Image forming apparatus, control method for image forming apparatus, and program

Abstract

To solve the problem that accuracy in alignment accuracy cannot be enhanced so that even a good printed matter may be determined to be a failure, in inspecting an image with fewer characteristic points.SOLUTION: An image forming device, in inspecting a pre-registered correct answer image and a scanned image obtained by scanning a printed matter while aligning the images, using respective characteristic points of the images, displays, on an operation part, a screen which can select a plurality of modes which include a first mode in which the alignment is performed using a position of a paper top of an area showing at least the printed matter having the scanned image and a position of a paper top of the correct answer image and a second mode in which inspecting means does not inspect the images, when characteristic points of the correct answer image are fewer than a predetermined number.SELECTED DRAWING: Figure 8

Description

[Technical Field]

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

[0002] In recent years, a printing system has become known in which an image forming apparatus including a printing device and an inspection device can inspect sheets printed by the printing device using the inspection device while they are being transported. In the inspection of printed sheets, the inspection device reads an image of the transported printed sheet and determines whether the printed sheet is normal or not through image analysis of the read image. The inspection device can detect, for example, missing barcodes or ruled lines, printing defects, etc.

[0003] As a method for creating a correct image (reference image) to be used in image analysis, a method is known in which a printed sheet of sufficient quality that has been printed in advance as a correct image is read by an inspection device and used.

[0004] Patent Document 1 describes an inspection device that, when comparing a correct image for inspection with a printed image obtained by reading a conveyed printed sheet, aligns the images based on feature points extracted from each image. In this inspection device, if a sufficient number of feature points are not extracted to align the images, the inspection device aligns the images using information about the paper vertices of the printed image and then performs the inspection. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-135197 Summary of the Invention [Problem to be solved by the invention]

[0006] When an image is printed on a recording sheet, slight misalignment of the print position can occur. If alignment is performed using feature points, the slight misalignment of the print position is corrected and the image passes inspection, but if alignment is performed using the vertices of the paper, the slight misalignment of the print position can be detected as a difference. In Patent Document 1, if sufficient feature points are not extracted, the only option available for aligning images is to use information about the vertices of the paper of the printed image. Therefore, for users who want to tolerate slight misalignment of the print position, the inspection often results in a print defect due to slight misalignment, which reduces convenience. [Means for solving the problem]

[0007] The image forming apparatus of the present invention comprises a display control means for displaying a screen on an operation unit, a printing means for printing an image on a recording sheet, a generating means for reading a printed matter on which the image has been printed by the printing means and generating a scanned image, an extracting means for extracting feature points from the scanned image and a reference image, a positioning means for aligning the scanned image with the reference image using the feature points extracted from the scanned image and feature points extracted from the reference image that has been registered in advance, an inspecting means for inspecting the printed matter using the reference image and the scanned image after the positioning, and a processing means for performing processing according to a method selected from a plurality of methods including at least a first method and a second method when the number of feature points in the reference image is less than a predetermined number. and when the number of feature points of the correct image extracted by the extraction means is less than the predetermined number, the display control means selects the selected method as follows: at least The method is characterized by displaying a screen that allows the user to select one of a plurality of modes, including the first method of performing the alignment using the positions of the paper vertices of the area showing the print of the scanned image of the scanned image and the positions of the paper vertices of the correct image, and the second method of not performing inspection by the inspection means. [Effects of the Invention]

[0008] According to the present invention, the user can select an inspection processing method for a target image and a printed image from which sufficient feature points for alignment are not extracted. [Brief explanation of the drawings]

[0009] [Figure 1] Example of an overall diagram of a printing system [Figure 2] An example of a block diagram showing the system configuration of a printing system [Figure 3] An example of a schematic cross-sectional view of the mechanism of an image forming apparatus [Figure 4] An example of a flowchart for the entire inspection process [Figure 5] (a) An example of a captured image. (b) An example of an image obtained by image transformation from the captured image. (c) An example of a diagram showing extracted feature points. (d) An example of an enlarged view of a feature point. [Figure 6] (a) An example of an image with few feature points. (b) An example of feature points extracted from an image with few feature points. [Figure 7] An example of a warning screen UI screen [Figure 8] An example of the UI screen for settings for images with few feature points [Figure 9] An example of a flowchart for detailed settings of the inspection method [Figure 10] An example of the UI screen for test settings [Figure 11] An example of a process flow diagram for an inspection invitation that performs inspection processing [Figure 12] An example of a processing flow diagram for an inspection device that compares with a correct image [Figure 13] An example of a processing flow diagram for inspection level coordinate information update processing [Figure 14] An example of inspection level coordinate information [Figure 15] 10 is a flowchart illustrating an example of detailed setting of an inspection method according to a second embodiment. [Figure 16] 10 is an example of a UI screen for test settings according to the second embodiment. [Figure 17] 10 is an example of a flowchart of an entire inspection process according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

[0011] In the following description, the external controller may also be called an image processing controller, a digital front end, a print server, a DFE, etc. The image forming apparatus may also be called a multifunction device, a multifunction peripheral, or an MFP.

[0012] [First embodiment] 1 is an overall diagram of the hardware configuration of an image processing system according to this embodiment. The image processing system includes an image forming apparatus 101 and an external controller 102. The image forming apparatus 101 and the external controller 102 are communicatively connected via an internal LAN 105 and a video cable 106. Note that the video cable 106 may not have this configuration, and its function may be substituted by the internal LAN 105. The external controller 102 is communicatively connected to a client PC 103 via an external LAN 104, and a print instruction is sent from the PC 103 to the external controller 102.

[0013] A printer driver that has the function of converting print data into a print description language that can be processed by the external controller 102 is installed in the client PC 103. A user who wants to print can issue a print instruction from various applications via the printer driver. The printer driver sends print data to the external controller 102 based on the print instruction from the user. When the external controller 102 receives a print instruction from the PC 103, it performs data analysis and rasterization processing, and inputs the print data to the image forming apparatus 101 to issue a print instruction.

[0014] Next, a description will be given of the image forming apparatus 101. The image forming apparatus 101 is connected to a plurality of devices with different functions, and is configured to be capable of complex printing processes such as bookbinding.

[0015] The printing device 107 forms an image using toner on a recording sheet (paper) transported from a paper feed unit located below the printing device 107. The configuration and operating principle of this printing device 107 are as follows: A beam of light, such as a laser beam, modulated according to image data is reflected by a rotating polygon mirror or other such mirror and irradiated onto a photosensitive drum as scanning light. The electrostatic latent image formed on the photosensitive drum by the laser beam is developed with toner, and the toner image is transferred onto a recording sheet attached to a transfer drum. This series of image formation processes is performed sequentially for yellow (Y), magenta (M), cyan (C), and black (K) toners, forming a full-color image on the paper. The paper on the transfer drum with the full-color image formed thereon is transported to a fuser. The fuser includes rollers, belts, etc., and incorporates a heat source, such as a halogen heater, within the rollers. The fuser fuses the toner on the paper with the transferred toner image by heat and pressure, fusing it to the paper.

[0016] An inserter 108 is used to insert an insertion sheet. A sheet can be inserted from the inserter 108 at any position into a group of sheets printed by the printing device 107 and transported.

[0017] The inspection device 109 is a device for reading an image of the conveyed paper and comparing it with a pre-registered correct image to determine whether the printed image is normal.

[0018] Reference numeral 110 denotes a large-capacity stacker capable of stacking a large volume of sheets. Reference numeral 111 denotes a finisher that performs finishing processes on the conveyed sheets. It is capable of performing finishing processes such as stapling, punching, and saddle stitching, and discharges the sheets to a paper discharge tray.

[0019] 1 is configured such that the external controller 102 is connected to the image forming apparatus 101, but the present invention is not limited to a configuration in which the external controller 102 is connected. That is, the image forming apparatus 101 may be connected to an external LAN 104, and print data that can be processed by the image forming apparatus 101 may be sent from a client PC 103. In this case, data analysis and rasterization processing are performed in the image forming apparatus 101, and print processing is executed.

[0020] FIG. 2 is a block diagram showing a system configuration of the image forming apparatus 101, the external controller 102, and the client PC 103. As shown in FIG.

[0021] First, the configuration of the printing device 107 of the image forming apparatus 101 will be described. The printing device 107 of the image forming apparatus 101 is composed of a communication I / F 217, a LAN I / F 218, a video I / F 220, a HDD 221, a CPU 222, a memory 223, an operation unit 224, and a display 225. The printing device 107 of the image forming apparatus 101 further includes a document exposure unit 226, a laser exposure unit 227, an image creation unit 228, a fixing unit 229, and a paper feed unit 230. Each of these components is connected via a system bus 231.

[0022] The communication I / F 217 is connected to the inserter 108, the inspection device 109, the large-capacity stacker 110, and the finisher 111 via a communication cable 254, and performs communication for controlling each device.

[0023] The LAN I / F 218 is connected to the external controller 102 via the internal LAN 105, and performs communication of print data and the like.

[0024] The video I / F 220 is connected to the external controller 102 via the video cable 106, and performs communication of image data and the like.

[0025] The HDD 221 is a storage device that stores programs and data. The CPU 222 comprehensively controls image processing and printing based on the programs and other data stored on the HDD 221. The memory 223 stores programs and image data required for the CPU 222 to perform various processes and functions as a work area. The operation unit 224 accepts various settings and operation instructions from the user. The display 225 displays the image processing device's settings and the processing status of print jobs. The document exposure unit 226 reads documents when using the copy and scan functions. The document data is read by shining an exposure lamp on the paper placed by the user and capturing an image with a CMOS image sensor. The laser exposure unit 227 is a device that performs primary charging and laser exposure to irradiate the photosensitive drum with laser light to transfer a toner image. The laser exposure unit 227 first performs primary charging, charging the surface of the photosensitive drum to a uniform negative potential. Next, a laser driver irradiates the photosensitive drum with laser light, adjusting the reflection angle with a polygon mirror. This neutralizes the negative charge in the irradiated area, forming an electrostatic latent image. The image-forming unit 228 is a device for transferring toner to paper and is composed of a developing unit, a transfer unit, a toner supply unit, etc., and transfers the toner on the photosensitive drum to paper. In the developing unit, negatively charged toner from a developing cylinder is attached to the electrostatic latent image on the photosensitive drum surface, creating a visible image. In the transfer unit, a positive potential is applied to the primary transfer roller to transfer the toner on the photosensitive drum surface to the transfer belt (primary transfer), and a positive potential is applied to the secondary transfer outer roller to transfer the toner on the transfer belt to paper (secondary transfer). The fixing unit 229 is a device for melting and fixing the toner on the paper to the paper using heat and pressure, and is composed of a heater, a fixing belt, a pressure belt, etc. The paper feed and transport unit 230 is a device for feeding paper, and the paper feed and transport operations are controlled by rollers and various sensors.

[0026] Next, the configuration of the inserter 108 of the image forming apparatus 101 will be described. The inserter 108 of the image forming apparatus 101 is composed of a communication I / F 232, a CPU 233, a memory 234, and a paper feed control unit 235, and each of these components is connected via a system bus 236. The communication I / F 232 is connected to the printing device 107 via a communication cable 254, and communication required for control is performed. The CPU 233 performs various controls required for paper feeding in accordance with a control program stored in the memory 234. The memory 234 is a storage device in which the control program is saved. The paper feed control unit 225 controls the rollers and sensors based on instructions from the CPU 218, and controls the feeding and transport of paper sheets transported from the inserter's paper feed unit and the printing device 107.

[0027] Next, the configuration of the inspection device 109 of the image forming apparatus 101 will be described. The inspection device 109 of the image forming apparatus 101 is composed of a communication I / F 237, a CPU 238, a memory 239, an image capturing unit 240, a display unit 241, an operation unit 242, and an HDD 255, and each component is connected via a system bus 243. The communication I / F 238 is connected to the printing device 107 via a communication cable 254, and communication necessary for control is performed. The CPU 238 performs various controls necessary for inspection according to a control program stored in the memory 239. The memory 239 is a storage device in which the control program is saved. The image capturing unit 240 captures an image of the conveyed paper based on instructions from the CPU 238. The CPU 238 saves the image captured by the image capturing unit 240 in the memory 239 as a reference image. Specifically, the average value of multiple scanned images is saved as the reference image. Furthermore, the CPU 238 compares the image captured by the photographing unit 240 with the correct image stored in the memory 239 to determine whether the printed image is normal. The display unit 241 displays the inspection results, setting screens, etc. The operation unit 242 is operated by the user and accepts instructions such as changing the settings of the inspection device 109 and registering the correct image. The HDD 255 stores various setting information and images required for inspection. The stored setting information and images can be reused.

[0028] Next, the configuration of the large-capacity stacker 110 of the image forming apparatus 101 will be described. The large-capacity stacker 110 of the image forming apparatus 101 is composed of a communication I / F 244, a CPU 245, a memory 246, and a paper discharge control unit 247, and each of these components is connected via a system bus 248. The communication I / F 244 is connected to the printing device 107 via a communication cable 254, and communication required for control is performed. The CPU 245 performs various controls required for paper discharge in accordance with a control program stored in the memory 246. The memory 239 is a storage device in which the control program is saved. The paper discharge control unit 247 controls the transport of transported paper to a stack tray, an escape tray, or the subsequent finisher 111 based on instructions from the CPU 245.

[0029] Next, the configuration of the finisher 111 of the image forming apparatus 101 will be described. The finisher 111 of the image forming apparatus 101 is composed of a communication I / F 249, a CPU 250, a memory 251, a paper discharge control unit 252, and a finishing processing unit 253, and each of these components is connected via a system bus 254. The communication I / F 249 is connected to the printing device 107 via a communication cable 254, and communication required for control is performed. The CPU 250 performs various controls required for finishing and paper discharge in accordance with a control program stored in the memory 251. The memory 251 is a storage device in which the control program is saved. The paper discharge control unit 252 controls paper transport and paper discharge based on instructions from the CPU 251. The finishing processing unit 253 controls finishing processes such as stapling, punching, and saddle stitching based on instructions from the CPU 251.

[0030] Next, we will explain the configuration of the external controller 102. The external controller 102 is composed of a CPU 208, memory 209, HDD 210, keyboard 211, display 212, LAN I / F 213, LAN I / F 214, and video I / F 215, which are connected via a system bus 216.

[0031] The CPU 208 comprehensively receives print data from the client PC 103 and performs RIP (Raster Image Processor) processing based on programs and data stored in the HDD 210. It also performs other processes such as sending print data to the image forming apparatus 101. It is also capable of performing RIP processing for correct image data. Specifically, in RIP processing for correct image data, an image is generated by converting a resolution of, for example, 600 dpi to 300 dpi, while in RIP processing for print data, an image is generated without reducing the resolution.

[0032] The memory 209 stores programs and data required for the CPU 208 to perform various processes and operates as a work area. The HDD 230 stores programs and data required for operations such as printing. The keyboard 211 is a device for inputting operation instructions for the external controller 102. The display 212 displays information such as the application executed by the external controller 102 using video signals of still images and moving images. The LAN I / F 213 is connected to the client PC 103 via the external LAN 104 and performs communication such as print instructions. The LAN I / F 214 is connected to the image forming apparatus 101 via the internal LAN 105 and performs communication such as print instructions. The external controller 102 can exchange various data with the printing apparatus 107, inserter 108, inspection device 109, large-capacity stacker 110, and finisher 111 via the internal LAN 105 and a communication cable 254.

[0033] The video I / F 215 is connected to the image forming apparatus 101 via a video cable 106, and performs communication of print data and the like.

[0034] Next, the configuration of the client PC 103 will be described. The client PC 103 is composed of a CPU 201, memory 202, HDD 203, keyboard 204, display 205, and LAN I / F 206, which are connected via a system bus 207. The CPU 201 creates print data and executes print instructions based on a document processing program stored in the HDD 203. The CPU 201 also comprehensively controls each device connected to the system bus. The memory 202 stores programs and data required for the CPU 201 to perform various processes and functions as a work area. The HDD 203 stores programs and data required for operations such as printing. The keyboard 204 is a device for inputting operation instructions for the PC 103. The display 205 displays information such as applications executed by the client PC 103 using video signals for still images and moving images. The LAN I / F 206 is connected to the external LAN 104, and is used for communication such as print instructions.

[0035] In the above description, the external controller 102 and the image forming apparatus 101 are connected via the internal LAN 1905 and the video cable 106. However, any other configuration is possible as long as the data necessary for printing can be transmitted and received; for example, a connection using only a video cable is also acceptable. Furthermore, the memory 202, memory 209, memory 223, memory 234, memory 239, memory 249, and memory 251 are each storage devices for storing data and programs. For example, they may be replaced with volatile RAM, non-volatile ROM, an internal HDD, an external HDD, a USB memory, or the like.

[0036] FIG. 3 is a cross-sectional view of the mechanism of the image forming apparatus 101. Reference numeral 107 denotes a printing device that forms an image to be printed on a sheet. Reference numerals 301 and 302 denote paper feed decks. Each paper feed deck can store various types of sheets. Each paper feed deck can separate only the topmost sheet from the stored sheets and transport it to sheet transport path 303. Reference numerals 304 to 307 denote developing stations that form toner images using Y, M, C, and K color toners, respectively, to form a color image. The toner image formed here undergoes primary transfer onto intermediate transfer belt 308, which rotates clockwise in the figure. At secondary transfer position 309, the toner image is transferred onto a sheet transported from sheet transport path 303. A display device 225 displays information on the printing status and settings of the image forming apparatus 101. Reference numeral 311 denotes a fixing unit that fixes the toner image to the sheet. Fixing unit 311 is equipped with a pressure roller and a heating roller, and as the sheet passes between these rollers, the toner is melted and pressed to fix the toner image to the sheet. After passing through fixing unit 311, the sheet is transported to 315 via sheet transport path 312. If further melting and pressing is required for fixing depending on the type of sheet, after passing through fixing unit 311, the sheet is transported to second fixing unit 313 using the upper sheet transport path, where additional melting and pressing is performed, and then transported to 315 via sheet transport path 314. If the image formation mode is double-sided, the sheet is transported to the sheet reversing path 316, and after being reversed at 316, the sheet is transported to double-sided transport path 317, where the image on the second side is transferred at secondary transfer position 309.

[0037] An inserter 108 is used to insert sheets. The inserter 108 has an inserter tray 321, and merges sheets fed through a sheet transport path 322 into the transport path. This makes it possible to insert a sheet at any position in a series of sheets transported from the printing device 107 and transport the sheet to a subsequent device.

[0038] The sheet that has passed through the inserter 108 is transported to the inspection device 109. Contact image sensors (CIS) 331 and 332 are arranged facing each other inside the inspection device 109. The CIS 331 is a sensor for reading the upper surface of the sheet, and the CIS 332 is a sensor for reading the lower surface of the sheet. Note that the image sensor for reading the image may be a line scan camera instead of a CIS. When the sheet transported to the sheet transport path 333 reaches a predetermined position, the inspection device 109 reads the image of the sheet using the CIS 331 and 332, and can determine whether the image of the device is normal. The display device 241 displays the inspection results performed by the inspection device 109, etc.

[0039] Reference numeral 110 denotes a large-capacity stacker capable of stacking a large number of sheets. The large-capacity stacker 110 has a stack tray 341 as a tray for stacking sheets. Sheets that have passed through the inspection device 109 are input into the large-capacity stacker 110 through a sheet transport path 344. The sheets are stacked on the stack tray 341 via the sheet transport path 344 and a sheet transport path 345. The stacker 340 also has an escape tray 346 as a paper discharge tray. The escape tray 346 is a paper discharge tray used to discharge sheets determined to be defective by the inspection device 109. When outputting to the escape tray 346, the sheet is transported from the sheet transport path 344 to the escape tray 346 via a sheet transport path 347. When transporting the sheet to a post-processing device downstream of the large-capacity stacker 110, the sheet is transported via a sheet transport path 348. Reference numeral 349 denotes an inverting unit for inverting the sheet. This reversing unit 349 is used when stacking sheets on the stack tray 341. When stacking on the stack tray 341, the sheets are reversed once in the reversing unit 349 so that the orientation of the input sheets is the same as the orientation of the sheets at the time of output. When conveying to the escape tray 346 or a subsequent post-processing device, the sheets are discharged as is without being flipped when stacked, so the reversing operation in the reversing unit 349 is not performed.

[0040] Reference numeral 111 denotes a finisher that performs finishing processing on conveyed sheets in accordance with a function specified by the user. Specifically, the finisher 111 has finishing functions such as stapling (one-point or two-point binding), punching (two-hole or three-hole), and saddle stitching. The finisher 111 has two paper output trays, 351 and 352, and outputs sheets to the output tray 351 via a sheet transport path 353. However, finishing processes such as stapling cannot be performed via the sheet transport path 353. When finishing processes such as stapling are performed, the sheets are output to the output tray 352 via the sheet transport path 354, and the finishing function specified by the user is executed in a processing section 355. The output trays 351 and 352 can each be raised and lowered, and it is also possible to lower the output tray 351 and stack sheets that have been finished in the processing section 355 on the output tray 351. When saddle stitching is specified, the saddle stitching processing unit 356 staples the sheet in the center, folds the sheet in half, and outputs it to a saddle stitching tray 358 via a sheet transport path 357. The saddle stitching tray 358 is configured as a belt conveyor, and the saddle stitched bundle loaded on the saddle stitching tray 358 is transported to the left side.

[0041] The inspection device 109 inspects the sent sheet image according to preset inspection items. The sheet image is inspected by comparing the sent sheet image with a preset correct image. Image comparison methods include comparing pixel values ​​for each image position, comparing object positions using edge detection, and extracting character data using OCR (Optical Character Recognition). Inspection items include misalignment of print position, image color, image density, streaks, blurred areas, and missing prints.

[0042] [Overall inspection process flow] Next, the overall flow from the work before the start of inspection to the execution of inspection in the inspection device 109 will be described using the flowchart in Fig. 4. Note that steps S401 to S412 in the flowchart are realized by the CPU 238 reading and executing a program stored in the HDD 255.

[0043] Each process in FIG. 4 is executed by the inspection device 109 in accordance with an operation from the client PC 103 of the user.

[0044] First, in step S401, the inspection device 109 registers a correct image that will be a correct image for inspection.

[0045] There are two methods for creating a correct image. The first method is to execute a print job and generate a correct image by scanning with the photographing unit 240.

[0046] The inspection device 109 waits in a read mode for the correct image, and executes a print job for registering the correct image from the client PC 103. When printing is executed, the inspection device 109 detects the conveyance of the paper and scans the paper with the photographing unit 240, and the scanned image is saved in the memory 239 of the inspection device 109 as the correct image.

[0047] The other method is to use image data after RIP processing, which analyzes the upper part of a print and generates image data, as the correct image, rather than using a scanned image. From step S402 onwards, we will explain a method of generating a correct image by executing a print job and scanning with the imaging unit 240. In the case of the method of using image data after RIP processing as the correct image, steps S402 and S403 are skipped.

[0048] In step S402, the inspection device 109 extracts the positions of the vertices of the paper from the image captured by the imaging unit 240. In this embodiment, the vertices of the paper refer to the four corners of the paper.

[0049] In step S403, the inspection device 109 transforms the image into the shape of the paper based on the positions of the paper vertices obtained in S402. This process may also include converting the resolution of the captured image to a specified resolution. Typically, the shape of the image corresponding to the paper in the captured image is distorted due to paper skew and fluctuations in transport speed. For example, if the paper size to be inspected is LTR and the resolution is 300 dpi in the main scanning direction and 300 dpi in the sub-scanning direction, the shape of the paper described above will be as follows: a rectangle with a length in the main scanning direction WR = 11 inches × 300 = 3300 pixels and a length in the sub-scanning direction HR = 8.5 inches × 300 = 2550 pixels. The shape of the paper can be represented by four points in coordinates: (0,0), (3299,0), (0,2549), and (3299,2549). The inspection device 109 transforms the image data so that the positions of the four vertices of the paper obtained from the image match the positions of the four vertices of the paper shape to be inspected in advance. This type of image transformation is also called geometric transformation, and there are known methods such as affine transformation. By performing the processes of S402 and S403, the scanned correct image can be converted to the size of the paper to be inspected.

[0050] In step S404, the inspection device 109 calculates feature points. Feature points indicate locations on the image that are suitable for aligning the entire image when comparing with the correct image in the inspection process described below. Feature points suitable for aligning the entire image are considered to be points with large corner feature values ​​within the image. A corner feature is a feature in which two distinct edges with different directions exist in a local vicinity. The corner feature value is a quantity that represents the strength of this edge feature. Furthermore, if feature points for aligning the entire image are concentrated in a certain location on the image, positional deviations will be large at locations far from the feature points. Therefore, it is desirable that the feature points be dispersed at positions that are somewhat distant from the feature points. Therefore, the inspection device 109 extracts feature points that exist in positions dispersed throughout the image from among the points with large corner feature values ​​described above. The extraction of feature points will be described later using FIG. 5.

[0051] In step S405, the inspection device 109 determines whether the number of feature points extracted in step S404 is equal to or greater than a predetermined number. In this embodiment, the predetermined number of feature points is the minimum number of feature points that can be used to align the target image and the scanned image. In this embodiment, the predetermined number of feature points is assumed to be three, but the number is not limited to three. If the number is less than the predetermined number, it is determined that an image with few feature points has been registered, and a warning screen is displayed and the user is prompted to select an inspection operation to be performed when there are few feature points. If it is determined that the number of feature points is equal to or greater than the predetermined number and a sufficient number of feature points have been extracted to align the images, the process proceeds to step S407. If it is determined that the number of feature points is less than the predetermined number, the process proceeds to step S406.

[0052] In step S406, the inspection device 109 stores the vertices of the paper in the memory 239 as alignment information.

[0053] In step S407, the inspection device 109 stores the feature points extracted in step S404 in the memory 239 as alignment information.

[0054] 7 on the display unit 241 of the inspection device 109, and notifies the user that the registered correct image is an image with few feature points. Note that the display on the display unit is controlled by the CPU 238 of the inspection device 109.

[0055] The UI 700 in FIG. 7 displays that the registered correct image is an image with few feature points, and is a UI for confirming whether to carry out the inspection as is or to return to registering the correct image without carrying out the inspection.

[0056] A button 701 is a button for executing the process again from step S401 in order to redo the registration of the correct image.

[0057] A button 702 is a button for executing an examination setting process to set up an examination.

[0058] A button 703 is a button for turning off the display of the UI 700.

[0059] The inspection device 109 continues to display the UI 700 until either the button 701, the button 702, or the close button 703 is selected in accordance with the user's operation.

[0060] In step S409, the inspection device 109 determines whether button 701 or button 702 is selected in accordance with the user's operation, and if 701 is selected, the process returns to step S401 and returns to reading the correct image.

[0061] If 702 is selected, the process proceeds to step S410 to set an inspection mode for an image with few feature points.

[0062] In step S410, the inspection device 109 displays, for example, a screen shown in FIG. 8 on the display unit 241 of the inspection device 109, and sets the operation for an image with few feature points.

[0063] A UI 800 in FIG. 8 is a UI screen for setting an inspection mode for an image with few feature points.

[0064] Button 801 is a button for performing an inspection in normal inspection mode for images with few feature points. In normal inspection mode, alignment is performed using the information on the paper vertices of the correct image and the scanned image, and the inspection is performed with the same inspection level settings as when there are a sufficient number of feature points.

[0065] Button 802 is a button for executing an inspection in the inspection level change mode for images with few feature points. In the inspection level change mode, the inspection level is automatically changed based on the inspection settings that have been set, and an inspection is executed. In the inspection level change mode, alignment is performed using information on the paper vertices of the correct image and the scanned image, and the inspection is executed at the specified inspection level that has been automatically changed.

[0066] A button 803 is a button for executing an inspection in an inspection exclusion mode for an image with few feature points. In the inspection exclusion mode, a registered inspection image is excluded from inspection.

[0067] In step S411, the inspection device 109 sets detailed information such as the inspection level, inspection type, and inspection area of ​​the print image inspection in accordance with the user's operation, as will be described in detail later.

[0068] In step S412, the inspection device 109 receives the print job for inspection from the client PC 103, detects the conveyance of the paper, scans the paper with the photographing unit 240, and stores the scanned image in the memory 239 of the inspection device 109. Then, an inspection is performed using the scanned image of the inspection job and the correct image registered in step S401, using the inspection parameters set in steps S410 and S411. Details will be described later.

[0069] [Detailed explanation of how minutiae information is calculated] The method for calculating feature point information will be described in detail with reference to FIG.

[0070] FIG. 5 is a diagram illustrating the extraction of feature points performed in S404.

[0071] 5(a) shows an image captured by the image capturing unit 240, and FIG. 5(b) shows an image after image deformation using the paper vertices. As explained in step S404, points with large corner features in the image are considered to be feature points suitable for aligning the entire image.

[0072] Various methods have been devised for detecting corner features, which represent the strength of edge features. One method for calculating corner features is a well-known technique called the Harris corner detection method. In the Harris corner detection method, a corner feature image is calculated from a differential image in the main scanning direction and a differential image in the sub-scanning direction. This corner feature image represents the edge value of the weaker of the two edges that make up the corner feature. Even though both edges of a corner feature are strong, the magnitude of the corner feature is expressed by whether the relatively weaker edge has a strong edge value. Figure 5(c) shows the result of applying the Harris corner detection method to Figure 5(b), where pixels with feature values ​​greater than a predetermined value are displayed in white. While multiple points with relatively large corner feature values ​​exist within an image, in this embodiment, six feature points with high corner feature value magnitudes and dispersed throughout the image are extracted as feature points for use in alignment. In Figure 5(c), the six extracted points are indicated by white dotted circles.

[0073] Figure 5(d) shows a 33-pixel square of the image corresponding to the position of one of the feature points extracted in Figure 5(c). In the inspection process flow described below, by searching for a location that matches the image shown in Figure 5(d) in the vicinity of the coordinates corresponding to the feature point in the scanned image to be inspected, it is possible to obtain the coordinates of the feature point in the scanned image to be inspected.

[0074] [Example of an image with few feature points] While Fig. 5 describes a case where there are a predetermined number of feature points or more and the extracted feature points are not biased in their positions, Fig. 6 will be used to describe an example where there are few feature points and the feature points are biased in their positions. For example, this may be the case where a correct image is registered using a blank sheet with no image printed on it, or a sheet printed with only a pattern with only points with small corner feature values. It may not be possible to extract a sufficient number of feature points for image alignment from the scanned image obtained by scanning such a sheet.

[0075] FIG. 6(b) shows an example of an image in which feature points are extracted in S404 from the reference image shown in FIG. 6(a). The image shown in FIG. 6(b) shows a state in which points with large feature amounts are concentrated in the corner areas of the sheet (indicated by the dotted circle in the figure). If the CPU 238 extracts one of these points with large feature amounts as a feature point in S404, the other points with large feature amounts are located very close to the reference image and are therefore not extracted as features. In this case, even if feature points are extracted from the reference image, it may be difficult to align the scanned image to be processed with the reference image based on the feature points.

[0076] [Advanced settings for setup method] Next, a flowchart for setting detailed information such as the inspection level, inspection type, and inspection area of ​​the print image inspection in step S411 will be described with reference to Fig. 9. Note that steps S901 to S902 of the flowchart are implemented by the CPU 239 reading and executing a program stored in the HDD 255.

[0077] By performing the processing of this flowchart, the inspection device 109 sets various inspection parameters such as the inspection area and inspection level for the print image inspection. An example of a UI related to the inspection settings will be described with reference to FIG.

[0078] In step S901, the inspection device 109 sets an area for print image inspection. The method for setting an area for print image inspection in this embodiment is as follows.

[0079] In this embodiment, four types of areas are set: a priority area, a standard area, a simple area, and an area not to be inspected (non-target area). A priority area is an area where inspection for defects is carried out with particular emphasis compared to other areas such as a person's face. A standard area is an area where inspection should be carried out in a standard manner. A simple area is an area where inspection may be carried out more simply than in a standard area. An area not to be inspected is an area that is excluded from inspection.

[0080] First, when setting a priority area, the user operates to press the priority area setting button 1021. Next, the user operates to specify an area in the page preview 1004 where the user wants to perform priority inspection, and the inspection device 109 sets the corresponding specified area as a priority inspection area 1005.

[0081] To set a standard area, the user operates to press the standard area setting button 1022. Next, the user operates to specify the range to be inspected as standard in the page preview 1004, and the inspection device 109 sets the specified range as the standard inspection area 1007.

[0082] To set a simple area, the user operates to press the simple area setting button 1023. Next, the user operates to specify an area to be inspected simply in the page preview 1004, and the inspection device 109 sets the corresponding specified area as a simple inspection area 1006.

[0083] To set an area not to be inspected, the user operates to press the button 1024 for setting a priority area. Next, the user operates to specify an area to be excluded from inspection in the page preview 1004, and the inspection device 109 sets the specified area as an area not to be inspected 1008.

[0084] In step S902, the inspection device 109 sets the detection items and their inspection levels for detecting defects in the print image inspection on the UI screen 1009.

[0085] The detection items for print image inspection are items related to the characteristics of defects to be detected when inspecting printed matter, such as round defects (dots) and linear defects (streaks). In this embodiment, a printed matter refers to a recording sheet on which an image is printed. The inspection level is a parameter set for each detected defect characteristic, which determines the size required for the defect to be determined as a defect. For example, there are seven levels, from level 1 to level 7, with level 7 being able to detect thinner and smaller defects than level 1. Furthermore, a level can be set for each inspection item, such as inspection level 7 for dots and level 4 for streaks. Note that the number of parameter levels and levels are not limited to these. The UI screen 1009 indicates that the user has selected level 7 for the inspection level setting for defects (dots) and level 7 for the inspection level setting for defects (streaks). Figure 14(a) shows an example of the inspection level coordinate information set in step S411. The upper left coordinate of the area specified in the page preview 1004 is stored as the start coordinate, and the lower right coordinate is stored as the end coordinate.

[0086] This concludes the description of the process related to detailed settings such as the inspection level, inspection type, and inspection area for print image inspection in step S411.

[0087] [Detailed explanation of inspection process] Next, a flowchart of the inspection process performed by the inspection device 109 in step S412 will be described with reference to Figures 11 and 12. Note that steps S1101 to S1110 in the flowchart are realized by the CPU 239 reading and executing a program stored in the HDD 255.

[0088] 11 is a flowchart showing the flow of the process performed by the inspection device 109 when performing the inspection process. The process in FIG.

[0089] In step S1101, the inspection device 109 acquires print settings and alignment information.

[0090] In step S1102, the inspection device 109 determines whether an inspection end instruction has been received. If an inspection end instruction has been received, the inspection process ends. If an inspection end instruction has not been received, the process proceeds to S1104.

[0091] In step S1103, the inspection device 109 determines whether paper has been transported to the inspection device 109. If paper has not been transported in S1103, the process proceeds to S1102. If paper has been transported in S1103, the process proceeds to S1105, where an image of the paper is read using CIS 231 and CIS 232 and stored in memory 239 of the inspection device 109.

[0092] In step S1105, the inspection device 109 compares the image read in S1104 with the correct image. The correct image used here is the image generated in Fig. 4. The flow of the process of comparison with the correct image will be described later with reference to Fig. 12.

[0093] Next, the process proceeds to step S1106, where the inspection device 109 determines whether the image is normal or defective based on the comparison with the correct image in step S1105.

[0094] If it is determined in S1106 that the image is normal (inspection OK), the process proceeds to S1107, and the display unit 241 of the inspection device 109 displays that the inspection result is OK.

[0095] Next, the process proceeds to step S1108, where the inspection device 109 instructs the printing device 107 to discharge the printed sheets onto the stack tray 341 of the large-capacity stacker 110. Based on the instruction from the inspection device 109, the printing device 107 instructs the large-capacity stacker 110 to discharge the sheets onto the stack tray 341.

[0096] Next, the process proceeds to S1102 and continues.

[0097] If it is determined in step S1106 that the image is defective (inspection NG), the process proceeds to S1109, where the display unit 241 of the inspection device 109 displays that the inspection result is NG.

[0098] Next, the process proceeds to S1110, where the inspection device 109 instructs the printing device 107 to discharge the printed sheet to the escape tray 346 of the large-capacity stacker 110. Based on the instruction from the inspection device 109, the printing device 107 instructs the large-capacity stacker 110 to discharge the sheet to the escape tray 346.

[0099] Next, the process proceeds to S1102 and continues. If an inspection end instruction is received here, or if an inspection end instruction is received before the next sheet is conveyed, the inspection process ends.

[0100] [Detailed explanation of the correct image and comparison process] 12 is a flowchart showing the flow of processing performed by the inspection device 109 when comparing with a correct image in the inspection process. Note that steps S1201 to S1207 in the flowchart are realized by the CPU 239 reading and executing a program stored in the HDD 255.

[0101] In step S1201, the inspection device 109 performs a process to update the inspection level and coordinate information, as will be described in detail later.

[0102] In step S1202, the inspection device 109 extracts the position of the vertex of the paper from the image captured by the image capturing unit 240.

[0103] In step S1203, the inspection device 109 determines whether the number of feature points of the correct image calculated in S404 is equal to or greater than a predetermined number. If it is determined that the number of feature points is equal to or greater than the predetermined number, the process proceeds to S1204.

[0104] If the number of feature points is less than the predetermined number, the process proceeds to S1206.

[0105] In step S1204, the inspection device 109 searches for a location in the image read in S1104 that matches the image of the feature point position of the correct image in the vicinity of the coordinates corresponding to the feature point from the paper vertex position, and acquires the feature point position of the image.

[0106] In step S1205, the inspection device 109 deforms and aligns the read image obtained in S1203 so that the positions of feature points in the read image match those in the authentic image. This process may also include converting the resolution of the captured image to a predetermined resolution. This type of image transformation is also called geometric transformation, and known methods exist for this, such as affine transformation. In affine transformation, the coefficients required for affine transformation processing can be calculated from the coordinates of the points to be matched between the reference image (the authentic image in this case) and the scanned image to be transformed (the read image in this case).

[0107] In step S1206, the inspection device 109 deforms and aligns the read image so that the positions of the paper vertices obtained in S1201 coincide with the positions of the paper vertices in the correct image. This may also include a process of converting the resolution of the captured image to a predetermined resolution. Note that the alignment in step S1206 may be performed using both a predetermined number of feature points and the positions of the paper vertices.

[0108] In step S1207, the inspection device 109 compares the image deformed in S1205 or S1206 with the correct image, and then ends this flow.

[0109] For example, if the difference between the pixel value (brightness value) of the pixel to be inspected in the image deformed in S1205 or S1206 and the pixel value (brightness value) of the pixel to be compared in the correct image is equal to or less than a threshold, the inspection device 109 determines that the pixel to be inspected passes. The threshold value differs for each inspection level. For example, the threshold value for inspection level 1 is 200. The threshold value for level 2 is 180. The threshold value for level 3 is 150. The threshold value for level 4 is 130. The threshold value for level 5 is 120. The threshold value for level 6 is 100. The threshold value for level 7 is 50.

[0110] Furthermore, when inspection of all pixels constituting the deformed image in S1205 or S1206 is completed, the inspection device 109 determines whether the total number of pixels determined to be unacceptable is equal to or less than the pass threshold. If the total number of pixels determined to be unacceptable is equal to or less than the pass threshold, the inspection device 109 determines that the image deformed in S1205 or S1206 is acceptable. If the total number of pixels determined to be unacceptable exceeds the pass threshold, the inspection device 109 determines that the image deformed in S1205 or S1206 is unacceptable.

[0111] In this embodiment, the determination in S1203 is made based on the number of feature points in the correct image, but the determination may also be made based on the number of feature points in the scanned image.

[0112] [Details of the process for updating inspection level and coordinate information] Next, a flowchart of the process of updating the inspection level and coordinate information performed by the inspection device 109 in step S1201 will be described with reference to Figures 13 and 14. Note that steps S1301 to S1305 in the flowchart are realized by the CPU 239 reading and executing a program stored in the HDD 255.

[0113] Fig. 13 is a flowchart showing the flow of processing performed by the inspection device 109 when performing processing to update the inspection level and coordinate information. Fig. 14 is a diagram for explaining processing to update the inspection level and coordinate information.

[0114] In step S1301, the inspection device 109 acquires the inspection level coordinate information set in step S411.

[0115] In step S1302, the inspection device 109 determines whether the number of feature points in the correct image is equal to or greater than a predetermined number in order to determine whether the inspection level and coordinate information need to be updated. Note that the processing in step S1302 is assumed to be performed by retaining the information acquired in S404. However, the determination may also be made based on information obtained by extracting feature points from the correct image again in S1302.

[0116] If the number of feature points is equal to or greater than the predetermined number, it is determined that there is no need to update the inspection level coordinate information, and the inspection level coordinate information is not updated, and the process of updating the inspection level and coordinate information is terminated.

[0117] If the number of feature points is less than the predetermined number, the inspection level coordinate information is updated to operate in the inspection mode for when there are few feature points, which was set in step S410. If the number of feature points is less than the predetermined number, the process proceeds to step S1303.

[0118] In step S1303, the inspection device 109 determines the selected inspection mode in order to operate in the inspection mode selected in step S410. If it is determined that the normal operation mode is selected, the inspection device 109 ends the process of updating the inspection level and coordinate information without updating the inspection level coordinate information.

[0119] If it is determined that the inspection level change mode has been selected, the process proceeds to step S1304, where the inspection level coordinate information is updated, whereas if it is determined that the inspection exclusion mode has been selected, the process proceeds to step S1305, where the inspection level coordinate information is updated.

[0120] In step S1304, the inspection device 109 changes the inspection level of all inspection areas (key area, standard area, simple area) in the inspection level coordinate information to "Level 1." By changing the inspection level to "Level 1," it becomes possible to suppress the occurrence of erroneous determinations even in images with few feature points and low alignment accuracy.

[0121] Fig. 14(a) is an example of the inspection level coordinate information before updating. In step S1304, the inspection levels of all inspection areas (focus area, standard area, simple area) are changed to "Level 1", so that the inspection levels of all inspection areas (focus area, standard area, simple area) are changed to "Level 1" as shown in Fig. 14(b).

[0122] In step S1305, the inspection device 109 changes the information of the non-inspection area in the inspection level coordinate information. By specifying the entire image as the non-inspection area, it is possible to suppress the occurrence of erroneous determination even when the alignment accuracy is low in an image with few feature points.

[0123] FIG. 14(a) is an example of inspection level coordinate information before updating. When the entire image is designated as a non-inspection area in step S1305, the information on the non-inspection area is updated as shown in FIG. 14(c). The entire image is designated as a non-inspection area. Here, Xmax is the horizontal length of the inspection image, which varies depending on the size of the paper. Also, Ymax is the vertical length of the inspection image, which varies depending on the size of the paper.

[0124] As described above, by switching the inspection mode for paper having an image with few feature points, it is possible to reduce erroneous determinations.

[0125] In this embodiment, the case where the number of feature points is less than a predetermined number has been described. However, even if the number of feature points is equal to or greater than a predetermined number, if the feature points are lined up in a row or concentrated in one location, it may be determined that sufficient feature points have not been extracted for image alignment.

[0126] Second Embodiment In the first embodiment, a method for switching the inspection mode in the case of an image with few feature points has been described. However, when the normal operation mode is selected, there is a problem that erroneous determination cannot be suppressed.

[0127] Therefore, in the second embodiment, a method for restricting the range of inspection levels that can be set in the detailed settings of the inspection method when an image with few feature points is registered as the correct image will be described. By restricting the selection of high inspection level settings, it becomes possible to suppress erroneous determination even when the registration accuracy is low.

[0128] In the following, only the differences from the first embodiment will be described in detail.

[0129] [Advanced settings for setup method] A flowchart for setting detailed information such as the inspection level, inspection type, and inspection area of ​​the print image inspection in step S411 in the second embodiment will be described with reference to Fig. 15. Note that steps S1501 to S1506 of the flowchart are implemented by the CPU 239 reading and executing a program stored in the HDD 255.

[0130] By performing the processing of this flowchart, the inspection device 109 sets various inspection parameters such as the inspection area and inspection level for the print image inspection. An example of a UI related to the inspection settings will be described with reference to FIG.

[0131] In step S1501, the inspection device 109 determines whether the number of feature points in the correct image is less than a predetermined number. If the number of feature points is less than the predetermined number, the process proceeds to step S1502 to limit the range of selectable inspection levels. If the number of feature points is not less than the predetermined number, the process proceeds to step S1505 to set the inspection area and inspection level without limiting the range of selectable inspection levels.

[0132] In step S1502, the inspection device 109 limits the range of selectable inspection levels. In this embodiment, a case will be described where seven levels, from level 1 to level 7, are selectable. The inspection device 109 limits the range of selectable inspection levels in the priority area to three levels, from level 1 to level 3. The inspection device 109 also limits the range of selectable inspection levels in the standard area to two levels, from level 1 to level 2. The inspection device 109 limits the range of selectable inspection levels in the simple area to only level 1.

[0133] In step S1503, the inspection device 109 sets the area for print image inspection. The method for setting the area for print image inspection in this embodiment is as follows: First, the user presses the button 1021 for setting a priority area. Next, the user specifies an area in the page preview 1004 that they want to inspect with priority, and the inspection device 109 sets the corresponding specified area as the priority inspection area 1005.

[0134] To set a standard area, the user operates to press the standard area setting button 1022. Next, the user operates to specify the range to be inspected as standard in the page preview 1004, and the inspection device 109 sets the specified range as the standard inspection area 1007.

[0135] To set a simple area, the user operates to press the simple area setting button 1023. Next, the user operates to specify an area to be inspected simply in the page preview 1004, and the inspection device 109 sets the corresponding specified area as a simple inspection area 1006.

[0136] To set an area not to be inspected, the user operates to press the button 1024 for setting a priority area. Next, the user operates to specify an area to be excluded from inspection in the page preview 1004, and the inspection device 109 sets the specified area as an area not to be inspected 1008.

[0137] In step S1504, the inspection device 109 sets the detection items and their inspection levels for detecting defects in the print image inspection on the UI screen 1609.

[0138] The UI screen 1609 shows that the user has selected level 3 for the defect (pochi) inspection level setting and level 3 for the defect (streak) inspection level setting.

[0139] This concludes the description of the process related to detailed settings such as the inspection level, inspection type, and inspection area for print image inspection in step S411.

[0140] As explained above, when an image with few feature points is registered as the correct image, by limiting the range of inspection levels that can be set in the detailed settings of the inspection method, it is possible to suppress erroneous judgments even when the alignment accuracy is low.

[0141] Third Embodiment In the first embodiment, a method for switching inspection modes for images with few feature points was described. However, when inspecting a large number of jobs with multiple pages (e.g., 1,000 pages), it is unrealistic to set up inspections individually for all pages. The job contains a mixture of pages with few feature points and pages with many feature points. In such cases, rather than having the user register inspection settings for each page, it is possible to register common inspection settings and inspection operations for when an image (page) with few feature points is registered, and then perform the inspection.

[0142] Therefore, in the third embodiment, a method for setting an inspection mode in advance when an image with few feature points is registered as a correct image in part of a job when inspecting a large number of multi-page jobs will be described. When inspecting a large number of multi-page jobs, the method of the first embodiment requires registration processing for all pages. The method of the third embodiment requires only one registration processing, and pages with many feature points can be inspected using common inspection settings, while pages with few feature points can be inspected using the inspection operation performed when an image with few feature points is registered. By registering the inspection mode in advance, it is possible to reduce the burden of individual setting work on the user.

[0143] In the following, only the differences from the first embodiment will be described in detail.

[0144] [Overall inspection process flow] The overall flow from the work before the start of inspection by the inspection device 109 to the execution of inspection in the third embodiment will be described using the flowchart in Fig. 17. Note that steps S1701 to S1711 in the flowchart are realized by the CPU 239 reading and executing a program stored in the HDD 255.

[0145] Each process in FIG. 17 is executed by the inspection device 109 in accordance with an operation from the client PC 103 of the user.

[0146] First, in step S1701, the inspection device 109 displays, for example, a screen shown in FIG. 8 on the display unit 241 of the inspection device 109, and sets the operation for an image with few feature points.

[0147] In step S1702, the inspection device 109 registers a correct image that will be used as a correct image for inspection.

[0148] In step S1703, the inspection device 109 extracts the positions of the vertices of the paper from the image captured by the imaging unit 240. In this embodiment, the vertices of the paper refer to the four corners of the paper.

[0149] In step S1704, the inspection device 109 transforms the image into the shape of the paper based on the positions of the vertices of the paper obtained in S1702.

[0150] In step S1705, the inspection device 109 calculates the feature points.

[0151] In step S1706, the inspection device 109 determines whether the number of feature points extracted in step S1704 is less than a predetermined number. If it determines that the number of feature points is equal to or greater than the predetermined number and that a sufficient number of feature points have been extracted for image alignment, the process proceeds to step S1708. If it determines that the number of feature points is less than the predetermined number, the process proceeds to step S1707.

[0152] In step S1707, the inspection device 109 stores the vertices of the paper in the memory 239 as alignment information.

[0153] In step S1708, the inspection device 109 stores the feature points extracted in step S1704 in the memory 239 as alignment information.

[0154] Each page of the print job is associated with the alignment information and stored in memory 239 .

[0155] In step S1709, the inspection device 109 determines whether reading of images that will be the correct images for all inspections in the print job has been completed. If the inspection device 109 determines that reading of all pages has been completed, it proceeds to step S1710 to perform detailed settings of the inspection method. If the inspection device 109 determines that reading of all pages has not been completed, it returns to step S1702 and performs image reading processing.

[0156] In step S1710, the inspection device 109 sets detailed information such as the inspection level, inspection type, and inspection area of ​​the print image inspection in accordance with the user's operation.

[0157] In step S1711, the inspection device 109 receives the print job for inspection from the client PC 103, detects the transport of the paper, scans the paper with the photographing unit 240, and saves the scanned image in the memory 239 of the inspection device 109. Then, an inspection is performed using the scanned image of the inspection job and the correct image registered in step S1702, using the inspection parameters set in steps S1701 and S1710.

[0158] As explained above, when inspecting a large number of multi-page jobs, a method for setting the inspection mode in advance has been explained for the case where an image with few feature points is registered as the correct image in part of the job. By registering the inspection mode in advance, it is possible to reduce the burden on the user of individual setting work.

[0159] (Other embodiments) While various examples and embodiments of the present invention have been shown and described, the spirit and scope of the present invention is not limited to the specific descriptions within this specification.

[0160] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions. [Explanation of symbols]

[0161] 107 Printing device 240 Photography Department 238 CPU 242 Operation section

Claims

1. a display control means for displaying a screen on an operation unit; a printing means for printing an image on a recording sheet; a generating means for reading a printed matter on which the image is printed by the printing means and generating a scanned image; extraction means for extracting feature points from the scanned image and the correct image; a registration means for registering the scanned image and the correct answer image using feature points extracted from the scanned image and feature points extracted from the correct answer image that has been registered in advance; an inspection means for inspecting the printed matter using the registered answer image and the scanned image; a processing means for performing processing according to a method selected from a plurality of methods including at least a first method and a second method when the number of feature points of the correct image is less than a predetermined number; Equipped with When the number of feature points of the genuine image extracted by the extraction means is less than the predetermined number, the display control means displays a screen that allows the user to select one of a plurality of modes, including the first method of performing the alignment using at least the positions of the paper vertices of the area showing the print of the scanned image and the positions of the paper vertices of the genuine image, as the selected method, and the second method of not performing inspection by the inspection means. An image forming apparatus characterized by:

2. The inspection means inspects whether a difference between the pixel value of the target pixel in the correct image and the pixel value of the target pixel in the scanned image is equal to or less than a threshold value.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

3. an area setting means for setting an inspection area in the image where the inspection means is to inspect and an out-of-target area where the inspection is not to be performed; When the second method is selected, the processing means sets the entire area showing the printed matter as a non-target area, thereby not inspecting the printed matter.

3. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

4. a determination unit that determines whether to use the positions of the feature points or the positions of the paper vertices in the alignment based on the number of the feature points extracted from the correct image by the extraction unit, The positioning means performs positioning of the scanned image with respect to the correct image using the positions of the feature points or the positions of the vertices of the paper in accordance with the determination by the determination means.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

5. The determination means If the number of the feature points is equal to or greater than a predetermined number, it is determined that the positions of the feature points are to be used in the alignment; If the number of feature points is less than a predetermined number, processing is performed using the selected method.

5. The image forming apparatus according to claim 4.

6. a detection means for detecting an area representing the printed matter from the scanned image; The feature points of the scanned image are feature points extracted by the extraction means from the area representing the printed matter detected by the detection means.

6. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

7. A registration means for registering a correct image is provided, The correct image to be registered in the registration means is a scanned image generated by the generation means.

7. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

8. A registration means for registering a correct image is provided, The correct image to be registered in the registration means is made up of image data that has undergone RIP processing.

7. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

9. The predetermined number is the number of feature points required for alignment of the scanned image and the target image.

9. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

10. 10. The image forming apparatus according to claim 1, wherein the display control means displays a warning screen when the number of feature points in the correct image is less than the predetermined number.

11. a printing step of printing the image on a recording sheet; a generating step of reading a printed matter on which the image is printed and generating a scanned image; an extraction step of extracting feature points from the scanned image and a ground truth image; a registration step of performing registration of feature points extracted from the scanned image with feature points extracted from the pre-registered correct image; an inspection step of inspecting the printed matter using the aligned correct image and the scanned image; a processing step of performing processing according to a method selected from a plurality of methods including at least a first method and a second method when the number of feature points of the correct image is less than a predetermined number; a display control step of displaying a screen on which the user can select one of a plurality of modes including the first method for performing the alignment using at least the positions of the paper vertices of an area showing a printout of the scanned image and the positions of the paper vertices of the target image as the selected method when the number of extracted feature points of the target image is less than the predetermined number, and the second method for not performing the inspection; 1. A method for controlling an image forming apparatus, comprising:

12. a printing means for printing an image on a recording sheet; a generating means for reading a printed matter on which the image is printed by the printing means and generating a scanned image; extraction means for extracting feature points from the scanned image and the correct image; a registration means for registering the scanned image and the correct answer image using feature points extracted from the scanned image and feature points extracted from the correct answer image that has been registered in advance; an inspection means for inspecting whether a difference between a pixel value of a target pixel in the original image after the alignment and a pixel value of a target pixel in the scanned image after the alignment is equal to or less than a threshold value; a control means for performing the alignment process using at least the positions of the paper vertices of the area representing the printout of the scanned image and the positions of the paper vertices of the correct image when the number of feature points of the correct image is less than a predetermined number, and setting the threshold value to a predetermined value; An image forming apparatus comprising:

13. The method further includes a determination unit that determines whether to use the positions of the feature points or the positions of the paper vertices for the alignment based on the number of the feature points extracted from the correct image by the extraction unit, The positioning means performs positioning of the scanned image with respect to the correct image using the positions of the feature points or the positions of the vertices of the paper in accordance with the determination by the determination means.

13. The image forming apparatus according to claim 12.

14. The determination means If the number of the feature points is equal to or greater than a predetermined number, it is determined that the positions of the feature points are to be used in the alignment; If the number of feature points is less than a predetermined number, the positioning is performed using at least the positions of the paper vertices in the area representing the print of the scanned image and the positions of the paper vertices in the correct image.

14. The image forming apparatus according to claim 13.

15. a detection means for detecting an area representing the printed matter from the scanned image; The feature points of the scanned image are feature points extracted by the extraction means from the area representing the printed matter detected by the detection means.

15. The image forming apparatus according to claim 12, wherein the image forming apparatus is a recording medium.

16. a printing step of printing the image on a recording sheet; a generating step of reading a printed matter on which the image is printed and generating a scanned image; an extraction step of extracting feature points from the scanned image and the target image; a registration step of aligning the scanned image with the correct image using feature points extracted from the scanned image and feature points extracted from the correct image that has been registered in advance; an inspection step of inspecting whether a difference between a pixel value of a target pixel in the registered answer image and a pixel value of a target pixel in the registered scanned image is equal to or less than a threshold; a control step of performing the alignment using at least the positions of the paper vertices of the area representing the printout of the scanned image and the positions of the paper vertices of the correct image when the number of feature points of the correct image is less than a predetermined number, and setting the threshold to a predetermined value; 1. A method for controlling an image forming apparatus, comprising:

Images