Inspection device, image forming apparatus, inspection method, and program

Abstract

To provide a technique for detecting distortion of each part of a print sheet.SOLUTION: An inspection apparatus according to an aspect of the present disclosure includes a reading unit configured to read a sheet on which an image is formed, the sheet being conveyed from an image forming unit, a first alignment unit configured to compare an entire image of the sheet read by the reading unit with an entire reference image to detect a deviation of a formation position in the image of the sheet, and align the image of the sheet with the reference image based on the deviation to acquire a first image, a second alignment unit configured to compare the first image with the reference image to detect distortion for each part of the image of the sheet, and locally align the first image with the reference image based on the distortion to acquire a second image, and a determination unit configured to acquire an amount of distortion from the distortion for each part to determine whether the image of the sheet is normal.SELECTED DRAWING: Figure 11

Description

[Technical Field]

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

[0002] In recent years, printing systems have become known that can inspect printed sheets printed by a printing device using an inspection device while they are being transported. During inspection, the inspection device reads an image of the transported printed sheet and analyzes the read image to determine whether the printed sheet is normal. The inspection device can detect, for example, misalignment between the printed image and the paper (overall misalignment) and printing abnormalities. If a printed sheet is determined to be abnormal, the abnormal sheet is discharged to a different destination from normal sheets. This prevents abnormal sheets from being mixed in with normal sheets and allows the operator to discard the abnormal sheets.

[0003] In printing devices, deviations of several mm can occur in the printing position depending on the conveying speed of the device, the paper storage environment, and the printed image. Patent Document 1 proposes a printed image inspection device that reads the printed sheet with a scanner in an inspection device, detects edges, and compares the detected edges with the edges of a reference image to detect deviations. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-165011 Summary of the Invention [Problem to be solved by the invention]

[0005] Among the types of misalignment, misalignment due to printed images occurs when toner on the paper makes the sheet slippery, reducing the paper transport force and causing the printed image to shrink. If misalignment or distortion affects the overall size of the image, it is possible to adjust the trimming position by adjusting the overall position misalignment so that the four corners of the image are aligned, such as by adjusting the registration. However, because the misalignment due to printed images varies depending on the amount of toner applied, the misalignment varies in each part of the image, causing local misalignment. Therefore, the inspection device proposed above could not handle cases where the misalignment varies in each part of the printed sheet.

[0006] In view of the above problems, an object of the present invention is to provide a technique for detecting distortion in each portion of a print sheet. [Means for solving the problem]

[0007] The inspection device of the present invention comprises a reading means for reading a sheet on which an image is formed and which is transported from an image forming means; a first alignment means for comparing the entire image of the sheet read by the reading means with the entire reference image to detect any misalignment in the formation position of the image of the sheet, and aligning the image of the sheet with the reference image based on the misalignment to obtain a first image; a second alignment means for comparing the first image with the reference image, detecting distortion for each portion of the image of the sheet, and locally aligning the first image with the reference image based on the distortion to obtain a second image; and a determination means for obtaining the amount of distortion from the distortion for each portion and determining whether the image of the sheet is normal. [Effects of the Invention]

[0008] According to the present invention, it is possible to inspect the distortion occurring in the printed matter and determine that the sheet is abnormal. [Brief explanation of the drawings]

[0009] [Figure 1] Overall view of the printing system. [Figure 2]FIG. 1 is a block diagram illustrating a system configuration of a printing system. [Figure 3] FIG. [Figure 4] Overall inspection process flow. [Figure 5] Inspection execution flow. [Figure 6] Alignment flow. [Figure 7] Overall alignment flow. [Figure 8] Partial alignment flow. [Figure 9] Flow for obtaining the amount of positional deviation. [Figure 10] Flow for obtaining the total positional deviation amount. [Figure 11] Flow to obtain the amount of distortion. [Figure 12] An example of the inspection settings UI. [Figure 13] An example of search results. [Figure 14] 1A and 1B are diagrams illustrating the occurrence of local distortion. [Figure 15] FIG. 10 is a diagram illustrating free-form registration. [Figure 16] FIG. 10 is a diagram illustrating calibration. [Figure 17] A flow for removing scan distortion using a calibration chart. [Figure 18] This is a flow chart for obtaining print distortion after removing scan distortion using a calibration chart. [Figure 19] An example of presenting measures to prevent and mitigate recurrence of abnormal sheets. [Figure 20] An example of presenting measures to prevent and mitigate recurrence of abnormal sheets. [Figure 21] Flow for setting preset basic values ​​from paper information. [Figure 22] 10 is a table showing basic values ​​of distortion thresholds corresponding to paper information. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[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 The hardware configuration of a printing system according to this embodiment will be described with reference to Fig. 1. The printing 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. 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 client PC 103 to the external controller 102. Note that the image forming apparatus 101 and the external controller 102 may be connected via only either the internal LAN 105 or the video cable 106, as long as the external controller 102 can control the operation of the image forming apparatus 101.

[0013] A printer driver that has a 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 performs printing can issue a print instruction from various applications via the printer driver. The printer driver transmits print data to the external controller 102 based on the print instruction from the user. Upon receiving a print instruction from the client PC 103, the external controller 102 performs data analysis and rasterization processing, and inputs the print data to the image forming apparatus 101 to issue a print instruction.

[0014] Next, we will explain the image forming apparatus 101. The image forming apparatus 101 is configured by connecting multiple devices with different functions. For example, the image forming apparatus 101 is configured to include a printing device 107, an inserter 108, an inspection device 109, a large-capacity stacker 110, and a finisher 111.

[0015] Printing device 107 forms an image using toner on unprinted media (paper, hereinafter referred to as "sheet") transported from a paper feeder located below printing device 107. Here, a sheet is a recording medium on which an image is formed, and includes various media such as plain paper, cardboard, and OHP sheets. The paper on which an image is printed in this way is hereinafter referred to as a printing sheet.

[0016] The inserter 108 inserts an insertion sheet into a printed product printed by the printing device 107. The insertion sheet can be inserted at any position in the group of printed sheets printed by the printing device 107 and transported. The inspection device 109 reads the image on the conveyed print sheet and compares it with a pre-registered reference image that is the correct answer, thereby determining whether the printed image is normal.

[0017] The large-capacity stacker 110 can accommodate a large number of sheets. The finisher 111 performs finishing processes on the transported sheets. The finisher 111 can perform finishing processes such as stapling, punching, and saddle stitching, and discharges the sheets that have undergone finishing processes onto a paper discharge tray.

[0018] 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, or print data may be read from an HDD 221 (described later) inside the printing apparatus 107. In this case, data analysis and rasterization processing are performed in the image forming apparatus 101, and printing processing is executed.

[0019] The internal configurations of the image forming apparatus 101, the external controller 102, and the client PC 103 will be described with reference to FIG. 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 configured to include a communication I / F (interface) 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 reading unit 226, a latent image unit 227, an image creating unit 228, a fixing unit 229, and a paper feeding and conveying unit 230. Each of the components is connected via a system bus 231.

[0020] 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 256, and performs communication to control each device. The LAN I / F 218 is connected to the external controller 102 via the internal LAN 105 and communicates print data and the like. The video I / F 220 is connected to the external controller 102 via the video cable 106 and communicates image data and the like.

[0021] 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 the like stored in the HDD 221. The memory 223 stores programs and image data required for the CPU 222 to perform various processes, and operates as a work area. The operation unit 224 accepts various setting inputs and operation instructions from the user. The display 225 displays setting information for the image processing device, the processing status of print jobs, and the like. The document reading unit 226 performs processing to read a document when using the copy function or scan function. The document reading unit 226 reads document data by shining an exposure lamp on a sheet placed by the user and capturing an image with a CMOS image sensor.

[0022] The latent image unit 227 performs primary charging and laser exposure to irradiate the photosensitive drum with laser light to develop a toner image. In the latent image unit 227, primary charging is first performed to charge the surface of the photosensitive drum to a uniform negative potential. Next, a laser driver irradiates the photosensitive drum with laser light while adjusting the reflection angle with a polygon mirror, forming an electrostatic latent image. The image creation unit 228 is a device for transferring toner to a sheet, and is composed of a development unit, transfer unit, toner supply unit, etc., and transfers the toner on the photosensitive drum to the sheet.

[0023] 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 primary transfer is performed by applying a positive potential to the primary transfer roller to transfer the toner on the photosensitive drum surface to the transfer belt, and a secondary transfer is performed by applying a positive potential to the secondary transfer outer roller to transfer the toner on the transfer belt to a sheet. The fixing unit 229 is a device that melts and fixes the toner on the sheet to the sheet using heat and pressure, and is composed of a heater, fixing belt, pressure belt, etc. The paper feed and transport unit 230 is a device that feeds sheets, and controls the sheet feed and transport operations using rollers and various sensors.

[0024] 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 configured to include a communication I / F 232, a CPU 233, a memory 234, and a paper feed control unit 235. These components are connected via a system bus 236. The communication I / F 232 is connected to the printing device 107 via a communication cable 256 and performs communication required for control. 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 235 controls rollers and sensors based on instructions from the CPU 233, and controls the feeding and transport of sheets transported from the inserter's paper feed unit and the printing device 107.

[0025] 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 configured to include a communication I / F 237, a CPU 238, a memory 239, an imaging unit 240, a display unit 241, an operation unit 242, and an HDD 255. Each component is connected via a system bus 243. The communication I / F 237 is connected to the printing device 107 via a communication cable 256, and performs communication required for control. The CPU 238 performs various controls required for inspection in accordance with a control program stored in the memory 239. The memory 239 is a storage device in which the control program is saved.

[0026] The photographing unit 240 photographs the conveyed sheet based on instructions from the CPU 238. The CPU 238 stores the image photographed by the photographing unit 240 in the memory 239 as a reference image that will serve as the correct answer. Furthermore, the CPU 238 compares the image photographed by the photographing unit 240 with the reference 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 a reference image. The HDD 255 stores various setting information and images required for inspection. The stored various setting information and images can be reused.

[0027] 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 configured to include a communication I / F 244, a CPU 245, a memory 246, and a paper discharge control unit 247. Each component is connected via a system bus 248. The communication I / F 244 is connected to the printing device 107 via a communication cable 256 and performs communication required for control. The CPU 245 performs various controls required for paper discharge in accordance with a control program stored in the memory 246. The memory 246 is a storage device in which the control program is saved. The paper discharge control unit 247 controls the transport of the transported sheet to a stack tray, an escape tray, or the subsequent finisher 111 based on instructions from the CPU 245.

[0028] 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 includes a communication I / F 249, a CPU 250, a memory 251, a paper discharge control unit 252, and a finishing processing unit 253. These components are connected via a system bus 254. The communication I / F 249 is connected to the printing device 107 via a communication cable 256 and performs communication required for control. 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 sheet transport and paper discharge based on instructions from the CPU 250. The finishing processing unit 253 controls finishing processes such as stapling, punching, and saddle stitching based on instructions from the CPU 250.

[0029] Next, we will explain the configuration of the external controller 102. The external controller 102 is configured to include a CPU 208, memory 209, HDD 210, keyboard 211, display 212, LAN I / F 213, LAN I / F 214, and video I / F 215. Each of the components is connected via a system bus 216.

[0030] The CPU 208 comprehensively executes processes such as receiving print data from the client PC 103 and transmitting the print data to the image forming apparatus 101 based on programs and data stored in the HDD 210. The CPU 208 is also capable of performing RIP (Raster Image Processor) processing for reference image data, which is the correct answer. Specifically, in the RIP processing for the reference image data, an image is generated by converting a resolution of, for example, 600 dpi to 300 dpi, and in the RIP processing for the print data, an image is generated without reducing the resolution.

[0031] The memory 209 stores programs and data required for the CPU 208 to perform various processes and operates as a work area. The HDD 210 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, the inserter 108, the inspection apparatus 109, the large-capacity stacker 110, and the finisher 111 via the internal LAN 105 and a communication cable 256. The video I / F 215 is connected to the image forming apparatus 101 via the video cable 106 and communicates print data and the like.

[0032] Next, the configuration of the client PC 103 will be described. The client PC 103 includes a CPU 201, a memory 202, a HDD 203, a keyboard 204, a display 205, and a LAN I / F 206. These components are connected via a system bus 207. The CPU 201 creates print data and executes print instructions based on a document processing program or the like stored in the HDD 203. The CPU 201 also comprehensively controls each device connected to the system bus 207. The memory 202 stores programs and data required for the CPU 201 to perform various processes. The memory 202 also operates as a work area for the CPU 201. The HDD 203 stores programs and data required for operations such as print processing. The keyboard 204 is a device for inputting operation instructions for the client 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 performs communication such as receiving print instructions and RIP images. In this example, the amount of applied toner during printing is calculated by the CPU 238 of the inspection device 109, but it may also be received from the printing device 107 or the external controller 102 via a communication cable 256.

[0033] In the above description, the external controller 102 and the image forming apparatus 101 are connected via the internal LAN 105 and the video cable 106, but any configuration is acceptable as long as they are capable of transmitting and receiving the data necessary for printing, and for example, a connection configuration using only the video cable 106 is also acceptable. Furthermore, the memory 202, the memory 209, the memory 223, the memory 234, the memory 239, the memory 246, and the memory 251 are each sufficient as long as they are storage devices for holding 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.

[0034] With reference to FIG. 3, the printing process and paper transport by the image forming apparatus 101 will be described. The printing device 107 forms an image to be printed on paper. Paper feed deck 301 and paper feed deck 302 can store various types of paper. Each paper feed deck can separate only the topmost sheet of stored paper and transport it to paper transport path 303. To form a color image, development stations 304 to 307 form toner images using color toners of Y (yellow), M (magenta), C (cyan), and K (black), respectively. The toner images formed here are primarily transferred to intermediate transfer belt 308. Intermediate transfer belt 308 rotates clockwise in FIG. 3. Then, at secondary transfer position 309, the toner image primarily transferred to intermediate transfer belt 308 is transferred to paper transported from paper transport path 303. At this time, if the amount of toner applied is large, the toner is more likely to slip, which can reduce the paper transport speed. As a result, the toner image may shrink in the direction of paper transport, resulting in a shrunken image as shown in the right diagram of FIG.

[0035] The display 225 displays information for the printing status and settings of the image forming apparatus 101. The fixing unit 311 fixes the toner image to the paper. The fixing unit 311 includes a pressure roller and a heating roller. The paper passes between these rollers, melting and pressing the toner, thereby fixing the toner image to the paper. After passing through the fixing unit 311, the paper is transported to the paper transport path 315 via the paper transport path 312. Depending on the type of paper, further melting and pressing may be required for fixing. In this case, after passing through the fixing unit 311, the paper is transported to the second fixing unit 313 via the upper paper transport path 314. After additional melting and pressing in the second fixing unit 313, the paper is transported to the paper transport path 314 via the paper transport path 315. When the image formation mode is double-sided, the paper is transported to the paper inversion path 316. After being inverted by the paper inversion path 316, the paper is transported to the double-sided transport path 317. At the secondary transfer position 309, the image is transferred onto the second side of the paper.

[0036] The inserter 108 inserts insertion sheets. The inserter 108 has an inserter tray 321, and merges sheets fed via a paper transport path 322 into the transport path. This makes it possible to insert insertion sheets at any position in a series of sheets transported from the printing device 107 and transport them to a subsequent device.

[0037] The print sheet that has passed through the inserter 108 is transported to the inspection device 109. A photographing unit 240 is arranged opposite the paper transport path 333 of the inspection device 109. The photographing units 240 are sensors for reading the top and bottom surfaces of the print sheet, respectively. When the print sheet transported on the transport path 333 reaches a predetermined position, the inspection device 109 reads the image of the print sheet using the photographing unit 240. Then, by performing an inspection, it can be determined whether the image of the printing device 107 is normal. The photographing unit 240 is one form of the reading means for reading the print sheet in the present invention.

[0038] Specifically, the inspection device 109 inspects the transmitted print sheet image according to preset inspection items. The inspection of the print sheet image is performed by comparing the transmitted print sheet image with a preset reference image that is the correct answer. Image comparison methods include comparing pixel values ​​at 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 print, and missing print. The display unit 241 displays the inspection results performed by the inspection device 109. After inspection by the inspection device 109, the print sheet is transported to the large-capacity stacker 110.

[0039] The large-capacity stacker 110 is a stacker that can stack a large amount of printed sheets. The large-capacity stacker 110 has a stack tray 341 as a tray for stacking printed sheets. Printed sheets that have passed through the inspection device 109 are transported to the large-capacity stacker 110 via a printed sheet transport path 344. The printed sheets then travel from the printed sheet transport path 344 to a printed sheet transport path 345 and are stacked on the stack tray 341.

[0040] Furthermore, the large-capacity stacker 110 has an escape tray 346 as a paper output tray. The escape tray 346 is a paper output tray used to output print sheets that have been determined to be abnormal by the inspection device 109. When outputting print sheets to the escape tray 346, the print sheets are transported from print sheet transport path 344 to the escape tray 346 via print sheet transport path 347. When transporting print sheets to the finisher 111 downstream of the large-capacity stacker 110, the print sheets are transported via print sheet transport path 348.

[0041] The discharge reversing unit 342 is used to reverse the print sheets. This discharge reversing unit 342 is used when the print sheets are stacked on the stack tray 341. When stacking on the stack tray 341, the print sheets are reversed once by the discharge reversing unit 342 so that the orientation of the input print sheets and the orientation of the print sheets at the time of output are the same. When transporting to the escape tray 346 or the subsequent finisher 111, the print sheets are discharged as is without being flipped when stacked, so the discharge reversing unit 342 does not perform the reversing operation.

[0042] The finisher 111 performs finishing processing on the transported print sheets according to the 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 is equipped with a paper output tray 351 and a paper output tray 352. The print sheets are output to the paper output tray 351 or the paper output tray 352 via a print sheet transport path 353 or a print sheet transport path 354. However, finishing processing such as stapling cannot be performed on the print sheet transport path 353. When finishing processing such as stapling is to be performed, the print sheets are output to the paper output tray 352 via the print sheet transport path 354, and the finishing function specified by the user is executed in a processing unit 355, and the print sheets are output to the paper output tray 352. The paper output tray 351 and the paper output tray 352 can each be raised and lowered, and it is also possible to lower the paper output tray 351 so that printed sheets that have been finished in the processing unit 355 are stacked on the paper output tray 351. When saddle stitch binding is specified, the saddle stitch processing unit 356 staples the printed sheets in the center, folds the printed sheets in half, and outputs them to the saddle stitch binding tray 358 via the printed sheet transport path 357. The saddle stitch binding tray 358 is configured as a belt conveyor, and the saddle stitched bundle stacked on the saddle stitch binding tray 358 is transported to the left.

[0043] <Overall inspection process flow> Next, with reference to FIG. 4, the overall flow from the work before the start of the inspection in the inspection device 109 to the execution of the inspection will be described. Each process in the flowchart of Fig. 4 is executed by the inspection device 109 in accordance with a user's operation via the operation unit 242 shown in Fig. 2. The process described below is realized, for example, by the CPU 238 of the inspection device 109 reading a program stored in the HDD 255 into the memory 239 and executing it. Below, the step numbers of each process included in the flowchart are indicated by numbers beginning with "S." This also applies to the subsequent flowcharts.

[0044] First, in S401, the CPU 238 registers a reference image that will be the correct answer for the inspection. The reference image can be a simulated image (hereinafter referred to as a simulated reference image) using print data previously received via the communication I / F 237, or scan data previously captured by the inspection device 109. The simulated reference image is an image created by adding color conversion, noise reproduction, glare reproduction processing, and margin addition to the print data, and is an image simulated by predicting the scan data from the print data. In addition, feature points are obtained from the reference image and saved in the HDD 255 along with the reference image.

[0045] In S402, the CPU 238 sets detailed inspection area settings such as the inspection level, inspection type, and inspection area of ​​the print image inspection in accordance with user operations. These settings are set using the inspection UI in Fig. 12. The various setting contents in Fig. 12 will be described later. Next, in S403, an inspection is performed. The inspection process in S403 will be described in detail with reference to the flowcharts in FIG.

[0046] <Inspection> Next, the inspection flow will be described. When the inspection starts, in S403, the CPU 238 inspects the printed sheet based on the reference image registered in S401 and the inspection settings set in S402. The flow for scanning an image and performing an inspection will be described with reference to Fig. 5. The processing described below is realized, for example, by the CPU 238 of the inspection device 109 reading a program stored in the HDD 255 into the memory 239 and executing it.

[0047] In S501, the CPU 238 acquires the inspection settings, the reference image, and information on feature points. In S502, the CPU 238 transitions to a scan standby state. In the scan standby state, two types of external inputs are accepted: scanning an inspection image and an instruction to end the inspection. In S503, if an instruction to end the inspection is received, the inspection process ends, whereas if an input to scan the inspection image is received, the process proceeds to S504.

[0048] In S504, the CPU 238 stores the inspection image read using the photographing unit 240 in the memory 239 of the inspection device 109. When the CPU 238 is in a scan standby state, the photographing unit 240 is always on standby so that it can scan a print sheet. When the printing device 107 prints on paper and the print sheet passes the photographing unit 240, the photographing unit 240 scans the print sheet to obtain an inspection image. The scanned inspection image is sent to the CPU 238. Then, the process proceeds to S505.

[0049] In S505, the CPU 238 performs alignment between the reference image and the inspection image stored in the memory 239. In the alignment, first, rigid body alignment of the inspection image is performed by affine transformation using feature points of the reference image and the inspection image. This alignment is performed to align the misalignment that occurs in the image formation position when the image is formed on the sheet with the reference image.

[0050] Thereafter, misalignment due to distortion of the print sheet is removed by non-rigid alignment. As an example, free form deformations (FFD) is used to align the misalignment due to distortion. Details of the alignment will be described later with reference to FIG. 6 and subsequent figures. Here, in this embodiment, "distortion" is defined as local non-linear misalignment that has not been aligned within an image obtained by rigid alignment of the inspection image (an image obtained by global alignment of the formation position).

[0051] Next, in S506, the CPU 238 acquires the "overall positional deviation amount," which quantitatively represents the deviation width when rigid body alignment was performed in S505, and the "distortion amount," which quantitatively defines the distortion. The "overall positional deviation amount" indicates the distance between the four corners of the paper between the reference image and the test image, and the "distortion amount" indicates the distance between corresponding pixels between the reference image and the test image. The distortion amount will be described later with reference to FIG. 9 and subsequent figures.

[0052] In S507, the CPU 238 determines whether the amount of overall positional misalignment is less than a specified value, and if so, determines that the inspection result is normal. If the CPU 238 determines that the inspection image is normal in S507, the process proceeds to S508. If the amount of overall positional misalignment of the inspection image is equal to or greater than a specified value, the CPU 238 determines that the inspection result is abnormal, and the process proceeds to S512. In S512, the CPU 238 instructs the large-capacity stacker 110 to eject printed sheets determined to be abnormal as abnormal sheets onto the escape tray 346. Note that the specified value for the amount of overall positional misalignment is set when the inspection is configured, and this will be described later.

[0053] In S508, the CPU 238 determines whether the amount of distortion in the inspection image is less than a specified value, and if so, determines that the inspection result is normal. If the CPU 238 determines that the inspection image is normal in S508, the process proceeds to S509. If the amount of distortion in the inspection image is equal to or greater than the specified value, the inspection result is determined to be abnormal, and the process proceeds to S512. In S512, the CPU 238 instructs the large-capacity stacker 110 to eject printed sheets determined to be abnormal as abnormal sheets onto the escape tray 346. Note that the specified value for the amount of distortion is set when the inspection is configured, and this will be described later.

[0054] Next, in S509, the CPU 238 performs an image anomaly inspection to detect image anomalies within the pattern. The image anomaly inspection performed here detects image anomalies such as dents and streaks, which will be described later in FIG. 12. The image difference between the reference image and the inspection image is obtained, and image anomalies are extracted based on the image difference. Anomaly extraction involves fine correction by comparing with neighboring pixels using window matching, correction of density fluctuations for the image difference, and correction by weighting the difference around the edges by edge strength, and then emphasis processing according to the shape of the anomaly. The corrected difference image generated in this way is subjected to binarization processing using a threshold, and anything above the threshold is deemed to be an anomaly.

[0055] In S510, the CPU 238 determines whether the inspection result of the inspection image is normal based on the presence or absence of the abnormality detected in S509. If it is determined to be normal in S510 (Yes), proceed to S511. In S511, the inspection device 109 instructs the large-capacity stacker 110 to discharge the print sheet determined to be a normal image onto the stack tray 341. On the other hand, if it is determined in S510 that there is an abnormality of a specified level or higher (No), the print sheet is determined to be an abnormal sheet, and proceed to S512. In S512, the inspection device 109 instructs the large-capacity stacker 110 to discharge the print sheet as an abnormal sheet onto the escape tray 346.

[0056] As described above, after performing alignment, the inspection device 109 can check the overall positional misalignment amount and distortion amount, determine whether there are any image abnormalities, and allocate the paper discharge destination. Next, the execution flow of alignment will be described with reference to Fig. 6. The processing described below is realized, for example, by the CPU 238 of the inspection device 109 reading a program stored in the HDD 255 into the memory 239 and executing it.

[0057] <Alignment> The alignment in S505 is roughly divided into two steps. First, in S601, CPU 238 performs global alignment (first alignment), which is a linear alignment between the scanned inspection image and the reference image. The flow of global alignment will be described later with reference to FIG. 7 and subsequent figures. Between the inspection image aligned by global alignment in S601 and the reference image, distortion remains, which is a local nonlinear positional deviation that cannot be aligned by global alignment. Therefore, in S602, CPU 238 performs partial alignment (second alignment) to align the position of the locally occurring distortion. The flow of partial alignment will be described later with reference to FIG. 8 and subsequent figures.

[0058] From here, the overall alignment in S601 in Fig. 6 will be described with reference to Fig. 7. The processing described below is realized, for example, by the CPU 238 of the inspection device 109 reading out a program stored in the HDD 255 into the memory 239 and executing it.

[0059] In S701, the CPU 238 counts the number of feature points acquired in S501. If the number of feature points is less than a specified value (No), it is determined that alignment using those feature points is likely to fail, and the process proceeds to S705. On the other hand, if the number of feature points is equal to or greater than the specified value in S701, the process proceeds to S702, where alignment using the feature points is performed. For example, the specified number of feature points here is three, which is the minimum number for generating a single affine matrix. The specified number of feature points may be increased to improve accuracy, and the specified number is not limited to the above.

[0060] Next, in S702, the CPU 238 extracts feature points from the inspection image. In this feature point extraction, a grayscale image is generated, and feature points that are equal to or greater than a threshold are selected from among the feature points extracted using the Harris corner detection method. In this embodiment, the Harris corner detection method is used, but the method of feature point extraction is not limited to this.

[0061] Next, in S703, the CPU 238 matches the feature points of the inspection image extracted in S702 with the feature points of a reference image acquired in advance, and selects feature points to be used for aligning the inspection image with the reference image. In S704, the CPU 238 obtains an affine matrix for performing alignment so that the feature points of the reference image correspond to the feature points of the inspection image obtained in S703. If the number of feature points is insufficient in S701 and the process proceeds to S705, the CPU 238 performs overall registration using the four corners of the print sheet of the inspection image. In S705, the CPU 238 acquires the coordinates of the four corners of the print sheet of the inspection image.

[0062] Next, in S706, the CPU 238 acquires an affine matrix to move the four corners of the print sheet of the inspection image to the respective predetermined coordinates. In this case, the predetermined coordinates indicate the positions of the four corners of the print sheet of the reference image. In this embodiment, a simulated reference image is used as the reference image, and the coordinates of the four corners of the print sheet of the reference image are determined at the stage of creating the simulated reference image. Therefore, the predetermined coordinates are constants that depend only on the paper size.

[0063] Finally, in S707, CPU 238 performs global alignment by affine transforming the test image using the affine matrix acquired in step S704 or S706. This makes it possible to acquire a globally aligned image I in which the test image is aligned with the reference image. This globally aligned image I is an image in which any misalignment between the image printed on the print sheet and the paper coordinates caused by factors such as the timing at which the print sheet scan starts or unevenness in the transport speed has been removed from the test image.

[0064] Next, the partial alignment of S602 in Fig. 6 will be described with reference to Fig. 8. The processing described below is realized, for example, by the CPU 238 of the inspection device 109 reading out a program stored in the HDD 255 into the memory 239 and executing it. As an example of the partial alignment, a non-rigid alignment method such as free form deformations (FFD) is used (Fig. 15), but other general alignment methods may also be used.

[0065] In the partial alignment, first, in S801, the CPU 238 arranges L×M control points in a grid pattern on the overall aligned image I. At this time, the distance δ between the control points is calculated from L, M and the image size. The coordinates of the control point on the lth row and mth column are calculated as p l,m Let (l=1,...,L,m=1,...,M).

[0066] Next, in S802, the CPU 238 updates the control points. The update formula is shown in [Formula 1]. μ represents a weighting coefficient, which may be a value such as 0.1, or may be changed according to the speed of updating the control points. ∇c is the weighting coefficient of the control points p shown in [Formula 2]. l,m A set of pixel locations in the neighborhood of l,m is the differential value of the sum of squares of the difference between the pixel values ​​of I' and T in TIFF2026005073000002.tif26154TIFF2026005073000003.tif22126

[0067] Next, in S803, the CPU 238 updates the pixels. The update formula is shown in [Formula 3]. w(x, y) is expressed by [Formula 4], and is a formula for acquiring the coordinates after the alignment process of the coordinates (x, y) in the inspection target image. The bases B0(t), B1(t), B2(t), and B3(t) in [Formula 4] are expressed by [Formula 5], [Formula 6], [Formula 7], and [Formula 8], respectively. Here, as shown in FIG. 15, TIFF2026005073000004.tif19129. In this embodiment, the 16 grid points p(u, v), p(u+1, v), ..., p(u+3, v+3) are used to acquire pixels in the post-registration image I', but this is not limiting. For example, four grid points with close Euclidean distances (x, y) may be used. TIFF2026005073000005.tif26160TIFF2026005073000006.tif17144TIFF2026005073000007.tif17144TIFF2026005073000008.tif26155TIFF2026005073000009.tif17115TIFF2026005073000010.tif26101In S804, the CPU 238 saves the coordinates (x, y) in the image to be inspected and the coordinates after movement for each point moved in S803 as a Look Up Table (LUT) so that the trajectory of alignment for each point can be tracked.

[0068] In S805, the CPU 238 determines whether the update is complete. The determination of whether the update is complete may be made by calculating the distance d between the deformed image I' and the reference image T and determining the distance d based on a threshold value. The file is TIFF2026005073000011.tif17138. When d becomes equal to or less than the threshold, the update process is completed.

[0069] This completes the registration by updating each pixel. This allows the overall registered image to be partially registered with the reference image, resulting in a partially registered image. The partially registered image provides an image with distortion, which is a misalignment that was not achieved by the overall registration, removed, allowing for inspection of image abnormalities by pixel comparison.

[0070] <Acquisition of positional deviation and distortion> Next, in S506, the CPU 238 acquires the amount of positional misalignment using intermediate data acquired during alignment. The flow for acquiring the amount of positional misalignment is as shown in Fig. 9. The processing described below is realized, for example, by the CPU 238 of the inspection device 109 reading out a program stored in the HDD 255 into the memory 239 and executing it. In S901, the CPU 238 acquires the amount of overall positional misalignment, and in S902, the CPU 238 acquires the amount of distortion that could not be achieved by overall alignment and was achieved by partial alignment.

[0071] 10 shows a flow for acquiring the total positional misalignment amount. The processing described below is realized, for example, by the CPU 238 of the inspection device 109 reading out a program stored in the HDD 255 into the memory 239 and executing it.

[0072] In S1001, the CPU 238 determines whether the number of feature points in the reference image is equal to or greater than a specified value. If the number of feature points in the reference image is less than the specified value, the number of feature points is deemed insufficient, and the process proceeds to S1007, and the process of acquiring the overall positional deviation amount is not performed. If the number of feature points is equal to or greater than the specified value in S1001, the process proceeds to S1002, and the process of acquiring the overall positional deviation amount is started.

[0073] First, in S1002, the CPU 238 acquires the coordinates of the four corners of the print sheet from the scanned inspection image. Next, in S1003, the CPU 238 acquires the feature point affine matrix calculated in S704. Next, in S1004, the CPU 238 uses this feature point affine matrix to affine-transform the coordinates of the four corners of the print sheet of the inspection image. This allows the positions of the four corners of the print sheet to be aligned with the positions of the four corners of the reference image. Because the image printed on the print sheet is not printed exactly like the correct reference image, there is a positional misalignment between the print image and the reference image when the four corner coordinates are aligned. Furthermore, there is a positional misalignment between the reference image and the image after feature point affine transformation. In other words, due to the influence of the overall positional misalignment, the alignment results do not match between feature point alignment and alignment using four corner coordinates.

[0074] In S1005, the CPU 238 calculates the difference between the four corner positions of the print sheet of the correct image and the four corner positions of the print sheet after the feature point affine transformation calculated in S1004. This becomes a vector indicating the overall positional deviation. In S1006, the CPU 238 calculates the absolute values ​​of the four vectors at the four corners that indicate the overall positional deviation, selects the largest one among them, and defines this as the overall positional deviation amount.

[0075] Next, a flow for acquiring the amount of distortion will be described with reference to Fig. 11. The processing described below is realized, for example, by the CPU 238 of the inspection device 109 reading out a program stored in the HDD 255 into the memory 239 and executing the program.

[0076] In S1101, the CPU 238 acquires the LUT saved in S804. Next, in S1102, the CPU 238 acquires the coordinates of the final movement of each pixel of the scanned inspection image from the LUT, and sets this movement vector as movement vector v1. This movement vector v1 can be considered to indicate distortion, but since it is the scale of the image after feature point affine transformation, in this embodiment it is normalized to match the scale with the reference image.

[0077] Therefore, in S1103, the CPU 238 obtains the feature point affine matrix obtained in S704, and calculates the inverse transformation matrix of the feature point affine matrix. Then, in S1104, the CPU 238 applies a transformation to the vector v1 using the inverse transformation matrix calculated in S1103 to calculate the vector v2. This is the movement vector v1 without scaling due to the feature point affine transformation, but since it contains errors in scaling that occur during transportation, scaling to the paper size is finally performed.

[0078] In S1105, the CPU 238 acquires the coordinates of the four corners of the print sheet of the inspection image. Next, in S1106, the CPU 238 calculates a four-corner affine matrix for aligning the coordinates of the four corners of the print sheet of the inspection image with the positions of the four corners of the print sheet of the reference image. Then, in S1107, the CPU 238 can perform scaling according to the paper size by converting the vector v2 using the four-corner affine matrix obtained in S1106. This vector is designated as a distortion vector v3.

[0079] Finally, in S1108, CPU 238 calculates the absolute value of distortion vector v3. The absolute value of distortion vector v3 can be considered the amount of distortion for each pixel. The largest of these amounts of distortion is defined as the amount of distortion for this inspection image. Although the processes of S1103 to S1107 are performed here, the difference in the amount of distortion caused by this scaling is not significant, so it is possible to omit these processes and use vector v1 or vector v2 as the distortion vector and their absolute values ​​as the amount of distortion.

[0080] <Inspection settings> The flow of setting up an examination using a UI (User Interface) for setting up an examination will be described below with reference to FIG. Screen 1201 shows an inspection UI window, and the user sets inspection areas including a priority area, a standard area, and a distortion inspection area. A priority area is an area where inspection for image abnormalities is performed with particular emphasis compared to other areas such as a person's face. A standard area is an area where inspection is performed as a standard. A distortion inspection area is an area where distortion is particularly inspected. In this embodiment, an example will be described in which three types of inspection area are set, but the area names, types, and numbers are not limited to this.

[0081] An area 1202 is an area for previewing an image. Here, the reference image registered in S401 is displayed. The inspection area setting described above is set by selecting an area on this reference image. Area 1203 indicates the inspection area. In area 1203, the type of line surrounding the area is the same as that of the four types of inspection area settings described above. For example, area 1211 surrounded by a dotted line in area 1203 is a priority area. Area 1212 surrounded by a dashed line is a standard area.

[0082] Button 1204 indicates a rotation function. By operating button 1204, the preview screen can be rotated by 90 degrees. As shown in the figure, there are two buttons 1204, and clockwise rotation and counterclockwise rotation can be selected, respectively. A button 1205 indicates an OK button. By operating the OK button, the inspection area setting can be saved. A button 1206 indicates a cancel button, and when the cancel button is operated, the input inspection area setting is discarded.

[0083] Area 1207 is a UI for setting the inspection level. Within the frame of area 1207, it is possible to set two inspection areas, a priority area, and a standard area, as well as the inspection level and threshold values ​​that serve as the reference for distortion and misalignment. The type of line used for the frame of the inspection area within each frame of area 1207 indicates the inspection setting area in preview area 1202.

[0084] The distortion inspection setting frame 1215 sets the maximum allowable deviation amount of distortion for the inspection image. The positional deviation threshold 1208 indicates the amount of overall positional deviation that is tolerable when an overall positional deviation occurs.

[0085] Hereinafter, a method for setting up an inspection will be described with reference to FIG. When setting up an image inspection, the user sets the area to be inspected on the reference image displayed in the preview area 1202. Here, the user uses a set priority area button 1209 and a set standard area button 1210. The user can set the area to be inspected, such as areas 1211 and 1212, by selecting a button according to the type of inspection to be performed and selecting a specific area of ​​the reference image in the preview area with a rectangle. At this time, the border of the set area is displayed with the same type of line as the selected button.

[0086] Next, the user sets the inspection reference value for each selected region. The user can set the reference value for each region in the setting frame 1213 for the priority region and the setting frame 1214 for the standard region. The image abnormalities to be set here are round abnormalities (dots) and linear abnormalities (streaks). The inspection level is a parameter that sets the size of each detected abnormality characteristic to determine whether it is an abnormality. For example, there are seven inspection levels, from level 1 to level 7, and level 7 can detect thinner and smaller abnormalities than level 1. In addition, different levels can be set for each inspection item, such as inspection level 7 for dots and inspection level 4 for streaks.

[0087] For an area selected as a priority area using button 1209, an inspection standard value is set in setting frame 1213. The user can select an inspection level for dents and streaks using the pull-down menus. For an area selected as a standard area using button 1210, an inspection standard value is set in setting frame 1214. The user can select an inspection level for dents and streaks using the pull-down menus.

[0088] Note that the parameter settings and the number of levels are not limited to these. In the priority area settings of Fig. 12, it is shown that the user has selected level 7 for the dot inspection level setting and level 7 for the streak inspection level setting. In addition, in the standard area settings, it is shown that the user has selected level 6 for the dot inspection level setting and level 6 for the streak inspection level setting.

[0089] Regarding the positional misalignment inspection, the user can inspect the overall positional misalignment by checking the checkbox for the overall positional misalignment threshold 1208 and entering the maximum allowable value in mm into the box. The overall positional misalignment inspection is executed only if the checkbox for the overall positional misalignment threshold 1208 is checked. If the checkbox is not checked, the overall positional misalignment inspection is not executed. The method for inspecting the overall positional misalignment amount is the same as that for the overall positional misalignment amount described in FIG. 10, and if the inspection image has an overall positional misalignment that exceeds the maximum allowable value, it is determined that there is an overall positional misalignment.

[0090] For distortion inspection, the user sets a distortion threshold value that will serve as the inspection reference value in setting frame 1215. The user enters the distortion threshold value in the frame in mm units. If the user checks the distortion threshold checkbox and inputs a numerical value as the distortion threshold, the amount of distortion in the print sheet is determined using the flow described in Figure 11. If the amount of distortion in the sheet exceeds the input distortion threshold, it is determined that distortion has occurred. Distortion inspection is performed only if the distortion threshold checkbox 1215 is checked. If the checkbox is not checked, distortion inspection is not performed.

[0091] When the user has finished inputting information into each setting item, the user completes the examination settings by operating the button 1205. The input examination settings are saved in the HDD 255.

[0092] <Presentation of results> The UI screen and the display of the search results on the display unit 241 will be described with reference to Fig. 13. The UI in Fig. 13 can be viewed either during or after the examination. Reference numeral 1301 denotes an inspection result window, in which the user can check the inspection results of the print sheet after inspection has been completed.

[0093] The inspection result list 1302 displays the results of inspections that have already been completed. The inspection result list 1302 displays a list of printed sheets that have been determined to be defective by inspection. The user can select the defective sheet they want to check from the inspection result list 1302 by clicking on it, and check the details of the inspection result. The inspection result list 1302 also displays a list of the causes of the sheet being determined to be defective, and five types of defects - vertical streaks, horizontal streaks, dots, misalignment, and distortion - can be distinguished by checking "OK" or "NG" with an X. Note that this is not intended to limit the present invention, and the defect may be expressed using "OK" or "NG" or any other character string or symbol.

[0094] An image of the abnormal sheet is displayed on the inspection image display screen 1303. Of the inspection images, images of sheets determined to be abnormal are saved in the HDD 255. When the user selects a sheet from the abnormal sheets in the inspection result list 1302, the inspection image display screen 1303 switches to the abnormal sheet selected by the user and displays the inspection image of the selected sheet.

[0095] Inspection results 1304 display why the selected abnormal sheet was determined to be abnormal. The types of causes of abnormality displayed in inspection results 1304 match the items in inspection results list 1302. In addition to vertical streaks, horizontal streaks, and dots, there are misalignment and distortion. Misalignment indicates overall misalignment. Inspection results 1304 displays the types of abnormality marked with an "X" in inspection results list 1302. If multiple causes are found, all of the causes are displayed.

[0096] Inspection progress 1305 indicates the progress of the current inspection. The inspection progress 1305 displays the number of sheets that have been inspected in the denominator and the number of sheets that have been determined to be abnormal in the inspection in the numerator. In the example of Fig. 13, inspection of 181 sheets has been completed, and 4 of them were found to be abnormal (NG).

[0097] The end button 1306 is a button for closing the inspection result window 1301, and when the user operates the end button 1306, the inspection result window 1301 is closed. Furthermore, when the end button 1306 is operated during inspection, the printing device 107 inspects all sheets up to the sheet for which printing has currently started, and then the inspection is terminated and the inspection result window 1301 is closed.

[0098] As described above, according to this embodiment, it is possible to determine the amount of distortion that occurs when alignment cannot be achieved by overall alignment and alignment is performed by partial alignment, and to inspect whether the sheet is normal or abnormal based on the amount of distortion.

[0099] <Second embodiment> According to the first embodiment, it was possible to determine whether a print sheet was normal or abnormal by determining the amount of distortion caused by partial alignment between the test image and the reference image. However, when the distortion in the test image is analyzed strictly, as shown in Fig. 16(b), there is distortion caused by the amount of toner applied to the print sheet itself due to printing, and distortion caused by scanning the print sheet with the imaging unit 240 during inspection. The distortion of the print sheet due to printing is the same as that explained in the background art, and is affected by the amount of toner applied during printing, the machine, the paper type, etc.

[0100] On the other hand, distortion caused by scanning a print sheet with the image capture unit 240 occurs due to localized changes in conveyance speed caused by roller speed differences during conveyance, and the degree of distortion tends to be the same for each paper type and printing device. This distortion does not occur on the print sheet itself, but occurs in the scanned image. Because distortion caused by scanning with the image capture unit 240 is not visible on the print sheet, when a scanned print sheet is used as the search target, distortion may be determined even though there is no distortion on the print sheet itself. Therefore, the distortion amount acquired in the second embodiment is determined by removing the influence of the distortion amount caused by scanning, and the distortion amount is determined based only on the distortion of the print sheet. Referring to Figures 16, 17, and 18, a flow for redefining the distortion amount after removing the influence of scanning distortion in this embodiment and using it for inspection is described.

[0101] In the second embodiment, a calibration chart such as that shown in FIG. 16(a) is used. The calibration chart is printed by the printing device 107 and scanned by the imaging unit 240 to obtain a scanned image. This calibration chart is designed to have a small and uniform amount of toner applied, so there is almost no distortion due to printing. Therefore, any distortion detected in the scanned image when this calibration chart is scanned can be attributed to the distortion due to the scan.

[0102] The process of removing the influence of scanning distortion from the distortion amount of a print sheet using a calibration chart will be described with reference to Fig. 17. The process described below is realized, for example, by the CPU 238 of the inspection device 109 reading a program stored in the HDD 255 into the memory 239 and executing it.

[0103] In S1701, the printing device 107 prints a calibration chart, and the CPU 238 stores the calibration chart imaged by the imaging unit 240 in the memory 239.

[0104] Next, in S1702, the CPU 238 obtains a distortion vector in the calibration chart. The distortion vector in the calibration chart is obtained using the same method as the distortion vector v3 in the flow described in FIG. 11. The distortion vector v3 obtained from the calibration chart is set as a calibration vector v4. Then, the coordinates of the scanned image and the calibration vector v4 thus obtained are associated and stored as an LUT.

[0105] Figure 18 is a flow that adds S1801, which removes distortion due to scanning, to the flow of Figure 11. As shown in S1801 of Figure 18, CPU 238 subtracts the amount of movement due to scanning distortion by subtracting calibration vector v4 from movement vector v1, which indicates the final movement amount of each pixel of the scanned inspection image. In this way, the influence of distortion that occurs during scanning can be removed from the distortion amount, making it possible to inspect the printing distortion on the printed sheet.

[0106] <Third embodiment> In the first embodiment, the normality or abnormality of a sheet is determined based on the amount of distortion in the scanned image. However, if an abnormal sheet occurs, the number of printed sheets is reduced due to the abnormal sheet, so printing must be performed again to replenish the number of abnormal sheets. When printing is performed again, the printing conditions are the same, so print distortion caused by the amount of applied toner is likely to recur. Therefore, in the third embodiment, the inspection device 109 presents the user with countermeasures to prevent or mitigate the occurrence of abnormal sheets when reprinting. An example of presenting measures to prevent or mitigate the occurrence of abnormal sheets to the user in this embodiment will be described with reference to FIGS. 19 and 20 .

[0107] FIG. 19 is an example of a UI screen that presents the user with solutions to reduce the likelihood of abnormalities occurring during reprinting. When the user operates the end button 1306, if an abnormality due to distortion was found during the completed inspection, a warning window 1901 is displayed. The warning window 1901 displays a message urging the user to change the paper type, change the distortion threshold via the setting frame 1215, or the like. As described above, it is possible to prevent similar distortions from occurring during reprinting, resulting in abnormal sheets. Furthermore, while FIG. 19 presents a change in paper type as an example, countermeasures for preventing recurrence are not limited to this, and include adjusting the image as shown in FIG. 20, which will be described later.

[0108] FIG. 20 is an example of a UI screen that presents the user with countermeasures to reduce the likelihood of abnormalities occurring during reprinting. When the user operates the end button 1306, if an abnormality due to distortion has occurred in the completed inspection, a warning window 2001 is displayed. The warning window 2001 displays a message urging the user to adjust the image. In automatic image adjustment, the distortion vector v3 and print data stored in the inspection device 109 are received, and the image is automatically adjusted by multiplying the print data by the inverse vector of the distortion vector v3. In this way, the distortion caused by the print data and printing is offset, resulting in a distortion-free printed image.

[0109] As described above, according to the third embodiment, it is possible to prevent distortion from occurring during reprinting and the production of abnormal sheets. In addition to the countermeasures proposed here, the present invention is not limited to the method as long as it can present a method for preventing recurrence, such as making it less likely for distortion to occur by feeding back the acquired distortion vector v3 to the printing device 107.

[0110] <Fourth embodiment> In the first embodiment, the normality or abnormality of a sheet is determined based on the amount of distortion in a scanned inspection image. However, the distortion threshold for the distortion inspection must be input by the user, which requires knowledge of the influence of paper type and paper size on the likelihood of distortion, placing a significant burden on the user. Therefore, in the fourth embodiment, the user inputs the paper type and paper size to preset the distortion threshold. By automatically setting the distortion threshold, the burden on the user can be reduced. A flow for presetting the distortion threshold based on paper type will be described with reference to Figures 21 and 22. The processing described below is implemented, for example, by the CPU 238 of the inspection device 109 reading a program stored in the HDD 255 into the memory 239 and executing it.

[0111] As shown in Fig. 22, a basic value table is prepared in advance, which associates basic values ​​of distortion thresholds with paper types and paper sizes. Generally, the larger the paper size, the greater the distortion, and the thicker the paper, the smaller the deviation and distortion.

[0112] In S2101, the CPU 238 prompts input from the operation unit 242 to acquire information on the paper type and paper size. The acquisition method is not limited to input, and may also be, for example, acquisition of information on the paper set in the paper feed decks 301 and 302 of the printing device 107.

[0113] 22 and determines whether the paper type and paper size obtained in S2101 exist in the basic value table. If the paper type and paper size exist in the basic value table (Yes), the basic value of the distortion amount threshold is obtained and the process proceeds to S2103. If the CPU 238 determines in S2102 that the paper type and paper size obtained in S2102 do not exist in the basic value table, it skips S2103 and proceeds to S402.

[0114] In S2103, the CPU 238 sets the basic value acquired from the basic table as the initial value in the setting frame 1215 of the inspection setting UI in Fig. 12. The initial value set in Fig. 12 may be left as is, or the user may change the setting when accepting the inspection setting in S402. Also, it may be possible to set whether or not to inspect the amount of distortion depending on the type of paper. If the paper size is small or the paper is thick, it may be possible not to inspect the amount of distortion. In this case, there is no need to acquire the amount of distortion itself. As described above, by estimating the amount of distortion from the acquired paper information and presetting it in the inspection settings, the burden on the user of setting a threshold value for the amount of distortion at their own discretion can be reduced.

[0115] <Other embodiments> 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.

[0116] The disclosure of this specification includes the following inspection apparatus, image forming apparatus, inspection method, and program. (Item 1) An inspection device, reading means for reading a sheet on which an image is formed and which is conveyed from the image forming means; a first alignment means for comparing the entire image of the sheet read by the reading means with the entire reference image to detect a misalignment in the formation position of the image of the sheet, and aligning the image of the sheet with the reference image based on the misalignment to obtain a first image; a second alignment means for comparing the first image with the reference image, detecting distortion of each portion of the image on the sheet, and locally aligning the first image with the reference image based on the distortion to obtain a second image; a determining means for determining whether the image on the sheet is normal by obtaining the amount of distortion from the distortion for each portion; An inspection device comprising: (Item 2) Further, a setting means is provided for setting a threshold value for determining whether or not to acquire the amount of distortion and whether or not the image is normal based on the amount of distortion. Item 1. The inspection device according to item 1. (Item 3) Further, the device is provided with a display unit, If the determination means determines that the image is not normal, the display unit displays a message indicating that the distortion is the cause. Item 1 or Item 2. The inspection device according to item 1 or 2. (Item 4) Further, the device is provided with a display unit, If the determining means determines that the image is not normal, the display unit displays a countermeasure to reduce the occurrence of the distortion. Item 3: The inspection device according to any one of items 1 to 3. (Item 5) the reading means reads a calibration chart, the first alignment means and the second alignment means acquire in advance a distortion of the read calibration chart, and the second alignment means, based on the acquired distortion of the calibration chart, removes the distortion caused by the reading means from the distortion of each portion. 5. The inspection device according to any one of items 1 to 4. (Item 6) The determining means determines that the image on the sheet is abnormal if the amount of distortion exceeds a threshold value. 6. The inspection device according to any one of items 1 to 5. (Item 7) the setting means sets a threshold value for determining whether or not to acquire the amount of distortion and whether or not the image is normal based on the amount of distortion, based on the type of sheet; Item 2. The inspection device according to item 2. (Item 8) Furthermore, an abnormality inspection means for inspecting an image for abnormalities on the sheet that has been determined to be normal by the determination means; 8. The inspection device according to any one of items 1 to 7, comprising: (Item 9) The reading means reads the sheet on which the image is formed and which is conveyed from the image forming means, a first alignment means for comparing the entire image of the sheet read by the reading means with the entire reference image to detect a misalignment in the formation position of the image of the sheet, and aligning the image of the sheet with the reference image based on the misalignment to obtain a first image; a second alignment means for comparing the first image with the reference image, detecting distortion of each portion of the image on the sheet, and locally aligning the first image with the reference image based on the distortion to obtain a second image; a determining means for determining whether the image on the sheet is normal by obtaining the amount of distortion from the distortion for each portion; Testing method. (Item 10) On the computer, The reading means reads the sheet on which the image is formed and which is conveyed from the image forming means, a first alignment means for comparing the entire image of the sheet read by the reading means with the entire reference image to detect a misalignment in the formation position of the image of the sheet, and aligning the image of the sheet with the reference image based on the misalignment to obtain a first image; a second alignment means for comparing the first image with the reference image, detecting distortion of each portion of the image on the sheet, and locally aligning the first image with the reference image based on the distortion to obtain a second image; a determining means for determining whether the image on the sheet is normal by obtaining the amount of distortion from the distortion for each portion; A program for executing a process. (Item 11) An image forming apparatus, an image forming means for forming an image on a sheet; The inspection device according to any one of claims 1 to 8, An image forming apparatus comprising:

[0117] The invention is not limited to the above-described embodiments, and various changes and modifications can be made 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]

[0118] 101: Image forming device, 102: External controller, 103: Client PC, 107: Printing device, 109: Inspection device, 240: Imaging unit

Claims

1. An inspection device, reading means for reading a sheet on which an image is formed and which is conveyed from the image forming means; a first alignment means for comparing the entire image of the sheet read by the reading means with the entire reference image to detect a misalignment in the formation position of the image of the sheet, and aligning the image of the sheet with the reference image based on the misalignment to obtain a first image; a second alignment means for comparing the first image with the reference image, detecting distortion of each portion of the image on the sheet, and locally aligning the first image with the reference image based on the distortion to obtain a second image; a determining means for determining whether the image on the sheet is normal by obtaining the amount of distortion from the distortion for each portion; An inspection device comprising:

2. Further, a setting means is provided for setting a threshold value for determining whether or not to acquire the amount of distortion and whether or not the image is normal based on the amount of distortion. The inspection device according to claim 1 .

3. Further, the device is provided with a display unit, If the determination means determines that the image is not normal, the display unit displays a message indicating that the distortion is the cause. The inspection device according to claim 1 .

4. Further, the device is provided with a display unit, If the determining means determines that the image is not normal, the display unit displays a countermeasure to reduce the occurrence of the distortion. The inspection device according to claim 1 .

5. the reading means reads a calibration chart, the first alignment means and the second alignment means acquire in advance a distortion of the read calibration chart, and the second alignment means removes the distortion caused by the reading means from the distortion of each portion based on the acquired distortion of the calibration chart. The inspection device according to claim 1 .

6. The determining means determines that the image on the sheet is abnormal if the amount of distortion exceeds a threshold value. The inspection device according to claim 1 .

7. the setting means sets a threshold value for determining whether or not to acquire the amount of distortion and whether or not the image is normal based on the amount of distortion, based on the type of sheet; The inspection device according to claim 2 .

8. Furthermore, an abnormality inspection means for inspecting an image for abnormalities on the sheet that has been determined to be normal by the determination means; The inspection device of claim 1 , comprising:

9. The reading means reads the sheet on which the image is formed and which is conveyed from the image forming means, a first alignment means for comparing the entire image of the sheet read by the reading means with the entire reference image to detect a misalignment in the formation position of the image of the sheet, and aligning the image of the sheet with the reference image based on the misalignment to obtain a first image; a second alignment means for comparing the first image with the reference image, detecting distortion of each portion of the image on the sheet, and locally aligning the first image with the reference image based on the distortion to obtain a second image; a determining means for determining whether the image on the sheet is normal by obtaining the amount of distortion from the distortion for each portion; Testing method.

10. On the computer, The reading means reads the sheet on which the image is formed and which is conveyed from the image forming means, a first alignment means for comparing the entire image of the sheet read by the reading means with the entire reference image to detect a misalignment in the formation position of the image of the sheet, and aligning the image of the sheet with the reference image based on the misalignment to obtain a first image; a second alignment means for comparing the first image with the reference image, detecting distortion of each portion of the image on the sheet, and locally aligning the first image with the reference image based on the distortion to obtain a second image; a determining means for determining whether the image on the sheet is normal by obtaining the amount of distortion from the distortion for each portion; A program for executing a process.

11. An image forming apparatus, an image forming means for forming an image on a sheet; The inspection device according to any one of claims 1 to 8, An image forming apparatus comprising:

Images