Image formation device, control method of image formation device, and program

Abstract

To provide an image formation device which dissolves such a problem that density unevenness caused by variation in the discharge amount of ink in a printed matter as a measurement object cannot be discriminated from density change caused by cockling, and can determine the cockling with high accuracy.SOLUTION: An image formation device includes read-out means for reading out a sheet printed with a chart image composed of a first recording pattern using ink of a first color and a second recording pattern which uses ink of a second color different from the first color, includes at least a part of the first recording pattern and has predetermined concentration, and detection means for detecting deformation of the sheet on the basis of a difference between a moisture content of a part corresponding to a region where the chart image is printed in the read-out image obtained by the read-out means and a moisture content of a part corresponding to a non-print region, in the region of the sheet, and thereby can determine cockling with high accuracy.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present disclosure relates to a technique for detecting deformation of paper. [Background technology]

[0002] When an inkjet printer prints an image on paper using water-based ink, the moisture in the ink can cause the paper to deform, damaging the quality of the print. One type of paper deformation is the phenomenon in which the paper ripples. Cockling occurs when two areas of the paper with large differences in moisture content are close to each other, and is caused by the difference in the amount of paper stretch in those areas.

[0003] Patent Document 1 discloses a method for detecting cockling using a density sensor installed in a printer. The method disclosed in Patent Document 1 detects cockling by utilizing the change in the amount of light received by the density sensor when the distance between the paper and the density sensor changes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-119713 A Summary of the Invention [Problem to be solved by the invention]

[0005] The technology disclosed in Patent Document 1 had a problem in that when the print to be measured itself had density unevenness caused by variations in the amount of ink ejected, the density unevenness could not be distinguished from density changes caused by cockling. In other words, there was a risk that a change in the amount of light received by the density sensor due to density unevenness would be erroneously determined to be cockling.

[0006] The present disclosure has been made to solve the above-mentioned problems, and has an object to determine cockling with high accuracy. [Means for solving the problem]

[0007] The image forming device according to the present disclosure is an image forming device that forms an image on paper using inks of multiple colors, and is characterized by comprising: a reading means that reads paper on which a chart image is printed, the chart image consisting of a first recording pattern using ink of a first color and a second recording pattern using ink of a second color different from the first color and having a predetermined density that encompasses at least a portion of the first recording pattern; and a detection means that detects deformation of the paper based on the difference in moisture content between a portion of the paper that corresponds to the area where the chart image is printed and a portion of the paper that corresponds to a non-printed area in the read image obtained by the reading means. Effect of the Invention

[0008] According to the present disclosure, it becomes possible to judge cockling with high accuracy. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram showing a hardware configuration of the image forming system. [Diagram 2] 3A to 3D are schematic diagrams showing an image forming unit 107. [Diagram 3] FIG. 2 is a diagram showing the arrangement of an image processing unit 106 according to the first embodiment. [Figure 4] 11 is a flowchart showing a process for printing a user image. [Diagram 5] 5 is a flowchart showing a process of determining a color separation table according to the first embodiment. [Figure 6] FIG. 4 is a diagram showing an example of a determination image in the first embodiment. [Figure 7] 6 is a flowchart showing a process for determining whether or not a sheet deformation has occurred in the first embodiment. [Figure 8] 13A to 13G are diagrams showing modified examples of the determination image. [Figure 9] FIG. 11 is a diagram showing the arrangement of an image processing unit 106 according to the second embodiment. [Figure 10]10 is a flowchart showing a primer amount determination process in the second embodiment. [Figure 11] FIG. 13 is a diagram showing an example of a determination image in the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that the following embodiments do not limit the present disclosure, and not all of the combinations of features described in the embodiments are necessarily essential to the solutions of the present disclosure. Note that the same configurations are described with the same reference numerals. Also, each process (step) in the flow chart is indicated with a reference numeral beginning with "S".

[0011] [Embodiment 1] <Hardware configuration of image forming system> 1 is a diagram showing a hardware configuration of an image forming system according to this embodiment. The image forming system according to this embodiment includes a CPU 100, a RAM 101, a ROM 102, an operation unit 103, a display unit 104, an external storage device 105, an image processing unit 106, an image forming unit 107, an image reading unit 108, an I / F unit 109 (interface unit), and a bus 110.

[0012] A CPU (Central Processing Unit) 100 controls the operation of the entire image forming system using input data and computer programs stored in RAM and ROM, which will be described later. Here, a case where the CPU 100 controls the entire image forming system will be described as an example, but the entire image forming system may be controlled by multiple hardware devices sharing the processing.

[0013] A RAM (Random Access Memory) 101 has a storage area for temporarily storing computer programs and data read from an external storage device 105, and data received from the outside via an I / F unit 109. The RAM 101 is also used as a storage area used when the CPU 100 executes various processes and as a storage area used when the image processing unit 106 executes image processing.

[0014] A ROM (Read Only Memory) 102 has a storage area for storing setting parameters for setting each unit in the image forming system, a boot program, and the like.

[0015] The operation unit 103 is an input device such as a keyboard and a mouse, and receives operations (instructions) from an operator. This allows the operator to input various instructions to the CPU 100.

[0016] The display unit 104 is a display device such as a liquid crystal screen, and can display the results of processing by the CPU 100 as images, characters, etc. If the display unit 104 is a touch panel capable of detecting a touch operation, the display unit 104 may function as a part of the operation unit 103.

[0017] The external storage device 105 is a large-capacity information storage device, typified by a hard disk drive. The external storage device 105 stores computer programs and data for causing the OS (operating system) and CPU 100 to execute various processes. The external storage device 105 also holds temporary data generated by the processing of each unit (for example, input / output image data and a threshold matrix used in the image processing unit 106). The computer programs and data stored in the external storage device 105 are read as appropriate under the control of the CPU 100, stored in the RAM 101, and processed by the CPU 100.

[0018] The image processing unit 106 is realized as a processor capable of executing a computer program or a dedicated image processing circuit, and executes various types of image processing for converting image data input as a print target into image data that can be output by an image forming apparatus described below. Note that instead of providing a dedicated processor as the image processing unit 106, the CPU 100 can also be configured to perform various types of image processing as the image processing unit 106.

[0019] The image forming unit 107 forms an image on a recording sheet using a recording material based on image data received directly from the image processing unit 106 or via a RAM or an external storage device.

[0020] The image reading unit 108 is an image sensor (a line sensor or an area sensor) for capturing an image of a recording image formed on a recording sheet by the image forming unit 107.

[0021] The I / F unit 109 functions as an interface for connecting the image forming system to an external device. The I / F unit 109 also functions as an interface for exchanging data with a communication device using infrared communication, a wireless LAN (Local Area Network), or the like, and as an interface for connecting to the Internet. This allows data, such as an input image, to be exchanged with the external device.

[0022] Each of the above-mentioned units is connected to a bus 110, and data can be exchanged via the bus 110. However, the image forming system may be configured such that each of the above-mentioned units (e.g., image forming unit 107) is connected via an I / F unit 109.

[0023] <Hardware configuration of image forming unit and image acquiring unit> 2(a) to 2(d) are schematic diagrams showing the image forming unit 107 according to this embodiment. Note that the image forming unit 107 in this embodiment is an inkjet type (IJ type) printer that forms an image by ejecting ink from nozzles onto a recording paper.

[0024] 2(a), the image forming unit 107 includes a plurality of recording heads 202 to 205 corresponding to black (K), cyan (C), magenta (M), and yellow (Y), respectively. It also includes a recording head 201 that ejects a primer (P) for fixing the ink onto a recording sheet 207. The primer is a colorless and transparent liquid.

[0025] 2(b), the recording heads 201 to 205 are configured by combining a plurality of head modules. The head modules 201a, 201b, and 201c that configure the recording head 201 are arranged alternately in the paper transport direction.

[0026] 2(c), head module 201a is composed of a plurality of chip modules 201a-1 to 201a-5. In this case, each chip module is connected to an independent board.

[0027] Figure 2(d) is a diagram of one of the chip modules as seen from the paper side, showing that the chip module has multiple nozzles. In the example shown in Figure 2(d), the chip module has 16 nozzles. The nozzle arrangement resolution is 1200 dpi.

[0028] The recording paper 207 is transported in the direction indicated by the arrow 208 in the figure by the rotation of the transport roller 206 (and other rollers, not shown) by the driving force of a motor (not shown). Then, while the recording paper 207 is being transported, ink and primer are ejected from the multiple nozzles of each of the recording heads 201 to 205 in accordance with the recording data, thereby sequentially forming an image for one raster corresponding to the nozzle rows of each recording head. In this way, by repeating the ejection operation from each recording head onto the transported recording paper, it is possible to record, for example, an image for one page.

[0029] 2(a), the image reading unit 108 is a line sensor that covers the entire surface of the recording paper and is installed downstream of the recording heads 201 to 205. That is, after an image is formed by the recording heads 201 to 205, the recording paper 207 is transported to the image reading unit 108. The image reading unit 108 sequentially captures and acquires images of the transported recording paper as, for example, RGB information or luminance information, and stores the images in the external storage device 105 as two-dimensional image data.

[0030] <Functional configuration of the image processing unit> The image processing unit 106 will be described below with reference to Figures 3 and 4. Figure 3 shows the configuration of the image processing unit 106, and Figure 4 is a flowchart showing the process flow when printing a normal user image.

[0031] As shown in FIG. 3, in the first embodiment, the determination result of the paper deformation determination unit 308 is sent to a determination image generation unit 307 and a color separation table selection unit 309 .

[0032] In S401 of Fig. 4, the user image acquisition unit 301 acquires an arbitrary input image designated by a user. In this embodiment, the input image is assumed to be image data of 8 bits for each of RGB. When the user image acquisition unit 301 acquires the input image, the process proceeds to S402.

[0033] In S402, the color separation processing unit 302 separates the RGB data into 16-bit gradation data (density data) of the ink colors of the recording device: C (cyan), M (magenta), Y (yellow), and K (black). In the ink color separation process, a color separation table 303 is used. The color separation table 303 is a lookup table (LUT) that stores the correspondence between RGB and CMYK. The color separation table 303 used is one selected by a color separation table selection unit 309 for each type of recording paper. Details of the color separation table selection process will be described later. Once the color separation processing unit 302 has performed the color separation process into CMYK, the process proceeds to S403.

[0034] In S403, the primer image generating unit 304 generates 16-bit image data of P (primer). For pixel positions where any of the CMYK images is 0 or greater, the pixel value of the primer is set to P1, and for other pixel positions, an image is generated where the pixel value of the primer is set to P2. In this embodiment, P1=8192, P2=0. When the primer image generating unit 304 generates the primer image data, the process proceeds to S404.

[0035] In S404, the HT processing unit 305 (HalfTone processing unit) performs quantization processing on the above CMYK image and primer image. In this embodiment, 1-bit binary data for five planes of CMYK and P is generated. As a quantization processing method, this embodiment uses a known dither method, but other pseudo halftone processing such as an error diffusion method may also be used. When the HT processing unit 305 executes the quantization processing, the process proceeds to S405.

[0036] In S405, the image forming unit 107 drives the recording head based on the dot data obtained by quantization, and performs recording by ejecting ink of each color and a primer onto the recording paper. When the image formation on the recording paper is completed, a printed matter 306 on which the user image is printed is obtained.

[0037] <Color separation table selection process> Next, the color separation table selection process will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the process flow for determining the color separation table 303 to be used.

[0038] In S501, the determination image generating unit 307 initializes the maximum ink ejection amount Vmax. In this embodiment, it is initialized to the maximum value of 16 bits, 65535. When the initialization of the maximum ink ejection amount Vmax is completed, the process proceeds to S502.

[0039] In S502, the judgment image generating unit 307 generates a judgment image (chart image). The judgment image is a 16-bit CMYK image, similar to the user image. An example of the judgment image is shown in FIG. 6(a).

[0040] 6A includes a region 601 having a high moisture content and a region 602 having a low moisture content. In FIG. 6A, the left half corresponds to region 601, and the right half corresponds to region 602.

[0041] In the area 601, an image for determination is printed in which a grid pattern 603, which is a recording pattern in which a specific design is regularly repeated in K ink, and a uniform density pattern 604, which is recorded in Y ink, includes the grid pattern 603, and has a predetermined density, are superimposed. At this time, the image for determination is generated so that the ink ejection amount of the uniform density pattern 604 becomes Vmax. When the image for determination generation unit 307 generates the image for determination, the process proceeds to S503.

[0042] In S503, the primer image generation unit 304 generates 16-bit image data for P (primer). As with printing a user image, an image is generated in which the pixel value of the primer is set to P1 for pixel positions where any of the CMYK images is 0 or greater, and the pixel value of the primer is set to P2 for other pixel positions. In this embodiment, P1=8192, P2=0. Once the primer image generation unit 304 has generated the primer image data, the process proceeds to S504.

[0043] In S504, the HT processing unit 305 performs quantization processing on the judgment image and the primer image. When the HT processing unit 305 executes the quantization processing, the process proceeds to S505.

[0044] In S505, the image forming unit 107 drives the recording head to form an image on the recording paper. When the image formation on the recording paper is completed, a printed matter 306 on which the image for determination is printed is obtained. When the printed matter 306 on which the image for determination is printed is obtained, the process proceeds to S506.

[0045] In S506, the image reading unit 108 captures an image of the printed matter 306 and obtains a read image. In this embodiment, the read image is obtained as an 8-bit 1200 dpi luminance image. When the read image is obtained, the process proceeds to S507.

[0046] In S507, the paper deformation determination unit 308 determines whether or not there is paper deformation. Details of the paper deformation determination process will be described later. If the paper deformation determination unit 308 determines that there is paper deformation, the process proceeds to S508. If the paper deformation determination unit 308 determines that there is no paper deformation, the process proceeds to S509.

[0047] In S508, the maximum ink ejection amount Vmax is decreased, and the process returns to S502. In this embodiment, 8192 is subtracted from the current maximum ink ejection amount Vmax. The changed value of Vmax is sent from the paper deformation determination unit 308 to the determination image generation unit 307.

[0048] In S509, the color separation table selection unit 309 selects a color separation table having a maximum ink ejection amount equal to or less than Vmax from among a plurality of color separation tables stored in the external storage device 105, and the color separation table selection process ends. The selected color separation table is held in correspondence with the recording paper.

[0049] <Paper deformation determination process> The paper deformation determination process executed by paper deformation determination unit 308 will be described with reference to Fig. 7. Fig. 7 is a flowchart showing the flow of the paper deformation determination process.

[0050] In S701, feature points are detected from the read image acquired in S506. In this embodiment, edges are detected using a known Sobel filter, and then feature points are detected by detecting intersections of the edges. For simplicity, the following description will be given assuming that the four points shown as points 6031 to 6034 in FIG. 6(a) are the detected feature points. The number of feature points is arbitrary as long as it is two or more. When feature points are detected from the read image, the process proceeds to S702.

[0051] In S702, the interval between the detected feature points is calculated. In this embodiment, attention is focused only on the distance in the longitudinal direction of the paper, and the distance d1 between the points 6031 and 6032, and the distance d2 between the points 6033 and 6034 are calculated. Once the distances d1 and d2 are calculated, the process proceeds to S703.

[0052] In S703, a reference distance between feature points is obtained. Here, the reference distance is the distance between feature points that is expected when there is no paper deformation. The reference distance is calculated from the image data of the determination image generated by the determination image generating unit 307. The reference distance between the point 6031 and the point 6032 is calculated as d1. * , the reference interval between point 6033 and point 6034 is d2 * When the reference interval between feature points is acquired, the process proceeds to S704.

[0053] In S704, the absolute value of the difference between the interval between the feature points acquired in S702 and the reference interval acquired in S703 is calculated.

[0054] That is, between points 6031 and 6032, Δd1 = |d1 - d1 * |, between points 6033 and 6034, Δd2 = |d2 - d2 * After Δd1 and Δd2 are calculated, the process proceeds to S705.

[0055] In S705, if the maximum absolute value of the difference between the interval between the feature points acquired in S702 and the reference interval acquired in S703, calculated in S704, is greater than a threshold value, it is determined that there is paper deformation.

[0056] In the above description, an example was described in which the image for determination was printed on the left half of the paper, but the image for determination is not limited to this, and an image printed on a smaller area may be used as long as the paper deformation can be determined. Also, the image for determination may be printed on the entire paper to determine the paper deformation.

[0057] <Modification> In the first embodiment, an example has been described in which the color separation table selection unit 309 selects from among a plurality of color separation tables stored in the external storage device 105, but the present disclosure is not limited to the above example. For example, instead of selecting a color separation table, the present disclosure may be applied to a configuration including a generation unit that generates a color separation table so that the ink ejection amount is equal to or less than Vmax.

[0058] Also, a configuration may be adopted in which the maximum ink ejection amount of the image forming device is notified to the user, and the user sets the maximum ink ejection amount in the external color separation table generating means based on this value. If this method is adopted, the image forming device prints an image for determination based on the maximum ink ejection amount set by the user, and the user checks whether or not paper deformation due to cockling has occurred. If the user checks whether or not paper deformation due to cockling has occurred, he or she changes the setting of the maximum ink ejection amount in the external color separation table generating means and prints the image for determination again to check whether or not paper deformation due to cockling has occurred. By repeating this process, the user can determine the maximum ink ejection amount at which paper deformation due to cockling does not occur.

[0059] Although an example has been described in which edge intersections are used to detect feature points in the paper deformation determination unit 308, any method for detecting feature points may be used. Feature amounts may be calculated using a known Harris corner detection method or the like.

[0060] 6(a) is used as an example of the determination image generated by the determination image generating unit 307, but the image is not limited to a uniform pattern as long as it can provide sufficient moisture to the region 601. For example, printing a pattern that avoids the vicinity of the grid pattern 603 is suitable for suppressing bleeding of the grid pattern 603.

[0061] In order to suppress bleeding, a configuration may be adopted in which first only the grid pattern 603 is printed and dried, and then the printed matter is returned using a transport mechanism for double-sided printing, and the uniform density pattern 604 is printed and scanned.

[0062] Furthermore, the pattern for detecting feature points is not limited to a lattice pattern, and any pattern may be used as long as the positions of feature points can be detected. Figures 8(a) to 8(g) show several examples of other patterns.

[0063] Fig. 8(a) shows an example using a regularly arranged dot pattern. In this case, the center of gravity of each dot can be used as a feature point.

[0064] Fig. 8(b) shows an example of arranging rectangular patterns. In this case, the four corners of each rectangle can be used as feature points.

[0065] Figure 8(c) is an example of a random dot pattern. In this case, it is possible to use the Euclidean distance between the selected dot and its neighboring points as the distance between feature points, rather than the distance in the longitudinal direction of the image. In the case of Figure 8(c), the distance between feature points is not at a constant interval, but changes based on the selected dot and its neighboring points.

[0066] Fig. 8(d) is an example consisting of lines in the short side direction (width direction) only. In this case, since the edge is a collection of feature points, it can be expanded to a form in which the change in the distance between edges is used to determine the paper deformation.

[0067] 8(e) is an example in which the lattice pattern 603 is also recorded in the low-water content region 602. In this example, the distance from the feature point 6035 to the feature point 6038 in the low-water content region 602 can be used as a substitute for the reference interval.

[0068] In addition, we have explained the case where the paper deformation occurs in the longitudinal direction of the image, but it is known that the direction of the paper deformation is affected by the grain of the paper. Therefore, as shown in Figure 8(f), it is possible to use an image in which the orientation of the judgment image is rotated 90 degrees to take the grain of the paper into consideration. In this case, the distance between feature points is only the distance in the short side direction (width direction) of the paper.

[0069] It is also possible to repeat printing and measurement while gradually changing the amount of ink in a pattern with uniform density. As shown in areas 605 to 608 in Fig. 8(g), multiple patterns with different ink amounts can be arranged on the paper. In this case, by extracting feature points for each of areas 605 to 608 and determining whether the paper is deformed, it is possible to obtain the maximum appropriate ink ejection amount Vmax.

[0070] In either case, it is desirable that the arrangement of feature points be denser in the direction of the paper deformation than in the direction perpendicular to the paper deformation.

[0071] In the present embodiment, an example has been described in which the grid pattern 603 of the determination image is printed in K ink, and the uniform density pattern 604 is printed in Y ink. As long as the color of the ink used to print the grid pattern 603 is different from the color of the ink used to print the uniform density pattern 604, the selection of the color of the ink used to print the grid pattern 603 and the color of the ink used to print the uniform density pattern 604 may be arbitrary. Alternatively, the ink used to print the grid pattern 603 may be fixed to K ink, and a color different from the K ink may be selected as the color of the ink used to print the uniform density pattern 604.

[0072] In this embodiment, the luminance of the judgment image is measured by the image reading unit 108, and it is preferable to select both inks so that the luminance of the ink for recording the grid pattern 603 is lower than the luminance of the ink used for the uniform density pattern 604. This makes it possible to easily obtain feature points even when the inks are superimposed.

[0073] More precisely, it is important that the feature points can be easily detected by the image reading unit 108. For example, if the image reading unit 108 can detect infrared rays, it is preferable to print the grid pattern 603 with ink having a high infrared absorption rate, and print the uniform density pattern 604 with ink having a low infrared absorption rate.

[0074] In addition, since the moisture content is the predominant cause of paper deformation, the uniform density pattern 604 may be printed using something other than ink. That is, it may be printed using a primer, or a device may be configured to apply the moisture of the primer. In this case, the amount of ink equivalent to the amount of moisture applied is calculated from the moisture content of the primer.

[0075] Although an example of determining paper deformation using only the change in distance between feature points has been described, the paper deformation determination based on density change, which has been described as a conventional technique, may also be used in combination. For example, by determining that there is paper deformation when the change in distance between feature points is equal to or greater than a predetermined value and the measured density change is equal to or greater than a predetermined value, it is possible to further reduce erroneous determinations.

[0076] By carrying out the above-described process control, according to the first embodiment, it becomes possible to determine paper deformation due to cockling with high accuracy.

[0077] [Embodiment 2] In the first embodiment, an example is described in which the maximum ink ejection amount Vmax of the color separation table is obtained based on the result of the paper deformation determination. In the second embodiment, an example is described in which the primer amount P2 of the primer image in the non-printing area is obtained based on the result of the paper deformation determination. Note that the following description will focus on the differences from the first embodiment described above, and will omit a description of the same points as in the first embodiment.

[0078] <Primer amount determination process> The primer amount determination process will be described below with reference to Fig. 9 and Fig. 10. Fig. 9 is a diagram showing the configuration of the image processing unit 106 in the second embodiment, and Fig. 10 is a diagram showing a flowchart of the primer amount determination process in the second embodiment.

[0079] As shown in FIG. 9, unlike the first embodiment, the determination result of the paper deformation determination unit 308 is sent to a primer image generation unit 304 and a determination image generation unit 307 .

[0080] 10, in S1001, the non-print area primer amount P2 is initialized. In the second embodiment, P2 is initialized to 0. When the initialization of the non-print area primer amount P2 is completed, the process proceeds to S1002.

[0081] In S1002, the judgment image generating unit 307 generates an image for judgment. An example of the image for judgment is shown in Fig. 6(a). When the judgment image generating unit 307 generates the image for judgment, the process proceeds to S1003.

[0082] In S1003, the primer image generation unit 304 generates 16-bit image data of P (primer). The primer image generation unit 304 generates an image in which the pixel value is set to P1 for pixel positions where any of the CMYK images is 0 or greater, and the pixel value is set to P2 for other pixel positions. In the second embodiment, P1=8192. Once the primer image generation unit 304 generates the primer image, the process proceeds to S1004.

[0083] In S1004, the HT processing unit 305 performs quantization processing on the above-mentioned judgment image and primer image. When the HT processing unit 305 completes the quantization processing, the process proceeds to S1005.

[0084] In S1005, the image forming unit 107 drives the recording head to form an image. When the image formation is completed, a printed matter 306 is obtained. When the image forming unit 107 generates the printed matter 306, the process proceeds to S1006.

[0085] In S1006, the image reading unit 108 captures an image of the printed matter 306 and acquires a read image. When the image reading unit 108 acquires the read image, the process proceeds to S1007.

[0086] In S1007, the paper deformation determination unit 308 determines whether or not there is paper deformation. If the paper deformation determination unit 308 determines that there is paper deformation, the process proceeds to S1008. If the paper deformation determination unit 308 determines that there is no paper deformation, the process proceeds to S1009.

[0087] In S1008, the primer amount P2 is increased, and the process returns to S1002. In the second embodiment, 8192 is added to the current primer amount P2. The added amount P2 is sent from the paper deformation determination unit 308 to the primer image generation unit 304.

[0088] In S1009, the primer image generating unit 304 holds the correspondence between the primer amount P2 and the recording paper, and the primer amount determination process ends.

[0089] As described above, it is possible to accurately determine paper deformation due to cockling in embodiment 2 as well. Furthermore, in embodiment 2, by performing a primer amount determination process, a primer is applied to the non-printed area, reducing the difference in moisture amount between the image printed area and the non-printed area, and paper deformation can be suppressed.

[0090] <Modification> Although an example of determining the amount of ink and the amount of primer has been described in the first embodiment and the second embodiment, respectively, it is also possible to set various printing conditions that affect paper deformation in a similar manner. For example, in a configuration equipped with a means for drying the printed matter with hot air, it is possible to similarly design the drying temperature and the amount of drying air. In addition, the printing speed also affects paper deformation, so it is possible to similarly design it.

[0091] [Embodiment 3] In the first embodiment, an example was described in which a reference interval to be compared with a measured interval is obtained from a judgment image. However, the grid pattern 603 may contain a print position shift caused by the accuracy of the image forming unit 107. In this case, it is difficult to separate the change in the interval between feature points into a change in the interval caused by paper deformation and a change in the interval caused by position shift, and the paper deformation may be erroneously judged. Therefore, in the third embodiment, a method for dealing with the above problem will be described. Note that the following mainly describes the points that are different from the above-mentioned embodiment, and the same points as the above-mentioned embodiment will be omitted.

[0092] <Paper deformation determination process using reference image> The paper deformation determination process in the third embodiment will be described below with reference to Fig. 6(a), Fig. 6(b), and Fig. 7. Fig. 6(a) shows an example of a determination image, and Fig. 6(b) shows an example of a reference image.

[0093] In the reference image, only the grid pattern 603 of the judgment image is printed using K ink.

[0094] The difference between the third embodiment and the first embodiment is that the above-mentioned reference image is used to obtain the reference interval in S703 of FIG.

[0095] 7, the processes in S701 and S702 are the same as those in the first embodiment, and the interval between the feature points of the determination image is calculated. Once the interval between the feature points of the determination image is calculated, the process proceeds to S703.

[0096] In S703, the reference interval between feature points is obtained by reading the reference image printed using only the K ink, unlike in the first embodiment. Once the reference interval between feature points is obtained, the process proceeds to S704 and S705.

[0097] In S704 and S705, as in the first embodiment, the absolute value of the difference between the spacing between feature points in the determination image and the reference spacing between feature points is calculated, and if this value is greater than a predetermined threshold, the paper deformation determination unit 308 determines that paper deformation has occurred.

[0098] Thereafter, similarly to the first embodiment, the flow of the color separation table selection process shown in FIG. 5 is executed.

[0099] By performing the processing control described above, according to the third embodiment, even if the grid pattern 603 includes a print position shift caused by the accuracy of the image forming unit 107, it is possible to determine paper deformation due to cockling with high accuracy.

[0100] The judgment image and the reference image may be printed and scanned on separate sheets of the same type of paper, or may be printed and scanned on a single sheet of paper. In the latter configuration, a reference image represented only by a grid pattern 603 is printed and scanned first, and then the printed matter is returned using a double-sided printing transport mechanism, and a uniform density pattern 604 is printed and scanned.

[0101] <Embodiment 4> In the first embodiment, an example has been described in which the grid pattern 603 is printed with K ink and the uniform density pattern 604 is printed with Y ink. This is because the relatively high density K ink makes it easy to obtain feature points even when the relatively low density Y ink is superimposed. In other words, the K ink is used to obtain feature points, and the Y ink is used to provide moisture.

[0102] In the fourth embodiment, it will be described that the present disclosure can be implemented even in the case of a determination image in which the ink is one color. Note that the following description will focus on the differences from the above-described embodiments, and in cases where individual processes performed in the fourth embodiment are similar to those described in the above-described embodiments, their description will be omitted.

[0103] Fig. 11 is an example of a determination image in the fourth embodiment. As in Fig. 6(a), the determination image is composed of a region 601 with a high moisture content and a region 602 with a low moisture content. Region 601 is printed with K ink, and is a pattern in which a plurality of rectangles having a predetermined density are arranged in a tile shape with gaps between them. The ink color of the rectangular pattern may be any color.

[0104] At this time, as shown in Fig. 11, points 1131 to 1134 which are gaps in the rectangular pattern can be acquired as feature points similar to the lattice pattern 603. If points 1131 to 1134 in Fig. 11 can be acquired, the subsequent process can be performed to execute the paper deformation determination process of the first embodiment, thereby making it possible to determine paper deformation due to cockling.

[0105] In the above, if paper deformation due to cockling occurs, the maximum ink ejection amount Vmax is reduced and the color separation table selection process of embodiment 1 is executed. This makes it possible to select an appropriate color separation table that does not cause paper deformation due to cockling.

[0106] Moreover, the fourth embodiment can also be applied to a configuration including a generating unit that generates a color separation table so that the ink ejection amount is equal to or less than Vmax, rather than selecting a color separation table.

[0107] Furthermore, a configuration may be adopted in which the maximum ink ejection amount of the image forming apparatus is notified to the user, and the user sets the maximum ink ejection amount in an external color separation table generating means based on this value. By adopting this method, as described in the modified example of the first embodiment, the user can determine the maximum ink ejection amount at which paper deformation due to cockling does not occur.

[0108] Although the above describes an example in which paper deformation is determined using only the change in distance between feature points, it is also possible to use paper deformation determination based on density change, which was described as a conventional technique. For example, by determining that paper deformation exists when the change in distance between feature points is equal to or greater than a predetermined value and the measured density change is equal to or greater than a predetermined value, it is possible to further reduce erroneous determination of paper deformation.

[0109] 11, a rectangle is illustrated as an example of the figure of the uniform density pattern for which the distance between feature points can be measured, but the figure of the uniform density pattern for which the distance between feature points can be measured is not limited to this. For example, the figure may be a square, parallelogram, trapezoid, rhombus, triangle, circle, or other shape. The figure of the uniform density pattern is not limited to the same shape, and may be a pattern in which the shape of the figure gradually increases from the top end of the paper, or a pattern in which the shape of the figure gradually decreases from the top end of the paper.

[0110] By carrying out the process control described above, according to the fourth embodiment, even if a determination image of a single ink is used, it is possible to perform a highly accurate determination of paper deformation due to cockling.

[0111] (Other Examples) The present disclosure can also be realized by a process in which a program for implementing one or more functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that implements one or more functions.

[0112] The disclosure of the above-described embodiments includes the following configurations and methods.

[0113] (Configuration 1) An image forming device that forms an image on paper using ink of multiple colors, comprising: a reading means that reads paper on which a chart image is printed, the chart image consisting of a first recording pattern using ink of a first color and a second recording pattern using ink of a second color different from the first color and having a predetermined density that encompasses at least a portion of the first recording pattern; and a detection means that detects deformation of the paper based on the difference in moisture content between a portion of the paper that corresponds to the area where the chart image is printed and a portion of the paper that corresponds to a non-printed area in the read image obtained by the reading means.

[0114] (Configuration 2) The image forming apparatus according to configuration 1, wherein the first recorded pattern is a pattern in which the distance between characteristic points of a specific design that is regularly repeated by the reading means can be obtained in the direction of paper deformation.

[0115] (Configuration 3) The image forming apparatus according to configuration 2, wherein the distance between the feature points in the paper deformation direction is shorter than the distance between the feature points in a direction perpendicular to the paper deformation.

[0116] (Configuration 4) The image forming apparatus according to any one of Configurations 1 to 3, wherein the first recording pattern includes a plurality of edges or a plurality of corners.

[0117] (Configuration 5) In the image forming apparatus according to any one of Configurations 1 to 4, the second recording pattern is a pattern that uses a larger amount of ink than the first recording pattern.

[0118] (Configuration 6) An image forming apparatus as described in any one of Configurations 1 to 5, characterized in that a brightness value measured by the reading means in a first recording pattern using ink of the first color is lower than a brightness value in a second recording pattern using ink of the second color.

[0119] (Configuration 7) The image forming apparatus according to any one of Configurations 1 to 6, wherein the first color is black.

[0120] (Configuration 8) The image forming apparatus according to any one of Configurations 1 to 7, wherein the reading means calculates a distance between a plurality of feature points by reading a plurality of feature points from the printed chart image in a paper deformation direction, and the detection means detects the paper deformation using an absolute value of a difference between the distance between the plurality of feature points and a predetermined distance.

[0121] (Configuration 9) The image forming apparatus according to configuration 8, wherein the predetermined distance is a distance between feature points obtained from data of the chart image.

[0122] (Configuration 10) The image forming apparatus according to configuration 8, wherein the predetermined distance is a distance between feature points measured by the reading means using a printed matter on which only the first recording pattern is printed.

[0123] (Configuration 11) The image forming apparatus according to configuration 8, wherein, when printing the chart image, the reading means measures the predetermined distance when only the first recording pattern is printed.

[0124] (Configuration 12) The image forming apparatus according to any one of configurations 1 to 10 or 12, characterized in that when printing the chart image, after only the first recording pattern is printed, the paper is dried and the second recording pattern is recorded.

[0125] (Configuration 13) The image forming apparatus according to configuration 1, wherein the reading means calculates a distance between multiple feature points by reading multiple feature points in the paper deformation direction from the printed chart image, and the detection means detects the paper deformation using an absolute value of a difference between the distance between the multiple feature points and a predetermined distance, and a density change in the paper deformation direction measured by the reading means.

[0126] (Configuration 14) The image forming apparatus according to any one of Configurations 1 to 13, further comprising: a control unit that acquires printing conditions under which the chart image was printed.

[0127] (Configuration 15) The image forming apparatus according to Configuration 14, wherein the printing conditions include at least one of an ink amount and a primer amount.

[0128] (Configuration 16) In the image forming apparatus according to configuration 14 or 15, the control means sets the printing conditions based on a result of the detection means detecting deformation of the paper.

[0129] (Configuration 17) The image forming apparatus according to configuration 14 or 15, further comprising: a notification unit that notifies a user of the printing conditions acquired by the control unit.

[0130] (Method 1) A control method for an image forming device that forms an image on paper using ink of multiple colors, comprising the steps of: reading paper on which a chart image is printed, the chart image being composed of a first recording pattern using ink of a first color and a second recording pattern using ink of a second color different from the first color and having a predetermined density that encompasses at least a portion of the first recording pattern; and detecting deformation of the paper based on the difference in moisture content between a portion of the paper that corresponds to the area where the chart image is printed and a portion of the paper that corresponds to a non-printed area in the read image obtained by reading the paper.

[0131] (Configuration 18) An image forming apparatus comprising: a reading means for reading paper on which a chart image consisting of a specific pattern is printed; and a detection means for detecting deformation of the paper based on the difference in moisture content between a portion of the paper corresponding to the area on which the chart image is printed in the read image obtained by the reading means and a portion of the paper corresponding to a non-printed area, wherein each of the specific patterns has a predetermined shape, an area of ​​a certain size or more, and a predetermined density.

[0132] (Configuration 19) The image forming apparatus according to configuration 18, wherein the chart image has a pattern in which the distance between regularly repeated feature points can be obtained by the reading means in the direction of paper deformation.

[0133] (Configuration 20) The image forming apparatus according to configuration 19, wherein the distance between the feature points in the paper deformation direction is shorter than the distance between the feature points in a direction perpendicular to the paper deformation.

[0134] (Configuration 21) The image forming apparatus according to any one of Configurations 18 to 20, wherein the chart image includes a plurality of edges or a plurality of corners.

[0135] (Configuration 22) The image forming apparatus according to any one of Configurations 18 to 21, wherein the color of the specific design is black.

[0136] (Configuration 23) The image forming apparatus according to any one of Configurations 18 to 22, characterized in that the reading means calculates a distance between a plurality of feature points by reading a plurality of feature points from the printed chart image in a paper deformation direction, and the detection means detects the paper deformation using an absolute value of a difference between the distance between the plurality of feature points and a predetermined distance.

[0137] (Configuration 24) The image forming apparatus according to Configuration 23, wherein the predetermined distance is a distance between feature points obtained from data of the chart image.

[0138] (Configuration 25) The image forming apparatus according to Configuration 18, wherein the reading means calculates a distance between multiple feature points by reading multiple feature points in the paper deformation direction from the printed chart image, and the detection means detects the paper deformation using an absolute value of a difference between the distance between the multiple feature points and a predetermined distance, and a density change in the paper deformation direction measured by the reading means.

[0139] (Configuration 26) The image forming apparatus according to any one of Configurations 18 to 25, further comprising: a control unit that acquires printing conditions under which the chart image was printed.

[0140] (Configuration 27) The image forming apparatus according to Configuration 26, wherein the printing conditions include at least one of an ink amount and a primer amount.

[0141] (Configuration 28) In the image forming apparatus according to Configuration 26 or 27, the control means sets the printing conditions based on a result of the detection means detecting deformation of the paper.

[0142] (Configuration 29) The image forming apparatus according to Configuration 26 or 27, further comprising: a notification unit that notifies a user of the printing conditions acquired by the control unit.

[0143] (Method 2) A control method for an image forming device, comprising the steps of: reading paper on which a chart image consisting of a specific pattern is printed; and detecting deformation of the paper based on the difference in moisture content between a portion of the paper that corresponds to the area on which the chart image is printed and a portion of the paper that corresponds to a non-printed area in the read image obtained by reading the paper, wherein each of the specific patterns has a predetermined shape, an area of ​​a certain size or more, and a predetermined density.

Claims

1. An image forming apparatus that forms an image on a sheet using inks of a plurality of colors, a reading unit that reads a sheet on which a chart image is printed, the chart image including a first recording pattern using ink of a first color and a second recording pattern having a predetermined density including at least a part of the first recording pattern and using ink of a second color different from the first color; a detection unit that detects deformation of the sheet based on a difference between a moisture content of a portion corresponding to the area where the chart image is printed and a moisture content of a portion corresponding to a non-printing area in the read image obtained by the reading unit in an area of the sheet; comprising: An image forming apparatus characterized by the above.

2. The image forming apparatus according to claim 1, wherein the first recording pattern is a pattern in which distances between feature points of a specific pattern regularly repeated by the reading unit can be obtained in the sheet deformation direction.

3. The image forming apparatus according to claim 2, wherein a distance between feature points in the sheet deformation direction is shorter than a distance between feature points in a direction orthogonal to the sheet deformation.

4. The image forming apparatus according to claim 1, wherein the first recording pattern includes a plurality of edges or a plurality of corners.

5. The image forming apparatus according to claim 1, wherein the second recording pattern is a pattern that uses a larger amount of ink than the first recording pattern.

6. The image forming apparatus according to claim 1, wherein a luminance value measured by the reading unit in the first recording pattern using ink of the first color is lower than a luminance value in the second recording pattern using ink of the second color.

7. The image forming apparatus according to claim 1, wherein the reading unit reads a plurality of feature points in the sheet deformation direction from the printed chart image, the detection unit calculates distances between the plurality of feature points, and detects deformation of the sheet using an absolute value of a difference between the distances between the plurality of feature points and a predetermined distance.

8. The image forming apparatus according to claim 7, wherein the predetermined distance is a distance between feature points obtained from data of the chart image.

9. The image forming apparatus according to claim 7, wherein the predetermined distance is a distance between feature points measured by the reading unit using a printed matter on which only the first recording pattern is printed.

10. When printing the chart image, after only the first recording pattern is printed, the paper is dried, and then the second recording pattern is recorded. The image forming apparatus according to claim 1, characterized in that.

11. The reading means reads a plurality of feature points in the paper deformation direction from the printed chart image, the detecting means calculates the distance between the plurality of feature points, and the absolute value of the difference between the distance between the plurality of feature points and a predetermined distance, and the image forming apparatus according to claim 1, characterized in that the deformation of the paper is detected using the density change in the paper deformation direction measured by the reading means.

12. A control method for an image forming apparatus that forms an image on a paper using a plurality of colors of ink, A step of reading a paper on which a chart image including a first recording pattern using a first color ink and a second recording pattern having a predetermined density including at least a part of the first recording pattern using a second color ink different from the first color is printed; A step of detecting the deformation of the paper based on the difference between the moisture content of a portion corresponding to the area where the chart image is printed in the read image of the paper and the moisture content of a portion corresponding to the non-printing area among the areas of the paper; Comprising A control method for an image forming apparatus, characterized in that.

13. A program for causing a computer to function as the image forming apparatus according to any one of claims 1 to 11.

14. Reading means for reading a paper on which a chart image composed of a specific symbol is printed; Detecting means for detecting the deformation of the paper based on the difference between the moisture content of a portion corresponding to the area where the chart image is printed in the read image obtained by the reading means and the moisture content of a portion corresponding to the non-printing area among the areas of the paper; Comprising Each of the specific symbols has a predetermined shape, an area of a certain size or more, and a predetermined density. An image forming apparatus, characterized in that.

15. The chart image has a pattern in which the distance between regularly repeated feature points can be obtained in the paper deformation direction by the reading means. The image forming apparatus according to claim 14, characterized in that.

16. The distance between the feature points in the paper deformation direction is shorter than the distance between the feature points in the direction orthogonal to the paper deformation. The image forming apparatus according to claim 15, characterized in that.

17. The image forming apparatus according to claim 14, wherein the chart image includes a plurality of edges or a plurality of corners.

18. The reading means reads a plurality of feature points in the paper deformation direction from the printed chart image, the detecting means calculates a distance between the plurality of feature points, and uses an absolute value of a difference between the distance between the plurality of feature points and a predetermined distance to detect deformation of the paper. The image forming apparatus according to claim 14, characterized by the above.

19. The image forming apparatus according to claim 18, wherein the predetermined distance is a distance between feature points obtained from data of the chart image.

20. The reading means reads a plurality of feature points in the paper deformation direction from the printed chart image, the detecting means calculates a distance between the plurality of feature points, and uses an absolute value of a difference between the distance between the plurality of feature points and a predetermined distance, and a density change in the paper deformation direction measured by the reading means to detect deformation of the paper. The image forming apparatus according to claim 14, characterized by the above.

21. A step of reading a paper on which a chart image composed of a specific pattern is printed; A step of detecting deformation of the paper based on a difference in moisture content between a portion corresponding to the area where the chart image is printed in the read image of the paper and a portion corresponding to the non-printing area among the areas of the paper; Comprising: Each of the specific patterns has a predetermined shape, an area of a certain size or more, and a predetermined density. A control method for an image forming apparatus, characterized by the above.

22. A program for causing a computer to function as the image forming apparatus according to any one of claims 14 to 20.

Images