JP2016191779A - Image reading device, image forming apparatus and image forming system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reading device, an image forming apparatus, and an image forming system capable of performing highly accurate image correction.SOLUTION: An image reading device comprises: a reading device 55 for reading a sheet P; a backing 80 which is disposed while facing the reading device 55, and on which a facing surface facing the reading device 55 is formed; and a switching control part 111 for switching a color of the facing surface with respect to the reading device 55 on the backing 80 to black or white, on the basis of momentum for reading the sheet P by the reading device 55. A forming range of a patch 201 formed on the sheet P is determined on the basis of a position of a nip for suppressing sag of the sheet P within an allowable range, a switching time until a color of the facing surface is switched to white by the switching control part 111, and transport speed for transporting the sheet P.SELECTED DRAWING: Figure 1

Description

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

  2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus is known as a multi-function peripheral (MFP) having a composite function of a printer, a copier, and the like. Among such image forming apparatuses, an on-demand image forming apparatus is required to maintain image quality that is not inferior to offset printing. However, at present, an image formed by an electrophotographic method has lower color reproducibility than an image formed by offset printing. Therefore, in order to improve the color reproducibility, various systems have been developed that make color measurement faster and easier and create a color profile and automate the adjustment work.

  Among the above adjustment operations, there is a method for adjusting the absolute value of the color by arranging a colorimeter for measuring the spectral reflectance in-line. As a characteristic of this colorimeter, there is a risk that the colorimetric accuracy may deteriorate depending on the height variation of the paper. Therefore, the colorimeter is fixedly arranged at a position for measuring the central portion (main direction) of the paper where the behavior of the paper is stable and the image forming engine performance is also stable.

  Further, since the colorimeter is a spot measurement, it is configured to measure an image of the full width of the paper by combining with a CCD line sensor (scanner). Since the CCD line sensor cannot guarantee the absolute value of the color, the absolute value of the color can be guaranteed by measuring the patch of the paper with the colorimeter by measuring and associating the same patch as the CCD line sensor with the colorimeter. I am doing.

  In order to guarantee the absolute value of the color, a white surface backing is provided on the surface facing the colorimeter. Thus, the influence of the backing color is eliminated.

  By the way, when patch reading is performed inline without stopping the conveyance of the paper, the color measurement is usually started after the measurement timing of the patch on the conveyed paper is determined. Therefore, some trigger is required for timing detection for measuring the patch. For the determination of the trigger, a reflection type sensor that detects the leading edge of the sheet is used, or a dedicated sensor that measures the trigger patch is used.

  In this case, since the dedicated sensor is provided, the number of parts increases and the cost also increases. Furthermore, since the position of the sensor changes depending on the mounting accuracy, the detection accuracy may be reduced and the patches may be straddled. Thus, there is a technique in which the head patch also serves as a trigger by using the lightness difference between the brightness of the backing and the lightness of the head patch as a trigger (see, for example, Patent Document 1). In this case, in order to compensate for the decrease in detection accuracy, there is a method of enlarging the patch in the sub-scanning direction. However, since the number of patches that can be arranged on one sheet decreases and the number of sheets necessary for measurement increases, the user The burden increases. For example, depending on the content of adjustment, when the number of patches is large, it becomes 1000 or more.

  Further, in the control of measuring the entire area without matching the patch and cutting out only a necessary part, the arrangement of the patch is restricted. In this case, the patches are arranged so that colors having a small brightness difference are not adjacent to each other. Therefore, since the control for determining the arrangement configuration of the patches becomes complicated, the development man-hour is increased, which is not realistic.

  Therefore, there is a technique that detects the leading edge of a sheet based on a change in color when the leading edge of the sheet enters the backing (see, for example, Patent Document 2). In this case, since the colorimeter also serves as a sensor for detecting the leading edge of the paper, the measurement position error is reduced and the measurement accuracy is improved. Further, the leading edge of the paper may be detected by a change in irregularly reflected light reflected on the backing (see, for example, Patent Document 3). The difference may be calculated by comparing the lightness L * of the spectral reflectance with the backing surface. In this case, the backing portion may be a dark color such as black in order to increase the difference from the paper white of the paper.

  By the way, since the colorimeter measures the absolute value of the color, the backing color is preferably white which does not affect the measurement. In order to obtain certification at a color certification authority, the backing color must be white. In view of this, there is a configuration in which the backing color can be switched, which is white in normal times and black in skew correction (see, for example, Patent Document 4).

  In addition, there is a technique in which the backing color is set to a high density when detecting the leading edge of the paper, and the backing color is set to a low density when performing calibration (see, for example, Patent Document 5).

JP 2014-165802 A JP-A-6-130160 JP 2014-1069 A JP 2009-290800 A JP 2014-116676 A

  However, the conventional techniques as described in Patent Documents 1 to 5 do not consider the relationship between the variation in the height direction of the conveyed paper and the patch formation range. In the colorimeter, the color reading accuracy greatly varies depending on the variation in the height direction of the conveyed paper. For this reason, the above prior art can accurately measure the absolute value of the color while accurately detecting the edge of the paper, but it is not in a measurement environment that can ensure the color reading accuracy with high accuracy. . Therefore, there is a possibility that the above-described conventional technology cannot perform image correction with high accuracy.

  SUMMARY An advantage of some aspects of the invention is that it provides an image reading apparatus, an image forming apparatus, and an image forming system capable of performing image correction with high accuracy. There is.

  In order to achieve the above object, an image reading apparatus according to the present invention includes a reading apparatus that reads a sheet, a backing that is disposed to face the reading apparatus and has a facing surface that faces the reading apparatus, and the reading apparatus. A patch control unit configured to switch a color of a surface facing the reading device formed on the backing to either black or white based on a trigger for the device to read the paper; The formation range of the nip position that suppresses the slack of the paper within an allowable range, the switching time until the switching control unit switches the color of the facing surface to white, the conveyance speed at which the paper is conveyed, It is determined based on.

  According to this image reading apparatus, highly accurate image correction can be performed.

  In the image reading apparatus according to the present invention, the nip is formed in each of an upstream conveying roller on the upstream side of the reading apparatus and a downstream conveying roller on the downstream side of the reading apparatus. Is preferred.

  According to this image reading apparatus, it is possible to read a sheet in an area where the height variation of the sheet is small.

  Further, in the image reading apparatus according to the present invention, of the nips, within an inter-nip distance between an upstream nip formed by the upstream transport roller and a downstream nip formed by the downstream transport roller, Preferably, the patch formation range is determined.

  According to this image reading apparatus, it is possible to read the patch in an area where the height variation of the paper is small.

  In the image reading apparatus according to the present invention, it is preferable that the shape and size of the patch are determined based on a reading range of the reading apparatus and the transport speed.

  According to this image processing apparatus, the number of sheets used can be reduced.

  In the image reading device according to the present invention, the switching control unit switches the color of the facing surface to black when the reading device reads either the leading edge or the trailing edge of the paper. Is preferred.

  According to this image reading apparatus, the color of the patch can be measured at the correct position.

  Further, in the image reading apparatus according to the present invention, an image position adjustment mark serving as a reference for adjusting the position of the image formed on the paper is formed, and the image position adjustment mark includes a front end portion of the paper, The switching control is formed in a margin between the first patch of the patches or in a margin between the rear end portion of the sheet and the patch of the rear end of the patch. The unit switches the color of the facing surface from black to white until the reading operation of the leading patch by the reading device is started, and the reading operation of the trailing edge of the sheet by the reading device is performed It is preferable that the color of the facing surface is switched from white to black before the start.

  According to this image reading apparatus, it is possible to accurately read the image position adjustment mark and the patch.

  In the image reading apparatus according to the present invention, it is preferable that the switching control unit switches the color of the facing surface to white when the reading apparatus reads the patch.

  According to this image reading apparatus, the absolute value of the color can be accurately measured.

  In the image reading apparatus according to the present invention, the patch formation range is determined within a transport distance in which the paper is transported according to the transport speed while the color of the facing surface is white. Is preferred.

  According to this image reading apparatus, it is possible to reduce the cost of paper and the color measurement time of patches.

  Further, in the image reading apparatus according to the present invention, the reading device is a spectrocolorimeter or a scanner, and the scanner is provided on the upstream side of the spectrocolorimeter, along the width direction of the paper, It is preferable that a CCD line sensor for reading the paper is provided, and the reading result of the scanner is corrected based on the reading result of the spectrocolorimeter.

  According to this image reading apparatus, it is possible to reduce the time required for adjusting the color of the image formed on the paper.

  In order to achieve the above object, an image forming apparatus according to the present invention is an image forming apparatus provided on the upstream side of the image reading apparatus described above, wherein the position of the nip, the switching time, Based on the acquisition unit that acquires the conveyance speed, the position of the nip acquired by the acquisition unit, the switching time, and the conveyance speed, the formation range of the patch formed on the paper is determined. An image processing unit.

  According to this image forming apparatus, highly accurate image correction can be performed.

  In the image forming apparatus according to the present invention, the image processing unit creates a color profile of the color of an image formed on the paper based on a result of reading the paper by the image reading device. preferable.

  According to this image forming apparatus, it is possible to improve the efficiency of adjusting the color of an image formed on a sheet.

  In order to achieve the above object, an image forming system according to the present invention includes the image reading device described above and the image forming device described above.

  According to this image forming system, an image not inferior to offset printing can be formed on paper.

  According to the present invention, highly accurate image correction can be performed.

1 is a configuration diagram schematically illustrating a configuration of an image forming system according to an exemplary embodiment. 1 is a diagram illustrating an example of a functional configuration of an image forming system according to an embodiment. It is a figure which shows the correspondence of the lightness L * and measurement position when the lightness difference of the adjacent patch 201 is small. It is a figure which shows the correspondence of the brightness L * and measurement position when the brightness difference of the adjacent patch 201 is large. 5 is a diagram showing the color of the surface facing the spectrocolorimeter 70 formed on the backing 80 when reading the edge of the paper P. FIG. FIG. 6 is a diagram showing the color of the surface facing the spectrocolorimeter 70 formed on the backing 80 when reading the patch 201 formed on the paper P. FIG. 6 is a diagram schematically illustrating color switching timing of a surface facing a spectrocolorimeter 70 formed on a backing 80. It is a figure which illustrates roughly the relationship between the color switching timing of the surface facing the spectrocolorimeter 70 formed in the backing 80, and the nip position. It is a figure explaining in steps the relationship between the color switching timing of the surface facing the spectrocolorimeter 70 formed on the backing 80 and the position of the nip. FIG. 6 is a diagram schematically illustrating the color switching timing of the surface facing the spectrocolorimeter formed on the backing when the image position adjustment mark is attached to the paper. 10 is a flowchart illustrating an example of color adjustment processing. It is a flowchart explaining the operation example of a color and image position adjustment process.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments.

  FIG. 1 is a configuration diagram schematically showing a configuration of an image forming system according to the present embodiment. The image forming system includes an image forming apparatus 2 and an image reading apparatus 3. A paper feeding device 1 is provided on the upstream side of the image forming apparatus 2. A paper discharge device 4 is provided on the downstream side of the image reading device 3.

  The image forming apparatus 2 forms an image by, for example, an electrophotographic method, and arranges a plurality of photosensitive drums 11Y, 11M, 11C, and 11K facing one intermediate transfer belt 15 in the vertical direction. This is a so-called tandem color image forming apparatus that forms a full-color image. The image forming apparatus 2 mainly includes a document reading device SC, four sets of image forming units 10Y, 10M, 10C, and 10K, and a fixing device 30.

  The document reader SC scans and exposes an image of the document with the optical system of the scanning exposure 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 as an image read value. Note that the input image data is not limited to the data read by the document reading device SC, and may be, for example, a personal computer connected to the image forming device 2, data received from another image forming device, or 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. Each of the image forming units 10Y, 10M, 10C, and 10K includes a photosensitive drum 11Y, 11M, 11C, and 11K, a charging unit, an optical writing unit, a developing device, and a drum cleaner arranged around the photosensitive drums 11Y, 11M, 11C, and 11K. .

  The surfaces of the photosensitive drums 11Y, 11M, 11C, and 11K are uniformly charged by the charging unit, and a latent image is formed by scanning exposure by the optical writing unit. The developing device develops the latent images on the photosensitive drums 11Y, 11M, 11C, and 11K by developing with toner. As a result, an image (toner image) of a predetermined color corresponding to any one of yellow, magenta, cyan, and black is formed on the photosensitive drums 11Y, 11M, 11C, and 11K. The images formed on the photosensitive drums 11Y, 11M, 11C, and 11K are sequentially transferred to predetermined positions on the rotating intermediate transfer belt 15 by the primary transfer roller.

  The image transferred onto the intermediate transfer belt 15 is transferred by the secondary transfer roller 16 to the paper P that is transported at a predetermined timing by a paper transport unit 20 described later. The secondary transfer roller 16 is disposed in pressure contact with the intermediate transfer belt 15 to form a transfer nip.

  The paper transport unit 20 transports the paper P fed from the paper feed unit 21 along the transport path. In the paper supply unit 21, the paper P is stacked on a paper tray, and the paper P stacked on the paper tray is taken in by the paper supply unit 22 and sent out to the conveyance path. A plurality of paper transport means for transporting the paper P is provided in the transport path. Each of the conveying means 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 through an electric motor that is a driving means. In addition to the configuration of the pair of rollers, the conveyance unit can widely employ a configuration including a pair of rotating members, such as a combination of belts or a combination of a belt and a roller.

  The fixing device 30 is a device that performs a fixing process on the paper P onto which the image has been transferred. 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 one or both of the fixing rollers. The fixing device 30 fixes the transferred image on the paper P through the action of the pressure applied by the pair of fixing rollers and the heat of the fixing roller. The paper P subjected to the fixing process by the fixing device 30 is discharged out of the apparatus by the paper 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 P 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 paper P whose front and back are reversed is transported by a plurality of transport rollers, and is joined to a transport path on the upstream side of the transfer position in order to provide image formation on the other surface.

  The operation panel 45 is a touch panel type input unit capable of inputting information in accordance with information displayed on a display (not shown). The user can set information regarding the paper P, specifically, the density or magnification of the image, a paper tray as a paper supply source, and the like through an operation on the operation panel 45. The operation panel 45 also functions as a display unit that displays various information to the user via the operation panel 45 by being controlled.

  The image reading device 3 is disposed downstream of the image forming device 2. The image reading apparatus 3 is provided with a paper transport unit 50. Further, the image reading device 3 includes a scanner 60a, a scanner 60b, a spectrocolorimeter 70, and the like provided from the upstream side to the downstream side. The paper transport unit 50 has a transport path for transporting the paper P fed from the image forming apparatus 2 and discharging it out of the apparatus. A backing 80a is provided at a position facing the scanner 60a. A backing 80b is provided at a position facing the scanner 60b. A backing 80 c is provided at a position facing the spectrocolorimeter 70. In addition, when any of the backings 80a to 80c is not particularly limited, it is referred to as a backing 80.

  An upstream conveyance roller 91a is provided on the upstream side of the scanner 60a. A downstream transport roller 92a is provided on the downstream side of the scanner 60a. An upstream conveyance roller 91b is provided on the upstream side of the scanner 60b. A downstream side conveyance roller 92b is provided on the downstream side of the scanner 60b. An upstream side conveyance roller 91 c is provided on the upstream side of the spectrocolorimeter 70. A downstream side conveyance roller 92 c is provided on the downstream side of the spectrocolorimeter 70.

  In addition, when any one of the upstream conveyance rollers 91a to 91c is not particularly limited, it is referred to as an upstream conveyance roller 91. Moreover, when any of the downstream side conveyance rollers 92a-92c is not specifically limited, it is called the downstream side conveyance roller 92.

  For example, when receiving the paper P supplied from the image forming apparatus 2, the image reading device 3 detects an image formed on the paper P. The scanners 60a and 60b are arranged so as to face the sheet P conveyed along the conveyance path, respectively, and read an image formed on the sheet P.

  Specifically, the scanner 60a scans the back surface of the paper P, and is used for checking, for example, whether the image printed on the paper P is misaligned or whether there is an unexpected image. The scanner 60b reads the surface of the paper P, and is used for reading an image printed on the paper P, specifically, the patch 201 and the like. Note that the scanner 60 a and the scanner 60 b are collectively referred to as a scanner 60.

  Next, the image forming apparatus 2 and the image reading apparatus 3 will be described with reference to FIG. FIG. 2 is a diagram illustrating an example of a functional configuration of the image forming system according to the present embodiment. The functional configuration of the image forming system can be realized by using a microcomputer mainly composed of a CPU, ROM, RAM, and I / O interface.

  First, the scanner 60 and the spectrocolorimeter 70 will be described. The scanner 60 is provided on the upstream side of the spectrocolorimeter 70, and includes a light source 101 that emits light to the paper P that passes through the reading position and a plurality of image sensors that perform photoelectric conversion for each pixel in a one-dimensional direction in the paper width direction. It is mainly composed of line image sensors arranged side by side. The reading range of the scanner 60 is set so as to cover the maximum width of the paper P that can be supplied from the image forming apparatus 2. The scanner 60 repeats an image reading operation for one line extending in the sheet width direction in accordance with the conveying operation of the sheet P passing through the reading position, whereby the image formed on the sheet P is converted into a two-dimensional image. Read as. The read image is generated as a read value of the image.

  That is, the scanner 60 has a line image sensor that reads the paper P along the width direction of the paper P, and reads the entire width of the paper P as one line in the transport direction of the paper P, thereby reading the image of the entire surface of the paper P. Is something that can be acquired. When the spectrocolorimeter 70 and the scanner 60 are collectively referred to as a reading device 55, the image reading device 3 reads the paper P by the reading device 55, and the result is fed back to the image forming device 2. .

  That is, the image reading apparatus 3 associates the reading result of the scanner 60 based on the reading result of the spectrocolorimeter 70, and the image forming apparatus 2 uses the reading result of the paper P by the image reading apparatus 3. Based on this, a color profile of the color of the image formed on the paper P is created.

  Here, the image pickup device is specifically a CCD (Charge Coupled Device). The CCD is an optical sensor that reads an image on the paper P at a reading position, and functions as a color line sensor that can be read in the entire width in the width direction of the paper P by being arranged in a line. is there.

  Specifically, when the reading operation is actually performed, in addition to the image sensor, an optical system (not shown) and an LED (Light Emitting Diode) light source 101 that illuminates the reading position operate in cooperation. The optical system is for guiding the image at the reading position to the CCD, and includes a plurality of mirrors and a plurality of lenses. The above line image sensor can be realized by the CCD line sensor 103.

  The spectrocolorimeter 70 is disposed so as to face the sheet P conveyed along the conveyance path, and is disposed on the downstream side of the scanner 60. The spectrocolorimeter 70 measures the color of a patch 201 and the like which will be described later.

  Specifically, the spectrocolorimeter 70 irradiates the visible light source from the light source 105 toward the patch 201 and the like, and the spectral imaging unit 107 acquires the spectral spectrum of the reflected light of the visible light source, and a predetermined color system Perform an operation on. Thereby, the color of the patch 201 or the like is derived.

  The colorimetric range of the spectrocolorimeter 70, that is, the viewing angle, is set to be narrower than the reading range of the scanner 60 and narrower than the width of the patch 201 along the paper width direction. Specifically, the lens unit that acquires the reflected light of the patch 201 is, for example, about 4 mm. In this case, the size of the patch 300 of 4 mm + α is required for one spectrocolorimeter 70 in the paper width direction.

  As described above, the spectrocolorimeter 70 performs colorimetry only in a certain viewing angle range, and therefore can reproduce color information with higher accuracy than the scanner 60. For this reason, if the sheet P passes through the transport path only once, color measurement is performed only for one row of patches 201.

  As shown in FIG. 1, the image forming apparatus 2 has a configuration provided on the upstream side of the image reading apparatus 3. The image reading apparatus 3 is operated by either an inline method or an offline method.

  The in-line method is configured to directly feed an image-formed sheet P discharged from the image forming apparatus 2 to the image reading apparatus 3. On the other hand, the off-line method is not configured to feed the image-formed paper P discharged from the image forming apparatus 2 directly to the image reading apparatus 3, but the image forming apparatus 2, the image reading apparatus 3, and the like. Is a system configured independently of each other. Here, the following description will be given on the premise of the inline method, but an offline method may be used.

  Next, the switching control unit 111 and the time measuring unit 113 configured as the functional configuration of the image reading device 3 will be described. Note that the reading device 55 described below assumes a spectrocolorimeter 70, but the reading device 55 may be a scanner 60.

  The backing 80 described above is disposed so as to face the reading device 55, and has a facing surface facing the reading device 55. The switching control unit 111 performs control to switch the color of the facing surface formed on the backing 80. The timing unit 113 counts a preset time after reading the last patch 201_n and the like, and transmits the timing result to the switching control unit 111.

  Specifically, the switching control unit 111 switches the color of the surface facing the reading device 55 formed on the backing 80 to either black or white based on the trigger when the reading device 55 reads the paper P. is there. The switching control unit 111 switches the color of the facing surface formed on the backing 80 to black when the reading device 55 reads either the leading edge or the trailing edge of the paper P.

  More specifically, the switching control unit 111 is configured so that the reading operation of the leading patch 201 by the reading device 55, that is, the facing surface formed on the backing 80 before the reading operation of the patch 201_1 by the reading device 55 is started. Is switched from black to white. The switching control unit 111 switches the color of the facing surface formed on the backing 80 from white to black before the reading device 55 starts the reading operation of the trailing edge of the paper P. The switching control unit 111 switches the color of the facing surface formed on the backing 80 to white when the reading device 55 reads the patch 201.

  Next, the formation range of the patch 201 formed on the paper P will be described. The formation range of the patch 201 includes a nip position that suppresses the slackness of the paper P within an allowable range, a switching time until the switching control unit 111 switches the color of the facing surface formed on the backing 80 to white, and the paper P It is determined based on the transport speed to be transported. The formation range of the patch 201 is determined within the transport distance in which the paper P is transported according to the transport speed of the paper P while the color of the opposing surface formed on the backing 80 is white. is there.

  The nip that suppresses the slackness of the paper P within an allowable range is formed on each of the upstream conveyance roller 91 on the upstream side of the reading device 55 and the downstream conveyance roller 92 on the downstream side of the reading device 55. It is. Among such nips, the formation range of the patch 201 is determined within the inter-nip distance between the upstream nip formed by the upstream transport roller 91 and the downstream nip formed by the downstream transport roller 92. Is. The shape and size of the patch 201 are determined based on the reading range of the reading device 55 and the conveyance speed of the paper P.

  Next, the acquisition unit 121 and the image processing unit 123 configured as the functional configuration of the image forming apparatus 2 will be described. First, the function of forming the patch 201 on the paper P will be described.

  When the image forming apparatus 2 forms the patch 201, the patch is within the transport distance in which the paper P is transported according to the transport speed of the paper P while the color of the opposing surface formed on the backing 80 is white. The color of the facing surface formed on the backing 80 and the transport distance of the paper P are considered so that the formation range of 201 can be configured.

  The acquisition unit 121 includes a position of a nip that suppresses the slackness of the paper P within an allowable range, a switching time until the color of the facing surface formed on the backing 80 is switched to white, a conveyance speed at which the paper P is conveyed, Is something to get.

  The image processing unit 123 determines the formation range of the patch 201 formed on the paper P based on the nip position, the switching time, and the conveyance speed acquired by the acquisition unit 121, and based on the determination result, the image forming unit 10Y, 10M, 10C, and 10K are controlled.

  Specifically, the image processing unit 123 optimizes images to be formed on the image forming units 10Y, 10M, 10C, and 10K based on the reading result of the scanner 60 and the colorimetric result of the spectrocolorimeter 70. Is. Specifically, the image optimization processing includes front and back position adjustment, density adjustment, color adjustment, and the like of the image printed on the paper P.

  The image processing unit 123 forms the patch 201 when, for example, a color adjustment mode command arrives. The color adjustment mode guarantees the absolute value of the color by measuring the color of the patch 201. It is something to be made. In the color adjustment mode, when the image position command is included in the color adjustment mode command, an image position adjustment mark for adjusting the image position is formed, and the image position adjustment is performed. It will be.

  Next, the patch 201 formed on the paper P will be described with reference to FIGS. FIG. 3 is a diagram illustrating a correspondence relationship between the lightness L * and the measurement position when the lightness difference between adjacent patches 201 is small. FIG. 4 is a diagram illustrating a correspondence relationship between the lightness L * and the measurement position when the lightness difference between adjacent patches 201 is large. 3 and 4, a solid circle is a cut-out OK region, and a broken-line circle is a region straddling the patch 201 and is a cut-out NG region.

  When the patch 201 is read inline without stopping the conveyance of the paper P, that is, when the patch 201 is scanned in-line, the patch 201 is usually determined after the measurement timing of the patch 201 on the conveyed paper P is determined. Measurement of the color is started. Therefore, some timing is required for timing detection for measuring the patch 201. In general, such a trigger is determined using a reflective sensor that detects the leading edge of the paper P or a dedicated sensor that measures the trigger patch.

  In such a configuration, since a dedicated sensor is provided, the number of parts increases and the cost also increases. Furthermore, since the position of the sensor changes depending on the mounting accuracy, the detection accuracy of the sensor may be reduced and the patch 201 may be straddled.

  In order to compensate for the decrease in detection accuracy of the sensor, there is a method of enlarging the patch 201 in the sub-scanning direction. In this case, the number of patches that can be arranged on one sheet P is reduced, the number of sheets necessary for measurement is increased, and the burden on the user is increased. For example, depending on the content of adjustment, when the number of patches is large, the number of patches is 1000 or more.

  Specifically, as shown in FIG. 3, when control is performed such that the entire area is measured without matching the patch 201 and only a necessary part is cut out, the brightness difference between adjacent patches 201 is small, and the cut-out OK area is determined. difficult. Therefore, as shown in FIG. 4, by arranging the patches 201 so that colors having a small brightness difference are not adjacent to each other, the brightness difference between the adjacent patches 201 is large and it is necessary to clarify the cut-out OK region. The arrangement of 201 is restricted. The arrangement configuration of the patch 201 shown in FIG. 4 is not realistic because the control method is complicated and the development man-hour is increased.

  Therefore, there is a method of detecting the leading edge of the paper P based on a color change when the paper P is conveyed to the backing 80. In this case, since the spectrocolorimeter 70 also serves as a sensor for detecting the leading edge of the paper P, the measurement position error is reduced and the measurement accuracy is improved. FIG. 5 is a diagram showing the color of the surface facing the spectrocolorimeter 70 formed on the backing 80 when reading the edge of the paper P. FIG. 6 is a diagram showing the color of the surface facing the spectrocolorimeter 70 formed on the backing 80 when the patch 201 formed on the paper P is read. As shown in FIG. 5, the color of the surface facing the spectrocolorimeter 70 formed on the backing 80 is a dark color, for example, black in order to increase the difference from the paper white of the paper P. In this case, in order to detect the edge of the sheet P of the spectrocolorimeter 70, for example, the brightness L * of the spectral reflectance is compared with the facing surface formed on the backing 80, and the difference may be calculated.

  However, in order for the spectrocolorimeter 70 to measure the absolute value of the color, the color of the opposing surface formed on the backing 80 needs to be white which does not affect the measurement. Further, in order to perform authentication with a color certification organization such as JapanColor, FORGA, or G7, white is essential for the color of the opposing surface formed on the backing 80. Therefore, as shown in FIG. 6, the color of the facing surface formed on the backing 80 may be white and the color may be measured.

  However, as shown in FIG. 6, when the color of the facing surface formed on the backing 80 is white, the difference in brightness from the paper white at the leading edge of the paper P becomes small. The error will increase. Therefore, when reading the leading edge of the paper P, a color that is easily discriminated to be paper white, for example, black is used as the color of the opposing surface formed on the backing 80, and the color formed on the backing 80 is determined by a signal obtained by reading the leading edge of the paper P. Control to switch the color of the facing surface to white may be performed.

  When the patch 201 is continuously measured, the color of the facing surface formed on the backing 80 is black until the leading edge of the next paper P reaches the measurement position after the trailing edge of the paper P is detected. What is necessary is just to make it control to hold | maintain. In this way, the difference in brightness between the leading edge of the paper P and the trailing edge of the paper P and the color of the facing surface formed on the backing 80 can be increased. Thereby, the edge part of the paper P can be detected accurately. Further, when measuring the color of the image formed on the paper P, the absolute value of the color can be accurately measured by switching the color of the facing surface formed on the backing 80 to white, and color authentication can be performed. it can.

  FIG. 7 is a diagram schematically illustrating the color switching timing of the surface facing the spectrocolorimeter 70 formed on the backing 80. The leading edge of the paper P and the rear edge of the paper P are not curled because the paper P easily curls due to heat and pressure of the fixing device 30. Therefore, the color of the facing surface formed on the backing 80 is switched using the margin created by not arranging the patch 201. In addition, the color switching speed of the facing surface formed on the backing 80 is always constant.

  FIG. 8 is a diagram schematically illustrating the relationship between the color switching timing of the surface facing the spectrocolorimeter 70 formed on the backing 80 and the nip position. FIG. 9 is a diagram illustrating stepwise the relationship between the color switching timing of the surface facing the spectrocolorimeter 70 formed on the backing 80 and the nip position.

  As shown in FIGS. 8 and 9, the leading edge of the paper P is detected by the density difference between the color of the facing surface formed on the backing 80 and the white color of the paper P on the leading edge side of the paper P in the section X1. . Next, in the section X2, when the backing 80 is rotated, the color of the facing surface formed on the backing 80 is switched from black to white. Next, in the section X3, the leading edge of the paper P is nipped by the downstream side conveyance roller 92. That is, the distance that the sheet P is transported to the section X3 is the distance from the leading end of the sheet P to the position of the nip formed on the downstream side transport roller 92.

  Next, in the section X4, while the paper P is being transported, the color of the facing surface formed on the backing 80 is white, and the paper P is placed on each of the downstream transport roller 92 and the upstream transport roller 91. It will be nipped. Next, in the section X5, the color of the facing surface formed on the backing 80 is switched from white to black by rotating the backing 80. Since the position of the patch 201_n at the rear end is known when the patch 201 is written, control is performed so that the color of the facing surface formed on the backing 80 is switched to black when the section X5 is exceeded. Next, in the section X6, when the color of the facing surface formed on the backing 80 is black, the trailing edge of the paper P is detected.

  As described above, the patch 201 is formed on the condition that, first, the leading edge of the paper P is nipped by the downstream transport roller 92 and the color of the facing surface formed on the backing 80 is switched to white. It becomes. Secondly, the patch 201 is formed on the condition that the trailing edge of the paper P is nipped by the upstream transport roller 91. As described above, the patch 201 is not formed at a position passing through the nip, and the patch 201 is formed between the nips, so that the patch 201 is read in an area where the height fluctuation of the paper P is small. Can do. That is, the formation range of the patch 201 is restricted within the distance between the upstream nip and the downstream nip.

  FIG. 10 is a diagram schematically illustrating the color switching timing of the surface facing the spectrocolorimeter 70 formed on the backing 80 when an image position adjustment mark is added to the paper P. As shown in FIG. 10, the image position adjustment mark is a reference for adjusting the position of the image formed on the paper P. The image position adjustment mark is a margin between the leading edge of the sheet P and the patch 201_1 that is the first patch 201 of the patches 201, or the trailing edge of the sheet P and the trailing edge of the patch 201. It is formed in the margin between the patch 201_n which is 201.

  When reading the image position adjustment mark, after the image position adjustment mark is read, the color of the facing surface formed on the backing 80 is completely switched to white, and the leading edge of the paper P is nipped by the downstream conveyance roller 92. It is a condition. It should be noted that the image position adjustment mark has a larger tolerance for reading accuracy in the height direction than in the case of color, so that the leading edge of the paper P does not need to be nipped by the downstream transport roller 92.

  Next, color adjustment processing and color and image position adjustment processing will be described. FIG. 11 is a flowchart for explaining an operation example of the color adjustment processing. FIG. 12 is a flowchart for explaining an operation example of color and image position adjustment processing.

  In step S11, it is determined whether or not the color adjustment mode is set. If it is in the color adjustment mode (YES in step S11), the process proceeds to step S12 to determine whether or not there is an image position adjustment mark. If there is an image position adjustment mark (YES in step S12), the process proceeds to step S13 to perform color adjustment. When the process is executed and there is no image position adjustment mark (NO in step S12), the process proceeds to step S27, and the color and image position adjustment process is executed. On the other hand, if it is not the color adjustment mode (step S11 NO), it waits for a command for the color adjustment mode to arrive.

(Color adjustment processing)
(Image forming apparatus 2)
In step S13, the conveyance speed of the paper P is determined based on the paper feed setting. In step S14, the formation range of the patch 201 is obtained. In step S <b> 15, the position where the patch 201 is formed is determined based on the formation range of the patch 201. In step S16, an operation for printing the patch 201 is started.

(Image reading device 3)
In step S17, the color of the facing surface of the backing 80 is switched from white to black. In step S18, the leading edge of the paper P is detected. In step S19, the color of the facing surface of the backing 80 is switched from black to white. In step S20, the patch 201 is read. In step S21, it is determined whether reading of the last patch 201_n is completed. If reading of the last patch 201_n is completed (YES in step S21), the process proceeds to step S22. If the reading of the last patch 201_n is not completed (NO in step S21), the process returns to step S20, and the patch 201 is read. In step S <b> 22, the reading result of the patch 201 is transmitted to the image processing unit 123. In step S23, it is determined whether or not a preset time has elapsed. If the preset time has elapsed (YES in step S23), the process proceeds to step S24. In step S24, the color of the facing surface of the backing 80 is switched from white to black.

  In step S25, it is determined whether or not the paper P on which the patch 201 is printed is conveyed. If the paper P on which the patch 201 is printed is not conveyed (NO in step S25), the process proceeds to step S26, and the patch 201 is printed. When the sheet P is conveyed (YES in step S25), the process returns to step S18, and the operation of detecting the leading end of the sheet P is executed again. In step S26, the normal print process is a process in which an image other than the patch 201 and the image position adjustment mark is printed on the paper P.

(Color and image position adjustment processing)
(Image forming apparatus 2)
In step S41, the conveyance speed of the paper P is determined based on the paper feed setting. In step S42, the formation range of the image position adjustment mark is obtained. In step S43, the formation range of the patch 201 is obtained. In step S44, the positions where the patch 201 and the image position adjustment mark are to be formed are determined based on the patch 201 formation range and the image position adjustment mark formation range. In step S45, the operation of printing the patch 201 and the image position adjustment mark is started.

(Image reading device 3)
In step S46, the color of the facing surface of the backing 80 is switched from white to black. In step S47, the leading edge of the paper P is detected. In step S48, the image position adjustment mark on the front end side is read. In step S49, the color of the facing surface of the backing 80 is switched from black to white. In step S50, the patch 201 is read. In step S51, it is determined whether reading of the last patch 201_n is completed. If reading of the last patch 201_n is completed (YES in step S51), the process proceeds to step S52. If the reading of the last patch 201_n is not completed (NO in step S51), the process returns to step S50, and the patch 201 is read. In step S52, it is determined whether or not a preset time has elapsed. If the preset time has elapsed (YES in step S52), the process proceeds to step S53.

  In step S53, the color of the facing surface of the backing 80 is switched from white to black. In step S54, the image position adjustment mark on the rear end side is read. In step S <b> 55, the result of reading the patch 201 and the image position adjustment mark is transmitted to the image processing unit 123. In step S56, it is determined whether or not the paper P on which the patch 201 is printed is transported. If the paper P on which the patch 201 is printed is not transported (NO in step S56), the normal print processing in step S26 of FIG. When the process shifts and the paper P on which the patch 201 is printed is conveyed (YES in step S56), the process returns to step S47, and the operation of detecting the leading edge of the paper P is executed again.

  After the color and image position adjustment process is completed, the process returns to step S26 in FIG. 11, and the normal print process is executed.

  From the above description, the image reading device 3 determines the formation range of the patch 201 formed on the paper P based on the position of the nip that suppresses the slackness of the paper P within the allowable range. Therefore, due to the positional relationship between the paper P and the nip, the slackness of the paper P is suppressed within the allowable range in the patch 201 formation range. That is, the patch 201 is formed in an area where the height fluctuation of the paper P is small. Therefore, since the color of the patch 201 is measured in an area where the height fluctuation of the paper P is small, the density of the color to be measured increases because the amount of reflected light changes greatly as the height of the paper P changes. You can avoid changing situations. As a result, the measurement environment is such that the color reading accuracy can be ensured with high accuracy.

  The color of the surface facing the reading device 55 formed on the backing 80 can be switched between black and white. Therefore, when the color is measured, if the color of the facing surface formed on the backing 80 is switched to white, the absolute value of the color can be measured accurately. Therefore, the formation range of the patch 201 formed on the paper P is determined based on the switching time until the color of the facing surface formed on the backing 80 is switched to white and the conveyance speed at which the paper P is conveyed. Then, when the color of the patch 201 is measured, the color of the opposing surface formed on the backing 80 can be white. Therefore, the absolute value of the color can be measured accurately.

  In other words, the absolute value of the color can be accurately measured in a measurement environment in which the color reading accuracy can be ensured with high accuracy. Therefore, highly accurate image correction can be performed.

  Further, since the nip is formed in each of the upstream side conveyance roller 91 on the upstream side of the reading device 55 and the downstream side conveyance roller 92 on the downstream side of the reading device 55, the nip is formed between the reading device 55 and the paper P. And the distance between the paper P and the backing 80 can be kept constant. Therefore, when the paper P passes through the reading device 55, the paper P does not flutter. Therefore, the height fluctuation of the paper P can be suppressed. Accordingly, the reading device 55 can read the paper P in an area where the height fluctuation of the paper P is small.

  Further, since the formation range of the patch 201 is determined within the nip distance between the upstream nip formed by the upstream transport roller 91 and the downstream nip formed by the downstream transport roller 92 in the nip. The patch 201 is formed at a position where the paper P does not flutter. Accordingly, the reading device 55 can read the patch 201 in an area where the height fluctuation of the paper P is small.

  Further, since the shape and size of the patch 201 are determined based on the reading range of the reading device 55 and the conveyance speed of the paper P, the printable range of the paper P can be effectively used. Thereby, the used number of sheets P can be reduced.

  Further, when the reading device 55 reads either the leading edge or the trailing edge of the sheet P, the color of the facing surface formed on the backing 80 is switched to black, so the leading edge and the trailing edge of the sheet P are switched. The density difference between the respective color densities and the color density of the opposing surface formed on the backing 80 can be increased. Therefore, the edge part of the paper P can be detected with high accuracy. Therefore, since the trigger for reading the paper P can be accurately determined, the colorimetric timing can be accurately determined. Thereby, the reading device 44 can measure the color of the patch 201 at the correct position.

  Further, the image position adjustment mark is formed in the margin between the leading edge of the paper P and the first patch 201_1 of the patches 201, or the trailing edge of the paper P and the rearmost patch 201_n of the patch 201. The color of the facing surface formed on the backing 80 is switched from black to white until the reading operation of the first patch 201_1 by the reading device 55 is started. In addition, the color of the facing surface formed on the backing 80 is switched from white to black before the reading device 55 starts the reading operation of the rear end portion of the paper P. Therefore, the color of the opposing surface formed on the backing 80 can be switched at an appropriate timing. Thereby, the image position adjustment mark and the patch 201 can be read accurately.

  In addition, when the reading device 55 reads the patch 201, the color of the facing surface formed on the backing 80 is switched to white. Therefore, the reading device 55 is in a state where the color of the facing surface formed on the backing 80 is white. Thus, the patch 201 is read. Thereby, the absolute value of the color can be accurately measured.

  In addition, while the color of the facing surface formed on the backing 80 is white, the formation range of the patch 201 is determined within the transport distance in which the paper P is transported according to the transport speed of the paper P. Therefore, the formation range of the patch 201 is determined within the minimum necessary range. Therefore, the paper P is not wasted. Thereby, the cost of the paper P and the color measurement time of the patch 201 can be reduced.

  The reading device 55 is a spectrocolorimeter 70 or a scanner 60. The scanner 60 is provided on the upstream side of the spectrocolorimeter 70 and reads the paper P along the width direction of the paper P. Since the reading result of the scanner 60 is corrected based on the reading result of the colorimeter 70, the image of the full width of the paper P can be corrected. As a result, the time required for adjusting the color of the image formed on the paper P can be shortened.

  The image forming apparatus 2 is provided on the upstream side of the image reading apparatus 3, and the image forming apparatus 2 sets the position of the nip that suppresses the slackness of the paper P within an allowable range and the color of the facing surface formed on the backing 80 to white. The formation range of the patch 201 is determined based on the switching time until switching to, and the transport speed at which the paper P is transported. Therefore, the image forming apparatus 2 can cause the image reading apparatus 3 to accurately measure the absolute value of the color in a measurement environment in which the color reading accuracy can be ensured with high accuracy. As a result, highly accurate image correction can be performed.

  Since the image forming apparatus 2 creates a color profile of the color of the image formed on the paper P based on the reading result of the paper P by the image reading device 3, the image color can be adjusted at an early stage. Accordingly, it is possible to improve the efficiency of adjusting the color of the image formed on the paper P.

  Image correction with high accuracy can be performed by the image forming system including the image reading apparatus 3 described above and the image forming apparatus 2 described above. Thereby, an image not inferior to offset printing can be formed on the paper P.

  Thus, according to the image reading device 3 according to the present embodiment, the reading device 55 that reads the paper P and the facing surface that is disposed to face the reading device 55 and that faces the reading device 55 are formed. A switching control unit 111 that switches the color of the facing surface of the backing 80 and the reading device 55 formed on the backing 80 to either black or white based on a trigger when the reading device 55 reads the paper P. The formation range of the patch 201 formed on the paper P includes the position of the nip that suppresses the slackness of the paper P within the allowable range, the switching time until the switching control unit 111 switches the color of the facing surface to white, and the paper P It is determined on the basis of the conveyance speed to be conveyed. Thereby, highly accurate image correction can be performed.

  In addition, the nip is formed in each of the upstream conveyance roller 91 on the upstream side of the reading device 55 and the downstream conveyance roller 92 on the downstream side of the reading device 55. Accordingly, the reading device 55 can read the paper P in an area where the height fluctuation of the paper P is small.

  Further, of the nips, the formation range of the patch 201 is determined within a nip distance between the upstream nip formed by the upstream transport roller 91 and the downstream nip formed by the downstream transport roller 92. It is. Accordingly, the reading device 55 can read the patch 201 in an area where the height fluctuation of the paper P is small.

  Further, the shape and size of the patch 201 are determined based on the reading range of the reading device 55 and the conveyance speed. Thereby, the used number of sheets P can be reduced.

  Further, the switching control unit 111 switches the color of the facing surface to black when the reading device 55 reads either the leading end portion or the trailing end portion of the paper P. Thereby, the reading device 44 can measure the color of the patch 201 at the correct position.

  Further, an image position adjustment mark serving as a reference for adjusting the position of the image formed on the paper P is formed. The image position adjustment mark is formed between the leading end of the paper P and the first patch 201_1 of the patches 201. The switching control unit 111 is formed at the margin between the rear end of the paper P and the margin between the rear end patch 201_n of the patches 201. The color of the opposing surface is switched from black to white until the reading operation 201_1 is started, and the color of the opposing surface is changed until the reading operation of the rear end portion of the paper P by the reading device 55 is started. It switches from white to black. Thereby, the image position adjustment mark and the patch 201 can be read accurately.

  The switching control unit 111 switches the color of the facing surface to white when the reading device 55 reads the patch 201. Thereby, the absolute value of the color can be accurately measured.

  In addition, while the color of the opposing surface is white, the formation range of the patch 201 is determined within the transport distance in which the paper P is transported according to the transport speed. As a result, the number of sheets used for adjustment can be reduced, the cost can be reduced, and the color measurement time of the patch 201 can be reduced.

  The reading device 55 is a spectrocolorimeter 70 or a scanner 60, and the scanner 60 is provided on the upstream side of the spectrocolorimeter 70 and reads the paper P along the width direction of the paper P. A line sensor 103 is provided, and the reading result of the scanner 60 is corrected based on the reading result of the spectrocolorimeter 70. As a result, the time required for adjusting the color of the image formed on the paper P can be shortened.

  The image forming apparatus 2 is provided on the upstream side of the image reading device 3, and includes an acquisition unit 121 that acquires a nip position, a switching time, and a conveyance speed, and a nip acquired by the acquisition unit 121. And an image processing unit 123 that determines the formation range of the patch 201 formed on the paper P based on the position, the switching time, and the conveyance speed. As a result, highly accurate image correction can be performed.

  The image processing unit 123 creates a color profile of the color of the image formed on the paper P based on the reading result of the paper P by the image reading device 3. Thereby, it is possible to improve the efficiency of adjusting the color of the image formed on the paper P.

  The image forming system also includes an image reading device 3 and an image forming device 2. Thereby, an image not inferior to offset printing can be formed on the paper P.

  The image processing apparatus according to the present invention has been described above based on the embodiments. However, the present invention is not limited to this, and modifications may be made without departing from the spirit of the present invention.

  For example, although an example in which two scanners 60 are provided has been described, the present invention is not limited thereto, and only one scanner 60 may be provided. In this case, it is only necessary to read the front and back of the paper P with a single scanner 60 by providing a conveyance path for inverting the paper P. Further, three or more scanners 60 may be provided.

  In addition, in the present embodiment, an example in which the color of the surface facing the reading device 55 formed on the backing 80 is switched to either black or white has been described. However, the present invention is not limited to this. It may be configured to switch to any one of the colors.

  In addition, an example of switching the color of the surface facing the reading device 55 formed on the backing 80 by rotating the backing 80 has been described. However, the present invention is not limited to this, and the backing 80 is a flat plate, and the black color is displayed on the flat plate. And white may be formed. In the case where the backing 80 is a flat plate, the color of the facing surface formed on the backing 80 may be switched between black and white by moving the flat plate in parallel.

  Further, although an example in which the image sensor is a CCD has been described, the present invention is not limited thereto, and the image sensor may be a CMOS.

DESCRIPTION OF SYMBOLS 1 Paper feeder 2 Image forming apparatus 3 Image reading apparatus 4 Paper discharge apparatus 10Y, 10M, 10C, 10K Image forming part 11Y, 11M, 11C, 11K Photosensitive drum 15 Intermediate transfer belt 16 Secondary transfer roller 20, 50 Paper conveyance Unit 21 paper feeding unit 22 paper feeding unit 23 paper discharge roller 24 switching gate 30 fixing device 45 operation panel 55 reading device 60, 60a, 60b scanner 70 spectrocolorimeter 80, 80a, 80b, 80c backing 101, 105 light source 103 CCD line sensor 107 Spectral imaging unit 91, 91a to 91c Upstream conveying roller 92, 92a to 92c Downstream conveying roller 111 Switching control unit 113 Timing unit 121 Acquisition unit 123 Image processing unit 201, 201_1 to 201_n Patch SC Document reading device P Paper

Claims (12)

A reading device for reading paper;
A backing disposed opposite the reading device and having a facing surface facing the reading device;
A switching control unit that switches a color of a surface facing the reading device formed on the backing to black or white based on an opportunity of the reading of the paper by the reading device;
With
The patch formation range formed on the paper includes the position of the nip that suppresses the slackness of the paper within an allowable range, the switching time until the switching control unit switches the color of the facing surface to white, and the paper An image reading apparatus that is determined based on a conveyance speed of conveyance.   2. The image according to claim 1, wherein the nip is formed on each of an upstream conveyance roller on an upstream side of the reading device and a downstream conveyance roller on a downstream side of the reading device. Reader.   Of the nips, the patch formation range is determined within a nip distance between an upstream nip formed by the upstream transport roller and a downstream nip formed by the downstream transport roller. The image reading apparatus according to claim 2.   The image reading apparatus according to claim 1, wherein the shape and size of the patch are determined based on a reading range of the reading apparatus and the conveyance speed.   5. The switch according to claim 1, wherein the switching control unit switches the color of the facing surface to black when the reading device reads either the leading edge or the trailing edge of the sheet. An image reading apparatus according to claim 1. An image position adjustment mark serving as a reference for adjusting the position of the image formed on the paper is formed,
The image position adjustment mark is a margin between the leading edge of the paper and the leading patch of the patch, or the trailing edge of the paper and the patch at the trailing edge of the patch. Is formed in the space between
The switching control unit switches the color of the facing surface from black to white until the reading operation of the leading patch by the reading device is started. The image reading apparatus according to claim 5, wherein the color of the facing surface is switched from white to black before the reading operation is started.   The image reading apparatus according to claim 1, wherein the switching control unit switches a color of the facing surface to white when the reading apparatus reads the patch.   The patch formation range is determined within a transport distance in which the paper is transported according to the transport speed while the color of the facing surface is white. An image reading apparatus according to claim 1. The reading device is a spectrocolorimeter or a scanner,
The scanner is provided on the upstream side of the spectrocolorimeter, and has a CCD line sensor that reads the paper along the width direction of the paper,
The image reading apparatus according to claim 1, wherein the reading result of the scanner is corrected based on the reading result of the spectrocolorimeter. An image forming apparatus provided on the upstream side of the image reading apparatus according to claim 1,
An acquisition unit for acquiring the position of the nip, the switching time, and the conveyance speed;
An image processing unit that determines a formation range of a patch to be formed on the paper based on the position of the nip, the switching time, and the conveyance speed acquired by the acquisition unit;
An image forming apparatus comprising:   The image forming unit according to claim 10, wherein the image processing unit creates a color profile of a color of an image formed on the paper based on a reading result of the paper by the image reading device. apparatus. An image reading apparatus according to any one of claims 1 to 9,
Provided on the upstream side of the image reading device, an acquisition unit that acquires the position of the nip, the switching time, and the conveyance speed, the position of the nip acquired by the acquisition unit, and the switching An image forming apparatus having an image processing unit that determines a formation range of a patch to be formed on the sheet based on time and the conveyance speed;
An image forming system comprising:

Images