Color measurement unit, image forming apparatus

Abstract

To avoid dirt on a reference surface with a simple configuration.SOLUTION: A white reference plate 800 has a reference surface 800a that is arranged outside a paper feed area R1 and is substantially the same plane as a conveyance guide surface 810a. A color sensor 501 is driven by a driving unit 570 and movable in a movement direction B, and measures the color of an image for measurement formed on a sheet S. Elevating rollers 555 each move with the color sensor 501 to press down the sheet S. An override member 820 is provided which is higher than the reference surface 800a of the white reference plate 800. When the color sensor 501 moves in an area where at least one of the elevating roller 555 overlaps the white reference plate 800 when seen from a direction perpendicular to the reference surface 800a, the elevating roller 555 overrides the override member 820 to ensure the interval between the elevating roller 555 and the reference surface 800a.SELECTED DRAWING: Figure 14

Description

[Technical field]

[0001] The present invention relates to a color measurement unit having a function of measuring color, and to an image forming apparatus. [Background technology]

[0002] Color reproducibility is important for image quality in image formation. Color reproducibility is an issue not only between the same model, but also between different models, image forming devices using different methods, and image display devices. To match colors between devices, software and color measuring devices that create multi-dimensional LUTs called ICC (International Color Consortium) profiles are commercially available.

[0003] Professional users create an ICC profile for a printer and an ICC profile for an offset printing machine, and build a color management environment like the one shown in Figure 8. In this environment, it is possible to match the colors output by the printer to the colors printed by the offset printing machine.

[0004] As shown in Fig. 7, the contents of the printing ICC profile and the printer ICC profile are calibrated to correspond to, for example, the CIE L*a*b* color space, based on color measurements of measurement images using a colorimeter. Here, the CIE L*a*b* color space is a color space that is independent of printing presses and printers. CIE stands for Commission Internationale de l'Eclairage.

[0005] This allows the colors printed by the press to match the colors printed by the printer. The Color Management Module (CMM) can then use these profiles to create print data by performing color conversion.

[0006] As described above, color management environments such as colorimeters, applications, and profile creation software are in place, but they have not been widely used due to various remaining issues. Therefore, it is desirable to create profiles faster and easier for color measurement and to automate the setting work. For this reason, image forming devices equipped with in-line colorimeters near the sheet discharge section of the printer have also appeared. Patent Document 1 proposes an in-line colorimeter configuration that improves the detection accuracy of a measurement image formed on a recording medium using a color sensor consisting of a light source, a diffraction grating, and a position detection sensor.

[0007] Generally, as a preparation for measuring a measurement image with a color sensor, a calibration operation using a white reference plate is performed to stabilize the reading accuracy. In order to maintain the reading accuracy, the whiteness of the white reference plate, which serves as the standard for color measurement by the color sensor, is an important value, and any dirt or discoloration on the reference surface (surface) will lead to a decrease in the measurement accuracy of the color sensor. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2013-54324 A Summary of the Invention [Problem to be solved by the invention]

[0009] In a configuration in which the color sensor is movable, a pressing unit that presses down the sheet during the movement of the color sensor may be disposed. In such a configuration, it is required to prevent the pressing unit from coming into contact with the white reference plate and thereby to prevent the reference surface from becoming dirty.

[0010] An object of the present invention is to prevent contamination of a reference surface with a simple configuration. [Means for solving the problem]

[0011] In order to achieve the above object, the present invention provides a conveying means for conveying the sheet in a conveying direction; Orthogonal direction Move to It is movable, The conveyor is Formed into sheets Picture a colorimetric means for measuring the color of the image; a reference member having a reference surface to be measured by the color measuring means for calibration of the color measuring means;A color measuring device moves together with the color measuring device. Measured by A pressing portion for pressing the sheet, and the reference In the direction perpendicular to the surface, From the reference plane Also Protruding Department and When viewed from a direction perpendicular to the reference plane, at least a part of the pressing portion is in contact with the reference Materials Overlaps with Like before When the color measuring means moves, the pressing portion Abutting on part This ensures a distance between the pressing portion and the reference surface. Effect of the Invention

[0012] According to the present invention, contamination of the reference surface can be prevented with a simple configuration. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing an overall configuration of an image forming system. [Diagram 2] FIG. 4 is a cross-sectional view of the adjustment unit. [Diagram 3] FIG. 2 is a control block diagram of a printer and an adjustment unit. [Figure 4] FIG. 2 is a diagram showing a structure of a color sensor. [Diagram 5] FIG. 13 is a diagram for explaining a process up to the calculation of a spectral reflectance. [Figure 6] 13 is a flowchart showing a white reference plate calibration operation process. [Figure 7] FIG. 2 is a diagram showing the configuration of an output ICC profile. [Figure 8] FIG. 1 is a schematic diagram of a color management environment. [Figure 9] FIG. 2 is a perspective view of a color measurement unit and related elements. [Figure 10] FIG. 2 is a perspective view of a color measurement unit and related elements. [Figure 11] FIG. 2 is a plan view of the color measurement unit and its peripheral parts. [Figure 12] 3A and 3B are a cross-sectional view and a plan view of a main part of a color measurement unit. [Figure 13] FIG. 2 is a plan view of the color measurement unit and its surroundings. [Figure 14] FIG. 2 is a side view of the color measurement unit and its surroundings. [Figure 15] FIG. 2 is a plan view of the color measurement unit and its peripheral parts. [Figure 16] FIG. 2 is a plan view of the color measurement unit and its peripheral parts. [Figure 17] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0015] 1 is a diagram showing the overall configuration of an image forming system to which a color measurement unit according to an embodiment of the present invention is applied. This image forming system 1000 includes a printer 100, which is an image forming apparatus, an adjustment unit 400, and a finisher 600. The printer 100 is an electrophotographic laser beam printer, but may be an image forming apparatus of another type, such as an inkjet printer or a dye-sublimation printer.

[0016] Printer 100 includes a housing 101. Housing 101 houses each mechanism constituting an engine section, an engine control section 312 (FIG. 3) that controls each printing process (e.g., paper feeding process, etc.) performed by each mechanism, and a control board storage section that stores printer controller 103 (FIG. 3). Printer 100 includes an optical processing mechanism and a fixing processing mechanism that form an image on a recording material by an electrophotographic process, and a feeding processing mechanism and a transport processing mechanism that feed and transport a sheet S used as a recording material.

[0017] The optical processing mechanism includes stations 120, 121, 122, and 123 that form toner images of each color, yellow, magenta, cyan, and black, and an intermediate transfer body 106. In each of the stations 120 to 123, a primary charger 111 charges the surface of a photosensitive drum 105, which is a drum-shaped photosensitive body. A laser scanner unit 107 exposes the photosensitive drum 105 based on a command signal generated based on image data from a printer controller 103. The laser scanner unit 107 has a laser driver that turns on and off the laser light emitted from a semiconductor laser 108, and guides the laser light from the semiconductor laser 108 to the photosensitive drum 105 via a reflecting mirror 109 while distributing it in the main scanning direction by a rotating polygon mirror. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 105.

[0018] The developing unit 112 contains a developer containing toner therein and supplies charged toner particles to the photosensitive drum 105. The toner particles adhere to the drum surface in accordance with the surface potential distribution, and the electrostatic 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 body 106 to which a voltage of a polarity opposite to the normal charging polarity of the toner is applied. When a color image is formed, the toner images formed by the four stations 120 to 123 are transferred in multiple layers so as to be superimposed on each other on the intermediate transfer body 106, thereby forming a full-color toner image on the intermediate transfer body 106. Meanwhile, the feeding process mechanism feeds the sheets S one by one from the storage 113 to the transfer roller 114. When the sheet S is pressed against the intermediate transfer body 106 by the transfer roller 114, a bias having opposite characteristics to the toner is applied to the transfer roller 114, so that the toner image carried on the intermediate transfer body 106 is transferred (secondary transfer) to the sheet S.

[0019] Around the intermediate transfer body 106, there are arranged an image formation start position detection sensor 115 for determining the print start position when forming an image, a feed timing sensor 116 for timing the feeding of the sheet S, and a density sensor 117. The density sensor 117 measures the density of the measurement image carried on the intermediate transfer body 106.

[0020] The fixing process mechanism is composed of a first fixing device 150 and a second fixing device 160. The first fixing device 150 includes a fixing roller 151 for applying heat to the sheet S, a pressure belt 152 for pressing the sheet S against the fixing roller 151, and a first post-fixing sensor 153 for detecting the completion of the fixing process by the first fixing device 150. Each roller including the fixing roller 151 is a hollow roller and has a heater inside. The first fixing device 150 applies heat and pressure to the toner image on the sheet S while conveying the sheet S by nipping it between the fixing roller 151 and the pressure belt 152. This melts the toner particles and then fixes them, thereby fixing the image on the sheet S.

[0021] The second fixing device 160 is disposed downstream of the first fixing device 150 in the transport path of the sheet S. The second fixing device 160 has a function of increasing the glossiness of the image fixed by the first fixing device 150 and ensuring fixability of the image to the sheet S. Like the first fixing device 150, the second fixing device 160 has a fixing roller 161 and a pressure roller 162, and a second post-fixing sensor 163 that detects the completion of the fixing process by the second fixing device 160.

[0022] Depending on the type of sheet S, there may be cases where it is not necessary to pass the sheet S through the second fixing device 160. To deal with such cases, the printer 100 has a bypass conveying path 130 for discharging the sheet S without passing through the second fixing device 160 for the purpose of reducing energy consumption. The sheet S sent out from the first fixing device 150 is guided by a flap 131 to either the second fixing device 160 or the bypass conveying path 130.

[0023] The sheet S that has passed through the second fixing device 160 or the bypass conveying path 130 is guided by the flap 132 to either the discharge conveying path 139 or the reverse conveying path 135. The position of the sheet S that has been conveyed to the reverse conveying path 135 is detected by the reverse sensor 137, and the leading edge and trailing edge in the sheet conveying direction are swapped by a switchback operation performed by the reverse unit 136. The flap 133 switches whether to guide the sheet S from the reverse unit 136 to the re-conveying path 138 or to the reverse conveying path 135.

[0024] In the case of double-sided printing, the sheet S with an image formed on its first side is conveyed again toward the transfer roller 114 via the re-conveyance path 138 with its leading and trailing ends swapped by the reversing unit 136, and an image is formed on its second side. The sheet S with image formation completed in single-sided printing or the sheet S with image formation completed on its second side in double-sided printing is discharged to the outside of the image forming apparatus 100 via the discharge conveyance path 139. Note that between the reversing conveyance path 135 and the discharge conveyance path 139, a flap 134 is provided that can guide the sheet S switched back by the reversing unit 136 toward the discharge conveyance path 139, and is configured so that the front or back of the sheet S when discharged from the printer 100 can be selected.

[0025] An image reading device 190 and an operation unit 180 serving as a user interface are provided on the upper portion of the printer 100. The operation unit 180 includes a display that displays information to the user. A color measurement unit 200 may also be provided on the reverse transport path 135.

[0026] 2 is a cross-sectional view of the adjustment unit 400. The adjustment unit 400 includes a through path 431 that constitutes a sheet transport path. The through path 431 is a transport path that receives the sheet S discharged from the printer 100 and transports it toward the finisher 600, and extends in a substantially horizontal direction. In the through path 431, a first roller 401, a second roller 402, a third roller 403, and a fourth roller 404 are arranged in this order from upstream to downstream in the sheet transport direction.

[0027] The discharge path 432 is a conveying path for discharging a sheet into a discharge space provided in the adjustment unit 400. The discharge path 432 branches off from the through path 431 downstream of the third roller 403 and extends from the through path 431 upward in a substantially vertical direction. At the branching portion where the discharge path 432 branches off from the through path 431, a flap 422 capable of switching the conveying path of the sheet between the through path 431 and the discharge path 432 is disposed. The sheet S conveyed into the discharge path 432 is conveyed upward by conveying rollers 405, 406, and 407 arranged in this order from the bottom to the top. A discharge roller 408 provided at the most downstream portion (top portion) of the discharge path 432 discharges the sheet to the outside of the adjustment unit 400 and stacks it on a discharge stacking portion 423.

[0028] A color measurement unit 500 is disposed on the discharge path 432. The color measurement unit 500 has a color sensor 501 (color measurement means). The color sensor 501 measures the color of an image (e.g., an image for measurement) formed on the sheet S passing through the discharge path 432 in a reading section 501S. Note that the second path in the lower half is omitted from illustration in FIG. 2. The second path is a path that branches off from the first roller 401 and returns to the third roller 403 without passing through the second roller 402. The color measurement unit 500 may be disposed on the second path.

[0029] 3 is a control block diagram of printer 100 and adjustment unit 400. Printer 100 includes, as a control configuration, printer controller 103, operation unit 180, and engine control unit 312, which are connected to each other so as to be able to communicate with each other. Printer controller 103 centrally controls the operation of image forming system 1000. Printer controller 103 includes profile creation unit 301, Lab calculation unit 303, and color sensor input ICC profile storage unit 304. Printer controller 103 also includes output ICC profile storage unit 305, CMM (color management module) 306, and input ICC profile storage unit 307.

[0030] The engine control unit 312 forms an image on the sheet S based on a command signal from the printer controller 103. For example, the engine control unit 312 controls the operation of the flaps 131 and 132 as well as the conveying motor 311 that drives the rollers that convey the sheet S based on detection signals from the first post-fixing sensor 153, the second post-fixing sensor 163, and the inversion sensor 137.

[0031] The adjustment unit 400 includes the above-mentioned color sensor 501, a communication unit 450, a control unit 451, a moving motor 571, a slide position sensor 545, and the like. The operation of the adjustment unit 400 is controlled by the control unit 451 mounted on the adjustment unit 400. The control unit 451 controls the operation of each motor, such as the moving motor 571, and each flap, based on a detection signal from a conveying path sensor (not shown) arranged on each conveying path in the adjustment unit 400. In addition, the control unit 451 instructs the color sensor 501 to perform color measurement based on a command received from the printer controller 103 of the image forming apparatus 100 via the communication unit 450. The detection results of the color sensor 501 and the slide position sensor 545 are transmitted to the printer controller 103 via the communication unit 450.

[0032] FIG. 4 is a diagram showing the structure of a color sensor 501. The color sensor 501 includes a light source 507, a diffraction grating 502, line sensors 503 (503-1 to 503-n), a calculation unit 504, a memory 505, and a lens 506. The light source 507 is a white LED that irradiates a measurement image 520 on the sheet S with light. The lens 506 focuses the reflected light from the measurement image 520 on the diffraction grating 502. The diffraction grating 502 separates the light reflected from the measurement image 520 into wavelengths. The line sensor 503 is made up of n pixels, and detects the light separated into wavelengths by the diffraction grating 502. The calculation unit 504 performs various calculations from the light intensity values ​​of the pixels detected by the line sensor 503. The calculation unit 504 includes, for example, a spectral calculation unit that calculates a spectral reflectance from the light intensity value, a Lab calculation unit that calculates Lab values, and the like. Various data are stored in the memory 505.

[0033] Next, the process up to calculating the spectral reflectance will be described with reference to Fig. 5. Fig. 5(a) to (c) are diagrams showing the relationship between pixels and output. Fig. 5(d) is a diagram showing the relationship between wavelength and output. Fig. 5(e) is a diagram showing the relationship between wavelength and reflectance.

[0034] The light source 507 is forced to emit light to stabilize the amount of light, and then is turned off. The calculation unit 504 measures the dark voltage of the line sensor 503 (FIG. 5(a)). Next, the calculation unit 504 performs a calibration operation using a white reference plate 800 (FIGS. 11, 14, etc.). The calibration operation is started from the light amount adjustment. The light amount adjustment is an adjustment for adjusting the peak output value Vpeak of the line sensor 503 to a target value Vtar (FIG. 5(b)). This is performed to correct fluctuations in the output of the line sensor 503 caused by the life of the light source 507, dirt on the window surface of the color sensor 501, and temperature changes of the color sensor 501.

[0035] Next, the spectral data of the white reference plate 800 is measured with the adjusted light amount (FIG. 5(c)). Then, based on the measurement data (solid line in FIG. 5(c)), the positional deviation amount α of the light incident on the line sensor 503 is calculated. This positional deviation amount α is calculated by comparing with the spectral data of the white reference plate 800 measured at the time of shipping the color sensor 501 from the factory (broken line in FIG. 5(c)). The spectral data of the white reference plate 800 measured at the time of shipping from the factory is called initial white reference plate data, and this data is stored in the memory 505. The positional deviation amount α is corrected, and the output value for each pixel is converted to an output value for each wavelength (FIG. 5(d)). This correction is called distortion correction. Also, converting the output value for each pixel to an output value for each wavelength is called pixel wavelength conversion. After that, the measurement image is actually measured, and dark voltage correction and pixel wavelength conversion processing are performed from the measured data, and further, the spectral reflectance is calculated by comparing with the spectral data of the white reference plate 800 (FIG. 5(e)). The spectral reflectance Rp of the measurement image is calculated by Equation 1. Rp = Measurement image spectral data / White reference plate spectral data × Reference plate reflectance (Equation 1) The reference plate reflectance is data obtained by measuring the reflectance of a white reference plate using a commercially available measuring device, and this data is stored in memory 505.

[0036] Fig. 6 is a flowchart showing the white reference plate calibration operation process. The printer controller 103 has a CPU, RAM, and ROM (not shown). The process shown in Fig. 6 is realized by the CPU expanding a program stored in the ROM of the printer controller 103 into the RAM and executing it. At that time, the printer controller 103 controls the color sensor 501 by sending a command to the control unit 451.

[0037] The printer controller 103 executes forced light emission in step S100. This forced light emission is performed to stabilize the amount of light from the light source 507. The time it takes for the amount of light to stabilize correlates with the time it takes for the temperature of the light source 507 to stabilize. The printer controller 103 executes dark voltage correction in step S101, and executes light amount adjustment in step S102. The printer controller 103 executes measurement of the white reference plate 800 in step S103, and executes white reference plate correction, i.e., distortion correction, in step S104.

[0038] Next, a method for feeding back the results detected by the color sensor 501 within the printer 100 will be described. In this embodiment, a basic flow for creating a profile and outputting using the profile will be described.

[0039] As a profile that realizes excellent color reproducibility, an ICC (International Color Consortium) profile that has been accepted in the market in recent years is used. However, this is not a limitation, and other color management systems may be used instead of an ICC profile. For example, it is possible to use the CRD (Color Rendering Dictionary) that is adopted in PostScript (registered trademark) proposed by Adobe, or the color separation table installed in Adobe Photoshop (registered trademark). In addition, it is also possible to use the CMYK simulation function of EFI's ColorWise (registered trademark), which maintains black plate information.

[0040] The adjustment unit 400 connected to the printer 100 has a built-in color sensor 501 (FIG. 2) that can measure spectral reflectance. The color sensor 501 can measure spectral reflectance, and the adjustment unit 400 converts it into chromaticity to create a color conversion profile by itself. The adjustment unit 400 then performs internal conversion color processing using the created color conversion profile.

[0041] The formula for calculating chromaticity will be described. The signal measured by the spectral sensor and inputted is the spectral reflectance detected on the CMOS sensor arranged in each wavelength region of 380 nm to 720 nm, when the light irradiated from the white LED hits the measurement object and the reflected light is dispersed by the diffraction grating. In this embodiment, in order to improve the detection calculation accuracy, the spectral reflectance is converted to L*a*b* via a color matching function as specified by the CIE. The printer controller 103 finds the relationship between the information converted to L*a*b* and the signal value of the measurement image, and creates an ICC profile, which is a color conversion profile.

[0042] A method for calculating chromaticity values ​​(L*a*b*) from spectral reflectance is described below. The coordinates of the L*a*b* color space can be calculated from the spectral reflectance using a procedure that complies with ISO 13655, for example, as shown below. a. Calculate the spectral reflectance R(λ) of the sample. (λ: 380nm~780nm) b. Prepare color matching functions x(λ), y(λ), z(λ) and standard light spectral distribution SD50(λ). Note that color matching functions are specified in JIS Z8701. SD50(λ) is specified in JIS Z8720 and is also called supplementary standard illuminant D50. c. Multiply the spectral reflectance R(λ), color matching functions x(λ), y(λ), z(λ) and standard light spectral distribution SD50(λ) for each wavelength.

[0043] R(λ)×SD50(λ)×x(λ) R(λ)×SD50(λ)×y(λ) R(λ)×SD50(λ)×z(λ) d. The product of step c above is integrated over the entire wavelength range.

[0044] Σ{R(λ)×SD50(λ)×x(λ)} Σ{R(λ)×SD50(λ)×y(λ)} Σ{R(λ)×SD50(λ)×z(λ)} e. Calculate the integrated value of the product of the color matching function y(λ) and the standard light spectral distribution SD50(λ).

[0045] Σ{SD50(λ)×y(λ)} f. Calculate the coordinates in the XYZ color space.

[0046] X=100×Σ{SD50(λ)×y(λ)} / Σ{R(λ)×SD50(λ)×x(λ)} Y=100×Σ{SD50(λ)×y(λ)} / Σ{R(λ)×SD50(λ)×y(λ)} Z=100×Σ{SD50(λ)×y(λ)} / Σ{R(λ)×SD50(λ)×z(λ)} g. Convert the XYZ coordinates obtained in (f) into the L*a*b* color space.

[0047] L*=116×(Y / Yn)^(1 / 3)-16 a*=500{(X / Xn)^(1 / 3)-(Y / Yn)^(1 / 3)} b*=200{(Y / Yn)^(1 / 3)-(Z / Zn)^(1 / 3)} In the above g, Xn, Yn, and Zn are values ​​that represent the coordinates of the reference white point (standard tristimulus values). Also, the above g is a conversion formula when Y / Yn≧0.008856, and is replaced as follows in the region where Y / Yn<0.008856.

[0048] (X / Xn)^(1 / 3)→7.78(X / Xn)^(1 / 3)+16 / 116 (Y / Yn)^(1 / 3)→7.78(Y / Yn)^(1 / 3)+16 / 116 (Z / Zn)^(1 / 3)→7.78(Z / Zn)^(1 / 3)+16 / 116 Next, the details of the profile creation process in which the printer 100 creates an ICC profile will be described. The profile creation process can be executed at any timing by the user issuing an instruction by operating the operation unit 180. For example, the profile creation process may be executed when a customer engineer replaces parts, before an image forming job that requires high color reproducibility is executed, or when the color tone of the final output is to be known at the design concept stage.

[0049] 3, when an operation for creating an ICC profile is performed on the operation unit 180, a signal instructing the creation of a profile is input to the profile creation unit 301 of the printer controller 103. The profile creation unit 301 transmits a CMYK signal for outputting a test form (CMYK color chart) defined in ISO 12642 to the engine control unit 312 without performing color conversion using the output ICC profile. The profile creation unit 301 sends an instruction (colorimetry instruction) to the adjustment unit 400 to perform measurement using a color sensor 501. The printer 100 executes an image forming operation based on the CMYK signal input to the engine control unit 312, and forms the test form on the sheet S. The sheet S on which the test form has been formed is conveyed to the adjustment unit 400, and the test form is colorimetrically measured by the color sensor 501.

[0050] The spectral reflectance data of the 928 measured measurement images is notified to the Lab calculation unit 303 of the printer controller 103, which converts it into L*a*b* color space data and inputs it to the profile creation unit 301. At this time, the L*a*b* color space data may be temporarily stored in a color sensor input ICC profile storage unit 304. Note that although the present embodiment employs CIE L*a*b* as the device-independent color space, other color spaces (for example, CIE1931 XYZ color space) may be employed instead.

[0051] The profile creation unit 301 creates an output ICC profile based on the relationship between the CMYK signals sent to the engine control unit 312 and the input L*a*b* data. The profile creation unit 301 also replaces the output ICC profile stored in the output ICC profile storage unit 305 with this output ICC profile.

[0052] The output ICC profile has a structure as shown in FIG. 7, for example, and is composed of a header, tags, and their data. The test form defined in ISO 12642 includes CMYK color signals that cover the color reproduction range that can be output by a general copier. The profile creation unit 301 creates a CMYK → L*a*b* conversion table (A2Bx tag) based on the CMYK signals used to output the test form and the L*a*b* values ​​obtained from the color measurement results. In addition, a reverse conversion table (B2Ax tag) from L*a*b* → CMYK is created based on this conversion table. Other tags that represent data, such as the white point (wtpt) and a tag (gamt) that describes whether a certain color is inside or outside the reproduction range that can be reproduced by hard copy, are also described in the output ICC profile.

[0053] When an execution command for the profile creation process is input via the external I / F 308, the ICC profile created by the profile creation unit 301 may be transmitted to the external device that issued the execution command. In this case, it is possible for the user to perform color conversion on the external device using an application compatible with the ICC profile.

[0054] Next, a description will be given of the color conversion process performed on input image data when an image formation job is input to the printer 100 to command image formation. In the block diagram shown in Fig. 3, image data received by the printer controller 103 via the external I / F 308 is sent to an input ICC profile storage unit 307 for external input. In normal color printing, it is assumed that the image data is expressed in RGB values ​​or standard printing CMYK signal values ​​such as JapanColor.

[0055] In the input ICC profile storage unit 307, conversion from RGB to L*a*b* or CMYK to L*a*b* is performed according to the input image signal. The input ICC profile is composed of a one-dimensional LUT (lookup table) that controls the gamma of the input signal, a multi-color LUT called direct mapping, and a one-dimensional LUT that controls the gamma of the generated conversion data. Using these tables, conversion is performed from a device-dependent color space to device-independent L*a*b* data.

[0056] The image signal converted into the L*a*b* chromaticity coordinates is input to the CMM 306. Then, the image signal is subjected to GAMUT conversion, color conversion, black character determination, etc. In the GAMUT conversion, mismatches in the output color reproduction range between the read color space of the external I / F 308 such as a scanner unit as an input device and the printer 100 as an output device are mapped. Also, color conversion is performed to adjust the mismatch between the light source type at the time of input and the light source type when observing the output object (also called a mismatch in color temperature setting), black character determination, etc. are performed.

[0057] As a result, the L*a*b* data is converted to L*'a*'b*' data and 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. The created profile is then color converted by a newly created ICC profile, converted to a CMYK (Cyan Magenta Yellow Black) signal dependent on the output device, and output.

[0058] 3, in terms of the block configuration, the CMM 306 has been described as being separate from the input ICC profile storage unit 307 and the output ICC profile storage unit 305. However, as shown in Fig. 8, the CMM is a module that controls color management, and is a module that performs color conversion using the input profile and the output profile.

[0059] Next, the configuration and operation of a color measurement unit 500 including a color sensor 501 will be described with reference to Figs. 9 to 12. Figs. 9 and 10 are perspective views of the color measurement unit 500 and related elements. Fig. 11 is a plan view of the color measurement unit 500 and its peripheral parts.

[0060] The color measurement unit 500 mainly includes a moving unit 530, a driving unit 570 (driving means), a slide position sensor 545 (FIG. 10), and a white reference plate 800 (FIG. 11). Peripheral components of the color measurement unit 500 include a transport roller unit 580, a transport driving unit 590, and a backing member 810 (FIG. 11).

[0061] The moving unit 530 includes a color sensor 501, and moves to the rear and front sides of the adjustment unit 400 shown in FIG. 2. The left side in FIG. 11 corresponds to the front side. Hereinafter, the conveying direction of the sheet S is referred to as the paper passing direction A. The direction (sheet width direction) approximately perpendicular to the paper passing direction A and the sheet surface is the moving direction B of the color sensor 501. The driving unit 570 drives the moving unit 530 to move it.

[0062] The transport roller unit 580 transports the sheet S. The transport drive unit 590 drives the transport roller unit 580. After the transport roller unit 580 receives the sheet S in the paper passing direction A, the moving unit 530 moves in the moving direction B while the color sensor 501 measures the color.

[0063] 10, in the moving unit 530, a moving bearing 532 is attached to a moving support plate 531. The moving bearing 532 engages with a moving belt 533 via a tooth surface, and also engages with a moving shaft 534. The moving belt 533 engages with a moving motor 571 via a moving pulley 572. Therefore, by operating the moving motor 571, the moving unit 530 is driven via the moving pulley 572 and the moving belt 533, and moves back and forth in a direction parallel to the moving direction B. The amount of movement of the moving unit 530 is controlled by sending a predetermined pulse to a flag portion 531f of the moving support plate 531 after the slide position sensor 545 switches ON / OFF.

[0064] 11, an area of ​​the backing member 810 that overlaps with the transport roller unit 580 becomes a transport guide surface 810a (sheet transport surface) that transports the sheet S. A white reference plate 800 is disposed at the left end of the backing member 810. A paper passing area R1 is an area through which the sheet S is transported. The white reference plate 800 is located outside the paper passing area R1.

[0065] The transport roller unit 580 has an upstream unit 580a on the upstream side in the paper passing direction A, and the upstream unit 580a includes an upstream transport drive roller (not shown) and an upstream transport driven roller (not shown). The upstream transport drive roller is an aluminum pipe with a urethane coating of 30 μm thick on its outer periphery, and has an outer diameter of 20 mm. The upstream transport drive roller is rotatably supported at both ends by bearings (not shown), and is rotationally driven by the transport drive unit 590.

[0066] The upstream transport driven roller is pressed against the upstream transport drive roller by a spring (not shown), and a nip is formed between the upstream transport drive roller and the upstream transport driven roller. The upstream transport driven roller is made of aluminum with silicone rubber wrapped around its surface, and has an outer diameter of 20 mm. The upstream transport driven roller is also rotatably supported by a bearing (not shown). The upstream transport driven roller rotates by being driven by the upstream transport drive roller.

[0067] The conveying roller unit 580 also has a downstream unit 580b on the downstream side in the paper passing direction A, and the downstream unit 580b includes a downstream conveying driven roller (not shown) and a downstream conveying roller (not shown). The specifications of the downstream unit 580b are the same as those of the upstream unit 580a, so a description thereof will be omitted.

[0068] In this embodiment, the driving force is transmitted to the upstream unit 580a and the downstream unit 580b by the transport roller unit 580. However, a transport drive unit may be provided for each of the upstream transport drive roller and the downstream transport drive roller to transmit the driving force.

[0069] Fig. 12(c) is a plan view of the main parts of the color measurement unit 500. Figs. 12(a) and 12(b) are cross-sectional views taken along line AA and line BB in Fig. 12(c), respectively. The color sensor 501 is attached to a support plate 553 and is built into the color measurement unit 500. A pair of fixed rollers 554 (rotating bodies) are disposed on both ends of the support plate 553 in the paper feed direction A. A pair of lift rollers 555 (pressing parts) are disposed on both ends of the support plate 553 in the movement direction B.

[0070] In a plan view, the rotation axis of the pair of fixed rollers 554 passes through the reading unit 501S of the color sensor 501. Therefore, in the movement direction B, the position of the rotation axis of the pair of fixed rollers 554 and the center position of the color sensor 501 approximately coincide with each other. By abutting each fixed roller 554 against the sheet S, the color sensor 501 can scan while maintaining a constant relative distance to the measurement target surface (surface of the sheet S). Therefore, the pair of fixed rollers 554 guarantee the distance between the color sensor 501 and the measurement target sheet S.

[0071] The pair of lift rollers 555 are rotating bodies whose longitudinal direction is the paper passing direction A. The rotation axis of each lift roller 555 is approximately parallel to the paper passing direction A. In a plan view, the pair of lift rollers 555 are arranged on a straight line that is parallel to the movement direction B and passes through the reading unit 501S. Each lift roller 555 is attached to the support plate 553 via a lift roller bearing 556, a lift roller spring 557 (elastic member), and a lift roller holder 558. Therefore, the pair of lift rollers 555 are urged toward the transport guide surface 810a (the side of the sheet S in the direction perpendicular to the transport guide surface 810a) by the lift roller spring 557.

[0072] The color sensor 501 is capable of reciprocating movement in a movement direction B. A pair of lift rollers 555 move together with the color sensor 501 and hold down the sheet S to be measured during the movement of the color sensor 501. During at least a portion of the movement of the color sensor 501, at least a portion of the pair of lift rollers 555 overlaps with the white reference plate 800 when viewed from a direction perpendicular to the reference surface 800a. For example, when the color sensor 501 moves over the white reference plate 800, there are times when the pair of lift rollers 555 overlap with the white reference plate 800 in a plan view.

[0073] 13 and 14 are a plan view and a side view, respectively, of the color measurement unit 500 and its surroundings.

[0074] As shown in Fig. 13, a pair of rise members 820 are provided protruding from the backing member 810 on both sides of the white reference plate 800 in the paper passing direction A. The rise members 820 are formed, for example, integrally with the backing member 810 at positions sandwiching the white reference plate 800 in the paper passing direction A. The upper end position of each rise member 820 is higher than the reference surface 800a. The transport guide surface 810a and the reference surface 800a of the white reference plate 800 are substantially on the same plane (Fig. 14). The pair of rise members 820 have the same shape. The rise members 820 are rib-shaped protruding members that are long in the movement direction B.

[0075] The relationship between the lift roller 555 and the climbing member 820 will be described. As shown in Fig. 13, the length of the lift roller 555 in the paper-passing direction A is defined as L1. The interval between the pair of climbing members 820 in the paper-passing direction A is defined as L2. Note that the interval L2 is defined as the shortest distance between the pair of climbing members 820 in the paper-passing direction A, but may also be defined as the distance between the centers of the climbing members 820 in the paper-passing direction A.

[0076] Here, the length L1 is longer than the interval L2, and the relationship L1>L2 is established. As a result, each of the lift rollers 555 rolls while contacting the two climb members 820. Therefore, when viewed from a direction perpendicular to the reference surface 800a, when the lift rollers 555 move in an area where at least a part of the lift rollers 555 overlaps with the white reference plate 800, the lift rollers 555 reliably climb onto the pair of climb members 820, thereby ensuring the interval between the lift rollers 555 and the reference surface 800a. As a result, the lift rollers 555 do not come into contact with the white reference plate 800 between the two climb members 820, and the adhesion of dirt to the reference surface 800a is prevented.

[0077] As shown in FIG. 14, the distance between the two lift rollers 555 in the moving direction B is L3. centerIt is defined as the distance between the positions, but it may be defined as the shortest distance. The length of the white reference plate 800 in the moving direction B is L4. The length of the lifting member 820 in the moving direction B is L5. The interval L3 is greater than the length L5, and the length L5 is greater than the length L4. That is, the relationship L3>L5>L4 is established. As a result, the lifting roller 555 does not remain on the lifting member 820 during the movement process of the color sensor 501 during calibration. For example, when reading the white reference plate 800, the two lifting rollers 555 are in a position straddling the lifting member 820 and abut against the transport guide surface 810a, so that the distance between the color sensor 501 and the white reference plate 800 is appropriately secured. Therefore, the white reference plate 800 can be read with high accuracy.

[0078] Next, the measurement operation of the color sensor 501 will be described with reference to Fig. 15 and Fig. 16. Fig. 15(a), (b), Fig. 16(a), and (b) are plan views of the color measurement unit 500 and its peripheral components. Fig. 16(a) and (b) also show the sheet S in the middle of being transported.

[0079] First, the color sensor 501 waits on the white reference plate 800 (FIG. 15(a)). This position of the color sensor 501 is called the waiting position. The waiting position is outside the range of the paper passing area R1, and the position of the white reference plate 800 is also outside the range of the paper passing area R1. The color sensor 501 can move in a direction approximately parallel to the movement direction B in an area including the white reference plate 800 and the paper passing area R1.

[0080] When starting the color measurement operation, the color sensor 501 retreats 100 mm in the movement direction B from the white reference plate 800 (FIG. 15(b)). At this time, the lifting rollers 555 move while climbing up on a pair of climbing members 820. Because the climbing members 820 are higher than the reference surface 800a of the white reference plate 800, the lifting rollers 555 do not come into contact with the white reference plate 800 even when they pass over the white reference plate 800.

[0081] The color sensor 501 is forced to emit light for 45 seconds while retracted from the white reference plate 800 (FIG. 15(b)). After that, the color sensor 501 returns to a position above the white reference plate 800 (FIG. 15(a)). Even when the lift rollers 555 pass over the white reference plate 800 during this movement process, the lift rollers 555 do not come into contact with the white reference plate 800. After the color sensor 501 returns to the standby position, the calibration by the color sensor 501 described above is performed, and the color sensor 501 waits until the sheet S is transported.

[0082] Measurement images of n rows and m columns are formed on the sheet S. In the first row, m measurement images from images P1-1, P1-2, . . . P1-m are formed, and these are formed for n rows from P1, P2, . . . Pn. The control unit 451 controls the conveying roller unit 580 based on the detection result of a sheet position detection unit (not shown), and can convey, stop, and convey the sheet S a predetermined amount. As shown in FIG. 16(a), the sheet S is conveyed within the range of a paper passing area R1.

[0083] When the sheet S is transported, the color sensor 501 waits at a standby position as shown in FIG. 15(a). The sheet S is transported to a color measurement position that matches the positions of the color sensor 501 and the first row of measurement images P1-1 to P1-m, and stops there (FIG. 16(a)). In this state, the color sensor 501 reads the m first row of measurement images while moving in the moving direction B, and stops at the end position. That is, the color sensor 501 reaches the end position on the opposite side of the paper passing area R1 from the standby position (FIG. 16(b)). The end position is also outside the range of the paper passing area R1.

[0084] 16(b), with the color sensor 501 positioned at the end position, the sheet S is transported to a color measurement position that matches the positions of the color sensor 501 and the measurement images P2-1 to P2-m in the second row, and stops there. In this state, the color sensor 501 reads the m measurement images in the second row while moving parallel to the moving direction B. By repeating the same reading operation n times, all of the n×m measurement images can be read.

[0085] According to this embodiment, the backing member 810 is provided with a riding member 820 higher than the reference surface 800a of the white reference plate 800. Therefore, when the color sensor 501 moves in an area where at least a part of the lift roller 555 overlaps with the white reference plate 800 when viewed from a direction perpendicular to the reference surface 800a, the lift roller 555 rides on the riding member 820. This ensures a gap between the lift roller 555 and the reference surface 800a, and prevents the reference surface 800a from being soiled due to contact with the lift roller 555. Although the color sensor 501 is configured to move, there is no need to provide a shutter or other member to protect the reference surface 800a, so the configuration is simple and costs can be suppressed. Therefore, the simple and inexpensive configuration can prevent the reference surface 800a from being soiled. In addition, since the white reference plate 800 is outside the paper passing area R1, paper dust from the sheet S is less likely to accumulate on the white reference plate 800.

[0086] In addition, the pair of fixed rollers 554 ensures the distance between the color sensor 501 and the measurement target sheet S. In particular, in the movement direction B, the position of the rotation axis of the fixed rollers 554 and the position of the color sensor 501 approximately coincide with each other, so the relative distance between the color sensor 501 and the sheet S is accurately kept constant. Therefore, the variation in the reading accuracy of the measurement image is small and the accuracy is high.

[0087] Furthermore, the length L1 of the lift roller 555 in the paper feed direction A is greater than the distance L2 between the pair of climb members 820 (L1>L2). Therefore, when the lift roller 555 moves near the white reference plate 800, the lift roller 555 reliably climbs onto the pair of climb members 820. This reliably prevents the reference surface 800a from becoming dirty.

[0088] Furthermore, the distance L3 between the two lifting rollers 555 in the movement direction B, the length L4 of the white reference plate 800, and the length L5 of the riding member 820 have the relationship L3>L5>L4. This prevents the lifting rollers 555 from remaining on the riding member 820 when reading the white reference plate 800. Therefore, the white reference plate 800 can be read with high accuracy.

[0089] In this embodiment, the rise member 820 is formed on the backing member 810 which is a holding part that holds the white reference plate 800. However, the rise member 820 may be a protruding member that protrudes in the height direction from the reference surface 800a, and may be fixed directly or indirectly to the white reference plate 800, or may be formed integrally with the white reference plate 800. For example, as in a modified example shown in FIG. 17, the rise member 820 as a protruding member may be formed integrally with the white reference plate 800. In the example shown in FIG. 17, the rise member 820 that protrudes higher than the reference surface 800a is formed integrally with both ends of the white reference plate 800 in the paper passing direction A.

[0090] Although the lift roller 555 is exemplified as a pressing portion that presses the sheet S to be measured during the movement of the color sensor 501, the pressing portion is not limited to this. For example, the pressing portion may be a member that slides on the sheet S without rotating.

[0091] In the above description, the color measurement unit 500 to which the present invention is applied is mounted on the adjustment unit 400. However, the color measurement unit to which the present invention is applied may be mounted on the printer 100. For example, the present invention may be applied to the color measurement unit 200 (FIG. 1). In this case, the printer controller 103 controls the color measurement unit 200. The image forming system 1000 may also include a connection unit other than the adjustment unit 400 and the finisher 600, and the connection unit to which the color measurement unit to which the present invention is applied is not limited. An image forming system including at least one connection unit such as the adjustment unit 400, such as the image forming system 1000, may be understood as an "image forming apparatus."

[0092] In this embodiment, the term "substantially" does not mean to completely exclude "substantially". For example, "substantially the same", "substantially the same", "substantially parallel", "substantially perpendicular", "substantially vertical", and "substantially horizontal" are intended to include the completely "coincident", "same", "parallel", "perpendicular", "vertical", and "horizontal" respectively.

[0093] The present invention has been described above in detail based on preferred embodiments thereof, but the present invention is not limited to these specific embodiments, and various forms that do not deviate from the gist of the present invention are also included in the present invention. [Explanation of symbols]

[0094] 500 color measurement units 501 Color Sensor 555 Lifting roller 570 Drive Unit 800 White reference plate 800a Reference Surface 820 Riding member R1 Paper passing area

Claims

1. A conveying means for conveying the sheet in a conveying direction; a color measuring means for measuring a color of an image formed on a sheet transported by the transport means, the color measuring means being movable in a direction perpendicular to the transport direction; a reference member having a reference surface to be measured by the color measuring means for calibration of the color measuring means; a pressing unit that moves together with the color measurement unit and presses a sheet to be measured by the color measurement unit; a protruding portion that protrudes from the reference surface in a direction perpendicular to the reference surface, A colorimetric unit characterized in that when the colorimetric means moves so that at least a portion of the pressing portion overlaps the reference member when viewed from a direction perpendicular to the reference surface, the pressing portion abuts the protrusion, thereby maintaining a distance between the pressing portion and the reference surface.

2. 2. The color measurement unit according to claim 1, further comprising a rotating body that moves together with the color measurement means and abuts against the sheet to be measured by the color measurement means, thereby maintaining a predetermined distance between the color measurement means and the sheet.

3. 3. The color measurement unit according to claim 2, wherein the position of the rotating body coincides with the position of the color measurement means in a moving direction of the color measurement means.

4. a pair of the protruding portions are disposed on both sides of the color measuring means in the transport direction; 4. The color measurement unit according to claim 1, wherein a length of the pressing portion in the transport direction is longer than a distance between the pair of protrusions in the transport direction.

5. The pressing portion is disposed in pair on both sides of the color measurement means in a moving direction of the color measurement means, A color measurement unit described in any one of claims 1 to 4, characterized in that the distance between the pair of pressing portions in the movement direction is greater than the length of the protrusion in the movement direction, and the length of the protrusion in the movement direction is greater than the length of the reference member in the movement direction.

6. A color measurement unit as described in any one of claims 1 to 5, characterized in that the pressing portion is movable in a direction perpendicular to the reference surface and is biased toward the reference member in the direction perpendicular to the reference surface by an elastic member.

7. The color measurement unit according to claim 1 , wherein the protrusion is formed on a holder that holds the reference member.

8. The color measurement unit according to claim 1 , wherein the protrusion is formed on the reference member.

9. 9. The color measurement unit according to claim 1, wherein the reference member is disposed outside a passing area of ​​the sheet transported by the transport means.

10. 10. The color measurement unit according to claim 1, wherein the pressing portion is a rotatably supported member.

11. A colorimetric unit described in any one of claims 1 to 10, characterized in that when the holding portion is in a position not abutting the protrusion in the movement direction of the colorimetric means, in a direction perpendicular to the reference surface, it is located in a position where the sheet can be held down or where the reference surface can be measured by the colorimetric means.

12. An image forming apparatus comprising the color measurement unit according to claim 1 .

Images