JP7615084B2 - Image forming device - Google Patents

Description

The present invention relates to a reading process that reads a test image for calibration formed on a sheet while moving in a direction intersecting the conveying direction of the sheet.

In recent years, the market for on-demand image forming devices has expanded. For example, electrophotographic image forming devices are becoming more widespread in the offset printing market. In addition, there are inkjet image forming devices that have succeeded in cultivating a wide range of markets due to their large format, low initial cost, and ultra-high speed. However, market expansion is not easy, and the image quality (hereafter referred to as "image quality") of the previous image forming devices that have dominated that market must be maintained.

The quality of images formed by image forming devices includes gradation, graininess, in-plane uniformity, character quality, color reproducibility (including color stability), etc. For example, the reproducibility of specific colors (memory colors) that humans remember is important when outputting them as photographs, etc. Also, for example, office users who feel uncomfortable with the difference in color between printed matter and the monitor, or graphic arts users who work with computer graphics, have high requirements for the color reproducibility of images printed by image forming devices.

For this reason, image forming devices have recently appeared that read test images formed on sheets and determine image formation conditions. The image forming device described in Patent Document 1 has a reading sensor unit that moves in a direction intersecting the conveying direction in which the sheet is conveyed in order to read the test images formed on the sheets. The image forming device in Patent Document 1 also performs calibration to generate a color profile for adjusting the color of the image formed by the image forming device based on the results of reading the test images.

JP 2021-179555 A

However, if the size of the sheet on which the test image is formed changes, it is preferable to also change the layout of the test image formed on the sheet.

However, when the reading operation is performed according to a predetermined number of reading lines as in Patent Document 1, the sensor moves so as to read areas where no test image is formed, which may increase downtime. Also, when the reading operation is performed according to a predetermined number of reading lines as in Patent Document 1, the number of test images required to perform calibration may be insufficient, and highly accurate calibration results may not be obtained.

The object of the present invention is to perform a reading operation appropriate for the size of the sheet used for calibration.

In order to solve the above problem, an image forming apparatus of the present invention includes an image forming means for forming a test image on a sheet, a transport means having a plurality of rollers for transporting the sheet, a reading means for moving in a width direction intersecting a transport direction in which the sheet is transported by the transport means and for reading the sheet while moving in the width direction while the sheet is stopped while the transport means transports the sheet intermittently, a receiving means for receiving a selection result of a calibration selected from a plurality of calibrations, an acquiring means for acquiring information regarding a size of the sheet on which the test image is formed, and a determination unit for determining, when a predetermined calibration is selected from the plurality of calibrations, the number of sheets on which the test image is formed and the number of multiple rows of patch lines aligned in the transport direction in the test image to be formed on each of the sheets based on the information, and the number of transports when the transport means repeatedly stops and transports the sheet while transporting the sheet intermittently and the number of movements of the reading means in the width direction are determined based on the number of the patch lines of each sheet determined by the determination unit. the number of sheets when the predetermined calibration is formed on an A3 size sheet is less than the number of sheets when the predetermined calibration is formed on an A4 size sheet, the A3 size sheets on which the test image for the predetermined calibration is formed include a first sheet having a first number of patch lines and a second sheet having a second number of patch lines equal to or less than the first number, the A4 size sheets on which the test image for the predetermined calibration is formed include a third sheet having a third number of patch lines and a fourth sheet having a fourth number of patch lines equal to or less than the third number, and the number of movements of the reading means when reading the test image for the predetermined calibration on the first A3 size sheet is greater than the number of movements of the reading means when reading the test image for the predetermined calibration on the third A4 size sheet .

According to the present invention, it is possible to perform a reading operation appropriate for the size of the sheet used for calibration.

Schematic diagram of an image forming apparatus Schematic diagram of the automatic reading device Cross-sectional view of the main part of the color measurement unit Control block diagram of an image forming apparatus Color management illustration FIG. 1 is a partial perspective view of a moving mechanism for moving an image sensor of an automatic reading device. FIG. 7 is an enlarged view of a main part of the moving mechanism shown in FIG. FIG. 1 is a perspective view of a main part showing the positional relationship between an image sensor and a conveying roller; Cross-sectional view of the main part around the image sensor of the automatic reading device FIG. 2 is an explanatory diagram of a patch image reading process FIG. 1 is a flow chart showing a calibration sequence using an automatic reader. Flowchart showing the sequence for determining the number of patch lines

The following describes an embodiment of the present invention with reference to the drawings.

(Image forming apparatus)
1 is a schematic diagram of an image forming apparatus 1. The image forming apparatus 1 of this embodiment is composed of a printer 100, an automatic reader 400, and a paper discharge device 600. The printer 100 forms an image on a sheet S. When calibration is performed, the printer 100 also forms a test image (hereinafter referred to as a patch image) on the sheet S according to the calibration. In the following description, the printer 100 is described as an electrophotographic printer that forms an image using toner. However, the printer 100 that functions as an image forming unit is not limited to an electrophotographic printer, and may be an inkjet printer or a dye-sublimation printer.

The printer 100 includes mechanisms constituting an image forming engine section within a housing 101, and a controller (described below) that controls the operation of each mechanism. An operation panel 180 is provided on the top of the housing 101. The operation panel 180 is a user interface, and includes an input device that accepts instructions from a user, and a display as an output device that displays an operation screen. The input device is various key buttons, a touch panel, or the like. The mechanisms constituting the image forming engine section include a mechanism for forming an image (image forming mechanism), a mechanism for transferring an image to a sheet S (transfer mechanism), a mechanism for feeding the sheet S (feed mechanism), and a mechanism for fixing the image to the sheet S (fixing mechanism).

The image forming mechanism includes four image forming units 120, 121, 122, and 123 corresponding to the colors of yellow (Y), magenta (M), cyan (C), and black (K). The image forming units 120, 121, 122, and 123 form images of the corresponding colors. The image forming units 120, 121, 122, and 123 have the same configuration, except that they form different colors of images. Here, the configuration of the image forming unit 120 will be described, and descriptions of the configurations of the other image forming units 121, 122, and 123 will be omitted.

The image forming unit 120 includes a photosensitive drum 105, a charger 111, a laser scanner 107, and a developer 112. The photosensitive drum 105 is a drum-shaped photosensitive body having a photosensitive layer on its surface, and rotates around the drum axis. The charger 111 uniformly charges the photosensitive layer on the surface of the rotating photosensitive drum 105. The laser scanner 107 scans the surface of the photosensitive drum 105 with a laser beam modulated based on image data representing the image to be formed. The laser scanner 107 includes a light emitting unit 108 that scans the laser beam emitted from a semiconductor laser in one direction, and a reflection mirror 109 that reflects the laser beam from the light emitting unit 108 toward the photosensitive drum 105. The direction in which the laser scanner 107 scans the photosensitive drum 105 (the depth direction in the figure) is the main scanning direction.

After being charged, the photosensitive drum 105 is scanned with a laser beam, forming an electrostatic latent image on the surface according to the image data. The developing unit 112 develops the electrostatic latent image formed on the photosensitive drum 105 with a developer of the corresponding color. As a result, an image is formed on the surface of the photosensitive drum 105 in which the electrostatic latent image is visualized. A yellow image is formed on the photosensitive drum 105 of the image forming unit 120. A magenta image is formed on the photosensitive drum 105 of the image forming unit 121. A cyan image is formed on the photosensitive drum 105 of the image forming unit 122. A black image is formed on the photosensitive drum 105 of the image forming unit 123. The photosensitive drum 105 and the developing unit 112 are detachable from the housing 101.

The transfer mechanism includes an intermediate transfer body 106 and a transfer roller 114. Images are transferred from the photosensitive drums 105 of the image forming units 120, 121, 122, and 123 in a sequentially superimposed manner onto the intermediate transfer body 106. In this embodiment, the intermediate transfer body 106 rotates clockwise in the figure, and images are transferred in the order of the image forming unit 120 (yellow), image forming unit 121 (magenta), image forming unit 122 (cyan), and image forming unit 123 (black). An image density detection sensor 117 is provided downstream of the image forming unit 123 in the rotation direction of the intermediate transfer body 106 to detect image density from an image for image density detection formed on the intermediate transfer body 106.

The image transferred to the intermediate transfer body 106 is transported to the transfer roller 114 as the intermediate transfer body 106 rotates. An image formation start position detection sensor 115 is provided upstream of the transfer roller 114 in the rotation direction of the intermediate transfer body 106 to determine the transfer position onto the sheet S. The transfer roller 114 presses the sheet S against the intermediate transfer body 106 and at the same time applies a bias with reverse characteristics to the image on the intermediate transfer body 106, thereby transferring the image from the intermediate transfer body 106 to the sheet S.

The feeding mechanism includes a paper feed cassette 113 that stores sheets S, a transport path along which the sheets S are fed, and various rollers for transporting the sheets S to the transport path. The sheets S are fed from the paper feed cassette 113, and while being transported along the transport path, an image is transferred and fixed onto the sheets S to form an image, and the sheets S are then discharged outside the housing 101.

To achieve this, the sheet S is first fed from the paper feed cassette 113 and transported along a transport path to the transfer roller 114. A paper feed timing sensor 116 is provided along the transport path from the paper feed cassette 113 to the transfer roller 114 to adjust the transport timing of the sheet S. The timing at which the sheet S is transported to the transfer roller 114 is adjusted based on the timing at which the image formation start position detection sensor 115 detects the image on the intermediate transfer body 106 and the timing at which the paper feed timing sensor 116 detects the sheet S. This allows the image to be transferred from the intermediate transfer body 106 to a predetermined position on the sheet S.

The sheet S onto which the image has been transferred is transported to the fixing mechanism. The fixing mechanism of this embodiment includes a first fixing device 150 and a second fixing device 160. The first fixing device 150 includes a fixing roller 151 for heating the sheet S in order to thermally press the image onto the sheet S, a pressure belt 152 for pressing the sheet S against the fixing roller 151, and a post-fixing sensor 153 for detecting the completion of fixing. The fixing roller 151 is a hollow roller having an internal heater 1510 and configured to transport the sheet S by rotating. The pressure belt 152 presses the sheet S against the fixing roller 151. The post-fixing sensor 153 detects the sheet S after the image has been fixed.

The second fixing device 160 is disposed downstream of the first fixing device 150 in the conveying direction of the sheet S, and is used to add gloss to the image on the sheet S fixed by the first fixing device 150 and to ensure fixability. The second fixing device 160 has a fixing roller 161, a pressure roller 162, and a post-fixing sensor 163. The fixing roller 161 has the same configuration as the fixing roller 151, and functions in the same way. The pressure roller 162 functions in the same way as the pressure belt 152. The post-fixing sensor 163 functions in the same way as the post-fixing sensor 153. The second fixing device 160 performs a fixing process on the sheet S in the same way as the first fixing device 150.

The second fixing device 160 may not be used depending on the type of sheet S and the contents of the image forming process. The transport path 130 is provided to transport the sheet S that has been fixed by the first fixing device 150 without passing through the second fixing device 160. For this reason, a flapper 131 is provided downstream of the first fixing device 150 in the transport direction of the sheet S to guide the sheet S to either the second fixing device 160 or the transport path 130.

After passing through either the second fixing device 160 or the transport path 130, the sheet S may be discharged as is or transported to the transport path 135. For this reason, a flapper 132 is provided after the transport path after the second fixing device 160 and the transport path 130 join together. The flapper 132 guides the sheet S to either the transport path 135 or a discharge path for the sheet S. The sheet S guided to the discharge path is discharged outside the housing 101 with the side on which the image is formed facing up.

The conveying path 135 is a path for conveying the sheet S to the inversion path 136 used for inverting the front and back sides of the sheet S. The inversion path 136 is provided with an inversion sensor 137 for detecting the sheet S. When the inversion sensor 137 detects the rear end of the sheet S, the conveying direction of the sheet S is inverted in the inversion path 136. The sheet S whose conveying direction has been inverted is conveyed to either the conveying path 135 or the inversion path 138. For this purpose, a flapper 133 is provided at the branch point between the conveying path 135 and the inversion path 138. When conveyed to the conveying path 135, the sheet S is guided to the conveying path 135 by the flapper 133, and the front and back sides are inverted (with the side on which the image is formed facing downward) and discharged to the outside of the housing 101. When conveyed to the inversion path 138, the sheet S is guided to the inversion path 138 by the flapper 133. The sheet S guided to the inversion path 138 is inverted and conveyed to the transfer roller 114 again. This allows the image to be formed on the back side of the sheet S.

(Automatic reading device)
2 is a schematic diagram of the automatic reading device 400. The automatic reading device 400 is connected to the rear stage of the printer 100, and a sheet S is supplied from the printer 100 to the automatic reading device 400. The automatic reading device 400 has two transport paths, a through path 431 and a reading path 432. The through path 431 is a transport path through which the sheet S passes when it is transported from the image forming device 100 to a paper discharge device 600 connected to the rear stage of the automatic reading device 400. The reading path 432 is a transport path through which the sheet S passes when it is discharged to a discharge tray 423 of the automatic reading device 400. The through path 431 is provided with transport rollers 401, 402, 403, and a discharge roller 404. The reading path 432 is provided with a plurality of transport rollers 405, 406, 407, and a discharge roller 408.

A sheet sensor 421 is disposed between the conveying roller 405 and the conveying roller 406. A color measurement unit 500 that functions as a reading unit for reading an image on the sheet S is disposed between the conveying roller 406 and the conveying roller 407. The color measurement unit 500 reads an image of the sheet S located between the conveying roller 406 and the conveying roller 407 while moving in a direction intersecting the conveying direction in which the sheet S is conveyed by the conveying roller 406 (first roller) and the conveying roller 407 (second roller). Here, the moving direction of the color measurement unit 500 is a direction perpendicular to the paper surface of FIG. 2. In order for the color measurement unit 500 to read the multiple patch images formed on the sheet S, the sheet S on which the multiple patch images are formed is conveyed intermittently, and the color measurement unit 500 performs a reading operation while moving in the moving direction while the conveyance of the sheet S is stopped.

The sheet S sent from the printer 100 is transported by transport rollers 401, 402, and 403 to the branching point between the through path 431 and the reading path 432. At the branching point, the sheet S is transported to either the through path 431 or the reading path 432. A flapper 422 that switches the destination of the sheet S is provided at the branching point between the through path 431 and the reading path 432.

When the sheet S is conveyed directly through the through path 431, the sheet S is guided by the flapper 422 toward the discharge roller 404 and discharged to the paper discharge device 600, which serves as a post-processing device connected downstream of the automatic reading device 400. The paper discharge device 600 discharges the sheet S to a paper discharge tray. Note that the paper discharge device 600 may be a post-processing device that performs post-processing such as binding or bookbinding on the sheet S before discharging the sheet S.

When the sheet S is transported to the reading path 432, the sheet S is guided to the reading path 432 by the flapper 422. The sheet S guided to the reading path 432 is discharged to the discharge tray 423 by the discharge rollers 408 after the patch image is read by the color measurement unit 500. The color measurement unit 500 is an in-line sensor that reads an image from the sheet S transported along the reading path 432.

(Color measurement unit)
3 is a cross-sectional view of a main part of the color measurement unit 500. The color measurement unit 500 includes an image sensor 551. The image sensor 551 includes a white LED (Light Emitting Diode) 501, a diffraction grating 502, a line sensor 503, a calculation unit 504, a memory 505, and a lens 506. The image sensor 551 reads an image formed on the sheet S while moving in a main scanning direction (depth direction in FIG. 2 ) perpendicular to the conveying direction of the sheet S. A movement mechanism for moving the image sensor 551 in the main scanning direction will be described later.

The white LED 501 is a light emitting unit that irradiates white light onto the sheet S transported along the reading path 432. The diffraction grating 502 separates the light reflected by the patch image P into separate wavelengths. The lens 506 focuses the white light irradiated from the white LED 501 onto the patch image P, and also focuses the light reflected by the patch image P onto the diffraction grating 502.

The line sensor 503 is a light receiving unit having n light receiving elements 503-1 to 503-n. Each light receiving element 503-1 to 503-n of the line sensor 503 receives reflected light that has been separated into wavelengths by the diffraction grating 502. Each light receiving element 503-1 to 503-n outputs, as a detection result, for example, a light intensity value that represents the intensity of the received reflected light. The calculation unit 504 performs a predetermined calculation on the light intensity values output from each light receiving element 503-1 to 503-n. For example, the calculation unit 504 calculates spectroscopic calculations and Lab values for the light intensity values. The memory 505 stores various data such as the calculation results.

(controller)
4 is a control block diagram of the image forming apparatus 1. The printer 100 is provided with a printer controller 103 for controlling the operation of the printer 100 and an engine control unit 312 for controlling the operation of an image forming engine for image formation, as controllers. The automatic reading device 400 is provided with a control unit 451 for controlling the operation of the automatic reading device 400 and a communication unit 450 for communicating with the printer controller 103.

The engine control unit 312 is connected to the post-fixing sensors 153 and 163, the inversion sensor 137, the drive motor 311 that drives each roller that transports the sheet S, and the flappers 131 and 132. The engine control unit 312 controls the drive motor 311 and the flappers 131 and 132 based on the detection results of each sensor, thereby causing the image forming engine unit to transport the sheet S. Although not shown in the figure, the engine control unit 312 also controls the operation of the image forming mechanism, transfer mechanism, feeding mechanism, and fixing mechanism to form an image on the sheet S. The operation of the engine control unit 312 is controlled by the printer controller 103.

The printer controller 103 is connected to an operation panel 180 and an external I/F 308. The external I/F 308 is a communication interface that communicates with external devices via a specified network. The printer controller 103 can receive jobs and the like from external devices via the external I/F 308. The operation of the printer controller 103 will be described in detail later.

The control unit 451 of the automatic reading device 400 incorporates a CPU 453, a ROM 455, and a RAM 454, and controls the automatic reading device 400 by a control program stored in the ROM 455. The RAM 454 temporarily stores control data and is used as a working area for calculation processing associated with control. The automatic reading device 400 is also connected to the printer control unit 900 so that it can communicate with it.

The control unit 451 of the automatic reading device 400 is further connected to the conveying motor 452, the sheet sensor 421, the flapper 422, and the color measurement unit 500. The control unit 451 communicates with the printer controller 103 via the communication unit 450 and performs processing in cooperation with the printer controller 103. The control unit 451 controls the operation of the conveying rollers 401, 402, 403, the discharge roller 404, the conveying rollers 405, 406, 407, and the discharge roller 408 in the automatic reading device 400 by the conveying motor 452 to convey the sheet S. The control unit 451 controls the operation of the flapper 422. The control unit 451 controls the operation of the color measurement unit 500 according to the timing when the sheet sensor 421 detects the sheet S, and detects the patch image P on the sheet S.

(Basic adjustment process)
In the image forming apparatus 1 of this embodiment, a patch image P for maintaining image quality is formed on a sheet S by the printer 100. The printer 100 conveys the sheet S on which the patch image P is formed to the automatic reading device 400. The automatic reading device 400 reads the patch image P formed on the sheet S by a color measurement unit 500 (image sensor 551). The printer controller 103 performs feedback control based on the detection result (reading result) by the image sensor 551 to maintain image quality such as color reproducibility. To this end, the printer controller 103 corrects the image forming conditions by the printer 100 based on the color measurement result by the color measurement unit 500 in order to maintain image quality such as color reproducibility.

The image forming device 1 creates a profile as the image formation conditions, converts image data using the created profile, and forms an image based on the converted image data. In the following, an ICC profile is used as a profile that achieves excellent color reproducibility. Note that the profile can also be a CRD (Color Rendering Dictionary), a color separation table, a CMYK simulation in ColorWise, or the like.

(Spectral reflectance measurement, chromaticity calculation)
The image sensor 551 detects reflected light from the patch image P and detects reflected light from a white reference board (not shown). The calculation unit 504 calculates the spectral reflectance R(λ) of the patch image P from the detection results of the patch image P and the white reference board. Here, λ means a wavelength corresponding to each pixel of the line sensor 503.

The image sensor 551 splits the white light emitted from the white LED 501 by the measurement object into light reflected by the object using the diffraction grating 502, and detects the light using light receiving elements 503-1 to 503-n arranged in the wavelength range of 380 nm to 720 nm. When the line sensor 503 receives the light reflected from the patch image P, the output value of each pixel of the line sensor 503 is acquired as the spectral data P(λ) of the patch image. When the line sensor 503 receives the light reflected from the white reference plate, the output value of each pixel of the line sensor 503 is acquired as the spectral data W(λ) of the white reference plate. The calculation unit 504 calculates the spectral reflectance R(λ) of the patch image P by dividing the spectral data P(λ) by the spectral data W(λ) of the white reference plate. The spectral reflectance R(λ) of the patch image P is then input to the Lab calculation unit 303.

The Lab calculation unit 303 converts the spectral reflectance R (λ) of the patch image P into color data expressed by L*, a*, and b* using color matching functions in accordance with CIE regulations. An ICC profile, which is a color conversion profile, is created based on the relationship between the color data and the signal value (image data) of the patch image P.

(L*a*b* operation)
The following is a method for calculating color data (L*a*b*) from spectral reflectance R (λ) (specified in ISO 13655).

a. Calculate the spectral reflectance R (λ) of the sample (380 [nm] to 780 [nm])
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, and SD50(λ) is specified in JIS Z8720, and is also called auxiliary standard illuminant D50.

c. R (λ) × SD50 (λ) × x (λ), R (λ) × SD50 (λ) × y (λ), R (λ) × SD50 (λ) × z (λ)
d. Integration of each wavelength Σ{R(λ)×SD50(λ)×x(λ)}
Σ{R(λ)×SD50(λ)×y(λ)}
Σ{R(λ)×SD50(λ)×z(λ)}
e. The product of the color matching function y(λ) and the standard light spectral distribution SD50(λ) is integrated for each wavelength.
Σ{SD50(λ)×y(λ)}
f. XYZ calculation 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. Calculation of L*, a*, b* 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)}
When Y/Yn>0.008856: Xn, Yn, and Zn are standard optical tristimulus values (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
(Create a profile)
When a customer engineer replaces a part, before a job that requires color matching accuracy is performed, or when the color of the final output is desired at the design concept stage, the user instructs the creation of a profile through the operation panel 180. The printer controller 103 creates a profile in response to an instruction from the operation panel 180.

As shown in FIG. 4, the printer controller 103 includes a profile creation unit 301, a Lab calculation unit 303, an output ICC profile storage unit 305, a CMM 306, and an input ICC profile storage unit 307.

An instruction to create a profile is input from the operation panel 180 to the profile creation unit 301. In response to the instruction, the profile creation unit 301 sends patch image data called an ISO 12642 test form to the engine control unit 312 to form the patch image data without going through a profile. At the same time, the printer controller 103 sends a color measurement instruction to the image sensor 551. The engine control unit 312 controls the operation of the printer 100 to print an ISO 12642 test form (patch image) on the sheet S. The sheet S on which the test form (patch image) is printed is measured by the image sensor 551. The spectral reflectance of the measured 928 patch image is input to the printer controller 103. The spectral reflectance is converted to color data (L*, a*, b*) by the Lab calculation unit 303 and input to the profile creation unit 301. Note that the color data is not limited to L*, a*, b*, and may be converted to color data (X, Y, Z) expressed using the CIE 1931 XYZ color system.

The profile creation unit 301 creates an output ICC profile based on the relationship between the CMYK color signals of the test form and the input color data. The profile creation unit 301 replaces the output ICC profile already stored in the output ICC profile storage unit 305 with the output ICC profile that it created.

The ISO12642 test form includes patch images of CMYK color signals that cover the color reproduction range that a typical copier can output. The profile creation unit 301 creates a color conversion table from the relationship between the image signal values (color signal values) used to form patch image P and the color data as the colorimetric result of patch image P. In other words, a conversion table (A2Bx tag) is created that converts each signal value of cyan (C), magenta (M), yellow (Y), and black (K) into L*, a*, and b* values. Based on this conversion table, an inverse conversion table (B2Ax tag) is created.

The printer controller 103 may also receive an instruction to create a profile from an external device via the external I/F 308. In this case, the printer controller 103 obtains the output ICC profile created by the external device and performs color conversion using an application that corresponds to that ICC profile.

(Color conversion processing)
In color conversion in normal color image formation, image data inputted assuming RGB signal values or standard printing CMYK signal values such as Japan Color inputted through an external I/F 308 is stored in an input ICC profile storage unit 307 for external input. In this case, a scanner or a DFE (Digital Front End Processor) is connected to the external I/F 308 as an external device. When the connected external device is a scanner, the image data stored in the input ICC profile storage unit 307 is converted from RGB to L*a*b* or CMYK to L*a*b*. The input ICC profile is composed of a one-dimensional LUT that controls the gamma value of the input signal, a multi-color LUT called direct mapping, and a one-dimensional LUT that controls the gamma value of the generated conversion data. Using these tables, the image data stored in the input ICC profile storage unit 307 is converted from a device-dependent color space to device-independent L*a*b* data.

Figure 5 is an explanatory diagram of color management by the CMM 306. Image data converted into L*a*b* chromaticity coordinates is input to the CMM 306. The CMM 306 performs GUMAT conversion to map mismatches between the reading color space of an external device such as a scanner and the output color reproduction range of the printer 100 as an output device. The CMM 306 also performs color conversion to adjust the mismatch between the light source type at the time of input and the light source type when observing the output (also called the mismatch of the color temperature setting), and performs black character judgment, etc. As a result, the L*a*b* data is converted to L*'a*'b*' data and stored in the output ICC profile storage unit 305. As described above, the created profile is stored in the output ICC profile storage unit 305, and is color converted by the newly created ICC profile, converted into a CMYK signal dependent on the output device, and output. As shown in Figure 5, the CMM 306 is a module that performs color management. CMM306 is a module that performs color conversion using input and output profiles.

If the connected external device is a DFE (Digital Front End Processor), a color measurement instruction is sent to the printer 100 from the external I/F 308. The sent color measurement instruction is transmitted from the printer controller 103 to the engine control unit 312, and sent from the communication unit 139 to the communication unit 450 of the automatic reading device 400. After that, test form (patch image) chart data is sent to the printer 100 from the external I/F 308. The printer 100 prints the sent patch image chart data and transports the patch image chart to the automatic reading device 450.

The number of patch lines in the patch image chart data sent from the external I/F 308 varies depending on the type of DFE (Digital Front End Processor) and the purpose of each DFE (profile creation, color verification, etc.).

(DFE Calibration)
The DFE connected to the image forming apparatus 1 instructs the image forming apparatus 1 to execute DFE calibration. DFE calibration is a process for generating a conversion table (γLUT) for tone correction used by the DFE so that a target tone predetermined for each type of sheet is achieved. For example, the DFE generates measurement image data and transfers the measurement image data to the printer 100 of the image forming apparatus 1. This causes the printer 100 to form a patch image for DFE calibration on the sheet S. The sheet S on which the patch image is formed may be called a test chart.

Furthermore, the DFE notifies the automatic reader 600 via the printer 1 of the number of patch lines when reading the patch image for DFE calibration. As a result, the color measurement unit 500 of the automatic reader 400 reads the patch image for DFE calibration formed on the sheet S, and transmits the read data (spectral reflectance) related to the patch image for DFE calibration to the DFE. When the DFE receives the read data (spectral reflectance) related to the patch image for DFE calibration, it converts the read data into density data, and generates a γLUT for each type of sheet based on the density data of each patch image and the target density for each type of sheet. In other words, a γLUT for each type of sheet is generated so that the target gradation is realized. For example, a γLUT for coated paper, a γLUT for plain paper, a γLUT for thick paper, and a γLUT for thin paper are generated. The DFE associates the generated γLUT with the type of sheet and stores it in the memory within the DFE.

The DFE converts image data based on the γLUT and transfers the converted image data to the printer 100, thereby controlling the density of the image formed by the printer 100 to the target density for each sheet type. The γLUT functions as a conversion condition for converting image data.

(Color measurement unit)
6, 7, and 8 are explanatory diagrams of a moving mechanism that moves the image sensor 551 in the main scanning direction. The color measurement unit 500 includes a moving mechanism in addition to the image sensor 551. The moving mechanism includes a moving unit 530 for moving the image sensor 551 in the main scanning direction, a moving drive motor 570 that drives the moving unit 530, and unit detection sensors 545 and 546. Although not shown, the image sensor 551 is attached to the moving unit 530. As peripheral components of the moving mechanism, a conveying roller unit 580 that conveys the sheet S in the a direction, and a conveying drive unit 590 that drives the conveying roller unit 580 are arranged. Drive control of the moving drive motor 570 and the conveying drive unit 590 is performed by the control unit 451.

When the sheet S is transported by the transport roller unit 580 to the reading position 551S of the image sensor 551, the moving unit 530 starts moving the image sensor 551 in the main scanning direction (direction b). The timing at which the sheet S is transported to the reading position of the image sensor 551 is determined based on the timing at which the sheet sensor 421 detects the sheet S, the position at which the sheet sensor 421 detects the sheet S, and the transport speed of the sheet S. The image sensor 551 reads (measures the color) the image of the sheet S while moving in the main scanning direction.

The transport roller unit 580 has an upstream transport drive roller 581 and an upstream transport driven roller 582 on the upstream side of the image sensor 551 in the transport direction (direction a) of the sheet S. The transport roller unit 580 also has a downstream transport drive roller 583 and a downstream transport driven roller 584 on the downstream side of the image sensor 551 in the transport direction of the sheet S. The transport roller unit 580 transports the sheet S transported from the transport roller 406 to the transport roller 407 via the reading position 551S (detection position).

In this embodiment, the upstream transport drive roller 581 and the downstream transport drive roller 583 are driven by a single transport drive unit 590. Alternatively, a transport drive unit may be provided for each of the upstream transport drive roller 581 and the downstream transport drive roller 583, and the upstream transport drive roller 581 and the downstream transport drive roller 583 may be driven and controlled individually.

(Color measurement operation)
FIG. 9 illustrates an example of the posture of the image sensor 551 of the sheet S transported through the reading path 432 at the reading position 551S. The reading path 432 is provided so that the sheet S is transported vertically from bottom to top. The color measurement unit 500 reads (measures) patch images from the sheet S transported vertically. The sheet S and FIG. 10 are explanatory diagrams of the patch image reading process by the color measurement unit 500. A predetermined number of patch images are formed on the sheet S in the row direction and the column direction. In this embodiment, m rows of patch images P for color measurement, P1 to Pm, are formed on the sheet S. In each row, n patch images, P1-1, P1-2, P1-3, . . . P1-n, are formed in the column direction. In other words, m×n patch images are arranged on one sheet S.

As described above, the image sensor 551 is moved in the main scanning direction perpendicular to the conveying direction of the sheet S by the moving unit 530. When the patch image is read by the image sensor 551, the conveying/stopping of the sheet S is controlled by the conveying roller unit 580, and it is possible to convey the sheet S a predetermined amount. The conveying drive unit 590 repeats the operation of conveying the sheet S a predetermined amount and pausing it by the conveying roller unit 580. The position of the sheet S is detected by a sheet position detection sensor (not shown). The image sensor 551 moves in the main scanning direction while the sheet S is paused, and reads one line of patch images. When moving from the front to the back of the device in the main scanning direction, the moving unit 530 moves from the left to the right of the sheet in FIG. 10, and when the unit detection sensor 546 detects the moving unit 530, the driving of the moving unit 530 is stopped. Conversely, when moving from the back side of the device to the front side in the main scanning direction, the moving unit 530 moves from the right side to the left side of the sheet in FIG. 10, and when the unit detection sensor 545 detects the moving unit 530, the driving of the moving unit 530 is stopped.

As shown in FIG. 10(a), when the sheet S is transported to the reading position 551S of the image sensor 551, the image sensor 551 retreats to a position outside the area of the sheet S in the main scanning direction and waits. Here, outside the area refers to a position where the unit detection sensor 545 is turned on when the image sensor 551 is at the front side of the device, and a position where the unit detection sensor 546 is turned on when the image sensor 551 is at the rear side of the device. The sheet S is transported and stopped until the reading position 551S of the image sensor 551 and the position of the patch image P1 of the first row are aligned in the transport direction. When the transport of the sheet S is stopped, the image sensor 551 moves in the main scanning direction as shown in FIG. 10(b) and reads the patch images P1-1 to P1-n of n rows P1.

In the above description, an example in which the color measurement unit 500 is provided in the automatic reading device 400 has been described, but the automatic reading device 400 may be provided inside the printer 100. For example, a reading path 432 in which the color measurement unit 500 is located may be provided after the second fixing device 160 and the conveying path 130 join together.

(Calibration operation flow)
The sequence executed by the CPU 453 of the automatic reading device 400 in calibration using the automatic reading device 400 will be described below with reference to the flowcharts shown in Figs. 11 and 12. Note that, in the following, the types of calibration will be described using DFE calibration (referred to as calibration 1) and profile creation (referred to as calibration 2) as examples. Also, the flowcharts in Figs. 11 and 12 explain an example in which a color measurement instruction is input for a patch image P laid out by the printer 100 based on the type of calibration and the size of the sheet S.

The CPU 453 accepts the type of calibration input using the operation panel 180, and acquires information on the size of the sheets S to be used for the calibration using the color measurement communication unit 450. Based on the input information on the size of the sheets S, the CPU 453 determines the number of sheets S on which patch images P are formed and the number of patch lines when reading the patch images P on each sheet S. The color measurement communication unit 450 functions as an acquisition unit that acquires information on the size of the sheets S on which the patch images P are formed, which is input via the operation panel 180. The color measurement communication unit 450 also functions as an output unit that outputs read data related to the patch images P when the patch images P are read in each calibration.

For example, if A3 size is selected in calibration 1, the number of sheets S on which patch images P are formed is two, the first sheet has eight patch lines, and the second sheet has four patch lines. For example, if A4 size is selected in calibration 1, the number of sheets S on which patch images P are formed is four, the first to third sheets have four patch lines, and the fourth sheet has two patch lines.

For example, if A3 size is selected in calibration 2, the number of sheets S on which patch image P is formed is two, and the number of patch lines on the first and second sheets is eight. For example, if A4 size is selected in calibration 2, the number of sheets S on which patch image P is formed is four, and the number of patch lines on the first to fourth sheets is four.

Then, based on the number of sheets S on which patch images P are formed and the number of patch lines, the CPU 453 controls the number of times that the conveying rollers 406 and 407 convey the sheet S intermittently and the number of times that the color measurement unit 500 moves in a direction intersecting the conveying direction of the sheet S.

(Calibration 1)
The colorimetry instruction for the patch image sheet is sent from the operation panel 180 or the external I/F 308 to the colorimetry communication unit 450 of the automatic reader 400 via the engine communication unit 139 of the printer 100. In this embodiment, the information of the colorimetry instruction for calibration 1 includes at least the calibration mode (type) and the paper size. When the colorimetry instruction is received and a job is started, the patch image sheet counter variable Sheet is cleared to 0.

When a color measurement instruction is received, the CPU 453 transitions to S1001 and sets the variable ReadLineCnt, which indicates which line of the color measurement patch is to be measured, to 0. Then, the CPU 453 transitions to S1002 and determines the number of patch lines to be measured on the patch image chart. In S1002, the variable LineCnt, which indicates the number of patch lines to be measured, is determined.

When the CPU 453 starts step S1002, it transitions the process to S1101, sets the calibration mode (type) received by the colorimetric communication unit 450 to the variable CAL, and checks the value of the variable CAL (S1102).

If it is determined that this is a request for calibration 1 (S1102: Yes), a check is made to see if the patch image sheet counter variable Sheet is 0 (S1103). The variable Sheet indicates the number of patch image sheets to be measured, and when multiple patch image sheets are used for color measurement, it is possible to determine which patch image sheet is to be measured. If Sheet is 0 (S1103: Yes), the process moves to S1104, where the paper size information received by the color measurement communication unit 450 is set to the variable Size, and the process moves to S1105, where a check is made to see if it is large size (A3 size).

In the case of large size (S1105: Yes), the variable SheetMax is set to 2 (S1106). In the case of small size (A4 size) (S1105: No), the variable SheetMax is set to 4 (S1110). Next, proceed to S1107 to determine the number of patch lines to be printed on each patch image sheet. In the case of large size, the first patch image sheet is determined to have 8 lines, and the second patch image sheet to have 4 lines. In the case of small size, the first patch image sheet is determined to have 4 lines, the second patch image sheet to have 4 lines, the third patch image sheet to have 4 lines, and the fourth patch image sheet to have 2 lines. Next, proceed to S1108 to set the patch image sheet counter variable Sheet to the first sheet, and proceed to S1109 to set the number of patch lines for the first sheet determined in S1107 to the variable LineCnt. Then, the processing of S1002 ends.

The values of these variables SheetMax and LineCnt are notified in advance based on the print settings notified by the DFE.

The condition (S1103: No) applies when this is the second or subsequent patch image sheet. For example, in the case of a large size, when measuring the second patch image sheet (S1103: No), the process moves to S1111, where Sheet is set to the second sheet, and the process moves to S1112, where the variable LineCnt is set to the fourth line of the second sheet. Next, the process moves to 1113, and if the variable Sheet is the same as the value of the variable SheetMax (S1113: Yes), it is determined that this is the final patch image sheet, and the variable Sheet is set to 0. S1111: If No, the value of the variable Sheet is maintained. Then the process of S1002 ends.

(Calibration 2)
If it is determined in step S1102 that the instruction is not for calibration 1, it is determined whether it is for calibration 2 (S1115). If it is determined in step S1115 that the instruction is for calibration 2 (S1115: Yes), the number of lines in the colorimetry instruction received by the colorimetry communication unit 450 is set to the variable LineCnt (S1116).

In this embodiment, the color measurement instruction information for calibration 2 includes at least the calibration mode (type) and the number of lines.

In this case, if it is determined that calibration 2 is being performed (S1115: Yes), it is determined that the number of patch lines is dynamically variable for each patch image sheet. Therefore, the number of lines received by the colorimetry communication unit 450 for each patch image sheet is set to the variable LineCnt.

Furthermore, the number of patch image sheets used and the number of patch lines on each patch image sheet are not determined. Then, processing of S1002 ends.

In this case, by setting the number of lines notified by the DFE to the variable LineCnt for each patch image sheet, the appropriate number of lines can be read even if the number of patch lines on the patch image sheet changes dynamically.

If the content of the variable CAL is neither calibration 1 nor calibration 2, the process proceeds to S1117. In S1117, the paper size information received by the colorimetry communication unit 450 is set to the variable Size, and the process proceeds to S1118 to check whether the size is large. If the size is large (S1118: Yes), the maximum number of patch lines that can be measured at large size (a fixed value is set) is set to the variable LineCnt (S1119). If the size is small (S1118: No), the maximum number of patch lines that can be measured at small size (a fixed value is set) is set to the variable LineCnt (S1120). Then the process of S1001 ends.

In addition, the type of calibration using the automatic reading device 400 is not limited to profile creation and DFE calibration, but may also be calibration involving verification or the formation of other patches.

(Color measurement operation of patch image sheet)
When the determination of the number of patch lines in S1002 is completed, the process proceeds to S1003, where the acquired value of LineCnt is set to a variable AllreadLincCnt that indicates the total number of patch lines to be measured on the patch image sheet.

Next, a patch image sheet is conveyed and the process waits until it stops at the color measurement position (the position of the color measurement start line P1 in FIG. 10(a)) (not shown). When the patch image sheet stops at the position of the color measurement start line, the process proceeds to S1004 and the moving unit 530 is moved from the front position to the back position. In parallel, the image sensor 551 performs patch color measurement processing (S1005).

When the image sensor 551 reaches the position in FIG. 10(c) (rear position) while measuring the P1 line in FIG. 10(a) and stops, the color measurement operation of the P1 line ends, and the variable readLineCnt, which indicates which row of the color measurement patch is to be measured, is incremented (S1006). Next, the process moves to S1007, where it is checked whether the value of the variable AllreadLincCnt has been reached. Since this is after the color measurement of the P1 line in FIG. 10, the value of the variable AllreadLincCnt (8) has not been reached. If the value of the variable readLineCnt has not reached the value of the variable AllreadLincCnt (S1007: No), the process moves to S1010. In S1010, the patch image sheet is moved to the color measurement line position of P2 in FIG. 10(c). Next, the process moves to S1011, where the moving unit 530 is moved from the rear position to the front position. In parallel, the image sensor 551 performs patch color measurement processing (S1012).

On the other hand, in step S1007, if the value of the variable readLineCnt reaches the value of the variable AllreadLincCnt, the moving unit 530 is moved from the rear position to the front position, and the process proceeds to S1008.

When the image sensor 551 reaches the front position while measuring the P2 line in FIG. 10(c) and stops, the color measurement operation of the P2 line ends, and the process proceeds to S1013, where the variable readLineCnt, which indicates which row of the color measurement patch is to be measured, is incremented.

Next, the process moves to S1014 to check whether the value of the variable AllreadLincCnt has been reached. Since this is after colorimetry of the P2 line in FIG. 10, the value of the variable AllreadLincCnt (8) has not been reached (S1014: No), so the process moves to S1015. In S1015, the patch image sheet is moved to the colorimetry line position of P3 (not shown) in FIG. 10. Next, the process moves to S1004 to move the moving unit 530 from the front position to the back position. In parallel, the image sensor 551 performs patch colorimetry processing (S1005).

The operations of S1004 to S1015 are repeated until the variable readLineCnt becomes 8. When the variable readLineCnt becomes 8, the variable AllreadLincCnt is reached (S1014: Yes), the process moves to S1008, and the patch image sheet is transported in the transport direction of FIG. 10 and discharged outside the automatic reading device 400.

When color measurement processing for one sheet is completed, the process transitions to S1040, where it is determined whether Sheet = 0, meaning color measurement processing for all sheets is complete. If Sheet = 0 is not true, the process returns to S1002 to perform color measurement on the next sheet, and the aforementioned patch line number determination flow and actual color measurement processing are performed in the same manner. If Sheet = 0, it is determined that color measurement processing for all sheets is complete, and the color measurement processing ends (S1009).

As explained above, when calibrating an ICC profile or the like using an external device, even if the patch lines are changed as necessary, the number of lines that are changed can be read, allowing color measurement to be performed efficiently and in the optimal measurement time.

100 Printer 406 Conveying roller 407 Conveying roller 450 Color measurement communication unit 453 CPU
500 Colorimetric Unit

Claims (4)

an image forming means for forming a test image on a sheet;
A conveying means having a plurality of rollers and conveying the sheet;
a reading means for reading the sheet while moving in a width direction intersecting a conveying direction in which the sheet is conveyed by the conveying means and while the conveying means is conveying the sheet intermittently, the reading means reads the sheet while moving in the width direction.
A receiving means for receiving a selection result of a calibration selected from a plurality of calibrations;
acquiring means for acquiring information regarding the size of the sheet on which the test image is to be formed;
a determination unit that, when a predetermined calibration is selected from the plurality of calibrations, determines, based on the information, the number of sheets on which the test image is to be formed and the number of multiple rows of patch lines aligned in the transport direction in the test image to be formed on each of the sheets, and a control unit that controls the number of transports when the transport unit repeats stopping and transporting while intermittently transporting the sheet and the number of movements of the reading unit in the width direction, based on the number of patch lines of each sheet determined by the determination unit ;
and an output unit for outputting a reading result of the test image read by the reading unit ,
the number of sheets in a case where the predetermined calibration is formed on A3 size sheets is less than the number of sheets in a case where the predetermined calibration is formed on A4 size sheets;
the A3 size sheet on which the predetermined calibration test image is formed includes a first sheet having a first number of patch lines and a second sheet having a second number of patch lines that is equal to or less than the first number,
the A4-sized sheets on which the predetermined calibration test images are formed include a third sheet having a third number of patch lines, and a fourth sheet having a fourth number of patch lines that is equal to or less than the third number;
an image forming apparatus characterized in that the number of times the reading means moves when reading the specified calibration test image on the first sheet of A3 size is greater than the number of times the reading means moves when reading the specified calibration test image on the third sheet of A4 size . 2. The image forming apparatus according to claim 1, wherein the reading means performs a first movement to a first side in the width direction and a second movement to a second side opposite to the first side in the width direction. A conversion means for converting image data based on a conversion condition;
generating means for generating the conversion condition based on the reading result output by the output means;
2. The image forming apparatus according to claim 1, wherein said image forming means forms an image based on the image data converted by said conversion means. The image forming device according to claim 1, characterized in that the reading means reads an area on the sheet located between a first roller included in the plurality of rollers and a second roller included in the plurality of rollers.

Images