imaging device

Abstract

An image forming apparatus includes an image forming unit configured to form an image on a sheet; a discharge conveyance path configured to discharge the sheet on which the image is formed by the image forming unit to the outside; a reverse conveyance path configured to reverse a conveyance direction of the sheet being conveyed and convey the sheet; a first conveyance path configured to guide the sheet conveyed from the image forming unit to the reverse conveyance path; a second conveyance path configured to guide the sheet reversed in the reverse conveyance path from the reverse conveyance path to the discharge conveyance path; and a reading unit configured to read the image of the sheet in the second conveyance path.

Description

TECHNICAL FIELD

[0001] The present application relates to an image forming apparatus including an image reading unit that reads an image on a sheet. BACKGROUND

[0002] Conventionally, in an image forming apparatus such as a printer or a multifunction peripheral that forms an image on a sheet, an image forming apparatus has been proposed that reads an image formed on a sheet and uses the result thereof for correction at the time of next image formation. In an image forming apparatus described in JP 2005-221582 A, a reading unit that reads a position of an image formed on a sheet is provided in a double-sided conveyance path that is used to reverse a sheet on which an image is formed on one side and convey the sheet again to an image forming unit, and an image forming position of a next sheet is corrected. Further, in image forming apparatuses described in JP 2013-54324 A and JP 2014-131205 A, a color sensor is provided on a conveyance path between an image forming unit and a reversing portion that reverses a sheet, an image of a color patch of a sheet is read by the color sensor to create a profile, and color adjustment is performed based on the profile.

[0003] For example, in a case where a reading unit is provided in a double-sided conveyance path as disclosed in JP 2005-221582 A, a sheet to be discarded is conveyed again to an image forming unit and passed through the image forming unit, and thus, a conveyance time until the sheet is discharged becomes long, and as a time of an adjustment process, first, becomes long. Further, for example, in a case where a reading unit is provided in front of a reversing portion as in JP 2013-54324 A and JP 2014-131205 A, when sheets are read continuously, it is necessary to widen a gap between sheets so that a next sheet does not interfere with a sheet being read, and as a time of an adjustment process, also becomes long. SUMMARY

[0004] Therefore, the present application provides an image forming apparatus that can prevent a processing time of reading images of a plurality of sheets from becoming long.

[0005] According to an aspect of the present application is an image forming apparatus including an image forming unit configured to form an image on a sheet; an ejection conveyance path configured to eject the sheet on which the image is formed by the image forming unit to the outside; a reverse conveyance path configured to reverse a conveyance direction of the sheet being conveyed and convey the sheet; a first conveyance path configured to guide the sheet conveyed from the image forming unit to the reverse conveyance path; a second conveyance path configured to guide the sheet reversed in the reverse conveyance path from the reverse conveyance path to the ejection conveyance path; and a reading unit configured to read the image of the sheet in the second conveyance path.

[0006] Other features of the present application will become apparent from the following description of exemplary embodiments thereof, taken together with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 is a schematic view of an image forming apparatus according to the present embodiment.

[0008] Figure 2 is a schematic view showing a structure of a color sensor.

[0009] Figure 3 is a block diagram showing a control configuration of an image forming apparatus.

[0010] Figure 4 is a diagram for explaining an ICC profile.

[0011] Figure 5 is a schematic view showing a color management environment.

[0012] Figure 6 is a flowchart showing control of a color matching job according to the present embodiment.

[0013] Figure 7 is a diagram of sheet conveyance in a color matching job according to the present embodiment.

[0014] Figure 8 is a schematic view of an image forming apparatus according to a first comparative example.

[0015] Figure 9 is a diagram of sheet conveyance in a color matching job according to the first comparative example.

[0016] Figure 10 is a schematic view of an image forming apparatus according to a second comparative example. DETAILED DESCRIPTION

[0017] Hereinafter, an image forming apparatus according to each embodiment will be described with reference to the drawings. The sizes, materials, shapes, relative arrangements, and the like of the components described in the following embodiments are not intended to limit the scope of application of the present technology to only these descriptions unless otherwise specified.

[0018] Schematic configuration of image forming apparatus

[0019] Figure 1 is a schematic view showing an image forming apparatus 100 according to the present embodiment. In the present embodiment, the image forming apparatus 100, which is an electrophotographic laser beam printer, is described as an example of an image forming apparatus, but the present application is not limited thereto, and the image forming apparatus can be an inkjet printer or a sublimation printer.

[0020] A housing 101 of the image forming apparatus 100 is provided with an image forming engine 102 and a control board storage portion (not shown) that accommodates a printer controller 103 (see Figure 3 ), which is a control unit for controlling the operation of the image forming apparatus 100. The image forming engine 102, which is an image forming unit, includes an optical processing mechanism 10 and a fixing processing mechanism 20 that form an image on a recording material through an image forming process, and a feeding processing mechanism 30 and a conveying processing mechanism 40 that feed and convey a rectangular sheet 1 serving as a recording material. As the recording material, a paper sheet such as regular paper or thick paper, a surface-treated paper such as coated paper or embossed paper, a plastic film, cloth, or the like can be used.

[0021] The optical processing mechanism 10 includes stations 120, 121, 122, and 123 that form toner images of respective colors of yellow, magenta, cyan, and black, and an intermediate transfer belt 106. In each of the stations 120 to 123, a primary electrostatic charger 111 charges a surface of a photosensitive drum 105, which is a drum-shaped photosensitive member. A laser scanner unit 107 performs an exposure process of the photosensitive drum 105 according to a command signal generated based on image data and transmitted to the laser scanner unit 107. The laser scanner unit 107 includes a laser driver that drives the opening and closing of laser light emitted from a semiconductor laser (not shown). The laser scanner unit 107 guides a laser beam from the semiconductor laser to the photosensitive drum 105 via a mirror 109 while distributing the laser beam in a main scanning direction (a sheet width direction) by a rotating polygon mirror. Thus, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 105.

[0022] The developer containing toner is housed in the developer 112, and charged toner particles are supplied to the photosensitive drum 105. The toner particles adhere to the surface of the drum according to the surface potential distribution, whereby the latent image carried on the photosensitive drum 105 is visualized as a toner image. The toner image carried on the photosensitive drum 105 is transferred (primary transfer) to the intermediate transfer belt 106 to which a voltage of a polarity opposite to that of the normal charge of the toner is applied. In the case of forming a color image, the toner images formed by the four stations 120 to 123 are multiple-transferred in a manner of overlapping each other on the intermediate transfer belt 106, whereby a full-color toner image is formed on the belt.

[0023] On the other hand, the feeding processing mechanism 30 feeds the sheet 1 from the sheet storage 113, which is inserted into the housing 101 of the image forming apparatus 100 in a drawable manner, to the transfer roller 114 one sheet at a time. The toner image carried on the intermediate transfer belt 106 as an intermediate transfer member is transferred (secondary transfer) to the sheet 1 by the transfer roller 114.

[0024] An image start position detection sensor 115 for determining a print start position at the time of image formation, a feeding timing sensor 116 for setting the feeding timing of the sheet 1, and a density sensor 117 are provided on the periphery of the intermediate transfer belt 106. The density sensor 117 measures the density of a test patch image carried on the intermediate transfer belt 106. The printer controller 103 adjusts the operation conditions of the optical processing mechanism 10 (for example, the setting of the charge target potential of the primary electrostatic charger 111 and the bias voltage of the developer 112) based on the detection result of the density sensor 117.

[0025] The fixing processing mechanism 20 of the present embodiment includes a fixing unit 150 and a cooling unit 160. The fixing unit 150 includes a fixing roller 151 for applying heat to the sheet 1, a pressurizing belt 152 for pressing the sheet 1 against the fixing roller 151, and a post-fixing sensor 153 for detecting the completion of the fixing processing by the fixing unit 150. The fixing roller 151 is a hollow roller and includes a heater inside. The fixing unit 150 applies heat and pressure to the toner image on the sheet while sandwiching and conveying the sheet 1 by the fixing roller 151 and the pressurizing belt 152 as a pair of rotating members. Thus, the toner particles melt and then fix, thereby fixing the image on the sheet 1.

[0026] A cooling unit 160 is provided downstream of the fixing unit 150 in the sheet conveyance direction, and its purpose of the provision is to reduce the temperature of the sheet 1 fixed by the fixing unit 150 to reduce the heat supply from the sheet 1 to the image forming section and to reduce the amount of curling of the product, particularly in double-sided printing. The cooling unit 160 includes a roller 161, a roller 162, and a post-cooling sensor 163 that detects the completion of the cooling process by the cooling unit 160. The cooling unit 160 grips the sheet 1 with a nip formed by the roller 161 and the roller 162 to transfer heat of the sheet 1 to the roller 161 and the roller 162. The heat transferred to the roller 161 and the roller 162 is dissipated by a cooling fan (not shown).

[0027] The sheet 1 that has passed through the cooling unit 160 is guided from the conveyance path 131 to the discharge conveyance path 139 via the discharge pre-conveyance path 142 as a fourth conveyance path or to the reversal pre-conveyance path 133 as a first conveyance path by the first switching baffle 132 (second switching unit). The sheet 1 carried into the reversal pre-conveyance path 133 passes through the second switching baffle 134 and is guided to the reversal conveyance path 135. The sheet 1 carried into the reversal conveyance path 135 is guided toward the standby path 138 by the first reversal conveyance roller 171 and / or the second reversal conveyance roller 172 as a reversal conveyance unit, while the position of the sheet 1 is detected by the reversal sensor 137.

[0028] In the case of double-sided printing, based on the detection by the reversal sensor 137, the sheet 1 on the front surface of which an image is formed is carried into the standby path 138 until the trailing edge thereof passes through the third switching baffle 136 (first switching unit). Then, the leading end (front edge) and the trailing end (trailing edge) of the sheet are exchanged by a turn-back operation performed by the second reversal conveyance roller 172. In the state where the front edge and the trailing edge of the sheet are switched by the second reversal conveyance roller 172, the sheet is guided again toward the transfer roller 114 via the re-conveyance path 140 as a third conveyance path by the third switching baffle 136, and an image is formed on the back surface of the sheet opposite to the front surface thereof.

[0029] Then, the sheet 1 of which the image formation in the single-sided printing has been completed or the sheet 1 of which the image formation in the back surface in the double-sided printing has been completed is guided to the discharge conveyance path 139 via the discharge pre-conveyance path 142. The sheet 1 conveyed to the discharge conveyance path 139 is discharged onto the discharge tray 700 provided outside the image forming apparatus 100 by the discharge roller 139a as a discharge unit.

[0030] On the other hand, when the sheet 1 that has passed through the cooling unit 160 is reversed and discharged (when a color matching job to be described later is performed), the sheet 1 on the front surface of which the image is formed is guided to the reverse front conveyance path 133. Thereafter, based on the detection of the reverse sensor 137, the sheet is carried into the reverse conveyance path 135 and the standby path 138 until the trailing edge thereof passes through the second switching damper 134. The reverse conveyance path 135 and the standby path 138 are reverse conveyance paths in the present embodiment. Then, by a turn-back operation performed by the first reverse conveyance roller 171, the downstream end (leading edge) and the upstream end (trailing edge) of the sheet in the sheet conveyance direction are exchanged. The sheet 1 of which the leading edge and the trailing edge have been switched by the first reverse conveyance roller 171 is guided by the second switching damper 134 to the reverse rear conveyance path 141 that is a second conveyance path connecting the reverse conveyance path 135 and the discharge conveyance path 139, and is subsequently guided toward the discharge conveyance path 139. Then, the sheet 1 that has been conveyed to the discharge conveyance path 139 after the front surface and the rear surface thereof are reversed in this way is discharged to the discharge tray 700 provided outside the image forming apparatus 100 with the front surface and the rear surface thereof reversed by the discharge roller 139a. That is, the reverse rear conveyance path 141 can also be said to be a conveyance path dedicated to discharge in the case where the reversed sheet 1 is discharged without performing double-sided printing.

[0031] Configuration of color sensor

[0032] Next, the arrangement and structure of the color sensor 200 in the color measurement unit 500 will be described with reference to Figure 1 and Figure 2 The color sensor 200 is a color sensor that reads the color of the image on the front surface of the sheet 1 conveyed on the reverse rear conveyance path 141. Figure 2 is a schematic view showing the structure of the color sensor. The color measurement unit 500 that reads the image on the front surface of the reversed sheet 1 conveyed on the reverse rear conveyance path 141 is provided along the reverse rear conveyance path 141. The color measurement unit 500 includes the color sensor 200 as a reading unit that reads the image of the sheet 1.

[0033] As Figure 2As shown, the color sensor 200 includes: a white LED 201 that illuminates a color patch image 1P on a sheet 1, the color patch image 1P comprising a large number of color patches formed as a test image; and a diffraction grating 202 that disperses light reflected from the color patch image 1P for each wavelength. Additionally, the color sensor 200 includes a lens 206 that converges light emitted from the white LED 201 onto the color patch image 1P on the sheet 1 and converges light reflected from the color patch image 1P onto the diffraction grating. Furthermore, the color sensor 200 is provided with line sensors 203 (203-1 to 203-n), which are CMOS sensors comprising n pixels that detect light decomposed by the diffraction grating 202 for each wavelength. The color sensor 200 includes a computing unit 204 that performs various calculations based on the light intensity value of each pixel detected by the line sensors 203, and a memory 205 that stores various data. It should be noted that the color measurement unit 500 includes an A / D converter and sends the color measurement results to a digital signal. Figure 3 The printer controller 103 in the middle.

[0034] It should be noted that the pixel information of line sensor 203 from 1 to n has the same relationship with the spectral wavelength. Ideally, n = 41 or greater is needed to achieve a final detection result with 10nm resolution from 380nm to 780nm. To ensure consistency between wavelength and pixel count, considering adjustment range, 48 or 64 pixels are suitable. Alternatively, a simpler configuration could be conceived that reduces the number of pixels and calculates the insufficient wavelength through interpolation. This simpler configuration can be used, but detection accuracy will be reduced.

[0035] Control configuration of imaging equipment

[0036] Next, we will refer to Figures 3 to 5 Describes the control of the imaging device 100. Figure 3 This is a diagram showing the control configuration of the imaging device. Figure 4 It is a diagram used to illustrate the ICC configuration file, and Figure 5 This is a schematic diagram illustrating a color management environment. The host computer 300 and the imaging device 100 are connected via a communication line such as USB 2.0 high-speed or LAN.

[0037] In the image forming apparatus 100, the printer controller 103 controls the overall operation of the printer. In addition, the printer controller 103 is connected to the I / F 308 that controls the input / output of the host computer 300, the operation unit 180, the color sensor 200, and the engine control unit 312. In addition, the printer controller 103 includes a ROM 320 in which control programs and control data are contained, and a CPU and a RAM (not shown). Each control program of the ROM 320 constitutes a raster image processor (RIP) processing unit 314 that decompresses an image object into a bit map image. In addition, each control program of the ROM 320 constitutes a color processing unit 315 that performs a color conversion process of a multi-level color described later, a gradation correction table generating unit 316 that performs a gradation correction of a single color, a multi-level color table generating unit 317 that reflects a correction result of a multi-level color, and a maximum density condition determining unit 318.

[0038] The engine control unit 312 causes the image forming engine 102 to perform the above-described image forming process to form an image on a sheet based on a command signal from the printer controller 103 or the like. For example, the engine control unit 312 receives detection signals of the post-fixing sensor 153, the post-cooling sensor 163, and the reversal sensor 137. Then, based on these detection signals, the engine control unit 312 controls the operation of the conveyance motor 311 that drives a roller that conveys a sheet, the first switching damper 132, the second switching damper 134, and the third switching damper 136.

[0039] The image forming apparatus 100 is provided with the operation unit 180 (see Figure 1 ) that functions as a user interface. The operation unit 180 includes a display that is a display unit that displays information to a user. In addition, the operation unit 180 includes, for example, physical keys such as a numeric keypad and a print execution button, and a touch panel function of the display, which are input units through which a user can input a command and data to the image forming apparatus 100. By operating the operation unit 180, a user can input information indicating a sheet attribute, such as a name, a grammage, and the presence or absence of a surface treatment of a sheet set in a certain sheet storage 113 (see Figure 1 ) to the printer controller 103.

[0040] Color adjustment in image formation

[0041] Next, imaging color adjustment when the color sensor 200 measures the color of the patch image 1P of the sheet 1 will be described in detail. That is, the control flow for creating a color profile and outputting an image using the color profile in the image forming apparatus 100 according to the present embodiment will be described. The process of creating a color profile is performed by the printer controller 103. First, a profile creation instruction is input to the profile creation unit 301 via the operation unit 180. The profile creation unit 301 sends a cyan, magenta, yellow, black (CMYK) color chart of the test format of ISO 12642 to the image forming engine 102 so as to output the CMYK color chart without a profile. At the same time, a colorimetric instruction is sent to the color sensor control unit 302.

[0042] In the image forming apparatus 100, the test format of ISO 12642 is transferred and fixed to the sheet 1 as the patch image 1P by processes such as charging, exposure, development, transfer, and fixation, and color measurement is performed by the color sensor 200 of the color measurement unit 500. The spectral reflectance data of the 928 patches after color measurement are input to the printer controller 103 and converted into L*a*b* data via the Lab calculation unit 303. Then, the L*a*b* data are stored in the input ICC profile storage unit 304 for the color sensor as a color setting table, and input to the profile creation unit 301. Instead of the L*a*b* data, the spectral reflectance data can be converted into the CIE1931 XYZ color system, which is a device-independent color space signal.

[0043] Further, the profile creation unit 301 creates an output ICC profile based on the relationship between the output CMYK signal and the input L*a*b* data, and performs updating to replace the output ICC profile stored in the output ICC profile storage unit 305.

[0044] The test format of ISO 12642 includes CMYK color signal patches covering the color reproduction range that can be output by a general copier, and a color conversion table is created according to the relationship between each color signal value and the L*a*b* value of color measurement. That is, a conversion table of CMYK→Lab (A2Bx tag) is created. An inverse conversion table (B2Ax tag) is created based on the conversion table.

[0045] The ICC profile has a structure as shown in Figure 4 and includes a header, tags, and data thereof. In the tags, not only the above-described color conversion table, but also a white point (Wtpt), a gamt tag describing whether a certain color represented by an L*a*b* value defined in the profile is within the reproducible reproduction range of a hard copy or not, and the like are described.

[0046] Note that if the profile creation command is an input from the external device or the like of the I / F 308, an output ICC profile created by the external device that sent the command can be uploaded, and the user can perform color conversion in an application corresponding to the ICC profile.

[0047] In color conversion in normal color output, an image signal input in accordance with an RGB signal value input via the external I / F 308 such as a scanner unit or in accordance with a standard print CMYK signal value such as Japanese color is sent to the input ICC profile storage unit 307. In the input ICC profile storage unit 307, RGB→L*a*b*or CMYK→L*a*b*conversion is performed in accordance with the image signal input from the external I / F 308. The input ICC profile includes a one-dimensional look-up table (LUT) that controls the gamma of the input signal, a multi-order color LUT called direct mapping, and a one-dimensional LUT that controls the gamma of the generated conversion data. By using these tables, the color space dependent on the device is converted to L*a*b*data that is not dependent on the device.

[0048] The image signal converted to L*a*b*colorimetric coordinates is input to the color management module (CMM) 306. Then, GAMUT conversion for mapping the mismatch between the read color space of the external I / F 308 such as a scanner unit that is the input device and the output color reproduction range of the image forming apparatus 100 that is the output device is performed. Further, color conversion for adjusting the light source type mismatch (also called color temperature setting mismatch) at the time of observation of the input and the output, black character determination, and the like are also performed. Thus, the L*a*b*data is converted to L*'a*'b*'data and is input to the output ICC profile storage unit 305. The profile created as described above is stored in the output ICC profile storage unit 305, color conversion is performed by the newly created ICC profile, conversion to a CMYK signal is performed depending on the output device, and output is performed.

[0049] A configuration in which the CMM 306, the input ICC profile storage unit 307, and the ICC output profile storage unit 305 are separated from each other has been described in terms of block configuration. However, as Figure 5 indicated, the CMM is a module that manages color management, and is a module that performs color conversion using an input profile and an output profile.

[0050] The maximum density condition determination unit 318, the gradation correction table generation unit 316, and the multi-step color table generation unit 317 that reflects the correction result of the multi-step color manage and update the ICC profile, the γLUT, and the Vcont information used at the time of imaging. That is, the desired color can be output by changing (reflecting) each table by the color processing unit 315, the multi-step color table generation unit 317, and the like.

[0051] Operation of the color matching job

[0052] Next, the control of the color matching job as an adjustment process of color adjustment in the present exemplary embodiment and the conveyance state of the plurality of sheets in the color matching job will be described with reference to Figure 6 and Figure 7 Figure 6 is a flowchart showing the control of the color matching job according to the present embodiment, and Figure 7 is a view of the sheet conveyance in the color matching job according to the present embodiment. Note that, Figure 7 shows the position of each sheet 1 when three consecutive sheets 1 are conveyed at the time of execution of the color matching job.

[0053] For example, when the color matching job such as color profile creation is specified by the user operation from the operation unit 180, the printer controller 103 starts Figure 6 the control shown in FIG. 8 (S1). As shown in Figure 6 and Figure 7 , first, the feeding operation of the sheet 1 is started, and the sheet 1 is fed from the sheet storage 113 to the transfer roller 114 (S2). On the other hand, in the image forming engine 102, a test pattern toner image is formed on the intermediate transfer belt 106, and is transferred to the fed sheet 1 as a patch image IP for creating a color profile (S3). Then, after the patch image is fixed by the fixing unit 150, the sheet is cooled by the cooling unit 160 (S4), and the imaging is completed. At this time, the sheet 1 is conveyed through the transfer roller 114, the fixing unit 150, and the cooling unit 160 at a conveyance speed of 600 mm / sec as an imaging processing speed.

[0054] Thereafter, when the trailing edge of the sheet 1 passes through the cooling unit 160, the sheet 1 is conveyed toward the pre-reversal conveyance path 133, the reversal conveyance path 135, and the standby path 138 at a conveyance speed of 1500 mm / sec (first conveyance speed) as an increase in the reversal stretch speed. After the leading edge of the sheet 1 passes through the reversal sensor 137, the timer count corresponding to the length of the sheet 1 is started (S5). Then, when the timer becomes 0, the trailing edge of the sheet 1 is positioned beyond the second switching damper 134, and thus the conveyance of the sheet 1 is stopped, that is, the sheet 1 is conveyed to the reversal conveyance path 135 and the standby path 138, and the sheet is made to stand by (S6). ​

[0055] Subsequently, once the sheet 1 is stopped in the reverse conveying path 135 and the standby path 138, the first reverse conveying roller 171 reverses the conveying direction of the sheet 1, and the second switching baffle 134 resumes conveying toward the post-reversal conveying path 141 (S7, see Figure 7 ). At this time, the conveying speed is increased (S8), and the sheet is conveyed to the position of the color sensor 200 of the color measurement unit 500 at a conveying speed of 1500 mm / sec as a post-reversal speed. Then, immediately before the leading edge of the sheet 1 reaches the reading position of the color sensor 200, the conveying speed is decelerated to 300 mm / sec (second conveying speed) as a reading speed (S9), and the sheet 1 is conveyed to the color sensor 200 at this speed (S10).

[0056] At this time, the counting of a timer for determining the start time of conveying of the subsequent sheet 1 is started (Sll), and the timing at which the interval between the leading edge of the subsequent sheet 1 and the trailing edge of the preceding sheet 1 becomes as small as possible is measured at the reading position of the color sensor 200. Then, when the counting of the timer ends, the feeding of the subsequent sheet 1 is allowed (S12). In the absence of the subsequent sheet 1 (Y in S17 to be described later), only the flag allowing the feeding is turned on, and the feeding is not actually performed.

[0057] On the other hand, when the sheet 1 is conveyed to the reading position of the color sensor 200, color detection (colorimetry) of the color patch image IP is performed by the reading operation of the color sensor 200 (S13). When the reading of the color sensor 200 is completed up to the trailing end of the color patch image IP drawn on the sheet, the conveying speed is increased to a conveying speed of 1500 mm / sec as a sheet discharge speed, so as to quickly discharge the sheet 1 (S14). Then, the sheet 1 is discharged to the discharge tray 700 by the discharge roller 139a (S15). The color measurement result obtained by reading the color patch image IP is sent to the Lab calculation unit 303, converted to L*a*b* data, stored in the input ICC profile storage unit 304 for the color sensor as a color setting table, and input to the profile creation unit 301 (S16).

[0058] As described above, at the end of the reading operation of the color patch image IP on the current sheet 1, it is determined whether the color measurement of the necessary number of sheets has been completed (S17), that is, it is determined whether the color measurement of 928 color patches required for creating the color profile has been completed. When the color measurement of 928 color patches required for creating the color profile has not been completed (N in S17), the feeding of the subsequent sheet 1 is started. Thus, the continuation of the color patches that have not yet been subjected to the color measurement is formed on the subsequent sheet 1, and the same reading operation is performed on the subsequent sheet 1. Then, when the color measurement of 928 color patches required for creating the color profile has been completed (Y in S17), the control ends (S18), that is, the colorimetric job is completed.

[0059] Summary of the Embodiment

[0060] In the present embodiment, as described above, the color sensor 200 is provided along the reverse post-conveying path 141 that connects the standby path 138 to the discharge conveying path 139. Then, the timing of feeding the sheet 1 is controlled so that the leading edge of the subsequent sheet 1 is conveyed to the reading position of the color sensor 200 at the timing when the trailing edge of the front sheet 1 passes the reading position of the color sensor 200. At this time, as shown in FIG. 6, the front sheet 1 is read by the color sensor 200 while the subsequent sheet 1 is conveyed to the reverse conveying path 135. Thus, at the reading position of the color sensor 200, the trailing edge of the front sheet 1 and the leading edge of the subsequent sheet 1 can be brought close to each other. Thus, as shown in FIG. 7, the color measurement of the color patches of the subsequent sheet 1 can be started immediately after the color measurement of the color patches of the front sheet 1 is completed. Figure 7 Figure 7 Thus, as shown in FIG. 8, the color measurement of the color patches of the subsequent sheet 1 can be completed immediately after the color measurement of the color patches of the front sheet 1 is completed. Thus, as shown in FIG. 9, the color measurement of the color patches of the third sheet 1 can be started immediately after the color measurement of the color patches of the second sheet 1 is completed. Thus, as shown in FIG. 10, the color measurement of the color patches of the third sheet 1 can be completed immediately after the color measurement of the color patches of the second sheet 1 is completed. Thus, as shown in FIG. 11, the color measurement of the color patches of the fourth sheet 1 can be started immediately after the color measurement of the color patches of the third sheet 1 is completed. Thus, as shown in FIG. 12, the color measurement of the color patches of the fourth sheet 1 can be completed immediately after the color measurement of the color patches of the third sheet 1 is completed. Thus, as shown in FIG. 13, the color measurement of the color patches of the fifth sheet 1 can be started immediately after the color measurement of the color patches of the fourth sheet 1 is completed. Thus, as shown in FIG. 14, the color measurement of the color patches of the fifth sheet 1 can be completed immediately after the color measurement of the color patches of the fourth sheet 1 is completed. Thus, as shown in FIG. 15, the color measurement of the color patches of the sixth sheet 1 can be started immediately after the color measurement of the color patches of the fifth sheet 1 is completed. Thus, as shown in FIG. 16, the color measurement of the color patches of the sixth sheet 1 can be completed immediately after the color measurement of the color patches of the fifth sheet 1 is completed. Thus, as shown in FIG. 17, the color measurement of the color patches of the seventh sheet 1 can be started immediately after the color measurement of the color patches of the sixth sheet 1 is completed. Thus, as shown in FIG. 18, the color measurement of the color patches of the seventh sheet 1 can be completed immediately after the color measurement of the color patches of the sixth sheet 1 is completed. Thus, as shown in FIG. 19, the color measurement of the color patches of the eighth sheet 1 can be started immediately after the color measurement of the color patches of the seventh sheet 1 is completed. Thus, as shown in FIG. 20, the color measurement of the color patches of the eighth sheet 1 can be completed immediately after the color measurement of the color patches of the seventh sheet 1 is completed.

[0061] Further, when the images of a plurality of sheets 1 are read, by making the reading speed, which is the conveying speed of the sheets, slower than the reverse stretching speed, the post-reverse speed, and the discharge speed, the reading accuracy is not impaired. Further, for example, when the sheet 1 is conveyed to the re-conveying path 140 and the reading operation is performed in the re-conveying path 140, the sheet 1 is conveyed to the discharge conveying path 139 after passing the transfer roller 114, the fixing unit 150, and the cooling unit 160 again, and thus, the conveying time becomes long. However, in the present embodiment, since the sheet 1 can be immediately conveyed from the post-reverse conveying path 141 to the discharge conveying path 139, it is possible to prevent the time of the colorimetric job of reading the images of a plurality of sheets 1 from becoming long. Thus, it is possible to shorten the time of the colorimetric job as an adjustment process, and it is possible to improve the productivity. In other words, it is possible to provide an image forming apparatus with high color stability and high operability.

[0062] First Comparative Example

[0063] Next, the present embodiment will be compared with the first comparative example, and it will be described that the time of the colorimetric job in the present embodiment is shortened.​Figure 8 It is based on a schematic diagram of the imaging device of the first comparative example, and Figure 9 This is a diagram of sheet feeding during the colorimetric operation based on the first comparative example.

[0064] like Figure 8 As shown, in the first comparative example, the color measurement unit 500 (color sensor 200) is arranged downstream of the third switching baffle 136 in the sheet transport direction before reversal, that is, near the entrance of the standby path 138. Therefore, by transporting the sheet 1 to the standby path 138, all color patch images 1P of the sheet 1 can be read.

[0065] However, the assumed length of sheet 1 in the conveying direction is the length by which the leading edge of sheet 1 reaches the reading position of color sensor 200 before the trailing edge of sheet 1 passes through cooling unit 160. Therefore, as described above, after the trailing edge of sheet 1 passes through cooling unit 160, the conveying speed cannot be increased to a conveying speed of 1500 mm / sec, which is the reverse stretching speed.

[0066] Furthermore, the moment when the conveying speed decreases from 600 mm / sec, which is the imaging processing speed, to 300 mm / sec, which is the reading speed, occurs immediately before the leading edge of the sheet 1 reaches the reading position of the color sensor 200 (S9).

[0067] Therefore, the time when the color block image 1P of the first sheet 1 is read is earlier than the time in this embodiment. However, in order to transport the subsequent sheet 1 to the color sensor 200, the subsequent sheet 1 needs to be transported after the trailing edge of the preceding sheet 1 passes through the second switching baffle 134, so that there is no collision between the sheets. Therefore, the start of the reading operation of the subsequent sheet 1 is delayed. Figure 9 The time difference dT is shown. For these reasons, the processing time T2 required to complete the colorimetric work on multiple sheets 1 in the first comparative example (see...) Figure 9 Compared to the operation time T1 in this embodiment (see...) Figure 7 )slow.

[0068] Second Comparative Example

[0069] Next, we will refer to Figure 10 Describe the second comparative example. Figure 10 This is a schematic diagram of the imaging device according to the second comparative example.

[0070] like Figure 10In the second comparative example, as shown, the color measurement unit 500 (color sensor 200) is arranged along the discharge conveying path 139 upstream of the discharge roller 139a in the sheet conveying direction. In the second comparative example, the sheet 1 does not need to be pulled into the pre-reversal conveying path 133, the reversal conveying path 135, and the post-reversal conveying path 141 at all, and it is sufficient to convey the sheet to the pre-discharge conveying path 142 and the discharge conveying path 139. However, the sheet 1 needs to be conveyed at a conveying speed of 600 mm / sec, which is the image forming processing speed, until the trailing edge of the sheet 1 passes through the cooling unit 160. However, on the other hand, the conveying speed needs to be decelerated to 300 mm / sec, which is the reading speed, so as not to impair the reading accuracy of the color patch image 1P. Therefore, it is necessary to lengthen the discharge conveying path 139 (or the pre-discharge conveying path 142) so that the leading edge of the sheet 1 reaches the reading position of the color sensor 200 after the trailing edge of the sheet 1 passes through the cooling unit 160. Therefore, the width of the image forming apparatus 100 increases as shown by the arrow W. Therefore, the image forming apparatus 100 according to the present embodiment can be downsized compared to the second comparative example.

[0071] Possibilities of other embodiments

[0072] In the present embodiment, an image forming apparatus using a spectral color sensor as a color sensor has been described. However, a compact image sensor typified by a contact image sensor (CIS) can be used as a reading unit. Even in this case, since it is necessary to decelerate the conveying speed at the time of image reading to ensure the reading accuracy, the same control is performed for colorimetric job of reading a plurality of sheets.

[0073] Further, in the present embodiment, an image forming apparatus including the re-conveying path 140 has been described, but the re-conveying path 140 can not be provided in an image forming apparatus that exclusively performs single-sided printing. Further, in the present embodiment, an image forming apparatus including the pre-discharge conveying path 142 has been described, but the pre-discharge conveying path 142 can also not be provided in an image forming apparatus that always reverses and discharges a sheet.

[0074] Further, in the present embodiment, an image forming apparatus in which the color patch image includes a large number of color patches has been described, but calibration can be performed by reading a black-and-white patch image.

[0075] In the present embodiment, an image forming apparatus in which the reading speed is slower than the image forming processing speed has been described. However, the speed relationship can be any speed relationship as long as an image can be accurately formed and the reading accuracy can be maintained.

[0076] In the present embodiment, an image forming apparatus in which the sheet 1 is reversed by the first reversal conveying roller 171 in the colorimetric job has been described, but the present application is not limited thereto, and the sheet 1 can be reversed by the second reversal conveying roller 172.

[0077] According to the present application, by slowing down the conveying speed of the sheet material when reading the images of the plurality of sheet materials, it is possible to prevent the time of processing of reading the images of the plurality of sheet materials from becoming longer without reducing the reading accuracy.

[0078] While the application has been described with reference to example embodiments, it is to be understood that the application is not limited to the disclosed example embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An imaging device, comprising: An imaging unit configured to form an image on a sheet; The discharge conveyor path is configured to discharge the sheet from which the image is formed by the imaging unit to the outside; A reverse conveyor path is configured to reverse the conveying direction of the conveyed sheet and convey the sheet. A first transport path is configured to guide the sheet transported from the imaging unit to the reverse transport path; A second conveying path is configured to guide the sheet reversed in the reverse conveying path from the reverse conveying path to the discharge conveying path; A switching unit is configured to switch between conveying the sheet from the first conveying path to the reverse conveying path and conveying the sheet from the reverse conveying path to the second conveying path; and A reading unit is disposed on the second transport path and configured to read an image of the sheet that has been transported from the reverse transport path to the second transport path via the switching unit.

2. The imaging device according to claim 1, further comprising: A third transport path is configured to guide a sheet that has been reversed in the reverse transport path from the reverse transport path to the imaging unit; as well as A first switching unit is configured to switch the conveying path on which the sheet being reversed in the reverse conveying path is conveyed to either the third conveying path or the second conveying path.

3. The imaging device according to claim 2, further comprising: A fourth transport path is configured to guide the sheet transported from the imaging unit to the discharge transport path; as well as The second switching unit is configured to switch the transport path on which the sheet being transported from the imaging unit is transported to either the first transport path or the fourth transport path.

4. The imaging device according to claim 1, further comprising: A control unit is configured to cause the imaging unit to form test images on a plurality of sheets in continuous transport, and to cause the reading unit to read the test images on the plurality of sheets in continuous transport, and to correct the image to be formed on the sheets by the imaging unit based on the read test images.

5. The imaging device according to claim 4, wherein The imaging unit is configured to form a color test image, and The reading unit includes a color sensor that reads the colors of the test image.

6. The imaging device according to claim 1, further comprising: A control unit is configured to, when the reading unit reads images of multiple sheets being continuously conveyed, control the conveying speed of the sheets to a second conveying speed, which is lower than a first conveying speed that is the conveying speed in the first conveying path.

7. The imaging device according to claim 6, wherein The control unit is configured to control the second transport speed to be lower than the imaging processing speed at which an image is formed on the sheet in the imaging unit.

8. The imaging device according to claim 6, wherein The control unit is configured to transport the sheet at the second transport speed while reading an image of the sheet so as to transport the sheet in the second transport path.

9. The imaging device according to claim 1, wherein While the first sheet is being read by the reading unit, a second sheet adjacent to the first sheet and to be read by the reading unit is configured to arrive at the reverse transport path.

Images