Image forming apparatus, method for adjusting image forming apparatus, and program

Abstract

To correctly execute color adjustment even when the patch density of a chart is increased.SOLUTION: An image forming apparatus 1 comprises: an image forming unit 5 that prints color adjustment chart images used for color adjustment on a conveyed sheet 50; and an image sensor 9 that reads the color adjustment chart images printed on the sheet 50. The image forming apparatus 1 comprises a control unit 10 that performs position adjustment of the print positions of the color adjustment chart images from the position of the conveyed sheet 50, and performs color adjustment by using the color adjustment chart images printed by the image forming unit 5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Known electrophotographic image processing devices, such as multifunction peripherals, are those that select a color measurement sensor depending on the paper (see Patent Document 1). Patent Document 1 describes an invention in which, in order to perform high-precision color matching, a color adjustment chart is first printed, and then the printed color adjustment chart is read by a color measurement sensor to perform color adjustment. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-141383 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in order to perform high-resolution color adjustment with such a conventional image forming apparatus, the number of patches in the chart must be increased. Increasing the number of patches in this way requires printing the color adjustment chart on a large amount of paper, which increases paper waste. Furthermore, as the number of patches increases, the number of times they need to be read also increases, which causes the problem of adjustment taking a long time. In the comparative example, the number of test charts was reduced by reducing the patch size and increasing the density. If the patch size is small and the number of patches in the main scanning direction is large, the number of times the patches need to be read decreases, thereby shortening the adjustment time. However, increasing the patch density posed a problem in that even a slight deviation in the patch reading position would result in the measurement of an adjacent patch, resulting in a failure of color adjustment.

[0005] The image forming apparatus of the present invention has been made in view of the above-mentioned background, and aims to perform color adjustment correctly even when the patch density of the chart is increased. [Means for solving the problem]

[0006] The above-mentioned problems of the present invention can be solved by the following configuration. (1) An image forming apparatus includes an image forming unit that prints an image on a transported sheet of paper, an image sensor that reads the paper, and a control unit that adjusts the printing position on the paper by the image forming unit based on the position of the image printed on the paper, and then performs color adjustment of the image forming unit using the chart printed by the image forming unit. (2) The image forming device according to (1), wherein the image forming unit prints a marker on the paper, and the control unit adjusts the printing position based on the position of the marker on the paper, and then the image forming unit prints a chart. (3) The image forming apparatus according to (1) or (2), wherein the control unit is capable of performing multiple types of color adjustment with different degrees of accuracy, and when performing color adjustment with a predetermined degree of accuracy, adjusts the printing position in advance. (4) The image forming apparatus according to (1), wherein the control unit determines whether to adjust the print position based on the printing state of the image forming unit. (5) The image forming apparatus according to (4), wherein the control unit adjusts the print position of the image forming unit in advance when performing color adjustment during execution of a job. (6) In the image forming apparatus described in (5), if high-quality printing is set when printing each page in a job, the control unit adjusts the printing position and then performs color adjustment using the image. (7) In the image forming apparatus described in (4), when the print position is adjusted during job execution, the control unit changes the size interval of the patches according to the paper transport speed, thereby performing color adjustment of the image forming unit. (8) The image forming apparatus according to (4), wherein, during execution of a job, the control unit may print on the second sheet a chart having more patches arranged in the main scanning direction than the chart on the first sheet, after adjusting the printing position of the image forming unit, when the second sheet is of the same type as the first sheet to be printed in the job and the second sheet is longer in the main scanning direction and stored in a paper feed tray different from the paper feed tray storing the first sheet, and (9) The control unit may detect, during execution of a job, that a second sheet of paper, which is the same type as a first sheet of paper used in the job but is longer in the main scanning direction, is stored in one of the paper feed trays. In this case, the image forming unit changes the size interval of the patches of the chart for the second sheet of paper after adjusting the print position. The image forming device also prints a chart on the second sheet of paper in which more patches are arranged in the main scanning direction than the chart for the first sheet of paper. (10) In the image forming apparatus according to (4), when the patch size of the chart falls below a threshold or the patch spacing falls below a threshold, the control unit adjusts the print position of the image forming unit before printing the chart and performing color adjustment of the image forming unit. (11) The control unit stores, for each paper feed tray, the time when the image position was adjusted using the paper stored in that paper feed tray, and if the elapsed time from the stored time is within a threshold value or the number of printed sheets is within a threshold value, performs color adjustment without adjusting the printing position of the image forming unit. (4) An image forming apparatus. (12) In the image forming device described in (4), when there are multiple paper feed trays containing the same type of paper, the control unit selects one of the paper feed trays whose image position adjustment was performed within a threshold time, and performs color adjustment without adjusting the printing position of the image forming unit. (13) The image forming device described in (4) prints the chart using one of the following methods that can save the number of sheets of paper: a method of printing the chart by changing the patch size and / or patch spacing based on a threshold value for the timing of adjusting the position of the paper on which the chart is output; or a method of adjusting the image position and then printing the chart at a predetermined patch size. (14) The image forming device described in (4) prints the chart using either of the following methods that can reduce the time: a method of printing the chart with the patch size and / or patch spacing changed based on a threshold value for the timing of position adjustment of the paper on which the chart is to be printed, or a method of adjusting the image position and then printing the chart with a predetermined patch size. (15) A method for adjusting an image forming apparatus, comprising: a step in which an image forming unit prints an image on transported paper; a step in which a control unit reads the paper as an image using a sensor; a step in which the control unit adjusts a printing position on the paper by the image forming unit from the position of the image printed on the paper; and a step in which the control unit performs color adjustment of the image forming unit using a chart printed by the image forming unit. (16) An image forming apparatus includes a program for causing a computer that controls the apparatus to execute the steps of printing an image on transported paper using an image forming unit and reading the paper using an image sensor. The computer also executes the steps of adjusting the print position on the paper by the image forming unit based on the position of the image printed on the paper. The program also causes the computer to execute the steps of adjusting the color of the image forming unit using a chart printed by the image forming unit. [Effects of the Invention]

[0007] According to the present invention, color adjustment can be performed correctly even if the patch density of the chart is increased. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a side view schematically illustrating a configuration of an image forming apparatus according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing a configuration of a control unit in the image forming apparatus according to the first embodiment. [Figure 3] 6 is a flowchart illustrating color adjustment control by the image forming apparatus according to the first embodiment. [Figure 4]FIG. 10 is a plan view illustrating how two color adjustment chart images are combined into one image and color adjusted in the image forming apparatus according to the first embodiment. [Figure 5] 10 is a flowchart illustrating color adjustment control by an image forming apparatus according to a second embodiment. [Figure 6] FIG. 2 is a plan view of a sheet of paper on which a color adjustment chart image is printed. [Figure 7] 10 is a flowchart illustrating a color adjustment process in an image forming apparatus according to a third embodiment. [Figure 8] 10 is a flowchart illustrating a color adjustment process in an image forming apparatus according to a fourth embodiment. [Figure 9] 13 is a flowchart illustrating a color adjustment process in an image forming apparatus according to a fifth embodiment. [Figure 10] 13 is a flowchart illustrating a color adjustment process in an image forming apparatus according to a sixth embodiment. [Figure 11] 13 is a flowchart illustrating a color adjustment process in an image forming apparatus according to a seventh embodiment. [Figure 12] FIG. 13 is a plan view of a color adjustment chart image used for color adjustment when the conveying speed is slow in an image forming apparatus according to a seventh embodiment. [Figure 13] FIG. 13 is a plan view of a color adjustment chart image used for color adjustment when the conveying speed is medium in an image forming apparatus according to a seventh embodiment. [Figure 14] FIG. 13 is a plan view of a color adjustment chart image used for color adjustment when the conveying speed is high in an image forming apparatus according to a seventh embodiment. [Figure 15] 13 is a flowchart illustrating a color adjustment process in an image forming apparatus according to an eighth embodiment. [Figure 16] FIG. 19 is a plan view of a color adjustment chart image for explaining how conveyance is stopped during scanning in an image forming apparatus according to an eighth embodiment. [Figure 17] 13 is a flowchart illustrating a color adjustment process in an image forming apparatus according to a ninth embodiment. [Figure 18]FIG. 13 is a plan view of a color adjustment chart image used for color adjustment in a comparative example in an image forming apparatus according to a ninth embodiment. [Figure 19] FIG. 23 is a plan view of a color adjustment chart image in which a plurality of color adjustment chart images are grouped together in an image forming apparatus according to a ninth embodiment. [Figure 20] 10 is a flowchart illustrating a color adjustment process in an image forming apparatus according to a tenth embodiment. [Figure 21] 23 is a flowchart illustrating a color adjustment process in the image forming apparatus according to the eleventh embodiment. [Figure 22] 23 is a flowchart illustrating a color adjustment process in an image forming apparatus according to a twelfth embodiment. [Figure 23] 23 is a flowchart illustrating a color adjustment process in an image forming apparatus according to a thirteenth embodiment. [Figure 24] FIG. 23 is a plan view of three color adjustment chart images used for color adjustment output by the image forming apparatus according to the thirteenth embodiment. [Figure 25] FIG. 23 is a plan view of a position adjustment sheet on which a marker image is printed and a color adjustment chart image in which a plurality of color adjustment chart images are compiled, in an image forming apparatus according to a thirteenth embodiment. [Figure 26] 23 is a flowchart illustrating a color adjustment process in an image forming apparatus according to a fourteenth embodiment. [Figure 27] FIG. 23 is a plan view of three color adjustment chart images used for color adjustment output by the image forming apparatus according to the fourteenth embodiment. [Figure 28] FIG. 24 is a plan view of a position adjustment sheet on which a marker image is printed and a color adjustment chart image in which a plurality of color adjustment chart images are compiled, in an image forming apparatus according to a fourteenth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] [First embodiment] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing the overall configuration of an image forming apparatus 1 according to the first embodiment, and FIG. 2 is a block diagram of the image forming apparatus 1. As shown in FIG.

[0010] [Configuration of image forming device] As shown in FIG. 1, the image forming apparatus 1 includes a main body 2 having a housing, a touch panel display 4, an image forming unit 5, a paper feed tray unit 6, a conveying unit 7, and a paper discharge tray unit 11.

[0011] The touch panel display 4 is configured by superimposing a transparent touch panel on a liquid crystal display, and displays images, figures, or characters, and also accepts user operations. The image forming unit 5 forms an electrophotographic image on paper. The paper feed tray unit 6 includes paper feed trays 6a to 6d and paper discrimination sensors 8a to 8d of the paper discrimination unit 8. The paper feed trays 6a to 6d store multiple types of paper, such as a first paper sheet 50a, a second paper sheet 50b, a third paper sheet 50c, and a fourth paper sheet 50d. The paper discrimination sensor 8a discriminates the type of paper stored in the paper feed tray 6a. The second paper sheet 50b is stored in the paper feed tray 6b. The paper discrimination sensor 8b of the paper discrimination unit 8 can also determine whether or not paper is present in each of the paper feed trays 6a to 6d.

[0012] A third sheet of paper 50c is stored in paper feed tray 6c. A paper discrimination sensor 8c discriminates the type of paper stored in paper feed tray 6c. A fourth sheet of paper 50d is stored in paper feed tray 6d. A paper discrimination sensor 8d discriminates the type of paper stored in paper feed tray 6d. In the conveying section 7, the paper stored in the paper feed tray section 6 is conveyed to the paper discharge tray section 11 via the image forming section 5.

[0013] The image forming apparatus 1 of the first embodiment also includes an image sensor 9 and a control unit 10 shown in Fig. 2. The image forming apparatus 1 may also be provided with an image reading unit that is provided with a scanner device using an ADF (Automatic Document Feeder) or the like and that sends the read image to the control unit 10.

[0014] Of these, paper 50 is transported to image forming unit 5 from paper feed tray unit 6 by transport unit 7. Image forming unit 5 prints an image on the transported paper 50. Control unit 10, which serves as a computer that controls image forming apparatus 1, causes image forming unit 5 to print an image of image data on paper 50 by a method that prints image data. Furthermore, when a color adjustment method is carried out as one of the image adjustment methods of the image forming apparatus 1, image data of a color adjustment chart image is printed on paper 50 and used. For this reason, the image forming unit 5 of the first embodiment prints image data of a color adjustment chart image as shown in FIG. 4, which is used for color adjustment and which has been input and stored in advance in the control unit 10, by printing a chart on paper 50.

[0015] Each of the color adjustment chart images 61, 62, and 63 is configured by arranging a plurality of square (or rectangular) patches of different colors and gradations (color shades) vertically and horizontally. The paper 51 in FIG. 4 is rectangular in plan view. The paper 51 is transported with its X direction (longer direction) aligned with the transport direction F by the transport unit 7. The color adjustment chart image 61 printed on the paper 51 has a total of 40 patches arranged in a grid, with four patches in the Y direction (shorter direction) and ten patches in the X direction. Each patch is printed so that the combinations of color (red, blue, yellow, green, or intermediate colors thereof, etc.) and gradations (color shades) (hereinafter referred to as colors, etc.) are all different.

[0016] Furthermore, the color adjustment chart image 62 printed on the paper 52 in FIG. 4 has 5 patches in the Y direction and 10 patches in the X direction, a total of 50 patches of different colors and gradations, arranged in a grid pattern.

[0017] The method for adjusting the image forming apparatus is carried out using a total of 90 patches of color adjustment chart images 61 and 62 printed separately on two sheets of paper 51 and 52. In the adjustment method for the image forming apparatus 1 of the first embodiment, color adjustment can be performed to achieve color adjustment with a desired accuracy. The color adjustment of the first embodiment includes adjustment of color, etc. (hereinafter also referred to as color adjustment), which also adjusts gradation (color density). Note that the process of scanning and reading the color and gradation (color density) of a color adjustment chart image or a printed image using the image sensor 9 and converting them into data is referred to as colorimetry here. However, to print 90 patches in a size that allows color adjustment, two sheets of paper 51 and 52 are required. Therefore, the time equivalent to two sheets is required to print the color adjustment chart images 61 and 62. Furthermore, when reading the color adjustment chart images 61 and 62, the time equivalent to two sheets is also required to read the two sheets of paper 51 and 52 with the image sensor 9.

[0018] In contrast to this, for example, it is possible to arrange 90 patches, all of which are different in color and gradation, in a grid pattern, with 9 patches in the Y direction and 10 patches in the X direction, as in the color adjustment chart image 63 printed on paper 53 in Figure 4. In this case, each patch becomes smaller and the distance between adjacent patches becomes narrower. As a result, if the printing position of a patch on the paper 53 shifts, the patch recognized by the image sensor 9 is likely to be an adjacent patch. This makes it difficult to perform accurate color adjustments all at once on one sheet of paper 53 in a short time.

[0019] In the image forming apparatus 1 of the first embodiment, the image sensor 9 is provided on the exit side of the image forming unit 5. The image sensor 9 is configured with a color measurement sensor such as a line sensor whose scanning direction is perpendicular to the conveying direction F of the paper 50. Then, the paper 50 on which the image data has been printed by the image forming unit 5 is discharged by the drive of the transport unit 7 and transported to the position of the image sensor 9. The image sensor 9 scans the image printed on the paper 50 multiple times along the main scanning direction S. The data of the color adjustment chart image read by the image sensor 9 is sent to the control unit 10 and used for color adjustment.

[0020] Furthermore, as one of the methods for adjusting the image forming apparatus 1, a position adjustment method is carried out. The image sensor 9 can read the color adjustment chart image T printed on the paper 50 by the image forming unit 5, as well as the marker images 71-74 (see FIG. 25) of the position adjustment chart printed on the paper 50. The marker images 71-74 of the position adjustment chart are cross-shaped and printed at predetermined positions near the four corners of the paper 50, and the printed positions in the X and Y directions can be measured from the center point where the images intersect. Then, like the color adjustment chart image, the data of the marker images 71-74 read by the image sensor 9 is sent to the control unit 10 and used for position adjustment.

[0021] The control unit 10 includes a position adjustment unit 3a and a color adjustment unit 3b. The position adjustment unit 3a adjusts the position of the print position according to a procedure for adjusting the print position. That is, the control unit 10 reads the position of the paper 50 conveyed by the conveyance unit 7 using the image sensor 9, and causes the position adjustment unit 3a to adjust the position of the print position based on the position information of the paper 50 that has been read. The control unit 10 causes the image forming unit 5 to print on paper 50 the image of the image data whose position has been adjusted or the image data of the color adjustment chart image. Furthermore, the control unit 10 performs color adjustment using the color adjustment unit 3b. When performing color adjustment, a color adjustment chart image printed by the image forming unit 5 is used. The adjustment method for the image forming device is performed using an adjustment procedure that combines a procedure for position adjustment using the position adjustment unit 3a and a procedure for color adjustment using the color adjustment unit 3b. 2 is a block diagram showing the control unit 10 of the image forming apparatus 1 and components connected to the control unit 10. The components include the touch panel display 4, the image sensor 9, the image forming unit 5, and the paper discrimination unit 8, which is a sensor mounted on the paper feed tray unit 6.

[0022] 2, a network interface 101 and an HDD / SSD 102 may be connected to the control unit 10. A USB interface 103 and a serial interface 104 may also be connected to the control unit 10. A ROM (Read Only Memory) 105 or a RAM (Random Access Memory) 106 may also be connected to the control unit 10. In the drawings, the interface is referred to as "I / F."

[0023] As shown in FIG. 2, the control unit 10 of the image forming apparatus 1 of the first embodiment has a plurality of CPUs (Central Processing Units) 10a to 10d as controllers. The CPUs 10a to 10d read out programs corresponding to the processing contents from the ROM 105 and load them into the RAM .

[0024] Then, CPUs 10a to 10d cause the loaded program to work in conjunction with various data stored in a storage unit such as RAM 106, HDD / SSD 102, or external storage. The external storage may be HDD / SSD 102, USB interface 103, or another device connected to serial interface 104. Control unit 10 controls image forming unit 5, paper feed tray unit 6, conveying unit 7, and image sensor 9 of image forming apparatus 1 based on processing by CPUs 10a to 10d.

[0025] The image processing unit 12 of the first embodiment performs gradation correction based on gradation correction data (for example, a gradation correction table LUT) stored in a storage unit such as an HDD. The image processing unit 12 performs various correction processes such as color correction and shading correction, compression, etc. on the input image data in addition to setting the print range and gradation correction.

[0026] The control unit 10 sends the image data processed by the image processing unit 12 to the image forming unit 5, and transfers the Y (yellow), M (magenta), C (cyan), and K (black) components using color toners. The image forming unit 5 is provided with an exposure device for each of the Y, M, C, and K components. Each exposure device is composed of a semiconductor laser and irradiates each photosensitive drum with laser light corresponding to the image of that color component. Positive charges generated in the charge generation layer of the photosensitive drum are transported to the surface and neutralized by surface charges (negative charges). An electrostatic latent image of each color component is formed on the surface of the photosensitive drum due to the potential difference with the surrounding area. The developing device forms a toner image by adhering toner of each color component to the surface of the photosensitive drum. The toner image is formed by visualizing the electrostatic latent image and is transferred to paper 50, which is being transported by transport unit 7, via an intermediate transfer belt (not shown). The toner images transferred onto the surface of paper 50 are superimposed to form a printed image with adjusted printing range, color, and gradation.

[0027] The paper feed tray section 6 has a plurality of paper feed trays 6a to 6d for respectively storing a plurality of types of paper 50 of different sizes and orientations. The paper feed trays 6a to 6d store paper 50 of different sizes and orientations, and paper discrimination sensors 8a to 8d of the paper discrimination section 8 discriminate the size and orientation of the paper 50 stored therein.

[0028] Then, the control unit 10 controls the driving of the conveying unit 7 as necessary to convey the paper 50 stocked in any one of the paper feed trays 6a to 6d to the image forming unit 5. The image forming unit 5 prints an image in the desired layout, color, and gradation on the paper 50. The paper 50 with the printed image is then stopped by the conveying unit 7 at or passes through an area where the image sensor 9 is provided, and is then conveyed to the paper output tray unit 11 provided outside the image forming apparatus 1.

[0029] Furthermore, the control unit 10 adjusts the positions of the marker images 71 to 74 (see FIG. 25: hereinafter also referred to as markers) by using the image sensor 9 to read the marker images 71 to 74 from the paper 50 on which the marker images 71 to 74 have been printed in advance by the image forming unit 5. The control unit 10 is configured to adjust the position of the printing range before printing the color adjustment chart image. For example, a conventional method is known in which color adjustment patches with marker images 71-74 are printed and the positions of the marker images 71-74 are detected simultaneously with reading the color adjustment. On the other hand, the color adjustment process of the present invention reliably positions all of the marker images 71-74 on the scanning lines. Therefore, the image forming device 1 can read the marker images 71-74 more accurately than conventional color adjustment, enabling highly accurate color adjustment.

[0030] As shown in FIG. 3, in the adjustment method for an image forming apparatus according to the first embodiment, color adjustment is performed after position adjustment is performed. First, when the control unit 10 of the image forming device 1 starts processing, in step (procedure) S1, it drives the conveying unit 7 to convey any one of the sheets 51 to 54 stored in each of the sheet feed trays 6a to 6d of the sheet feed tray unit 6 to the position of the image forming unit 5 as a sheet for position adjustment. In step S2, the control unit 10 controls the driving of the image forming unit 5 to print the marker images 71 to 74 shown in FIG. 25 on the conveyed paper by a method for printing marker images. In step S3, the marker images 71 to 74 on the paper 51 transported by the transport unit 7 to the position of the image sensor 9 shown in FIG. 1 are read by the image sensor 9 according to a procedure for reading images (scanning).

[0031] In step S4, based on the data of the marker images 71-74 sent from the image sensor 9, the control unit 10 adjusts the position of the color adjustment chart image on the paper to be printed next to the paper 51 on which the marker images 71-74 were read. In step S5, the control unit 10 drives and controls the image forming unit 5 to print a color adjustment chart image including the patches on the next sheet 53. At this time, the procedure for printing the image is such that, as shown on the sheet 53 in FIG. 4, 9 patches in the Y direction and 10 patches in the X direction, a total of 90 patches with different colors and gradations, are grouped together to print the color adjustment chart image 63. The paper 53 on which the color adjustment chart image has been printed is transported by the transport unit 7 from the image forming apparatus 1 to the paper discharge tray unit 11, whereupon the process ends.

[0032] In step S6, the image sensor 9 reads the patches of the color adjustment chart image 63 printed on the paper 53 that has been conveyed out. Then, in step S 4 , the control unit 10 performs color adjustment of the image formed by the image forming unit 5 based on the data of the color adjustment chart image 63 sent from the image sensor 9 .

[0033] As a result, even if the color adjustment chart image has a large number of patches, the image forming apparatus 1 of the first embodiment prints all of the patches together on one sheet of paper 53. This makes it possible to reduce the number of times the color adjustment chart image is read. In this way, even if the color adjustment chart image is made smaller and the density is increased, the patches arranged in the correct desired positions can be reliably read by the image sensor 9. Therefore, it is possible to reduce erroneous measurements of the color adjustment chart image used for color adjustment. Therefore, the image forming apparatus 1 can perform high-resolution color adjustment in a short time while saving the amount of paper 53 used to print the color adjustment chart image by one sheet.

[0034] Furthermore, the position of the color adjustment chart image is accurately adjusted using a plurality of cross marker images 71 to 74 printed near the four corners of the paper 50. Therefore, even if the patches that make up the color adjustment chart image are made smaller and the density is increased, erroneous measurements can be reduced. Furthermore, the image sensor 9 can scan while omitting the margins of the paper on which the cross marker images 71 to 74 are not printed. Therefore, the image forming apparatus of the first embodiment can reduce the reading time and adjustment time, thereby further improving the adjustment efficiency.

[0035] 5 is a diagram illustrating color adjustment performed by the control unit 10 of the image forming apparatus 1 of the second embodiment. Note that the same or equivalent parts as those of the image forming apparatus 1 of the first embodiment will be described with the same reference numerals.

[0036] The flowchart shown in FIG. 5 explains the control of color adjustment using the image forming apparatus 1 of the second embodiment. When an instruction to print a color adjustment chart is given in step S11, the control unit 10 first performs a process in step S12 in which the position adjustment unit 3a shown in FIG. 2 adjusts the position of the marker image output by the image forming unit 5, similar to steps S2 to S6 in FIG. 3. In the next step S13, based on the result of the position adjustment, the control unit 10 instructs the image forming unit 5 to print a color adjustment chart image, and causes the image forming unit 5 to print the color adjustment chart image. In step S14, color measurement is performed by a sensor using the color adjustment chart image, and color adjustment is performed as color correction processing. Then, in step S15, the paper 50 on which the color adjustment chart image has been printed is conveyed by the conveying unit 7 and ejected.

[0037] In this way, in the image forming apparatus 1 of the second embodiment, an instruction to print a color adjustment chart is given via the operation unit 4b of the touch panel display 4, or via the network interface 101, the HDD / SSD 102, the USB interface 103, or the serial interface 104. That is, the position adjustment is first performed using the paper on which the marker images 71 to 74 are printed, and after the position adjustment is performed, the color adjustment is then performed.

[0038] FIG. 6 shows a sheet 54 on which a color adjustment chart image 64 used in the image forming apparatus 1 is printed. The orientation of the paper 54 in the X and Y directions relative to the transport direction F of the paper 53 shown in Fig. 4 is changed by 90 degrees. As a result, the color adjustment chart image 64 printed on the paper 54 can be printed with 11 patches in the Y direction that coincides with the transport direction F and 13 patches in the X direction, for a total of 141 patches with different colors and gradations.

[0039] Color adjustment using the paper 54 configured in this manner can increase the number of patches compared to color adjustment processed by the image forming apparatus 1 of the first embodiment. Therefore, the image forming apparatus 1 of the second embodiment can perform color adjustment with even higher precision. Furthermore, when the paper 54 is transported at the same transport speed as the paper 53, the time required to read the entire color adjustment chart image 64 is reduced. At this time, the position of the color adjustment chart image is accurately adjusted using the marker images 71 to 74. Therefore, even if the color adjustment chart image is made smaller and the density is increased, erroneous measurements are reduced and high-resolution color adjustment can always be performed in a short time. The other configurations and effects are the same as those of the image forming apparatus 1 of the first embodiment, so a description thereof will be omitted.

[0040] 7 illustrates the color adjustment process performed by the control unit 10 of the image forming apparatus 1 of the third embodiment. Note that the same or equivalent parts as those of the image forming apparatus 1 of the first embodiment will be described with the same reference numerals. First, in step S21, when processing starts, an instruction is given to print (also referred to as a job) on paper, which is a printed matter other than the marker images 71-74 or the color adjustment chart image, etc. Generally, in a job, the control unit 10 sends print data for an image or text (document) to the image forming unit 5, and the desired print is performed on paper by the image forming unit 5. At this time, if the color adjustment precision is selected from high resolution, medium resolution, or low resolution, an instruction is given to print the color adjustment chart image 63 for color adjustment in step S22. In step S23, position adjustment processing is performed only if the instruction in step S21 is high resolution. Next, in step S24, based on the result of the position adjustment, the control unit 10 instructs the image forming unit 5 to print a color adjustment chart image, and causes the image forming unit 5 to print the color adjustment chart image. In step S25, color measurement is performed by the image sensor 9 using the color adjustment chart image, and color adjustment is performed as color correction processing. Then, in step S26, the paper on which the color adjustment chart image has been printed is transported and ejected by the transport unit 7, and the processing ends. Other configurations and effects are the same as those of the image forming apparatus 1 of the first embodiment, and therefore description thereof will be omitted.

[0041] 8 is a diagram illustrating the color adjustment process performed by the control unit 10 of the image forming apparatus 1 of the fourth embodiment. Note that the same or equivalent parts as those of the image forming apparatus 1 of the first embodiment will be described with the same reference numerals. The control unit 10 of the fourth embodiment determines whether to perform position adjustment based on the printing state of the image forming apparatus 1. Here, the state of the image forming apparatus 1 is such that whether or not position adjustment has been performed on the paper in the paper feed tray 6 that is the target of job printing within one day from now is used as a criterion for determining whether position adjustment should be performed. First, in step S31, when processing starts, an instruction is given to the image forming unit 5 to print a color adjustment chart, and in step S32, it is determined based on the printing history stored in a memory unit such as RAM 106 whether position adjustment has been performed on the paper in the target paper feed tray unit 6 within the past day.

[0042] If the position adjustment has been performed within one day, the process proceeds to the next step S34 (Yes in step S32). In step S34, based on the result of the position adjustment, the control unit 10 instructs the image forming unit 5 to print a color adjustment chart image, and causes the image forming unit 5 to print the color adjustment chart image. In step S35, color measurement is performed by the image sensor 9 using the color adjustment chart image, and color adjustment is performed as color correction processing. Then, in step S36, the paper on which the color adjustment chart image has been printed is transported and ejected by the transport unit 7, and the processing ends.

[0043] If the position adjustment has not been performed within one day, the process proceeds to step S33 (No in step S32). In step S33, the position adjustment process is performed, and then the process proceeds from step S34 to step S36. Thus, in the fourth embodiment, the memory unit of the control unit 10 stores the time when the previous image position adjustment was performed. The memory unit of the fourth embodiment stores the position adjustment of the paper feed tray 6a to 6d corresponding to any of the sheets 51 to 54 on which the color adjustment chart image is printed, among the multiple paper feed trays 6a to 6d. If the time or number of sheets since the previous position adjustment is within a threshold value, in this case within one day, the color adjustment chart image is output without image position adjustment.

[0044] The control unit 10 determines whether it is within a period in which the positional accuracy of printing the color adjustment chart image will not decrease based on the state of the printing history, and performs positional adjustment only if necessary. Also, if it is determined from the history that position adjustment is unnecessary immediately after position adjustment has been performed, color adjustment can be performed immediately without performing position adjustment.

[0045] This further reduces the reading time and adjustment time, thereby improving the adjustment efficiency. Other configurations and effects are the same as those of the image forming apparatus 1 of the first embodiment, and therefore description thereof will be omitted.

[0046] 9 explains the color adjustment process performed by the control unit 10 of the image forming apparatus 1 of the fifth embodiment. Note that the same or equivalent parts as those of the image forming apparatus 1 of the first to fourth embodiments will be described with the same reference numerals. The control unit 10 of the fifth embodiment determines whether or not to perform position adjustment based on the printing status of the image forming apparatus 1. Here, the printing status is determined based on whether or not the number of printed sheets in the history exceeds a specified number, and if color adjustment is to be performed, the color adjustment is performed after the position adjustment. First, when a job is started in step S41, if the number of prints of the job being executed exceeds a specified number, the control unit 10 starts color adjustment processing in step S42. In step S43, a position adjustment process is performed. Then, in step S44, based on the result of the position adjustment, the control unit 10 instructs the image forming unit 5 to print a color adjustment chart image, and causes the image forming unit 5 to print the color adjustment chart image. In step S45, color measurement is performed by the image sensor 9 using the color adjustment chart image, and color adjustment is performed as color correction processing. Then, in step S26, the paper on which the color adjustment chart image T is printed is transported and ejected by the transport unit 7, and the processing ends. Other configurations and effects are the same as those of the image forming apparatus 1 of the first to fourth embodiments, and therefore description thereof will be omitted.

[0047] 10 is a diagram illustrating the color adjustment process performed by the control unit 10 of the image forming apparatus 1 of the sixth embodiment. Note that the same or equivalent parts as those of the image forming apparatus 1 of the first to fifth embodiments will be described with the same reference numerals. First, in step S51, the start of a job is instructed, and in step S52, the page to be printed by the job is instructed to be high-definition, high-quality, or photo printing. In this case, it is determined whether color adjustment has been performed within a specified period. If color adjustment has been performed (Yes in step S52), the process proceeds to the next step S58, where the page is printed. If color adjustment has not been performed (No in step S52), the process proceeds to step S53.

[0048] Next, in step S53, it is determined whether the position adjustment of the target tray has been performed within the specified state of the image forming apparatus 1. Here, for example, the print state is determined based on whether the number of prints in the print history exceeds a specified number. If color adjustment is to be performed, the color adjustment is performed after the position adjustment. In addition, in printing control, there is an image forming apparatus 1 that is recommended to perform position adjustment when paper is set in the paper feed tray. Furthermore, in such an image forming apparatus 1, there are cases where the number of sheets used for printing has decreased to the number that requires paper to be set in the paper feed tray section 6. In such cases, this may be used as a criterion for determining that the specified number has been exceeded and position adjustment is required.

[0049] Therefore, in step S53, when the control unit 10 determines whether the specified number has been exceeded based on the printing history previously stored in the memory unit, it determines whether position adjustment is necessary based on the time when position adjustment was performed on the target paper feed tray 6a to 6d. If the position adjustment of the target paper feed trays 6a-6d corresponding to the paper sheets 51-54 for which the job is to be performed has not been performed within the specified range (No in step S53), the process proceeds to step S54. After the position adjustment process is performed in step S54, the process proceeds to step S55. If the position adjustment has been performed within the specified range (Yes in step S53), the process proceeds to step S55 without performing the position adjustment process.

[0050] In step S55, the control unit 10 instructs the image forming unit 5 to print a color adjustment chart. The image forming unit 5 prints the color adjustment chart image on paper. At this time, if the paper discrimination unit 8 determines that there are multiple paper feed trays containing paper of the same paper type based on the paper type information of the paper stored in the paper feed tray unit 6, the control unit 10 prints a color adjustment chart image on paper in any of the paper feed trays 6a to 6d whose position has been adjusted. In step S56, color measurement is performed by the image sensor 9 using the color adjustment chart image, and color adjustment is performed as color correction processing. Then, in step S57, the paper on which the color adjustment chart image has been printed is transported by the transport unit 7 and ejected.

[0051] Once the page of the job is printed in step S58, a determination is made in step S59 as to whether the printed page is the last page of the job. If the printed page is the last page of the job (Yes in step S59), the process proceeds to step S60 to execute the job. If the last page is not there (No in step S59), the process returns to step S52, where it is again determined whether the page to be printed by the job is high definition, high image quality, or photo printing and color adjustment has not been performed.

[0052] In this way, when printing on paper 60, the control unit 10 performs position adjustment based on whether or not color adjustment is performed within the preset specifications when high-quality printing settings such as high definition / high quality / photo printing are set. For example, even when position adjustment is required for high-resolution, high-quality printing such as photographs, position adjustment may be performed periodically within the specified range or within the number of sheets that does not require adjustment. In such cases, position adjustment or color adjustment can be omitted, further reducing the number of sheets, scanning time, and adjustment time. This further improves the adjustment efficiency of the image forming apparatus 1.

[0053] Furthermore, the paper discrimination unit 8 prints a color adjustment chart image on paper stocked in the position-adjusted paper feed trays 6a to 6d based on the paper type information of the paper detected by the paper discrimination sensors 8a to 8d. In addition, when the same type of paper is stocked in multiple paper feed trays 6a to 6d after being adjusted in position, the color adjustment chart image can also be printed by giving priority to paper whose width in the main scanning direction S is wider along the X direction. In this case, the image forming apparatus 1 can print a large number of patches arranged in the main scanning direction S. Also, more patches can be read in one scan by the image sensor 9. This reduces the reading time.

[0054] Furthermore, it is possible to calculate the position accuracy error from the position adjustment timing and determine the priority between performing color adjustment by changing the patch size and spacing, and performing position adjustment first and then performing color adjustment. Also, the width in the main scanning direction S may be used as a criterion for determination. In this case, priority is given to paper that is narrow in the main scanning direction S along the Y direction, thereby reducing the risk of the paper tearing or becoming worn. Other configurations and effects are the same as those of the image forming apparatus 1 of the first embodiment, and therefore description thereof will be omitted.

[0055] 11 is a diagram illustrating color adjustment performed by the control unit 10 of the image forming apparatus 1 of the seventh embodiment. Note that the same or equivalent parts as those of the image forming apparatuses 1 of the first to sixth embodiments will be described with the same reference numerals. In the seventh embodiment, the patch sizes of the color adjustment chart images 65 to 67 are changed according to the conveying speed of the conveying unit 7, as shown in FIGS. First, in step S61, when processing starts, an instruction to print a color adjustment chart is given to the image forming unit 5. In step S62, the control unit 10 causes the position adjustment unit 3a to output marker image data to the image forming unit 5, as in steps S2 to S6 of Figure 3, and print it on the position adjustment paper 520, thereby performing the position adjustment process.

[0056] At this time, in step S63, the patch size and interval are changed according to the speed at which the paper is being conveyed by the conveyance unit 7 during the process. The speed at which the paper is conveyed by the conveying unit 7 differs depending on the performance of the image forming unit 5. A color adjustment chart image 65 having a patch size and small intervals that is used for an image forming unit 5 with a relatively slow transport speed is printed on a paper 55 shown in FIG. Also, a color adjustment chart image 66 is printed on the paper 56 shown in FIG. 13, in which the patch size and intervals used for the image forming unit 5 with a medium transport speed are set to be medium. Then, on the paper 57 shown in FIG. 14, a color adjustment chart image 67 is printed in which the patch size and intervals are set large so as not to cause erroneous measurements even when the image forming unit 5 is operated at a relatively fast transport speed.

[0057] Returning to step S64 in FIG. 11, the control unit 10 instructs the image forming unit 5 to form an image of any one of these color adjustment chart images 65 to 67, and the image forming unit 5 prints any one of the color adjustment chart images 65 to 67 on paper. In step S65, color measurement and color adjustment as color correction processing are performed by the image sensor 9 using any of the color adjustment chart images 65 to 67 printed on the sheets 55 to 57. Then, in step S66, the sheets 55 to 57 that have been color-measured are transported and ejected by the transport unit 7, and the processing ends.

[0058] As a result, the image forming apparatus 1 of the seventh embodiment, in addition to the effects of the image forming apparatuses 1 of the first to sixth embodiments, can further measure the color in the main scanning direction S using the image sensor 9 while transporting the paper according to the transport speed of each image forming unit 5 without stopping the paper. This allows high-definition color adjustment to be performed with the number of sheets, reading time, and adjustment time that provide the most efficient adjustment in accordance with the performance of the conveyance speed of the image forming unit 5. Other configurations and effects are the same as those of the image forming apparatus 1 of the first to sixth embodiments, and therefore description thereof will be omitted.

[0059] 15 is a diagram illustrating color adjustment performed by the control unit 10 of the image forming apparatus 1 of the eighth embodiment. Note that the same or equivalent parts as those of the image forming apparatus 1 of the first embodiment will be described with the same reference numerals. In the eighth embodiment, the user issues an instruction to print a color adjustment chart (step S71), which causes the control unit 10 to carry out a process of adjusting the position using the marker images 71 to 74 (step S72). In step S73, the control unit 10 performs color adjustment using a sheet of paper that is long in the main scanning direction S, among the sheets 51 to 54 stocked in the paper feed trays 6a to 6d. For color adjustment, the control unit 10 instructs the image forming unit 5 to print a color adjustment chart image 64 for color adjustment corresponding to the long sheet of paper. At this time, the control unit 10 causes the image forming unit 5 to print the color adjustment chart image 64 based on the result of the position adjustment.

[0060] In step S74, the control unit 10 performs color measurement using the color adjustment chart image with the image sensor 9. Then, color adjustment is performed as color correction processing. In step S75, the paper on which the color adjustment chart image 64 is printed is transported by the transport unit 7 and discharged. This reduces the time required to read the color adjustment chart image, allowing high-resolution color adjustment to be performed in a short time. Other configurations and effects are the same as those of the image forming apparatus 1 of the first to sixth embodiments, and therefore description thereof will be omitted.

[0061] 15 is a diagram illustrating the color adjustment process performed by the control unit 10 of the image forming apparatus 1 of the eighth embodiment. Note that the same or equivalent parts as those of the image forming apparatus 1 of the first embodiment will be described with the same reference numerals. When the image forming apparatus 1 starts processing, an instruction to print a color adjustment chart is given in step S71, and the control unit 10 then performs processing to print marker images 71 to 74 and adjust their positions in step S72. In step S73, color adjustment is performed using paper 58 that is long in the main scanning direction S, as shown in Fig. 16, from among the papers stocked in paper feed trays 6a to 6d. In color adjustment, first, the control unit 10 prints a color adjustment chart image 68 that corresponds to the long paper 58. 14, which has a shorter main scanning direction, more patches can be arranged on the paper 58 in the main scanning direction S of the color adjustment chart image 68. At this time, based on the result of the position adjustment, the control unit 10 causes the image forming unit 5 to print the color adjustment chart image 68.

[0062] 16, a sheet of paper 58 whose X direction is aligned with the main scanning direction S can read a large number of patches with a single scanning line 200. In this case, 12 patches can be read in the same reading time. For comparison, if the orientation of the same sheet of paper 58 is changed by 90 degrees so that the Y direction is aligned with the main scanning direction S, the number of patches that can be read with a single scanning line 200 will be about 9. The control unit 10 determines that the same paper 58, but with the X direction aligned with the main scanning direction S, is stocked in one of the paper feed trays 6a to 6d of the paper feed tray unit 6 by the paper discrimination unit 8. As a result, the stocked paper 58 is transported by the transport unit 7 with the Y direction aligned with the transport direction F, and the color adjustment chart image 68 is printed by the image forming unit 5.

[0063] In step S74, the image sensor 9 performs color measurement using the color adjustment chart image 68. A relatively large number of patches can be read with a small number of reads on the paper 58 that is long in the main scanning direction S. Furthermore, the Y direction of the paper 58 is the transport direction F, so the transport distance can be reduced. Furthermore, in step S74, color adjustment is performed as a color correction process. Then, in step S75, the paper 58 after color adjustment is transported by the transport unit 7 and ejected, and the process ends. Therefore, the time required to read the color adjustment chart image is shortened, and more patches can be read in the same amount of time. This allows the image forming apparatus 1 to perform high-resolution color adjustment in a short amount of time. Other configurations and effects are the same as those of the image forming apparatus 1 of the first to seventh embodiments, and therefore description thereof will be omitted.

[0064] 17 is a diagram illustrating the color adjustment process performed by the control unit 10 of the image forming apparatus 1 of the ninth embodiment. Note that the same or equivalent parts as those of the image forming apparatus 1 of the first embodiment will be described with the same reference numerals. In the ninth embodiment, when processing of the image forming apparatus 1 is started, an instruction to print a color adjustment chart is given in step S81, and then in step S82 the control unit 10 performs processing to adjust the position using the marker image M. Normally, as in step S83, color adjustment chart images 69 and 610 may be formed on the same sheets of paper 59 and 510 that are long in the transport direction F shown in FIG.

[0065] In step S84 of the present invention, as shown in FIG. 19, paper 511, which is the same size as paper 59, 510 and is stored in one of the paper feed trays 6a to 6d along the Y direction in the transport direction F, is transported to the image forming unit 5, and a color adjustment chart image 611 is printed on it. This allows the number of patches read in one scan to be increased compared to the number printed on two sheets of paper 59 or 510 shown in Figure 18. This further reduces the reading time and adjustment time, improving adjustment efficiency. Furthermore, in step S85, color adjustment is performed as color measurement and color correction processing. Then, in step S86, the paper 58 etc. for which color adjustment has been completed is conveyed and ejected by the conveying unit 7, and the processing ends.

[0066] 20 is a diagram illustrating the color adjustment process performed by the control unit 10 of the image forming apparatus 1 of the tenth embodiment. Note that the same or equivalent parts as those of the image forming apparatus 1 of the first embodiment will be described with the same reference numerals. In the tenth embodiment, when the control unit 10 starts processing, an instruction to print a color adjustment chart is given in step S91, and then in step S92 the control unit 10 determines whether the patch size of the color adjustment chart image is equal to or less than the specified 15 mm and the patch spacing is equal to or less than the specified 3 mm.

[0067] If the patch size of the color adjustment chart image is equal to or smaller than the specified 15 mm and the patch interval is equal to or smaller than the specified 3 mm (Yes in step S91), the control unit 10 proceeds to step S93 to perform position adjustment processing, and then proceeds to step S94. If the patch size of the color adjustment chart image is not equal to or less than the specified 15 mm and the patch interval is not equal to or less than the specified 3 mm (No in step S91), the process proceeds to step S94. In step S94, the control unit 10 instructs the image forming unit 5 to form an image of the color adjustment chart image, and the image forming unit 5 prints the color adjustment chart image on paper. In step S95, the image sensor 9 measures the color using the printed color adjustment chart image and performs color adjustment as a color correction process. Then, in step S96, the paper that has been measured is transported and ejected by the transport unit 7, and the process ends.

[0068] In this way, when printing on paper, if the patch size or patch spacing of the chart in the color adjustment chart image is below a threshold value, the control unit 10 of the tenth embodiment performs position adjustment and then prints the color adjustment chart image to perform color adjustment. This makes it possible to reduce erroneous measurements and further improve the accuracy of color adjustment. Other configurations and effects are the same as those of the image forming apparatus 1 of the first to ninth embodiments, and therefore description thereof will be omitted.

[0069] 21 is a diagram illustrating the color adjustment process performed by the control unit 10 of the image forming apparatus 1 of the eleventh embodiment. Note that the same or equivalent parts as those of the image forming apparatus 1 of the first embodiment will be described with the same reference numerals. In the eleventh embodiment, when the control unit 10 starts processing and an instruction to print a color adjustment chart is issued in step S101, the control unit 10 determines in step S102 whether the position adjustment process for any of the paper feed trays 6a to 6d that outputs the color adjustment chart image has been performed within one day.

[0070] If the position adjustment process has not been performed within one day, which is the threshold value of the elapsed time (No in step S102), the process proceeds to step S103, where the position adjustment process is performed, and then the process proceeds to step S104. If the position adjustment process was performed within one day (Yes in step S102), the process proceeds to step S104. In step S104, the control unit 10 instructs the image forming unit 5 to form an image of the color adjustment chart image, and the image forming unit 5 prints the color adjustment chart image on paper. In step S105, the image sensor 9 measures the color using the printed color adjustment chart image and performs color adjustment as a color correction process. Then, in step S96, the paper that has been measured is transported and ejected by the transport unit 7, and the process ends.

[0071] The control unit 10 of the eleventh embodiment stores in a memory unit the time when the previous image position adjustment was performed in the paper feed tray of the paper on which the color adjustment chart image is printed. The control unit 10 outputs the color adjustment chart image without adjusting the image position if the time since the previous position adjustment was performed, which is within one day in this case. Note that if the number of sheets printed by the job is within a threshold, the color adjustment chart image may be output without adjusting the image position. As a result, for example, if the image forming apparatus 1 has had a position adjustment within the past day, it is determined that no position adjustment is to be performed, but if it has been more than a day, it is determined that position adjustment is to be performed. Therefore, it is possible to further omit excessive position adjustment processing and shorten the adjustment time. Other configurations and effects are the same as those of the image forming apparatus 1 of the first to tenth embodiments, and therefore description thereof will be omitted.

[0072] 22 is a diagram illustrating the color adjustment process performed by the control unit 10 of the image forming apparatus 1 of the twelfth embodiment. Note that the same or equivalent parts as those of the image forming apparatus 1 of the first embodiment will be described with the same reference numerals. In the twelfth embodiment, when the control unit 10 starts processing, an instruction to print a color adjustment chart is given in step S111, and then in step S112, the control unit 10 determines whether or not the position adjustment process for at least one of the multiple paper feed trays 6a to 6d that can be color adjusted has been performed within one day.

[0073] If the position adjustment process for at least one of the paper feed trays 6a to 6d has not been performed within one day (No in step S112), the process proceeds to step S113, where the position adjustment process is performed, and then the process proceeds to step S114. If the position adjustment process for at least one of the paper feed trays 6a to 6d has been performed within the last day (Yes in step S112), the process proceeds to step S114. In step S114, the control unit 10 instructs the image forming unit 5 to form an image of the color adjustment chart, and the image forming unit 5 prints the color adjustment chart image on paper that is stocked in any of the paper feed trays 6a to 6d within one day after the position adjustment process was performed. In step S115, the printed color adjustment chart image is used to perform color measurement and color adjustment, which is a color correction process, by the image sensor 9. Then, in step S116, the paper used for color measurement is transported and ejected by the transport unit 7, and the process ends.

[0074] In this way, when there are multiple paper feed trays containing the same type of paper, the control unit 10 of the twelfth embodiment prints a color adjustment chart image from any of the paper feed trays whose last image position adjustment was performed within the threshold value. This allows the color adjustment chart image to be printed on paper stored in the paper feed tray for which position adjustment has already been performed, thereby further shortening the reading time and adjustment time and improving adjustment efficiency. Other configurations and effects are the same as those of the image forming apparatus 1 of the first to eleventh embodiments, and therefore description thereof will be omitted.

[0075] 23 is a diagram illustrating the color adjustment process performed by the control unit 10 of the image forming apparatus 1 of the thirteenth embodiment. Note that the same or equivalent parts as those of the image forming apparatus 1 of the first embodiment will be described with the same reference numerals. In the thirteenth embodiment, when the control unit 10 starts processing, an instruction to print a color adjustment chart image is given in step S121, and in the case of normal color adjustment, the control unit 10 prints color adjustment chart images 612 to 614 shown in FIG. 24 on three sheets of paper 512 to 514 as in step S122, thereby performing color adjustment.

[0076] 25, the control unit 10 of the thirteenth embodiment prints marker images 71 to 74 near the four corners of the position adjustment paper 520. Then, in step S123, the position adjustment process is performed using the position adjustment paper 520 on which the marker images 71 to 74 are printed. After the position adjustment process is performed, the process proceeds to step S124. In step S124, the control unit 10 instructs the image forming unit 5 to form an image of the color adjustment chart image. Then, the image forming unit 5 prints the color adjustment chart image 615 shown in Fig. 25 on a sheet of paper 515. The color adjustment chart image 615 is printed on one sheet of paper 515 with three sheets of color adjustment chart images 612 to 614 grouped together. In step S125, color measurement and color adjustment as color correction processing are performed by the image sensor 9 using the color adjustment chart image 615 printed on the paper 515. Then, in step S126, the paper 515 used for color measurement is transported and ejected by the transport unit 7, and the processing ends.

[0077] For example, normal color adjustment uses three sheets of paper 512-514 shown in Fig. 24. The image forming apparatus 1 of the thirteenth embodiment uses a position adjustment sheet 520 on which marker images 71-74 shown in Fig. 25 are printed, and combines three sheets of color adjustment chart images 612-614 shown in Fig. 25 onto one sheet 515. Then, by reducing the size of the patches and increasing the density, the number of sheets of paper 515 on which the color adjustment chart images 615 are printed can be reduced. This makes it possible to reduce the number of sheets of paper used for color adjustment and further improve the efficiency of adjustment. The other configurations and effects are the same as those of the image forming apparatus 1 of the first to twelfth embodiments, so a description thereof will be omitted.

[0078] 26 is a diagram illustrating the color adjustment process performed by the control unit 10 of the image forming apparatus 1 of the fourteenth embodiment. Note that the same or equivalent parts as those of the image forming apparatus 1 of the first embodiment will be described with the same reference numerals. When the control unit 10 starts processing, an instruction to print a color adjustment chart image is given in step S131. For example, as in step S132, the control unit 10 prints the color adjustment chart images 616 to 618 shown in FIG. 27 on three sheets of paper 516 to 518, respectively, and performs normal color adjustment with the main scanning direction S aligned with the X direction.

[0079] When an instruction to print a color adjustment chart image T is given in step S131, the image forming apparatus 1 of the fourteenth embodiment first prints marker images 71 to 74 near the four corners of the position adjustment paper 520 as shown in Fig. 28. Then, in step S133, a position adjustment process is performed using the position adjustment paper 520 on which the marker images 71 to 74 are printed. After the position adjustment process is performed, the process proceeds to step S134. In step S134, the control unit 10 instructs the image forming unit 5 to form an image of the color adjustment chart image. At this time, the image forming unit 5 prints a color adjustment chart image 619 shown in Fig. 28 on a sheet of paper 519. The color adjustment chart image 619 is printed on one sheet of paper 519 with three sheets of color adjustment chart images 612 to 614 grouped together. In step S135, the image sensor 9 reads the color adjustment chart image 619 printed on the paper 519, and color measurement and color adjustment as color correction processing are performed by the color adjustment unit 3b of the control unit 10. Then, in step S126, the paper 519 used for color measurement is transported by the transport unit 7 and discharged to the paper discharge tray unit 11, and the processing ends.

[0080] In this way, in the image forming apparatus 1 of the fourteenth embodiment, the paper 519 used for color adjustment and the position adjustment paper 520 are transported with the Y direction aligned with the transport direction F, and the main scanning direction S coincides with the X direction. Therefore, the color adjustment of the fourteenth embodiment can be processed even faster in a shorter time than the color adjustment of the thirteenth embodiment. The other configurations and effects are the same as those of the image forming apparatus 1 of the thirteenth embodiment, so a description thereof will be omitted.

[0081] As described above, the image forming apparatus 1 of the present invention includes an image forming unit 5 that prints a color adjustment chart image used for color adjustment on transported paper, an image sensor 9 that reads the color adjustment chart image printed on the paper, and a control unit 10 that performs position adjustment to adjust the printing position of the color adjustment chart image from the position of the transported paper and performs color adjustment using the color adjustment chart image printed by the image forming unit 5.

[0082] In the image forming apparatus 1 and the image forming apparatus adjustment method of the present invention configured as described above, the number of times of reading can be reduced even if the number of patches in the color adjustment chart image is large. Specifically, the color adjustment chart image is adjusted to the correct position and printed accurately at the desired position on the paper. Therefore, even if the color adjustment chart image is made smaller and the density is increased, erroneous measurements can be reduced. Therefore, high-resolution color adjustment can be performed in a short time while saving paper used to print the color adjustment chart image.

[0083] The control unit 10 uses the image sensor 9 to read the marker images 71 to 74 from paper on which the marker images 71 to 74 have been printed in advance by the image forming unit 5, adjusts the positions, and then prints a color adjustment chart image after performing the position adjustment. The color adjustment chart image printed by the image forming unit 5 is accurately positioned using the marker images 71 to 74. Therefore, even if the color adjustment chart image is made smaller and the density is increased, erroneous measurements can be reduced. Therefore, the reading time and adjustment time can be shortened, and adjustment efficiency can be improved.

[0084] The control unit 10 is configured to be able to perform a plurality of types of color adjustment with different degrees of precision, and performs position adjustment when performing high-definition color adjustment. When performing high-precision color adjustment, the color adjustment is performed after performing position adjustment. Therefore, when high-precision color adjustment is not required, the color adjustment can be performed without performing position adjustment. This improves adjustment efficiency.

[0085] The control unit 10 determines whether or not to perform position adjustment based on the printing state. For example, it is determined whether or not position adjustment is to be performed based on the state of the print history whether or not it is within a period in which the position accuracy of printing will not decrease. If it is determined from the history that position adjustment is not necessary, color adjustment can be performed immediately without performing position adjustment. This further reduces the reading time and adjustment time, thereby improving the adjustment efficiency.

[0086] When executing a print job, the control unit 10 performs color adjustment after performing position adjustment. A print job is a general term for print commands to the image forming apparatus 1, and includes print data and print settings. Print data is data of a document to be printed, and may include various types of data such as image data, vector data, and text data. Specifically, print data may be PDL (Page Description Language) data or PDF (Portable Document Format) data. Print data may also be TIFF (Tagged Image File Format) data. Print settings are settings related to image formation on paper, and include various settings such as the number of pages, number of copies, paper type, selection of color or monochrome, and page layout. For example, if the printing status is determined based on whether the number of printed sheets in the history has exceeded a specified number and color adjustment is to be performed, the color adjustment is performed after position adjustment. In addition, there is an image forming apparatus 1 that is recommended to perform position adjustment when paper is set in the paper feed tray in the print control. In such an image forming apparatus 1, the number of sheets used for printing has decreased to the number of sheets that requires paper to be set in the paper feed tray, and the position adjustment is performed as it is considered to be necessary. For this reason, in this proposal, if printing of a color adjustment chart image is specified immediately after position adjustment, the color adjustment chart image is output without performing position adjustment. This makes it possible to avoid redundant and unnecessary position adjustment. Therefore, it is possible to further shorten the reading time and adjustment time and improve adjustment efficiency.

[0087] When printing on paper, if high-quality printing such as high definition / high quality / photo printing is set, the control unit 10 performs color adjustment after performing position adjustment. This allows position adjustment to be performed when high-definition / high-quality printing is required, such as high-quality printing of photographs, etc. Therefore, the number of sheets of paper, the reading time, and the adjustment time can be further reduced, improving the adjustment efficiency.

[0088] When printing on paper, the control unit 10 adjusts the position and changes the size and interval of the color adjustment patches in accordance with the transport speed of the paper on which printing is performed, thereby performing color adjustment. This allows color adjustment to be performed with the number of sheets, reading time, and adjustment time that provide the best adjustment efficiency in accordance with the performance of the conveyance speed.

[0089] When printing on paper, if there is paper of the same type as the paper to be printed on that has a long main scanning direction, the control unit 10 arranges more patches in the main scanning direction of the color adjustment chart image than paper with a short main scanning direction. This allows the number of patches read in one scan to be increased, thereby further shortening the read time and adjustment time and improving the adjustment efficiency.

[0090] When printing on paper, if there is paper of the same type as the paper being printed on but which is long in the main scanning direction, the control unit 10 changes the size interval of the patches of the color adjustment chart image to arrange more patches in the main scanning direction. This makes it possible to increase the number of patches that can be read in one scan, thereby further shortening the reading time and adjustment time and improving the adjustment efficiency.

[0091] When printing on paper, if the patch size or patch interval of the chart of the color adjustment chart image is below a threshold, the control unit 10 performs position adjustment before printing the chart and performs color adjustment. This makes it possible to reduce erroneous measurements and further improve the accuracy of color adjustment.

[0092] The control unit 10 stores the time when the previous image position adjustment was performed in the paper feed tray of the paper on which the color adjustment chart image is printed, and outputs the color adjustment chart image without performing image position adjustment if the time or number of sheets since the previous position adjustment is within a threshold value. As a result, for example, if the device status indicates that position adjustment has been performed within the past day, it is determined that position adjustment is not required, but if it has been more than a day, it is determined that position adjustment is required. Therefore, if color adjustment can be performed with even higher precision and position adjustment is not necessary, position adjustment can be omitted, thereby shortening the adjustment time.

[0093] When there are multiple paper feed trays containing the same type of paper, the control unit 10 prints the color adjustment chart image from any of the paper feed trays whose previous image position adjustment was performed within a threshold value. As a result, the color adjustment chart image is printed from the paper feed tray for which position adjustment has already been performed, thereby further shortening the reading time and adjustment time and improving adjustment efficiency.

[0094] The control unit 10 prints the color adjustment chart image by changing the patch size and patch interval based on the threshold value for the timing of position adjustment of the paper on which the color adjustment chart image T is output, or by adjusting the image position and then printing the color adjustment chart image with a predetermined patch size, or by printing the color adjustment chart image in a way that can save the number of sheets of paper. This can reduce the number of sheets of paper and improve the efficiency of adjustment.

[0095] The control unit 10 prints the color adjustment chart image by either printing the color adjustment chart image with the patch size and patch interval changed based on the threshold value of the timing of position adjustment of the paper on which the color adjustment chart image is output, or printing the color adjustment chart image with a predetermined patch size after adjusting the image position, whichever is shorter in time. This allows the color adjustment chart image to be printed in the shortest possible time. Because the paper position is adjusted before color adjustment, color adjustment can be performed correctly even if the patch density of the chart is increased.

[0096] Although the embodiments and their modifications of the present invention have been described above, these embodiments are merely illustrative and do not limit the technical scope of the present invention. The present invention can take various other embodiments, and various modifications such as omissions and substitutions can be made without departing from the spirit of the present invention. These embodiments and their modifications are included in the scope and spirit of the invention described in this specification, etc., and are included in the invention described in the claims and their equivalents.

[0097] For example, in the first embodiment, position adjustment is performed using a position adjustment paper 520 on which multiple cross marker images 71-74 are printed near the four corners of the paper. However, the position adjustment paper 520 used for position adjustment is not limited to this. For example, the marker images 71-74 do not have to be used as long as the print position on the paper can be identified. Also, figures or marks of other shapes may be printed instead of the cross marker images 71-74. In other words, the shape, number, and print position of the marker images 71-74 are not limited to those of the position adjustment paper 520 of the first embodiment, and any other shape may be used as long as it is possible to perform position adjustment to adjust the print position of the color adjustment chart image from the position of the transported paper. [Explanation of symbols]

[0098] 1. Image forming device 5. Image forming unit 9 Image Sensor 10 Control Unit 50 sheets 71~74 Marker images

Claims

1. an image forming unit that prints an image on the transported paper; an image sensor that reads the paper; and a control unit that adjusts the printing position on the paper by the image forming unit from the position of the image printed on the paper, and then performs color adjustment of the image forming unit using the chart printed by the image forming unit.

2. the image forming unit prints a marker on the paper; After the control unit adjusts the print position based on the position of the marker on the paper, the image forming unit prints a chart; The image forming apparatus according to claim 1 .

3. the control unit is capable of performing a plurality of types of color adjustment with different degrees of accuracy, When performing color adjustment with a predetermined accuracy, the print position is adjusted in advance.

3. The image forming apparatus according to claim 1.

4. the control unit determines whether to adjust the print position based on the printing state of the image forming unit.

2. The image forming apparatus according to claim 1.

5. When performing color adjustment during execution of a job, the control unit adjusts the printing position of the image forming unit in advance. The image forming apparatus according to claim 4 .

6. When printing each page in a job, if high-quality printing is set, the control unit adjusts the print position and then performs color adjustment using the image. The image forming apparatus according to claim 5 .

7. when the control unit adjusts the print position during execution of the job, the control unit changes the size interval of the patches in accordance with the conveyance speed of the paper, and performs color adjustment of the image forming unit. The image forming apparatus according to claim 4 .

8. When a second sheet of paper that is the same type as a first sheet of paper to be printed in the job and that is longer in the main scanning direction is stored in a paper feed tray different from the paper feed tray that stores the first sheet of paper during execution of the job, the control unit prints, after adjusting the print position of the image forming unit, a chart on the second sheet of paper in which more patches are arranged in the main scanning direction than the chart on the first sheet of paper. The image forming apparatus according to claim 4 .

9. When a second sheet of paper, which is the same type as a first sheet of paper to be printed in the job but is longer in the main scanning direction, is stored in one of the paper feed trays during execution of the job, the control unit, after adjusting the print position of the image forming unit, changes the size interval of the patches of the chart for the second sheet of paper and prints a chart on the second sheet of paper in which more patches are arranged in the main scanning direction than in the chart for the first sheet of paper. The image forming apparatus according to claim 4 .

10. when the patch size of the chart is below a threshold value or the patch interval is below a threshold value, the control unit adjusts the print position of the image forming unit, then prints the chart, and performs color adjustment of the image forming unit. The image forming apparatus according to claim 4 .

11. the control unit stores, for each paper feed tray, the time of image position adjustment using the paper stored in the paper feed tray, and when the elapsed time from the stored time is within a threshold value or when the number of printed sheets is within a threshold value, performs color adjustment without adjusting the print position of the image forming unit. The image forming apparatus according to claim 4 .

12. When there are a plurality of paper feed trays containing the same type of paper, the control unit selects one of the paper feed trays whose image position adjustment period is within a threshold value, and performs color adjustment without adjusting the print position of the image forming unit. The image forming apparatus according to claim 4 .

13. the control unit prints the chart by either one of a method of changing a patch size and / or a patch interval based on a threshold value for the timing of position adjustment of paper on which the chart is output and printing the chart, or a method of adjusting an image position and then printing the chart at a predetermined patch size, which can save the number of sheets of paper; The image forming apparatus according to claim 4 .

14. the control unit prints the chart by either one of a method of printing the chart after changing the patch size and / or the patch interval based on a threshold value for the timing of position adjustment of the paper on which the chart is output, and a method of printing the chart with a predetermined patch size after performing image position adjustment, which can shorten the time. The image forming apparatus according to claim 4 .

15. an image forming unit printing an image on the transported paper; a step in which a control unit reads the paper as an image using a sensor; a step of adjusting a printing position on the paper by the image forming unit from a position of the image printed on the paper by the control unit; a step in which the control unit performs color adjustment of the image forming unit using a chart printed by the image forming unit; An adjustment method for an image forming apparatus, comprising:

16. The computer that controls the image forming apparatus includes: a step of printing an image on the transported paper by an image forming unit; reading the paper with an image sensor; a step of adjusting a printing position on the paper by the image forming unit from a position of the image printed on the paper; a step of performing color adjustment of the image forming unit using a chart printed by the image forming unit; A program to execute.

Images