Image reading device and image forming device

Abstract

To accurately correct a reading error of an image formed on a recording medium when a branch unit for causing a conveyance path of the recording medium to branch is provided on the downstream side of an image reading unit in a conveyance direction of the recording medium.SOLUTION: An image reading device according to an aspect of the present invention has: a conveying unit that conveys a recording medium having a first surface and a second surface in a conveyance direction; a reading unit that reads an image formed on the recording medium; a first path that is provided on the downstream side of the reading unit in the conveyance direction and does not invert the direction in which the recording medium is conveyed; a second path that is provided on the downstream side of the reading unit in the conveyance direction and inverts the direction in which the recording medium is conveyed; a branch unit that causes the conveyance path of the recording medium to branch into the first path and the second path on the downstream side of the reading unit in the conveyance direction; and an output unit that outputs a corrected image in which a reading error between the read image of the first surface and the read image of the second surface is corrected based on read images in which each of the first surface and the second surface is read by the reading unit.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an image reading device and an image forming device. [Background technology]

[0002] Conventionally, in an image forming apparatus such as a printer, a configuration is known in which an image formed on a recording medium is read by an image reading device after the image is formed in order to detect the amount of misalignment of an image actually formed on the recording medium relative to an image that is ideally formed on the recording medium.

[0003] In this image reading device, if a branching section that branches the transport of the recording medium is provided downstream of the image reading section in the transport direction of the recording medium, the recording medium being transported may be skewed near the branching section, causing a reading error in the image on the recording medium. If a reading error occurs, the amount of misalignment of the image formed on the recording medium cannot be accurately detected.

[0004] In order to suppress reading errors by an image reading device, a configuration is known in which correction data based on the results of measuring the skew of a recording medium near a branching point is stored in the image reading device when the image reading device is shipped, and the stored correction data is referenced when reading an image to correct the reading error.

[0005] Also, in order to control the transport of a recording medium such as paper, a configuration has been disclosed in which, based on the detection results of the leading and trailing edges of the paper during the double-sided path, the rotational deviation angle of the leading edge of the paper with an image formed on its surface and the amount of deviation in parallelism between the leading and trailing edges of the paper are calculated, and a skew correction method is selected based on the rotational deviation angle and the parallelism deviation angle (see, for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0006] However, with the conventional configuration, there was a concern that if components of the image reading device were to become misaligned after shipment of the image reading device, or if the correction data differed depending on the type of recording medium, it would not be possible to accurately correct the reading error.

[0007] Furthermore, the configuration of Patent Document 1 does not have a branching section for branching the conveyance of the recording medium downstream of the reading section in the conveyance direction of the recording medium, and therefore cannot correct the above-mentioned reading error.

[0008] The present invention aims to accurately correct reading errors of an image formed on a recording medium when a branching section that branches the transport of the recording medium is provided downstream of the image reading section in the transport direction of the recording medium. [Means for solving the problem]

[0009] An image reading device according to one aspect of the present invention includes a transport unit that transports a recording medium having a first side and a second side in a transport direction, a reading unit that reads an image formed on the recording medium, a first path that is provided downstream of the reading unit in the transport direction and does not reverse the direction in which the recording medium is transported, a second path that is provided downstream of the reading unit in the transport direction and reverses the direction in which the recording medium is transported, and a branching unit that branches the transport of the recording medium into the first path and the second path downstream of the reading unit in the transport direction. before Based on the read images obtained by reading each of the first side and the second side by a reading unit, a correction unit that corrects a reading error that is a difference between the read image of the first side and the read image of the second side; An output unit that outputs the corrected image. The correction unit detects the reading error when the recording medium passes through the first path after the second surface is read by the reading unit, and The recording medium is After the second surface is read by the reading unit, the reading error when passing through the second path is corrected using a difference image between the read image of the first surface and the read image of the second surface, the difference image being different from each other and obtained in advance. . Effect of the Invention

[0010] According to the present invention, when a branching section that branches the transport of the recording medium is provided downstream of the image reading section in the transport direction of the recording medium, reading errors of an image formed on the recording medium can be accurately corrected. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating an example of the configuration of an image forming system according to an embodiment. [Diagram 2] FIG. 2 is a diagram illustrating an example of a hardware configuration of an information processing device according to an embodiment. [Diagram 3] FIG. 2 is a diagram illustrating an example of a hardware configuration of an image forming apparatus according to an embodiment. [Figure 4] 1 is a diagram illustrating an example of the configuration of an image forming apparatus according to a first embodiment. [Diagram 5] 3 is a diagram showing an example of the arrangement of a reading unit and a transport path according to the first embodiment. FIG. [Figure 6] 2 is a diagram illustrating an example of a functional configuration of a processing unit of the image forming apparatus according to the embodiment. [Figure 7] 7A and 7B are diagrams showing an example of paper transport, where FIG. 7A is a diagram of a non-reverse path, and FIG. 7B is a diagram of a reverse path. [Figure 8] FIG. 13 is a diagram showing an example of a reading error. [Figure 9] FIG. 1 is a first diagram showing an example of correction of a reading error. [Figure 10] FIG. 2 is a second diagram showing an example of correction of a reading error. [Figure 11] 13 is a diagram showing an example of timing for acquiring a reading error in a reverse path. [Figure 12] 12A and 12B are diagrams showing examples of correction data corresponding to paper types and environmental conditions, with FIG. 12A being a diagram for general setting paper, and FIG. 12B being a diagram for user setting paper. [Figure 13] FIG. 11 is a diagram of an equal magnification optical system of an image forming apparatus according to a second embodiment. [Figure 14] FIG. 11 is a diagram showing a reduction optical system of an image forming apparatus according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each drawing, the same components are given the same reference numerals, and duplicated explanations will be omitted as appropriate.

[0013] In the following, an embodiment will be described taking an image forming system having an image reading device as an example. The image forming system is, for example, an image forming system for commercial printing that prints a desired image on a large number of sheets of paper or other printing media.

[0014] Note that the embodiments shown below are examples of an image reading device and an image forming device for embodying the technical idea of ​​the present invention, and the present invention is not limited to the embodiments shown below. Unless otherwise specified, the shapes of the components described below, their relative positions, parameter values, etc. are intended to be illustrative and not to limit the scope of the present invention. Furthermore, the sizes and positional relationships of the components shown in the drawings may be exaggerated to clarify the explanation. Furthermore, the terms printing, image formation, and printing in the embodiments are all synonymous.

[0015] <Example of Overall Configuration of Image Forming System 100> First, Fig. 1 is a diagram for explaining an example of the configuration of an image forming system 100. As shown in Fig. 1, the image forming system 100 has a client PC (Personal Computer) 101, a DFE (Digital Front End) 102, an image forming apparatus 103, and a management server 104. These are connected to each other so as to be able to communicate with each other via the Internet or the like.

[0016] The client PC 101 creates a print job that the user wants to print, and transmits the print job to the DFE 102 or the management server 104. The client PC 101 is equipped with a display unit that is a liquid crystal display, and input devices such as a mouse and a keyboard.

[0017] The DFE 102 receives a print job from the client PC 101 or the management server 104 , creates rendering data using a RIP (Raster Image Processor) engine based on the received print job, and transmits the rendering data to the image forming apparatus 103 .

[0018] The image forming apparatus 103 forms an image on a recording medium based on the drawing data received from the DFE 102. The management server 104 manages the print jobs received from the client PC 101. Further, in response to a request from the DFE 102, the management server 104 transmits the print jobs to the DFE 102. Note that a plurality of image forming apparatuses and a plurality of client PCs may be communicably connected to the image forming system 100.

[0019] <Example of the hardware configuration of the DFE 102> Next, FIG. 2 is a block diagram for explaining an example of the hardware configuration of the DFE 102. As shown in FIG. 2, the DFE 102 includes a CPU (Central Processing Unit) 201, a ROM (Read Only Memory) 202, a RAM (Random Access Memory) 203, an HDD (Hard Disk) / SSD (Solid State Drive) 204, and an I / F (Interface) 205.

[0020] Among these, the CPU 201 uses the RAM 203 as a work area and controls the operation of the entire DFE 102 by executing the programs stored in the ROM 202.

[0021] The HDD / SSD 204 is used as a storage unit and stores preset setting values. The information stored in the HDD / SSD 204 may be used by the CPU 201 when reading and executing programs.

[0022] The I / F 205 is an interface that enables communication between the DFE 102 and the client PC 101, the image forming apparatus 103, and the management server 104.

[0023] <Example of the hardware configuration of the image forming apparatus 103> 3 is a block diagram illustrating an example of a hardware configuration of the image forming apparatus 103. As shown in FIG. 3, the image forming apparatus 103 includes a CPU 301, a ROM 302, a RAM 303, a HDD / SSD 304, an I / F 305, an image forming unit 306, and a reading unit 307.

[0024] Of these, the CPU 301 uses a RAM 303 as a working area and executes a program stored in a ROM 302 to control the overall operation of the image forming apparatus 103 .

[0025] The HDD / SSD 304 is used as a storage unit and stores preset setting values. The information stored in the HDD / SSD 304 may be read by the CPU 301 and used when executing a program.

[0026] The I / F 305 is an interface that enables communication between the image forming apparatus 103, the DEF 102, the client PC 101, and the management server 104.

[0027] The image forming unit 306 is a print engine that forms an image on paper. The reading unit 307 reads the image formed on the paper.

[0028] [First embodiment] <Example of configuration of image forming apparatus 103> Next, Fig. 4 is a diagram for explaining an example of the configuration of the image forming apparatus 103 according to the first embodiment. As shown in Fig. 4, the image forming apparatus 103 has tandem electrophotographic photoconductor drums 403K, 403C, 403M, and 403Y, an intermediate transfer belt 402, a secondary transfer roller 404, a paper feed unit 500, a pair of conveying rollers 401, a fixing roller 405, an in-line sensor 406, and a conveying path 408. The conveying path 408 also has a reversing path 407, a non-reversing path 409, and a branching section 410. The in-line sensor 406 constitutes a part of the reading unit 307.

[0029] The paper feed section 500 has a paper feed tray 501, a pickup roller 502, and a paper feed roller 503. The paper feed tray 501 accommodates a plurality of papers stacked on top of each other. The recording medium may be paper such as recording paper (transfer paper), but is not limited thereto, and may be coated paper, cardboard, an overhead projector (OHP) sheet, a plastic film, a prepreg, copper foil, or the like, as long as it is a medium on which an image can be formed (recorded).

[0030] The paper feed unit 500 picks up the papers stacked and stored in the paper feed tray 501 in order from the top by a pickup roller 502, and supplies the picked up papers to the conveying roller pair 401 by using a pair of rollers, paper feed rollers 503. The paper feed unit 500 may be configured to have other rollers for conveying the papers.

[0031] The image forming unit 306 includes photoconductor drums 403K, 403C, 403M, and 403Y, an intermediate transfer belt 402, a secondary transfer roller 404, and a fixing roller 405.

[0032] The image forming apparatus 103 is a so-called tandem type image forming apparatus having a configuration in which photoconductor drums 403Y, 403M, 403C, and 403K of each color (hereinafter collectively referred to as photoconductor drums 403) are arranged along an intermediate transfer belt 402, which is an endless moving means. The photoconductor drums 403Y, 403M, 403C, and 403K are arranged in order from the upstream side in the conveying direction of the intermediate transfer belt 402 along the intermediate transfer belt 402, on which an intermediate transfer image to be transferred to a sheet fed from a paper feed unit 500 and conveyed by a pair of conveying rollers 401 is formed. The pair of conveying rollers 401 is an example of a conveying unit that conveys the sheet in the conveying direction A.

[0033] The image forming device 103 carries a toner image of each color developed with toner on the surface of the photosensitive drum 403 of each color, and transfers the carried toner images in a superimposed manner onto the intermediate transfer belt 402, thereby forming a full-color image on the intermediate transfer belt 402.

[0034] The image forming device 103 transfers the full-color image formed on the intermediate transfer belt 402 onto the surface of the paper transported on the transport path 408 at a position closest to the paper transport path 408, indicated by the dashed line in the figure, by using the function of the secondary transfer roller 404.

[0035] The paper with the image formed on its surface is further transported, and the image is fixed (image formed) by fixing rollers 405. Fixing rollers 405 are a fixing section that thermally fixes the image onto the paper. Fixing rollers 405 fix the full-color toner image onto the paper by applying heat and pressure to the paper onto which the full-color toner image has been transferred. Fixing rollers 405 can generate heat from a built-in heater such as a halogen heater to heat the paper.

[0036] An in-line sensor 406 is provided downstream of the fixing roller 405 in the paper conveying direction A. The in-line sensor 406 reads the image fixed on the paper to obtain a read image. The in-line sensor 406 reads the front side after an image is formed on the front side, and reads the back side after an image is formed on the back side. Here, the front side of the recording medium corresponds to the first side, and the back side corresponds to the second side.

[0037] In-line sensor 406 is a CCD (Charge Coupled Device) line sensor in which pixels that output electrical signals according to the intensity of received light are arranged in a one-dimensional array. The direction in which the pixels are arranged intersects with the paper transport direction. In-line sensor 406 also includes a pixel array that receives red light (R), a pixel array that receives green light (G), and a pixel array that receives blue light (B). In the following, red may be represented as R, green as G, and blue as B, respectively.

[0038] The in-line sensor 406 outputs an electrical signal according to the light intensity of the reflected light from the image formed on the paper by the pixel array of each color. The image forming apparatus 103 uses the light intensity (density) of each color of the image read by the in-line sensor 406 as color information for correcting the color of the image.

[0039] In-line sensor 406 may include a light source that irradiates light onto the paper. Irradiating light from the light source onto the paper ensures sufficient brightness for reading by in-line sensor 406. In-line sensor 406 may be configured with a complementary metal-oxide-semiconductor (CMOS) or a photodiode (PD) array instead of a CCD.

[0040] After the image is read by the in-line sensor 406, the paper reaches a branching section 410 provided downstream in the conveying direction A. At the branching section 410, which branches the conveying of the paper into a non-reverse path 409 and a reverse path 407, the paper is conveyed along one of the paths.

[0041] The non-reversing path 409 is provided downstream of the reading unit 307 in the conveying direction A, and is an example of a first path in which the direction in which the paper is conveyed is not reversed.

[0042] The reversing path 407 is provided downstream of the reading unit 307 in the conveying direction A, and is an example of a second path that reverses the direction in which the paper is conveyed. For example, when performing double-sided printing on paper, the image forming apparatus 103 forms an image on the front side of the paper, then conveys the paper to the reversing path 407 in the conveying path 408, and after the paper is reversed, conveys it again to the position of the secondary transfer roller 404.

[0043] Of the components described above, the pair of conveying rollers 401 , the in-line sensor 406 , the non-reverse path 409 , the reverse path 407 , and the branching section 410 form part of the image reading device 600 .

[0044] 5 is a diagram illustrating an example of the arrangement of the reading unit 307 and the transport path 408. As shown in Fig. 5, the reading unit 307 has an in-line sensor 406, a glass 71, and a revolver 72. The reading unit 307 reads the image formed on the paper P as a two-dimensional image by repeatedly reading an image for one line extending in the paper width direction in accordance with the paper passing operation of the paper P passing through the reading position.

[0045] In-line sensor 406 includes a light source that irradiates light onto paper P passing through the reading position, and a line image sensor in which multiple imaging elements that perform photoelectric conversion for each pixel are arranged one-dimensionally in the width direction of paper P. The imaging elements are optical sensors that perform an operation of reading an image on paper P at the reading position.

[0046] The revolver 72 is provided facing the in-line sensor 406, and reflects the light irradiated onto the paper P when reading an image. The revolver 72 can also change the background color according to the color of the paper P, etc.

[0047] Glass 71 is provided between in-line sensor 406 and revolver 72, facing revolver 72, and transmits light emitted from a light source and reflected light that is the irradiated light reflected and returned by revolver 72 or paper P. Glass 71 prevents paper P from flapping as it passes between glass 71 and revolver 72 when paper P is read by in-line sensor 406.

[0048] In order to minimize flapping of the paper P, upstream reading transport rollers 412 are disposed upstream of the reading unit 307, and downstream reading transport rollers 413 are disposed downstream of the reading unit 307.

[0049] After being read by the reading unit 307, the paper P is branched at a branching unit 410 and transported in either the direction of the arrow 11 or the direction of the arrow 12. The paper P that has traveled in the direction of the arrow 11 is transported along a non-reverse path 409 by the drive of downstream reading transport rollers 413. The paper P that has traveled in the direction of the arrow 12 is transported along a reverse path 407 by the drive of reverse transport rollers 414 and 415.

[0050] Here, distance D1 indicates the distance between the reading unit 307 and the branching unit 410 along the transport direction A, and distance D2 indicates the length of the paper P along the transport direction A. In this embodiment, for example, distance D1 is shorter than distance D2.

[0051] Users of the image forming system 100 often output printed matter face-down (printed surface facing down). For example, in order to output face-down during single-sided printing, the inversion path 407 is used. During double-sided printing, the inversion path 407 is used after an image is formed on the front side of the paper P, and the non-inversion path 409 is used after an image is formed on the back side.

[0052] Although FIG. 5 illustrates an in-line sensor such as a contact image sensor integrated with a light source, the embodiment can also be applied to a reduction optical system in which the light source and the in-line sensor are separate.

[0053] <Example of functional configuration of the processing unit 700> Next, Fig. 6 is a block diagram showing an example of the functional configuration of the processing unit 700. As shown in Fig. 6, the processing unit 700 has a correction unit 701, a storage unit 702, and an output unit 703. The function of the correction unit 701 is realized by the CPU 301 executing a program stored in the ROM 302 or the HDD / SSD 304 of Fig. 3 or the like. The function of the storage unit 702 is realized by the HDD / SSD 304 or the like. The function of the output unit 703 is realized by the I / F 305 or the like. The processing unit 700 also constitutes a part of the image reading device 600.

[0054] The correction unit 701 corrects the reading error of the front side read image Im1 relative to the back side read image Im2 based on the front side read image Im1 and the back side read image Im2 obtained by reading the front side and back side of the paper by the reading unit 307, respectively.

[0055] Furthermore, the storage unit 702 can store correction data for the reading error acquired by the correction unit 701 in response to at least one of the type of paper or the environmental conditions around the image forming apparatus 103. The correction unit 701 can also correct the reading error using the correction data stored in the storage unit 702.

[0056] The output unit 703 can output a corrected image Im1' obtained by correcting the front side read image Im1 by the correction unit 701 to the image forming unit 306 or the like.

[0057] <Example of reading error> Next, reading errors by the reading unit 307 will be described with reference to Fig. 7 and Fig. 8. Fig. 7 shows an example of paper transport, with Fig. 7(a) showing the non-inverting path 409 and Fig. 7(b) showing the inverting path 407. Fig. 8 shows an example of a read image Im, with Fig. 8(a) showing the non-inverting path 409 and Fig. 8(b) showing the inverting path.

[0058] 7 shows a plan view of the transported paper P, and illustrates how the positional relationship between the paper P and the in-line sensor 406 changes over time as the paper P is transported. The white arrows indicate the passage of time.

[0059] In the inversion path 407, the sliding load on the paper P during transport is larger than that in the non-inversion path 409, so the paper P may be skewed (rotated) during reading by the reading unit 307. Therefore, when the leading edge of the paper P is transported to the inversion path 407 during reading, reading errors Ex and Ey occur in the read image Im with respect to the ideal read image Im0, as shown in FIG.

[0060] The reading error Ex is a reading error in the main scanning direction, and the reading error Ey is a reading error in the sub-scanning direction. The image leading edge Imf is the leading edge of the read image Im that is read first when read by the reading unit 307, and the image trailing edge Imb is the trailing edge of the read image Im that is read last when read by the reading unit 307. The leading edge of the paper P enters the inversion path 407 during reading, and then gradually skews, so that the reading errors Ex and Ey gradually increase as it advances toward the image trailing edge Imb.

[0061] Such reading errors Ex and Ey are due to the sliding load applied to the paper P during transport, and therefore vary depending on the stiffness, surface properties, basis weight, and the like of the paper P.

[0062] <Example of reading error correction> Next, the correction process of the reading errors Ex and Ey performed by the correction unit 701 will be described with reference to Fig. 9 and Fig. 10. Fig. 9 and Fig. 10 are diagrams for explaining an example of the correction of the reading errors Ex and Ey, Fig. 9 being Fig. 1 and Fig. 10 being Fig. 2. Fig. 10 explains the handling of the reading error Ey in more detail.

[0063] Here, the image forming apparatus 103 has an automatic registration adjustment function that adjusts the position of an image to be formed on the paper P before the paper P is fed through the image forming apparatus 103. When performing automatic registration adjustment, the front and back sides of the paper P are read, but since the same paper P is read, when the back side is read on the non-reversing path 409, the leading edge and trailing edge of the paper P are reversed compared to when the front side is read on the reversing path 407. Therefore, the difference between the front side read image and the back side read image in the automatic registration adjustment corresponds to the reading error on the reversing path 407.

[0064] 9, the correction unit 701 acquires the front side read image Im1 and the back side read image Im2 from the reading unit 307, and then inverts the back side read image Im2 upside down. Then, image difference processing is performed on the front side read image Im1 and the back side read image Im2 to acquire a difference image ΔIm. Then, by reflecting the difference image ΔIm in the front side read image Im1, a corrected image Im1' is obtained in which the reading errors Ex and Ey caused by conveying the paper P on the reversal path 407 are corrected.

[0065] In addition, the correction process by the correction unit 701 can correct not only the reading errors Ex and Ey associated with transporting the paper P on the reversal path 407, but also other reading errors such as reading errors due to expansion and contraction of the paper after fixing and reading errors due to differences in transport speed.

[0066] Also, in the non-reversing path 409, a reading error may occur due to skew of the paper P during reading, although this is not as large as in the reversing path 407. If the reading error in the non-reversing path 409 is α, the difference between the reading error in the reversing path 407 and the reading error in the non-reversing path 409 is β, and the reading error in the reversing path 407 is γ, then the relationship shown in the following formula (1) is satisfied. γ = α + β (1)

[0067] Of these, the reading error γ corresponds to the correction data used to correct the read image read when the paper passes through the inversion path 407, the difference in the reading errors β corresponds to the correction data that differs for each type of paper, and the reading error α corresponds to a unique value for each image forming device.

[0068] In FIG. 10, position Ydc is the reading position of one corner C of the image trailing end Imb1 in the front-surface read image Im1 during the reversal pass 407 in the sub-scanning direction. If the ideal position is position Yc, then there is the relationship shown in the following equation (2). Ydc = Yc + α + β (2)

[0069] Similarly, if the reading position of the corner C read by the non-reversed path 409 is taken as a position Yuc, the relationship with respect to the position Yuc is expressed by the following formula (3). Yuc = Yc + α (3)

[0070] Ideally, even if there is a reading error α in the non-inverting path 409 or the inverting path 407, the reading error α will be the same value. Therefore, the difference β in the reading error between the non-inverting path 409 and the inverting path 407 is obtained by the following equation (4). Ydc-Yuc=β (4)

[0071] The reading error α is used by the correction unit 701 after the position Yc is separately measured by a measuring device capable of accurately measuring the image position.

[0072] By obtaining the reading error difference β in this manner, the position Ydc obtained in the inversion path 407 is substituted into the following equation (5): This makes it possible to obtain a position rYdc in which the reading error difference β is accurately corrected. Ydc-β=Yc+α=rYdc (5)

[0073] Similarly, for the reading position Ydd at the other corner D of the image trailing edge Imb1 during the reversal pass 407 in the sub-scanning direction, a position rYdd with the reading error Ey accurately corrected can be obtained.

[0074] 11 is a diagram showing an example of the timing for acquiring the reading errors Ex and Ey in the reverse path 407. After an image is formed in the image forming apparatus 103, the reading unit 307 reads the paper P and the image formed on the paper P to acquire position information of the image relative to the paper P.

[0075] As described above, the image forming apparatus 103 has an automatic registration adjustment function, and can obtain an appropriate image position by reading images formed on several sheets of paper P with the reading unit 307.

[0076] 11, in the automatic registration adjustment, there are two timings for reading the same paper P for each sheet P, one for reading the front side and one for reading the back side. In this case, by controlling the paper to always pass through the reversing path 407 during double-sided printing and pass through the non-reversing path 409 after image formation on the back side, the reading errors Ex and Ey in the reversing path 407 can be obtained. By correcting the reading errors Ex and Ey during the subsequent image formation, an accurate read image can be obtained.

[0077] In addition, when a print job is sent to the image forming device 103, images are formed on a predetermined number of sheets of paper P specified in the print job, but it is preferable to correct the reading errors Ex and Ey before the print job is executed.

[0078] Next, Fig. 12 shows an example of correction data corresponding to the paper type and environmental conditions, Fig. 12(a) shows the case of general setting paper, and Fig. 12(b) shows the case of user setting paper. The tables shown in Fig. 12(a) and Fig. 12(b) are stored in the storage unit 702.

[0079] When automatic registration adjustment is performed during paper passing with the general settings, the reading errors Ex and Ey are stored as correction data in the corresponding locations in the table in Fig. 12. As a result, the next time paper is passed with the same settings, the correction data can be obtained by referring to the storage unit 702 and used for correction. Also, when the reading errors Ex and Ey are misaligned due to a positional shift or the like in the components of the image forming apparatus 103, the reading errors Ex and Ey can be obtained again by performing automatic registration adjustment and stored in the storage unit 702.

[0080] Furthermore, the transport error of the paper P may differ depending on the rigidity of the paper P, and the rigidity of the paper P is affected by temperature and humidity. For example, the rigidity of the paper P is high in an LL (low temperature, low humidity) environment, and the rigidity of the paper P is low in an HH (high temperature, high humidity) environment. Therefore, even for the same paper type, different correction data can be stored for each temperature and humidity.

[0081] The same is true for user-defined paper. For paper that has not been subjected to automatic registration adjustment, the reading errors Ex and Ey are obtained by performing automatic registration adjustment, and are stored in the storage unit 702 as correction data.

[0082] <Effects of the Image Reading Apparatus 600 and the Image Forming Apparatus 103> As described above, the image reading device 600 according to this embodiment includes a pair of conveying rollers (conveying section) that conveys a sheet of paper P (recording medium) having a front side (first side) and a back side (second side) in a conveying direction A, and a reading section 307 that reads an image formed on the sheet of paper P. The image reading device 600 also includes a non-reversing path 409 (first path) that is provided downstream of the reading section 307 in the conveying direction A and does not reverse the direction in which the sheet of paper P is conveyed, and a reversing path 407 (second path) that is provided downstream of the reading section 307 in the conveying direction A and reverses the direction in which the sheet of paper P is conveyed. Furthermore, downstream of the reading unit 307 in the transport direction A, there is a branching unit 410 that branches the transport of the paper P into a non-reverse path 409 and an inverse path 407, and an output unit 703 that outputs a corrected image Im1' in which the reading errors Ex and Ey of the read image of the back side relative to the read image of the front side are corrected based on the read images of the front and back sides read by the reading unit 307.

[0083] With this configuration, when a branching section 410 that branches the transport of paper P is provided downstream of the reading section 307 in the transport direction A of paper P, reading errors Ex and Ey of the image formed on paper P can be accurately corrected.

[0084] In particular, if the distance between the reading unit 307 and the branching unit 410 along the transport direction A is shorter than the length of the paper P in the transport direction A, part of the paper P enters the reversing path 407, which has a large sliding load on the paper P, during reading by the reading unit 307, and the paper P is likely to be skewed and reading errors Ex and Ey are likely to occur. Even in this case, Ex and Ey can be appropriately corrected. However, the same effect can be obtained even if the distance between the reading unit 307 and the branching unit 410 along the transport direction A is not shorter than the length of the paper P in the transport direction A.

[0085] In this embodiment, the image reading device 600 includes a storage unit 702 capable of storing correction data for the reading errors Ex and Ey acquired by the correction unit 701 in response to at least one of the type of paper P and the environmental conditions around the image reading device 600. The correction unit 701 corrects the reading errors Ex and Ey using the correction data stored in the storage unit 702.

[0086] As a result, when passing paper with the same settings as when the correction data was obtained, the correction data can be obtained by referring to the storage unit 702 and used for correction, thereby saving the effort and time required to obtain the correction data.

[0087] Moreover, the image forming apparatus 103 according to this embodiment has an image forming unit 306 that forms an image on paper P, and an image reading device 600 that is provided downstream of the image forming unit 306. The image forming unit 306 can correct image formation based on a read image read by the image reading device 600. This makes it possible to accurately detect the amount of misalignment of the image formed on paper P and correct the image formation, thereby improving the quality of the image formed on paper P.

[0088] Furthermore, in this embodiment, the correction unit 701 corrects the reading errors Ex and Ey based on the read images of the multiple sheets of paper P read by the reading unit 307 before the image forming unit 306 forms images on the predetermined number of sheets of paper P. This makes it possible to improve the quality of the images formed on each of the predetermined number of sheets of paper P specified in the print job.

[0089] [Second embodiment] Next, a second embodiment will be described. In the image forming apparatus 103a according to the second embodiment, a paper cooling unit 450 is provided after fixing. Fig. 13 is a diagram showing an example of the configuration when the reading unit 307 has an equal magnification optical system, and Fig. 14 is a diagram showing an example of the configuration when the reading unit 307 has a reduction optical system 308.

[0090] 13 and 14, the above-described embodiment can be applied to a configuration in which a paper cooling unit 450 is provided after fixing, and similar effects can be obtained. Also, the reading unit 307 can have either an equal magnification optical system or a reduction optical system.

[0091] Although the embodiments have been described above, the present invention is not limited to the above specifically disclosed embodiments, and various modifications and changes are possible without departing from the scope of the claims.

[0092] Further, in the above-described embodiment, an image forming system including an electrophotographic image forming apparatus has been described, but the present invention is also applicable to an image forming system including an image forming apparatus of another type, such as an inkjet type.

[0093] In addition, all numbers such as ordinal numbers and quantities used in the description of the embodiments are merely examples for specifically explaining the technology of the present invention, and the present invention is not limited to the exemplified numbers. Furthermore, the connection relationships between the components are merely examples for specifically explaining the technology of the present invention, and the connection relationships for realizing the functions of the present invention are not limited to these.

[0094] In addition, the division of blocks in the functional block diagram is an example, and multiple blocks may be realized as one block, one block may be divided into multiple blocks, and / or some functions may be transferred to another block. Furthermore, the functions of multiple blocks having similar functions may be processed in parallel or in a time-division manner by a single piece of hardware or software.

[0095] Each function of the above-described embodiments can be realized by one or more processing circuits. Here, the term "processing circuit" in this specification includes a processor programmed to execute each function by software, such as a processor implemented by an electronic circuit, and a device such as an ASIC (Application Specific Integrated Circuit), a DSP (digital signal processor), an FPGA (field programmable gate array), or a conventional circuit module designed to execute each function described above. [Explanation of symbols]

[0096] 71 Glass 72 Nosepiece 100 Image forming system 103 Image forming device 306 Image forming section 307 Reading Unit 401 Pair of conveying rollers (an example of a conveying section) 406 Inline Sensor 407 Reverse Path (An example of the second route) 408 Transport Route 409 Non-reverse path (example of the first route) 410 Branch 600 Image reader 701 Correction Unit 702 Storage Unit 703 Output section A Conveying direction D1, D2 distance Im1 Surface reading image Im2 Back side image reading [Prior art documents] [Patent documents]

[0097] [Patent Document 1] JP 2019-085215 A

Claims

1. a conveying section that conveys a recording medium having a first side and a second side in a conveying direction; A reading unit that reads an image formed on the recording medium; a first path that is provided downstream of the reading unit in the transport direction and does not reverse the direction in which the recording medium is transported; a second path that is provided downstream of the reading unit in the transport direction and that reverses the direction in which the recording medium is transported; a branching section that branches the conveyance of the recording medium into the first path and the second path at a downstream side of the reading section in the conveyance direction; a correction unit that corrects a reading error, which is a difference between a read image of the first side and a read image of the second side, based on read images obtained by reading each of the first side and the second side by the reading unit; an output unit that outputs a corrected image corrected by the correction unit, The correction unit is the reading error when the recording medium passes through the first path after the second surface is read by the reading unit; and An image reading device that corrects the reading error when the recording medium passes through the second path after the second surface is read by the reading unit, using a difference image between the read image of the first surface and the read image of the second surface, the difference images being different from each other and obtained in advance.

2. The distance between the reading unit and the branch unit along the conveying direction is 2. The image reading apparatus according to claim 1, wherein the length of the recording medium is shorter than the length of the recording medium.

3. a storage unit capable of storing correction data for the reading error corresponding to at least one of the type of the recording medium and the environmental conditions around the image reading device; 3. The image reading device according to claim 1, wherein the output unit outputs the corrected image in which the reading error has been corrected using the correction data stored in the storage unit.

4. 4. The method according to claim 1, wherein the reading unit has either a unity magnification optical system or a reduction optical system.

2. The image reading device according to claim 1.

5. an image forming unit for forming an image on the recording medium; and the image reading device according to claim 1 , which is provided downstream of the image forming unit, The image forming apparatus, wherein the image forming section is capable of correcting image formation based on a read image read by the image reading device.

6. The image forming apparatus according to claim 5, wherein the output unit outputs the corrected image in which the reading error is corrected based on the read images of the plurality of recording media read by the reading unit before the image forming unit forms images on a predetermined number of the recording media.

Images