JP2017072632A - Image reading device and image formation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reading device and an image formation system which are excellent in producibility of an image.SOLUTION: An image reading device 3 includes a rear surface reading part 61 for reading a rear surface of a sheet P that is transported on a transportation path FR, a surface reading part 62 which is arranged on a lower stream side than the rear surface reading part 61 on the transportation path FR, for reading the surface of the sheet P, and a control part 80 which compares a rear surface reading image that has been read by the rear surface reading part 61 with an original image which is the information about the image formed on the surface of the sheet P, for outputting the information of a portion different from the original image to the surface reading part 62. In this case, the surface reading part 62, based on the information of the portion different from the original image, reads a surface of the sheet P whose rear surface has been read.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image reading apparatus and an image forming system.

  2. Description of the Related Art Conventionally, an image reading apparatus that reads a conveyed sheet is known. This image reading apparatus includes an image reading unit (front surface reading unit) that reads the front side of the paper and an image reading unit (back side reading unit) that reads the back side in order to read both sides of the paper in one transport. I have. Each image reading unit has a predetermined reading width in the paper width direction, and is configured by, for example, a line sensor in which elements are arranged linearly in the paper width direction.

  The image reading apparatus reads a document, generates image data for the image forming apparatus to form an image on a sheet, reads a sheet output from the image forming apparatus, and feeds back the read information to the image forming apparatus. Therefore, it is used in such a way as to correct a color shift, a position shift, and a magnification shift.

  For example, Patent Document 1 discloses an image forming system including one or more image forming apparatuses. In this image forming system, each image forming apparatus includes a color detection unit that detects the color of a patch after fixing formed on a sheet. Then, the color detection unit of one or a plurality of image forming apparatuses detects the test chart, and the density-gradation characteristics of one or a plurality of image forming apparatuses are controlled based on the detection result. Yes.

  For example, Patent Document 2 discloses an image forming apparatus in which a line spectrometer is disposed above a paper discharge tray from which a paper sheet on which an image is formed is discharged. In this image forming apparatus, based on the spectral reflectance distribution of the multi-order color toner image on the paper obtained by the line spectrometer, the output halftone dot ratio of each primary color toner image constituting the multi-order color toner image is estimated. The image forming condition of the primary color toner image is corrected based on a comparison result between the estimated value and the control halftone dot ratio of the primary color.

JP 2003-107833 A JP 2012-155309 A

  However, this type of image reading apparatus has a problem that due to the basis weight of the paper, for example, with thin paper, an image on the surface opposite to the reading surface is seen through, and accurate reading becomes difficult. In addition, if there is a pattern on the surface opposite to the reading surface, there is a problem that the color is changed and read, and the color reading accuracy is lowered.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an image reading apparatus and an image forming system that are excellent in image reproducibility.

  In order to solve such a problem, the first invention provides a conveyance path for conveying a sheet on which an image is formed, a first image reading unit for reading a first surface of the sheet conveyed on the conveyance path, and A second image reading unit that is disposed on the downstream side of the first image reading unit in the conveyance path and reads a second surface opposite to the first surface; and a first image reading unit. The read image of the first surface that has been read is compared with an original image that is information about the image formed on the first surface, and information on a portion different from the original image is sent to the second image reading unit. An image reading apparatus having a control unit for outputting is provided. Here, the second image reading unit reads the second surface of the paper on which the first surface has been read based on information on a portion different from the original image.

  Here, in the first invention, the distance between the first image reading unit and the second image reading unit is the sheet conveyance time from the first image reading unit to the second image reading unit. The first image reading unit is set to be longer than the time from when the first surface starts to be read until information on a portion different from the original image is output to the second image reading unit. It is preferable.

  In the first invention, the control unit causes the first image reading unit to start reading the first surface during the sheet conveyance time from the first image reading unit to the second image reading unit. It is preferable to control the sheet conveyance speed so that the time from when the information different from the original image is output to the second image reading unit becomes longer than the time.

  The first invention preferably further includes a colorimetric unit that is arranged on the downstream side of the second image reading unit in the conveyance path and performs colorimetry on the paper.

  In the first invention, it is preferable that the control unit divides the processed image into a plurality of regions and performs the processing in parallel on each region.

  According to a second aspect of the invention, there is provided an image forming apparatus for forming an image on a sheet, and an image reading apparatus according to the first aspect of the present invention to which a sheet on which an image is formed by the image forming apparatus is supplied. An image forming system is provided.

  An image reading apparatus and an image forming system excellent in image reproducibility can be provided.

Explanatory drawing which shows typically the structure of the image forming system which concerns on this embodiment. Flowchart showing control method of image reading apparatus

  FIG. 1 is an explanatory diagram schematically showing a configuration of an image forming system according to the present embodiment. The image forming system according to the present embodiment includes a paper feeding device 1, an image forming device 2, an image reading device 3, and a post-processing device 4.

  The paper feeding device 1 is a device for storing a large amount of paper P and feeding the paper P to the image forming apparatus 2. The paper feeding device 1 is connected to the upstream side of the image forming device 2 in the paper transport direction (the arrow direction in the figure). The paper feeding device 1 includes, for example, a plurality of paper feeding trays (not shown), and the paper P is stored in each paper feeding tray.

  The image forming apparatus 2 is, for example, an electrophotographic image forming apparatus, and forms a full-color image by arranging a plurality of photosensitive drums facing one intermediate transfer belt in the vertical direction, so-called tandem. Type color image forming apparatus. The image forming apparatus 2 is mainly composed of a document reading device SC, four sets of image forming units 10Y, 10M, 10C, and 10K, a fixing device 30, and a control unit 40.

  The document reader SC irradiates an image of the document with the optical system of the illumination device, reads the reflected light with a line image sensor, and obtains an image signal. The image signal is subjected to processing such as A / D conversion, shading correction, and compression, and then input to the control unit 40 as image data. Note that the image data input to the control unit 40 is not limited to the data read by the document reading device SC. For example, the data received from a personal computer connected to the image forming device or another image forming device, a semiconductor memory It may be read from a portable recording medium.

  The four image forming units 10Y, 10M, 10C, and 10K include an image forming unit 10Y that forms a yellow (Y) image, an image forming unit 10M that forms a magenta (M) image, and a cyan (C) image. The image forming unit 10 </ b> C to be formed and the image forming unit 10 </ b> K that forms a black (K) image are configured.

  The image forming unit 10Y corresponding to yellow includes a photosensitive drum 11Y and a charging unit, an optical writing unit, a developing device, a drum cleaner, and the like disposed around the photosensitive drum 11Y.

  The surface of the photosensitive drum 11Y is uniformly charged by the charging unit, and a latent image is formed on the photosensitive drum 11Y by scanning exposure by the optical writing unit. The developing device develops the latent image on the photosensitive drum 11Y by developing with toner. As a result, an image (toner image) corresponding to yellow is formed on the photosensitive drum 11Y. The image formed on the photosensitive drum 11Y is sequentially transferred to a predetermined position on the rotating intermediate transfer belt 15 by the primary transfer roller.

  The configuration of the image forming units 10M, 10C, and 10K corresponding to the other colors is the same as the configuration of the image forming unit 10Y corresponding to yellow, and detailed description thereof is omitted, but each of the image forming units 10Y. It can be read by replacing “Y” attached to the reference numerals of the constituent elements with “M”, “C”, and “K”.

  The image transferred onto the intermediate transfer belt 15 is transferred onto the paper P transported at a predetermined timing by the paper transport unit 20 by the secondary transfer roller 16. The secondary transfer roller 16 is disposed in pressure contact with the intermediate transfer belt 15, and a transfer nip is formed between the intermediate transfer belt 15 and the secondary transfer roller 16.

  The paper transport unit 20 transports the paper P fed from the paper feeding device 1 along the transport path. A plurality of transport members that transport the paper P are provided in the transport path. Each of the conveying members is composed of a pair of rollers that are in pressure contact with each other, and at least one of the rollers is rotationally driven by receiving power from an electric motor that is a driving unit.

  In addition, the image forming apparatus 2 includes one or more paper feed trays 21. Each paper feed tray 21 accommodates paper P. The paper P stored in the paper feed tray 21 is fed one by one by the paper feed unit 22 and sent out to the transport path.

  The fixing device 30 is a device that performs a fixing process for fixing the transferred image onto the paper P. The fixing device 30 includes, for example, a pair of fixing rollers that are pressed against each other to form a fixing nip, and a heater that heats the fixing roller. The fixing device 30 fixes the transferred image on the paper P through the action of pressure applied by the pair of fixing rollers and heat of the fixing rollers. The sheet P on which the fixing process has been performed is discharged out of the apparatus (in the present embodiment, the image reading apparatus 3) by the discharge roller 23.

  When image formation is performed also on the back surface of the paper P, the paper P on which image formation on the front surface of the paper has been completed is conveyed to the refeed conveyance path by the switching gate 24. In the re-feed conveyance route, the rear end of the conveyed paper P is nipped by the reverse roller, and then reversely fed to reverse the front and back of the paper P. The sheet P with the front and back reversed is transported by a plurality of transport members and returned to a required position on the transport path in order to provide image formation on the other surface.

  The control unit 40 has a function of controlling the image forming apparatus 2 in an integrated manner, and a microcomputer mainly composed of a CPU, a ROM, a RAM, and an I / O interface can be used. The control unit 40 forms an image on the paper P by controlling the image forming units 10Y, 10M, 10C, 10K and the like.

  The control unit 40 is configured to be able to communicate with the sheet feeding device 1, the image reading device 3, and the post-processing device 4, and controls the entire image forming system that links the devices.

  The operation panel 45 is an input unit including a touch panel and hard keys capable of inputting information according to information displayed on the display. The user can input information regarding the paper P, image density and magnification, a paper feed tray serving as a paper feed source, and the like through an operation on the operation panel 45. Information input from the operation panel 45 is input to the control unit 40. The operation panel 45 also functions as a display unit by displaying various information to the user via a display that forms part of the operation panel 45. The display content on the operation panel 45 (display) is controlled by the control unit 40.

  The image reading device 3 is disposed downstream of the image forming device 2 in the paper conveyance direction. When the image reading device 3 receives the paper P output from the image forming device 2, the image reading device 3 reads the paper P and performs colorimetry, and generates feedback information for adjusting color characteristics in the system.

  The image reading device 3 is mainly configured by a back side reading unit 61, a front side reading unit 62, a color measurement unit 63, and a control unit 80. In the image reading apparatus 3, the paper P output from the image forming apparatus 2 is conveyed from upstream to downstream inside the apparatus by a plurality of conveyance rollers arranged along the conveyance path FR, and outside the apparatus (in this embodiment, the rear side) It is discharged to the processing device 4).

  The back surface reading unit 61 reads the paper P with respect to the back surface of the paper P transported along the transport path FR. Reading the paper P by the back side reading unit 61 not only means reading the paper P itself but also includes reading an image formed on the paper P (the same applies to the front side reading unit 62 described later). .

  The back surface reading unit 61 is arranged in an upward state on the lower side of the transport path FR so as to face the back surface of the paper P being transported through the transport path FR. Note that the front and back of the paper P expressed in the description of the image reading device 3 is a surface corresponding to the upper side of the paper P conveyed in the image reading device 3, and a surface corresponding to the lower side is a back surface. Therefore, it does not necessarily coincide with the front surface (surface on which images are primarily formed) and the back surface (surface on which images are secondarily formed) of the paper P in image formation.

  The back surface reading unit 61 is an image scanner mainly composed of a light source for irradiating light to the conveyed paper P and a line image sensor composed of, for example, a CCD or CIS. The line image sensor is a one-dimensional array of a plurality of elements that perform photoelectric conversion for each pixel in the paper width direction (direction intersecting the paper conveyance direction). The reading range of the back side reading unit 61 has a predetermined width along the sheet width direction, and is set to cover the maximum width of the sheet P fed to the image reading device 3, for example. The back surface reading unit 61 performs reading for each line according to the conveyed paper P and sequentially outputs image data, thereby generating image data corresponding to one page of paper. The generated image data is output to the control unit 80.

  A background plate 64 is disposed at a position facing the back surface reading unit 61 with the conveyance path FR interposed therebetween. The background plate 64 functions as an opposing surface serving as a reading reference for the back surface reading unit 61, and is configured of, for example, a white flat plate.

  The front surface reading unit 62 reads the paper P with respect to the front surface of the paper P that is transported along the transport path FR. The front surface reading unit 62 is disposed in a downward state on the upper side of the transport path FR so as to face the front surface of the paper P transported through the transport path FR. Similar to the back side reading unit 61, the front side reading unit 62 is an image scanner mainly composed of a light source for irradiating the conveyed paper P with light and a line image sensor constituted by, for example, a CCD or CIS. The front surface reading unit 62 performs reading for each line according to the conveyed paper P and sequentially outputs image data, thereby generating image data corresponding to one page of paper. The generated image data is output to the control unit 80.

  A background plate 65 is disposed at a position facing the surface reading unit 62 with the conveyance path FR interposed therebetween. The background plate 65 functions as an opposing surface serving as a reading reference for the front surface reading unit 62, and is configured of, for example, a white flat plate.

  In this embodiment, the distance L between the back surface reading unit 61 and the front surface reading unit 62 is set so as to satisfy the following requirements. This requirement is that the paper conveyance time from the back side reading unit 61 to the front side reading unit 62 is different from the original image described later after the back side reading unit 61 starts reading the back side of the paper P. That is, the time until the data is output to the reading unit 62 is exceeded. In this case, a predetermined reference speed is used as the conveyance speed of the paper P.

  The color measurement unit 63 performs color measurement on the paper P conveyed on the conveyance path FR, and generates an absolute value of the color of the paper P. The color measurement of the paper P by the back side reading unit 61 not only means the color measurement of the paper P itself, but also includes the color measurement of an image formed on the paper P. The color measurement unit 63 is disposed downward on the upper side of the transport path FR so as to face the front side of the paper P being transported on the transport path FR.

  The color measurement unit 63 is, for example, a spectrocolorimeter, which irradiates the paper P with a light source and measures the spectral reflectance and the wavelength of each reflected light. The color measurement unit 63 generates color information about the color measurement target by applying the measurement result to a color space (three-dimensional space). The color information measured by the color measurement unit 63 is expressed in a predetermined color space such as L * a * b * color system. The color measurement unit 63 is controlled by the control unit 80 and performs color measurement on the paper P in accordance with the transport operation of the paper P. The color measurement result of the color measurement unit 63 is generated as numerical data (color information) expressed in a predetermined color space, and is output to the control unit 80.

  In addition, a background plate 66 is disposed at a position facing the color measurement unit 63 with the conveyance path FR interposed therebetween. The background plate 66 functions as a facing surface that faces the colorimetric unit 63, and is formed of, for example, a white flat plate.

  The control unit 80 has a function of controlling the image reading apparatus 3 in an integrated manner, and a microcomputer mainly composed of a CPU, a ROM, a RAM, and an I / O interface can be used. That is, the control unit 80 controls each unit of the image reading apparatus 3 by reading a program stored in the ROM and operating according to the program. In other words, the program causes the control unit (computer) to execute a control method of the image reading apparatus 3 including each process described later.

  As one of the features of the present embodiment, when the paper P on which an image is formed is supplied from the image forming apparatus 2, the control unit 80 operates the back surface reading unit 61 in accordance with the conveyance of the paper P. . As a result, the back side of the paper P is read by the back side reading unit 61.

  The control unit 80 compares the read image on the back surface read by the back surface reading unit 61 with the original image, and outputs information on a portion different from the original image to the front surface reading unit 62. Here, the original image is information about the image formed on the back surface of the paper P, and is held as image data by the control unit 40 of the image forming apparatus. That is, this original image is an image of a document read by the document reader SC, an image of a document received from a personal computer connected to the image forming apparatus or another image forming apparatus, or a portable recording such as a semiconductor memory. An image of a document read from a medium.

  Then, the control unit 80 operates the front surface reading unit 62 in accordance with the conveyance of the paper P. In this case, the front surface reading unit 62 reads the front surface of the paper P on which the back surface has been read in advance based on information on a portion different from the original image.

  Further, the control unit 80 operates the color measurement unit 63 in accordance with the conveyance of the paper P. Thereby, the color measurement unit 63 measures the color of the paper P.

  The control unit 80 generates feedback information for adjusting the color characteristics of the image forming system based on the image data read by the back surface reading unit 61 and the front surface reading unit 62 and the color information measured by the color measuring unit 63. To do.

  Specifically, the control unit 80, based on the image data output from the back side reading unit 61 and the front side reading unit 62, color information regarding the image formed by the image forming apparatus 2, the image position and magnification of the paper front and back sides. Information is generated, and this information is output to the image forming apparatus 2. The image forming apparatus 2 can correct image color reproducibility, image position characteristics, and magnification characteristics based on the feedback information.

  In outputting the feedback information, the control unit 80 generates information that associates the color information output from the color measurement unit 63 with the color information of the images read by the back side reading unit 61 and the front side reading unit 62. ing. With this information, the image data read by the back side reading unit 61 and the front side reading unit 62 can be corrected so that the color characteristics thereof correspond to the color information measured by the color measuring unit 63.

  FIG. 2 is a flowchart illustrating a method for controlling the image reading apparatus 3. The processing shown in this flowchart is executed by a control unit (CPU) 80 that operates according to a predetermined program, triggered by detection of the paper P by a paper sensor (not shown) arranged upstream of the back surface reading unit 61. In executing this control method, the control unit 80 acquires image data about an image (original image) formed on the paper P by the image forming apparatus 2 by communicating with the image forming apparatus 2.

  First, in step 10 (S10), the back side reading unit 61 starts reading the back side of the paper P based on the operation signal of the control unit 80.

  In step 11 (S11), the control unit 80 compares the image read by the back side reading unit 61 (hereinafter referred to as “back side read image”) with the original image corresponding to the back side, and whether there is a different part or not. Judging. For example, when the original image is white (no image) but a pattern appears on the back side scanned image, the pattern is an image formed on the front surface of the paper P (hereinafter referred to as “front surface image”). Is considered to be a show-through. In addition, when there is a significant color difference between the original image and the back side scanned image, the front side image shows through, and the image formed on the back side of the paper P (hereinafter referred to as “back side image”) is the front side image. Is considered to have appeared. Thus, when the surface image is show-through, a different portion appears between the images.

  If an affirmative determination is made in step 11, that is, if there is a difference between the back-side read image and the original image, the process proceeds to step 12 (S12). On the other hand, if a negative determination is made in step 11, that is, if there is no difference between the back side scanned image and the original image, the process proceeds to step 15 (S15) described later.

  In step 12, the control unit 80 recognizes a portion different from the original image in the back side scanned image as the front surface image. And the control part 80 acquires the positional information and color information about a surface image based on a back surface read image and an original image. The position information is specified as, for example, a position from the paper edge. For example, the color information is specified as a density decomposed into RGB components.

  In step 13 (S13), the control unit 80 outputs position information and color information about the surface image to the surface reading unit 62.

  In step 14 (S14), the control unit 80 performs a correction process on the back side scanned image. This correction process is a process for eliminating the influence of the show-through of the front surface image from the back side scanned image. For example, when a pattern appears in the back side scanned image even though the original image is white (no image), the pattern is deleted from the back side scanned image. In addition, when there is a significant color difference between the original image and the back side scanned image, the color information of the back side scanned image is corrected by subtracting the color information of the front side image.

  In step 15 (S15), the front surface reading unit 62 starts reading the surface of the paper P based on the operation signal of the control unit 80. In this case, the front surface reading unit 62 reads the front surface of the paper P based on the front surface image (position information and color information). That is, the surface reading unit 62 corrects an image actually read by the surface reading unit 62 (hereinafter referred to as “surface reading image”) so as to correspond to position information and color information about the output surface image. Output.

  In step 16 (S 16), the color measurement unit 63 starts color measurement for the paper P based on the operation signal of the control unit 80.

  In step 17 (S17), the control unit 80 determines whether or not the back surface reading unit 61 continues the reading operation. If an affirmative determination is made in step 17, that is, if the back surface reading unit 61 continues the reading operation, the process returns to step 11. On the other hand, if a negative determination is made in step 17, that is, if the back surface reading unit 61 does not continue the reading operation, the process proceeds to step 18 (S18).

  In step 18, the control unit 80 determines whether there is a sheet relating to the next unit. If an affirmative determination is made in step 18, that is, if there is a sheet relating to the next section, the process returns to step 10. On the other hand, if a negative determination is made in step 18, that is, if there is no sheet relating to the next section, this routine is ended (END).

  Then, the control unit 80 performs color characteristics of the image forming system based on the back side scanned image and the front side scanned image output from the back side scanning unit 61 and the front side scanning unit 62 and the color information output from the colorimetric unit 63. To generate feedback information to adjust.

  Specifically, the control unit 80, based on the back side scanned image and the front side scanned image output from the back side scanning unit 61 and the front side scanning unit 62, the color information regarding the image formed by the image forming apparatus 2 and the front and back sides of the paper. Information relating to the image position and magnification is generated, and this information (feedback information) is output to the image forming apparatus 2. With this information, the image forming apparatus 2 can correct image color reproducibility, image position characteristics, and magnification characteristics.

  In outputting the feedback information, the control unit 80 obtains the color information output from the color measurement unit 63 and the color information of the back side read image and the front side read image read by the back side reading unit 61 and the front side reading unit 62. The associated information is generated. By referring to this information, the control unit 80 can correct the back side scanned image and the front side scanned image so that the color characteristics thereof correspond to the color information measured by the color measuring unit 63.

  As described above, the image reading apparatus 3 of the image forming system according to the present embodiment reads the conveyance path FR that conveys the paper P on which an image is formed, and the back surface reading that reads the back surface of the paper P that is conveyed along the conveyance path FR. Unit 61, a front side reading unit 62 that is disposed downstream of the back side reading unit 61 in the transport path FR and reads the front side of the paper P, and a back side read image read by the back side reading unit 61 And a control unit 80 that outputs information on a portion different from the original image to the surface reading unit 62 in comparison with the original image that is information about the image formed on the surface. In this case, the front surface reading unit 62 reads the front surface of the paper P from which the back surface is read based on information on a portion different from the original image.

  According to this configuration, it is possible to recognize the show-through of the front surface image that appears in the back side scanned image by comparing the back side scanned image with the original image. As a result, it is possible to perform appropriate processing such as removing the show-through portion from the back side scanned image. Further, since the surface reading unit 62 performs reading in consideration of information on a portion different from the original image, the reproducibility of the surface reading image output from the surface reading unit 62 can be ensured. Thereby, it is possible to provide the image reading device 3 having excellent image reproducibility.

  Further, in the present embodiment, the distance L between the back side reading unit 61 and the front side reading unit 62 is the sheet conveyance time from the back side reading unit 61 to the front side reading unit 62, and the back side reading unit 61 reads the back side. It is set so that it is longer than the time until the information of the part different from the original image is output to the surface reading unit 62 after the start of.

  According to this configuration, since the distance L from the back side reading unit 61 to the front side reading unit 62 is optimized, the sheet P is obtained by the back side reading unit 61 before the paper P reaches the front side reading unit 62. Information is output to the surface reading unit 62. Therefore, a series of processes can be performed in real time during the process of transporting the paper P from the back side reading unit 61 to the front side reading unit 62.

  Note that the above-described distance L may not be ensured due to the device configuration. In this case, the controller 80 may variably control the paper transport speed to ensure real-time performance. That is, the control unit 80 determines that the sheet conveyance time from the back side reading unit 61 to the front side reading unit 62 is different from the original image after the back side reading unit 61 starts reading the back side. On the other hand, the sheet conveyance speed may be controlled so as to be equal to or longer than the time until output.

  In the present embodiment, the image reading apparatus 3 further includes a color measurement unit 63 that is arranged on the downstream side of the front surface reading unit in the transport path FR and performs color measurement on the surface of the paper P.

  According to this configuration, the color information of the read image can be associated with the color information measured by the color measuring unit 63. Thereby, the read image can be corrected so as to correspond to the color information measured by the color measurement unit 63. As a result, information with high color reliability can be fed back to the image forming apparatus 2.

  In the present embodiment, the control unit 80 may divide the processed image into a plurality of areas and perform the processes in parallel on the respective areas when performing the above-described processing.

  According to this configuration, the time required for processing the back side scanned image and the original image can be shortened, so that the distance L can be minimized. Thereby, size reduction of the image reading apparatus 3 and an image forming system is realizable.

  The image forming system according to the embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications are possible within the scope of the invention. . The image reading apparatus itself constituting the image forming system also functions as part of the present invention. In the present exemplary embodiment, the method in which the control units of the respective apparatuses cooperate to perform processing has been described. However, these control units may be integrated and the control unit of the image forming apparatus may perform the function. A control device that executes the processing shown in the present embodiment may be provided separately.

  In the above-described embodiment, the back side reading unit is arranged on the upstream side and the front side reading unit is arranged on the downstream side, but the order of these image reading units may be reversed. In the present embodiment, the image reading apparatus disposed on the downstream side of the image forming apparatus has been described. However, the present invention is applied to an original reading apparatus that generates image data used for image formation by the image forming apparatus. Also good.

DESCRIPTION OF SYMBOLS 1 Paper feeder 2 Image forming apparatus 10Y, 10M, 10C, 10K Image forming part 20 Paper conveyance part 30 Fixing apparatus 40 Control part 3 Image reading device 61 Back surface reading part (1st image reading part)
62 Surface reading unit (second image reading unit)
63 Colorimetry unit 80 Control unit

Claims (6)

A transport path for transporting the paper on which the image is formed;
A first image reading unit for reading a first surface of a sheet conveyed along the conveyance path;
A second image reading unit that is arranged on the downstream side of the first image reading unit in the conveyance path and that reads a second surface opposite to the first surface;
The read image of the first surface read by the first image reading unit is compared with an original image that is information about an image formed on the first surface, and information on a portion different from the original image And a control unit that outputs to the second image reading unit,
The image reading apparatus, wherein the second image reading unit reads the second surface of the sheet on which the first surface has been read based on information of a portion different from the original image.   The distance between the first image reading unit and the second image reading unit is such that the sheet conveyance time from the first image reading unit to the second image reading unit is equal to the first image reading unit. It is set to be longer than the time from when the image reading unit starts reading the first surface until information of a portion different from the original image is output to the second image reading unit. The image reading apparatus according to claim 1.   The control unit is configured so that a sheet conveyance time from the first image reading unit to the second image reading unit is determined after the first image reading unit starts reading the first surface. 2. The image reading according to claim 1, wherein the sheet conveyance speed is controlled so that information of a portion different from the original image is equal to or longer than a time until the information is output to the second image reading unit. apparatus.   4. The image reading according to claim 1, further comprising a color measurement unit that is arranged on the downstream side of the second image reading unit in the transport path and performs color measurement on a sheet. 5. apparatus.   5. The image reading apparatus according to claim 1, wherein the control unit divides the processed image into a plurality of regions and performs processing on each region in parallel. An image forming apparatus for forming an image on paper;
The image reading apparatus according to claim 1, wherein a sheet on which an image is formed by the image forming apparatus is supplied.
An image forming system comprising:

Images