Image forming system, method for controlling image forming system, and program

Abstract

To provide an image forming system that can reduce a processing time of the entire system, a method for controlling the image forming system, and a program.SOLUTION: An image forming system 1 comprises an image forming unit 24, a reading unit 32, a color measuring unit 34, and a control unit. The image forming unit 24 forms an image on a recording medium. The reading unit 32 reads the image formed on the recording medium. The color measuring unit 34 is arranged on the downstream side of the reading unit 32 in a conveyance direction of the recording medium, and measures the colors of a color adjustment chart formed on the recording medium. The control unit controls the color measuring unit on the basis of image information read by the reading unit 32.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming system, a control method for an image forming system, and a program. [Background technology]

[0002] An image forming system includes an image forming apparatus that forms an image on paper and a paper supplying apparatus that supplies paper to the image forming apparatus. The image forming apparatus then forms the image on the paper based on output job information. In recent years, printing accuracy has been improved by measuring the color information of the printed matter using a colorimetric unit and correcting the image formation operation of the image forming unit based on the colorimetric information.

[0003] A conventional technology relating to this type of colorimetric unit is, for example, described in Patent Document 1. Patent Document 1 describes a technology that includes an acquisition unit that measures the color of a color patch and acquires at least two colorimetric values, and a first determination unit that determines whether or not the measured color patch is one that should be colorimetrically measured based on the at least two colorimetric values.

[0004] Furthermore, by increasing the number of color patches in the color adjustment chart, it is possible to perform color correction with high precision. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-152551 Summary of the Invention [Problem to be solved by the invention]

[0006] However, as the number of color patches in the color adjustment chart increases, the color measurement operation in the colorimetric unit takes a long time. Furthermore, with the technology described in Patent Document 1, in order to determine whether the color measurement result is an error, it is necessary to operate the colorimetric unit and actually measure the color patches of the color adjustment chart. As a result, with the technology described in Patent Document 1, it is necessary to operate the colorimetric unit even if the color measurement result is an error, which poses a problem of long processing times for the entire system.

[0007] SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, an object of the present invention is to provide an image forming system, a control method for an image forming system, and a program that can reduce the processing time of the entire system. [Means for solving the problem]

[0008] In order to solve the above problems and achieve the object of the present invention, the image forming system of the present invention includes an image forming unit, a reading unit, a colorimetric unit, and a control unit. The image forming unit forms an image on a recording medium. The reading unit reads the image formed on the recording medium. The colorimetric unit is disposed downstream of the reading unit in the recording medium transport direction and measures the color of a color adjustment chart formed on the recording medium. The control unit controls the colorimetric unit based on the image information read by the reading unit.

[0009] The control method for an image forming system of the present invention includes the following processes (1) to (3). (1) A process for forming a color adjustment chart on a recording medium. (2) A process of reading an image formed on a recording medium by a reading unit. (3) A process of controlling a colorimetric unit that is arranged downstream of the reading unit in the conveyance direction of the recording medium and that measures the color of a color adjustment chart formed on the recording medium, based on the image information read by the reading unit.

[0010] The program of the present invention is a program for causing an image forming system to execute the following procedures (1) to (3). (1) A procedure for forming a color adjustment chart on a recording medium by an image forming unit. (2) A procedure for reading an image formed on a recording medium by a reading unit. (3) A procedure for controlling a colorimetric unit that is arranged downstream of the reading unit in the conveyance direction of the recording medium and measures the color of a color adjustment chart formed on the recording medium, based on image information read by the reading unit. [Effects of the Invention]

[0011] According to the image forming system, the control method for the image forming system, and the program having the above-described configuration, the processing time of the entire system can be reduced. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing the overall configuration of an image forming system according to an embodiment of the present invention; [Figure 2] 1 is a block diagram showing a hardware configuration of an image forming system according to an embodiment of the present invention; [Figure 3] 5A and 5B are explanatory diagrams illustrating a color measurement operation of a color measurement unit according to an embodiment of the present invention. [Figure 4] 5 is a flowchart showing a color measurement operation of the image forming system according to the embodiment of the present invention. [Figure 5] 10 is a flowchart showing a patch measurement process of an image forming system according to an embodiment of the present invention. [Figure 6] 6A and 6B are diagrams showing an example of an image formed on paper when the patch size is smaller than a predetermined size or in high-precision colorimetry mode in an image forming system according to an embodiment of the present invention, where FIG. 6A shows the ideal printing position, and FIG. 6B shows an image when printing misalignment occurs. [Figure 7] 10A and 10B are explanatory diagrams showing a method for calculating feature points in the image forming system according to the embodiment of the present invention; [Figure 8] 10 is a diagram showing the coordinates of the four corners of a color adjustment chart in the image forming system according to the embodiment of the present invention; [Figure 9] 10A and 10B are diagrams showing an example of an image formed on a sheet in a mode other than the high-precision color measurement mode, or in which the patch size is larger than a predetermined size, in the image forming system according to the embodiment of the present invention; [Figure 10] 10A and 10B are explanatory diagrams showing modified examples of characteristic points in the image forming system according to the embodiment of the present invention, where Fig. 10A shows an ideal print position, and Fig. 10B shows an image when print misalignment occurs. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the image forming system of the present invention will be described with reference to Figures 1 to 10B. Note that common members in each figure are given the same reference numerals. Furthermore, the present invention is not limited to the following embodiments.

[0014] 1. Example of implementation 1-1. Image formation system configuration First, the overall configuration of an image forming system according to an embodiment of the present invention (hereinafter referred to as "this example") will be described. Fig. 1 is a schematic diagram of an image forming system 1 according to this example.

[0015] 1, the image forming system 1 includes a paper feeder 10, an image forming device 20, and an image reading device 30. The paper feeder 10, the image forming device, and the image reading device 30 are each connected to a network such as a LAN, and are interconnected via the network. In the image forming system 1, the paper feeder 10, the image forming device 20, and the image reading device 30 are arranged in this order from the upstream side of the transport path of the paper S, and are connected in series.

[0016] The paper feeding device 10 has a paper feeding section 13 consisting of a plurality of paper feeding trays 131, 132, and 133, and a transport section 12 (see FIG. 2) that transports the paper stored in the paper feeding section 13. The number of paper feeding trays 131, 132, and 133 that make up the paper feeding section 13 is not limited to three, and two or four or more may be provided. The transport section 12 has a transport path 121 that communicates with the image forming device 20. The transport section 12 transports the paper to the image forming device 20 via the transport path 121.

[0017] The image forming device 20 forms an image on roll paper S by electrophotography, and is a tandem color image forming device that overlays toner of four colors: yellow (Y), magenta (M), cyan (C), and black (K). The image forming device 20 includes an operation unit 21, a display unit 22, a document reading unit 23, and an image forming unit 24.

[0018] The operation unit 21 and the display unit 22 are installed on the upper part of the housing of the image forming apparatus 20. The operation unit 21 and the display unit 22 are, for example, touch panels made up of displays such as a liquid crystal display (LCD) or an organic ELD (Electro Luminescence Display). The display unit 22 displays instruction menus for the user, information on the acquired image data, etc. Furthermore, the operation unit 21 has a plurality of keys, and accepts input of various instructions, characters, numbers, and other data by the user's key operation, and outputs input signals to the control unit 26. The display unit 22 also displays various reports showing the inspection results of the image reading device 30, which will be described later, feedback information, etc.

[0019] The document reading unit 23 has a document feed tray on which documents are set, a document discharge tray, multiple rollers, and a document reading section. The documents set on the document feed tray are transported one by one by the multiple rollers to the reading position of the document reading section. The documents read by the document reading section are discharged to the document discharge tray.

[0020] The document reading unit reads the image of the document that has been conveyed or that has been placed on the document feed table, and generates image data. The document that has been conveyed to the document reading unit has one or both sides of the image exposed by an optical system and then read by an image sensor.

[0021] The analog signal photoelectrically converted by the image sensor undergoes various processes in the image processing unit, such as analog processing, A / D conversion processing, shading ink correction processing, image compression processing, etc. The image signal that has undergone various signal processes is then sent from the image processing unit 29 (see FIG. 2) to the image forming unit 24.

[0022] In addition, the image signal sent to the image forming unit 24 is not limited to the image signal output from the document reading unit 23, but may also be received from an external device such as a personal computer connected to the image forming device 20 or another image forming device.

[0023] The image forming section 24 has four image forming units 241Y, 241M, 241C, and 241K, a conveying section 246, an intermediate transfer belt 242, a secondary transfer section 243, a fixing section 244, and a reverse conveying section 245. The image forming section 24 forms toner images of the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) using the four image forming units 241Y, 241M, 241C, and 241K.

[0024] The first image forming unit 241Y forms a yellow toner image, the second image forming unit 241M forms a magenta toner image, the third image forming unit 241C forms a cyan toner image, and the fourth image forming unit 241K forms a black toner image. Because these four image forming units 241Y, 241M, 241C, and 241K each have the same configuration, only the first image forming unit 241Y will be described here.

[0025] The first image forming unit 241Y has a drum-shaped photosensitive member, a charging unit arranged around the photosensitive member, an exposure unit, a developing unit, and a cleaning device. The photosensitive member is rotated counterclockwise by a drive motor (not shown). The charging unit applies an electric charge to the photosensitive member, uniformly charging the surface of the photosensitive member. The exposure unit performs exposure scanning on the surface of the photosensitive member based on image data transmitted from an external device, forming an electrostatic latent image on the photosensitive member.

[0026] The developing unit applies yellow toner to the electrostatic latent image formed on the photoconductor. As a result, a yellow toner image is formed on the surface of the photoconductor. The developing unit of the second image forming unit 241M applies magenta toner to the photoconductor, and the developing unit of the third image forming unit 241C applies cyan toner to the photoconductor. Finally, the developing unit of the fourth image forming unit 241K applies black toner to the photoconductor.

[0027] The toner adhering to the photosensitive member is transferred to the intermediate transfer belt 242. After the toner has been transferred to the intermediate transfer belt 242, the cleaning device removes the toner remaining on the surface of the photosensitive member.

[0028] Intermediate transfer belt 242 is formed endless and rotates clockwise, which is the opposite direction to the rotation of the photosensitive members, by a drive motor (not shown). A primary transfer unit is provided on intermediate transfer belt 242 at a position facing the photosensitive members of each image forming unit 241Y, 241M, 241C, and 241K. This primary transfer unit applies a polarity opposite to that of the toner to intermediate transfer belt 242, thereby transferring the toner image formed on the photosensitive member to intermediate transfer belt 242.

[0029] As the intermediate transfer belt 242 rotates, the toner images formed by the four image forming units 241Y, 241M, 241C, and 241K are sequentially transferred onto the surface of the intermediate transfer belt 242. As a result, the yellow, magenta, cyan, and black toner images are superimposed on each other to form a color image on the intermediate transfer belt 242.

[0030] A secondary transfer unit 243 is disposed near the intermediate transfer belt 242 and downstream in the conveying direction of the conveying unit 246. The secondary transfer unit 243 is configured with a pair of transfer rollers, including an upper transfer roller around which the intermediate transfer belt 242 is stretched, and a lower transfer roller pressed against the upper transfer roller with the intermediate transfer belt 242 sandwiched therebetween. The upper transfer roller and lower transfer roller that constitute the secondary transfer unit 243 are configured to be able to press against and separate from each other with the intermediate transfer belt 242 sandwiched therebetween.

[0031] In the secondary transfer unit 243, the paper conveyed from the conveyance unit 246 is pressed by a lower transfer roller toward the intermediate transfer belt 242. Then, the secondary transfer unit 243 transfers the color toner image formed on the intermediate transfer belt 242 onto the paper sent from the conveyance unit 246.

[0032] Furthermore, a fixing unit 244 is provided downstream in the transport direction of the secondary transfer unit 243. The fixing unit 244 includes a fixing belt and a pressure roller as a pressure member. The fixing belt is made of an endless elastic member, and is supported and stretched between a fixing roller as a drive roller and a heating roller as a driven roller.

[0033] A fixing nip is formed where the fixing roller and pressure roller come into contact with each other via the fixing belt. When a sheet of paper carrying a toner image passes through the fixing nip of fixing unit 244, the toner is melted by the fixing belt and pressure roller, which are controlled to a predetermined temperature, and fixed to the sheet of paper.

[0034] The sheet on which the fixing process has been performed by the fixing unit 244 is conveyed by the conveying unit 246 to the reverse conveying unit 245 and the image reading device 30.

[0035] The reverse conveyance section 245 is provided with a reversing section that reverses the paper. The paper that has been reversed by the reversing section is conveyed through the reverse conveyance section 245 to the upstream side of the secondary transfer section 243 or the downstream side of the fixing section 244.

[0036] The image reading device 30 is a device that reads an image formed on a sheet of paper. The image reading device 30 is also a device that performs color measurement of a correction patch formed on the sheet of paper. The image reading device 30 has a conveying unit 36 ​​(see FIG. 2) that conveys the sheet of paper, a reading unit 32, a detection unit 33, a color measurement unit 34, a correction unit 35, and a paper discharge tray 39. The conveying unit 36 ​​has a first conveying unit 37 and a second conveying unit 38.

[0037] The reading unit 32 is disposed on the upstream side of the image reading device 30 in the transport direction. The reading unit 32 reads an image formed on a sheet transported from the image forming device 20. The downstream side of the reading unit 32 in the transport direction branches into a first transport unit 37 and a second transport unit 38. The first transport unit 37 transports the sheet toward a paper output tray 39.

[0038] The second conveying section 38 is provided with a correction section 35, a detection section 33, and a color measurement section 34. The correction section 35 has a first conveying roller 351 and a second conveying roller 352. The correction section 35 corrects the orientation of the paper conveyed by the first conveying roller 351 and the second conveying roller 352.

[0039] A detection unit 33 is disposed downstream of the correction unit 35 in the second conveying unit 38 in the conveying direction. The detection unit 33 detects paper that has passed through the second conveying unit 38 and reached the detection unit 33. A colorimetric unit 34 is disposed downstream of the detection unit 33 in the conveying direction. The colorimetric unit 34 measures the color of patches formed on the paper that has passed the detection unit 33. The paper that has passed the colorimetric unit 34 is conveyed to a paper output tray 39 by the second conveying unit 38.

[0040] 1-2. Hardware configuration of each device Next, the hardware configuration of each device will be described with reference to FIG. FIG. 2 is a block diagram showing the hardware configuration of each device in the image forming system.

[0041] First, the hardware configuration of the paper feeder 10 will be described. 2, the sheet feeding device 10 includes a control unit 11, a sheet feeding unit 13, and a conveying unit 12. The control unit 11 has, for example, a CPU (Central Processing Unit). The control unit 11 controls the sheet feeding unit 13 and the conveying unit 12, and feeds sheets of a predetermined size from sheets stored in sheet feeding trays 131, 132, and 133 toward the image forming device 20.

[0042] Next, the hardware configuration of the image forming apparatus 20 will be described. The image forming apparatus 20 includes an operation unit 21, a display unit 22, a document reading unit 23, a control unit 26, a storage unit 27, a communication unit 28, and an image processing unit 29. The control unit 26 has, for example, a CPU (Central Processing Unit). The control unit 26 is connected to the operation unit 21, the display unit 22, the document reading unit 23, the storage unit 27, the communication unit 28, and the image processing unit 29 via a system bus, and controls the entire image forming apparatus 20. The control unit 26 also corrects the image forming operation in the image forming unit 24 based on the reading result of the image reading device 30, which will be described later.

[0043] The storage unit 27 is a volatile memory such as a RAM or a large-capacity non-volatile memory. The storage unit 27 stores programs executed by the control unit 26 and is also used as a work area for the control unit 26.

[0044] The image processing unit 29 acquires image data and attribute data from job information input from outside and performs image processing. Under the control of the control unit 26, the image processing unit 29 performs image processing such as shading correction, image density adjustment, and image compression on the received image data in accordance with the attribute data and job information. The image data processed by the image processing unit 29 is then sent to the image forming unit 24. The image forming unit 24 receives the image data processed by the image processing unit 29 and forms an image on paper based on the image data.

[0045] The communication unit transmits and receives data to and from the paper feed device 10, the image reading device 30, etc. The communication unit outputs various data such as the received image data and attribute data to the control unit .

[0046] Next, the hardware configuration of the image reading device 30 will be described. The image reading device 30 includes a control unit 31, a reading unit 32, a detection unit 33, a colorimetric unit 34, a correction unit 35, and a conveying unit 36. The control unit 31 has, for example, a CPU (Central Processing Unit). The control unit 31 is connected to the reading unit 32, the detection unit 33, the colorimetric unit 34, the correction unit 35, and the conveying unit 36 ​​via a system bus, and controls the entire image reading device 30.

[0047] The reading unit 32 reads (captures) an image formed on a sheet of paper transported from the image forming device 20. The reading unit 32 outputs the read image information to the control unit 31. The control unit 31 controls the operations of the colorimetric unit 34, the correction unit 35, and the transport unit 36 ​​based on the image information received from the reading unit 32. The transport unit 36 ​​switches between transporting the sheet of paper to the first transport unit 37 or the second transport unit 38 based on a control signal from the control unit 31.

[0048] The color measurement unit 34 performs color measurement of the patches formed on the paper based on a control signal from the control unit 31. Then, the color measurement unit 34 outputs the color measurement result to the control unit 31.

[0049] In the image forming system 1 of this example, the sheet feeder 10, the image forming device 20, and the image reading device 30 are provided with the control units 11, 26, and 31, respectively, but the present invention is not limited to this. For example, a single control unit that controls the entire image forming system 1 may be provided.

[0050] 2. Color measurement operation of the colorimeter Next, the color measurement operation of the color measurement unit 34 will be described with reference to FIG. FIG. 3 is an explanatory diagram showing the color measurement operation of the color measurement unit 34.

[0051] 3, when performing color measurement operation in the color measurement unit 34, the control unit 26 of the image forming apparatus 20 controls the image forming unit 24 to form a color adjustment chart P1 consisting of multiple colors (patches) on the paper S1. The multiple color patches that make up the color adjustment chart P1 are printed and arranged along the scanning direction perpendicular to the transport direction of the paper S1 and along the transport direction.

[0052] When the paper S1 reaches the colorimetry unit 34, the control unit 31 of the image reading device 30 moves the detection unit of the colorimetry unit 34 in the scanning direction. Therefore, as shown in Fig. 3, the detection point Q1 of the colorimetry unit 34 moves along the scanning direction and measures the color of the color adjustment chart P1 formed on the paper S1 and consisting of multiple colors.

[0053] Here, if the color adjustment chart P1 is formed on the paper S1 at an angle, the direction in which the patches of the color adjustment chart P1 are arranged will also be tilted relative to the scanning direction of the colorimetric unit 34. As a result, the detection point Q1 of the colorimetric unit 34 may pass over a patch different from the patch that is the intended target of color measurement, or may pass over the boundary between patches of two different colors. As a result, there is a problem in that the colorimetric accuracy of the colorimetric unit 34 may decrease, or colorimetric errors may occur.

[0054] In the image forming system 1 of this embodiment, the detection unit of the colorimetric unit 34 is moved in a scanning direction perpendicular to the transport direction of the paper S1. However, the direction in which the detection unit moves is not limited to this. For example, the detection unit of the colorimetric unit 34 may be moved in two directions: the scanning direction and the sub-scanning direction perpendicular to the scanning direction, or may be moved only in the sub-scanning direction. Furthermore, the detection unit of the colorimetric unit 34 may be fixed. Note that by moving the detection unit of the colorimetric unit 34 in the scanning direction or the sub-scanning direction, multiple colors can be measured at once. As a result, it is possible to form a large amount of color information (patches) on a single sheet of paper S1, and a large amount of color measurement data can be obtained with a small number of sheets of paper, enabling highly accurate color correction.

[0055] Furthermore, as the number of patches to be measured increases, the color measurement takes a long time. Therefore, in order to shorten the time required for color measurement, it is preferable to reduce the size of the patches formed on one sheet of paper S1. Furthermore, if the patch size is reduced, and the position of the color adjustment chart P1 becomes tilted, as described above, there is a risk that the color measurement accuracy will decrease or a color measurement error will occur.

[0056] 3. Color measurement operation of the image forming system Next, the color measurement operation of the image forming system 1 having the above-described configuration will be described with reference to FIGS. FIG. 4 is a flowchart showing the color measurement operation, and FIG. 5 is a flowchart showing the patch measurement process.

[0057] 4, the control unit 26 of the image forming apparatus 20 executes a color measurement operation for a color adjustment print chart in response to a user instruction or at predetermined intervals (step S11). Next, the control unit 26 determines the color measurement mode (step S12). In the processing of step S12, the control unit 26 determines whether the patch size printed on the color adjustment print chart is smaller than a predetermined size or whether the color measurement mode is a high-precision color measurement mode (step S12).

[0058] In the process of step S12, if control unit 26 determines that the patch size is smaller than the predetermined size or that the high-precision color measurement mode is being used (YES in step S12), the process proceeds to step S13. In the process of step S13, control unit 26 of image forming device 20 controls image forming unit 24 to print the register marks as a rectangular shape as the predetermined first measurement image. Then, the process proceeds to step S15.

[0059] 6A and 6B are diagrams showing an example of an image formed on paper S1 when the patch size is smaller than a predetermined size or in high-precision color measurement mode (second level). Fig. 6A shows the ideal printing position, and Fig. 6B shows an image when printing misalignment occurs. As shown in Figure 6A, when the patch size is smaller than a predetermined size or in high-precision color measurement mode, a color adjustment chart P1 and first registration marks T1 are printed on the paper S1. The first registration marks T1 are printed at the four corners of the paper S1. The first registration marks T1 are printed as rectangular black images. The first registration marks T1 and color adjustment chart P1 are formed at predetermined positions on the paper S1.

[0060] As shown in FIG. 6B, when printing misalignment occurs and the color adjustment chart P1 is tilted from the ideal printing position, the printing position of the first register mark T1 also tilts from the ideal printing position by the same amount as the misalignment of the color adjustment chart P1.

[0061] The shape of the first registration mark T1 is not limited to a rectangle, but various other shapes such as a triangle or a hexagon can be used. Also, although the first registration mark T1 is painted black, it is not limited to this and may be painted white or various other colors. Also, in order to be readable by the reading unit 32, it is preferable that the first registration mark T1 has a predetermined density difference from the paper S1.

[0062] If control unit 26 determines that the patch size is larger than the predetermined size or that the high-precision color measurement mode is not selected (NO in step S12), the process proceeds to step S14. In step S14, control unit 26 of image forming device 20 controls image forming unit 24 to print cross marks as the predetermined second measurement image. Then, the process proceeds to step S17.

[0063] FIG. 9 is a diagram showing an example of an image formed on a sheet S1 in a mode (first level) where the patch size is larger than a predetermined size or is not the high-precision color measurement mode. As shown in Figure 9, when the patch size is larger than a predetermined size or in a mode other than the high-precision color measurement mode, a color adjustment chart P1 and second registration marks T2 are printed on the paper S1. The second registration marks T2 are printed at the four corners of the paper S1, just like the first registration marks T1. The second registration marks T2 are printed as cross images. The second registration marks T2 and color adjustment chart P1 are formed at predetermined positions on the paper S1.

[0064] Although the example has been described in which the second registration marks T2 are formed on the paper S1 at the first level, which is a mode in which the patch size is larger than a predetermined size or is not a high-precision color measurement mode, the present invention is not limited to this. At the first level, the second registration marks T2 do not have to be formed on the paper S1.

[0065] In the processing of step S15, the control unit 26 of the image forming device 20 and the control unit 31 of the image reading device 30 perform a patch measurement process. In the processing of step S15, the position and size of the color adjustment chart P1 are measured by measuring the position and size of the first register mark T1. Details of the processing of step S15 will be described later.

[0066] When the process of step S15 is completed, the control unit 31 of the image reading device 30 determines whether the return value is an error (step S16). If the control unit 31 determines in the process of step S16 that the return value is an error (YES determination in step S16), the control unit 31 does not perform the color measurement operation by the color measurement unit 34. In other words, the control of the color measurement unit 34 by the control unit 31 of the image forming system 1 of this example also includes control not to perform the color measurement operation. Then, the process proceeds to step S18.

[0067] Specifically, the control unit 31 controls the conveying unit 36 ​​to convey the sheet S1 to the first conveying unit 37. Therefore, the sheet S1 is discharged to the sheet output tray 39 without passing through the colorimetry unit 34. Alternatively, the control unit 31 controls the conveying unit 36 ​​to convey the sheet S1 to the second conveying unit 38, but does not operate the colorimetry unit 34. Therefore, the sheet S1 is discharged to the sheet output tray 39 without being subjected to colorimetry by the colorimetry unit 34.

[0068] In this way, errors can be detected quickly by making an error determination before operating the colorimetric unit 34. Furthermore, by not operating the colorimetric unit 34 when an error is determined, it is possible to prevent time from being wasted by the colorimetric unit 34 and shorten the processing time.

[0069] Furthermore, in the process of step S16, if the control unit 31 determines that the return value is not an error (NO determination in step S16), it performs color measurement processing (step S17). In the process of step S17, the control unit 31 controls the conveying unit 36 ​​to convey the paper S1 to the second conveying unit 38. Then, the control unit 31 controls the detection unit 33 and the colorimetric unit 34 to measure the color of the color adjustment chart P1 printed on the paper S1. This completes the colorimetric operation of the image forming system 1.

[0070] Furthermore, in a mode where the patch size is larger than a predetermined size or where the mode is not the high-precision colorimetry mode, the colorimetry process is performed without performing the processes of steps S15 and S16. When the patch size is relatively large, even if the color adjustment chart P1 is slightly tilted, the detection point Q1 of the color section 34 passes over the patch that is the intended target of colorimetry. Therefore, in a mode where the patch size is larger than a predetermined size or where the mode is not the high-precision colorimetry mode, the processes of steps S15 and S16 are not performed, thereby shortening the processing time of the entire system.

[0071] On the other hand, when the patch size is smaller than a predetermined size or in high-precision color measurement mode, the printing misalignment and patch size of the color adjustment chart P1 are determined before performing color measurement operation by the colorimetric unit 34. This makes it possible to perform error determination before actually operating the colorimetric unit 34, thereby shortening the processing time of the entire system.

[0072] Furthermore, in the process of step S18, the control unit 26 of the image forming device 20 determines whether or not to perform position adjustment based on the information from the process of step S15 in the control unit 31 of the image reading device 30. If the control unit 26 determines in the process of step S18 that position adjustment is not to be performed (NO determination in step S18), the process is completed.

[0073] If the control unit 26 determines in the process of step S18 that position adjustment should be performed (YES determination in step S18), the process proceeds to step S19. In the process of step S19, the control unit 26 of the image forming apparatus 20 controls the image forming unit 24 based on the information from the process of step S15 by the control unit 31 of the image reading device 30. That is, the control unit 26 of the image forming apparatus 20 controls the image forming unit 24 based on the information from the control unit 31 of the image reading device 30, and adjusts the printing positions of the color adjustment chart P1 and the register marks T1 and T2. Then, when the process of step S19 ends, the process returns to the process of step S11, and the color measurement operation is performed again.

[0074] In the process of step S19, an example has been described in which image forming apparatus 20 adjusts the position based on information from control unit 31 of image reading device 30, but the present invention is not limited to this. For example, the information on the process of step S15 may be displayed on display unit 22, and the user may operate operation unit 21 to perform the position adjustment.

[0075] Next, the patch measurement process in step S15 will be described with reference to FIGS. 5, the control unit 26 of the image forming device 20 stores chart information to be printed in the storage unit 27 (step S21). Next, the control unit 26 controls the image forming unit 24 to print a color adjustment chart P1 and a first registration mark T1 on the paper S1 based on the chart information stored in step S21 (step S22). As a result, the color adjustment chart P1 and the first registration mark T1 are printed on the paper S1, as shown in FIGS. 6A and 6B. The paper S1 is then transported from the image forming device 20 to the image reading device 30.

[0076] When the paper S1 is conveyed to the image reading device 30, the control unit 31 of the image reading device 30 controls the reading unit 32 to capture an image of the color adjustment chart P1 and the first register marks T1 printed on the paper S1 (step S23). When the processing of step S23 is completed, the reading unit 32 outputs the captured image information to the control unit 31. Then, the control unit 31 calculates feature points of the color adjustment chart P1 and the first register marks T1 based on the image information (step S24).

[0077] FIG. 7 is an explanatory diagram showing a method for calculating feature points. 7, the control unit 31 detects two lines that bisect the area of ​​the rectangular first register mark T1 from the image information (for example, a diagonal line connecting the vertices TL1 and TR2, and a diagonal line connecting the vertices TL2 and TR1).Then, the control unit 31 calculates the center of gravity G of the first register mark T1 as a feature point from the intersection of the two diagonal lines.

[0078] For example, the control unit 31 first obtains the midpoint in the main scanning direction based on the image information of the first register mark T1. That is, the control unit 31 obtains the sum of the density distribution of a specific size in the main scanning direction, and calculates the midpoint in the main scanning direction from this sum data. Next, the control unit 31 obtains the midpoint in the sub-scanning direction, which is perpendicular to the main scanning direction, based on the image information of the first register mark T1. That is, the control unit 31 obtains the sum of the density distribution of a specific size in the sub-scanning direction, and calculates the midpoint in the sub-scanning direction from this sum data. Then, the control unit 31 calculates the intersection of the midpoint in the main scanning direction and the midpoint in the sub-scanning direction, using the center of gravity G of the first register mark T1 as a feature point.

[0079] 9, when calculating the intersection of a cross as a feature point, there is a risk that the calculation accuracy of the feature point will decrease due to toner spills, dirt, etc. Therefore, by calculating the center of gravity G of the rectangular first register mark T1 as the feature point, it is possible to reduce the influence of toner spills, dirt, etc. and improve the calculation accuracy.

[0080] Returning to FIG. 5, the control unit 31 determines whether the centers of gravity of the four first register marks T1, i.e., the four feature points, have been calculated (step S25). If the control unit 31 determines in the processing of step S25 that the four feature points have not been calculated (NO in step S25), an error notification is issued (step S33). That is, the return value of the patch measurement processing is also an error. Then, the control unit 31 proceeds to the processing of step S16 shown in FIG. 4.

[0081] Furthermore, in the process of step S25, if the control unit 31 determines that four feature points have been calculated (YES determination in step S25), the control unit 31 calculates a displacement amount coefficient from the four feature points (step S26). In the process of step S26, for example, a projective transformation coefficient is calculated as the displacement amount coefficient from the four feature points.

[0082] Next, the control unit 31 calculates the coordinates of the four corners of the color adjustment chart P1 based on the deviation amount coefficients calculated in the processing of step S26 (step S27). In the processing of steps S26 and S27, various calculation methods such as projective transformation, phase-only correlation, affine transformation, and the like can be applied.

[0083] FIG. 8 is a diagram showing the coordinates of the four corners of the color adjustment chart P1. By performing the processing of step S27, the coordinates (x, y) of the four corners LT, LB, RT, and RB of the color adjustment chart P1 can be obtained, as shown in FIG. 8. Next, the control unit 31 calculates the difference (distance) of the X and Y components from the coordinates (x, y) of the four corners LT, LB, RT, and RB of the color adjustment chart P1, i.e., the amount of deviation from the ideal position (step S28). That is, as the difference of the Y component, LT(y)-RT(y) and LB(y)-RB(y) of the four corners are calculated. Similarly, as the difference of the X component, LT(x)-LB(x) and RT(x)-RB(x) of the four corners are calculated.

[0084] Next, the control unit 31 determines whether the difference calculated in the process of step S28 is within the allowable error (step S29). If the control unit 31 determines in the process of step S29 that the difference exceeds the allowable error (NO in step S29), it issues an error notification (step S34). That is, the return value of the patch measurement process is also an error. Then, the control unit 31 proceeds to the process of step S16 shown in FIG. 4. The control unit 31 also outputs the amount of misalignment calculated in step S29 to the control unit 26 of the image forming apparatus 20. This makes it possible to automatically correct the printing misalignment in step S19.

[0085] In the process of step S29, if the control unit 31 determines that the difference is within the allowable error (YES in step S29), the control unit 31 calculates the magnification of the color adjustment chart P1, i.e., the patch size, from the size of the first register mark T1 based on the image information (step S30). Next, it determines whether the magnification calculated in the process of step S30 is equal to or greater than a predetermined magnification (step S31).

[0086] In the process of step S31, if the control unit 31 determines that the magnification is not equal to or greater than the predetermined magnification (NO determination in step S31), an error notification is issued (step S35). That is, the return value in the patch measurement process will also be an error. Then, the control unit 31 proceeds to the process of step S16 shown in FIG. 4. On the other hand, in the process of step S31, if the control unit 31 determines that the magnification is equal to or greater than the predetermined magnification (YES determination in step S31), the control unit 31 notifies that the color adjustment chart P1 is normal (step S32). Then, the process proceeds to the process of step S16 shown in FIG. 4. This completes the patch measurement process.

[0087] 4. Variation of feature points Next, a modified example of the feature point will be described with reference to FIGS. 10A and 10B. 10A and 10B are explanatory diagrams showing modified examples of feature points, where Fig. 10A shows the ideal print position, and Fig. 10B shows an image when print misalignment occurs.

[0088] In the above-described embodiment, the center of gravity of the rectangular first register mark T1 is used as the feature point, but this is not limiting. For example, as shown in FIG. 10A, the vertices T3 at the four corners of the color adjustment chart P1 printed on the paper S1 may be used as feature points. Also, as shown in FIG. 10B, even if printing misalignment occurs and the color adjustment chart P1 is tilted from the ideal printing position, the vertices T3 at the four corners of the color adjustment chart P1 will be tilted from the ideal printing position by the same amount as the amount of misalignment of the color adjustment chart P1. Even with such feature points, the amount of misalignment of the color adjustment chart P1 can be calculated in the same way as in the above-described embodiment.

[0089] The above describes the embodiments, including their effects. However, the present invention is not limited to the above embodiments, and various modifications are possible within the scope of the invention as defined in the claims.

[0090] Furthermore, although an example in which paper is used as the recording medium has been described, the present invention is not limited to this, and various other materials such as film and fabric can also be used as the recording medium.

[0091] Furthermore, some or all of the above-described components, functions, processing units, etc. may be implemented in hardware, for example, by designing an integrated circuit. Furthermore, the above-described components, functions, etc. may be implemented in software by a processor interpreting and executing a program that implements each function. Information such as the programs, tables, and files that implement each function can be stored in a storage device such as a memory, a hard disk, or an SSD (Solid State Drive), or in a storage medium such as an IC card, SD card, or DVD.

[0092] In this specification, the words "parallel" and "orthogonal" are used, but these do not mean only "parallel" and "orthogonal" in the strict sense, but also include "parallel" and "orthogonal" and may also mean a "substantially parallel" or "substantially orthogonal" state within a range in which the functions can be exerted. [Explanation of symbols]

[0093] 1...image forming system, 10...paper feeding device, 11...control unit, 12...transport unit, 13...paper feeding unit, 20...image forming device, 21...operation unit, 22...display unit, 23...document reading unit, 24...image forming unit, 26...control unit, 27...storage unit, 28...communication unit, 29...image processing unit, 30...image reading device, 31...control unit, 32...reading unit, 33...detection unit, 34...colorimetry unit, 35...correction unit, 36...transport unit, 37...first transport unit, 38...second transport unit, 39...paper output tray, P1...color adjustment chart, G...center of gravity (feature point), T1...first registration mark, T2...second registration mark, T3...vertex (feature point)

Claims

1. an image forming unit that forms an image on a recording medium; a reading unit that reads an image formed on the recording medium; a color measurement unit that is disposed downstream of the reading unit in a conveyance direction of the recording medium and that measures the color of a color adjustment chart formed on the recording medium; a control unit that controls the colorimetric unit based on image information read by the reading unit; An image forming system comprising:

2. The control unit Calculating feature points from the image information read by the reading unit; The color measurement unit is controlled based on the feature points. The image forming system according to claim 1 .

3. The control unit determines whether or not to perform color measurement of the color adjustment chart by the color measurement unit based on the feature points. The image forming system according to claim 2 .

4. The feature points are calculated from a predetermined measurement image formed on the recording medium. The image forming system according to claim 3 .

5. The feature point is the center of gravity of the predetermined measurement image. The image forming system according to claim 4 .

6. When the control unit determines that the patch size of the color adjustment chart is smaller than a predetermined size, the control unit controls the image forming unit to form the feature points on the recording medium. The image forming system according to claim 2 .

7. the control unit has a first level and a second level having higher accuracy than the first level as a color measurement mode, When the control unit determines that the color measurement mode is at the second level, the control unit controls the image forming unit to form the feature points on the recording medium. The image forming system according to claim 2 .

8. The control unit calculates a deviation amount from an ideal position on the color adjustment chart from the calculated characteristic point, and determines whether or not to perform color measurement of the color adjustment chart by the color measurement unit based on the calculated deviation amount. The image forming system according to claim 2 .

9. The control unit controls the image forming unit based on the calculated amount of deviation, and adjusts the printing position of the color adjustment chart. The image forming system according to claim 8 .

10. The control unit calculates a patch size of a color adjustment chart from the image information read by the reading unit, and controls the colorimetric unit based on the calculated patch size. The image forming system according to claim 1 .

11. The predetermined measurement image is a rectangular image formed at the four corners of the recording medium. The image forming system according to claim 4 .

12. A process of forming a color adjustment chart on a recording medium; a process of reading the image formed on the recording medium by a reading unit; a process of controlling a colorimetric unit that is disposed downstream of the reading unit in the conveyance direction of the recording medium and that measures the color of the color adjustment chart formed on the recording medium, based on the image information read by the reading unit; A control method for an image forming system including:

13. a step of forming a color adjustment chart on a recording medium by an image forming unit; a step of reading an image formed on the recording medium by a reading unit; a step of controlling a colorimetric unit that is disposed downstream of the reading unit in a conveyance direction of the recording medium and that measures the color of the color adjustment chart formed on the recording medium, based on image information read by the reading unit; A program executed by the image forming system.

Images