Image processing device, control method and program thereof

Abstract

To determine the presence or absence of reproducibility of defects related to printing in a printer even if defect positions on images on a plurality of recording media printed by the printer change.SOLUTION: An image processing apparatus is connected with a printer, sequentially receives input of a plurality of recording media on which images are printed by the printer, and checks the quality of the images formed on the recording media, and the image processing apparatus has: a reference image input unit that receives input of a reference image; a scan image input unit that sequentially scans the plurality of recording media that are output from the printer, the recording media in which images to be checked are recorded, to acquire a plurality of scan images; a phase information input unit that receives input of phase information on an image forming body included in the printer; a defect detection unit that compares a pixel value of the reference image and a pixel value of each of the plurality of scan images to detect defects on the plurality of scan images; and a determination unit that determines reproducibility of the defects based on the positions of the defects on the recording media calculated from the phase information.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an image processing apparatus, a control method thereof, and a program. [Background technology]

[0002] When hardware such as a photosensitive drum constituting a printing device is damaged by wear caused by mass printing or long-term operation, the quality of the printed matter output may be reduced. Specifically, stains occur repeatedly in which coloring materials such as ink and toner adhere to unintended locations. Alternatively, coloring materials adhere to locations where images should be formed, and color loss occurs repeatedly, resulting in a lighter color than the original color. When printing defects such as stains and color loss occur repeatedly, the quality and yield of printed matter are reduced. For this reason, it is necessary to inspect the presence or absence of printing defects, and if defects occur repeatedly, to notify the user and guarantee the quality and yield of printed matter. Visual inspection for inspecting the presence or absence of printing defects requires a lot of time and cost, so an inspection system that performs the inspection automatically has been proposed. In such an inspection system, the inspection is performed by calculating the presence or absence of defects based on the difference between a reference image that serves as an inspection standard for printed matter registered in advance and an inspection target image obtained by scanning the printed matter to be inspected.

[0003] In Patent Document 1, when a defect occurs on an output image, the user repeatedly outputs a test image for reproducing the defect, and visually judges whether the same defect is repeated. If the defect is repeated, the output test image is scanned, and the scanned image and copier identification data are transferred to a remote diagnostic computer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3576209 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the method described in Patent Document 1, even if printing defects are automatically inspected by an inspection system, the reproducibility of the printing defects is judged visually, which requires a lot of time and cost. Therefore, an inspection system that automatically judges the reproducibility of defects from scanned images is required, but since the reproduced position of the defects varies depending on the photosensitive drum / intermediate transfer belt cycle length, paper length, image formation timeline, etc., it has been difficult to judge the presence or absence of the reproducibility of the defects from the scanned images.

[0006] The present invention has been developed in consideration of such problems, and makes it possible to determine whether defects related to printing in a printing device are reproducible even if the position of defects in images of multiple recording media printed by the printing device varies. [Means for solving the problem]

[0007] In order to solve this problem, for example, an image processing device according to the present invention has the following arrangement. a reference image input means for inputting a reference image; A plurality of recording media on which images to be inspected are recorded, output from a printing device, are sequentially The sensor a scan image input means for acquiring a plurality of scan images obtained by scanning; a phase information input unit for inputting phase information of an image forming body of the printing device; the reference image and the plurality of scanned images; The images are aligned by transformation using a matrix. The above After alignment a defect detection means for detecting defects on the plurality of scanned images; Based on the phase information, Between the plurality of scanned images after the alignment, The defect When the amount of positional deviation is less than a threshold value, the defect is determined to be a defect reproduced due to the image forming body. A determination means for determining , The determination means transforms the plurality of scanned images after the alignment using an inverse matrix of the matrix when the amount of deviation is equal to or greater than the threshold, and determines that the defect is a defect reproduced due to the sensor when the amount of deviation of the position of the defect between the transformed plurality of scanned images is less than a threshold. . Effect of the Invention

[0008] According to the present invention, even if the positions of defects in images printed on a plurality of recording media by a printing device vary, it is possible to determine whether or not defects relating to printing by the printing device are reproducible. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the overall configuration of a printing system including an image processing apparatus. [Diagram 2] FIG. 13 is a diagram showing an example of a defect that repeatedly reoccurs. [Diagram 3] FIG. 2 is a block diagram showing the functional configuration of the image processing apparatus. [Figure 4] 4 is a flowchart showing a flow of processing performed in image processing. [Diagram 5] FIG. 4 is a diagram showing an example of a reference image. [Figure 6] FIG. 4 is a diagram showing an example of phase information. [Figure 7] FIG. 13 is a diagram showing an example of a scanned image. [Figure 8] 4 is a flowchart of an image correction process. [Figure 9] FIG. 11 is a diagram showing an example of a corrected image. [Figure 10] 4 is a flowchart of a defect detection process. [Figure 11] FIG. 13 is a diagram showing an example of a defect image. [Figure 12] 13 is a flowchart of a reproducibility determination process. [Figure 13] FIG. 11 is a diagram showing an example of a determination result. [Figure 14] FIG. 11 is a diagram showing an example of an aligned image. [Figure 15] FIG. 13 is a diagram showing an example of a cropped aligned image. [Figure 16] 5A to 5C are diagrams for explaining a defect detection process. [Figure 17] FIG. 4 is a diagram showing an example of an image forming body region image Icur. [Figure 18] FIG. 4 is a diagram showing an example of an image forming body region image Ipre. [Figure 19] 6A to 6C are diagrams for explaining a reproducibility determination process. [Figure 20] 13A to 13C are diagrams showing examples of a scanned image and an image forming body region image Icur according to a second embodiment. [Figure 21] 13 is a flowchart of a repeatability determination process according to the second embodiment. [Figure 22] 13 is a flowchart of a determination region image IMGmask generation process according to the second embodiment. [Diagram 23] FIG. 13 is a diagram showing an example of a determination region image IMGcur_mask according to the second embodiment. [Figure 24] 13A to 13C are views showing examples of determination region images IMGpre_mask and IMGmask according to the second embodiment. [Diagram 25] 13A and 13B are views showing examples of an image forming body region image IMGpre and a determination result according to the second embodiment. [Figure 26] 13A to 13C are views for explaining an overwrite update process of an image forming body region image IMGpre according to the second embodiment. [Figure 27] FIG. 13 is a diagram showing an example of a determination region image IMGpre_mask that has been overwritten and updated in the second embodiment. [Figure 28] 13A to 13C are views for explaining the repeatability determination process for the (i-1)th to (i+1)th scanned images according to the second embodiment. [Figure 29] 13 is a flowchart of a modified example of a determination region image IMGcur_mask generation process. [Diagram 30] 10A to 10C are diagrams showing examples of a scan image, a defect image, and an image forming body region image according to a modified example. [Diagram 31] 10A to 10C are views for explaining a modified example of a paper white area image generation process. [Diagram 32] 13A and 13B are diagrams showing examples of an image forming body region image IMGpre and a determination result in a modified example. [Diagram 33] 13A to 13C are views showing examples of a scan image and a defect image according to a third embodiment. [Diagram 34] 13 is a flowchart of a repeatability determination process according to the third embodiment. [Diagram 35] 13 is a flowchart of a sensor defect determination process according to a third embodiment. [Diagram 36] FIG. 13 is a diagram showing an example of a determination result according to the third embodiment. [Figure 37] 13A to 13C are views for explaining a sensor defect determination process according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0011] [First embodiment] In this first embodiment, a method is described for determining whether or not a defect is reproducible from a scanned image, even when the defect reproduction position varies depending on the periodic length of the photosensitive drum and intermediate transfer belt in a printing device, the paper length, the image formation timeline, etc.

[0012] FIG. 1 shows an example of the overall configuration of a printing system that performs image quality inspection of a printed output, including an image processing device 100 to which the embodiment is applied. The printing system in this embodiment includes the image processing device 100, a printing server 180, and a printing device 190. The printing server 180 has a function of generating a print job of a document to be printed and inputting the print job to the printing device 190. The printing device 190 has a function of forming an image on a recording medium (on a printing paper) based on the print job input from the printing server 180. The printing device 190 can be an offset printing device, an electrophotographic device, or the like. The printing device 190 in this embodiment is assumed to be an electrophotographic printing device. The printing device 190 has a paper feed unit 191, and a user sets printing paper in the paper feed unit 191 in advance. When a print job is input, the printing device 190 conveys the printing paper set in the paper feed unit 191 along a conveying path 192. In synchronization with the transport of the printing paper, a toner image is formed on an image forming body consisting of a photosensitive drum 193, an intermediate belt 194, etc., and the toner image is transferred onto the surface of the printing paper by a voltage-applied transfer roller 195. The transferred toner image is fixed onto the printing paper by a fixing roller 196, and the printed matter on which the image is formed is sent to the image processing device 100.

[0013] The image processing device 100 of this embodiment is connected to a printing device 190, and performs an inspection process to check for defects on paper, i.e., printed matter, that the printing device 190 forms an image on and sends via a conveying path 192. That is, the image processing device 100 functions as an inspection processing device. The image processing device 100 has a CPU 101, a RAM 102, a ROM 103, a main memory device 104, an image reading device 105, an interface (I / F) 106 with the printing device, a general-purpose interface (I / F) 107, a user interface (UI) panel 108, and a main bus 109 inside. The image processing device 100 further has a conveying path 110 for printed matter connected to the conveying path 192 of the printing device 190, an output tray 111 for printed matter that has passed the inspection, and an output tray 112 for printed matter that has failed the inspection due to the discovery of a defect. A switching unit (not shown) is provided on the conveying path 110 to switch to either the output tray 111 or 112 to which the printed matter is to be discharged, and this switching unit operates under the control of the CPU 101. Note that the classification of the printed matter is not limited to these two types, pass and fail, and may be further classified.

[0014] The CPU 101 is a processor that controls each unit in the image processing device 100. The RAM 102 functions as the main memory, work area, etc. of the CPU 101. The ROM 103 stores a group of programs executed by the CPU 101. The main storage device 104 stores applications executed by the CPU 101, data used in image processing, etc. The image reading device (hereinafter, simply referred to as a scanner) 105 can read one side or both sides of a printed matter sent from the printing device 190 on a conveying path 110 and obtain the image data. The printing device I / F 106 is connected to the printing device 190, and can synchronize the processing timing of the printing device 190 and the printing device 190, and can communicate each other's operating status. 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. The UI panel 108 is, for example, a liquid crystal display, and functions as a user interface for the image processing device 100, displaying and informing the user of the current status and settings. The UI panel 108 also receives instructions from the user by being provided with a touch panel or buttons. A main bus 109 connects the various parts of the image processing device 100. In addition, although not shown in FIG. 1, various parts inside the image processing device 100 and the printing system can be operated by instructions from the CPU 101, and for example, a switching unit is provided that moves the conveying paths in synchronization and switches whether the printed matter is sent to the pass output tray 111 or the fail output tray 112 depending on the inspection result. In addition to the CPU, a GPU may also be provided.

[0015] Overall, the image processing device 100 performs an inspection process, described below, based on image data of the printed matter read by the scanner 105 while transporting the printed matter sent from the printing device 190 on a transport path 110. As a result of the inspection process, printed matters that pass the inspection are transported to an output tray 111 for pass prints, and printed matters that fail the inspection are transported to an output tray 112 for fail prints. In this way, only those whose quality has been confirmed can be collected in the output tray 111 as deliverables for delivery.

[0016] A repeatedly reproducing defect to be detected in this embodiment will be described with reference to Fig. 2. The printing device 190 has an image forming body composed of a photosensitive drum 193 that forms an image by electrophotography, and an intermediate belt 194. Although not shown, a charger that charges the surface of the photosensitive drum 193 in the image forming body, a laser element that generates laser light according to image data, a polygon mirror that rotates by driving a motor and reflects the laser light toward the photosensitive drum 193, and a developer that attaches toner to the electrostatic latent image formed on the photosensitive drum 193 to form a toner image are provided around the photosensitive drum 193.

[0017] After a print job is input, the printing device 190 forms a toner image on a photosensitive drum 193, which rotates in synchronization with the transport of the print paper, in accordance with a well-known electrophotographic method, and transfers the formed toner image to an intermediate belt 194. Then, the toner image on the intermediate belt 194 is transferred to the surface of the transported print paper by a transfer roller 195 to which a voltage is applied.

[0018] 2 occurs on the photosensitive drum 193 and the intermediate belt 194, unintended toner adheres to the photosensitive drum 193 or the intermediate belt 194 due to the application of voltage, or sufficient toner does not adhere to the photosensitive drum 193 or the intermediate belt 194, resulting in failure to form a good image in the area of ​​the scratches 201 or 202. As a result of the photosensitive drum 193 and the intermediate belt 194 rotating and repeating output image formation and transfer, unintended toner adheres to the image area corresponding to the scratches 201 or 202, or printed matter with insufficient toner adhered thereto is repeatedly output.

[0019] 3 shows a functional configuration diagram of the image processing device 100 in this embodiment. This functional configuration is realized by the CPU 101 of the image processing device 100 executing a program for realizing the function. This program is stored in the ROM 103 or the main storage device 104.

[0020] The reference image input unit 301 inputs a reference image that serves as an inspection standard for printed matter and that is stored in advance in the RAM 102 or the main storage device 104. The reference image input unit 301 outputs the input reference image to the defect detection unit 305. Note that this reference image is an ideal image that is assumed to be obtained by scanning an image recorded on a recording medium without any defects. This reference image is sent from the printing device 190 or the printing server 180 at the start of processing in the inspection mode, and is stored in the RAM 102 or the main storage device 104.

[0021] A phase information input unit 302 inputs phase information stored in the RAM 102 or the main storage device 104, and outputs it to a repeatability determination unit 306. Here, the phase information is information that associates the rotational phase of the image forming body with the reading pixel position of the scanner 105, and is obtained by synchronizing the printing device 190 and the image processing device 100 through communication with the printing device 190 via the printing device I / F 106.

[0022] In synchronization with a signal input via the printer 106, the scanned image input unit 303 causes the scanner 105 to scan the printed matter discharged from the printer 190 and conveyed onto the conveying path 110. The scanned image input unit 303 then inputs the image data obtained by scanning with the scanner 105, and outputs the input image data to the image correction unit 304 as a scanned image.

[0023] The image correction unit 304 performs correction on the scanned image to correct misalignment caused by misalignment due to misalignment of the printed matter transported on the transport path 110 or flexure of the paper. The image correction unit 304 outputs the corrected image to the defect detection unit 305.

[0024] The defect detection unit 305 generates defect information representing defects on the corrected image from the defect image generated based on the difference between the corrected image and the reference image. Then, the defect detection unit 305 outputs the generated defect information to the repeatability determination unit 306.

[0025] Based on the phase information, the repeatability determination unit 306 calculates the occurrence positions of defects on the image forming bodies such as the photosensitive drum 193 and the intermediate belt 194 for defects occurring on the multiple scanned images, and determines the repeatability of the defects detected between the scanned images. Then, the repeatability determination unit 306 outputs the determination result to the UI panel 108 or the printing device 190.

[0026] [Operation of image processing device 100] The operation of image processing executed by the image processing device 100 will be described. Fig. 4 is a flowchart of the image processing executed by the image processing device 100. The processing according to the flowchart in the figure is realized by the CPU 101 reading and executing a program stored in the ROM 103 or the main memory device 104. In the following description, each step (process) will be denoted with the letter "S".

[0027] In S401, the reference image input unit 301 inputs a reference image that serves as an inspection standard for printed matter stored in the RAM 102 or the main memory device 104. The reference image may be set, for example, as a scanned image of a printed matter that has been visually determined in advance to be free of defects. In this embodiment, the reference image shown in Fig. 5 is input. In this embodiment, image data in which one pixel in grayscale is 8 bits (256 gradations) is input as the reference image.

[0028] In S402, the phase information input unit 302 inputs the phase information stored in the RAM 102 or the main storage device 104. In this embodiment, the correspondence between the timing of conveying the printed matter, the rotation phase of the image forming body composed of the photosensitive drum 193 and the intermediate belt 194, and the reading pixel position of the scanner 105 is input as phase information. FIG. 6(a) shows a graph showing the positional relationship of the printed matter and the rotation phase of the photosensitive drum 193, etc., obtained from the operation timing after the above print job is input. The horizontal axis is the position coordinate with the origin Y=0 at the time of job input, and is a value converted into pixels at the scan image resolution. Ys(i) is the scan start position of the i-th print image. Yp(i) is the start position at which the printed matter to output the i-th print image is conveyed on the scanner 105. Yd(i) and Yb(i) are the start positions of the photosensitive drum 193 and the intermediate belt 194 that appear first on the i-th scan image. These start positions are calculated according to the following formula (1).

[0029]

number

[0030] FIG. 6B shows the positional relationship in FIG. 6A and phase information obtained from the above-mentioned formula (1), forming a correspondence list of the start positions of the scanner 105, the printed material, the photosensitive drum 193, and the intermediate belt 194.

[0031] In S403, the scan image input unit 303 acquires image data (scanned image) by scanning the printed matter. In this embodiment, it is assumed that the scan image shown in Fig. 7 is input. In the illustrated scan image, the printed matter is tilted counterclockwise due to a conveyance position shift, and defects 701, 702, and 703 have occurred on the output image. In this embodiment, the scan image is grayscale image data with 8 bits per pixel.

[0032] In S404, the image correction unit 304 corrects the misalignment of the scanned image due to misalignment of the printed matter transported on the transport path 110 and flexure of the paper. Details of this image correction process will be described later with reference to Fig. 8. In this embodiment, the tilt due to the misalignment of the printed matter transported as shown in Fig. 9 is corrected, and a corrected image is generated in which the area outside the print paper is trimmed.

[0033] In S405, the defect detection unit 305 detects pixel areas in the defect image, which are generated based on the difference between the corrected image and the reference image, as defects, where the pixel areas have large difference values. Details of the defect detection process will be described later with reference to Fig. 10. In this embodiment, the defect image shown in Fig. 11 is generated based on the difference between the corrected image and the reference image, and pixel areas of defects 701, 702, and 703 are detected as defect areas.

[0034] In S406, the repeatability determination unit 306 calculates, from the phase information, the occurrence positions of defects on the image forming body, such as the photosensitive drum 193 and the intermediate belt 194, which correspond to the defective pixel positions detected in the multiple scanned images, and determines the repeatability of the defects detected between the scanned images. Details of the repeatability determination process will be described later with reference to FIG. 12. In this embodiment, the positions of defects detected on the i-th scanned image and the (i+1)-th scanned image are compared based on the phase information, and the defects 701 and 703 shown in FIG. 13 are determined to be repeatable defects. The determination result is output to the UI panel 108 or the printing device 190, and the process ends.

[0035] [Operation of image correction unit 304] Next, the image correction process in S404 will be described in detail with reference to the flowchart in FIG.

[0036] In S801, the image correction unit 304 corrects the misalignment of the scanned image due to misalignment of the printed matter transported on the transport path 110 and the flexure of the paper. In this embodiment, the image correction unit 304 detects feature points on the reference image and the scanned image using a known template matching technique, and calculates an affine transformation matrix for moving and rotating to match pixel positions between the feature points. Then, the image correction unit 304 uses the calculated affine transformation matrix to generate an image in which the pixel positions of the scanned image are matched to the pixel positions of the reference image. In this embodiment, as shown in FIG. 14, pixel areas 1401 to 1404 are detected as feature points, and an affine transformation process is performed to generate a registered image as shown in FIG. 15.

[0037] In S802, the image correction unit 304 generates an image by trimming the aligned image with the image area of ​​the reference image, and ends the process. In this embodiment, the aligned image shown in Fig. 15 is trimmed with the reference image area shown in Fig. 5 to generate the corrected image shown in Fig. 9.

[0038] [Operation of defect detection unit 305] Next, the defect detection process in S405 will be described in detail with reference to the flowchart in FIG.

[0039] In S1001, the defect detection unit 305 generates a difference image ΔIMG, whose pixel value is the absolute value of the difference between the pixel value of the corrected image and the pixel value of the reference image. th By performing binarization processing, the defect image IMG def Since this is a binarization process, the defect image IMG def Each pixel that composes the threshold I th is a threshold for detecting a defective area, and in this embodiment, I thIn this embodiment, the pixel area shown in FIG. 16A, in which the absolute value of the difference between the corrected image and the reference image is greater than the threshold value Ith, has a pixel value of 255 and a threshold value I th A binarized image with a pixel value of 0 will be generated for the following pixel areas.

[0040] In S1002, the defect detection unit 305 detects a defect image IMG def Each of the above defect areas is labeled, and the process ends. In this embodiment, the defects 701, 702, and 703 shown in FIG. 16B are labeled with defect area numbers "1," "2," and "3."

[0041] [Operation of reproducibility determination unit 306] Next, the repeatability determination process in S406 in FIG. 4 will be described in detail with reference to the flowchart in FIG.

[0042] In S1201, the reproducibility determination unit 306 receives the scanned image IMG scan An image forming body area image IMG showing the positions of the defects detected above on the image forming body such as the photoconductor drum 193 and the intermediate belt 194. cur Specifically, the repeatability determination unit 306 generates the start position Y s and the start position Y of the photosensitive drum 193 d From the start position Y of the photosensitive drum 193 on the defective image, d Pixel position Y corresponding to d_cur In this embodiment, the pixel position Y d_cur corresponds to the start position of the photosensitive drum 193. Furthermore, the pixel position Y d_cur Based on this, the defect image IMG def In this embodiment, the divided image IMG shown in FIG. cur1 , IMG cur2 , IMG cur3is generated as an area image showing the position of a defect occurring on the photosensitive drum 193. The areas 1701 and 1702 are represented by the defect image IMG def Split image IMG not shown above cur1 , IMG cur3 This is the upper image area, which in this embodiment is an image area with a pixel value of "128."

[0043] The repeatability determination unit 306 determines the repeatability of the scanned image IMG between these area images based on the following formula (2): scan 1 shows an image carrier area image IMG indicating the location on the image carrier of the defects detected above. cur Generate.

[0044]

number

[0045] In this embodiment, as shown in FIG. 17(c), a divided image IMG cur1 , IMG cur2 , IMG cur3 From the image forming body area image IMG cur is generated.

[0046] In S1202, the repeatability determination unit 306 stores in the RAM 102 or the main storage device 104 an image forming body area image IMG indicating the positions of the defects already detected on the image forming body area. pre Determine whether the IMG pre If the reproducibility determination unit 306 stores the scanned image IMG scan It is determined that the reproducibility of the above defect can be determined, and the process proceeds to S1203. pre In the present embodiment, when the pixel position Y corresponding to the start position of the photosensitive drum 193 is not stored in the defect image shown in FIG. d_pre Based on this, the period of the photosensitive drum 193 is 2πr, and the IMG pre1 , IMG pre2The regions 1801 and 1802 are divided images IMG that are not shown on the defect image. pre1 , IMG pre2 In this embodiment, it is assumed that the pixel value of the image forming body area is "128". Furthermore, as shown in FIG. 18(c), it is assumed that an image forming body area image IMGpre, which is generated according to the formula (2) and indicates the position on the image forming body area of ​​the defect that has already been detected, is stored in advance. Image IMG pre Above, defects 1803, 1804, and 1805 have occurred.

[0047] In S1203, the repeatability determination unit 306 initializes a variable i representing a defective area number to "1". In S1204, the repeatability determination unit 306 calculates the positional deviation amount ΔS of the defective area i according to the following formula (3): i th Determine whether the following is satisfied.

[0048]

number

[0049] In this embodiment, the positional deviation amount of the defect area i is IMG cur The area S of the defect region i on i The area of ​​the defect area i remaining on the difference image, ΔS i It is calculated from the ratio of S th is a threshold value for determining the reproducibility of the defective area, and in this embodiment, S th = 0.1. ΔS i th If the above condition is satisfied, the repeatability determination unit 306 determines that the defect area i is a defect that repeats, and proceeds to step S1205. i th If the above is not satisfied, the repeatability determination unit 306 determines that the defect area i is a randomly occurring defect, and proceeds to step S1206. In this embodiment, the image forming body area image IMG cur And, IMG pre ​​​19 is generated as an image having pixel values ​​that are the absolute values ​​of the differences between the defects 702 and 1804. cur And, IMG pre Since the defect was not reproduced at the same position in the image, the absolute value of the difference is 255. In the pixel areas of defects 701 (1803) and 703 (1805), cur And, IMG pre Since the defect was repeatedly reproduced, the absolute value of the difference is 0. Therefore, the positional deviations of defective areas 1 and 2, ΔS1=0 and ΔS2=0 th As a result, the defects 701 and 702 occurring in the defect areas 1 and 2 are determined to be defects that repeatedly reappear.

[0050] In S1205, the reproducibility determination unit 306 stores the defect area i as a reproducible defect area in which defects repeatedly reoccur in the RAM 102 or the main storage device 104. In S1206, the reproducibility determination unit 306 increments (updates) the variable i representing the defect area number by "1".

[0051] In S1207, the repeatability determination unit 306 determines whether i>n is satisfied for the defective area number i. If it is determined that i>n is satisfied, the repeatability determination unit 306 determines that the determination process has been performed for all defective areas, and proceeds to S1208. On the other hand, if it is determined that i>n is not satisfied, the repeatability determination unit 306 returns the process to S1204.

[0052] In S1208, the reproducibility determination unit 306 cur an image forming body area image IMG showing the positions of the already detected defects on the image forming body area; pre The result is stored in the RAM 102 or the main storage device 104, and the process ends.

[0053] 13 is an image showing pixel positions of defects that are determined to repeatedly reoccur in the repeatability determination process of this embodiment. In this embodiment, defects 701 and 703 are determined to be defects that repeatedly reoccur, and a warning is given to the user by displaying the defect area on the UI of a display device (not shown).

[0054] ​ By carrying out the image processing described above, it is possible to determine whether or not a defect is reproducible from the scanned image, even if the position at which the defect is reproduced varies depending on the cycle length of the photosensitive drum and intermediate transfer belt, the length of the paper, the image formation timeline, etc.

[0055] In this embodiment, an 8-bit grayscale image is used, but an RGB color image may be used. The number of bits may be 16 bits, and there is no limitation on the number of channels or bits of the image data.

[0056] In addition, in this embodiment, the positions of the images are aligned by affine transformation during the alignment process, but projective transformation may also be used, and the method is not particularly limited to geometric transformation processing.

[0057] In addition, in this embodiment, the position shift of a defect detected between multiple defect images is calculated from the ratio of the area remaining on the difference image between the multiple defect images to the area of ​​the defect region, but it may also be calculated from the shift in the center of gravity of the defect region, and the method of calculating the position shift of a defect is not particularly limited.

[0058] In this embodiment, the reproducibility of defects was judged using a printing machine that outputs images using one photosensitive drum and one intermediate belt, but for example, the number of photosensitive drums may be four, CMYK, and there is no particular limitation on the number or configuration of the image forming bodies for which reproducibility is judged.

[0059] In this embodiment, the user is warned by displaying an image of a defective area that is determined to be repeatedly reproduced on the UI, but error information regarding the repeated occurrence of a defect may be output to the printing machine 190 and the printing job of the printing machine 190 may be stopped, and the output method is not particularly limited.

[0060] [Second embodiment] In the first embodiment, the presence or absence of reproducibility of a defect caused by a scratch on the photosensitive drum 193 having a period shorter than the height of the defective image is determined. However, when a defect occurs repeatedly due to a scratch on the intermediate belt 194 having a period longer than the height of the defective image, the defect is detected on the defective image every several sheets of printing paper. As a result, when a defect is compared between a previous and a next defective image, there is a possibility that the reproducibility is erroneously determined. Therefore, in the second embodiment, a method for determining with high accuracy the reproducibility of a defect caused by a scratch on the intermediate belt 194 having a period longer than the height of the defective image by masking a pixel area corresponding to the defective image within the image forming body area as a determination area will be described.

[0061] In this embodiment, the scanned image shown in FIG. 20(a) is input. The scanned image is tilted counterclockwise due to a misalignment of the printed matter conveyed, resulting in an output image with defects 2001-2004. The scanned image is corrected and the difference between the scanned image and a reference image is calculated to generate a defect image shown in FIG. 20(b), in which the pixel regions of the defects 2001-2004 are detected as defective regions. Furthermore, pixel position Y 1 corresponding to the start position of the intermediate belt 194 in FIG. 20(b) is corrected and the defect image shown in FIG. 20(b) is generated. b_cur Based on this, the period Y of the intermediate belt 194 b The defect image segmented by the above is shown in Fig. 20(c). cur1 , IMG cur2 The regions 2005 and 2006 are the divided images IMG that are not shown on the defect image IMGdef. cur1 , IMG cur3 In this embodiment, this is the image area with a pixel value of "128." cur1 , IMG cur2 From the image forming body region image IMG generated according to the formula (2), cur It is. IMG cur The upper area 2007 is the defect image IMG def This is the image area that is not shown on the screen and has a pixel value of "128."

[0062] [Operation of reproducibility determination unit 306] The flow of the repeatability determination process of the second embodiment will be described with reference to Fig. 21. Since the steps other than S2101 to S2104 in this figure are the same as those in Fig. 12 in the first embodiment, the following will describe the differences.

[0063] In step S2101, the repeatability determination unit 306 generates an image IMG indicating an area for determining the repeatability of a defect detected on a defect image. cur_mask The determination region image generation process will be described in detail later with reference to FIG. 22. In this embodiment, the repeatability determination unit 306 generates an IMG cur Defective image IMG in the upper image area def An image is generated in which the pixel area excluding area 2007, which is a pixel area not shown in the image, is used as the area for judging reproducibility. The judgment area image is a binary image in which the area for judging reproducibility has a pixel value of "1" and the area 2007, which is not judged, has a pixel value of "0."

[0064] In S2102, the repeatability determination unit 306 generates an image forming body area image IMG pre Reproducibility judgment area IMG pre_mask And the IMG generated by S2101 cur_mask Image of common area with mask In this embodiment, IMG pre_mask 24(a) is an image in which the pixel area excluding the area 2401 shown in FIG. 24(a) is used as the area for determining the reproducibility. mask is a binary image in which the pixel area excluding the areas 2007 and 2401 shown in FIG. 24B is the area for judging the reproducibility. In this embodiment, the image shown in FIG. 25A is an image forming body area image IMG pre The image IMG is stored in the RAM 102 or the main memory device 104. cur and image IMG pre24(b) is an image showing the position of a defect determined to be a repeating defect by comparing the common area image IMG 2001 and the common area image IMG 2002. As in the first embodiment, a defect 2001 detected at the same position on the image forming body area image is determined to be a repeating defect. mask By judging the reproducibility in the image IMG cur In this case, the defect 2004, which is detected only in a partial area, can be determined to be a defect that repeatedly reappears.

[0065] In S2103, the reproducibility determination unit 306 determines whether the image IMG pre Image IMG in the pixel area above cur The IMG is the area where reproducibility is judged. cur_mask For pixel area, image IMG pre The pixel values ​​of the image IMG cur In this embodiment, the pixel values ​​of the image IMG shown in FIG. pre In contrast, IMG cur_mask In the pixel domain, an image IMG cur By overwriting and updating the pixel values ​​of the image IMG pre The randomly generated defect 2501 has disappeared and the image IMG cur A defect 2002 that has randomly occurred in is added. Also, a defect image of a pixel region in region 2502 is added, and a defect 2003 is added.

[0066] In S2104, the reproducibility determination unit 306 determines the reproducibility of the region image IMG pre_mask and image IMG cur_mask The region obtained by taking the union of pre_mask Then, the process is terminated.

[0067] In this embodiment, the image IMG shown in FIG. pre_mask In contrast, the image IMG shown in FIG. cur_mask By overwriting and updating with the union of the image IMG pre_maskThe image shown in FIG. 27 is an image in which the entire image is the area to be determined.

[0068] [S2101 Judgment area image IMG cur_mask Generation process flow Next, the details of the determination area image generation process in S2101 will be described with reference to the flowchart in FIG.

[0069] In S2201, the reproducibility determination unit 306 determines whether the image IMG cur The defect detection area image R is obtained by binarizing the pixel values ​​of the pixel value = 128 area to "0" and the pixel values ​​of the pixel value ≠ 128 area to "1". b In this embodiment, an image in which pixel regions other than region 2007 shown in FIG. 23 are designated as defect detection regions is generated by binarization processing.

[0070] In S2202, the reproducibility determination unit 306 b , Image IMG cur Image of the area to judge the reproducibility of the above cur_mask and the process is terminated.

[0071] The above repeatability determination process is repeatedly performed on the first, second, ..., i-1th, ith, and i+1th scanned images. Therefore, for example, in the i-1th scanned image, the image shown in FIG. pre 28(b) is stored as image IMG pre Fig. 28(c) is an image showing pixel positions of defects determined to be repeatedly reproduced in this embodiment. A defect 2003 that is not captured in the image forming body region image in the i-th scanned image in Fig. 25(a) is determined to be a repeatedly reproduced defect.

[0072] By performing the image processing described above, the reproducibility of the defect can be determined with high accuracy even in the case of repeated defects caused by scratches on the intermediate belt 194 having a period longer than the height of the defect image.

[0073] [Modification] (If the defect location is in the white area of ​​the paper, it is excluded from the judgment area) A modified example of the determination area image generation process in S2101 will be described below with reference to the flowchart in FIG.

[0074] In the first and second embodiments, the presence or absence of defect reproducibility is judged for an image in which a pattern is output over the entire image. However, color loss caused by insufficient color material adhering due to scratches on the photosensitive drum 194 or the like does not occur in the paper white area where no color material is originally attached, so if the output image includes a paper white area, the reproducibility of defects caused by color loss may be erroneously judged. Therefore, in this modified example, a method for highly accurately judging the reproducibility of defects even when the output image includes a paper white area by excluding pixel areas corresponding to the paper white area in the image of the image forming body area from the judgment area will be described.

[0075] In this modification, the images shown in Fig. 30(a) to (c) are input as the scanned images of the i-1, i, and i+1-th printed matter. The scanned images shown in the figures show an example in which the original printed matter is tilted counterclockwise due to a misalignment in the conveying position. The scanned images show that defects 3001 to 3006 have occurred. Areas 3007 to 3009 are white paper areas on the i-1 to i+1-th scanned images. The scanned images are corrected and the difference from the reference image is calculated to generate the defect images shown in Fig. 30(d) to (f), and the pixel areas of defects 3001 to 3006 are detected as defective areas. Furthermore, the pixel positions Y 1 to Y 2 corresponding to the start position of the intermediate belt 194 in Figs. 30(d) to (f) are b_cur Based on this, an image forming body region image shown in Fig. 30(g) to (i) is generated. Regions 3010 to 3012 in Fig. 30(g) to (i) are image regions that are not shown in the defect image, and are image regions with a pixel value of 128.

[0076] [S2101 Judgment area image IMG cur_mask Flow of generation process] Below, the judgment area image IMG cur_maskA modified example of the generation process will be described with reference to the flowchart of FIG.

[0077] Determination region image IMG of S2101 in this modified example cur_mask The flow of the generation process is the same as that described with reference to FIG. 22 except for S2901 and S2902, so the description will be omitted.

[0078] In S2901, the repeatability determination unit 306 applies a threshold value I p By performing binarization processing in step I, a paper white area image is generated. p is a threshold value for detecting the paper white area, and in this embodiment, I p In this embodiment, the threshold value I p 31(a)-(c) are generated by performing the binarization process. The paper white areas 3007-3009 are binarized with a pixel value of 255, and the other picture areas are binarized with a pixel value of 0. Next, the repeatability determination unit 306 performs a geometric transformation using the affine transformation matrix calculated in the correction process of S404, and generates an image trimmed with the reference image area. Furthermore, the repeatability determination unit 306 performs a geometric transformation using the pixel position Y b_cur In this embodiment, an image forming body region image is generated in which the pixel value is 255 in regions 3007-3009 and the pixel value is 128 in regions 3010-3012, as shown in Fig. 31(d)-(f). This image is subjected to binarization processing in which the pixel value = 255 is set to a pixel value of "0" and the pixel value ≠ 255 is set to a pixel value of "1", thereby generating a paper white region image R p In this embodiment, a paper white area image R p is a binary image in which the pixel value is "1" in areas 3007 to 3009 and the pixel value is "0" in the other areas, as shown in FIGS. 31(g) to (i).

[0079] In S2902, the reproducibility determination unit 306 p The binary image is inverted and the image not(R p ) and defect detection area image R bThe repeatability determination unit 306 generates a common area image (an image of the logical product) of the two images. cur Image of the area to judge the reproducibility of the above cur_mask In this embodiment, the binary image in which the pixel value is 1 in the regions 3101 to 3103 shown in Figs. 31(j) to (l) is set as the determination region image IMG cur_mask It will be generated as:

[0080] The above-mentioned repeatability determination process is executed for the (i-1)th, i-th, and (i+1)th scanned images. In the (i-1)th and i-th scanned images, the images shown in (g) and (h) in FIG. pre 31(j) and (k) are stored as the judgment region IMG cur_mask 32(a) is stored as an image IMG pre As a result, as shown in FIG. 32(b), the defect 3001 (3006) that did not occur in the paper white area of ​​the image forming body area image in the i-th scanned image is determined to be a defect that repeatedly reproduces in the (i+1)-th scanned image.

[0081] By carrying out the image processing described above, even if the output image contains a paper-white area, it is possible to determine the reproducibility of defects due to color loss with high accuracy.

[0082] [Third embodiment] In the first and second embodiments, the presence or absence of reproducibility of defects caused by scratches on the image forming body such as the photosensitive drum 193 and the intermediate belt 194 is judged. However, when a sensor defect occurs, even if there is no defect in the actual output image itself, it may be erroneously judged that the defect is repeatedly reproduced on the scanned image. Therefore, in the third embodiment, a method of separating defects caused by scratches on the image forming body from sensor defects and executing separate processing will be described. As a specific example of separate processing, when a sensor defect is detected, since there is no defect in the output image itself, a process of passing through and outputting an image, or a process of displaying a sensor defect error on the UI to warn the user may be executed.

[0083] In this embodiment, the images shown in Fig. 33(a) and (b) are input as the i-th and (i+1)-th scanned images. In the illustrated example, the prints on the i-th and (i+1)-th scanned images are tilted counterclockwise and clockwise, respectively, due to a misalignment in the conveying position. On the scanned images, streak-like defects 3301 and 3304 caused by a sensor defect are shown across the top and bottom of the scanned image. Furthermore, streak-like defects 3303 and 3306 caused by scratches on the intermediate belt 194 are shown across the top and bottom of the paper. Randomly occurring defects 3302 and 3305 are also shown.

[0084] The scanned image is subjected to a correction process, and the difference between the scanned image and the reference image is calculated to generate the defect images shown in FIGS. 33(c) and (d), in which the pixel areas of defects 3301 to 3306 are detected as defect areas.

[0085] [Operation of reproducibility determination unit 306] The flow of the reproducibility determination process in the third embodiment is the same as that described in the first and second embodiments with reference to Fig. 12 and Fig. 21, except for S3401. Hereinafter, the reproducibility determination process in the third embodiment will be described with reference to Fig. 34.

[0086] In S3401, the repeatability determination unit 306 compares the defect images corresponding to the i-th and (i+1)-th scan images to determine whether the detected defect is a defect caused by a sensor defect. Details of the sensor defect determination process will be described later with reference to Fig. 35. In this embodiment, the defect image shown in Fig. 36 is generated by comparing the i-th and (i+1)-th defect images, and the pixel area of ​​the defect 3301 (3304) is detected as a sensor defect.

[0087] [S3401 Sensor defect determination process flow] The sensor defect determination process in S3401 will be described in detail below with reference to the flowchart in FIG.

[0088] In S3501, the repeatability determination unit 306 stores in the RAM 102 or the main storage device 104 a defect image IMG indicating the position of a defect that has already been detected on a reference image. def_pre Determine whether the IMG def_pre If the reproducibility determination unit 306 stores the scanned image IMG scan It is determined that the presence or absence of a sensor defect on the sensor 1 can be determined, and the process proceeds to S3502. def_pre If the defect image IMG shown in FIG. 33(c) is not stored, the repeatability determination unit 306 determines that it is impossible to determine whether or not there is a sensor defect, and proceeds to step S3509. def_pre is generated, and defects 3301 to 3303 are detected.

[0089] In S3502, the repeatability determination unit 306 initializes a variable i, which indicates the number of the defective area, to "1." In S3503, the repeatability determination unit 306 calculates the positional deviation amount ΔS of the defective area i on the defect image according to the following equation (4): def ≧S th Determine whether the following is satisfied.

[0090]

number

[0091] In S3504, the repeatability determination unit 306 receives the defect image IMG def_pre , IMG def_cur Image IMG is an image obtained by performing a geometric inverse transformation using the inverse matrix of the affine transformation matrix calculated in the correction process of S404. inv_pre , IMG inv_cur In this embodiment, the defect images IMG shown in FIGS. def_pre , IMG def_cur By performing a geometric inverse transformation on the image IMG shown in FIG. inv_pre , IMG inv_curis generated. Defects 3001 and 3004 caused by sensor defects have defects detected on a straight line at the pixel position x = x0 in the x direction. Since defects 3302 and 3305 are randomly occurring defects, defects are detected on different pixel regions. Also, for defects 3003 and 3006, due to the misalignment of the conveyance position of the printed matter, defects are detected on different pixel regions. In S3505, the reproducibility determination unit 306 determines whether the displacement amount ΔS inv <S th of the defect region i on the geometrically inverse-transformed defect image satisfies the following.

[0092] [Number] Here, S th is a threshold for determining the reproducibility of the defect region. In this embodiment, Sth = 0.1. When ΔS inv <S th is satisfied, the reproducibility determination unit 306 determines that the defect region i is a sensor defect and transfers the process to S3506. When ΔSinv < Sth is not satisfied, the reproducibility determination unit 306 determines that the defect region i is a randomly occurring defect and transfers the process to S3507. In this embodiment, by taking the absolute value of the difference between the geometrically inverse-transformed defect image IMG inv_pre and IMG inv_cur , the image shown in FIG. 37(d) is generated. In the image of the same figure, defect 3001 (3304) is determined to be a sensor defect, and defects 3302 and 3305 are determined to be randomly occurring defects.

[0093] In S3506, the reproducibility determination unit 306 stores the defect region i as a sensor defect region in the RAM 102 or the main storage device 104.

[0094] In S3507, the repeatability determination unit 306 updates the variable i indicating the defective area by incrementing it by "1". In S3508, the repeatability determination unit 306 determines whether i>n is satisfied for the defective area number i. If i>n is satisfied, it is determined that the sensor defect determination process has been performed for all defective areas, and the process proceeds to S3509. If i>n is not satisfied, the repeatability determination unit 306 returns the process to S3503. In S3509, the repeatability determination unit 306 determines whether the IMG def_cur The defect image IMG shows the positions of the already detected defects on the reference image. def_pre The result is stored in the RAM 102 or the main storage device 104, and the process ends.

[0095] 36 is an image showing pixel positions of defects that have been determined to be sensor defects by the sensor defect determination process of this embodiment. In this embodiment, the defect 3001 (3004) is determined to be a sensor defect, and a sensor defect error is displayed on the UI to warn the user.

[0096] By performing the image processing described above, even if repeated defects are detected in the scanned image due to a sensor defect, it is possible to distinguish between defects caused by scratches on the image forming body and sensor defects and perform separate processing.

[0097] (Other embodiments) The present invention can also be realized by a process in which a program for implementing one or more of the 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. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.

[0098] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0099] 301: Reference image input section; 302: Phase information input section; 303: Scan image input section; 304: Image correction section; 305: Defect detection section; 306: Reproducibility determination section

Claims

1. a reference image input means for inputting a reference image; a scan image input means for acquiring a plurality of scan images obtained by sequentially scanning a plurality of recording media on which images to be inspected are recorded and output from a printing device by a sensor; a phase information input unit for inputting phase information of an image forming body of the printing device; a defect detection means for aligning the reference image and the plurality of scanned images by transformation using a matrix, and detecting defects on the plurality of scanned images after the alignment; and a determination unit that determines, based on the phase information, when a positional deviation amount of the defect between the plurality of scanned images after the alignment is less than a threshold value, that the defect is a defect reproduced due to the image forming body, The image processing device is characterized in that, when the amount of deviation is equal to or greater than the threshold, the judgment means transforms the multiple aligned scan images using an inverse matrix of the matrix, and when the amount of deviation of the position of the defect between the transformed multiple scan images is less than a threshold, the judgment means judges that the defect is a defect reproduced due to the sensor.

2. 2. The image processing apparatus according to claim 1, wherein the defect detection means detects the defect by comparing pixel values ​​of the reference image with those of each of the plurality of scanned images.

3. 3. The image processing apparatus according to claim 1, wherein the determining means determines the reproducibility of the defect based on a position of the defect on the recording medium, the position being calculated based on the phase information.

4. The image forming body of the printing device includes a photosensitive drum according to an electrophotographic method, an intermediate transfer belt for transferring a toner image formed on the photosensitive drum, and a transfer roller for transferring the toner image on the intermediate transfer belt onto a recording medium; The phase information is information that associates the rotational phase of the image forming body with the reading pixel position of the scanner of the scan image input means, the information being obtained by synchronizing the printing device and the image processing device through communication with the printing device.

4. The image processing device according to claim 1, wherein the first and second inputs are input to the image processing apparatus.

5. 5. The image processing apparatus according to claim 1, wherein the scanned image input means includes a correction means for correcting the image obtained by scanning in accordance with a positional deviation associated with conveyance of a recording medium on which the image is recorded.

6. a reference image input step of inputting a reference image; a scan image input process for acquiring a plurality of scan images obtained by sequentially scanning a plurality of recording media on which images to be inspected are recorded and output from a printing device by a sensor; a phase information input step of inputting phase information of an image forming body of the printing device; a defect detection step of aligning the reference image and the plurality of scanned images by transformation using a matrix, and detecting defects on the plurality of scanned images after the alignment; and a determination step of determining, based on the phase information, that the defect is a defect reproduced due to the image forming body when a positional deviation amount of the defect between the plurality of scanned images after the alignment is less than a threshold value, A control method for an image processing device, characterized in that in the judgment process, if the amount of deviation is equal to or greater than the threshold, the multiple aligned scan images are transformed using an inverse matrix of the matrix, and if the amount of deviation of the position of the defect between the transformed multiple scan images is less than a threshold, it is determined that the defect is a defect that is reproduced due to the sensor.

7. A program for causing a computer to execute each of the steps recited in claim 6 when the program is read and executed by the computer.

Images