Image reading devices, image forming devices

Abstract

To provide an image reading device that can read an image for detection with high accuracy in a short time while reducing the usage of sheets.SOLUTION: An image reading device comprises: a colorimetric sensor 207 that reads an image for detection including an image for colorimetry printed on a sheet and an image for position determination for detecting the state of the image for colorimetry; a colorimetric unit drive motor 206 that moves the colorimetric sensor 207 in a main scanning direction; a colorimetric unit conveyance motor 205 that conveys the sheet in a direction orthogonal to the main scanning direction; and a reader control unit 250 that detects the state of the image for colorimetry based on a result of reading of the image for position determination performed by the colorimetric sensor 207, and while controlling the movement of the colorimetric sensor 207 performed by the colorimetric unit drive motor 206 and the conveyance of the sheet performed by the colorimetric unit conveyance motor 205 based on the detected state of the image for colorimetry, causes the colorimetric sensor 207 to read the image for colorimetry.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image reading device that reads an image for color measurement formed on a sheet when an image forming apparatus adjusts an image formed on the sheet. [Background technology]

[0002] There are image forming systems that include an image reading device downstream of an image forming device such as a copier, printer, or multifunction device. In such image forming systems, the image forming device prints an image on paper, and the image reading device reads the image printed on the paper. The image reading device includes, for example, a spectrophotometer, and measures the color of the image on the paper.

[0003] For example, when adjusting the color of an image forming device, the image forming device forms a detection image for adjusting the color on a sheet of paper. Patent Document 1 discloses a technology for adjusting the color by reading the detection image printed on the sheet of paper by the image forming device with an image reading device and adjusting the image formation conditions when the image forming device forms an image based on the reading result. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-90255 Summary of the Invention [Problem to be solved by the invention]

[0005] The image reading device in Patent Document 1 reads a detection image using a fixed spectrophotometer while conveying paper. The detection image is composed of multiple color measurement images lined up in a line in the paper conveyance direction. The spectrophotometer sequentially reads the color measurement images from the conveyed paper. Therefore, in order to measure a multi-color image including mixed colors, it is necessary to print the detection images on a large amount of paper, which increases the amount of paper used and the color measurement time.

[0006] By moving the spectrophotometer in a direction perpendicular to the paper transport direction, it is also possible to read a detection image in which colorimetric images are arranged two-dimensionally. In this case, it is possible to form multiple colorimetric images on the paper. However, when reading colorimetric images arranged in two directions with a spectrophotometer, accuracy may decrease. For example, in the paper transport direction, variations in the paper stop position and variations in the image geometric characteristics may occur. In the direction perpendicular to the paper transport direction, there may be variations in the position where the image reading starts and variations in the image magnification. These variations and deviations reduce reading accuracy. This decrease in reading accuracy can be suppressed by enlarging the size of the colorimetric images. However, in this case, the number of colorimetric images that can be printed on one sheet of paper is reduced, resulting in increased paper usage.

[0007] The present invention has been made in view of the above-mentioned problems, and has as its main object to provide an image reading device that can read a detection image with high accuracy in a short time while reducing the amount of paper used. [Means for solving the problem]

[0008] The image reading device of the present invention includes a colorimetric measuring device that reads a detection image including a colorimetric image printed on a sheet of paper and a position measurement image for detecting a state of the colorimetric image, a moving device that moves the colorimetric measuring device in a first direction, a transporting device that transports the sheet of paper in a second direction perpendicular to the first direction, and a control device that detects a state of the colorimetric image based on a result of reading the position measurement image by the colorimetric measuring device, and controls the movement of the colorimetric measuring device by the moving device and the transporting of the sheet of paper by the transporting device based on the detected state of the colorimetric image, while causing the colorimetric measuring device to read the colorimetric image. The control means detects an amount of tilt of the color measurement image and an amount of deviation of the color measurement image in the first direction based on a reading result of the position measurement image, and controls movement of the color measurement means by the movement means and conveyance of the paper by the conveyance means based on the detected amount of tilt and amount of deviation. It is characterized by the following. [Effects of the Invention]

[0009] According to the present invention, it is possible to read an image for detection with high accuracy in a short time while reducing the amount of paper used. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an image forming system. [Figure 2] Controller configuration diagram. [Figure 3] FIG. 3 is a detailed explanatory diagram of a reader control unit. [Figure 4] FIG. [Figure 5] FIG. 10 is a diagram illustrating an example of an image for detection. [Figure 6] FIG. 10 is a diagram illustrating an example of a detection image including a position measurement image. [Figure 7] FIG. [Figure 8] FIG. 10 is an explanatory diagram of a method for calculating the distance between images. [Figure 9] 10 is a flowchart showing a color measurement operation. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, the embodiments will be described in detail with reference to the drawings.

[0012] (Image forming system) 1 is a diagram showing the configuration of an image forming system including an image reading apparatus according to this embodiment. The image forming system 1 includes an image forming apparatus 100, an image reading apparatus 200, and a finisher 300.

[0013] The image forming apparatus 100 forms an image based on image data generated by scanning a document or image data acquired from an external device (not shown) on paper based on image formation conditions to produce a printed product. The paper is stored in a paper feed unit 110. The printing process may be performed using, for example, an electrophotographic method or an inkjet recording method. In the electrophotographic method, the image forming apparatus 100 irradiates a photosensitive drum with laser light corresponding to the scanned data to form an electrostatic latent image, and then develops the electrostatic latent image with toner to produce a toner image. The image forming apparatus 100 transfers the toner image from the photosensitive drum to an intermediate transfer body, and then transfers the toner image transferred to the intermediate transfer body onto a paper sheet fed from the paper feed unit 110. The paper sheet onto which the toner image has been transferred is transported to a fuser. The fuser fuses the toner image to the paper sheet to produce a printed product. The printed product is cooled by a cooling fan 120 and transported to the image reading device 200.

[0014] The image reading device 200 includes an image reading unit 201 used to detect the printing position of an image on paper (printed material) transported from the image forming device 100, and a color measurement unit 202 used to detect the image density of the image on the paper.

[0015] The image reading unit 201 reads position marks used to align the printing positions of images on the front and back sides of paper, and a reference image for detecting the printing position of a detection image for adjusting color such as image density. The image reading unit 201 includes a first image reading unit 201a for reading the image on the front side of paper, and a second image reading unit 201b for reading the image on the back side of paper. When aligning the images on the front and back sides of paper, the image reading unit 201 notifies the image forming apparatus 100 of the positions of the read position marks. The image forming apparatus 100 adjusts the printing positions based on the notification from the image reading unit 201, thereby controlling the printing positions of the images on the front and back sides of paper to align.

[0016] When the image reading unit 201 reads the reference image, it notifies the image forming apparatus 100 of the detection of the reference image. The image forming apparatus 100 performs feedback control of the colorimetric unit 202 based on the notification from the image reading unit 201. The colorimetric unit 202 measures the color of the detection image formed on paper using a spectrophotometer. The colorimetric results are sent to the image forming apparatus 100 and used to correct the image formation conditions. Details of the colorimetric operation by the colorimetric unit 202 will be described later.

[0017] The image reading device 200 is equipped with an escape tray 203. Paper sheets on which detection images are formed are printed sheets dedicated to correcting image formation conditions, and are different from printed sheets corresponding to normal print jobs. Therefore, paper sheets on which detection images are formed are unnecessary printed sheets for the user. Paper sheets on which such detection images are formed are discharged to the escape tray 203. Normal printed sheets on which detection images are not formed are discharged from the image reading device 200 to the finisher 300.

[0018] The finisher 300 performs post-processing such as sorting and stapling instructed by the user on the printed materials conveyed from the image reading device 200. The finisher 300 discharges the printed materials after post-processing onto a printed material discharge tray 310.

[0019] (controller) 2 is a configuration diagram of a controller that controls the operation of the image forming system 1. The controller of the image forming system 1 is made up of control units provided in the image forming apparatus 100, the image reading apparatus 200, and the finisher 300, respectively.

[0020] Image forming apparatus 100 has a printer control unit 150, a control unit 170, a communication IF 161, and various loads 162 for performing image formation and paper transport. Printer control unit 150 is an information processing device having a CPU (Central Processing Unit) 151, a ROM (Read Only Memory) 152, and a RAM (Random Access Memory) 153. Printer control unit 150 has an ASIC (Application Specific Integrated Circuit) 154 as a dedicated device for controlling the various loads 162.

[0021] The CPU 151 controls the operation of the image forming apparatus 100 by executing a computer program stored in the ROM 152. The RAM 153 provides a work area for the CPU 151 when it executes processing. The ASIC 154 controls the operation of various loads 162 in accordance with instructions from the CPU 151. The CPU 151 executes image formation processing based on image data under predetermined image formation conditions, for example. At that time, the CPU 151 controls the operation of various loads 162 in the image forming apparatus 100 using the ASIC 154. Depending on the image formation conditions, the operation of each part of the image forming apparatus 100 during image formation is controlled, and the image density, print position, etc. of the image printed on paper are adjusted.

[0022] The control unit 170 has a CPU 171. An operation unit 172 is connected to the CPU 171. The operation unit 172 is an input interface such as input keys or a touch panel. In addition to the input interface, the operation unit 172 may also include an output interface such as a display or a speaker. The CPU 171 receives instructions and information input from the operation unit 172. The CPU 151 communicates with the CPU 171 and acquires the instructions and information received by the CPU 171. The CPU 151 controls the image forming apparatus 100 based on the acquired instructions and information.

[0023] The communication IF 161 is an interface that controls communication between the image reading device 200 and the finisher 300. The communication lines connected to the image reading device 200 and the finisher 300 via the communication IF 161 include a serial signal line and a parallel signal line including a power remote signal. The serial signal line allows serial data transmission and reception of information between the devices. When the image forming device 100 operates in cooperation with the image reading device 200 and the finisher 300, the CPU 151 communicates with the image reading device 200 and the finisher 300 via the communication IF 161 and transmits and receives necessary data, etc. The CPU 151 can also control the power supplies of the image reading device 200 and the finisher 300 by transmitting a power remote signal via the communication line.

[0024] The image reading device 200 has a reader control unit 250, a communication IF 261, and various loads 262 for transporting paper and reading images. The reader control unit 250 is an information processing device having a CPU 251, a ROM 252, a RAM 253, and an ASIC 254. The CPU 251 controls the operation of the image reading device 200 by executing a computer program stored in the ROM 252. The ASIC 254 is a dedicated device that controls the operation of the various loads 262 in accordance with instructions from the CPU 251. The communication IF 261 is an interface that controls communication between the image forming apparatus 100 and the finisher 300. When the image forming apparatus 100 operates in cooperation with the image reading device 200 and the finisher 300, the CPU 251 communicates with the image forming apparatus 100 and the finisher 300 via the communication IF 261, and transmits and receives necessary data, etc.

[0025] The finisher 300 includes a finisher control unit 350, a communication IF 361, and various loads 362 for paper transport and post-processing. The finisher control unit 350 is an information processing device including a CPU 351, a ROM 352, a RAM 353, and an ASIC 354. The CPU 351 controls the operation of the finisher 300 by executing a computer program stored in the ROM 352. The ASIC 354 is a dedicated device that controls the operation of the various loads 362 in accordance with instructions from the CPU 351. The communication IF 361 is an interface that controls communication between the image forming apparatus 100 and the image reading apparatus 200. When the image forming apparatus 100 operates in cooperation with the image reading apparatus 200 and the finisher 300, the CPU 351 communicates with the image forming apparatus 100 and the image reading apparatus 200 via the communication IF 361, and transmits and receives necessary data, etc.

[0026] 3 is a detailed explanatory diagram of the reader control unit 250. A colorimetric sensor 207, which is a spectrophotometer provided in the colorimetric unit 202, is connected to the CPU 251. A first image reading unit 201a, a second image reading unit 201b, a reading unit transport motor 204, a colorimetric unit transport motor 205, and a colorimetric unit drive motor 206 are connected to the ASIC 254 as various loads 262. The reading unit transport motor 204 is a drive source for transporting paper to the image reading unit 201. The colorimetric unit transport motor 205 is a drive source for transporting paper to the colorimetric unit 202. The colorimetric unit drive motor 206 is a drive source for moving the colorimetric sensor 207 in a direction (main scanning direction) perpendicular to the paper transport direction. The paper transport direction is the sub-scanning direction relative to the main scanning direction of the colorimetric sensor 207.

[0027] The ASIC 254 drives and controls the reading unit transport motor 204 to transport the paper to the reading positions of the first image reading unit 201a and the second image reading unit 201b, and controls the first image reading unit 201a and the second image reading unit 201b to read the image formed on the paper. The reading results by the first image reading unit 201a and the second image reading unit 201b are transmitted to the ASIC 254. The ASIC 254 transmits the reading results by the first image reading unit 201a and the second image reading unit 201b to the image forming apparatus 100 via the CPU 251 and the communication IF 261.

[0028] The ASIC 254 drives and controls the colorimetry unit transport motor 205 to transport the paper to the reading position of the colorimetry sensor 207. The ASIC 254 drives and controls the colorimetry unit drive motor 206 to move the colorimetry sensor 207 in the main scanning direction, causing the colorimetry sensor 207 to measure the color of the detection image formed on the paper. The colorimetry results from the colorimetry sensor 207 are transmitted to the CPU 251. The CPU 251 transmits the colorimetry results to the CPU 151 of the printer control unit 150 via the communication IF 261. The CPU 151 corrects the image formation conditions based on the colorimetry results acquired from the CPU 251, and adjusts the color tone, such as image density.

[0029] (Color measurement department) 4 is a configuration diagram of the colorimetric unit 202. The colorimetric unit 202 includes, from the upstream side in the paper transport direction, a paper leading edge detection sensor 407, a colorimetric unit upstream roller 404, a carriage 401 on which the colorimetric sensor 207 is mounted, and a colorimetric unit downstream roller 403. The carriage 401 is disposed on a carriage transport belt 402 and is movable in the main scanning direction. Within the movement range of the carriage 401, a left home position sensor 405 is disposed on the left side in the main scanning direction as viewed from the upstream side in the paper transport direction, and a right home position sensor 406 is disposed on the right side. The colorimetric sensor 207 of the carriage 401 reads the detection image printed on the paper while reciprocating between the left home position sensor 405 and the right home position sensor 406.

[0030] The leading edge of the paper conveyed to the colorimetry unit 202 is detected by a paper leading edge detection sensor 407. The detection result of the leading edge of the paper by the paper leading edge detection sensor 407 is sent to the CPU 251. When the CPU 251 detects the leading edge of the paper, the ASIC 254 controls the colorimetry unit conveyance motor 205, and the colorimetry unit upstream rollers 404 and the colorimetry unit downstream rollers 403 convey the paper to a predetermined position and stop it.

[0031] The carriage 401 moves in the main scanning direction as a carriage conveyor belt 402 is driven by a colorimetry unit drive motor 206. When the paper stops at a predetermined position, the CPU 251 drives the colorimetry unit drive motor 206 via the ASIC 254 to move the carriage 401 in the main scanning direction, while causing the colorimetry sensor 207 to read the detection image printed on the paper stopped at the predetermined position.

[0032] The position of the carriage 401 is detected by a left home position sensor 405 and a right home position sensor 406. When the colorimetric sensor 207 performs colorimetric operation for one line from left to right, the ASIC 254 drives the colorimetric unit drive motor 206 in a CW (clockwise) direction until the right home position sensor 406 detects the carriage 401. Conversely, when the colorimetric sensor 207 performs colorimetric operation for one line from right to left, the ASIC 254 drives the colorimetric unit drive motor 206 in a CCW (counterclockwise) direction until the left home position sensor 405 detects the carriage 401. This allows the colorimetric sensor 207 to move back and forth between the left home position sensor 405 and the right home position sensor 406.

[0033] As will be described in detail later, a reference image is formed at the beginning of the detection image in the movement direction of the carriage 401. The reference image is a single color, black. The colorimetric sensor 207 reads the reference image, thereby detecting the reading start position of the colorimetric sensor 207. The colorimetric sensor 207 transmits the timing at which the reading result (colorimetric value) changes from paper white to black to the CPU 251 as a timing trigger. The CPU 251 can measure the elapsed time from acquiring the timing trigger, that is, the elapsed time from the start of reading by the colorimetric sensor 207.

[0034] When reading of one line of the detection image in the main scanning direction is completed, the ASIC 254 drives the colorimetry unit transport motor 205 to transport the paper by one line. By alternately performing the colorimetry operation in the main scanning direction and paper feeding in this way, it is possible to read the detection image arranged two-dimensionally.

[0035] (Detection image) FIG. 5 is an exemplary diagram of a conventional detection image. The detection image in FIG. 5 includes one reference image and 22 color measurement images on one line in the main scanning direction. The detection image includes 18 lines of such one-line images in the paper transport direction (sub-scanning direction). Note that the number of color measurement images on one line and the number of lines are not limited to these. Note that the left HP indicates the position of the left home position sensor 405, and the right HP indicates the position of the right home position sensor 406.

[0036] For odd-numbered lines, a reference image L is provided at the left end, and 22 color measurement images are formed following the reference image L. For even-numbered lines, a reference image R is provided at the right end, and 22 color measurement images are formed following the reference image R. With this arrangement, the colorimetric sensor 207 reads the color measurement images while moving from left to right on the odd-numbered lines, and reads the color measurement images while moving from right to left on the even-numbered lines. The results of reading the color measurement images are used to correct the image formation conditions.

[0037] The size of both the reference image and the colorimetry image is 12 mm in the main scanning direction and 16 mm in the transport direction (sub-scanning direction). The paper size is A3, and the margin in the main scanning direction from the end of the detection image to the edge of the paper is 10.5 mm. The sum of the margin and the length of the detection image in the main scanning direction is 297 mm, which is the width of an A3-sized paper. In the transport direction (sub-scanning direction) of the paper, a margin of 66 mm is provided at each of the leading and trailing edges of the paper in the transport direction so that the paper is supported by the colorimetry unit upstream roller 404 and the colorimetry unit downstream roller 403. The sum of the margin and the length of the detection image in the transport direction is 420 mm, which is the length of an A3-sized paper.

[0038] The detection image conveyed to the colorimetry unit 202 may be tilted due to factors such as tilt caused by misalignment of the conveyance path between the image forming device 100 and the image reading device 200 during image formation, or tilt between the image and paper during image formation. Also, due to variations in the timing of paper conveyance by the colorimetry unit conveyance motor 205 and detection by the paper leading edge detection sensor 407, the detection image may be misaligned in the conveyance direction at the start of reading.

[0039] To ensure that the detection image can be read correctly even if the reading position is shifted due to these factors, margins are provided in the sizes of the reference image and colorimetric image. Specifically, a margin of 0.8 mm for paper skew and 0.2 mm for print skew is included in the main scanning direction, for a total of 1 mm. In the paper transport direction, a margin of 1.7 mm for paper skew, 0.4 mm for print skew, and 3.1 mm for detection timing variations are included. As a result, the sizes of the reference image and colorimetric image are increased, the number of colorimetric images per sheet is reduced, and the reading time is increased.

[0040] FIG. 6 is an example diagram of a detection image according to this embodiment, including a position measurement image. The position measurement image is composed of two rectangular position measurement images 601 and 603 and one parallelogram position measurement image 602, whose hypotenuse is at a 45° angle to the base. The position measurement images 601, 602, and 603 are used to detect the state of the colorimetric image. Specifically, the position measurement images 601 and 603 are used to measure the skew / magnification of the colorimetric image. The position measurement image 602 is used to measure the reading position of the colorimetric image. The results of reading the position measurement images 601, 602, and 603 suppress misalignment during reading, eliminating the need for a margin to correct the misalignment during reading. Therefore, the sizes of the reference image and colorimetric image can be smaller than those shown in FIG. 5. In this embodiment, the sizes of the reference image and colorimetric image are 11 mm in the main scanning direction and 10 mm in the transport direction (sub-scanning direction). A predetermined number of color measurement images are printed in the main scanning direction and a predetermined number of lines are printed in the transport direction. In this embodiment, since the size of the color measurement images is as described above, 24 color measurement images in the main scanning direction and 27 lines in the transport direction can be printed on one A3 sheet of paper.

[0041] The position measurement images 601, 602, and 603 are arranged closer to the leading edge of the paper than the color measurement images, and are read first by the color measurement sensor 207. Therefore, when reading the color measurement images, the reading results of the position measurement images 601, 602, and 603 suppress misreading during reading, and accurate reading results of the color measurement images can be obtained.

[0042] (Reading correction) FIG. 7 is an explanatory diagram of a method for measuring the position of a color measurement image using position measurement images 601, 602, and 603. In FIG. 7, the position measurement images 601, 602, and 603 in the first column of the detection image are read. The colorimetric sensor 207 reads the position measurement images 601, 602, and 603 in order from left to right in the main scanning direction. Each of the position measurement images 601, 602, and 603 is printed in black. As with the reference images L and R, the colorimetric sensor 207 sends a timing trigger to the CPU 251 when the read result changes from paper white to black.

[0043] The timing trigger is transmitted in the reading order of the position measuring image 601, the position measuring image 602, and the position measuring image 603. The CPU 251 operates a timer based on the timing trigger from the position measuring image 601, and measures the elapsed time between the position measuring images. The timer operates on a clock of, for example, 1 MHz, and buffers the count value of the timer and resets the counter when the timing trigger is detected.

[0044] When there is no tilt in the colorimetric image, the distance dr12 between the centers of the position measurement image 601 and the position measurement image 602 is equal to the distance dr23 between the centers of the position measurement image 602 and the position measurement image 603. In this embodiment, the distances dr12 and dr23 are both 120 mm. The scanning speed when the colorimetric sensor 207 moves in the main scanning direction is set to 100 mm / s. In this case, the count value of the timer is 1,200,000.

[0045] The reading result when the color measurement image is tilted will be described below. If the count value of the timer when reading the position measurement image 601 to the position measurement image 603 is 2,401,500, the distance d13 between the centers of the position measurement image 601 and the position measurement image 603 is expressed by the following formula: d13 = Count value / Timer clock*Scanning speed = 2,401,500 / 10^6 *100 = 240.15[mm]

[0046] The amount of inclination θ of the color measurement image at this time is expressed by the following formula. Tilt amount θ = cos -1 {d13 / (dr12+dr23)}

[0047] Thus, based on the measurement results of the respective distances between the position measurement image 601 and the position measurement image 602, and between the position measurement image 602 and the position measurement image 603, the tilt amount θ of the color measurement image can be calculated. Here, the tilt amount θ is 2°. Further, when d12 < d23 for the distance d12 between the position measurement image 601 and the position measurement image 602 and the distance d23 between the position measurement image 602 and the position measurement image 603, it is determined that the color measurement image is tilted clockwise. When d12 > d23, it is determined that the color measurement image is tilted counterclockwise.

[0048] When d12 = d23, the color measurement sensor 207 scans in the reverse main scanning direction to calculate the distance d32 between the position measurement image 603 and the position measurement image 602 and the distance d21 between the position measurement image 602 and the position measurement image 601. At this time, when d32 < d21, it is determined that the color measurement image is tilted clockwise, and when d32 > d21, it is determined that the color measurement image is tilted counterclockwise. In FIG. 7, the color measurement image is tilted counterclockwise by the tilt amount θ.

[0049] FIG. 8 is an explanatory diagram of a method for calculating the distance d12 between the position measurement image 601 and the position measurement image 602. FIG. 8 explains a method for calculating the deviation amount of the reading position. When the count value of the timer during reading from the position measurement image 601 to the position measurement image 602 is 1,2775,441, the base a and height b from the position measurement image 601 to the position measurement image 602 are expressed by the following equations. a = d12 * cosθ b = d12 * sinθ

[0050] In this example, the base a is calculated to be 127.45 [mm] and the height b is calculated to be 4.45 [mm]. At this time, the deviation amount e of the reading position in the main scanning direction of the position measurement image 602 is expressed by the following equation. Deviation amount e = a - b - 120

[0051] In this example, the amount of deviation e is 3 [mm]. In this manner, the amount of inclination θ of the color measurement image and the amount of deviation e of the reading position are calculated.

[0052] (Paper feed amount correction) The process of correcting the paper feed amount based on the tilt amount θ of the colorimetry image and the deviation amount e of the reading position calculated as above will be described below. The movement amount h of the colorimetry sensor 207 in the main scanning direction and the paper feed amount v in the paper transport direction (sub-scanning direction) are expressed by the following equations. Travel amount h = (240 * cosθ) / 20 Paper feed amount v = 16+e

[0053] Based on these calculation results, when reading the colorimetric image in the main scanning direction, the colorimetric sensor 207 reads the colorimetric image every time it moves in the main scanning direction by a movement amount h using the detection position of the reference image as a reference. Also, the colorimetric unit 202 feeds the paper in the sub-scanning direction by an amount obtained by adding the paper feed amount v and the deviation amount e of the reading position when reading the colorimetric image for the first row in the transport direction, and thereafter feeds the paper by the paper feed amount v.

[0054] By correcting the movement amount h of the colorimetric sensor 207 in the main scanning direction and the paper feed amount v in the transport direction (sub-scanning direction) in this way, the colorimetric unit 202 can perform colorimetric operations with high accuracy according to the printing state (tilt, misalignment) of the colorimetric image.

[0055] Furthermore, while reading the colorimetric image in the main scanning direction, the reading position of the colorimetric sensor 207 may deviate from the range of the colorimetric image in the transport direction. In this case, the colorimetric unit 202 may temporarily suspend the movement and reading operation of the colorimetric sensor 207 in the main scanning direction and transport the paper to the reading position of the colorimetric sensor 207. This makes it possible to read the colorimetric image even when the reading position deviates from a single line in the main scanning direction due to tilt of the colorimetric image.

[0056] Furthermore, image forming apparatus 100 may correct the printing position of the detection image based on the tilt amount θ of the color measurement image. In this case, CPU 151 acquires the tilt amount θ of the color measurement image from reader control unit 250 and corrects the image formation conditions according to the tilt amount θ. CPU 151 controls image formation on paper based on the corrected image formation conditions. Correcting the image formation conditions enables printing of an appropriate detection image according to the transport state of the paper after image formation.

[0057] (Color measurement operation) FIG. 9 is a flowchart showing the color measurement operation by the image reading device 200.

[0058] When a color measurement operation is instructed by the operation unit 172 or the like, the image forming apparatus 100 forms a detection image on a sheet of paper (S901). The detection image includes position measurement images 601, 602, 603 and a color measurement image. The sheet of paper on which the detection image has been formed is transported from the image forming apparatus 100 to the image reading apparatus 200 (S902).

[0059] The colorimetric unit 202 reads the position measurement images 601, 602, and 603 printed on the conveyed paper (S903). The CPU 251 of the reader control unit 250 calculates the tilt amount θ of the colorimetric image, the amount of deviation e of the reading position, the amount of movement h of the colorimetric sensor 207 in the main scanning direction, and the paper feed amount v in the paper conveyance direction based on the reading results of the position measurement images (S904). The CPU 251 controls the operation of the colorimetric unit 202 based on each calculation result to control the colorimetric operation of the colorimetric image (S905). Through the above processing, the colorimetric unit 202 corrects the reading position in the main scanning direction and the conveyance direction, and can accurately read the colorimetric image. This makes it possible to accurately adjust the color tone based on the reading results of the colorimetric image.

[0060] In this way, the image reading device 200 of this embodiment reads position measurement images 601, 602, and 603 to detect the state of the colorimetric image printed on paper. The reader control unit 250 acquires parameters related to the print state of the colorimetric image, such as the position, tilt, and magnification, based on the read results (detection results) of the position measurement images 601, 602, and 603. The reader control unit 250 corrects the paper feed amount during colorimetric measurement and the scanning amount in the main scanning direction of the colorimetric sensor 207. Such corrections enable the colorimetric unit 202 to read the colorimetric image with high accuracy. Furthermore, it is no longer necessary to provide a margin in the size of the colorimetric image to compensate for misalignment or tilt. This makes it possible to form multiple colorimetric images on paper, thereby saving paper and shortening adjustment time.

[0061] In this embodiment, the image forming apparatus 100 and the image reading apparatus 200 are described as separate devices, but they may also be configured as an integrated unit. For example, the image reading unit 201 may be provided downstream of the position of the cooling fan 120 of the image forming apparatus 100 in the paper transport direction, and the colorimetric unit 202 may be provided on one of the transport paths branching off further downstream. Paper transported to the transport path on which the colorimetric unit 202 is provided is discharged to an escape tray 203, and paper transported to the other branched transport path is transported to the finisher 300.

Claims

1. a color measurement unit that reads a detection image including a color measurement image printed on a sheet and a position measurement image for detecting the state of the color measurement image; a moving means for moving the color measurement means in a first direction; a conveying means for conveying the paper in a second direction perpendicular to the first direction; a control means for detecting a state of the color measurement image based on a result of reading the image for position measurement by the color measurement means, and for causing the color measurement means to read the image for color measurement while controlling the movement of the color measurement means by the moving means and the transport of the paper by the transport means based on the detected state of the image for color measurement, the control means detects an amount of tilt of the color measurement image and an amount of deviation of the color measurement image in the first direction based on the reading result of the position measurement image, and controls the movement of the color measurement means by the moving means and the transport of the paper by the transport means based on the detected amount of tilt and amount of deviation. Image reading device.

2. the control means calculates the amount of movement of the color measurement means in the first direction and the amount of paper feed when reading the color measurement image based on the amount of tilt and the amount of deviation, and causes the color measurement means to perform a reading operation every time the moving means moves the color measurement means by the amount of movement.

2. The image reading device according to claim 1.

3. a predetermined number of the color measurement images are printed in the first direction and a predetermined number of lines are printed in the second direction, the control means, when reading the colorimetry image of the first row in the second direction, causes the conveying means to feed the paper by an amount obtained by adding the paper feed amount and the deviation amount.

3. The image reading device according to claim 2.

4. the control means temporarily suspends the movement of the colorimetric means by the moving means and the reading operation by the colorimetric means when the reading position of the colorimetric means deviates from the range of the colorimetric image in the second direction. The image reading device according to any one of claims 1 to 3.

5. An image reading device according to any one of claims 1 to 4; an image forming means for forming an image on a sheet based on image forming conditions, the image forming means forms the detection image including the color measurement image and the position measurement image on the paper. Image forming device.

6. The image forming unit corrects the image forming conditions based on the result of reading the color measurement image by the image reading device. The image forming apparatus according to claim 5 .

7. the image forming means acquires an amount of tilt of the color-measurement image from the image reading device, and corrects a printing position of the detection image formed on the paper based on the acquired amount of tilt.

7. The image forming apparatus according to claim 5 or 6.

Images