for example.

[0016] The image reading device (scanner) 105 reads the printed recording medium (roll paper) transported from the printing device 190 on the transport path 110 and acquires the image data. The transport path 110 serves as the background when the image reading device 105 reads the image on the printed recording medium, and is therefore configured to have a color (e.g., black) that is easily distinguishable from the recording medium in the image.

[0017] The printing device I / F 106 is connected to the printing device 190, and the image processing device 100 can communicate with the printing device 190 through the printing device I / F 106. For example, the image processing device 100 can synchronize with the printing device 190 and exchange operation statuses with each other via the printing device I / F 106. The general-purpose I / F 107 is a serial bus interface such as USB or IEEE1394, and allows a user to take out data such as logs and import some data into the image processing device 100.

[0018] The UI panel 108 is, for example, a liquid crystal display (display unit), and functions as a user interface for the image processing device 100, displaying the current status and settings of the image processing device 100 and conveying them to the user. The UI panel 108 may also be configured to receive instructions from a user by using a touch panel type liquid crystal display and operating displayed buttons by the user. In other words, the UI panel 108 may be configured to receive selections made by user operations.

[0019] The main bus 109 is a bus that connects each unit of the image processing device 100 and exchanges data, etc. Each unit of the image processing device 100 and each internal part of the printing system can be operated by instructions from the CPU 101 via the main bus 109.

[0020] While the printed recording medium output from the printing device 190 is conveyed along the conveying path 110, the image processing device 100 performs an inspection process to check for defects on the printed recording medium based on image data of the recording medium acquired by the image reading device 105. The judgment result of the inspection process is stored in the RAM 102 or the ROM 103.

[0021] (Functional configuration of image processing device) 2 is a block diagram showing an example of the functional configuration of the image processing device 100. The image processing device 100 includes a reference image acquisition unit 201, a read image acquisition unit 202, a paper information acquisition unit 203, an inspection information acquisition unit 204, a target value calculation unit 205, an image correction unit 206, a defect determination unit 207, and a display unit 208.

[0022] The reference image acquisition unit 201 acquires original data, which is the original data of the printed matter, by reading it into the RAM 102. The read image acquisition unit 202 acquires image data of a read image of a printed recording medium, which is an inspection target, on which printing is performed by the printing device 190. The acquired image data is stored in the RAM 102. In this embodiment, the read image acquisition unit 202 acquires image data obtained by the image reading device 105 reading the printed recording medium on the conveying path 110. The paper information acquisition unit 203 acquires paper information indicating the film used for the printing layer and the backing paper used for the base layer as information related to the layer structure of the paper, based on the user's operation acquired via the UI panel 108. The inspection information acquisition unit 204 acquires information related to the print job and the inspection level related to the inspection settings, based on the user's operation acquired via the UI panel 108.

[0023] The target value calculation unit 205 calculates a target value for correcting color data of the inspection image based on the paper information acquired by the paper information acquisition unit 203. The image correction unit 206 performs color correction processing based on the target value calculated by the target value calculation unit 205 for the images acquired by the reference image acquisition unit 201 and the read image acquisition unit 202. The defect determination unit 207 compares the reference image (corrected reference image) color-corrected by the image correction unit 206 with the read image (corrected read image), and determines the presence or absence of a defect based on the compared data, etc. The display unit 208 displays a UI screen on the UI panel 108 to notify the user of information and to allow the user to input information required for processing.

[0024] (Overview of inspection process) FIG. 3 is a flowchart showing the flow of processing executed by the image processing device 100.

[0025] In S301, the image processing device 100 displays a UI screen on the UI panel 108 to receive instructions from the user so that the user can input information necessary for the inspection, and acquires paper information and inspection information based on operations from the user, etc.

[0026] (UI screen) 4 is a diagram showing an example of a UI screen displayed in S301. Note that the display window 440 of the UI screen 400 is displayed in S310.

[0027] The UI screen 400 has a field 410 for setting paper information, a field 420 for setting inspection information, an inspection execution button 430, and a display window 440 for displaying the judgment result (inspection result).

[0028] The paper information setting field 410 has a print layer selection field 411 and a base layer selection field 412. The print layer selection field 411 is in a pull-down menu format, and for example, from among a plurality of print layers such as film 1, film 2, and film 3, a print layer constituting the recording medium to be inspected can be selected. The base layer selection field 412 is in a pull-down menu format, and for example, from among a plurality of base layers such as none, mount 1, and mount 2, a base layer constituting the recording medium to be inspected can be selected. Note that information indicating the print layer selected in the print layer selection field 411 and the base layer selected in the base layer selection field 412 is acquired as paper information by the paper information acquisition unit 203. The paper information setting field 410 can also be said to be an area for the user to specify the print layer and the base layer. In this embodiment, the selection fields for specifying the print layer and the base layer are separate, but it is also possible to hold combinations of print layers and base layers and specify these combinations. In addition, if the paper information to be used for the inspection is not included in the preset values ​​for the printing layer or base layer, a separate UI screen for custom settings may be provided so that the user can register the paper to be used as a preset value and specify the paper information.

[0029] The inspection information setting field 420 has an inspection job selection column 421 and an inspection level selection column 422. The inspection job selection column 421 is in the form of a pull-down menu, and is a menu for selecting a job including an inspection to be performed from among a plurality of jobs, such as job 1 and job 2. The inspection level selection column 422 is in the form of a pull-down menu, and is capable of selecting a level of inspection to be performed from among a plurality of inspection levels, such as inspection level 5 (high)·inspection level 1 (low). The inspection level is associated with a processing parameter required for detecting defects for each inspection level according to the size and contrast of defects to be detected, and defects are detected according to the inspection level selected by the user. In this embodiment, five inspection levels are held, and the higher the inspection level, the lower the contrast and the smaller the size of defects to be detected, and the lower the inspection level, the higher the size and size of defects to be detected. Information indicating the job selected in the inspection job selection column 421 and the inspection level selected in the inspection level selection column 422 is acquired as inspection information by the inspection information acquisition unit 204. The designated inspection job is held in the RAM 102. The specified inspection level is stored in the RAM 102 .

[0030] The execute inspection button 430 is a button for executing the inspection process. When the execute inspection button 1105 is pressed by the user, the inspection process is executed based on the information selected in the print layer selection field 411, the base layer selection field 412, the inspection job selection field 421, and the inspection level selection field 422. The type of defect determined by the inspection process, position information of the defect on the roll paper, and the like are stored in the RAM 102. The display window 440 displays the image of the inspection target, a defect map, and the determination results. The display window 440 displays information on the type and position of the defect detected by the inspection process together with the corresponding image area.

[0031] The display window 440 has an area 450 for displaying a read image, an area 460 for displaying an inspection image (enlarged display) determined to be defective, and an area 470 for displaying a defect map (enlarged display). The area 450 displays a read image 452 of a printed recording medium on which an image 451 to be inspected is formed. The area 450 also displays a dashed line 455 for highlighting an image 454 having a detected defect 453. The area 460 enlarges and displays an image corresponding to the image 454 having the defect 453. That is, the area 460 displays an image 463 having a defect 462, and a balloon 464 including "defect type: point defect" 465 and "position information: (X, Y)" 466. Note that, if a linear defect is detected, "defect type: linear defect" is displayed instead of "defect type: point defect". Note that, if a point defect and a linear defect are detected, "defect type: point defect, linear defect" is displayed instead of "defect type: point defect". The position information indicates an XY coordinate position with the origin being the upper left vertex of the read image 452. Area 470 displays a defect map 471, which is a binarized image of the inspection image (enlarged display) and in which defects are colored white 473 and other parts are colored black 472.

[0032] In S302, the reference image acquisition unit 201 acquires document data, which is the original data of the printed matter, or a read image, and stores it in the RAM 102. The read image is acquired by the image reading device 105 reading the roll paper on the conveying path 110, and is stored in the RAM 102. Note that the image reading device 105 generates a read image by reading the roll paper, but it is also applicable to a case where an image acquired by another device is used. For example, a read image obtained by a device other than the image reading device 105 may be stored in an auxiliary storage device (not shown). In this case, the read image acquisition unit 202 can acquire the read image from the auxiliary storage device. In addition, when the document data is used as the reference image, overdetection occurs due to a difference in image characteristics from the read image, so in this embodiment, a correction process is performed on the document data for color reproduction characteristics and thin line reproduction characteristics as image characteristics.

[0033] In color reproduction correction processing, correction is performed by referencing a lookup table (LUT) that describes the correspondence for converting the four-channel CMYK data into the three-channel RGB data of the scanned image data for each printing device characteristic, paper, and output condition. The LUT is created and stored in advance.

[0034] In the thin line correction process, a thin line chart is output in advance, the output thin line chart is read, and correction data relating to the reproduction of thin lines in the original data and the read image is calculated. In this embodiment, a filter coefficient for matching the line width with the read image based on the line profile of the thin line, and a filter coefficient for correcting edge blurring during scanning are calculated, and a reference image is generated by applying these two types of correction processes to the original data. In addition, a process is performed to convert the resolution of the original data to match the image size and resolution of the read image used during inspection.

[0035] In S303, the paper information acquisition unit 203 acquires paper information to be used for printing. That is, the paper information acquisition unit 203 acquires the information set in the print layer selection field 411 and the base layer selection field 412 as the paper information.

[0036] In S304, the examination information acquisition unit 204 acquires an examination job. That is, the examination information acquisition unit 204 acquires information selected in the examination job selection field 421 as the examination job.

[0037] In S305, the inspection information acquisition unit 204 acquires an inspection level. The inspection information acquisition unit 204 refers to the information selected in the inspection level selection field 422, and acquires processing parameters related to the contrast and size of a defect associated with the inspection level as the inspection level.

[0038] In S306, the read image acquisition unit 202 acquires a read image obtained by the image reading device 105 reading the roll paper on the conveying path 110. The acquired read image is stored in the RAM .

[0039] In S307, the target value calculation unit 205 calculates a target value for correcting the colors of the reference image and the read image used as the inspection image. In this embodiment, the pixel value of the paper white is set as the target value as the correction target according to the combination of the print layer and the base layer, and correction processing is performed so that the pixel values ​​of the paper white of the reference image and the read image reproduce the target value.

[0040] <Target value> 5 is a diagram showing an example of a file for managing the relationship between a print layer, a base layer, and a target value. A file 500 shows the relationship between a print layer 520, a base layer 530, and a target value 540.

[0041] In the case of number “1” 511, the combination of “Film 1 (transmittance 60%)” of the printed layer 520 and “Backing 1 (transmittance 1%)” of the base layer 530 is linked to (R,G,B) “(230,230,230)” as the target value 540. In the case of number “2” 512, the combination of “Film 2 (transmittance 65%)” of the printed layer 520 and “Backing 2 (transmittance 1%)” of the base layer 530 is linked to (R,G,B) “(228,228,228)” as the target value 540. In the case of number “3” 513, the combination of “Film 3 (transmittance 75%)” of the printing layer 520 and “Backing 3 (transmittance 10%)” of the base layer 530 is linked to (R,G,B) “(220,220,220)” as the target value 540.

[0042] In the case of number "4" 514, the combination of "Film 3 (transmittance 75%)" of the printed layer 520 and "Backing 4 (transmittance 30%)" of the base layer 530 is linked to (R, G, B) "(210, 210, 210)" as the target value 540. In the case of number "5" 515, the combination of "Film 4 (transmittance 80%)" of the printed layer 520 and "Backing 4 (transmittance 30%)" of the base layer 530 is linked to (R, G, B) "(208, 208, 208)" as the target value 540. It can be said that the target values ​​are set so that the color brightness value becomes higher as the transmittance of the printed layer and the transmittance of the base layer become smaller.

[0043] As shown in FIG. 5, the RGB values ​​of paper white are described in the file as target values ​​according to the combination of the print layer and the base layer, and the RGB values ​​are values ​​obtained by reading the paper white in advance with a reading device. The target value calculation unit 205 acquires the file and calculates the target value by referring to the correspondence between the target value and the combination of the print layer and the base layer. In this embodiment, the pixel value of the paper white is set as the target value, but the characteristics of the entire print color may be set as the target value in the form of a LUT (lookup table) without being limited to the paper white. In addition, if the combination of the print layer and the base layer specified by the user is not in the file, a database that can list the paper characteristics may be stored separately, and the database may be referenced and the target value of the paper with the closest characteristics may be used instead. Alternatively, the target value may be calculated by performing an interpolation operation from the target values ​​of the paper with the closest characteristics.

[0044] In S308, the image correction unit 206 performs color correction on the inspection image based on the target value calculated in S307. The details of the process of the image correction unit 206 will be described later.

[0045] In S309, the defect determination unit 207 determines the presence or absence of a defect using the inspection image corrected in S308. Details of the process of the defect determination unit 207 will be described later.

[0046] In S310, the display unit 208 displays the judgment result obtained in the process of S309 in the display window 1106. The display window displays the image used in the inspection (the read image obtained in one read). If the inspection image has a defect, the display window displays the inspection image, an enlarged image of the inspection image, and a defect map (enlarged image) corresponding to the enlarged image of the inspection image. The defect map is a map that indicates the defect coordinate position when the inspection image (enlarged image of the inspection image) has a defect. The defect map is an image file of the same vertical and horizontal size as the reference image and the read image. If there is a defect, for example, a pixel value of RGB=(255,255,255) is stored in the corresponding coordinate position, and if there is no defect, a pixel value of RGB=(0,0,0) is stored in the coordinate position. Note that the top left vertex of the read image is the origin. In this embodiment, if there is no defect, all pixel values ​​are stored as 0. If there is a point-like defect, a pixel value of RGB=(255,0,0) is stored in the corresponding coordinate position. If there is a linear defect, a pixel value of RGB=(0,255,0) is stored at the corresponding coordinate position. In this embodiment, different pixel values ​​are stored in the cases where there is no defect, where there is a point defect, and where there is a linear defect, but this is not limiting and different pixel values ​​may be stored.

[0047] <Details of color correction process for inspection images (S308)> 6 is a flowchart showing a detailed flow of the inspection image color correction process (S308). The process of correcting the color of the inspection image is executed by the image correction unit 206.

[0048] In S601, the image correction unit 206 acquires the reference image acquired in S302. In S602, the image correction unit 206 acquires the read image acquired in S306.

[0049] In S603, the image correction unit 206 acquires pixel values ​​of the paper white of the reference image and the read image. For example, the image correction unit 206 detects blank areas in each of the reference image and the read image using a known technique, and acquires pixel values ​​of the paper white from the detected blank areas.

[0050] In S604, the image correction unit 206 calculates a gain value for image correction based on the pixel value acquired in S603 and the target value acquired in S307. In this embodiment, the gain value for correcting the luminance of the image is calculated by the following formula (1) using only the G channel as the pixel value. In formula (1), Gt indicates the G channel value of the target value acquired in S307, and G0 indicates the G channel value of the pixel value acquired in S603. Gain(G) (gain value) is calculated for each of the reference image and the scanned image.

[0051] gain(G) = Gt / G0 (1) In this embodiment, only the gain value is calculated from the G channel value, but it is also possible to calculate and store gain values ​​for the R channel and B channel separately, and perform not only brightness correction but also white balance correction in the correction process of S605 described below.

[0052] In S605, the image correction unit 206 corrects the pixel values ​​of the reference image and the read image using the gain value calculated in S604 according to the following formula (2). (R, G, B) are pixel values ​​of the image before correction, and (R', G', B') are pixel values ​​of the image after correction, and correction is performed for pixel values ​​of all coordinates. For example, assume that the pixel value ((R, G, B) = (100, 100, 100)) of the paper white of the inspection image is obtained under the condition No. 1 shown in FIG. 5, and the gain value (correction gain value) gain(G) for image correction is calculated as 230 / 100 = 2.3 according to the above formula (1). In this case, the inspection image is corrected using the calculated gain(G) of 2.3. That is, the image correction unit 206 corrects the color of the reference image and the color of the read image.

[0053] R' = R × gain(G) G' = G × gain(G) (2) B' = B × gain(G) Although the above is a process for correcting the luminance of an image, the white balance may be corrected not only by luminance but also by using the gain value of each channel as shown in the following formula (3).

[0054] R' = R × gain(R) G' = G × gain(G) (3) B' = B × gain(B)

[0055] In S606, the image correction unit 206 stores the corrected reference image and the corrected read image obtained in S605 in the RAM 102. When the process of S606 ends, the flow shown in FIG.

[0056] <Details of inspection process (S309)> 7 is a flowchart showing a detailed flow of the inspection process (S309). Note that the inspection process is executed by the defect determination unit 207.

[0057] In S701, the defect determination unit 207 acquires the corrected reference image obtained in S308. In S702, the defect determination unit 207 acquires the corrected read image obtained in S308.

[0058] In S703, the defect determination unit 207 extracts alignment reference points that represent image features used when aligning the corrected reference image and the corrected read image. The reference points are extracted using a known image feature point extraction method such as SIFT or SURF.

[0059] In S704, the defect determination unit 207 aligns the corrected reference image and the corrected read image based on the feature points extracted in S703. In this embodiment, affine transformation is used as the geometric transformation parameters used for alignment, but the transformation is not limited to this. For example, the images may be aligned using other geometric transformation parameters such as projective transformation.

[0060] In S705, the defect determination unit 207 calculates the difference (difference value) between the aligned and corrected reference image and the corrected read image.

[0061] In S706, the defect determination unit 207 determines that a pixel whose calculated difference (difference value) is greater than a predetermined threshold is a defective pixel. In this embodiment, a contrast threshold value for the difference and a dot size and a line size are stored for each inspection level, and the presence or absence of a defect is determined based on the contrast of the difference and the shape size.

[0062] As described above, in this embodiment, a target value for correcting the color of an image is calculated based on the combination of the print layer and the base layer that constitute the printed recording medium, and the color of the image used for the inspection is corrected based on the calculated target value. This makes it possible to prevent poor alignment and deterioration of inspection performance caused by a decrease in the brightness of the read image.

[0063] <<Embodiment 2>> In this embodiment, a mode of calculating a target value of an inspection image based on a combination of a printing layer, a base layer, and a backing material (hereinafter referred to as a backing) when reading by a reading device will be described. Specifically, when the printing layer and base layer are made of a thin material and the backing is black, the brightness of the read image is lowered and acquired darker than the actual appearance. When the brightness of the read image is lowered, the brightness and contrast of the image are insufficient when performing alignment and defect detection processing, and image feature points required for alignment are not properly extracted. In addition, problems such as a decrease in the accuracy of defect detection occur. A mode of correcting this will be described. Note that the operation of the target value calculation unit 205, which is a difference from the first embodiment, will be described, and other processing will be omitted because it is the same as the first embodiment.

[0064] <Operation of target value calculation unit 205> FIG. 8 is a diagram showing an example of a file referred to by the target value calculation unit 205 according to the present embodiment. In the file 800, a target value 850 corresponding to a color combination of the print layer 820, the base layer 830, and the backing 840 is described as a table. That is, the file 800 can be said to show the relationship between the print layer 820, the base layer 830, the backing 840, and the target value 850. The target value 850 is a pixel value of the paper white of the read image acquired by the reading device as in the first embodiment, and is stored in a file in advance according to the combination of the paper information and the backing. Note that the backing color information is acquired from information specified in the backing setting unit by adding a new backing setting unit to the UI screen displayed in S301.

[0065] In number "1" 811, the combination of "Film 1 (transmittance 60%)" of the print layer, "Paper 1 (transmittance 1%)" of the base layer, and "Black (reflectance 0.5%)" of the backing is linked to the target value (R,G,B) of "(230,230,230)." In number "2" 812, the combination of "Film 2 (transmittance 65%)" of the print layer, "Paper 2 (transmittance 1%)" of the base layer, and "Black (reflectance 0.5%)" of the backing is linked to the target value (R,G,B) of "(228,228,228)." In the case of number “3” 813, the combination of the printing layer “Film 3 (transmittance 75%)”, the base layer “Backing 3 (transmittance 10%)”, and the backing “Black (reflectance 0.5%)” is linked to the target value (R,G,B) of “(220,220,220)”.

[0066] In the case of number "4" 814, the combination of the print layer "Film 3 (transmittance 75%)", the base layer "Paper 4 (transmittance 30%)", and the backing "White (reflectance 90%)" is linked to the target value (R,G,B) of "(235,235,235)". In the case of number "5" 815, the combination of the print layer "Film 4 (transmittance 80%)", the base layer "Paper 4 (transmittance 30%)", and the backing "Gray (reflectance 18%)" is linked to the target value (R,G,B) of "(225,225,225)".

[0067] Here, the target values ​​to be written in the file of Fig. 8 will be explained with reference to Fig. 9. Since a black backing color causes a dark image to be acquired by the reading device, in this embodiment, the target value is the pixel value of the paper white when the read image is acquired by the reading device using a white backing color. However, since it is costly to realize a device configuration that switches the backing color of the reading device, in this embodiment, the read value with a white backing is estimated from the read value of the reading device using a commonly used black backing and the measured value by a measuring device.

[0068] Fig. 9(a) is a schematic diagram of a printed layer 911 and an underlayer 912 being measured by a measuring device 921 using a white backing 913. Fig. 9(b) is a schematic diagram of a printed layer 911 and an underlayer 912 being measured by a measuring device 921 using a black backing 914. Fig. 9(c) is a schematic diagram of a printed layer 911 and an underlayer 912 being read by a reading device 922 using a black backing 914. The image acquired by the reading device 922 has sensor-linear (luminance-linear) pixel values, and taking into consideration the high correlation with the luminance value measured by the measuring device 921, a target value is estimated by the following formula (4).

[0069] R1 = R × Ya / Yb G1 = G × Ya / Yb (4) B1=B×Ya / Yb Here, R1, G1, and B1 are pixel values ​​(estimated target values) of the paper white when the paper is acquired by the reading device 922 using a white backing 913, and R, G, and B are pixel values ​​of the paper white when the paper is acquired by the reading device 922 using a black backing 914. Ya is the luminance value of the measurement value when the paper is measured using the white backing 913, and Yb is the luminance value of the measurement value when the paper is measured using the black backing 914.

[0070] In this embodiment, the read value for the white backing 913 is estimated based on the read value for the black backing 914 and the measured values ​​for the white and black backings 913, 914, but the present invention is not limited to this. For example, if the backing of the reading device is replaced with a white one and reading is possible with the white backing 913, the read value acquired by the device may be used as the target value. As an estimation method, the target value may be estimated using a physical simulation based on the surface reflectance of the pigment and the transmittance characteristics of each layer of the paper.

[0071] As described above, in this embodiment, the color of the inspection image and the color of the read image are corrected using a target value linked to the combination of the print layer and the base layer that make up the printed recording medium and the backing used when reading. This makes it possible to prevent misalignment and deterioration of inspection performance even if the base layer is made of a thin material that transmits light and the color of the backing affects the color of the read image.

[0072] <<Embodiment 3>> In this embodiment, when correcting the reference image and the read image based on the target value, it is determined whether or not the feature points used for alignment are extracted, and if not, the correction amount is sequentially updated to be stronger. Note that the process of the defect determination unit 207, which is the difference from the first and second embodiments, is described, and the other processes are the same as those of the first and second embodiments, so the description is omitted.

[0073] <Details of inspection process (S309)> FIG. 10 is a flowchart showing a detailed flow of the inspection process (S309) executed by the defect determination unit 207 according to this embodiment.

[0074] In S1001, the defect determination unit 207 acquires the corrected reference image obtained in S308. Note that, if the process of S1005 is performed, the defect determination unit 207 acquires the corrected reference image, which is an image after color correction based on the modified target value (correction amount).

[0075] In S1002, the defect determination unit 207 acquires the corrected read image obtained in S308. Note that, if the process of S1005 is performed, the defect determination unit 207 acquires the corrected read image, which is an image after color correction based on the modified target value (correction amount).

[0076] In S1003, the defect determination unit 207 extracts alignment reference points that represent image features to be used when aligning the corrected reference image and the corrected read image. As in S703, the reference points are extracted using a known image feature point extraction method such as SIFT or SURF.

[0077] In S1004, the defect determination unit 207 determines whether the number of feature points extracted in S1003 is greater than a predetermined threshold. When affine transformation is used for alignment in S1006, the predetermined threshold is, for example, 3. When the determination result indicates that the number of extracted feature points is greater than the predetermined threshold (YES in S1004), the process proceeds to S1006. When the determination result indicates that the number of extracted feature points is equal to or less than the predetermined threshold (equal to or less than a predetermined number) (NO in S1004), the process proceeds to S1005. Note that in this embodiment, the number of feature points is used as the threshold for determination, but instead of the number of feature points, a geometric transformation parameter for alignment may be calculated from the extracted feature points, and a threshold may be set to determine how much a predetermined coordinate on the inspection image varies using the geometric transformation parameter. For example, it is assumed that 5 mm is set as the allowable limit for alignment. In such a setting, if the alignment error estimated using the geometric transformation parameters is greater than 5 mm, the process may proceed to S1005, and if the estimated alignment error is 5 mm or less, the process may proceed to S1006.

[0078] In S1005, the defect determination unit 207 corrects the correction amount. Since the feature points required for alignment cannot be extracted with the target value calculated in S307, the target value is reset to 10% brighter to increase the amount of luminance correction and correct the image. If the correction is still insufficient even with 10%, the correction is continued until the brightness is such that the feature points can be extracted by setting the brightness to 10% brighter. The value of 10% is not limited to this, and for example, other numerical values ​​and correction increments are variable and may be changed. Alternatively, instead of automatically determining the correction amount, a method may be used in which the user is notified that the luminance of the image used for inspection is insufficient, the user is prompted to input the correction amount on the UI screen, and the image is corrected based on the input correction amount.

[0079] In S1006, the defect determination unit 207 aligns the corrected reference image and the corrected read image based on the extracted feature points. In this embodiment, affine transformation is used for the alignment.

[0080] In S1007, the defect determining unit 207 calculates the difference between the aligned and corrected reference image and the corrected read image.

[0081] In S1008, the defect determination unit 207 determines the presence or absence of a defect based on the calculated difference.

[0082] As described above, in this embodiment, the number of feature points used for aligning the reference image and the scanned image after color correction is checked, and if the number of checked feature points does not satisfy a predetermined condition, the amount of color correction is further strengthened to obtain feature points equal to or greater than a threshold value. This makes it possible to more appropriately align images, perform image difference processing, and detect defects, thereby improving inspection accuracy.

[0083] <<Embodiment 4>> In the first embodiment, a mode in which a target value is calculated based on a combination of a printed layer and a base layer, and in the second embodiment, a mode in which a target value is calculated based on a combination of a printed layer, a base layer, and a backing, has been described. In label paper, in addition to the combination of a printed layer and a base layer, for example, a special (spot color) toner or ink such as clear, gold, silver, or white may be provided in a printing device, and a printed matter may be formed in a multi-layer structure. For example, special toners or inks such as gold, silver, or clear can be used in a top coat layer above the printed layer to give a luxurious feel or a metallic expression to the label. In addition, white can be formed as a layer below the printed layer to form a base that is difficult to see through, and contributes to the sharpness and color development of letters and pictures, allowing for more faithful reproduction of the design.

[0084] Therefore, in this embodiment, for example, a mode in which target values ​​corresponding to combinations of a special layer (upper), a printing layer, a special layer (lower), a base layer, and a backing are stored in advance as a table, and target values ​​corresponding to these special layers are calculated. That is, a mode in which target values ​​corresponding to combinations of an upper special layer, a printing layer, a lower special layer, a base layer, and a backing are calculated is described. Note that the operation of the target value calculation unit 205, which is the difference from the second embodiment, is described, and other processes are the same as those in the second embodiment, so description thereof is omitted.

[0085] <Operation of target value calculation unit 205> 11 is a diagram showing an example of a file referenced by the target value calculation unit 205 according to the present embodiment. In the file 1100, a target value 1170 corresponding to a combination of the special layer (upper) 1120, the print layer 1130, the special layer (lower) 1140, the base layer 1150, and the backing 1160 is described as a table. That is, each data registered in the file 1100 can be said to be linked to the target value 1170 represented by (R, G, B) for the combination of the special layer (upper) 1120, the print layer 1130, the special layer (lower) 1140, the base layer 1150, and the backing 1160.

[0086] In number "1" 1111, the combinations of "None", "Film 1 (Transmittance 60%)", "None", "Backing 1 (Transmittance 1%)", and "White (Reflectance 90%)" are linked to the target value "240, 240, 240". In number "2" 1112, the combinations of "None", "Film 1 (Transmittance 60%)", "None", "Backing 1 (Transmittance 1%)", and "Gray (Reflectance 18%)" are linked to the target value "235, 235, 235".

[0087] In number "3" 1113, the combination of "none", "film 1 (transmittance 60%)", "none", "mount 1 (transmittance 1%)", and "black (reflectance 0.5%)" is linked to the target value "230, 230, 230". In number "4" 1114, the combination of "clear (transmittance 70%)", "film 3 (transmittance 75%)", "silver (transmittance 0.5%)", "mount 1 (transmittance 1%)", and "black (reflectance 0.5%)" is linked to the target value "225, 225, 225". In the case of number “5” 1115, the combination of “Clear (Transmittance 70%)”, “Film 4 (Transmittance 80%)”, “Silver (Transmittance 0.5%)”, “Backing Paper 2 (Transmittance 30%)”, and “Black (Reflectance 0.5%)” is linked to the target value “220, 220, 220”.

[0088] As described above, in this embodiment, the color of the inspection image and the color of the read image are corrected using a target value linked to the combination of the special layer (top), the printing layer, the special layer (bottom), the base layer, and the backing that make up the printed recording medium. This makes it possible to prevent misalignment and deterioration of inspection performance even if an overcoat layer above the printing layer or a layer below the printing layer is formed.

[0089] (Other embodiments) The present disclosure can also be realized by a process in which a program for implementing one or more functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that implements one or more functions.

[0090] The disclosure of this embodiment includes the following configuration examples.

[0091] (Configuration 1) An acquisition means for acquiring a read image obtained by reading a printed recording medium; a correction means for correcting a color of the read image and a color of a reference image serving as a reference in an inspection based on a target value corresponding to a combination of a print layer and a base layer constituting the printed recording medium; an inspection means for inspecting the printed recording medium based on a difference between the corrected read image and the corrected reference image; 13. An image processing device comprising:

[0092] (Configuration 2) The correction means corrects the color of the read image and the color of the reference image based on the target value corresponding to a combination of the transmittance of the print layer and the transmittance of the base layer. 2. The image processing device according to claim 1,

[0093] (Configuration 3) The correction means corrects the color of the read image and the color of the reference image based on the target value that is set so that the luminance value of the color increases as the transmittance of the print layer and the transmittance of the base layer decrease. 3. The image processing device according to configuration 2.

[0094] (Configuration 4) The correction means corrects the color of the read image and the color of the reference image based on the target value corresponding to a combination of the print layer, the base layer, and a backing used when performing the reading. 2. The image processing device according to claim 1,

[0095] (Configuration 5) The correction means corrects the color of the read image and the color of the reference image based on the target value corresponding to a combination of the transmittance of the print layer, the transmittance of the base layer, and the reflectance of the backing. 5. The image processing device according to configuration 4.

[0096] (Configuration 6) The correction means corrects the color of the read image and the color of the reference image based on the target value corresponding to a combination of an upper special layer formed on the upper side of the print layer with a special color ink, the print layer, a lower special layer formed on the lower side of the print layer with a special color ink, the base layer, and a backing used when performing the reading. 2. The image processing device according to claim 1,

[0097] (Configuration 7) The correction means corrects the color of the read image and the color of the reference image based on the target value corresponding to a combination of the transmittance of the upper special layer, the transmittance of the printing layer, the transmittance of the lower special layer, the transmittance of the base layer, and the reflectance of the backing. 7. The image processing device according to configuration 6,

[0098] (Configuration 8) The acquisition means acquires the target value associated with a combination of the printing layer and the base layer, The correction means corrects a color of the read image and a color of the reference image based on the acquired target value. 4. The image processing device according to any one of configurations 1 to 3.

[0099] (Configuration 9) the acquisition unit acquires the target value associated with a combination of the printing layer, the base layer, and a backing used when performing the reading; The correction means corrects a color of the read image and a color of the reference image based on the acquired target value. 6. The image processing device according to any one of configurations 1, 4 and 5.

[0100] (Configuration 10) the acquisition means acquires the target value associated with a combination of an upper special layer formed on the upper part of the printed layer with a special color ink, the printed layer, a lower special layer formed on the lower part of the printed layer with a special color ink, the base layer, and a backing used when performing the reading; The correction means corrects a color of the read image and a color of the reference image based on the acquired target value. 8. The image processing device according to any one of configurations 1, 6 and 7,

[0101] (Configuration 11) The target value is a pixel value of the paper white of the reference image and the read image for correcting the luminance of the paper white of the recording medium. 11. The image processing device according to any one of configurations 1 to 10.

[0102] (Configuration 12) The inspection means includes: When the number of feature points for alignment extracted from the corrected read image and the corrected reference image is equal to or less than a predetermined number, a print defect is detected on the printed recording medium based on a difference value between the read image, the color of which has been corrected based on a target value having a larger correction amount than the target value used by the correction means, and the reference image. 12. The image processing device according to any one of configurations 1 to 11.

[0103] (Configuration 13) The method further includes a control unit for controlling a user interface screen for allowing a user to specify the printing layer and the undercoat layer, The acquisition means acquires the target value associated with a combination of the printing layer and the undercoat layer selected by a user operation on the user interface screen. 9. The image processing device according to configuration 8.

[0104] (Configuration 14) The method further includes a control means for controlling a user interface screen for allowing a user to specify the printing layer, the undercoat layer, and the backing; The acquisition means acquires the target value associated with a combination of the printing layer, the undercoat layer, and the backing selected by a user operation on the user interface screen. 10. The image processing device according to configuration 9.

[0105] (Configuration 15) The acquisition means acquires the reference image. 15. The image processing device according to any one of configurations 1 to 14.

[0106] (Configuration 16) The recording medium is a label paper. 16. The image processing device according to any one of configurations 1 to 15.

[0107] (Configuration 17) The printing layer is made of a transparent film or a seal paper, and the base layer is made of a release paper or a mount paper. 17. The image processing device according to claim 16,

[0108] (Configuration 18) an acquiring step of acquiring a read image obtained by reading the printed recording medium; a correction step of correcting the color of the read image and the color of a reference image serving as a reference in inspection, based on a target value corresponding to a combination of a printing layer and a base layer constituting the printed recording medium; an inspection step of inspecting the printed recording medium based on a difference between the corrected read image and the corrected reference image; 13. An image processing method comprising:

[0109] (Configuration 19) 20. A program for causing a computer to execute each step of the image processing method according to aspect 18.

Claims

1. An acquisition means for acquiring a read image obtained by reading a printed recording medium; a correction means for correcting a color of the read image and a color of a reference image serving as a reference in an inspection based on a target value corresponding to a combination of a print layer and a base layer constituting the printed recording medium; an inspection means for inspecting the printed recording medium based on a difference between the corrected read image and the corrected reference image; 13. An image processing device comprising:

2. The correction means corrects the color of the read image and the color of the reference image based on the target value corresponding to a combination of the transmittance of the print layer and the transmittance of the base layer.

2. The image processing device according to claim 1,

3. The correction means corrects the color of the read image and the color of the reference image based on the target value that is set so that the smaller the transmittance of the print layer and the transmittance of the base layer, the higher the color luminance value.

3. The image processing device according to claim 2.

4. The correction means corrects the color of the read image and the color of the reference image based on the target value corresponding to a combination of the print layer, the base layer, and a backing used when performing the reading.

2. The image processing device according to claim 1,

5. The correction means corrects the color of the read image and the color of the reference image based on the target value corresponding to a combination of the transmittance of the print layer, the transmittance of the base layer, and the reflectance of the backing.

5. The image processing device according to claim 4.

6. The correction means corrects the color of the read image and the color of the reference image based on the target value corresponding to a combination of an upper special layer formed on the upper side of the print layer with a special color ink, the print layer, a lower special layer formed on the lower side of the print layer with a special color ink, the base layer, and a backing used when performing the reading.

2. The image processing device according to claim 1,

7. The correction means corrects the color of the read image and the color of the reference image based on the target value corresponding to a combination of the transmittance of the upper special layer, the transmittance of the printing layer, the transmittance of the lower special layer, the transmittance of the base layer, and the reflectance of the backing.

7. The image processing device according to claim 6,

8. The acquisition means acquires the target value associated with a combination of the printing layer and the base layer, The correction means corrects a color of the read image and a color of the reference image based on the acquired target value.

2. The image processing device according to claim 1,

9. the acquisition unit acquires the target value associated with a combination of the printing layer, the base layer, and a backing used when performing the reading; The correction means corrects a color of the read image and a color of the reference image based on the acquired target value.

2. The image processing device according to claim 1,

10. the acquisition means acquires the target value associated with a combination of an upper special layer formed on the upper part of the printed layer with a special color ink, the printed layer, a lower special layer formed on the lower part of the printed layer with a special color ink, the base layer, and a backing used when performing the reading; The correction means corrects a color of the read image and a color of the reference image based on the acquired target value.

2. The image processing device according to claim 1,

11. 2. The image processing apparatus according to claim 1, wherein the target value is a pixel value of paper white of the reference image and the scanned image for correcting a luminance of paper white of the recording medium.

12. The inspection means includes: When the number of feature points for alignment extracted from the corrected read image and the corrected reference image is equal to or less than a predetermined number, a print defect is detected on the printed recording medium based on a difference value between the read image, the color of which has been corrected based on a target value having a larger correction amount than the target value used by the correction means, and the reference image.

2. The image processing device according to claim 1,

13. The method further includes a control unit for controlling a user interface screen for allowing a user to specify the printing layer and the undercoat layer, The acquisition means acquires the target value associated with a combination of the printing layer and the undercoat layer selected by a user operation on the user interface screen.

9. The image processing device according to claim 8,

14. The method further includes a control means for controlling a user interface screen for allowing a user to specify the printing layer, the undercoat layer, and the backing; The acquisition means acquires the target value associated with a combination of the printing layer, the undercoat layer, and the backing selected by a user operation on the user interface screen.

10. The image processing device according to claim 9,

15. The acquisition means acquires the reference image.

2. The image processing device according to claim 1,

16. The recording medium is a label paper.

2. The image processing device according to claim 1,

17. The printing layer is made of a transparent film or a seal paper, and the base layer is made of a release paper or a mount paper.

17. The image processing device according to claim 16,

18. an acquiring step of acquiring a read image obtained by reading the printed recording medium; a correction step of correcting the color of the read image and the color of a reference image serving as a reference in inspection, based on a target value corresponding to a combination of a printing layer and a base layer constituting the printed recording medium; an inspection step of inspecting the printed recording medium based on a difference between the corrected read image and the corrected reference image; 13. An image processing method comprising:

19. A program for causing a computer to execute each step of the image processing method according to claim 18.

Images