Inspection Device and Inspection System

Abstract

To improve usability in setting an inspection level for inspecting an image on a sheet.SOLUTION: There is provided an inspection system comprising: reading means for optically reading a sheet on which an object image is formed to generate read image data; inspection means for inspecting the object image by comparing the read image data with correct answer image data at an inspection level set out of a plurality of candidate levels to generate a first inspection result; and control means for controlling display of an inspection result on a display device, where, depending on the first inspection result satisfying a predetermined condition, the control means controls the display device so as to display, on a screen, a second inspection result acquired in the case of inspecting the object image at one or more candidate levels different from the inspection level out of the plurality of candidate levels and re-sets the inspection level on the basis of user input.SELECTED DRAWING: Figure 12

Description

Technical Field

[0001] The present disclosure relates to an inspection system for inspecting an image on a sheet. Inspection device and

Background Art

[0002] Conventionally, there has been known an inspection system for inspecting the quality of an image on a sheet by reading a sheet on which an image is formed by a printer with a scanner arranged at the subsequent stage of the printer and analyzing the read image.

[0003] For example, Patent Document 1 discloses a technique for determining the coincidence between images at different inspection levels for each inspection area when comparing read image data corresponding to an inspection target image with correct answer image data.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] How much a user tolerates defects in an image varies depending on various factors such as the use of the printed matter, cost, and productivity. The user cannot always set an optimal inspection level before printing and inspection are started. If an overly high inspection level is set, the number of sheets determined to be defective increases even though they are within the allowable range. On the other hand, if an overly low inspection level is set, the probability of overlooking defects to be detected increases. Although the user can change the setting of the inspection level and instruct printing and inspection again when an undesirable inspection result is output, it has been difficult to know how to change the inspection level.

[0006] ​In view of the above circumstances, an object of the present invention is to improve the usability when setting an inspection level for inspecting an image on a sheet.

Means for Solving the Problem

[0007] According to one aspect, holding means for holding a reference image used for inspection, reading means having a first reading unit for reading the first surface of a sheet on which an image is formed and a second reading unit for reading the second surface of the sheet, setting means for setting an inspection level for inspection of an inspection area, inspection means for inspecting a read image of the sheet read by the reading means based on the inspection level and the reference image, and display means for displaying the result of the inspection by the inspection means, wherein the inspection means inspects a first read image of a first sheet read by the reading means at a first inspection level specified by a user in a first inspection area, inspects the first read image at a second inspection level different from the first inspection level in the first inspection area, and the display means displays a first inspection result for the inspection at the first inspection level and a second inspection result for the inspection at the second inspection level. Inspection device is provided. The corresponding Inspection system is also provided.

Effect of the Invention

[0008] According to the present disclosure, the usability when setting an inspection level for inspecting an image on a sheet is improved.

Brief Description of the Drawings

[0009]

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Best Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. It should be noted that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential to the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are given the same reference numerals, and duplicate descriptions are omitted.

[0011] <1. Overview of the System> FIG. 1 is a schematic diagram showing the configuration of an inspection system 1 according to an embodiment. Referring to FIG. 1, the inspection system 1 includes a personal computer (PC) 10, an external controller 50, and an image forming apparatus 100. The PC 10 is connected to the external controller 50 via a network 20. The network 20 may be a wired communication network or a wireless communication network. For example, the network 20 may include one or more of a LAN (Local Area Network), a WAN (Wide Area Network), and a public communication line. The external controller 50 is connected to the image forming apparatus 100 via a connection line 70. The connection line 70 may be a communication network such as a LAN or a dedicated line for connection to the image forming apparatus 100. As will be described later, the connection line 70 may include a communication line and an image signal line.

[0012] PC10 is a client terminal that issues print jobs to be executed by the image forming apparatus 100. PC10 typically includes a communication interface (I / F), an input device, a display, a storage, a memory, and a processor. One or more applications and a printer driver are installed on PC10. When printing is requested by the user, the printer driver generates page description language (PDL) data representing the image to be printed and transmits a print instruction together with the generated PDL data to the external controller 50. The printer driver can cooperate with the job control unit 60 of the external controller 50, which will be described later, to display a print dialog on the display of PC10, and the user can specify various control parameters related to printing and inspection in the print dialog.

[0013] The external controller 50 receives a print instruction from PC10 and issues a print job to the image forming apparatus 100. The external controller 50 may also be referred to as an image processing controller, a digital front end, or a print server, etc. The configuration of the external controller 50 will be further described later.

[0014] The image forming apparatus 100 is an apparatus that executes a print job to form an image on a sheet. In the present embodiment, the image forming apparatus 100 has an inspection function of reading a sheet on which an image is formed to generate read image data and inspecting the quality of printing (the quality of the image on the sheet) based on the generated read image data. Therefore, the image forming apparatus 100 may also be referred to as an inspection apparatus.

[0015] <2. Schematic Configuration of Image Forming Apparatus> As shown in FIG. 1, the image forming apparatus 100 includes a printer unit 120, an inserter 140, a reader unit 150, a stacker 170, and a finisher 180. The printer unit 120, the inserter 140, the reader unit 150, the stacker 170, and the finisher 180 are connected to each other by signal lines such as communication cables. However, in FIG. 1, only the signal line 101 between the printer unit 120 and the reader unit 150 is shown.

[0016] <2-1. Printer Unit> The printer unit 120 is an image forming means for forming an image on a sheet. In the present embodiment, the printer unit 120 is a color laser printer capable of printing a color image by an electrophotographic method. In other embodiments, the printer unit 120 may be another type of printer such as a monochrome laser printer or an inkjet printer. Also, the entire printer unit 120 or the image forming apparatus 100 may be configured as a multifunction peripheral (MFP).

[0017] In the example of FIG. 1, the printer unit 120 includes an operation panel 110, image forming units 121Y, 121M, 121C, 121K, an intermediate transfer member 126, a transfer unit 127, a fixing unit 128, paper feed trays 131, 132, and a printer controller 200. The operation panel 110 provides a user interface (UI) composed of a combination of a display and an input device to the user. The input device may include, for example, one or more of buttons, numeric keys, a touch panel, and switches. The detailed configuration of the printer controller 200 will be described in detail later.

[0018] The image forming unit 121Y forms a yellow (Y) toner image on the intermediate transfer member 126. The image forming unit 121M forms a magenta (M) toner image on the intermediate transfer member 126. The image forming unit 121C forms a cyan (C) toner image on the intermediate transfer member 126. The image forming unit 121K forms a black (K) toner image on the intermediate transfer member 126. Since the image forming units 121Y, 121M, 121C, and 121K have the same configuration as each other, the configuration of the image forming unit 121Y will be described here as an example. The image forming unit 121Y includes a photosensitive drum 122, a charger 123, an exposure unit 124, and a developing unit 125. The photosensitive drum 122 is a drum-shaped photoreceptor having a photosensitive layer on its surface. The photosensitive drum 122 rotates about the drum axis in the direction of arrow R in the figure. The charger 123 uniformly charges the surface of the rotating photosensitive drum 122. The exposure unit 124 irradiates the photosensitive drum 122 with laser light according to image data (here, representing a yellow image) input from the printer controller 200. The laser light output from the exposure unit 124 scans the surface of the charged photosensitive drum 122 in the drum axis direction, thereby forming an electrostatic latent image on the surface of the photosensitive drum 122. The developing unit 125 supplies (here, yellow) toner to the surface of the photosensitive drum 122 to develop the electrostatic latent image on the photosensitive drum 122. As a result, a toner image is formed on the surface of the photosensitive drum 122. The yellow toner image formed on the surface of the photosensitive drum 122 in the image forming unit 121Y is transferred to the intermediate transfer member 126. Further, the magenta, cyan, and black toner images formed on the surfaces of the respective photosensitive drums 122 in the image forming units 121M, 121C, and 121K are transferred to the intermediate transfer member 126 in order so as to overlap the yellow toner image. Thereby, a full-color toner image is formed on the intermediate transfer member 126. The intermediate transfer member 126 is an endless belt member and rotates in the clockwise direction in the figure. The intermediate transfer member 126 conveys the full-color toner image to the position of the transfer unit 127 (transfer nip).

[0019] Each of the paper feed trays 131 and 132 contains a stack of sheets. The same type of sheets or different types of sheets may be accommodated in the paper feed trays 131 and 132. Although two paper feed trays 131 and 132 are shown in FIG. 1, the number of paper feed trays provided in the image forming apparatus 100 is not limited to two. When a printing job is executed, sheets are picked up one by one from the paper feed tray 131 or 132 by a paper feeding mechanism and conveyed along a conveyance path 133.

[0020] Sheets picked up from the paper feed tray 131 or 132 are conveyed to a transfer nip under the control of a printer controller 200 at a timing when the toner image on the intermediate transfer member 126 reaches the transfer nip. The transfer unit 127 transfers the toner image carried on the intermediate transfer member 126 to the sheet at the transfer nip. The fixing device 128 includes a heater and a pressure roller. The fixing device 128 heats the toner image transferred to the sheet by the heater and applies pressure by the pressure roller. Thereby, the toner on the sheet melts and the toner image is fixed to the sheet. Although FIG. 1 shows an example in which the image forming apparatus 100 includes one fixing device 128, the image forming apparatus 100 may further include a second fixing device used, for example, for increasing gloss or improving fixability.

[0021] The conveyance path 133 branches into conveyance paths 134 and 135 downstream of the fixing device 128. The sheet that has passed through the fixing device 128 is once conveyed from the conveyance path 133 to the conveyance path 135. When the rear end of the sheet enters the conveyance path 135, the conveyance direction is reversed, and the sheet is discharged to a reader unit 150 by a discharge roller 137. When double-sided printing is performed, the sheet that has entered the conveyance path 135 is conveyed to the conveyance path 136, returns from the conveyance path 136 to the conveyance path 133, and passes through the transfer nip again in a front-back reversed form. A toner image is formed on the back surface of the sheet by the transfer unit 127 at the transfer nip, and the toner image is fixed to the sheet by the fixing device 128. The sheet on which images are formed on both sides is discharged to an inserter 140 by the discharge roller 137.

[0022] <2-2. Inserter> The inserter 140 includes an insert tray 141. The insert tray 141 has additional sheets to be inserted between a series of sheets on which images are formed by the printer unit 120 placed thereon. When the insert function is enabled in a print job, the inserter 140 merges the additional sheets supplied from the insert tray 141 at a specified timing between the sheets sequentially received from the printer unit 120. Although not shown in FIG. 1, the inserter 140 may include a controller that controls the insertion of such additional sheets. Instead, the insertion of the additional sheets may be controlled by the printer controller 200 or the reader controller 250. The inserter 140 discharges the sheets received from the printer unit 120 and the additional sheets to the reader unit 150.

[0023] <2-3. Reader Unit> The reader unit 150 is a reading means that optically reads the sheet on which an image is formed by the printer unit 120 and generates read image data representing the read image. In the example of FIG. 1, the reader unit 150 includes an operation panel 115, a sheet sensor 151, a through-feed glass 152, a first reading sensor 153, a through-feed glass 154, a second reading sensor 155, and a reader controller 250. The operation panel 115 provides a user interface consisting of a combination of a display and an input device to the user. The detailed configuration of the reader controller 250 will be described in detail later.

[0024] The sheet sensor 151 detects the leading edge of each sheet received from the inserter 140. The sheet sensor 151 may be, for example, a photointerrupter. The first reading sensor 153 optically reads the lower surface of the sheet passing over the flow-through glass 152 to generate reading image data, and outputs the generated reading image data to the reader controller 250. The second reading sensor 155 optically reads the upper surface of the sheet passing under the flow-through glass 154 to generate reading image data, and outputs the generated reading image data to the reader controller 250. The first reading sensor 153 and the second reading sensor 155 may be, for example, a contact image sensor (CIS) or a line scan camera. The timing at which the first reading sensor 153 and the second reading sensor 155 read the sheet can be controlled by the reader controller 250 based on the timing at which the sheet sensor 151 detects the leading edge of the sheet. The reading image data output from each reading sensor to the reader controller 250 may be, for example, data indicating the RGB signal values at each pixel position. The reader unit 150 discharges each sheet that has passed through the flow-through glass 154 to the stacker 170.

[0025] <2-4. Stacker> The stacker 170 includes a stack tray 171 and an escape tray 172. The stack tray 171 is a large-capacity tray capable of stacking a large number of sheets. When the stack tray 171 is designated as the discharge destination of the sheets in a printing job, the sheets received from the reader unit 150 are sequentially discharged to the stack tray 171. The escape tray 172 is a tray to which sheets determined to be defective as a result of inspection in the reader unit 150 are discharged. Although not shown in FIG. 1, the stacker 170 may include a controller that controls the discharge of the sheets to these trays. Instead, the discharge of the sheets may be controlled by the printer controller 200 or the reader controller 250. The stacker 170 may further include an inversion mechanism for inverting the front and back of the sheets discharged to the stack tray 171. When the stack tray 171 is not designated as the discharge destination of the sheets, the stacker 170 discharges each received sheet (for example, a sheet in which no defect is detected) to the finisher 180.

[0026] <2-5. Finisher> The finisher 180 includes a post-processing mechanism 181, a first discharge tray 182, and a second discharge tray 183. The post-processing mechanism 181 can perform post-processing such as stapling, punching, cutting, or bookbinding (e.g., saddle-stitching) on the sheets or bundles of sheets received from the stacker 170. When the first discharge tray 182 is designated as the discharge destination of the sheets in a print job, the sheets are sequentially discharged to the first discharge tray 182. When it is specified to execute post-processing, one or more sheets are once taken into the post-processing mechanism 181, and after the specified post-processing is executed, the post-processed sheets or bundles of sheets are discharged to the second discharge tray 183. Although not shown in FIG. 1, the finisher 180 may include a controller that controls such post-processing and discharging. Alternatively, the post-processing and discharging may be controlled by the printer controller 200 or the reader controller 250. The finisher 180 may further include a lifting mechanism for raising and lowering the positions of the first discharge tray 182 or the second discharge tray 183 according to the number of sheets to be discharged.

[0027] <3. Configuration Example of Control Function> <3-1. External Controller> FIG. 2 is a block diagram showing an example of the configuration of the external controller 50. Referring to FIG. 2, the external controller 50 includes a first communication I / F 51, a second communication I / F 52, a video I / F 53, a display 54, an input device 55, a CPU 56, a memory 57, and an HDD 58. The first communication I / F 51, the second communication I / F 52, the video I / F 53, the display 54, the input device 55, the CPU 56, the memory 57, and the HDD 58 are interconnected via a system bus 59.

[0028] The first communication I / F 51 is an interface for the external controller 50 to communicate with other devices (e.g., PC 10) via the network 20. The second communication I / F 52 is an interface for mediating control communication between the external controller 50 and the image forming apparatus 100. The video I / F 53 is an interface for mediating communication of image data (e.g., input image data of a print job) between the external controller 50 and the image forming apparatus 100. The display 54 is a device capable of displaying images, videos, and information. The input device 55 is a device capable of receiving user input. The input device 55 may include, for example, one or more of a keyboard, buttons, a touch panel, and a switch. The CPU (Central Processing Unit) 56 is a processing circuit that controls the overall functions of the external controller 50 by executing a computer program stored in the memory 57 or the HDD 58. The memory 57 may be, for example, any combination of RAM (Random Access Memory) and ROM (Read-Only Memory). The RAM provides a temporary storage area for the CPU 56 for calculations. The HDD (Hard Disk Drive) 58 is a storage device capable of storing large amounts of data. The HDD 58 may store, for example, in addition to a computer program, image data and various setting data.

[0029] In the present embodiment, the CPU 56 functions as a job control unit 60. The job control unit 60 controls reception of a print instruction, issuance of a print job to the image forming apparatus 100, and feedback of a job execution result to the user. For example, when a print is instructed by the user, the job control unit 60 generates input image data (RIP data) in bitmap format by rasterizing PDL data representing the image to be printed. The job control unit 60 may further perform image processing such as color conversion, gradation correction, and binarization on the input image data. Then, the job control unit 60 outputs a print job including the generated input image data and control parameters that can be obtained via a UI such as a print dialog to the image forming apparatus 100.

[0030] Note that, regardless of the description herein, the external controller 50 may be omitted from the configuration of the inspection system 1. When the inspection system 1 does not include the external controller 50, the functions of the job control unit 60 may be implemented integrally or distributively in one or more of the PC 10, the printer controller 200, and the reader controller 250.

[0031] <3-2. Printer Controller> FIG. 3 is a block diagram showing an example of the configuration of the printer controller 200. Referring to FIG. 3, the printer controller 200 includes a communication I / F 201, a video I / F 202, a connection I / F 203, an operation I / F 204, a printer I / F 205, a CPU 206, a memory 207, and an HDD 208. The communication I / F 201, the video I / F 202, the connection I / F 203, the operation I / F 204, the printer I / F 205, the CPU 206, the memory 207, and the HDD 208 are interconnected via a system bus 209.

[0032] The communication I / F 201 is an interface that mediates control communication between the printer controller 200 and the external controller 50. The video I / F 202 is an interface that mediates communication of image data between the printer controller 200 and the external controller 50. The connection I / F 203 is an interface that connects the printer controller 200 to the signal line 101. The operation I / F 204 is an interface that connects the printer controller 200 to the display and input devices of the operation panel 110. The CPU 206 is a processing circuit that controls the overall functions of the printer controller 200 by executing a computer program stored in the memory 207 or the HDD 208. The memory 207 may be, for example, any combination of RAM and ROM. The RAM provides a temporary storage area for arithmetic operations to the CPU 206. The HDD 208 is a storage device capable of storing large-scale data.

[0033] In this embodiment, the CPU 206 functions as a print control unit 210. When a print job is received via the communication I / F 201 (or the operation panel 110), the print control unit 210 controls the printer unit 120 to form an image based on the input image data on a sheet in accordance with the control parameters included in the print job. The print control unit 210 can display the progress status and execution result of the print job on the display of the operation panel 110 and report them to the job control unit 60 of the external controller 50 via the communication I / F 201.

[0034] <3-3. Reader Controller> FIG. 4 is a block diagram showing an example of the configuration of the reader controller 250. Referring to FIG. 4, the reader controller 250 includes image processing circuits 251 and 252, a connection I / F 253, an operation I / F 254, a CPU 256, and a memory 257. The image processing circuits 251 and 252, the connection I / F 253, the operation I / F 254, the CPU 256, and the memory 257 are interconnected via a system bus 259.

[0035] The image processing circuit 251 executes image processing such as analog-digital conversion (ADC), color conversion, and noise removal on the read image data generated when the first reading sensor 153 reads the lower surface of the sheet. The image processing circuit 252 executes image processing such as ADC, color conversion, and noise removal on the read image data generated when the second reading sensor 155 reads the upper surface of the sheet. The connection I / F 253 is an interface that connects the reader controller 250 to the signal line 101. The operation I / F 254 is an interface that connects the reader controller 250 to the display and input device of the operation panel 115. The CPU 256 is a processing circuit that controls the overall functions of the reader controller 250 by executing a computer program stored in the memory 257. The memory 257 may be, for example, any combination of RAM and ROM. The RAM provides a temporary storage area for calculations to the CPU 56.

[0036] In this embodiment, the CPU 256 functions as an inspection unit 260. When the inspection function is enabled in a print job, the inspection unit 260 causes the reader unit 150 to read a sheet on which an image has been formed by the printer unit 120, and acquires the read image data. In the case of single-sided printing, the inspection unit 260 acquires the read image data generated by the first reading sensor 153 and processed by the image processing circuit 251 for the lower surface of each sheet. In the case of double-sided printing, the inspection unit 260 further acquires the read image data generated by the second reading sensor 155 and processed by the image processing circuit 252 for the upper surface of each sheet. In the following description, an image of each surface to be inspected represented by the read image data is referred to as an inspection target image.

[0037] The inspection unit 260 inspects each inspection target image by comparing the read image data with the correct image data corresponding to a correct image (reference image) serving as a reference for inspection. For example, the inspection unit 260 divides the inspection target image and the correct image into a plurality of segments, and compares partial images between the inspection target image and the correct image for each segment. The inspection unit 260 may determine that there is no defect (meeting the pass criterion) if the amount of displacement of the position of the content between the partial images is equal to or less than a first threshold value, and determine that there is a defect (not meeting the pass criterion) if the amount of displacement exceeds the first threshold value. Further, the inspection unit 260 may determine that there is no defect if the size of a stain or streak that is not present in the correct image but is present in the inspection target image is equal to or less than a second threshold value, and determine that there is a defect if the size of the stain or streak exceeds the second threshold value. Further, the inspection unit 260 may perform optical character recognition (OCR) on the inspection target image and the correct image, and determine whether there is a defect based on a comparison of the recognized characters. These methods for comparison may be combined with each other in any manner.

[0038] In this embodiment, the inspection unit 260 inspects the inspection target image at an inspection level set from among candidates for a plurality of inspection levels (hereinafter referred to as candidate levels). The higher (more stringent) the inspection level, the smaller the difference between the inspection target image and the correct image can be detected as a printing defect. For example, among the inspection levels "A" and "B", assume that the inspection level "A" is higher. In this case, the determination threshold value (for example, the first threshold value and / or the second threshold value described above) used for the inspection at the inspection level "A" is smaller than the determination threshold value used for the inspection at the inspection level "B". In the following description, the inspection level is represented by an integer value, and a larger numerical value corresponds to a higher inspection level. For example, the inspection level may be one of three candidate levels from level 1 to level 3, or one of five candidate levels from level 1 to level 5.

[0039] In an embodiment, the inspection unit 260 may inspect whether the inspection target image includes a defect (also referred to as a printing defect) within the range of each of one or more inspection areas registered in advance in association with the correct image. Areas not included in any inspection area may be excluded from the inspection. Even if there is a difference between the inspection target image and the correct image in an area excluded from the inspection, the difference is not detected as a printing defect. Also, when two or more inspection areas are registered in association with the correct image, it may be possible to set different inspection levels for the two or more inspection areas. For example, when a photographic image is printed, a first inspection area may be set for the subject area and a second inspection area may be set for the background area, and a relatively high inspection level may be set for the first inspection area and a relatively low inspection level may be set for the second inspection area. The inspection area may be specified by the user using, for example, the PC 10 or the operation panel 110. Also, the inspection unit 260 may automatically specify, as an inspection area, an area recognized by analyzing the correct image (for example, a face area or a person area recognized through image recognition).

[0040] In this embodiment, the correct image data can be generated in advance by reading a sheet (hereinafter referred to as the correct sheet) on which the correct image is formed by the printer unit 120, and can be stored by the memory 257. As an example, the correct sheet may be supplied from the insert tray 141 of the inserter 140 described above and read by the reader unit 150. The inspection unit 260 may generate the correct image data by performing processes such as resolution conversion, noise removal, superposition, and averaging on the read image data of the correct sheet read by at least one of the first reading sensor 153 and the second reading sensor 155. As another example, the correct sheet may be read by a scanner (not shown in FIG. 1) that can be integrated with the printer unit 120. In other embodiments, the correct image data may be data generated based on input image data (RIP data) received when forming the inspection target image on the sheet (without going through the printing and reading steps).

[0041] In an embodiment, the printing defects detected by the inspection unit 260 can be classified into a plurality of defect types. The plurality of defect types may be, for example, two or more of the following: · Bleeding (dot-like stains) · Streaks (linear stains) · Misregistration (displacement of the printed image) · Color misregistration (color tone deviation) · Density irregularity (excessively high density / low density) · Image or character missing The user is supposed to be able to specify which type of defect to inspect as an inspection-related parameter. In the following description, the type of defect to be inspected is referred to as an "inspection item". The inspection unit 260 can inspect the inspection target image using different inspection methods for different inspection items. For example, the detection of stains is performed based on a simple comparison of pixel values with a relatively small segment size, while the detection of streaks can be performed based on a comparison of pixel values and edge comparison with a relatively large segment size. In addition, the inspection unit 260 is capable of performing inspections on two or more types of defects at different inspection levels. For example, if a certain degree of small stains are acceptable while the occurrence of streaks is not, a relatively low inspection level can be specified for stains, and a relatively high inspection level can be specified for streaks.

[0042] The inspection unit 260 can display the progress and results of the inspection on the display of the operation panel 115, and report them to the printer controller 200 (and further to the external controller 50) via the connection I / F 253. The inspection results include the presence or absence of detected printing defects for each inspection target image. For the inspection target image where a printing defect is detected, they include the type of the detected printing defect and the position information indicating the position of the printing defect. The inspection unit 260 may record the inspection results in the inspection log stored in the memory 257 together with the identification information of the inspection target image (e.g., sheet number and front / back distinction) and the inspection date and time. The inspection unit 260 may control the stacker 170 to discharge the defective sheet where a printing defect is detected to the escape tray 172. Alternatively, the defective sheet may be discharged to the same discharge destination as the normal sheet, and the discharge position of the defective sheet may be shifted from the discharge position of the normal sheet at the same discharge destination. By shifting the discharge position, the burden on the user to extract the defective sheet from the stack of discharged sheets can be reduced.

[0043] <4. Configuration Example of User Interface> In this section, some examples of the configuration of the inspection-related UI provided to the user in the inspection system 1 will be described. These UIs may be provided via any display device under the control of at least one (control means) among the printer driver of the PC 10, the external controller 50, the printer controller 200, and the reader controller 250.

[0044] <4-1. Print Job Settings> FIG. 5 is an explanatory diagram showing an example of the configuration of a job setting screen 400 for setting a print job to be executed in the inspection system 1. The job setting screen 400 can be generated by the job control unit 60 of the external controller 50 and displayed on the display.

[0045] Referring to FIG. 5, the job setting screen 400 includes five setting fields 401, 402, 403, 405, 406 for basic settings of the print job, an inspection setting section 410, and buttons 418, 419. The setting field 401 is a field for accepting input of the number of copies to be printed. The setting field 402 is a field for accepting specification of the color mode (e.g., full color or monochrome). The setting field 403 is a field for accepting specification of the print side (e.g., single-sided or double-sided). The setting field 405 is a field for accepting specification of the paper feed tray. The setting field 406 is a field for accepting specification of the discharge destination.

[0046] The inspection settings section 410 includes a checkbox 411, a preview window 412, buttons 413, 417, and setting fields 415, 416. The checkbox 411 is an object for allowing the user to specify whether to enable the inspection for the image printed on the sheet. In the example of FIG. 5, since the checkbox 411 is on, the inspection is enabled. The other objects within the inspection settings section 410 may be operable only when the checkbox 411 is set to on. The preview window 412 displays a preview of a representative correct image when a correct image to be used for the inspection is registered. In the example of FIG. 5, since the correct image is not registered, the preview window 412 does not display a preview of the correct image. The button 413 is a button for calling the correct image registration function of the reader unit 150. An example of the UI related to the registration of the correct image will be described later with reference to FIGS. 6 to 9. The setting field 415 is a field for accepting the designation of the discharge destination of defective sheets (for example, the same as normal sheets or an escape tray). The setting field 416 is a field for accepting the designation of the surface to be inspected (for example, only the front surface, only the back surface, or both surfaces). The designation of the printing surface in the setting field 403 and the designation of the inspection target surface in the setting field 416 do not necessarily have to match (that is, when double-sided printing is performed, only one side may be inspected, and when single-sided printing is performed, both sides may be inspected). The button 417 is a button for calling the detailed setting function related to the inspection. An example of the UI for the detailed setting related to the inspection will be described later with reference to FIG. 10.

[0047] Button 418 is a button for canceling the issuance of a print job and closing the job setting screen 400. Button 419 is a button for instructing the start of execution of a print job. When button 419 is operated by the user, job control unit 60 issues a print job including the input image data and control parameters indicating the settings received via job setting screen 400 to image forming apparatus 100. Print control unit 210 of printer controller 200 receives the print job and executes the print job according to the print-related settings. Further, print control unit 210 transmits an inspection start instruction to reader controller 250 together with control parameters indicating the inspection-related settings. Inspection unit 260 of reader controller 250 executes an inspection according to the inspection-related settings in response to the inspection start instruction. If the correct answer image necessary for the inspection is not registered, inspection unit 260 may notify an error to print control unit 210 and job control unit 60 so that the execution of the print job is not started until the correct answer image is registered.

[0048] FIG. 5 shows an example in which job setting screen 400 includes inspection setting section 410, but inspection setting section 410 may be provided as an inspection setting screen independent of job setting screen 400 (for example, callable from job setting screen 400). Further, inspection setting section 410 or the inspection setting screen may further include an object (for example, a field for inputting the number of printed copies of the correct answer image and a button for triggering printing) for receiving an instruction to print the correct answer image when the correct answer image has been registered.

[0049] <4-2. Registration of Correct Answer Image> FIG. 6 is an explanatory diagram showing an example of the configuration of correct answer image registration screen 430 for receiving registration of a correct answer image. Correct answer image registration screen 430 is generated by inspection unit 260 of reader controller 250 and can be displayed on the display.

[0050] Referring to FIG. 6, the correct image registration screen 430 includes three setting fields 431, 432, 433, and buttons 435, 438, 439. The setting field 431 is a field for accepting input of the number of correct images to be registered. For example, when inspecting printed images on both sides of N sheets (N is a natural number), a total of N×2 correct images need to be registered. The setting field 432 is a field for accepting input of the number of repetitions of reading for registering one correct image. For example, the inspection unit 260 can generate one correct image corresponding to the printed image by synthesizing (e.g., superimposing or averaging) K read images (K is a natural number) generated by reading K sheets on which the same printed image is printed. The setting field 433 is a field for accepting specification of the reading surface (e.g., single-sided or double-sided) of the correct sheet. The button 435 is a button for calling a previously registered correct image as a correct image for a new print job. The button 438 is a button for canceling the registration of the correct image and closing the correct image registration screen 430. The button 439 is a button for instructing the start of reading of the correct sheet. When the button 439 is operated by the user, the inspection unit 260 controls the reader unit 150 to sequentially read the correct sheets conveyed from the inserter 140 to generate read image data, and generates correct image data based on the read image data.

[0051] While the reading of the correct sheet is in progress, the inspection unit 260 notifies the user of the progress of the reading on the display. When the reading of the correct sheet is completed, the inspection unit 260 causes the display to display a confirmation screen for allowing the user to confirm the correct image to be registered.

[0052] FIG. 7 is an explanatory diagram showing an example of the configuration of the correct image confirmation screen 440. Referring to FIG. 7, the correct image confirmation screen 440 includes a selection field 441, a preview window 442, buttons 443, 444, 448, 449, and objects 445a, 445b, 446, 447a, 447b, 447c.

[0053] The selection field 441 is a field that enables switching of the page of the correct answer image to be confirmed. In the following description, the term "page" is used to indicate a position identified by a combination of a sheet and a side (front / back) among a series of images (inspection target images or correct answer images). The preview window 442 is a window in which a preview of the correct answer image of the page selected in the selection field 441 is displayed. The objects 445a and 445b are buttons for moving the selected sheet forward or backward, and the object 446 is a button for inverting the selected side. When the object 445a, 445b, or 446 is operated, the preview display of the correct answer image in the preview window 442 switches along with the selection of the page in the selection field 441. The objects 447a and 447b are buttons for changing the display magnification of the preview in the preview window 442. The object 447c is a set of buttons for moving the portion displayed in the preview window 442 in four directions: up, down, left, and right. Although an example in which several UI objects are arranged on the screen is described in this section, each object may be replaced by a gesture operation (for example, flick, pinch-in, pinch-out, or swipe, etc.) by the user.

[0054] Button 443 is a button for a user who has determined that there is no problem with the (unregistered) correct answer image displayed in the preview window 442 to instruct the registration of the correct answer image. When the button 443 is operated by the user, the inspection unit 260 registers the corresponding correct answer image in association with the page selected in the selection field 441. Button 444 is a button for a user who has determined that there is a problem with the correct answer image (for example, due to occurrence of printing defect, omission of image, or mis-taking of correct answer sheet, etc.) to cancel the registration of the correct answer image. When the button 444 is operated by the user, the inspection unit 260 may discard the corresponding correct answer image. Button 448 is a button for canceling the registration of correct answer images generated by reading a series of correct answer sheets all at once. Button 449 is a button for instructing the registration of all correct answer images generated by reading a series of correct answer sheets all at once.

[0055] FIG. 8 is an explanatory diagram showing an example of the configuration of an inspection area setting screen 450 that can be further displayed on the display when at least one correct answer image is registered. Referring to FIG. 8, the inspection area setting screen 450 includes a selection field 451, a preview window 452, a check box 453, level setting sections 454a, 454b, and buttons 457, 458, 459.

[0056] The selection field 451 is a field that enables switching of the page of the correct answer image to be the target of the inspection area setting. The preview window 452 is a window in which the correct answer image registered in association with the page selected in the selection field 451 is displayed. The check box 453 is an object for allowing the user to specify whether to enable the setting of the inspection area for the correct answer image of the page selected in the selection field 451. When the check box 453 is off, the setting of the inspection level for each inspection area is not performed for the selected correct answer image, and the inspection level may be set for the entire correct answer image. When the check box 453 is on, it becomes possible to perform the setting of the inspection level for each inspection area for the selected correct answer image.

[0057] The level setting section 454a includes an object for receiving a setting of an inspection level for an inspection area automatically set by the inspection unit 260. In the example of FIG. 8, two face areas recognized in the correct image are set as the automatic inspection area, and marks 461 indicating those face areas are superimposed on the preview window 452. The user can specify whether to enable the setting of such an automatic inspection area in the detailed settings described later. The level setting section 454b includes an object for receiving a setting of an inspection level for an inspection area set by the user. In the example of FIG. 8, a designated area specified by a user operation (for example, touch or drag) in the preview window 452 is set as the user's own inspection area (custom area A), and a mark 462 indicating the custom area A is superimposed on the preview window 452.

[0058] Since the configurations of level setting section 454a and level setting section 454b may be the same, level setting section 454b will be taken as an example for explanation here. Level setting section 454b includes checkbox 455a, objects 455b, 455c, checkbox 456a, and objects 456b, 456c. Checkbox 455a is an object for allowing the user to specify whether to enable the inspection for "bleed", which is one of the inspection items. Objects 455b and 455c are buttons for changing the inspection level for "bleed". For example, when the user desires a detailed inspection for "bleed" (when they hope that even a sheet with only small bleeds is detected as a defective sheet), the user sets checkbox 455a to on and operates object 445b to raise the inspection level. Conversely, a user who desires only a rough inspection for "bleed" sets checkbox 455a to on and operates object 445c to lower the inspection level. A user who does not desire an inspection for "bleed" sets checkbox 455a to off. Checkbox 456a is an object for allowing the user to specify whether to enable the inspection for "streak", which is another one of the inspection items. Objects 456b and 456c are buttons for changing the inspection level for "streak". Such setting of the inspection level in level setting section 454b is applied to custom area A.

[0059] The inspection unit 260 may make the color of mark 461 in the preview window 452 and the color of the frame of level setting section 454a the same (for example, blue), and make the color of mark 462 and the frame of level setting section 454b the same (for example, green). Thereby, it becomes easier for the user to understand which settings in which section are applied to which inspection area.

[0060] Button 457 is a button for canceling the setting of the inspection area and returning to the previous screen. Button 458 is a button for transitioning to the screen for additional registration of the correct answer image. Button 458 can be displayed on the inspection area setting screen 450 when, for example, there is a page where it is selected not to register the correct answer image on the correct answer image confirmation screen 440 of FIG. 7. When the user operates button 458, the inspection unit 260 causes the memory 257 to store the settings of the inspection area and the inspection level received via the inspection area setting screen 450, and then causes the display to display an additional registration screen for additional registration of the correct answer image. Button 459 is a button for completing the registration of the correct answer image. When the user operates button 459, the inspection unit 260 stores the settings of the inspection area and the inspection level in the memory 257 and closes the inspection area setting screen 450.

[0061] FIG. 9 is an explanatory diagram showing an example of the configuration of an additional registration screen 470 for additional registration of a correct answer image. Referring to FIG. 9, the additional registration screen 470 includes radio buttons 471a, 471b, setting fields 472, 475, a text field 474, and buttons 473, 478, 479. The radio buttons 471a, 471b are objects that receive an alternative selection as to whether to perform additional registration of the correct answer image only for a specific page or for all pages for which the correct answer image is not registered. When the user performs additional registration of the correct answer image only for a specific page, the user selects the radio button 471a, selects the target page in the setting field 472, and operates the button 473. Then, the selected page is added to the list of pages to be additionally registered. The text field 474 is a field that displays the list of pages to be additionally registered. When the user performs additional registration of the correct answer image for all pages, the user selects the radio button 471b. The setting field 475 is a field that receives input of the number of repetitions of reading for additional registration of one correct answer image. The button 478 is a button for canceling the additional registration of the correct answer image and closing the additional registration screen 470. The button 479 is a button for instructing the start of reading of the correct answer sheet for additional registration. When the button 479 is operated by the user, the inspection unit 260 controls the reader unit 150 to read the correct answer sheet conveyed from the inserter 140 and generate read image data, and generates correct answer image data for additional registration based on the read image data.

[0062] While the reading of the correct answer sheet is in progress, the inspection unit 260 notifies the user of the progress of the reading on the display. When the reading of the correct answer sheet for additional registration is completed, the inspection unit 260 causes the display to display a confirmation screen similar to that described with reference to FIG. 7.

[0063] Note that the inspection unit 260 may send a request for printing the correct answer image to be registered to the printing control unit 210 of the printer controller 200 or the job control unit 60 of the external controller 50 in response to reading of the correct answer sheet for initial registration or additional registration of the correct answer image.

[0064] <4-3. Detailed Settings Related to Inspection> FIG. 10 is an explanatory diagram showing an example of the configuration of a detailed setting screen 480 for detailed settings related to inspection called from the job setting screen 400 (or some other menu screen) described with reference to FIG. 5. The detailed setting screen 480 can be generated by, for example, the inspection unit 260 and displayed on the display.

[0065] Referring to FIG. 10, the detailed setting screen 480 includes check boxes 481a, 482a, 483a, objects 481b, 481c, check boxes 484, 485, 486, and buttons 488, 489. The check boxes 481a, 482a, and 483a are objects for respectively allowing the user to specify whether to enable inspections for "bleed", "streak", and "misalignment", which are candidates for inspection items. In the example of FIG. 10, the check boxes 481a and 482a are set to on. In this case, it is possible to enable the inspections for "bleed" and "streak" on the inspection area setting screen 450 described with reference to FIG. 8. The objects 481b and 481c are buttons for changing the default inspection level for "bleed". Similar objects for changing the inspection levels for "streak" and "misalignment" also exist. The check box 484 is an object for allowing the user to specify whether to enable the setting of the automatic inspection area for the correct image. The check box 485 is an object for allowing the user to specify whether to display a provisional inspection result at a candidate level other than the current inspection level when a defect is detected in the inspection. When the check box 485 is set to on, the inspection unit 260 provides the user with a provisional inspection result at other candidate levels together with the inspection result at the current inspection level on the inspection result screen, which will be described in detail later. The check box 486 is an object for allowing the user to specify whether to discharge a defective sheet that can be detected in the inspection to the escape tray 172 of the stacker 170 or to the same discharge destination as the normal sheet.

[0066] Button 488 is a button for canceling the change of detailed settings and closing the detailed settings screen 480. Button 489 is a button for completing the change of detailed settings. When button 489 is operated by the user, the inspection unit 260 reflects the change of detailed settings received via the detailed settings screen 480 in the settings stored in the memory 257 and closes the detailed settings screen 480. The inspection-related settings received via the detailed settings screen 480 may be applied only to an individual print job or may be applied commonly to a plurality of print jobs.

[0067] <4-4. Display of Inspection Progress> When a print job with inspection enabled is executed, an inspection target image of the inspection is formed on the sheet by the printer unit 120, and the sheet is optically read by the reader unit 150. The inspection unit 260 inspects the inspection target image by comparing the read image data with the correct answer image data at the inspection level set via the above-described UI, and generates a first inspection result. The external controller 50, the printer controller 200, or the reader controller 250 controls the display of the inspection result on the display. In the following description, it is assumed that the inspection unit 260 has a role as a control means for controlling the display of the inspection result, and the inspection result is displayed on the display of the operation panel 115.

[0068] FIG. 11 is an explanatory diagram showing an example of the configuration of an inspection status screen 490 that can be displayed on a display while an inspection on a series of images to be inspected is in progress. Referring to FIG. 11, the inspection status screen 490 includes a status indicator 491, an image window 492, and buttons 498 and 499. The status indicator 491 is an object indicating what percentage of the total number of images to be inspected has been inspected. The image window 492 is a window in which a reduced view of the latest image to be inspected (or the corresponding correct image) for which the inspection has been completed is displayed. The button 498 is a button for stopping (skipping) the inspection on the subsequent image to be inspected. When the button 498 is operated by the user, the inspection unit 260 controls the first reading sensor 153 and the second reading sensor 155 so as not to read the sheet conveyed from the inserter 140 thereafter. The button 499 is a button for interrupting the execution of the printing job. When the button 499 is operated by the user, the inspection unit 260 reports to the printer controller 200 that an instruction to interrupt the job has been given. The printing control unit 210 of the printer controller 200 transfers this report to the job control unit 60 of the external controller 50 and stops the driving of the printer unit 120.

[0069] <4-5. Re - setting of Inspection Level> In this embodiment, when the inspection result of the first inspection (i.e., the inspection result at the current inspection level) satisfies a predetermined condition, the inspection unit 260 acquires a second inspection result when the inspection target image is inspected at one or more candidate levels different from the current inspection level among a plurality of candidate levels. In the following description, the current inspection level is also referred to as the first inspection level, and one or more other candidate levels are also referred to as the second inspection level. Then, the inspection unit 260 controls the display device to display the acquired second inspection result on the screen. As an example, the predetermined condition may include that it is determined in the first inspection result that the inspection target image includes a printing defect. As another example, the predetermined condition may include that it is continuously determined a plurality of times in the first inspection result that the inspection target image includes a printing defect. As a further example, the predetermined condition may include that the number of times it is determined in the first inspection result that the inspection target image includes a printing defect exceeds a predetermined threshold. As still another example, the predetermined condition may include that the inspection has reached a specific page specified in advance. The inspection unit 260 can reset the inspection level from the first inspection level to any one of the second inspection levels based on the user input acquired in response to the display of such a screen.

[0070] When the first inspection result satisfies a predetermined condition, the inspection unit 260 tentatively acquires a second inspection result by comparing the inspection target image with a comparison image at each candidate level. Then, the inspection unit 260 displays the first inspection result and the second inspection result in parallel on an inspection result screen 500 as shown in FIG. 12. Note that the first inspection result and the second inspection result do not necessarily have to be displayed in parallel, and may be displayed across a plurality of mutually transitionable screens, for example.

[0071] FIG. 12 is an explanatory diagram showing an example of the configuration of the inspection result screen 500. Referring to FIG. 12, the inspection result screen 500 includes a target image window 501, an inspection result section 502, a correct answer image window 503, a current setting section 504, a tentative result section 505, and buttons 531, 532, 533.

[0072] The target image window 501 is a window in which a reduced view of the inspection target image where a printing defect has been detected is displayed. In the target image window 501, a mark 506 indicating the position of one or more printing defects detected based on the difference between the read image data and the correct image data is superimposed. The inspection result section 502 is a section in which information regarding the first inspection result at the current inspection level is described. In the example of FIG. 12, the inspection result section 502 describes the identification information of the page where a printing defect has been detected, the name of the inspection area where a printing defect has been detected, the defect type, and the position information of the printing defect. The correct image window 503 is a window in which a reduced view of the correct image used for the inspection of the inspection target image is displayed. The current setting section 504 is a section in which information regarding the current settings of the inspection area and the inspection level associated with the correct image is described.

[0073] The provisional result section 505 is a section that displays a second inspection result indicating the position of at least one printing defect that can be detected at each of one or more candidate levels. In the example of FIG. 12, the provisional result section 505 includes preview windows 511a, 511b, 511c, buttons 512a, 512c, preview windows 521a, 521b, 521c, and buttons 522a, 522c.

[0074] Preview windows 521a, 521b, and 521c respectively show the inspection results when the inspection levels are set to "1", "2", and "3" and the inspection target image is inspected for the presence or absence of bleeding. However, the inspection level "2" is equal to the current inspection level. No mark indicating the position of a printing defect is superimposed on preview window 511a. This means that when the inspection level is reset from "2" to "1", the bleeding detected at inspection level "2" will not be detected as a printing defect. Mark 513a is superimposed on preview window 511b, which indicates the same bleeding detected in the first inspection result. Three marks 513a, 513b, and 513c indicating the positions of printing defects are superimposed on preview window 511c. Marks 513b and 513c indicate bleeding that was not detected in the first inspection result. However, the bleeding indicated by each mark may be actual bleeding or may be small noise that is not actually bleeding. That is, when the inspection level is reset from "2" to "3", more printing defects will be detected than the printing defects detected at inspection level "2". If the user does not want the bleeding indicated by mark 513a to be detected as a printing defect, the user operates button 512a. Then, the inspection unit 260 resets the inspection level for the inspection item "bleeding" to the designated candidate level "1". Alternatively, if the user wants the bleeding indicated by marks 513b and 513c to also be detected as printing defects, the user operates button 512c. Then, the inspection unit 260 resets the inspection level for the inspection item "bleeding" to the designated candidate level "3".

[0075] Preview windows 511a, 511b, and 511c each show the inspection results when the inspection levels are set to "1", "2", and "3" for inspecting the inspection target image with respect to the presence or absence of streaks. However, the inspection level "2" is equal to the current inspection level. Similar to the case of "bleed", when the user operates button 522a, the inspection unit 260 resets the inspection level for the inspection item "streak" to the designated candidate level "1". Also, when the user operates button 522c, the inspection unit 260 resets the inspection level for the inspection item "streak" to the designated candidate level "3".

[0076] That is, in the present embodiment, the user input for resetting the inspection level on the inspection result screen 500 designates one of the one or more candidate levels as the inspection level after resetting. In one example, the user input for resetting the inspection level may designate any of the candidate levels as the inspection level after resetting for one of two or more defect types. In this case, similar to the user input for buttons 512a, 512c, 522a, or 522c in FIG. 12, the same user input may also serve as the designation of the defect type. In another example, the user input for resetting the inspection level may designate any of the candidate levels as the inspection level after resetting for one of the one or more inspection areas. In this case, the same user input may also serve as the designation of the inspection area. However, it is not limited to these examples, and a user input that commonly increases or decreases the inspection level for a plurality of defect types may be adopted. Also, a user input that commonly increases or decreases the inspection level for a plurality of inspection areas may be adopted.

[0077] Button 531 is a button for triggering re-inspection at the inspection level after reconfiguration. The operation of button 531 becomes possible after at least one inspection level has been reconfigured according to user input. When button 531 is operated by the user, inspection unit 260 performs re-inspection on the inspection target image for which a printing defect has once been detected, at the inspection level after reconfiguration. If no printing defect is detected in this re-inspection, the inspection result for the inspection target image can be corrected from defective to normal. That is, immediate correction of the inspection result is possible. Button 532 is a button for stopping the inspection for subsequent inspection target images. Button 533 is a button for triggering resumption of inspection. When button 533 is operated by the user, inspection unit 260 resumes inspection for subsequent sheets. When the inspection level is reconfigured, the inspection for subsequent sheets is performed at the inspection level after reconfiguration.

[0078] In a certain modification, instead of comprehensively displaying the second inspection results at all candidate levels, tentative result section 505 may selectively display only the second inspection results at fewer candidate levels. Inspection unit 260 may select the second inspection level for which the second inspection results are to be displayed, based on user input, or according to predefined conditions. For example, inspection unit 260 may determine the upper limit number of second inspection levels so as to match the size of the available display area, select the number of second inspection levels not exceeding the determined upper limit number, and generate the second inspection results. In particular, when the candidate levels span multiple stages, by thus restricting the number of second inspection levels in this way, the time required for generating the inspection results and preview display can be shortened. Also, the display area can be utilized efficiently to enhance the visibility of the inspection results.

[0079] In another modification, instead of displaying the second inspection results for all valid inspection items, the provisional result section 505 may display the second inspection results only for the inspection items for which printing defects are detected. For example, when the stain and streak inspections are enabled, if it is detected that a certain inspection target image does not contain stains but contains streaks, the inspection unit 260 may perform a provisional inspection at one or more second inspection levels only for the streaks and display the second inspection results on the display. At this time, the inspection unit 260 may accept a user input for resetting the inspection level only for the streaks. In this case, it becomes easy to optimize the inspection level for printing defects of the same type as the actually detected printing defect. Also, the time required for generating and preview-displaying the inspection results can be shortened, and the visibility of the inspection results can also be improved.

[0080] <5. Flow of processing> <5-1. Correct image registration processing> FIG. 13 is a flowchart showing an example of the flow of the correct image registration processing that can be executed by the inspection system 1 in the present embodiment. The correct image registration processing in FIG. 13 can be started, for example, in response to the operation of the button 439 on the correct image registration screen 430 shown in FIG. 6. In the following description, the processing steps are abbreviated as 'S'.

[0081] First, in S101, the inspection unit 260 acquires settings for reading the correct sheet. The settings acquired here may include, for example, the number of correct images to be registered, the number of repetitions of reading for registering one correct image, and the designation of the reading surface of the correct sheet.

[0082] Next, in S103, the inspection unit 260 monitors the sensor signal from the sheet sensor 151 and waits for the timing of reading the correct sheet. Here, for simplicity of explanation, it is assumed that only one side of the correct sheet is the target of reading. When the timing of reading arrives, the process transitions to S105.

[0083] In S105, the first reading sensor 153 optically reads the answer sheet. Then, in S107, the first reading sensor 153 generates read image data. The image processing circuit 251 performs necessary image processing (e.g., resolution conversion, noise removal, superposition, and averaging) on the read image data.

[0084] Next, in S109, the inspection unit 260 determines whether the reading of all the answer sheets is completed. If there is a next sheet to be read, the process returns to S103. If the reading of all the answer sheets is completed, the process proceeds to S111.

[0085] In S111, the inspection unit 260 generates correct answer image data based on the read image data obtained through the iterations of S105 and S107, and causes the display to display a correct answer image confirmation screen 440 including a preview of the correct answer image. The user checks the preview of the correct answer image for each page on the displayed correct answer image confirmation screen 440, and if there is no problem, instructs the registration of the correct answer image.

[0086] The subsequent process branches depending on the user's operation on the correct answer image confirmation screen 440. If one or more correct answer images are discarded (S113 - NO) and the user selects to perform additional registration of the correct answer image (S115 - YES), the process returns to S101, and the answer sheet for additional registration is read. When the registration of the correct answer images for all pages is completed (S113 - YES), or when the user selects not to perform additional registration of the correct answer image (S115 - NO), the process proceeds to S117.

[0087] In S117, the inspection unit 260 acquires the correct image data for which registration has been received. Next, in S119, the inspection unit 260 causes the inspection area setting screen 450 to be displayed on the display. And when it is selected by the user to customize the inspection area / inspection level (S119 - YES), in S121, the inspection unit 260 receives the setting of the inspection area and inspection level for the correct image of each page. If customization of the inspection area / inspection level is not performed, default or automatic settings related to inspection can be used for the inspection.

[0088] <5-2. Inspection Process> FIG. 14 is a flowchart showing an example of the flow of the inspection process that can be executed by the inspection system 1 in the present embodiment. The inspection process in FIG. 14 can be started, for example, in response to the inspection being enabled in the job setting screen 400 shown in FIG. 5 and the execution of the print job being triggered.

[0089] First, in S201, the inspection unit 260 acquires inspection-related settings. The settings acquired here can include, for example, the discharge destination of defective sheets, the designation of the inspection target surface, inspection items, inspection areas, inspection levels, and whether to display inspection results at candidate levels other than the inspection level when a defect is detected. Also, in S203, the inspection unit 260 acquires the registered correct image data.

[0090] Next, in S205, the inspection unit 260 monitors the sensor signal from the sheet sensor 151 and waits for the timing to read the sheet to be inspected. Here, for simplicity of explanation, it is assumed that only one side of each sheet is the target for reading. When the timing for reading arrives, the process transitions to S207.

[0091] In S207, the first reading sensor 153 optically reads the sheet conveyed from the inserter 140. Next, in S209, the first reading sensor 153 generates reading image data. The image processing circuit 251 executes necessary image processing on the reading image data.

[0092] Next, in S211, the inspection unit 260 inspects the inspection target image by comparing the inspection target image represented by the read image data with the correct image according to the settings acquired in S201. For example, the inspection unit 260 determines the presence or absence of printing defects based on the difference between the read image data and the correct image data within the range of each of one or more inspection areas registered in advance in association with the correct image.

[0093] Next, in S213, the inspection unit 260 determines whether a printing defect has been detected in the inspection target image. For example, a printing defect can be detected in the inspection target image if there is a difference exceeding the threshold corresponding to the preset inspection level for the defect type (inspection item) for which the inspection is enabled. If a printing defect is detected, the process proceeds to S220. On the other hand, if no printing defect is detected, the inspection target image is determined to be normal, and the process proceeds to S215.

[0094] In S215, the inspection unit 260 updates the display of the inspection progress. For example, the inspection unit 260 causes the inspection status screen 490 described with reference to FIG. 11 to be displayed on the display, and each time the inspection of one inspection target image is completed, reflects the latest inspection result in the indicators and messages on the screen. Then, the process proceeds to S233.

[0095] In S220, the inspection unit 260 executes inspection result display processing and causes an inspection result screen 500 showing the second inspection results at one or more candidate levels together with the first inspection result (indicating a printing defect) at the current inspection level to be displayed on the display. The detailed flow of the inspection result display processing executed here will be further described later. The inspection unit 260 can reset at least one inspection level based on user input acquired via the inspection result screen 500.

[0096] The subsequent processing branches depending on whether the user has instructed a reinspection for the inspection target image. If the user has instructed a reinspection, the process returns to S211, and the inspection target image is inspected again at the reinspected inspection level. If no reinspection has been instructed, the process proceeds to S233.

[0097] In S233, the inspection unit 260 discharges the sheet to the discharge destination according to the inspection result. For example, a sheet for which no printing defect is detected as the inspection result is discharged to the discharge destination for normal sheets. A sheet for which a printing defect is detected is discharged to the discharge destination for defective sheets.

[0098] Next, in S235, the inspection unit 260 determines whether the inspection of all sheets has been completed. If there is a next sheet to be inspected, the process returns to S205. If the inspection of all sheets has been completed, the inspection process in FIG. 14 ends.

[0099] <5-3. Inspection result display process> FIG. 15 is a flowchart showing an example of the detailed flow of the inspection result display process that can be executed in S220 of FIG. 14.

[0100] Referring to FIG. 15, first, in S221, the inspection unit 260 obtains a first inspection result based on the current inspection level. The first inspection result may include, for example, the defect type and position information for each detected printing defect.

[0101] Next, in S222, the inspection unit 260 performs a provisional inspection at each of one or more candidate levels different from the current inspection level to obtain a corresponding second inspection result. The second inspection result may also include the defect type and position information for each detected printing defect.

[0102] Next, in S223, the inspection unit 260 causes a display to display an inspection result screen 500 showing the first inspection result and the second inspection result. For example, on the inspection result screen 500, based on the first inspection result, a mark indicating the position of the printing defect detected at the current inspection level is superimposed on the reduced view of the inspection target image. Similarly, based on the second inspection result, marks indicating the positions of the printing defects detected at each candidate level are superimposed on the reduced view of the inspection target image.

[0103] In S224, the inspection unit 260 waits for a user input instructing re - setting of the inspection level. When receiving a user input instructing re - setting of the inspection level, in S225, the inspection unit 260 re - sets the inspection level according to the user input. For example, the inspection unit 260 re - sets the inspection level of the specified inspection item to the specified candidate level.

[0104] In S226, when receiving a user input instructing resumption of inspection or re - inspection on the inspection result screen 500, the inspection unit 260 ends the display of the inspection result. Then, the process proceeds to S231 in FIG. 14, and re - inspection of the inspection target image or inspection of the subsequent sheet is performed.

[0105] <6. Summary> So far, various embodiments, examples and modifications of the technology according to the present disclosure have been described with reference to FIGS. 1 to 15. According to the above - described embodiments, the reading means of the inspection system optically reads a sheet on which a target image is formed and generates read image data. The inspection means inspects the target image by comparing the read image data with correct answer image data at an inspection level set from a plurality of candidate levels, and generates a first inspection result. The control means acquires a second inspection result when the target image is inspected at one or more candidate levels different from the inspection level among the plurality of candidate levels in response to the first inspection result satisfying a predetermined condition. Then, the control means causes the acquired second inspection result to be displayed on the screen, and re - sets the inspection level based on a user input acquired thereafter. Therefore, the user can easily grasp how to change the inspection level from the visual information on the screen displaying the inspection result, and give an appropriate instruction to the inspection system for re - setting the inspection level. Thereby, the usability when setting the inspection level for inspecting an image on a sheet is improved.

[0106] In addition, in the above-described embodiment, the above-described predetermined conditions include that it is determined that the target image includes a printing defect. Therefore, when an undesirable inspection result is output, the inspection level can be quickly optimized, and as a result, usability is improved, errors in detecting printing defects are reduced, and inspection productivity is also improved.

[0107] In addition, in the above-described embodiment, the above-described first inspection result at the current inspection level and the above-described second inspection results at one or more candidate levels can be displayed in parallel on the screen. Therefore, when the user resets the inspection level, the user can intuitively grasp how the printing defects increase or decrease by comparing the two inspection results. Thereby, usability is further improved.

[0108] In addition, in the above-described embodiment, the user input for resetting the inspection level can specify one of the above-described one or more candidate levels as the inspection level after resetting. In one example, the user input can specify the inspection level after resetting for one of two or more defect types. In this case, it is possible to flexibly adjust the inspection level for each defect type according to the use of the printed matter. Also, in one example, the user input can specify the inspection level after resetting for a specific inspection area registered in association with the correct image. In this case, it is possible to receive a detailed adjustment of the inspection level specialized for a limited part emphasized in the target image, and further improvement in usability is achieved.

[0109] Note that the embodiments, examples, and modifications described in this specification may be combined with each other in any manner.

[0110] <7. Other Embodiments> The above-described embodiments can also be implemented in a form of processing in which a program that realizes one or more functions is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. Further, it can also be implemented by a circuit (for example, ASIC) that realizes one or more functions.

[0111] 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. Therefore, the claims are attached to disclose the scope of the invention.

Description of Reference Numerals

[0112] 1: Inspection system, 10: PC, 20: Network, 50: External computer, 60: Job control unit, 100: Image forming apparatus, 110, 115: Operation panel, 120: Printer unit, 140: Inserter, 150: Reader unit, 153, 155: Reading sensor, 170: Stacker, 171: Stack tray, 172: Escape tray, 180: Finisher, 200: Printer controller, 210: Printing control unit, 250: Reader controller, 260: Inspection unit, 400: Job setting screen, 430: Correct image registration screen, 440: Correct image confirmation screen, 450: Inspection area setting screen, 470: Additional registration screen, 480: Detailed setting screen, 490: Inspection status screen, 500: Result display screen

Claims

Claim 1: A holding means for holding a reference image used for inspection, a reading means having a first reading unit for reading the first surface of the sheet on which the image is formed and a second reading unit for reading the second surface of the sheet, a setting means for setting an inspection level for inspection within an inspection area, an inspection means for inspecting a read image of the sheet read by the reading means based on the inspection level and the reference image, a display means for displaying the result of the inspection by the inspection means, comprising: The inspection means: inspects the first read image of the first sheet read by the reading means at a first inspection level specified by the user in a first inspection area, and inspects the first read image at a second inspection level different from the first inspection level in the first inspection area, The display means displays a first inspection result regarding the inspection at the first inspection level and a second inspection result regarding the inspection at the second inspection level. An inspection apparatus. Claim 2: The inspection apparatus according to claim 1, wherein the display means displays the first inspection result and the second inspection result on the same screen. Claim 3: The inspection apparatus according to claim 2, wherein the inspection area is an area corresponding to a part of the read image. Claim 4: The inspection apparatus according to claim 3, wherein the setting means can set the inspection level in one of a first mode for setting an inspection level for an inspection area corresponding to the entire read image and a second mode for setting an inspection level for an inspection area corresponding to a part of the read image. Claim 5: The inspection apparatus according to claim 4, wherein the reading means reads a sheet conveyed from an image forming apparatus that forms an image on the sheet via an inserter. Claim 6: The inspection apparatus according to claim 2, wherein the display means displays the first inspection result and the second inspection result in parallel on the same screen. Claim 7: The inspection apparatus according to claim 1, wherein the inspection area is an area corresponding to the entire read image. Claim 8: The inspection apparatus according to claim 1, wherein the inspection area is an area corresponding to a part of the read image. **Claim 9**: The inspection means executes the inspection in the first inspection area of the first read image at the first inspection level to generate a first inspection result, and executes the inspection in the first inspection area of the first read image at the second inspection level to generate a second inspection result without causing the reading means to read the first sheet again. The inspection apparatus according to claim 1. **Claim 10**: The inspection means sets the first inspection level before the first sheet is read by the reading means, and sets the second inspection level after the first sheet is read by the reading means. The inspection apparatus according to claim 1. **Claim 11**: The inspection means sets the first inspection level before the first sheet is read by the reading means, sets the second inspection level based on user input after the first sheet is read by the reading means, The inspection means executes the inspection in the first inspection area of the first read image at the second inspection level to generate a second inspection result without causing the reading means to read the first sheet again. The inspection apparatus according to claim 1. **Claim 12**: The display means displays, on the screen, a first object for allowing the user to specify the second inspection level after the first sheet is read by the reading means. The inspection apparatus according to claim 1. **Claim 13**: The second inspection level is higher than the first inspection level, In the second inspection result, more defects are detected than in the first inspection result. The inspection apparatus according to claim 1. **Claim 14**: The inspection means executes the inspection in the first inspection area of the first read image at the second inspection level when a defect is detected in the first inspection result. The inspection apparatus according to claim 1. **Claim 15**: The setting means can set the inspection level in one of a first mode for setting the inspection level for an inspection area corresponding to the entire read image and a second mode for setting the inspection level for an inspection area corresponding to a part of the read image. The inspection apparatus according to claim 1. **Claim 16**: The setting means can set the type of defect specified by the user as the type of defect to be detected by the inspection means. The inspection apparatus according to claim 1.

17. The inspection apparatus according to claim 1, wherein the reading means reads a sheet that has been conveyed from an image forming apparatus that forms an image on the sheet via an inserter.

18. The inspection means detects a defect based on a difference between the read image and the reference image, The first inspection result indicates the positions of the respective defects detected at the first inspection level, The second inspection result indicates the positions of the respective defects detected at the second inspection level, The inspection apparatus according to claim 1.

19. The inspection apparatus according to claim 12, wherein the first object receives a user input that designates one of one or more of the second inspection levels.

20. The inspection means is capable of performing inspections on two or more defect types at different inspection levels, The first inspection level is set for one of the two or more defect types, The inspection apparatus according to claim 1.

21. The inspection means is capable of performing inspections on two or more defect types at different inspection levels, The inspection apparatus according to claim 1, wherein the inspection means performs the inspection on the first inspection area of the first read image at the second inspection level for the type of defect detected in the first inspection result.

22. One or more of the inspection areas are registered in association with the reference image, The inspection means inspects the read image within the range of each registered inspection area. The inspection apparatus according to claim 1.

23. The inspection apparatus according to claim 22, wherein the second inspection level is set for one of one or more of the inspection areas registered in association with the reference image.

24. The inspection apparatus according to claim 1, wherein the inspection means performs the inspection on the first inspection area of the first read image at one or more of the second inspection levels selected from a plurality of candidate levels so as not to exceed an upper limit number.

25. The inspection apparatus according to claim 24, wherein the upper limit number is determined based on the size of the available display area of the display means.

26. The inspection apparatus according to claim 1, wherein the reference image is generated in advance by reading the sheet on which the reference image is formed, or is generated based on input image data of a print job.

27. An image forming apparatus that forms an image on the sheet, The inspection apparatus according to any one of claims 1 to 26, An inspection system including

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