Image forming system

Abstract

To provide an image inspection system which can execute an image inspection more appropriately than a conventional technique.SOLUTION: An image formation unit forms a first image on a first surface of a first sheet on which a second image is formed previously. A reading unit is provided on the downstream with respect to the image formation unit in the conveyance direction in which the first sheet is conveyed and reads an image of the first sheet that is conveyed. At least one processor generates reference data on the basis of a result of reading an image by the reading unit on the first surface of the first sheet on which a first image is not formed, generates first image data that represents a result of reading an image by the reading unit on the first surface of the first sheet on which the first image is formed on the first surface by the image formation unit, and determines, on the basis of the reference data and the first image data, a relative position between the first image and the second image on the first surface of the first sheet on which the first image is formed.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to an image forming system.

Background Art

[0002] In recent years, there has been a demand for inspecting the quality of an image formed on a sheet. According to Patent Document 1, it has been proposed to print another image on a sheet (preprinted sheet) on which an image has been printed in advance, and inspect the print quality of the other image. In Patent Document 1, reference data is created by reading a preprinted sheet with an image sensor in advance. Then, another image is additionally formed on the preprinted sheet and read with an image sensor, thereby creating inspection data. Finally, the print quality is determined based on the reference data and the inspection data.

Prior Art Documents

Patent Documents

[0003]

Patent Document

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in Patent Document 1, a mask is applied to the area where the image is preprinted, and the print quality is determined for the area of the sheet excluding the masked area over the entire area of the sheet. That is, in Patent Document 1, the relative positions of the image preprinted on the sheet and the image additionally printed on the sheet are not considered. Thus, in Patent Document 1, even when the image preprinted on the sheet and the image additionally printed on the sheet are not in an appropriate positional relationship, the inspection result may be judged as passing. Therefore, an object of the present invention is to provide an image inspection system capable of performing image inspection more appropriately than in the past.

Means for Solving the Problems

[0005] The present invention, for example, An image forming unit that forms a first image on the first surface of a first sheet, wherein a second image is already formed on the first surface of the first sheet; A reading unit is provided downstream of the image forming unit in the transport direction in which the first sheet is transported, and reads the image of the first sheet as it is being transported. It has at least one processor, and the at least one processor is Based on the result of the reading unit reading the image of the first surface of the first sheet on which the first image is not formed, reference data is generated. The reading unit generates first image data representing the result of reading the image of the first surface of the first sheet on which the first image has been formed by the image forming unit. The present invention provides an image forming system that determines the relative positions of the first image and the second image on the first surface of the first sheet on which the first image is formed, based on the reference data and the first image data. [Effects of the Invention]

[0006] According to the present invention, an image inspection system is provided that can perform image inspection more appropriately than conventional systems. [Brief explanation of the drawing]

[0007] [Figure 1] A diagram illustrating an image inspection system. [Figure 2] A diagram illustrating the control device. [Figure 3] A diagram illustrating an imaging inspection device. [Figure 4] A diagram illustrating edge enhancement processing. [Figure 5] Diagram explaining the binarization process [Figure 6] A diagram illustrating the process of determining the character area. [Figure 7] A diagram illustrating the settings screen. [Figure 8] A diagram explaining imaging examinations. [Figure 9] A flowchart illustrating the image inspection method. [Figure 10] Flowchart showing image inspection method [Figure 11] A diagram illustrating an image inspection system. [Modes for carrying out the invention]

[0008] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0009] [Image Forming System] The image forming system 100 in this embodiment will be described below. As shown in Figure 1, the image inspection system (image forming system) 100 includes an operating unit 20, an image forming apparatus 30, a control device 40, an image inspection apparatus 50, a loading device 60, and a post-processing device 70.

[0010] The operation unit 20 includes a display device that outputs information to the user and an input device (e.g., a touch panel sensor) that receives instructions from the user.

[0011] The image forming apparatus 30 forms a toner image on the sheet P according to the YMCK color signal supplied from the control device 40. The letters YMCK assigned to the reference code indicate the toner colors: yellow, magenta, cyan, and black. When explaining matters common to the four colors, the letters YMCK are omitted from the reference code.

[0012] The photoreceptor 1 is an image carrier that carries an electrostatic latent image and a toner image. The charger 2 uniformly charges the surface of the photoreceptor 1. The exposure device 3 irradiates the photoreceptor 1Y with laser light corresponding to a color signal supplied from the control device 40 to form an electrostatic latent image on the surface of the photoreceptor 1. The developing device 4 develops the electrostatic latent image using toner to form a toner image on the surface of the photoreceptor 1. The primary transfer roller 5Y transfers the toner image formed on the surface of the photoreceptor 1 from the photoreceptor 1 to the intermediate transfer belt 6. Here, each toner image of YMCK is superimposed to form a color image. The intermediate transfer belt 6 conveys the toner image to the secondary transfer unit 7.

[0013] The sheet cassette 11 is a storage for accommodating a large number of sheets P. Here, the sheet P accommodated in the sheet cassette 11 may be a preprinted sheet as the first sheet. A preprinted sheet is a sheet on which an image has been previously formed by an image forming apparatus 30 or another image forming apparatus. Representative preprinted sheets are, for example, invoices and delivery notes. Hereinafter, the case where the sheet P accommodated in the sheet cassette 11 is a preprinted sheet will be described.

[0014] The conveyance roller 12 feeds the sheet P accommodated in the sheet cassette 11 and conveys the sheet P along the conveyance path.

[0015] The secondary transfer unit 7 transfers the toner image from the intermediate transfer belt 6 to the sheet P. The fixing device 8 applies heat and pressure to the sheet P and the toner image to fix the toner image on the sheet P. The discharge roller 17 discharges the sheet P to the image inspection device 50.

[0016] The image inspection device 50 is a device for inspecting the quality of the image formed on the sheet P. The inspection controller 51 reads the sheet P using the image sensors 52a and 52b while conveying the sheet P with the conveyance roller 53. The image sensors 52a and 52b include a light source for illuminating the sheet P and a CMOS sensor. The inspection controller 51 generates image data corresponding to the result of the image sensors 52a and 52b reading the sheet P.

[0017] The loading device 60 transports the sheets P discharged from the image inspection device 50 using transport rollers 63. The loading device 60 has an NG tray 62 and a large-capacity tray 61. For example, sheets P whose image quality has been determined to be unacceptable by the image inspection device 50 are loaded onto the NG tray 62. The control device 40 controls the image forming device 30 to form the image formed on the sheet P determined to be NG (unacceptable) by the image inspection device 50 onto a new sheet P (reprint). The control device 40 may also notify the user of the NG (unacceptable) determination by the image inspection device 50 by displaying it on the display device 21.

[0018] The large-capacity tray 61 is a sheet loading unit capable of loading a large number of sheets P. The loading device 60 has flappers 64a and 64b that switch the destination of the sheets P. The control device 40 controls the flappers 64a and 64b based on the print job and image inspection results. The control device 40 may also control the flappers 64a and 64b to output the sheets P to the post-processing device 70.

[0019] The post-processing device 70 transports the sheets P using a plurality of transport rollers 73. The post-processing device 70 has an upper tray 74a, a middle tray 74b, and a lower tray 74c as output trays. The control device 40 controls the flappers 72a and 72b to discharge the sheets P into one of the upper tray 74a, the middle tray 74b, or the lower tray 74c. The post-processing device 70 may also include a binding machine that bundles the sheets P discharged from the loading device 60 to create sheet bundles and staples the sheet bundles together. The post-processing device 70 may also include a bookbinding machine that folds the sheet bundles in half. The post-processing device 70 may also include a cutting machine that cuts the sheet bundles.

[0020] In this embodiment, sheets P that are judged to be acceptable by the image inspection device 50 are loaded onto a large-capacity tray 61 or bundled into sheets by the post-processing device 70. Conventionally, if one sheet P in a sheet bundle consisting of several hundred sheets P is deemed unacceptable, the entire sheet bundle is discarded. However, in this embodiment, the unacceptable sheet P is removed from the sheet bundle, so the sheet bundle is not wasted. In other words, this embodiment contributes to the effective use of resources.

[0021] Next, the control configuration in the image forming system 100 will be described. Figure 2 shows details of the control device 40. The CPU 201 implements multiple functions by executing a control program 213 stored in the memory 210. The CPU 201 may have multiple processors or CPU cores. Some or all of the multiple functions implemented by the CPU 201 may be implemented by hardware circuits different from the CPU 201. The memory 210 is a storage device that includes ROM (read-only memory), RAM (random access memory), SSD (solid state drive), and HDD (hard disk drive).

[0022] Figure 3 shows details of the test controller 51. The CPU 301 implements multiple functions by executing a control program 313 stored in the memory 310. Some or all of these functions may be implemented by hardware circuits. The memory 310 is a storage device including ROM, RAM, SSD, and HDD.

[0023] The UI display unit 203 of the setting unit 202 displays the user interface (UI) necessary for setting up the image inspection on the display device 21 of the operation unit 20. The reception unit 204 of the setting unit 202 receives operations and instructions for the user interface from the input device 22.

[0024] <Generating reference data> The method for generating reference data 211, which serves as the reference image when inspecting images, is explained below.

[0025] When an instruction to generate reference data 211 is input to the control device 40 via the display device 21, the control device 40 controls the image forming apparatus 30 to transport the sheet P, which is a preprinted sheet housed in the sheet cassette 11. When the image forming apparatus 30 transports the sheet P to generate reference data 211, it does not form an additional image on the sheet P that is to be formed by the image forming apparatus 30 as a first image in the inspection job described later.

[0026] Furthermore, when an instruction to generate reference data 211 is input to the control device 40 via the display device 21, the control device 40 controls the image inspection device 50 to read the image of the sheet P being transported from the image forming apparatus 30.

[0027] The inspection controller 51 generates reference data 211 based on image data representing the results read by image sensors 52a and 52b of the sheet P that has been transported by the image forming apparatus 30 without an image being formed on it, and stores it in the memory 310. Alternatively, the inspection controller 51 may generate reference data 211 based on the average value of the image data (pixel values) of multiple sheets P read by image sensors 52a and 52b.

[0028] The control device 40 receives reference data 211 from the inspection controller 51 and stores it in the memory 210. The UI display unit 203 may display the image represented by the reference data 211 on the display device 21.

[0029] <Image inspection> Next, a method for inspecting images based on reference data 211 will be described. In this embodiment, the inspection job is started after the reference data 211 is generated (i.e., additional images are formed on the sheet P loaded in the sheet cassette 11), but this is not limited to this embodiment.

[0030] The control device 40 stores the inspection setting data 212, which is information about the image inspection set by the user via the display device 21, in the memory 210. The control device 40 then transfers the inspection setting data 212 to the image inspection device 50. The inspection setting data 212 will be described later.

[0031] When an instruction to start an inspection job to form an image on sheet P and inspect the formed image is input to the control device 40 via the display device 21, the control device 40 controls various devices such as the image forming apparatus 30, the loading apparatus 60, and the post-processing apparatus 70.

[0032] Specifically, the control device 40 controls the image forming apparatus 30 to transport the sheet P, which is a preprinted sheet stored in the sheet cassette 11. The control device 40 also controls the image forming apparatus 30 to print an image on the sheet P that corresponds to image data input from an external device such as a PC or tablet.

[0033] The transport control unit 306, located in the inspection controller 51, drives the motor M2 to rotate the transport roller 53. The reading control unit 307, also located in the inspection controller 51, controls the image sensors 52a and 52b to read the sheet P and generate image data. Image sensor 52a reads the first surface of the sheet P, and image sensor 52b reads the second surface of the sheet P, which is opposite to the first surface. As a result, this embodiment can perform image inspection on both sides of the sheet P.

[0034] The loading device 60 drives the motor M1 to rotate the transport roller 63 according to a control command from the control device 40. The loading device 60 drives the solenoids 65a and 65b according to a control command from the control device 40 to switch the flappers 64a and 64b. As a result, the sheet P is guided and transported to either the NG tray 62, the large capacity tray 61, or the post-processing device 70. For example, if the image inspection result from the image inspection device 50 is NG, the control device 40 controls the loading device 60 to discharge the sheet P determined to be NG to the NG tray 62. The image forming apparatus 30 and the post-processing device 70 also include solenoids to drive the flappers and motors to drive the transport rollers.

[0035] {Position correction unit} The position correction unit 303 of the inspection unit 302 performs position correction on the reading results of the image sensors 52a and 52b. If the sheet P is read by the image sensors 52a and 52b while it is skewed, the sheet P may appear slanted in the read image. Also, the leading edge of the sheet P may be shifted from its ideal position in the read image. Therefore, the position correction unit 303 corrects the position of the read image by rotating the read image or by shifting the position of the read image so that the leading edge of the sheet P in the read image matches the ideal position.

[0036] {Overlap detection unit} The overlap determination unit 304 determines, based on the reference data 211 and the inspection image data 312, which is image data corrected by the position correction unit 303, whether a pre-printed image, which is a second image printed on the sheet P before the image is formed on the sheet P by the image forming apparatus 30 in the inspection job, and an image formed on the sheet P by the image forming apparatus 30 in the inspection job (hereinafter referred to as the additional image) overlap. For example, it determines whether the characters as an additional image overlap the lines and characters as a pre-printed image. Specifically, the overlap determination unit 304 calculates the difference between the pixel value (luminance value) in the reference data 211 and the pixel value in the inspection image data 312, and determines the overlap based on the difference. More specifically, the overlap determination unit 304 determines that the characters as an additional image overlap the lines and characters as a pre-printed image if the difference between the pixel value in the reference data 211 and the pixel value in the inspection image data 312 is greater than or equal to a first predetermined value. Furthermore, the overlap determination unit 304 determines that the characters in the additional image do not overlap the lines and characters in the pre-printed image if the difference between the pixel values ​​in the reference data 211 and the pixel values ​​in the inspection image data 312 is less than a first predetermined value. This utilizes the characteristic that the pixel values ​​of the parts where the characters in the additional image overlap the lines and characters in the pre-printed image are lower than the pixel values ​​of the parts where the characters in the additional image do not overlap the lines and characters in the pre-printed image.

[0037] {Misalignment detection unit} If the characters in the additional image do not overlap with the lines and characters in the pre-printed image, the misalignment determination unit 305 determines whether the area of ​​the characters in the additional image is misaligned by a predetermined amount or more relative to the lines and characters in the pre-printed image. Specifically, for example, the misalignment determination unit 305 calculates the distance between the lines in the pre-printed image and the area of ​​the characters in the additional image, and determines that the area of ​​the characters in the additional image is misaligned with the lines and characters in the pre-printed image if the distance exceeds a second predetermined value. Also, if the distance between the lines in the pre-printed image and the area of ​​the characters in the additional image does not exceed a second predetermined value, the misalignment determination unit 305 determines that the area of ​​the characters in the additional image is not misaligned with the lines and characters in the pre-printed image. Note that if the distance is within a predetermined range, the misalignment may be determined to be acceptable. If the distance deviates from the predetermined range, the misalignment may be determined to be unacceptable.

[0038] The method by which the misalignment detection unit 305 detects the character area is described below.

[0039] The misalignment detection unit 305 calculates the average brightness value within a predetermined area (for example, an area of ​​7 pixels in the X direction and 7 pixels in the Y direction) based on the brightness values ​​contained in the image data. The coordinate of the pixel of interest in the main scanning direction, which is the direction in which the light-receiving elements of the image sensors 52a and 52b are arranged, is defined as X. The coordinate of the pixel of interest in the sub-scanning direction, which corresponds to the transport direction in which the sheet P is transported, is defined as Y. When three pixels before and three pixels after the pixel of interest are referenced in both the main scanning direction and the sub-scanning direction, the average brightness value AVE2 is calculated based on the following formula.

[0040]

number

[0041] The misalignment detection unit 305 performs edge enhancement processing on the acquired image data in order to detect character areas and halftone areas from the acquired image data. When a 7x7 filter coefficient K is multiplied by the three pixels before and after the pixel of interest in both the main scanning direction and the sub-scanning direction, the brightness value EDGE of the image data after edge enhancement is calculated based on the following formula.

[0042]

number

[0043] Figures 4A to 4C illustrate the edge enhancement process. Figure 4A shows an image obtained from read data where the background brightness value is "200", the diagonal line brightness value is "150", and the isolated point brightness value is "190". The image size is 10x10 pixels. Figure 4B shows an edge enhancement filter with a size of 5x5 pixels. Figure 4C shows the brightness values ​​of the image data after convolution processing based on the edge enhancement filter. Values ​​less than or equal to 0 after convolution processing are clipped to "0". Values ​​greater than or equal to 255 after convolution processing are clipped to "255".

[0044] The data read after the convolution operation (Figure 4C) shows that the brightness value of the diagonal lines is "255," indicating edge enhancement. The brightness value of the background is "0" due to edge enhancement. This is how the edges are extracted. Isolated points with a small brightness difference from the background brightness value are not significantly enhanced after edge enhancement, and their brightness value becomes "80."

[0045] The misalignment detection unit 305 compares the difference between the average brightness value AVE2 and the brightness value EDGE with the threshold THedge. The misalignment detection unit 305 outputs a binarized data BIN of "1" if the difference is less than or equal to the threshold THedge. The misalignment detection unit 305 outputs a binarized data BIN of "0" if the difference is greater than the threshold THedge. Through this binarization process, information that is clearly printed on the original, such as characters, and dots in halftone printing are emphasized and extracted. The misalignment detection unit 305 performs binarization determination using the following formula.

[0046]

number

[0047]

number

[0048] In the example shown in Figure 4C, a binarization process is performed where the threshold THedge is set to "100", pixels with a difference of 100 or more are set to "0", and pixels with a difference of 99 or less are set to "1". As a result, only pixels with diagonal lines become BIN=1, making it possible to extract diagonal lines.

[0049] The misalignment detection unit 305 detects groups of pixels that are isolated, such as halftone dots formed on sheet P, where there are no surrounding pixels with BIN=1. The misalignment detection unit 305 prepares a pattern matching image in advance, which is based on the image when the halftone dots are read, and detects the region where an image matching this pattern matching image is found as an isolated group of pixels. The misalignment detection unit 305 converts the value of the BIN of the binarized data of the detected group of pixels from "1" to "0". Through this process, the halftone dot portion can be removed from the binarized data.

[0050] Figure 5A shows an example of a binarized data BIN. In particular, Figure 5A illustrates a binarized data BIN that includes the letter "A" and a halftone area with a 2x2 dot pattern. Figure 5B illustrates a pattern matching image that detects the 2x2 dot pattern. Figure 5C illustrates the binarized data after the halftone area has been removed.

[0051] The binarized data BIN shown in Figure 5A contains two regions that match the pattern matching image (the regions enclosed by the thick border in Figure 5A). By converting the binarized data BIN in these regions from "1" to "0", the binarized data shown in Figure 5C is obtained.

[0052] In this example, the 2x2 dot area has been removed, leaving the letter "A," indicating that the halftone area has been excluded and only the letter area has been extracted. As shown in Figure 5C, the misalignment detection unit 305 determines that pixels set to "1" in the binarized data DOT from which the halftone area has been excluded are the letter area.

[0053] The misalignment detection unit 305 divides the image read by the image sensor into predetermined sizes (for example, a rectangular size of 32x32 pixels), performs area mapping, and detects the character regions. Figures 6A to 6C are explanatory diagrams of the process for determining the character regions.

[0054] The misalignment detection unit 305 determines for each mapped area whether or not it contains a pixel whose binarized data DOT is "1". The misalignment detection unit 305 determines that an area containing a pixel whose binarized data DOT is "1" is an area containing "characters". In the example in Figure 6B, the character "A" is printed within the range of Area 11, Area 12, Area 21, and Area 22. Since this area contains a pixel whose binarized data DOT is "1", it is determined that there are characters in the area enclosed by the thick border.

[0055] The method for determining the character region is not limited to the method described above. For example, a method using a pre-trained model to determine the character region may also be used.

[0056] {Setting the test content} Figure 7A shows an example of the print settings screen 400. Figure 7B shows an example of the inspection settings UI 410. The CPU 201 displays the print settings screen 400 on the display device 21 according to the control program 213. The term "inspection content" may refer to the inspection process (inspection job), or it may refer to the conditions or information that set or define the inspection process.

[0057] The print settings screen 400 has a paper selection button 401. When the paper selection button 401 is pressed, the CPU 201 (reception unit 204) accepts the specification of the sheet cassette from which sheet P will be fed, the sheet size, and the type of sheet (thick paper, plain paper, thin paper, glossy paper).

[0058] When the inspection setting button 402 is pressed, the CPU 201 (UI display unit 203) displays the inspection setting UI 410 shown in Figure 7B on the display device 21.

[0059] When the cancel button 403 is pressed, the CPU 201 (settings unit 202) discards the settings made by the user on the print settings screen 400 and returns to the initial settings screen (not shown).

[0060] When the print start button 404 is pressed, the CPU 201 starts printing without performing image inspection.

[0061] As shown in Figure 7B, the inspection setting UI 410 has an image display area 411 and a detailed setting area 412. The image display area 411 is an area that displays a reference image as an image represented by reference data 211 and accepts the setting of an inspection area as an area to be inspected in the reference image.

[0062] If checkbox 420 is not checked, the image display area 411 displays the image to be formed on sheet P by the image forming apparatus 30. Thus, checkbox 420 is a control object that specifies whether the image displayed in the image display area 411 is a reference image or an image to be formed on sheet P by the image forming apparatus 30.

[0063] The detailed settings area 412 becomes operable when checkbox 420 is checked, displaying a screen for setting the inspection details and accepting the settings for the inspection details (conditions).

[0064] The setting area 413a has an area setting button 414a and a content specification menu 415a. The area setting button 414a displays the name of the inspection area (judgment area). To the left of the area setting button 414a, it is suggested that the first inspection area 421a is displayed by a dashed line. When the area setting button 414a is pressed, the CPU 201 (reception unit 204) accepts the specification of the first inspection area 421a entered by the user in the image display area 411. For example, the CPU 201 (reception unit 204) sets the area touched by the user with their finger or stylus in the image display area 411 as the inspection area. For example, the CPU 201 (reception unit 204) sets a coordinate system with the upper left corner of the reference image as the origin and stores the coordinates of the first inspection area 421a specified by the user in the inspection setting data 212. The CPU 201 (UI display unit 203) may highlight the inspection area set by the user. Highlighting includes enclosing the inspection area in a frame or displaying the inspection area as a strip. The content selection menu 415a displays candidate inspection content and accepts the user's selection of inspection content. The CPU 201 (reception unit 204) stores the selected inspection content from the content selection menu 415a in the inspection setting data 212. When the add button 416a is pressed, the CPU 201 (UI display unit 203, reception unit 204) additionally displays a second content selection menu 415a and accepts the selection of additional inspection content.

[0065] Setting areas 413b and 413c accept inspection settings in the same way as setting area 413a. Setting area 413b has an area setting button 414b for accepting settings for the second inspection area 421b and a content specification menu 415b. In this example, the add button 416b has already been pressed, and two inspection contents have been set. To the left of the area setting button 414b, it is indicated that the second inspection area 421b will be displayed by a dashed line. The second inspection area 421b is displayed by a dashed line in the image display area 411.

[0066] The setting area 413c has an area setting button 414c for accepting the third inspection area 421c, a content specification menu 415c, and an add button 416c. To the left of the area setting button 414c, it is suggested that the third inspection area 421c will be displayed by a dashed line. The image display area 411 displays the third inspection area 421c by a dashed line.

[0067] The add button 417 is used to add a setting area 413. For example, in the default state, only setting area 413a is displayed. If the add button 417 is pressed in this state, the CPU 201 (UI display unit 203) adds and displays setting area 413b. If the add button 417 is pressed again in this state, the CPU 201 (UI display unit 203) adds and displays setting area 413c.

[0068] When the back button 419 is pressed, the CPU 201 (UI display unit 203) returns to the print settings screen 400. When the start inspection print button 418 is pressed, the CPU 201 starts an inspection job that forms an image on sheet P and inspects the image formed on sheet P.

[0069] Among the inspection items, "overlap with lines and text" refers to checking for overlap between the additional image and the lines and text included in the pre-printed image. "misalignment with lines" refers to checking for misalignment between the additional image and the lines included in the pre-printed image. "Exclusion from inspection" means that the inspection will not be performed in the corresponding inspection area.

[0070] Here, three setting areas 413a to 413c are displayed, and their display order may correspond to the priority in image inspection. That is, the inspection content set in the top-displayed setting area 413a is executed with higher priority than the inspection content set in the second-displayed setting area 413b. The inspection content set in the second-displayed setting area 413b is executed with higher priority than the inspection content set in the third-displayed setting area 413c. In the example shown in Figure 7B, the entire image to be inspected is set as an inspection exclusion area in setting area 413c. The inspection areas of setting areas 413a and 413b are set within the inspection exclusion area. Since setting areas 413a and 413b have higher priority than setting area 413c, the inspection content set in setting areas 413a and 413b is executed.

[0071] Figure 8A shows an example of detecting "overlap with lines and text." The pre-printed image includes text such as "billing amount" and "yen," as well as lines. The added image contains the text "5000." In Figure 8A, in inspection area 501, the text "5000" overlaps with a line. The CPU 201 (overlap detection unit 304) detects the overlap by calculating the difference between the added image and the pre-printed image.

[0072] Figure 8B shows an example of detecting "misalignment with grid lines." The CPU 201 (misalignment detection unit 305) calculates the distance h between the additional image and the pre-printed image. If the distance h exceeds a threshold, the CPU 201 (misalignment detection unit 305) determines that the additional image is misaligned with the pre-printed image.

[0073] Figure 9 shows the image inspection method performed by the CPU 201 of the control device 40.

[0074] In S601, CPU201 (setting unit 202) accepts inspection settings via inspection setting UI410.

[0075] In S602, the CPU 201 (inspection control unit 205) determines whether the inspection job has been instructed to start via the inspection print start button 418 of the inspection setting UI 410. If the inspection job is instructed to start, the CPU 201 proceeds to S603.

[0076] In S603, the CPU 201 (setting unit 202 or inspection control unit 205) transfers the inspection settings (inspection setting data 212) to the inspection controller 51 of the image inspection device 50.

[0077] In S604, the CPU 201 (inspection control unit 205) instructs the CPU 301 of the inspection controller 51 to inspect the image formed on the sheet P.

[0078] In S605, the CPU 201 (inspection control unit 205) receives the inspection results from the CPU 301 of the inspection controller 51.

[0079] In S606, the CPU201 (job processing unit206) distributes sheets P according to the inspection results. If the inspection result is unsatisfactory, it controls the motor M1, solenoids 65a and 65b of the loading device 60 to discharge the sheets P that have been determined to be NG into the NG tray 62.

[0080] Furthermore, if the inspection result is unsatisfactory, the control device 40 may control the image forming apparatus 30 so as to eliminate the cause of the failure. Specifically, for example, if the cause of the failure was the overlap shown in Figure 8A, the control device 40 may control the image forming apparatus 30 to shift the formed image "5000" upwards.

[0081] Furthermore, if the cause of the failure was the misalignment shown in Figure 8B, the control device 40 may control the image forming apparatus 30 to shift the formed image "5000" downwards.

[0082] If the inspection result is satisfactory, the motor M1 and solenoids 65a and 65b of the loading device 60 are controlled to discharge the sheet P that has been determined to pass into the large capacity tray 61 or the post-processing device 70.

[0083] Figure 10 shows the image inspection method performed by the CPU 301 of the image inspection device 50. When the CPU 301 is instructed or commanded by the control device 40 to execute an inspection job, it starts the following process.

[0084] In S701, the CPU 301 (inspection unit 302) receives inspection settings (inspection setting data 212) from the control device 40 and stores the inspection settings in the memory 310.

[0085] In S702, the CPU 301 (inspection unit 302) performs inspection according to the inspection settings. The inspection unit 302 performs image inspection in the inspection area specified by the inspection setting data 212, according to the inspection content specified by the inspection setting data 212. For example, the inspection unit 302 performs image inspection of sheet P by comparing reference data 211 obtained from a preprint sheet that does not contain additional images with inspection image data 312 obtained from sheet P. The reference data 211 may be part of the inspection setting data 212.

[0086] In S703, CPU301 (inspection unit 302) sends the inspection results to CPU201. When printing and image inspection are performed consecutively on multiple sheets P, CPU301 repeatedly executes S702 and S703.

[0087] As described above, in this embodiment, reference data 211 is generated based on first image data obtained by reading the first surface of sheet P on which a pre-printed image as a second image is formed and an additional image as a first image is not formed. The CPU 301 detects the relative position of the first image and the second image on the first surface of sheet P on which the first image is formed, based on the second image data obtained by reading the first surface of sheet P on which a pre-printed image as a second image is formed and an additional image as a first image is formed on the first surface, and the image data corresponding to the reference data 211. Note that detecting the relative position may, for example, be by detecting the overlap between the first image and the second image, and / or by detecting the displacement of the first image relative to the second image. With this configuration, the relative position of the image pre-printed on sheet P and the image additionally printed on sheet P can be detected (inspected). In other words, it will be possible to prevent the inspection result from being incorrectly determined to be a pass when the pre-printed image on sheet P and the additionally printed image on sheet P are not in the correct positional relationship. That is, image inspection will be able to be performed more appropriately than before.

[0088] Furthermore, in this embodiment, the image inspection system 100 sets an inspection area on a part of the preprinted sheet and performs image inspection on that inspection area. With this configuration, it becomes possible to detect (inspect) the relative positions of the image preprinted on sheet P and the image additionally printed on sheet P. In other words, it is possible to suppress the case where the inspection result is incorrect when the preprinted image on sheet P and the image additionally printed on sheet P are not in the appropriate positional relationship. That is, image inspection is performed more appropriately than before. In addition, according to this embodiment, since image inspection is not performed outside the inspection area, false detections are reduced and the good product rate of printed output is improved.

[0089] In this embodiment, the control device 40 performs inspection settings and sheet P allocation, and the image inspection device 50 performs image inspection. However, this is only one example. The functions of the control device 40 may be incorporated into the controller of the image inspection device 50 or the image forming apparatus 30.

[0090] Furthermore, in this embodiment, when the reference data 211 is generated, the sheet P loaded on the sheet cassette 11 is transported to the image inspection device 50; this is just one example.

[0091] For example, as shown in Figure 11, the sheet P may be transported to the image inspection device 50 from an inserter device 80 provided between the image forming apparatus 30 and the image inspection device 50 in the transport direction in which the sheet P is transported. Specifically, the sheet P loaded on the inserter tray 81 of the inserter device 80 may be transported to the image inspection device 50 by transport rollers 82 and discharge rollers 87. The reference data 211 is generated based on the reading result of the sheet P transported from the inserter tray 81. When an additional image is to be formed on the sheet P, the sheet P is transported from the sheet cassette 11, and the image forming apparatus 30 forms the additional image on the sheet P. The second transport guide 86 that guides the sheet P being transported from the inserter tray 81 to the image inspection device 50 merges with the first transport guide 85 that guides the sheet being transported from the image forming apparatus 30 to the image inspection device 50 in the transport direction between the image forming apparatus 30 and the image inspection device 50.

[0092] <Technical concept derived from the embodiment> [perspective A1] As shown in Figures 1 and 11, the image forming apparatus 30 and the secondary transfer unit 7 are examples of an image forming unit that forms a first image (e.g., an additional image) on the first surface of a first sheet. A second image (e.g., a pre-printed image) is pre-formed on the first surface of the first sheet. The image inspection apparatus 50 and image sensors 52a and 52b are examples of reading units provided downstream of the image forming unit in the transport direction in which the first sheet is transported, and which read the image of the transported first sheet. CPUs 201 and 301 are examples of at least one processor. At least one processor may be configured to generate reference data based on the result of the reading unit reading the image of the first surface of the first sheet on which the first image has not been formed. At least one processor may be configured to generate first image data representing the result of the reading unit reading the image of the first surface of the first sheet on which the first image has been formed by the image forming unit. At least one processor may be configured to determine the relative positions of the first image and the second image on the first surface of the first sheet on which the first image is formed, based on reference data and first image data. Determining the relative positions may include, for example, determining the overlap between the first image and the second image, and / or determining the displacement of the first image relative to the second image. Determining the relative positions may also include determining the relative positional relationship between the position of the first image and the position of the second image.

[0093] [perspective A2] The sheet cassette 11 is an example of a loading section on which the first sheets are loaded. The transport roller 12 is an example of a transport unit that transports the first sheets loaded in the loading section to the image forming unit. A transport belt may be used together with the transport roller 12, or in place of the transport roller 12.

[0094] In some cases, the first sheet may be transported from the loading unit to the reading unit via the image forming unit so that at least one processor can generate reference data. In this case, the image forming unit does not form a first image on the first surface of the first sheet, whose relative position should be detected by at least one processor. On the other hand, in some cases, the first sheet may be transported from the loading unit to the reading unit via the image forming unit so that at least one processor can generate first image data. In this case, the image forming unit forms a first image on the first surface of the first sheet being transported.

[0095] [perspective A3] As shown in Figure 11, the inserter tray 81 is an example of a first loading section provided between the image forming unit and the reading unit in the transport direction, on which the first sheet is loaded. The transport roller 82 is an example of a first transport unit that transports the first sheet loaded in the first loading section to the reading unit. The sheet cassette 11 is an example of a second loading section on which the first sheet is loaded. The transport roller 12 is an example of a second transport unit that transports the first sheet loaded in the second loading section to the image forming unit. The first transport guide 85 is an example of a first transport guide that guides the first sheet being transported from the image forming unit to the reading unit. The second transport guide 86 is an example of a second transport guide that guides the first sheet being transported from the first loading section to the reading unit. As shown in Figure 11, the second transport guide may be provided to merge with the first transport guide at a position between the image forming unit and the reading unit. At least one processor controls the first transport unit so that the first sheet is transported from the first loading unit to the reading unit in order to generate reference data. Furthermore, at least one processor controls the first transport unit so that the first sheet is transported from the second loading unit to the reading unit via the image forming unit in order to generate first image data. The image forming unit forms a first image on the first surface of the first sheet that has been transported from the second loading unit.

[0096] [Perspective A4] The sheet cassette 11 is an example of a first loading section on which the first sheet is loaded. The transport roller 12 is an example of a first transport unit that transports the first sheet loaded in the first loading section to the image forming unit. At least one processor may control the first transport unit so that the first sheet loaded in the first loading section is transported to the image forming unit after the generation of reference data is completed. After the generation of reference data is completed, the image forming unit forms a first image on the first surface of the first sheet transported by the first transport unit.

[0097] [perspective A5] In perspective A4, the first sheet may be transported from the first loading unit to the reading unit via the image forming unit so that at least one processor can generate reference data. In this case, the image forming unit does not form a first image on the first surface of the first sheet, whose relative position should be detected by at least one processor. The first sheet may be transported from the first loading unit to the reading unit via the image forming unit so that at least one processor can generate first image data. In this case, the image forming unit forms a first image on the first surface of the first sheet being transported.

[0098] [perspective A6] In viewpoint A4, the inserter tray 81 is an example of a second loading section provided between the image forming unit and the reading unit in the transport direction, on which the first sheet is loaded. The transport roller 82 is an example of a second transport unit that transports the first sheet loaded in the second loading section to the reading unit. The first transport guide 85 is an example of a first transport guide that guides the first sheet being transported from the image forming unit to the reading unit. The second transport guide 86 is an example of a second transport guide that guides the first sheet being transported from the second loading section to the reading unit. The second transport guide is provided to merge with the first transport guide at a position between the image forming unit and the reading unit. At least one processor controls the second transport unit so that the first sheet is transported from the second loading section to the reading unit in order to generate reference data. At least one processor controls a first transport unit so that a first sheet is transported from a first loading unit to a reading unit via an image forming unit in order to generate first image data. At least one processor causes the image forming unit to form a first image on the first surface of the first sheet that has been transported from the first loading unit.

[0099] [perspectiveA7] At least one processor may generate reference data based on the average value of image data representing the result of a reading unit reading the image of the first face of a first sheet on which the first image has not been formed, and image data obtained by the reading unit reading the face of a second sheet on which the first image has not been formed. Here, the second image has already been formed on the face of the second sheet. In this way, reference data may be created from multiple preprint sheets using statistical methods.

[0100] [perspective A8] The operation unit 20 is an example of an input unit equipped with a display unit (e.g., display device 21) that displays an image corresponding to the reference data. As shown in Figure 7B and others, the input unit may accept the selection of a determination region in the image displayed on the display unit whose relative position should be determined. At least one processor may detect the relative position between the first image and the second image in the determination region on the first surface of the first sheet on which the first image is formed, based on the reference data and the first image data.

[0101] [perspective A9] As shown in Figure 7B and other figures, the display unit may include a first display area that displays an image corresponding to the reference data, and a second display area that displays a screen for receiving settings for the content of the inspection to be performed on the judgment area.

[0102] [perspective A10] The second image may consist of lines or text.

[0103] [perspective A11] At least one processor may determine, based on the reference data and the first image data, whether the first image and the second image overlap as relative positions.

[0104] [perspective A12] At least one processor may calculate the difference between the pixel values ​​of the reference data and the pixel values ​​of the first image data. Based on this difference, at least one processor may determine whether the first image and the second image overlap.

[0105] [perspective A13] At least one processor may determine that the first image and the second image overlap if the difference is greater than or equal to a predetermined value. At least one processor may determine that the first image and the second image do not overlap if the difference is less than a predetermined value.

[0106] [Perspective A14] At least one processor may determine the distance between the first image and the second image as the relative position on the first surface of the first sheet, based on reference data and the first image data. At least one processor may determine whether the determined distance is greater than or equal to a predetermined distance.

[0107] [perspective A15] The NG tray 62 is located downstream of the reading unit in the transport direction and is an example of a first discharge and loading section from which a first sheet is discharged if it is determined that the first image and the second image overlap. The large-capacity tray 61 is located downstream of the reading unit in the transport direction and is an example of a second discharge and loading section from which a first sheet is discharged if it is determined that the first image and the second image do not overlap.

[0108] [perspective A16] The display device 21 is an example of a notification unit that notifies information indicating the result of determining the overlap between the first image and the second image as relative positions.

[0109] [perspective A17] At least one processor may determine the distance between the first image and the second image as a relative position, based on the reference data and the first image data. At least one processor may determine whether the determined distance is greater than or equal to a predetermined distance.

[0110] [Perspective A18] The NG tray 62 is an example of a first discharge tray, located downstream of the reading unit in the transport direction, and is loaded with sheets that have been determined to be at least a predetermined distance away. The large-capacity tray 61 is an example of a second discharge tray, located downstream of the reading unit in the transport direction, and is loaded with sheets that have been determined to be at least a predetermined distance away.

[0111] [Perspective A19] The display device 21 is an example of a notification unit that notifies information indicating whether the determined distance is greater than or equal to a predetermined distance.

[0112] [perspective B1] As shown in Figure 1, the image sensors 52a and 52b are examples of reading units that read a sheet P (e.g., a preprinted sheet) with a pre-formed image and generate image data that becomes reference data 211. The CPU 201 and setting unit 202 are examples of setting units that set an inspection area (e.g., first inspection area 421a) for a part of the image on the sheet P. The image forming apparatus 30 is an example of an image forming unit that forms an additional image on the sheet P. The image inspection apparatus 50 functions as an inspection unit that performs image inspection by focusing on the inspection area set by the setting unit for the inspection data (e.g., inspection image data 312) and the reference data 211. The inspection data is image data generated by having the reading unit read the sheet P with the additional image formed on it. The reference data 211 is image data generated by reading the sheet P with a pre-formed image. Thus, according to this embodiment, an inspection area is set for a part of the image on the sheet P. Therefore, this embodiment can perform image inspection more appropriately than the conventional technology in which the entire image is always considered the inspection area. For example, because the image inspection is performed with focus on the inspection area explicitly set by the user, minor defects located outside the inspection area will not be detected. Also, because the image inspection is performed with focus on the set inspection area, the image inspection will be performed appropriately even if a light-density image is pre-printed across the entire sheet.

[0113] [perspective B2] The display device 21 is an example of a display unit that displays an image of sheet P based on reference data 211. As illustrated in Figure 7B, the CPU 201 (setting unit 202) is configured to accept the setting of the inspection area while the sheet image is displayed on the display unit. Therefore, the user can set the inspection area appropriately or easily.

[0114] [perspective B3] The input device 22 is an example of a touch panel sensor located above the display unit. The CPU 201 (setting unit 202) may set the inspection area in response to the touch input detected by the touch panel sensor. This will allow the user to easily set the inspection area.

[0115] [Perspective B4] The display unit (e.g., display device 21, inspection setting UI 410) may have a first display area (e.g., image display area 411) for displaying an image of sheet P. The display unit (e.g., display device 21, inspection setting UI 410) may also have a second display area (e.g., detailed setting area 412) for displaying a user interface that accepts the specification of inspection content to be performed on the inspection area.

[0116] [perspective B5~B7] The user interface may include an area (e.g., area setting button 414a) that displays identification information for the first inspection area set for the sheet image. Furthermore, the user interface may include an area (e.g., content selection menu 415a) that displays the first inspection content to be performed for the first inspection area in a selectable manner. The user interface may also include an area (e.g., area setting button 414b) that displays identification information for the second inspection area set for the sheet image. Furthermore, the user interface may include an area (e.g., content selection menu 415a) that displays the second inspection content to be performed for the second inspection area in a selectable manner. This will allow the user to easily set multiple inspection areas and their inspection content. The inspection unit (e.g., inspection unit 302) may execute the first inspection content set for the first inspection area with priority over the second inspection content set for the second inspection area. This will allow the user to perform complex image inspections by utilizing the priority system.

[0117] [Perspectives B8, B9] The user interface may include an area (e.g., an area setting button 414c) that displays identification information for the third inspection area set for the sheet image. Furthermore, the user interface may include an area (e.g., a content selection menu 415c) that displays the third inspection content to be performed on the third inspection area in a selectable manner. The inspection unit 302 executes the first inspection content set for the first inspection area with priority over the second inspection content set for the second inspection area and the third inspection content set for the third inspection area. Furthermore, the inspection unit 302 may execute the second inspection content set for the second inspection area with priority over the third inspection content set for the third inspection area.

[0118] [perspective B10] The area in the user interface that displays the selectable test options may be a list or menu that displays multiple test options as selectable candidates. This will allow the user to easily decide and select the test options.

[0119] [Perspective B11, B12] The inspection unit 302 may compare the reference data 211 with the inspection data in the inspection area and determine whether the additional image overlaps with the image pre-formed on sheet P. The image pre-formed on sheet P may be, for example, lines or characters.

[0120] [perspective B13] The inspection unit 302 may determine the difference between the reference data 211 and the inspection data in the inspection area and determine the print quality of the additional image formed on the sheet based on this difference. This difference may also be used to detect the overlap of the two images described above.

[0121] [Perspective B14, B15] The inspection unit 302 may compare the reference data 211 with the inspection data in the inspection area and determine whether the additional image is misaligned with respect to the grid lines pre-formed on sheet P. The inspection unit 302 may compare the reference data 211 with the inspection data in the inspection area, determine the distance h between the grid lines pre-formed on sheet P and the additional image, and determine whether the distance h exceeds a threshold.

[0122] [perspective B16] The large-capacity tray 61 and trays 74a to 74c are examples of first loading units that load sheets P that have been judged as acceptable by the inspection unit. The NG tray 62 is an example of a second loading unit that loads sheets that have been judged as unacceptable by the inspection unit.

[0123] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention. [Explanation of Symbols]

[0124] 52a, 52b: Image sensors, 30: Image forming apparatus, 50: Image inspection apparatus, 51: Inspection controller

Claims

1. An image forming means for forming an image on a sheet; a reading means provided downstream of the image forming means in a sheet conveying direction, the reading means reading an image on the conveyed sheet; A control means, When a first image is formed by the image forming means on a first surface of a first sheet on which a second image has been formed in advance, the control means generates reference data based on a result of reading an image of the first surface of the first sheet by the reading means before the first image is formed; generating first read image data representing a result of the reading means reading an image of the first surface of the first sheet after the first image has been formed by the image forming means; An image forming system that determines the relative positions of the first image and the second image on the first surface of the first sheet on which the first image is formed based on the reference data and the first read image data.

2. 2. The image forming system according to claim 1, further comprising: a stacking means for stacking the first sheet; a conveying means for conveying the first sheet stacked on the stacking means to the image forming means, When the first sheet is transported from the stacking means to the reading means via the image forming means in order for the control means to generate the reference data, the image forming means does not form the first image, the relative position of which is to be determined by the control means, on the first surface of the first sheet, An image forming system, wherein when the first sheet is transported from the stacking means to the reading means via the image forming means so that the control means generates the first read image data, the image forming means forms the first image on the first surface of the first sheet being transported.

3. 2. The image forming system according to claim 1, further comprising: a first stacking unit provided between the image forming unit and the reading unit in the conveying direction, on which the first sheet is stacked; a first conveying means for conveying the first sheet stacked on the first stacking means to the reading means; a second stacking means on which the first sheets are stacked; a second conveying means for conveying the first sheet stacked on the second stacking means to the image forming means; a first guide means for guiding the first sheet conveyed from the image forming means to the reading means; a second guide means for guiding the first sheet conveyed from the first stacking means to the reading means, the second guide means is provided to join the first guide means at a position between the image forming means and the reading means, the control means controls the first transport means so that the first sheet is transported from the first stacking means to the reading means in order to generate the reference data; the control means controls the first transport means so that the first sheet is transported from the second stacking means to the reading means via the image forming means in order to generate the first read image data; The image forming system includes a first image forming unit that forms the first image on the first surface of the first sheet transported from the second stacking unit.

4. 2. The image forming system according to claim 1, further comprising: a first stacking means for stacking the first sheets; a first conveying means for conveying the first sheet stacked on the first stacking means to the image forming means, the control means controls the first transport means so that the first sheet stacked on the first stacking means is transported to the image forming means after the generation of the reference data is completed; The image forming system, wherein the image forming means forms the first image on the first surface of the first sheet transported by the first transport means after generation of the reference data is completed.

5. 5. The image forming system according to claim 4, When the first sheet is transported from the first stacking means to the reading means via the image forming means in order for the control means to generate the reference data, the image forming means does not form the first image, the relative position of which is to be determined by the control means, on the first surface of the first sheet, An image forming system, wherein when the first sheet is transported from the first stacking means to the reading means via the image forming means so that the control means generates the first read image data, the image forming means forms the first image on the first surface of the first sheet being transported.

6. The image forming system according to claim 4, further comprising: a second stacking unit provided between the image forming unit and the reading unit in the conveying direction, on which the first sheet is stacked; a second conveying means for conveying the first sheet stacked on the second stacking means to the reading means; a first guide means for guiding the first sheet conveyed from the image forming means to the reading means; a second guide means for guiding the first sheet conveyed from the second stacking means to the reading means, the second guide means is provided to join the first guide means at a position between the image forming means and the reading means, the control means controls the second transport means so that the first sheet is transported from the second stacking means to the reading means in order to generate the reference data; the control means controls the first transport means so that the first sheet is transported from the first stacking means to the reading means via the image forming means in order to generate the first read image data; The image forming system includes a first image forming unit that forms the first image on the first surface of the first sheet conveyed from the first stacking unit.

7. 7. The image forming system according to claim 1, An image forming system, wherein the control means generates the reference data based on an average value of image data representing the result of the reading means reading an image of the first side of the first sheet on which the first image is not formed and image data obtained by the reading means reading the side of a second sheet on which the first image is not formed, and the second image is formed in advance on the side of the second sheet.

8. The image forming system according to any one of claims 1 to 7, further comprising: an input means having a display means for displaying an image corresponding to the reference data; the input means accepts a selection of a determination area in which the relative position is to be determined in the image displayed on the display means; The control means determines the relative positions of the first image and the second image in the judgment area on the first surface of the first sheet on which the first image is formed based on the reference data and the first read image data.

9. 9. The image forming system according to claim 8, further comprising: The display means includes a first display area in which an image corresponding to the reference data is displayed; and a second display area that displays a screen for accepting settings for the content of an inspection to be performed on the judgment area.

10. 10. The image forming system according to claim 1, An image forming system, wherein the second image is a ruled line or a character.

11. The image forming system according to any one of claims 1 to 10, The control means determines whether the first image and the second image overlap as the relative positions based on the reference data and the first read image data.

12. 12. The image forming system according to claim 11, The control means calculates a difference between pixel values ​​of the reference data and pixel values ​​of the first read image data, and determines whether the first image and the second image overlap based on the difference.

13. 13. The image forming system according to claim 12, The control means determines that the first image and the second image overlap when the difference is greater than or equal to a predetermined value, and determines that the first image and the second image do not overlap when the difference is less than the predetermined value.

14. The image forming system according to any one of claims 11 to 13, the control means determines, based on the reference data and the first read image data, a distance between the first image and the second image as the relative position in an image on the first surface of the first sheet where it has been determined that the first image and the second image do not overlap as the relative position; The control means determines whether or not the determined distance is equal to or greater than a predetermined distance.

15. The image forming system according to any one of claims 11 to 14, further comprising: a first discharge stacking means provided downstream of the reading means in the transport direction, to which the first sheet on which it has been determined that the first image and the second image are overlapped is discharged; An image forming system having a second discharge stacking means, which is provided downstream of the reading means in the conveying direction and to which the first sheet is discharged when it is determined that the first image and the second image do not overlap.

16. The image forming system according to any one of claims 11 to 15, further comprising: the image forming system further comprising a notification unit configured to notify information indicating a result of a determination of an overlap between the first image and the second image as the relative position.

17. The image forming system according to any one of claims 1 to 10, the control means determines a distance between the first image and the second image as the relative position based on the reference data and the first read image data; The control means determines whether or not the determined distance is equal to or greater than a predetermined distance.

18. 18. The image forming system of claim 17, further comprising: a first discharge tray that is provided downstream of the reading means in the conveying direction and that receives sheets for which it has been determined that the determined distance is equal to or greater than a predetermined distance; a second discharge tray that is provided downstream of the reading means in the transport direction and on which sheets for which it is determined that the determined distance is not greater than a predetermined distance are stacked.

19. 19. The image forming system according to claim 17 or 18, further comprising: the image forming system further comprising a notification unit that notifies information indicating a determination result as to whether or not the determined distance is equal to or greater than a predetermined distance.

Images