Image inspection device, image inspection method, and image inspection program

Abstract

To provide an image inspection apparatus configured to suppress reduction in productivity while reducing the time and effort of a user, an image inspection method, and an image inspection program.SOLUTION: An image inspection apparatus 300 includes: a registration unit which registers a ground truth image; an acquisition unit which scans multiple copies of printed matters to acquire images for each copy of the printed matters, as inspection images; a detection unit which detects streaks on the inspection images by comparing the inspection images with the ground truth image; and a setting unit which sets a target region where detection is suppressed, in inspection images excluding a confirmation image, on the basis of locations of the streaks in the confirmation image which is an image of the first copy of the printed matter of the inspection images or images of the first to N-th (N is an integer equal to or larger than 2) copies of the printed matter. The detection unit suppresses detection of streaks in the target region, in the inspection images excluding the confirmation image, rather than in regions excluding the target region.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an image inspection device, an image inspection method, and an image inspection program. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2015-74108 (Patent Document 1) discloses an image forming apparatus that includes a print head in which multiple ejection ports are arranged in a direction perpendicular to the conveyance direction of a recording medium, and that performs repair operations in accordance with the results of image quality assessment. In this image forming apparatus, to prevent a decrease in productivity due to frequent repair operations, multiple regions are provided in the ejection port arrangement direction, and the image quality assessment criteria are changed for each region. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-74108 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described system, the user must instruct the image forming apparatus on the criteria for each area, which is time-consuming for the user.

[0005] The present disclosure has been made in consideration of the above-described situation, and one of its objectives is to provide an image inspection device, an image inspection method, and an image inspection program that can reduce the user's workload and prevent a decline in productivity. [Means for solving the problem]

[0006] An image inspection device according to an aspect of the present disclosure includes a registration unit that registers a correct image, an acquisition unit that scans multiple copies of printed matter and acquires an image of each copy of the printed matter as an inspection image, a detection unit that detects streaks in the inspection image by comparing the inspection image with the correct image, and a setting unit that sets a target region in the inspection image, excluding the confirmation image, where detection is suppressed, based on the location of streaks in the image of the first copy of printed matter or a confirmation image that is an image of the first to Nth copies (N is an integer of 2 or greater) of printed matter among the inspection images. The detection unit suppresses streak detection in the target region in the remaining images more than in regions excluding the target region.

[0007] Preferably, suppressing detection of streaks in the target region includes not detecting streaks in the target region.

[0008] Preferably, suppressing streak detection in the target region includes changing the streak detection level in the target region to a level at which streaks are more difficult to detect than in regions other than the target region.

[0009] Preferably, when the direction perpendicular to the paper conveyance direction is the X-axis direction, the target area is the entire area indicated by the same X coordinate as the location of the streak.

[0010] Preferably, when the direction perpendicular to the paper conveyance direction is the X-axis direction, the target area is a part of the area indicated by the same X-coordinate as the location of the streak.

[0011] Preferably, the region of interest is valid for the same print job.

[0012] Preferably, the confirmation image is an image of the first printed copy, and the location of the streak is a location where the streak is detected in the image of the first printed copy.

[0013] Preferably, the confirmation image is an image of the first to Nth copies of the printed matter, and the location of the streak is a location obtained by performing a logical OR operation on the locations where the streak is detected in the image of each copy of the printed matter in the confirmation image, a location obtained by performing a logical AND operation on the locations where the streak is detected in the image of each copy of the printed matter in the confirmation image, or a location where the streak is detected in the image of a specific copy of the printed matter in the confirmation image.

[0014] Preferably, the printing target is a document consisting of a plurality of pages, and the setting unit sets the target area for each page.

[0015] Preferably, the correct image is an image obtained by scanning a printout on which an image has been formed by test printing, or an image obtained by color-converting a raster image into RGB.

[0016] In another aspect of the present disclosure, an image inspection method executed by a computer includes registering a correct image, scanning multiple copies of printed matter with a scanner to obtain an image of each copy of the printed matter as an inspection image, detecting streaks in the inspection image by comparing the inspection image with the correct image, and setting a target area in which detection is suppressed in the remaining images of the inspection image excluding the confirmation image based on the location of streaks in an image of the first printed matter or a confirmation image which is an image of the first to Nth copies (N is an integer of 2 or greater) of the inspection image. Detecting streaks in the inspection image includes suppressing streak detection in the target area more than in areas excluding the target area for the remaining images.

[0017] An image inspection program according to another aspect of the present disclosure causes a computer to execute the image inspection method described above. [Effects of the Invention]

[0018] According to the present disclosure, it is possible to provide an image inspection device, an image inspection method, and an image inspection program that can reduce the burden on the user and prevent a decrease in productivity. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram illustrating an outline of an image forming system. [Figure 2] FIG. 2 is a block diagram showing the main hardware configuration of the image forming apparatus. [Figure 3] FIG. 2 is a block diagram showing the main hardware configuration of the image inspection device. [Figure 4] FIG. 2 is a block diagram showing an example of a functional configuration of the image inspection device. [Figure 5] 10A and 10B are diagrams for explaining an example of a method for setting a target area when an image of the first printed copy of a regular print is used as a confirmation image. [Figure 6] 10A and 10B are diagrams for explaining another example of a method for setting a target area when an image of the first printed copy of a regular print is used as a confirmation image. [Figure 7] FIG. 10 is a diagram illustrating an example of a method for setting a target area when images of the first to Nth (N is an integer of 2 or more) copies of a regular print run are used as confirmation images. [Figure 8] FIG. 10 illustrates an example of processing executed by the image forming system. [Figure 9] 10 is a flowchart illustrating an example of processing executed by the image inspection device. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated. Note that the embodiments and modifications described below may be selectively combined as appropriate.

[0021] (1. Configuration of Image Forming System) 1 is a diagram showing an outline of an image forming system. The image forming system 1 includes an image forming apparatus 100 and an image inspection apparatus 300. The image forming apparatus 100 and the image inspection apparatus 300 may be connected by a local interface such as a USB (Universal Serial Bus), or may be connected via a network.

[0022] The image forming apparatus 100 is connected to a terminal device 500 via a network. The image forming apparatus 100 receives manuscript data to be printed from the terminal device 500 and forms an image on paper based on the manuscript data (hereinafter also referred to as "printing"). The manuscript data is configured as an image in a raster format (for example, bitmap format) generated by a RIP (Raster Image Processor). Hereinafter, an image in a raster format will also be referred to as a "raster image." The terminal device 500 is configured, for example, by a PC (Personal Computer), a smartphone, a tablet, or the like. The network may be, for example, a public network such as the Internet, a public line, or a public wireless LAN (Local Area Network), or a private network such as a LAN or VPN (Virtual Private Network).

[0023] Image forming apparatus 100 includes an inkjet printer 104. Printer 104 includes a paper feed unit 11, a paper conveyor belt 12, a printing unit 13, and a paper output tray 14. Paper feed unit 11 stores a plurality of sheets of paper. The sheets are sent out one by one from paper feed unit 11 to conveyor belt 12, and then transported to printing unit 13.

[0024] Printing unit 13 includes print heads H. Print heads H include a head for cyan, a head for magenta, a head for yellow, and a head for black. Print heads H form an image on the transported paper by ejecting droplets onto the paper based on the document data received from terminal device 500. The paper on which the image has been formed (hereinafter also referred to as "printed matter") is transported to image inspection device 300, and in printing unit 13, the image is formed on paper newly transported from paper feeder 11.

[0025] The image inspection device 300 inspects the transported printed matter for streaks. In inkjet printers, streaks occur in a direction parallel to the paper transport direction when droplets clog the nozzles of the print head H. If streaks are detected, the image inspection device 300 sends error information to the image forming device 100. In response to receiving the error information, the image forming device 100 suspends the printing operation currently being performed by the printing unit 13. After inspection is complete, the printed matter is transported and discharged onto the paper output tray 14.

[0026] Generally, when multiple copies are planned to be printed, the user performs a test print using image forming apparatus 100 and visually checks the layout, color reproducibility, and image quality (for example, the presence or absence of streaks) based on the test print proof. The user repeats machine adjustments (for example, nozzle adjustment of print head H), test prints, and visual checks until the intended proof is obtained, and when the intended proof is obtained, the user performs actual printing using image forming apparatus 100.

[0027] The image quality desired by users varies depending on the product and the image (content). For example, even slight streaks are unacceptable for products such as photo books, whereas slight streaks may be acceptable for products with a lot of text. Also, even if the streaks are of the same level, if they occur on a person's face, they may be unacceptable, whereas if they occur on an image with a fine pattern or other pattern where the streaks are not noticeable, they may be acceptable. Furthermore, if the streaks occur near the center of the paper, they may be unacceptable, whereas if they occur on the edge of the paper, they may be acceptable.

[0028] In the actual printing that has started after user confirmation, it is unlikely that streaks that the user did not intend, i.e., unacceptable streaks, will occur from the very beginning. Therefore, the image inspection device 300 uses the first predetermined number of copies of the actual printing for confirmation, and does not send error information to the image forming device 100 even if streaks are detected in the confirmation print. Furthermore, the image inspection device 300 sets an area (hereinafter also referred to as the "target area") in which streak detection is suppressed based on the location of the streaks detected in the confirmation print. The image inspection device 300 suppresses streak detection in the target area in the remaining copies of the actual printing, excluding the confirmation print.

[0029] This makes it possible to prevent streaks detected in the first few copies of a print run, i.e., allowable streaks, from interrupting the printing operation. This prevents a decrease in productivity. Furthermore, the target area where streak detection is suppressed is automatically set. This reduces the user's workload.

[0030] (2. Hardware Configuration) The hardware configurations of the image forming apparatus 100 and the image inspection apparatus 300 will be described mainly with reference to FIGS.

[0031] 2 is a block diagram showing the main hardware configuration of an image forming apparatus 100. In addition to a printer 104, the image forming apparatus 100 includes a processor 101, a main memory 102, a communication interface 103, an operation panel 105, a memory card interface 106, and a storage device 120. These components are connected to each other via an internal bus 119 so that they can communicate with each other.

[0032] The processor 101 is configured, for example, by at least one integrated circuit. The integrated circuit is configured, for example, by at least one central processing unit (CPU), at least one application specific integrated circuit (ASIC), at least one field programmable gate array (FPGA), or a combination thereof.

[0033] The processor 101 realizes various processes according to this embodiment by loading the program 122 stored in the storage device 120 into the main memory 102 and executing it. The main memory 102 is configured from a volatile memory, and functions as a work memory required for the processor 101 to execute the program.

[0034] The communication interface 103 exchanges data and signals with external devices. Examples of external devices include the terminal device 500 and the image inspection device 300 shown in FIG. 1 . As an example, the image forming device 100 receives manuscript data 124 to be printed from the terminal device 500 via the communication interface 103. The image forming device 100 also receives error information from the image inspection device 300 via the communication interface 103. Furthermore, the image forming device 100 may transmit the manuscript data 124 received from the terminal device 500 to the image inspection device 300 via the communication interface 103.

[0035] Operation panel 105 is composed of a display and a touch panel. The display and touch panel are placed on top of each other, and operation panel 105 accepts operations for image forming apparatus 100 by touch operation. Furthermore, operation panel 105 may include hard buttons for accepting operations for image forming apparatus 100. Furthermore, operation panel 105 not only accepts setting operations but also provides various information to the user.

[0036] The memory card interface 106 mediates data transmission between the processor 101 and the memory card 106A. The memory card 106A may be a general-purpose semiconductor storage device such as a Secure Digital (SD), a magnetic recording medium such as a flexible disk, or an optical recording medium such as a compact disk read-only memory (CD-ROM).

[0037] Storage device 120 is, for example, a hard disk. As an example, storage device 120 stores a program 122 for implementing various processes according to the present embodiment, and manuscript data 124.

[0038] Program 122 is provided by being stored in a storage medium such as memory card 106A. Program 122 is read from memory card 106A by memory card interface 106 and installed in image forming apparatus 100. Program 122 may be provided not as a standalone program but as part of an arbitrary program. In this case, program 122 cooperates with the arbitrary program to realize the processing according to the present embodiment. Even a program that does not include some of these modules does not deviate from the spirit of image forming apparatus 100 according to the present embodiment. Some or all of the functions provided by program 122 may be realized by dedicated hardware.

[0039] Furthermore, instead of installing the program 122 stored in the memory card 106A in the image forming apparatus 100, a program downloaded from a distribution server or the like via the communication interface 103 may be installed in the image forming apparatus 100.

[0040] 3 is a block diagram showing the main hardware configuration of an image inspection device 300. The image inspection device 300 includes a processor 301, a main memory 302, a communication interface 303, a scanner 304, a memory card interface 305, and a storage device 320. These components are connected to each other via an internal bus 319 so that they can communicate with each other.

[0041] The processor 301 is configured, for example, by at least one integrated circuit, which may be configured, for example, by at least one CPU, at least one ASIC, at least one FPGA, or a combination thereof.

[0042] The processor 301 implements various processes according to this embodiment by loading the program 322 stored in the storage device 320 into the main memory 302 and executing it. The main memory 302 is configured from a volatile memory, and functions as a work memory required for the processor 301 to execute the program.

[0043] The communication interface 303 exchanges data and signals with external devices. Examples of external devices include the terminal device 500 and the image forming device 100 shown in FIG. 1. As an example, the image inspection device 300 transmits error information to the image forming device 100 via the communication interface 303. The image inspection device 300 may also receive user-specified information regarding streak detection from the terminal device 500 or the image forming device 100 via the communication interface 303. The image inspection device 300 may also receive manuscript data 124 (see FIG. 2) to be printed from the terminal device 500 or the image forming device 100 via the communication interface 303.

[0044] The scanner 304 scans a printed matter on which an image has been formed by the printing unit 13 (see FIG. 1) and acquires the image of the printed matter.

[0045] The memory card interface 305 mediates data transmission between the processor 301 and the memory card 305A. The memory card 305A may be a general-purpose semiconductor storage device such as an SD card, a magnetic recording medium such as a flexible disk, or an optical recording medium such as a CD-ROM.

[0046] The storage device 320 is, for example, a hard disk. As an example, the storage device 320 stores a program 322 for implementing various processes according to the present embodiment and a correct image 324 of the image formed by actual printing.

[0047] The program 322 is provided by being stored in a storage medium such as the memory card 305A. The program 322 is read from the memory card 305A by the memory card interface 305 and installed in the image inspection device 300. The program 322 may be provided not as a standalone program but as part of an arbitrary program. In this case, the program 322 cooperates with the arbitrary program to realize the processing according to this embodiment. Even a program that does not include some of these modules does not deviate from the spirit of the image inspection device 300 according to this embodiment. Some or all of the functions provided by the program 322 may be realized by dedicated hardware.

[0048] Furthermore, instead of installing the program 322 stored in the memory card 305A in the image inspection device 300, a program downloaded from a distribution server or the like via the communication interface 303 may be installed in the image inspection device 300.

[0049] (3. Functional configuration of image inspection device) The functional configuration of image inspection device 300 will be described mainly with reference to Fig. 4. Fig. 4 is a block diagram showing an example of the functional configuration of an image inspection device. Image inspection device 300 includes a registration unit 331, an acquisition unit 332, a detection unit 333, and a setting unit 334. The registration unit 331, the detection unit 333, and the setting unit 334 are realized by processor 301 shown in Fig. 3 executing program 322, and the acquisition unit 332 is realized by scanner 304 shown in Fig. 3.

[0050] The registration unit 331 stores (registers) the correct image of the image formed by actual printing in the storage device 320 (see FIG. 3). As an example, the correct image is an image obtained by scanning a printed matter (proof) on which an image has been formed by test printing that has been determined by the user to have no problems (the intended proof described above). The image may be acquired by the scanner 304 or by another scanner. If the image is acquired by another scanner, the registration unit 331 receives the image acquired by the other scanner via the communication interface 303.

[0051] As another example, the reference image may be an image obtained by color-converting a raster image used for actual printing to RGB. The registration unit 331 receives the raster image used for actual printing, i.e., the manuscript data 124 (see FIG. 2), from the terminal device 500 or the image forming apparatus 100 shown in FIG. 1 via the communication interface 303 (see FIG. 3). The registration unit 331 performs color conversion from CMYK to RGB on the received raster image, and registers the RGB raster image as the reference image.

[0052] The acquisition unit 332 scans a plurality of copies of printed matter on which images are formed by actual printing, and acquires an image of each copy of the printed matter as an inspection image.

[0053] The detection unit 333 detects streaks in the test image by comparing the test image with the correct image. Hereinafter, the operation of detecting streaks by the detection unit 333 will also be referred to as a "detection operation." Here, the detection operation will be described.

[0054] The detection operation includes two steps. In the first step, detection unit 333 calculates the edge strength of each pixel that makes up the test image using a known method (for example, the Sobel method, the Laplacian method, etc.), and detects as edges portions that are made up of pixels whose edge strength is equal to or greater than a threshold. In the second step, detection unit 333 compares the edge portions in the test image with the edge portions in the correct image, and detects as streaks edge portions that exist only in the test image but not in the correct image.

[0055] Setting unit 334 sets a target region in the inspection image where streak detection is suppressed. In detail, setting unit 334 first uses an image of the first printed copy or images of the first to Nth printed copies (N is an integer equal to or greater than 2) from the inspection image as a confirmation image and acquires the location of streaks in the confirmation image from detection unit 333. Next, setting unit 334 sets a target region in the inspection image where streak detection is suppressed in the remaining images excluding the confirmation image, based on the location of streaks in the confirmation image acquired from detection unit 333.

[0056] The image to be used as the confirmation image among the test images may be predetermined, or may be designated by the user via the terminal device 500 or the operation panel 105 (see FIG. 2).

[0057] The detection unit 333 suppresses streak detection in the target region of the remaining image more than in regions other than the target region. As an example, the detection unit 333 does not detect streaks in the target region of the remaining image. In particular, the detection unit 333 does not perform the detection operation itself in the target region of the remaining image. This reduces the processing load on the processor 301. Note that the detection unit 333 may perform the detection operation on the remaining image, including the target region, and process streaks detected in the target region as if they were not detected.

[0058] As another example of suppressing streak detection in the target region, the detection unit 333 may change the streak detection level in the target region for the remaining image to a level at which streaks are more difficult to detect than in the region other than the target region. As an example, the detection unit 333 changes the streak detection level in the target region for the remaining image to a level that is minus 1 compared to the streak detection level in the region other than the target region. The streak detection level can be changed by adjusting the above-mentioned edge strength threshold. The higher the edge strength threshold, the lower the streak detection level and the more difficult it is to detect streaks. The detection unit 333 sets the edge strength threshold in the target region of the remaining image (hereinafter also referred to as "threshold TH1") higher than the edge strength threshold in the region other than the target region (hereinafter also referred to as "threshold TH2").

[0059] Therefore, among the methods for suppressing streak detection in the target area, if the method for changing the streak detection level is used, streaks that exceed the threshold TH1 will be detected even if they occur in the target area. Streaks that exceed the threshold TH1 are likely to be unacceptable streaks. Therefore, among the methods for suppressing streak detection in the target area, if the method for changing the streak detection level is used, it is possible to detect only streaks that are likely to be unacceptable, without detecting acceptable streaks.

[0060] The threshold value of the edge strength in the target region of the remaining image may be determined in advance, or may be specified by the user via the terminal device 500 or the operation panel 105.

[0061] (4. Target Area) A method for setting the target area will be described mainly with reference to Figures 5 to 7. Here, the method for setting the target area will be described using an example in which a two-page document is printed in multiple copies in the final printing. Note that the print target in the final printing is not limited to a two-page document. The print target in the final printing may be a one-page document or a multiple-page document. In the following, the direction on the surface of the paper that is perpendicular to the paper transport direction is defined as the X-axis direction.

[0062] 5 is a diagram for explaining an example of a method for setting a target area when the image of the first printed copy of a regular print is used as the confirmation image. In such a case, the setting unit 334 (see FIG. 4) sets, for each page, a target area in which streak detection is suppressed in the images of the second and subsequent printed copies, based on the location where streaks were detected in the image of the first printed copy.

[0063] Referring to FIG. 5, images G1 to G6 are examples of inspection images acquired by acquisition unit 332 (see FIG. 4). Images G1 and G2 are examples of confirmation images. Image G1 is an example of an image of a printed matter corresponding to the first page of the original of the first printed matter in the official printing. Image G2 is an example of an image of a printed matter corresponding to the second page of the original of the first printed matter in the official printing.

[0064] Images G3 to G6 are examples of the remaining images. Image G3 is an example of an image of a printed matter corresponding to page 1 of the manuscript among the second printed matter in the official printing. Image G4 is an example of an image of a printed matter corresponding to page 2 of the manuscript among the second printed matter in the official printing. Image G5 is an example of an image of a printed matter corresponding to page 1 of the manuscript among the third printed matter in the official printing. Image G6 is an example of an image of a printed matter corresponding to page 2 of the manuscript among the third printed matter in the official printing. Note that the dotted lines in images G3 to G6 are added merely to indicate the target area, and the dotted lines are not included in the images themselves acquired by acquisition unit 332.

[0065] Streaks ST1 occur in the images G1, G3, and G5, and streaks ST2 occur in the images G2, G4, and G6.

[0066] When the detection unit 333 (see FIG. 4) performs a detection operation on each of the images G1 and G2, a streak ST1 is detected in the image G1, and a streak ST2 is detected in the image G2. The streak ST1 detected in the image G1 and the streak ST2 detected in the image G2 are streaks detected in the first copies of the actual printing, and can be said to be permissible streaks.

[0067] Therefore, the setting unit 334 sets the area R1, which is the entire area indicated by the same X coordinate as the location of the streak ST1, as the target area in which streak detection is suppressed in the remaining images of the printed material corresponding to the first page of the document (images G3 and G5).

[0068] In addition, the setting unit 334 sets the area R2, which is the entire area indicated by the same X coordinate as the location of the streak ST2, as the target area in which streak detection is suppressed in the remaining images of the printed material corresponding to the second page of the document (images G4 and G6).

[0069] This prevents streaks ST1 occurring in the printed matter corresponding to the first page of the original among the second and subsequent copies of printed matter from being detected by the detection operation by the detection unit 333. Also, it prevents streaks ST2 occurring in the printed matter corresponding to the second page of the original among the second and subsequent copies of printed matter from being detected by the detection operation by the detection unit 333.

[0070] In this way, a pattern in which the entire area indicated by the same X coordinate as the location of the streak detected in the confirmation image is set as the target area is referred to as pattern A below.

[0071] Fig. 6 is a diagram for explaining another example of a method for setting a target area when the image of the first printed copy of a regular print is used as a confirmation image. The example shown in Fig. 6 is the same as the example shown in Fig. 5 except that the area set as the target area is different. In the example shown in Fig. 6, setting unit 334 (see Fig. 4) sets, as the target area, part of the area indicated by the same X coordinate as the location of the streak detected in the image of the first printed copy.

[0072] Specifically, the setting unit 334 sets an area P1, which is part of the area indicated by the same X coordinate as the location of the streak ST1, as a target area in which streak detection is suppressed in the remaining images of the printed material corresponding to the first page of the document (images G3 and G5). Area P1 is an area that overlaps with the picture portion within the area indicated by the same X coordinate as the location of the streak ST1. The setting unit 334 identifies the area surrounded by the edges of the correct image as the picture portion.

[0073] Furthermore, setting unit 334 sets area P2, which is part of the area indicated by the same X coordinate as the location of streak ST2, as a target area in which streak detection is suppressed in the remaining images of the printed material corresponding to page 2 of the document (images G4 and G6). Area P2 is an area that overlaps with the picture portion of the area indicated by the same X coordinate as the location of streak ST2.

[0074] This prevents streaks ST1 occurring in the printed matter corresponding to the first page of the original among the second and subsequent copies of printed matter from being detected by the detection operation by the detection unit 333 (see FIG. 4). Also, it prevents streaks ST2 occurring in the printed matter corresponding to the second page of the original among the second and subsequent copies of printed matter from being detected by the detection operation by the detection unit 333.

[0075] In this way, a pattern in which a part of the area indicated by the same X coordinate as the location of the streak detected in the confirmation image is set as the target area is referred to as pattern B below.

[0076] When pattern A is followed, the processing load on processor 301 can be reduced. On the other hand, when pattern B is followed, it becomes possible to detect streaks that occur in the background portion. Depending on the image, streaks are less noticeable, so streaks that occur in the image portion may be acceptable, but streaks that occur in portions other than the image, i.e., the background portion, may not be acceptable. Pattern B is suitable for such cases.

[0077] When the image of the first printed copy of the actual printing is used as the confirmation image, the method of setting the target area, either pattern A or pattern B, may be determined in advance, or may be specified by the user via the terminal device 500 (see Figure 1) or the operation panel 105 (see Figure 2).

[0078] 7 is a diagram for explaining an example of a method for setting a target area when images of the first to Nth (N is an integer of 2 or more) copies of a regular print are used as confirmation images. In such a case, as an example, the setting unit 334 (see FIG. 4) sets a target area for each page where streaks are suppressed based on the locations obtained by performing a logical OR operation on the locations where streaks have been detected in the images of each copy of the confirmation image (Pattern 1).

[0079] As another example, the setting unit 334 sets a target area for each page where streak detection is suppressed based on the location obtained by performing a logical AND operation on the location where streaks are detected in the image of each copy of the confirmation image for each page (Pattern 2).

[0080] As another example, the setting unit 334 sets a target area for suppressing streak detection for each page based on a location where streaks were detected in the image of a specific copy of the confirmation image (Pattern 3). The specific copy is a copy number arbitrarily selected from the first to Nth copies (N is an integer of 2 or more) when the images of the first to Nth copies of the inspection image are used as the confirmation image.

[0081] Referring to FIG. 7, images G1 to G8 are examples of inspection images acquired by the acquisition unit 332 (see FIG. 4). Images G1 to G6 are examples of confirmation images. Image G1 is an example of an image of a printed matter corresponding to page 1 of the manuscript among the first printed matter in the official printing. Image G2 is an example of an image of a printed matter corresponding to page 2 of the manuscript among the first printed matter in the official printing. Image G3 is an example of an image of a printed matter corresponding to page 1 of the manuscript among the second printed matter in the official printing. Image G4 is an example of an image of a printed matter corresponding to page 2 of the manuscript among the second printed matter in the official printing. Image G5 is an example of an image of a printed matter corresponding to page 1 of the manuscript among the third printed matter in the official printing. Image G6 is an example of an image of a printed matter corresponding to page 2 of the manuscript among the third printed matter in the official printing.

[0082] Images G7 and G8 are examples of the remaining images. Image G7 is an example of an image of a printed matter corresponding to the first page of the manuscript among the fourth printed matter in the actual printing. Image G8 is an example of an image of a printed matter corresponding to the second page of the manuscript among the fourth printed matter in the actual printing. Note that the dotted lines in images G7 and G8 are added merely to indicate the target area, and the dotted lines are not included in the images themselves acquired by acquisition unit 332.

[0083] Streaks ST1 occur in images G1, G3, G5, and G7, streaks ST2 occur in images G2, G4, G6, and G8, and streaks ST3 occur in image G3.

[0084] When the detection unit 333 (see FIG. 4) performs a detection operation on each of the images G1 to G6, a streak ST1 is detected in the images G1 and G5, a streak ST1 and a streak ST3 are detected in the image G3, and a streak ST2 is detected in the images G2, G4, and G6. The streak ST1, streak ST2, and streak ST3 are streaks detected in the first copies of the actual printing, and can be said to be permissible streaks.

[0085] [If following Pattern 1] 7, the locations obtained by performing a logical OR operation on the locations where streaks were detected in the images of the printed matter corresponding to the first page of the document (image G1, image G3, and image G5) among the confirmation images are the locations of streaks ST1 and ST3. The setting unit 334 sets area R1, which is the entire area indicated by the same X coordinate as the location of streak ST1, and area R3, which is the entire area indicated by the same X coordinate as the location of streak ST3, as target areas where streak detection is suppressed in the image of the printed matter corresponding to the first page of the document (image G7) among the remaining images.

[0086] 7, the location of streak ST2 is obtained by performing a logical OR operation on the locations where streaks are detected in the images of the printed matter corresponding to the second page of the document (image G2, image G4, and image G6) among the confirmation images. The setting unit 334 sets area R2, which is the entire area indicated by the same X coordinate as the location of streak ST2, as the target area where streak detection is suppressed in the image of the printed matter corresponding to the second page of the document (image G8) among the remaining images.

[0087] This prevents streaks ST1 and ST3 occurring in the printed matter corresponding to the first page of the original among the fourth and subsequent printed matters from being detected by the detection operation by the detection unit 333. Also, it prevents streaks ST2 occurring in the printed matter corresponding to the second page of the original among the fourth and subsequent printed matters from being detected by the detection operation by the detection unit 333.

[0088] [If following Pattern 2] 7, the location of streak ST1 is obtained by performing a logical AND operation on the locations where streaks have been detected in the images of the printed matter corresponding to the first page of the document (image G1, image G3, and image G5) among the confirmation images. The setting unit 334 sets region R1, which is the entire area indicated by the same X coordinate as the location of streak ST1, as the target region where streak detection is suppressed in the image of the printed matter corresponding to the first page of the document (image G7) among the remaining images.

[0089] 7, the location of streak ST2 is obtained by performing a logical AND operation on the locations where streaks are detected in the images of the printed matter corresponding to the second page of the document (image G2, image G4, and image G6) among the confirmation images. The setting unit 334 sets area R2, which is the entire area indicated by the same X coordinate as the location of streak ST2, as the target area where streak detection is suppressed in the image of the printed matter corresponding to the second page of the document (image G8) among the remaining images.

[0090] This prevents streaks ST1 occurring in the printed matter corresponding to the first page of the original among the fourth and subsequent printed matters from being detected by the detection operation by the detection unit 333. Also, it prevents streaks ST2 occurring in the printed matter corresponding to the second page of the original among the fourth and subsequent printed matters from being detected by the detection operation by the detection unit 333.

[0091] [If following Pattern 3] 7, if the specific copy number is the last copy number of the copies set for confirmation, i.e., the third copy, the location where a streak was detected in the image of the specific copy number of printed matter corresponding to the first page of the original (image G5) is the location of streak ST1. The setting unit 334 sets area R1, which is the entire area indicated by the same X coordinate as the location of streak ST1, as the target area where streak detection is suppressed in the image of the printed matter corresponding to the first page of the original (image G7) among the remaining images.

[0092] 7, if the specific copy number is the last copy number of the copies set for confirmation, i.e., the third copy, the location where a streak was detected in the image of the specific copy number of the printed matter corresponding to the second page of the original (image G6) is the location of streak ST2. The setting unit 334 sets area R2, which is the entire area indicated by the same X coordinate as the location of streak ST2, as the target area where streak detection is suppressed in the image of the printed matter corresponding to the second page of the original (image G8) among the remaining images.

[0093] This prevents streaks ST1 occurring in the printed matter corresponding to the first page of the original among the fourth and subsequent printed matters from being detected by the detection operation by the detection unit 333. Also, it prevents streaks ST2 occurring in the printed matter corresponding to the second page of the original among the fourth and subsequent printed matters from being detected by the detection operation by the detection unit 333.

[0094] When images of the first to Nth (N is an integer greater than or equal to 2) copies of a printed copy are used as confirmation images, the method of setting the target area using patterns 1 to 3 may be predetermined, or may be specified by the user via terminal device 500 (see Figure 1) or operation panel 105 (see Figure 2).

[0095] In addition, in patterns 1 to 3, the setting unit 334 sets the entire area indicated by the same X coordinate as the location of the streak as the target area in which streak detection is suppressed, but as in the example (pattern B) shown in FIG. 6, it is also possible to set the area that overlaps with the picture part within the area indicated by the same X coordinate as the location of the streak as the target area.

[0096] The specific number of copies in pattern 3 may be determined in advance or may be specified by the user via the terminal device 500 or the operation panel 105.

[0097] (5. Processing Executed by the Image Forming System) The process executed by the image forming system 1 will be described mainly with reference to Fig. 8. Fig. 8 is a diagram showing an example of the process executed by the image forming system.

[0098] In step S1, image forming apparatus 100 performs a test print based on the document data (raster image) received from terminal device 500. Step S1 is executed by printer 104 (see FIG. 2). If the user determines that there are no problems, image forming apparatus 100 proceeds to step S3.

[0099] In step S2, the image inspection device 300 registers the correct image. Step S2 is executed by the registration unit 331 (see FIG. 4). As one example, the image inspection device 300 registers as the correct image an image obtained by scanning a printed matter (proofs) on which an image has been formed by trial printing that has been determined to be problem-free by the user (the intended proof described above) (case 1). As another example, the image inspection device 300 may register as the correct image an image obtained by color-converting a raster image used for actual printing to RGB (case 2).

[0100] In step S3, the image forming apparatus 100 starts actual printing. Step S3 is executed by the printer 104.

[0101] In step S4, the image inspection device 300 acquires a confirmation image. The confirmation image is an image of the confirmation printed matter described above, i.e., the first printed matter in the actual printing, or the first to Nth (N is an integer of 2 or more) printed matters in the actual printing, acquired by scanning the prints. Step S4 is executed by the acquisition unit 332 (see FIG. 4).

[0102] In step S5, image inspection device 300 performs a detection operation on the verification image. Step S5 is performed by detection unit 333 (see FIG. 4).

[0103] In step S6, the image inspection device 300 sets a target region where detection is suppressed. Step S6 is executed by the setting unit 334 (see FIG. 4).

[0104] In step S7, the image inspection device 300 acquires the remaining images. The remaining images are images of the remaining printed matter obtained by scanning the remaining printed matter in the actual printing, excluding the confirmation printed matter. Step S7 is executed by the acquisition unit 332.

[0105] In step S8, the image inspection device 300 performs a detection operation on the remaining image. Step S8 is performed by the detection unit 333. In step S8, the image inspection device 300 performs a detection operation on the remaining image while suppressing streak detection in the target region more than in regions other than the target region.

[0106] (6. Processing performed by the image inspection device) The processing executed by the image inspection device 300 will be described mainly with reference to Fig. 9. Fig. 9 is a flowchart showing an example of processing executed by the image inspection device. The processing shown in Fig. 9 is processing executed in response to one actual print, i.e., one print job.

[0107] In step S31, processor 301 (see FIG. 3) operates as registration unit 331 (see FIG. 4) and registers a correct image. If the printing target in the actual printing is a document consisting of multiple pages, processor 301 registers a correct image for each page.

[0108] In step S32, scanner 304 (see FIG. 3) acquires an image of the nth (n≧1) copy of the printed matter in the official printing. If the printing target in the official printing is a document consisting of multiple pages, scanner 304 acquires an image of the nth copy of the printed matter in the official printing for each page.

[0109] In step S33, the processor 301 operates as the detection unit 333 (see FIG. 4) and performs a detection operation on the image acquired in step S32.

[0110] In step S34, processor 301 determines whether or not streaks are detected. If streaks are detected (YES in step S34), processor 301 proceeds to step S35. On the other hand, if streaks are not detected (NO in step S34), processor 301 proceeds to step S36.

[0111] In step S35, the processor 301 stores the detected streak locations for each image acquired in step S32 in the storage device 320 (see FIG. 3).

[0112] In step S36, processor 301 determines whether the detection operation has been completed for all the numbers of copies set for confirmation. If the detection operation has been completed for all the numbers of copies set for confirmation (YES in step S36), processor 301 proceeds to step S38. On the other hand, if the detection operation has not been completed for all the numbers of copies set for confirmation (NO in step S36), processor 301 proceeds to step S37.

[0113] In step S37, the processor 301 increments n by 1, and returns the process to step S32.

[0114] In step S38, processor 301 operates as setting unit 334 (see FIG. 4) and sets a target area in which streak detection is suppressed based on the location of the streak in the confirmation image. If the printing target for actual printing is a document consisting of multiple pages, processor 301 sets a target area for each page. The method for setting the target area is as described above.

[0115] In step S39, the processor 301 increments n by 1, and proceeds to step S40.

[0116] In step S40, scanner 304 acquires an image of the nth copy of the printed matter in the official printing. If the printing target in the official printing is a document consisting of multiple pages, scanner 304 acquires an image of the nth copy of the printed matter in the official printing for each page.

[0117] In step S41, processor 301 operates as detection unit 333 and performs a detection operation on the image acquired in step S40. In step S41, processor 301 performs the detection operation in a state in which detection of streaks in the target area set in step S38 is suppressed more than in areas other than the target area.

[0118] In step S42, processor 301 determines whether or not streaks are detected. If streaks are detected (YES in step S42), processor 301 proceeds to step S43. On the other hand, if streaks are not detected (NO in step S42), processor 301 proceeds to step S44.

[0119] In step S43, processor 301 executes error processing. As an example, processor 301 transmits error information to image forming apparatus 100 (see FIG. 1). The error information includes information indicating the occurrence of streaks and may further include information indicating the location of the streaks. In response to receiving the error information from image inspection device 300, image forming apparatus 100 stops the printing operation being performed and displays an error message on operation panel 105 (see FIG. 2). The error message may be a message indicating that streaks have been detected, a message urging machine adjustment, or both.

[0120] In step S44, processor 301 determines whether the detection operation has been completed for all printed materials printed by regular printing. If the detection operation has been completed for all printed materials printed by regular printing (YES in step S44), processor 301 proceeds to step S45. On the other hand, if the detection operation has not been completed for all printed materials printed by regular printing (NO in step S44), processor 301 returns the process to step S39.

[0121] In step S45, the processor 301 cancels the setting made in step S38.

[0122] After step S45, the processor 301 ends the series of processes shown in FIG.

[0123] In this way, image inspection device 300 uses the first few copies of the actual print run as a confirmation run to check for allowable streaks, and does not send error information to image forming device 100 even if streaks are detected in the confirmation print run. Furthermore, image inspection device 300 sets a target area in which streak detection is suppressed based on the location of the streaks detected in the confirmation print run. Image inspection device 300 suppresses streak detection in the target area in the remaining print runs of the actual print run, excluding the confirmation print run.

[0124] This makes it possible to prevent the printing operation from being interrupted due to streaks detected in the first set of printed copies of the regular printing, i.e., allowable streaks, and therefore to prevent a decrease in productivity.

[0125] Furthermore, since the target area in which streak detection is suppressed is automatically set, the burden on the user can be reduced.

[0126] Furthermore, when the printing target for actual printing is a document consisting of multiple pages, the image inspection device 300 sets a target area for each page where streak detection is suppressed. If a uniform area is set across all pages as the target area for streak detection suppression, there is a risk that streaks that should be detected will not be detected. However, the image inspection device 300 sets a target area for each page. Therefore, it is possible to prevent streaks that should be detected from not being detected.

[0127] Furthermore, when the image inspection device 300 has completed the detection operation for all printed materials printed in the regular printing, it cancels the set target area. In other words, in the image inspection device 300, the target area is valid only for the same print job. As a result, for the printed materials printed in the next regular printing, a separate target area appropriate for that printed material is set. This makes it possible to prevent streaks that should be detected from going undetected.

[0128] In the above embodiment, the location of the streak detected in the confirmation image is automatically set as a target area where detection is suppressed. However, if a raster image is used for the target image, the user may visually check the location of the streak detected in the confirmation image and determine whether to set the location as a target area where detection is suppressed. If a raster image is used for the target image, there is a possibility that a test print has not been performed. The setting unit 334 cannot determine whether the streak detected in the confirmation image is an acceptable streak. However, even in such a case, the user can visually check the location of the streak detected in the confirmation image and determine whether to set the location as a target area where detection is suppressed, making it possible to detect only streaks that are likely to be unacceptable.

[0129] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0130] 1 Image forming system, 11 Paper feed unit, 12 Conveyor belt, 13 Printing unit, 14 Paper output tray, 100 Image forming device, 101, 301 Processor, 102, 302 Main memory, 103, 303 Communication interface, 104 Printer, 105 Operation panel, 106, 305 Memory card interface, 106A, 305A Memory card, 119, 319 Internal bus, 120, 320 Storage device, 122, 322 Program, 124 Original data, 300 Image inspection device, 304 Scanner, 324 Correct image, 331 Registration unit, 332 Acquisition unit, 333 Detection unit, 334 Setting unit, 500 Terminal device, G1, G2, G3, G4, G5, G6, G7, G8 Image, H Print head, P1, P2, R1, R2, R3 areas, ST1, ST2, ST3 stripes.

Claims

1. a registration unit for registering a correct image; an acquisition unit that scans a plurality of copies of a printed material and acquires an image of each copy of the printed material as an inspection image; a detection unit that detects streaks in the inspection image by comparing the inspection image with the target image; a setting unit that sets a target region in which detection is suppressed in the remaining images of the inspection image excluding the confirmation image, based on the location of the streak in the image of the first printed item or the confirmation image that is the image of the first to Nth printed items (N is an integer of 2 or more) of the inspection image; The detection unit suppresses detection of streaks in the target region of the remaining image more than in a region other than the target region.

2. The image inspection device according to claim 1 , wherein suppressing detection of streaks in the target region includes not detecting streaks in the target region.

3. The detection unit Calculating the edge intensity of each pixel constituting the inspection image; A portion composed of pixels whose edge strength is equal to or greater than a threshold is detected as an edge; 3. The image inspection device according to claim 1, wherein edge portions in the inspection image are compared with edge portions in the target image, and edge portions that exist only in the inspection image but not in the target image are detected as streaks.

4. 4. The image inspection device according to claim 1, wherein, when a direction perpendicular to a paper conveyance direction is defined as an X-axis direction, the target area is the entire area indicated by the same X-coordinate as the location of the streak.

5. 4. The image inspection device according to claim 1, wherein, when a direction perpendicular to a paper transport direction is defined as an X-axis direction, the target area is a part of an area indicated by the same X-coordinate as the location of the streak.

6. 6. The image inspection device according to claim 1, wherein the target area is valid for the same print job.

7. the confirmation image is an image of the first printout, 7. The image inspection device according to claim 1, wherein the streak location is a location where a streak is detected in the image of the first copy of the printed matter.

8. the confirmation images are images of the first to Nth copies of the printed matter, The location of the streak is a location obtained by performing a logical OR operation on the locations where streaks are detected in the image of each copy of the printout among the confirmation images; a location obtained by performing a logical product operation on the location where the streak is detected in the image of each copy of the printout among the confirmation images; Alternatively, the image inspection device according to any one of claims 1 to 6 is a location where a streak is detected in an image of a specific number of copies of the confirmation image.

9. The printing target is a manuscript consisting of multiple pages, 9. The image inspection device according to claim 1, wherein the setting unit sets the target area for each page.

10. The image inspection device according to any one of claims 1 to 9, wherein the correct image is an image obtained by scanning a printed matter on which an image has been formed by test printing, or an image obtained by color-converting a raster image to RGB.

11. 1. A computer-implemented image inspection method comprising: Registering the correct image, Scanning a plurality of copies of the printed matter with a scanner to obtain an image of each copy of the printed matter as an inspection image; detecting streaks in the inspection image by comparing the inspection image with the target image; and based on the location of the streak in a confirmation image, which is an image of the first printed copy of the inspection image or an image of the first to Nth (N is an integer of 2 or more) printed copies, setting a target area in which detection is suppressed in the remaining images of the inspection image excluding the confirmation image, An image inspection method, wherein detecting streaks in the inspection image includes suppressing detection of streaks in the target region of the remaining image more than in regions other than the target region.

12. An image inspection program for causing a computer to execute the image inspection method according to claim 11.

Images