Image forming apparatus

Abstract

To secure the amount of information and execute real-time processing on read image data obtained by image sensors.SOLUTION: A first image sensor 3a reads an output image formed on a sheet. A second image sensor 3b reads the output image at a resolution lower than the resolution of the first image sensor 3a. An image data processing unit 8c executes first data processing on first read image data obtained by the first image sensor 3a, and second data processing on second read image data obtained by the second image sensor 3b and different from the first data processing.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus capable of inspecting the quality of an image formed on a sheet. [Background technology]

[0002] The image forming apparatus includes a printing device that executes a printing process, which is a process for forming an image on a sheet.

[0003] Furthermore, it is known that the image forming apparatus includes an image sensor that reads the output image formed on the sheet, and inspects the quality of the output image based on the read image (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-78366 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, if an image sensor with a high resolution is used, it is possible to inspect the quality of the output image in more detail.

[0006] On the other hand, when an image sensor with high resolution is employed, the amount of information in the read image data obtained by the image sensor is large, and the load of processing the read image data is large.

[0007] When the load of processing the read image data is large, due to limitations in the processing capacity of the data processing device, it is difficult to perform real-time processing of the read image data for each sheet in parallel with the continuous printing process when the continuous printing process is being executed.

[0008] An object of the present invention is to provide an image forming apparatus that can ensure both the amount of information regarding the read image data obtained by the image sensor and real-time processing when an output image formed on a sheet is read by the image sensor. [Means for solving the problem]

[0009] An image forming apparatus according to one aspect of the present invention includes a printing device, a first image sensor, a second image sensor, and an image data processing unit. The printing device executes a printing process to form an image on a sheet transported along a transport path. The first image sensor is disposed downstream of the printing device in a sheet transport direction and reads an output image formed on the sheet. The second image sensor is disposed downstream of the printing device in the sheet transport direction and reads the output image at a resolution lower than the resolution of the first image sensor. The image data processing unit executes a first data process on first read image data obtained by the first image sensor and a second data process different from the first data process on second read image data obtained by the second image sensor. Effect of the Invention

[0010] According to the present invention, when an output image formed on a sheet is read by an image sensor, it is possible to provide an image forming apparatus that can achieve both ensuring the amount of information about the read image data obtained by the image sensor and real-time processing. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing the configuration of an image forming apparatus according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing the configuration of a control device in the image forming apparatus according to the embodiment. [Diagram 3] FIG. 3 is a diagram showing an example of an arrangement state of two image sensors in the image forming apparatus according to the embodiment. [Figure 4] FIG. 4 is a flowchart showing an example of a procedure of an image inspection process in the image forming apparatus according to the embodiment. [Diagram 5] FIG. 5 is a flowchart showing an example of a procedure for error processing in the image forming apparatus according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the following embodiment is an example of the present invention, and is not intended to limit the technical scope of the present invention.

[0013] [First embodiment: configuration of image forming apparatus 10] The image forming apparatus 10 according to the first embodiment includes a sheet storage unit 1, a sheet conveying device 2, and a printing device 5 (see FIG. 1).

[0014] The image forming apparatus 10 further includes a human interface device 800 and a control device 8. The control device 8 controls the sheet transport device 2 and the printing device 5.

[0015] The sheet conveying device 2 sends out the sheets 9 accommodated in the sheet accommodating unit 1 one by one to the conveying path 200. The sheet conveying device 2 further conveys the sheets 9 along the conveying path 200.

[0016] In this embodiment, the sheet conveying device 2 includes a primary conveying device 21, a belt conveying device 22, and a secondary conveying device .

[0017] The primary transport device 21 includes a sheet feeding mechanism 211 and a plurality of primary transport roller pairs 212 .

[0018] The sheet feeding mechanism 211 feeds the sheet 9 from the sheet storage unit 1 to the conveying path 200. The primary conveying roller pair 212 conveys the sheet 9 along the conveying path 200, and further sends the sheet 9 to the belt conveying device 22.

[0019] The belt conveying device 22 takes over the conveyance of the sheet 9 from the primary conveying device 21. The belt conveying device 22 conveys the sheet 9 along the conveying path 200, and further sends the sheet 9 to the secondary conveying device 23.

[0020] The belt conveying device 22 includes a conveying belt 221 and a plurality of support rollers 32. The belt conveying device 22 further includes a motor (not shown) that rotates one of the plurality of support rollers 32.

[0021] The conveyor belt 221 is an endless belt member. The conveyor belt 221 is rotatably supported by a plurality of support rollers 32. When one of the plurality of support rollers 32 rotates, the conveyor belt 221 rotates.

[0022] The belt conveying device 22 conveys the sheet 9, which has been sent out onto the conveying belt 221 by the primary conveying device 21, along the upper surface of the conveying belt 221. The belt conveying device 22 sends out the sheet 9 from the upper surface of the conveying belt 221 to the secondary conveying device 23. The area along the upper surface of the conveying belt 221 is a part of the conveying path 200.

[0023] The secondary conveying device 23 takes over the conveying of the sheet 9 from the belt conveying device 22. The secondary conveying device 23 conveys the sheet 9 along the conveying path 200, and further sends the sheet 9 from the conveying path 200 to a downstream part (not shown). For example, the downstream part is a discharge tray, a post-processing device, an intermediate conveying device, or the like.

[0024] The printing device 5 executes a printing process. The printing process is a process of forming an image on a sheet 9 conveyed along a conveying path 200.

[0025] In this embodiment, the printing device 5 forms an image on the sheet 9 conveyed by the belt conveying device 22. In the example shown in Fig. 1, the printing device 5 executes the printing process by an inkjet method.

[0026] In the example shown in FIG. 1, the printing device 5 includes a plurality of inkjet units 51 corresponding to a plurality of colors, and a plurality of ink supply units 52.

[0027] The ink supply units 52 each supply ink of a different color to the inkjet units 51. The inkjet units 51 form an image on the sheet 9 by ejecting ink onto the sheet 9.

[0028] The printing device 5 may be a device that executes the printing process using a method other than the inkjet method, such as an electrophotographic method.

[0029] [Human interface device 800] The human interface device 800 includes an operation device 801 and a display device 802 .

[0030] The operation device 801 is a device that detects operations by a person. For example, the operation device 801 includes one or both of a touch panel and operation buttons.

[0031] The display device 802 is a device that displays various types of information. For example, the display device 802 is a panel display device such as a liquid crystal display panel.

[0032] [Control device 8] The control device 8 includes a central processing unit (CPU) 81, a random access memory (RAM) 82, a secondary storage device 83, a signal interface 84, a communication device 85, and the like.

[0033] The secondary storage device 83 is a computer-readable non-volatile storage device. The secondary storage device 83 can store and update computer programs and various data. For example, one or both of a flash memory and a hard disk drive are adopted as the secondary storage device 83.

[0034] The signal interface 84 converts signals output by various sensors into digital data, and transmits the converted digital data to the CPU 81. Furthermore, the signal interface 84 converts control commands output by the CPU 81 into control signals, and transmits the control signals to the devices to be controlled.

[0035] The communication device 85 executes communication with other devices such as the management device 7. The CPU 81 communicates with the other devices through the communication device 85. The management device 7 is an information processing device such as a personal computer.

[0036] The CPU 81 is a processor that executes the computer program to perform various data processing and control operations. The control device 8 including the CPU 81 controls the sheet transport device 2, the printing device 5, and the like.

[0037] The RAM 82 is a computer-readable volatile storage device that temporarily stores the computer programs executed by the CPU 81 and data output and referenced by the CPU 81 in the course of executing various processes.

[0038] The CPU 81 includes a plurality of processing modules that are realized by executing the computer programs, and the plurality of processing modules include a main processing unit 8a and a print control unit 8b.

[0039] The main processing unit 8a executes processes to start various processes in response to the occurrence of various processing events, such as an operation event and a reception event.

[0040] The operation event is an event that various processing request operations are detected by the operation device 801. The reception event is an event that various processing request commands are received through the communication device 85. The processing request includes a print request for requesting execution of the print process.

[0041] The print control unit 8b controls the sheet transporting device 2 and the printing device 5. The print control unit 8b controls the sheet transporting device 2 to thereby control the transport of the sheet 9.

[0042] Furthermore, the print control unit 8b causes the printing device 5 to execute the print process in synchronization with the conveyance of the sheet 9 by the sheet conveying device 2.

[0043] For example, when the print request is received by the communication device 85, the print control section 8b causes the sheet conveying device 2 to convey the sheet 9 and causes the printing device 5 to execute the print process.

[0044] The management device 7 includes a CPU 71, a secondary storage device 72, a communication device 73, and a human interface device 74 (see FIG. 2). The CPU 71 is capable of communicating with the image forming apparatus 10 through the communication device 73.

[0045] The secondary storage device 72 is a computer-readable non-volatile storage device. For example, a flash memory or a hard disk drive or both may be employed as the secondary storage device 72.

[0046] The CPU 71 of the management device 7 is capable of acquiring data from the image forming apparatus 10 via the communication device 73 and recording the acquired data in the secondary storage device 72 .

[0047] The human interface device 74 includes an operation unit such as a touch panel, a mouse, or a keyboard, and a display unit such as a liquid crystal display.

[0048] The image forming apparatus 10 includes an image sensor 3 that reads an output image G1 formed on a sheet 9 (see FIG. 3). The image forming apparatus 10 includes a function of inspecting the quality of the output image G1 based on the read image data obtained by the image sensor 3.

[0049] Incidentally, if an image sensor with a high resolution is used, it is possible to inspect the quality of the output image G1 in more detail.

[0050] On the other hand, when an image sensor 3 with high resolution is employed, the amount of information in the read image data obtained by the image sensor 3 is large, and the load of processing the read image data is large.

[0051] When the load of processing the read image data is large, due to limitations in the processing capacity of the data processing device, it is difficult to perform real-time processing of the read image data for each sheet in parallel with the continuous printing process when the continuous printing process is being executed.

[0052] The image forming apparatus 10 has a configuration for ensuring the amount of information regarding the read image data obtained by the image sensor 3 and for real-time processing.

[0053] In the following description, the direction in which the sheet 9 is conveyed along the conveying path 200 is referred to as a sheet conveying direction D1 (see FIGS. 1 and 3). Also, the direction intersecting the sheet conveying direction D1 is referred to as a width direction D2 (see FIGS. 1 and 3).

[0054] The width direction D2 corresponds to the main scanning direction in the printing device 5. Moreover, the sheet transport direction D1 is a direction along the sub-scanning direction in the printing device 5. In this embodiment, the width direction D2 is a direction perpendicular to the sheet transport direction D1.

[0055] The image forming apparatus 10 includes two image sensors 3 (see FIGS. 1 and 3). The two image sensors 3 are disposed downstream in a sheet conveying direction D1 with respect to the printing device 5. Each of the image sensors 3 is, for example, a line sensor such as a CIS (Contact Image Sensor).

[0056] In this embodiment, the two image sensors 3 are disposed facing each other in an area between the belt conveying device 22 and the secondary conveying device 23 in the conveying path 200 (see FIG. 1). The two image sensors 3 are disposed at two positions offset from each other in the sheet conveying direction D1.

[0057] Each image sensor 3 reads an image of a sheet passing area in the width direction D2 from the sheet 9 (see FIG. 3). Each image sensor 3 reads an output image G1 read from the sheet 9. The sheet passing area is an area corresponding to the maximum width of the sheet 9 that can be used.

[0058] The two image sensors 3 include a first image sensor 3a and a second image sensor 3b (see FIGS. 1 and 3). The resolution of the second image sensor 3b is lower than that of the first image sensor 3a. That is, the second image sensor 3b reads the output image G1 at a resolution lower than that of the first image sensor 3a.

[0059] The image forming apparatus 10 further includes two white reference members 4 (see FIGS. 1 and 3) disposed opposite the two image sensors 3. Each of the white reference members 4 has a white surface.

[0060] The two image sensors 3 output data of a white image by executing a process of reading an image when the sheet 9 is not being conveyed. The white image is an image representing the surfaces of the two white reference members 4.

[0061] The white image data is used in a sensitivity adjustment process for adjusting the sensitivity of each image sensor 3. A description of the sensitivity adjustment process will be omitted.

[0062] In this embodiment, each of the white reference members 4 is a roller-shaped member that is supported so as to be able to rotate freely.

[0063] Since the two white reference members 4 are roller-shaped, the sheet 9 is smoothly transported along the circumferential surfaces of the two white reference members 4.

[0064] The plurality of processing modules of the CPU 81 further includes an image inspection unit 8c (see FIG. 2). The print control unit 8b and the image inspection unit 8c execute an image inspection process (see FIG. 4), which will be described later.

[0065] The data of the two read images obtained by the two image sensors 3 are used in the image inspection process.

[0066] [Image inspection processing] An example of the procedure of the image inspection process will be described below with reference to the flowchart shown in FIG.

[0067] The image inspection unit 8c starts the image inspection process when a continuous print process, which is a continuous repetition of the print process, is started. As a result, the print control unit 8b and the image inspection unit 8c execute the image inspection process in parallel with the continuous print process.

[0068] In the following description, S101, S102, ... represent identification codes of a plurality of steps in the image inspection process. In the image inspection process, the process of step S101 is executed first.

[0069] <Process S101> In step S101, the image inspection unit 8c waits until the page printing, which is the print processing for one page, is completed.

[0070] When the page printing, which is the print processing for one page, is completed, the image inspection unit 8c shifts the process to step S102.

[0071] <Process S102> In step S102, when the sheet 9 on which the output image G1 is formed passes through an area facing the two image sensors 3, the image inspection unit 8c causes the two image sensors 3 to execute a process of reading the output image G1.

[0072] By executing the process of step S102, each image sensor 3 outputs to the control device 8 data of the read image representing the output image G1.

[0073] In the following description, the data of the read image obtained by the first image sensor 3a is referred to as first read image data, and the data of the read image obtained by the second image sensor 3b is referred to as second read image data.

[0074] After executing the process of step S102, the image inspection unit 8c shifts the process to step S103.

[0075] <Process S103> In step S103, the image inspection unit 8c records the first read image data in the secondary storage device 83 of the image forming apparatus 10 or the secondary storage device 72 of the management apparatus 7.

[0076] For example, the image inspection unit 8c records the first read image data in the secondary storage device 83 through a data bus (not shown). Alternatively, the image inspection unit 8c records the first read image data in the secondary storage device 72 by transmitting the first read image data and a recording request command to the management device 7 through the communication device 85.

[0077] After executing the process of step S103, the image inspection unit 8c shifts the process to step S104.

[0078] <Process S104> In step S104, the image inspection unit 8c shifts the process to step S101 until the print process for the preset number of pages is completed. As a result, the process after step S101 corresponding to the print process for a new page is executed.

[0079] In Fig. 4, N represents a predetermined integer equal to or greater than 1. N in Fig. 4 represents the specified number of pages.

[0080] When the print process for the predetermined number of pages is completed, the image inspection unit 8c shifts the process to step S105.

[0081] <Process S105> In step S105, the image inspection unit 8c executes a simplified inspection process based on the second read image data.

[0082] In the simplified inspection process, the image inspection unit 8c judges whether or not the second scanned image data satisfies an allowable condition based on the reference image data.

[0083] The reference image data is image data corresponding to the output image G1. For example, the reference image data is data that represents the output image G1 at the same resolution as the resolution of the second image sensor 3b.

[0084] In the present embodiment, the image inspection unit 8c detects defective pixels and noise pixels in the second read image data in the simplified inspection process, and counts the numbers of the defective pixels and noise pixels.

[0085] The defective pixels are pixels among the drawing pixels in the reference image data that overlap with blank pixels in the second read image data, and the noise pixels are pixels among the blank pixels in the reference image data that overlap with drawing pixels in the second read image data.

[0086] The simplified inspection process is image processing based on image data with a relatively low resolution, and therefore the computation load of the simplified inspection process is relatively low.

[0087] In addition, the process of detecting the defective pixels and the noise pixels can be realized by processing binarized image data, and therefore the process of detecting the defective pixels and the noise pixels has a lower computation load than the process of determining the density of each pixel in the output image G1.

[0088] The image inspection unit 8c determines, as the permissible condition, that the number of the detected defective pixels is the permissible number of defective pixels and that the number of the detected noise pixels is the permissible number of noise pixels.

[0089] The image inspection unit 8c judges the output image G1 to be normal when the number of the defective pixels and the number of the noise pixels satisfy the tolerance conditions, whereas the image inspection unit 8c judges the output image G1 to be abnormal when the number of the defective pixels and the number of the noise pixels do not satisfy the tolerance conditions.

[0090] If the image inspection unit 8c determines that the output image G1 is normal, it shifts the process to step S106, and if it determines that the output image G1 is abnormal, it shifts the process to step S107.

[0091] When the default page number is 1, the simplified inspection process is performed on the second read image data for each page of the print process. On the other hand, when the default page number is 2 or more, the simplified inspection process is performed on the second read image data sampled for each multiple pages of the print process.

[0092] <Process S106> In step S106, the image inspection unit 8c selects the next process depending on whether the continuous printing process has been completed or not.

[0093] If the continuous print process is not completed, the image inspection unit 8c shifts the process to step S101, whereby the processes subsequent to step S101 corresponding to the print process of a new page are executed.

[0094] On the other hand, when the continuous print process is completed, the image inspection unit 8c ends the image inspection process.

[0095] <Process S107> In step S107, the print control unit 8b interrupts the continuous print process in the printing device 5 and the sheet conveying device 2. After executing the process of step S107, the print control unit 8b shifts the process to step S108.

[0096] <Process S108> In step S108, the image inspection unit 8c and the print control unit 8b execute error processing, which will be described later.

[0097] After the error processing is executed, the image inspection unit 8c shifts the process to step S109.

[0098] <Process S108> In step S108, the print control unit 8b releases the interruption of the continuous printing process, so that the interrupted continuous printing process is continued.

[0099] That is, when the interruption of the continuous printing process is released, the print control section 8b causes the sheet transport device 2 and the printing device 5 to continue the continuous printing process.

[0100] After executing the process of step S108, the print control unit 8b shifts the process to step S106. As a result, the processes from step S101 onwards are executed every time the print process of a new page is executed until the continuous print process is completed.

[0101] [Error handling] Next, an example of the procedure for the error processing will be described with reference to the flowchart shown in FIG.

[0102] In the following description, S201, S202, ... represent identification codes of a plurality of steps in the error processing. In the error processing, the processing of step S201 is executed first.

[0103] <Process S201> In step S201, the image inspection unit 8c acquires target image data, which is part of the data recorded in the secondary storage device 83 of the image forming apparatus 10 or the secondary storage device 72 of the management apparatus 7.

[0104] The target image data is the first read image data corresponding to the second read image data for one page in which an abnormality in the output image G1 has been detected by the simplified inspection process in step S105.

[0105] The target image data may be the first read image data for a plurality of pages corresponding to the second read image data for a plurality of pages including a page in which an abnormality is detected in the output image G1.

[0106] After executing the process of step S201, the image inspection unit 8c shifts the process to step S202.

[0107] <Process S202> In step S202, the image inspection unit 8c executes a detailed inspection process based on the target image data.

[0108] The detailed inspection process is a process for inspecting the quality of the output image G1 by comparing the target image data with reference image data corresponding to the output image G1.

[0109] The reference image data is data that represents an output image G1 to be formed on a sheet 9. For example, the reference image data is data that represents the output image G1 at the same resolution as the resolution of the first image sensor 3a.

[0110] Specifically, in the detailed inspection process, the image inspection unit 8c detects the defective pixels and the noise pixels in the first read image data and counts the number of the defective pixels and the noise pixels. In this case, the image inspection unit 8c detects the defective pixels and the noise pixels by comparing the reference image data with the first read image data.

[0111] Furthermore, the image inspection unit 8c derives a pixel density difference, which is a difference between the density of each pixel in the first read image data and the density of each pixel in the reference image data, and further derives a representative value of the pixel density differences for a plurality of pixels for one page as a density evaluation value.

[0112] For example, the density evaluation value is an average value or a mode value of the pixel density differences corresponding to a plurality of images for one page.

[0113] In the above example, the number of defective pixels, the number of noise pixels, and the density evaluation value are each an example of an index value of the quality of the output image G1.

[0114] After executing the process of step S202, the image inspection unit 8c shifts the process to step S203.

[0115] <Process S203> In step S203, the image inspection unit 8c executes a result notification process for notifying the inspection results, which are the results of the simple inspection and the detailed inspection.

[0116] For example, the result notification process includes a process of notifying the test result through the human interface device 800. Alternatively, the result notification process may include a process of notifying the management device 7 of the test result through the communication device 85.

[0117] In this embodiment, the result notification process includes an inquiry process for inquiring whether to re-execute the detailed inspection process or to release the interruption of the continuous printing process.

[0118] For example, the image inspection unit 8c executes the inquiry process through the human interface device 800 of the image forming apparatus 10.

[0119] Moreover, the image inspection unit 8c may execute the inquiry process for the management device 7 by transmitting inquiry information to the management device 7 through the communication device 85.

[0120] The administrator checks the notification information from the inquiry process and then performs an adjustment selected from a plurality of adjustment candidates. For example, the plurality of adjustment candidates include performing an operation on the operation device 801 to cause the image forming apparatus 10 to execute various adjustment processes such as a head cleaning process or a print density correction process.

[0121] Furthermore, the plurality of adjustment suggestions include cleaning of the sheet transport device 2 or the transport path 200.

[0122] After executing the process of step S203, the image inspection unit 8c shifts the process to step S204.

[0123] <Process S204> In step S204, the image inspection unit 8c selects the next process depending on whether or not a reexamination instruction has been input in response to the inquiry process. The reexamination instruction is an instruction requesting re-execution of the detailed inspection process.

[0124] Usually, the manager performs an operation corresponding to the re-examination instruction on the human interface device 800 of the image forming apparatus 10 or the human interface device 74 of the management apparatus 7 after carrying out the adjustment measures.

[0125] The image inspection unit 8c shifts the process to step S205 if the reexamination instruction has not been input, and shifts the process to step S206 if the reexamination instruction has been input.

[0126] <Process S205> In step S205, the image inspection unit 8c selects the next process depending on whether or not a release instruction has been input in response to the inquiry process. The release instruction is an instruction requesting release of the interruption of the continuous print process.

[0127] When the administrator visually determines that the image quality of the output image G1 is acceptable, the administrator performs an operation corresponding to the release instruction on the human interface device 800 of the image forming apparatus 10 or the human interface device 74 of the management device 7 .

[0128] If the release instruction is not input, the image inspection unit 8c shifts the process to step S204. As a result, the image inspection unit 8c repeats the processes of step S204 and step S205 until the re-examination instruction or the release instruction is input.

[0129] On the other hand, when the release instruction is input, the image inspection unit 8c ends the error processing, whereby the interruption of the continuous printing process is released (see step S109 in FIG. 4).

[0130] <Process S206> In step S206, the print control unit 8b causes the sheet conveying device 2 and the printing device 5 to execute the print process for the page corresponding to the target image data.

[0131] The print control unit 8b executes the process of step S206 and then shifts the process to step S207.

[0132] <Process S207> In step S207, the image inspection unit 8c causes the first image sensor 3a to execute a process of reading an image from the sheet 9 on which the output image G1 has been formed by the print process in step S206.

[0133] After executing the process of step S207, the image inspection unit 8c shifts the process to step S208.

[0134] <Process S208> In step S208, the image inspection unit 8c records the first read image data obtained by the first image sensor 3a in step S207 in the secondary storage device 83 or the secondary storage device 72, similarly to step S103.

[0135] After executing the process of step S208, the image inspection unit 8c shifts the process to step S202. In step S202 after step S208, the image inspection unit 8c processes the first read image data obtained by the first image sensor 3a in step S207 as the target image data.

[0136] As described above, the image inspection unit 8c executes the processes of steps S103 and S202 on the first read image data obtained by the first image sensor 3a. The processes of steps S103 and S202 are each an example of first data processing on the first read image data.

[0137] The image inspection unit 8c is an example of an image data processing unit that processes the first read image data and the second read image data.

[0138] In step S103, the image inspection unit 8c sequentially records the first read image data for each page of the sheet 9 in the secondary storage device 83 or the secondary storage device 72 in parallel with the continuous print process.

[0139] Furthermore, the image inspection unit 8c executes a process of step S105 on the second read image data obtained by the second image sensor 3b. The process of step S105 is an example of a second data process on the second read image data. The process of step S105 is different from the processes of steps S103 and S202.

[0140] In step S105, the image inspection unit 8c executes the simplified inspection process in parallel with the continuous printing process. The simplified inspection process is an example of a process for inspecting the quality of the output image G1 by comparing the second read image data with the reference image data corresponding to the output image G1.

[0141] The second read image data to be subjected to the simplified inspection process is the second read image data for each page of the print process or the second read image data sampled for each of a plurality of pages of the print process.

[0142] By recording the first read image data obtained by the first image sensor 3a, a sufficient amount of information is ensured in the read image data for the output image G1.

[0143] Furthermore, the second scanned image data obtained by the second image sensor 3b is used in the simplified inspection process. The second scanned image data has a relatively small amount of information. This allows real-time processing of the second scanned image data for each sheet 9 in parallel with the continuous printing process.

[0144] Furthermore, the print control unit 8b causes the printing device 5 to suspend the continuous printing process when an abnormality is detected in the output image G1 by the simplified inspection process (see step S107 in FIG. 4).

[0145] After the continuous printing process is interrupted, the image inspection unit 8c executes the detailed inspection process in step S202. The detailed inspection process is an example of a process for inspecting the quality of the output image G1 by comparing the target image data with the reference image data.

[0146] The simplified inspection process screens the output image G1 for the presence or absence of an abnormality. If there is a possibility that an abnormality has occurred in the output image G1, the continuous print process is interrupted and the detailed inspection process is performed based on the first read image data.

[0147] Therefore, it is possible to avoid the continuous printing process being executed unnecessarily under the circumstances where an abnormality occurs in the output image G1. Also, by executing the detailed inspection process, the manager can grasp the more detailed condition of the output image G1.

[0148] By employing the image forming apparatus 10, it is possible to ensure the amount of information regarding the read image data obtained by the image sensor 3 while also achieving real-time processing. [Explanation of symbols]

[0149] 2: Sheet transport device 3: Image sensor 3a: 1st image sensor 3b: Second image sensor 4: White reference material 5: Printing device 7: Management device 8: Control device 10: Image forming device 74: Human interface devices 200: Transport path 800: Human interface devices D1: Sheet transport direction D2: Width direction G1: Output image

Claims

1. a printing device that executes a printing process for forming an image on a sheet transported along a transport path; a first image sensor disposed downstream of the printing device in a sheet conveying direction and configured to read an output image formed on the sheet; a second image sensor disposed downstream of the printing device in the sheet conveying direction and configured to read the output image at a resolution lower than that of the first image sensor; An image forming apparatus comprising: an image data processing unit that performs first data processing on first read image data obtained by the first image sensor and second data processing, different from the first data processing, on second read image data obtained by the second image sensor.

2. the image data processing unit executes, as the first data processing, a process of sequentially recording the first read image data for each page of the sheet in a secondary storage device in parallel with a continuous print processing which is a continuous repetition of the print processing; The image forming apparatus of claim 1, further comprising: an image data processing unit that, in parallel with the continuous printing process, executes as the second data processing a simple inspection process for inspecting the quality of the output image by comparing the second read image data for each printing process for one page or the second read image data sampled for each printing process for multiple pages with reference image data corresponding to the output image.

3. a print control unit that causes the printing device to suspend the continuous printing process when an abnormality in the output image is detected by the simplified inspection process; The image forming apparatus of claim 2, wherein the image data processing unit executes as the first data processing a detailed inspection process to inspect the quality of the output image by comparing the first read image data corresponding to the second read image data in which an abnormality in the output image was detected by the simple inspection process with reference image data corresponding to the output image after the continuous printing process is interrupted.

Images