Image forming apparatus, gradation patch forming method, and evaluation chart for image forming apparatus

Abstract

To provide an image forming apparatus that forms a gradation patch for density correction on a sheet material, reads a gradation patch image, and does not impair real-time performance when performing correction.SOLUTION: In an image forming apparatus, a control unit acquires density information from image information of a print image formed on a sheet material S, and determines, from the acquired density information, a width of a gradation patch P in a sheet material conveying direction in a blank area SB as an area of the sheet material S excluding an image area SA, and performs control to form gradation patch patterns 400K, 400C, 400M, and 400Y composed of a plurality of gradation patches P (P1 to P8) with different widths in the sheet material conveying direction. The gradation patches P include a gradation patch Pa having a large width in the sheet material conveying direction and a patch Pb having a small width in the sheet material conveying direction.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus, a method for forming a gradation patch, and an evaluation chart for the image forming apparatus. [Background technology]

[0002] 2. Description of the Related Art In some image forming apparatuses, a tone patch for density correction is formed on a sheet material, the tone patch image is read by a reading means (an in-line sensor), and correction is performed based on the reading result.

[0003] Conventionally, there is known a device that includes a print image analysis unit that analyzes the placement of a print image formed in an image forming area of ​​the paper relative to the paper, and a patch image position determination unit that determines the position of a patch image for image correction to be formed outside the image forming area of ​​the paper based on the analysis results of the print image analysis unit (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-005173 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the distance between the target (density detection area) to be read by the reading means (in-line sensor) and the gradation patch that is not the target to be read is short, a phenomenon called "flare" occurs in which the gradation patch cannot be read accurately. In addition, if the density difference of the target to be read is large, the effect of flare becomes large.

[0006] Here, if one were to try to suppress the effects of flare by simply making the gradation patches larger (wider), the margin area would be limited, which would result in the necessary gradation patches having to be formed across multiple sheets of material, thereby impairing real-time performance.

[0007] The present invention has been made in view of the above problems, and has an object to prevent loss of real-time performance. [Means for solving the problem]

[0008] In order to solve the above problems, an image forming apparatus according to the present invention comprises: Obtain density information from image information of the print image; determining a width of a gradation patch to be image-formed in a sheet material conveying direction from the acquired density information; and controlling the formation of the gradation patches having different widths in the sheet material conveying direction in a marginal area of ​​the sheet material. 、 The formed tone patch has a width of the tone patch of a prioritized tone that is wider than a width of the tone patch of a tone other than the prioritized tone. The composition was as follows. Effect of the Invention

[0009] According to the present invention, it is possible to prevent the loss of real-time performance. [Brief description of the drawings]

[0010] [Figure 1] 1 is an illustrative side view of an example of an image forming apparatus according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram illustrating the device. [Diagram 3] FIG. 2 is an explanatory diagram illustrating an evaluation chart of the image forming apparatus according to the first embodiment of the present invention. [Figure 4] 1A to 1C are plan explanatory diagrams illustrating different examples of the arrangement of gradation patch patterns (gradation patches). [Diagram 5] 5 is a flow diagram illustrating a printing process (forming process) of a gradation patch image (gradation patch pattern) by a control unit in the first embodiment. FIG. [Figure 6] 6 is a flow diagram illustrating the print data (print image) analysis process of FIG. 5. [Figure 7] FIG. 10 is an explanatory diagram for explaining the concentration information acquisition process. [Figure 8]6 is a flow diagram illustrating a patch process for determining the patch shape of FIG. 5. FIG. [Figure 9] FIG. 11 is an explanatory diagram illustrating the priority gradation determination process. [Figure 10] FIG. 4 is a flow diagram illustrating the operation of the inspection unit. [Figure 11] FIG. 11 is an explanatory diagram illustrating a tone patch according to a second embodiment of the present invention. [Figure 12] FIG. 11 is an explanatory diagram illustrating the priority gradation determination process. [Figure 13] FIG. 13 is an explanatory diagram illustrating a tone patch according to a third embodiment of the present invention. [Figure 14] FIG. 13 is an explanatory diagram for explaining a fourth embodiment of the present invention. [Figure 15] FIG. 13 is an explanatory diagram of an image forming apparatus according to a fifth embodiment of the present invention. [Figure 16] FIG. [Figure 17] FIG. 13 is an explanatory diagram for explaining a sixth embodiment of the present invention. [Figure 18] 13 is a flow diagram illustrating an example of a printing process of a gradation patch by a control unit according to the fifth embodiment. FIG. [Figure 19] FIG. 23 is an explanatory diagram of an example of a gradation patch pattern in a seventh embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. An image forming apparatus according to a first embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a side view of the image forming apparatus.

[0012] The image forming apparatus 200 includes an apparatus main body 201 to which a scanner unit 202, an operation unit 203, and a discharge unit 204 are connected.

[0013] The apparatus main body 201 includes an image forming section 210, a sheet material conveying section 220, a fixing section 230, an inspection unit 240, and a control section 300. The control section 300 controls the overall operation of the image forming apparatus 200 and also serves as a means for controlling the formation of gradation patches on the sheet material S.

[0014] The image forming section 210 includes photoconductor units 214 (214y, 2145m, 214c, 214k) and image forming units 215 (215y, 215m, 215c, 215k) to form latent images corresponding to the images of each color. The image forming units 215 include a charging unit, a LD writing unit, and a developing unit.

[0015] The photoconductor unit 214 is disposed along an endless intermediate transfer belt 216. The intermediate transfer belt 216 is passed around at least one driving roller and a plurality of driven rollers, and moves between a primary transfer position where an image (toner image) developed by the photoconductor unit 214 is transferred, and a secondary transfer position where the image (toner image) is transferred to the sheet material S.

[0016] At the secondary transfer position, a transfer section 217 including a transfer roller 217a and an opposing roller 217b arranged opposite to the transfer roller 217a is disposed. In the transfer section 217, a toner image is transferred from the intermediate transfer belt 216 to the sheet material S, so that a color image is formed at a predetermined position on the sheet material S.

[0017] The sheet material conveying section 220 includes a supply tray 221 (221A, 221B) that stores sheet material S for image formation. The sheet material conveying section 220 includes a conveying path 222, a conveying path switching section 224, and a reversing path 225, the conveying path 222 being configured by a plurality of roller pairs along which the sheet material S is conveyed.

[0018] During the image formation process, under the control of a predetermined control process by the control unit 300, the image forming unit 215 charges the photoconductor unit 214 of each color and exposes it to light in accordance with the original image, thereby forming an electrostatic latent image on the photoconductor unit 214.

[0019] Then, toner is applied to the electrostatic latent images on the photoconductor units 214 corresponding to yellow, magenta, cyan, and black, respectively, using the developing sections of the image forming units 215, to form toner images of the respective colors.

[0020] Next, the toner images formed on the yellow, magenta, cyan and black photoconductor units 214 are sequentially primarily transferred onto the surface of the intermediate transfer belt 216 which is rotated.

[0021] On the other hand, the sheet material S accommodated in the supply tray 221 is separated by a pickup roller or the like, and is transported along a transport path 222 to the transfer unit 217 .

[0022] Then, when the sheet material S reaches the transfer section 217, a transfer process is performed. That is, the sheet material S is conveyed in a predetermined conveying direction while being sandwiched between the surface of the intermediate transfer belt 216, which is urged toward the opposing roller 217b by the transfer roller 217a, and the opposing roller 217b. When the sheet material S passes between the intermediate transfer belt 216 and the opposing roller 217, the toner images of each color that have been primarily transferred onto the intermediate transfer belt 216 are secondarily transferred onto the sheet material S, forming a color image. By this transfer process, an image is formed on one side (first side) of the sheet material S.

[0023] The sheet material S on whose first surface the color image has been formed by the image forming unit 210 is further conveyed and sent to the fixing unit 230. The fixing unit 230 performs a fixing process on the sheet material S on which the color toner image has been formed. The fixing unit 230 applies pressure and heat to the conveyed sheet material S to fix the transferred toner image onto the sheet material S.

[0024] In the case of single-sided printing, the sheet material S that has been subjected to the fixing process by the fixing section 230 is transported to the inspection unit 240.

[0025] In the case of double-sided printing, the sheet material S is conveyed to a conveying path switching section 224. Thereafter, the sheet material S reverses its traveling direction and is conveyed to a reversing path 225. Then, the sheet material S is conveyed again to a transfer section 217 in a state in which the image formed on the intermediate transfer belt 216 is transferred to the second side of the sheet material S.

[0026] The sheet material S with the image formed on the second surface is further transported, and after the image on the second surface is fixed in the fixing section 230, the sheet material S is transported to the inspection unit 240.

[0027] A passage sensor 260 for detecting the passage of the sheet material S is disposed upstream of the inspection unit 240 .

[0028] The inspection unit 240 is provided with two (upper and lower) in-line sensors 241, 241 as image reading devices, sandwiching the conveying path of the sheet material S, and reads the image formed on the sheet material S. When double-sided printing is performed, the two in-line sensors 241, 241 read both the front and back sides of the sheet material S at once.

[0029] The inspection unit 240 performs image analysis of the read image and transmits color correction data to a printer unit 307 described later. The in-line sensor 241 uses a line sensor in which a plurality of photoelectric conversion elements are linearly arranged across the entire width direction (direction perpendicular to the conveying direction: main scanning direction) of the sheet material S. The inspection unit 240 also reads images of gradation patches.

[0030] The sheet material S that has passed through the inspection unit 240 is discharged to the discharge unit 204 .

[0031] Next, the control unit will be described with reference to the block diagram of FIG.

[0032] The control unit 300 includes a CPU 301 that performs main control, a RAM 302 that provides a processing space used by the CPU 301 for processing, and a ROM 303 in which programs for the CPU 301 and the like are stored.

[0033] The control unit 300 includes an image storage 304 , an I / O control unit 305 , an operation unit 306 , a printer unit 307 , a scanner unit 308 , and an inspection unit 309 .

[0034] The scanner unit 308 controls the scanner 202. The printer unit 307 processes input image data and controls a laser diode (LD) of the image forming unit 215 to expose the photoconductor unit 214. The printer unit 307 also performs color correction and generates tone patches for color correction based on the analysis results of the inspection unit 309.

[0035] An operation unit 306 receives instructions from a user and executes processes such as copying, facsimile, scanning, and image storage.

[0036] The image storage 304 is configured as a fixed or removable memory device such as a hard disk drive, an SD card, or a USB memory, and stores image data acquired by the image forming apparatus 200, making it available for various processing by the user.

[0037] An I / O control unit 305 drives various motors, performs detection by various sensors, controls the fixing unit, and controls the photoconductor and intermediate transfer unit.

[0038] The inspection section 309 controls the in-line sensor 241 of the inspection unit 240 and analyzes the read image data.

[0039] Next, the gradation patch in the first embodiment of the present invention will be described with reference to Fig. 3. Fig. 3 is an explanatory diagram of an evaluation chart of an image forming apparatus provided for the description, in which (a) is an explanatory diagram of an example of an evaluation chart including a flare-compatible gradation patch according to the embodiment, and (b) is an explanatory diagram of an example of an evaluation chart including a flare-uncompatible gradation patch according to a comparative example.

[0040] In this embodiment, the control unit 300, which functions as a means for controlling the formation of the gradation patch, acquires density information from the image information of the print image, and determines the width of the gradation patch P in the sheet material transport direction from the acquired density information.

[0041] Then, the control unit 300 controls the formation of a gradation patch pattern 400 (400K, 400C, 400M, 400Y) consisting of multiple gradation patches P (P1 to P8) for image correction (e.g., color correction) having different widths in the sheet material transport direction, as shown in Figure 3 (a).

[0042] The gradation patch pattern 400 is formed by arranging gradation patches P along the sheet material transport direction in a margin area SB, which is an area excluding the image area SA of the sheet material S, in a direction perpendicular to the sheet material transport direction (main scanning direction).

[0043] Here, the gradation patches P include gradation patches Pa that are wide (thick) in the sheet material transport direction (hereinafter referred to as "sub-scanning width") and patches Pb that are narrow (thin) in the sub-scanning width. In the example of the gradation patch pattern 400K of K in Fig. 3(a), the gradation patches P1 to P5 are gradation patches Pb with a narrow sub-scanning width, and the gradation patches P6 to P8 are gradation patches Pa with a wide sub-scanning width.

[0044] Specifically, with higher gradations being given priority, the gradation patch P of the higher gradations given priority is made a patch Pa with a wider sub-scanning width, and the gradation patch P of the lower gradations other than the priority gradation is made a gradation patch Pb with a narrower sub-scanning width. In other words, the sub-scanning width of the gradation patch P of the priority gradation is wider than the sub-scanning width of the gradation patch P of the gradation other than the priority gradation. The priority gradation is determined based on the printing information and the width information of the margin area.

[0045] Thus, the evaluation chart for the image forming device in this embodiment is an evaluation chart for the image forming device formed on a sheet material by the image forming device, and has a printed image formed in the image area SA and a gradation patch P formed in the margin area SB outside the image area SA, and the gradation patch P is a chart with different widths in the sheet material transport direction.

[0046] As a result, the area of ​​the gradation patch Pa with higher gradation levels, which is given priority, becomes larger and is no longer affected by flare.

[0047] Here, if the gradation patches are formed across multiple sheet materials, it takes time to calculate the density correction value, and color correction when forming an image with print information is delayed (real-time performance is impaired). However, the width of each gradation patch P (Pa, Pb) is determined so that the overall width (length) of all the gradation patch patterns 400 (400K, 400C, 400M, 400Y) in the sheet material conveying direction is the same as that of the gradation patch pattern 400 not compatible with flare shown in FIG. 3(b).

[0048] This ensures real-time performance even when the width (sub-scanning width) of the gradation patch in the sheet material transport direction is changed.

[0049] Furthermore, between adjacent colors, the gradation patches 400 are formed such that, for example, odd-numbered colors (K, M) are formed from the light-to-dark side in the sheet conveying direction, and even-numbered colors (C, Y) are formed from the dark-to-light side, thereby reducing the density difference between adjacent patches.

[0050] Next, a different example of the arrangement of the gradation patch pattern (gradation patch) will be described with reference to Fig. 4. Fig. 4 is a plan view for the same description. Note that the description here is for a general gradation patch (a gradation patch having the same sub-scanning width and main scanning width).

[0051] 4A, a gradation patch pattern 400 for color correction is formed in margin areas (side margin areas) SB, SB on both sides in a direction (main scanning direction) perpendicular to the sheet material conveying direction. The gradation patch pattern 400 is disposed in the margin area SB outside the image area SA and on the outside of the cutting portion.

[0052] On one side of the sheet material S, there is a margin area SB with a width of (sheet material size-image area) / 2. If printing misalignment occurs in the main scanning direction of the gradation patch pattern 400 within this margin area SB, the gradation patch pattern 400 will protrude outside the sheet material S. Therefore, to prevent the gradation patch pattern 400 from being adjacent to the image area SA side, a gap is provided, and the length of the gradation patch pattern 400 in the main scanning direction is set to a width narrower than (sheet material size-image area) / 2.

[0053] In Figure 4(b), a gradation patch pattern 400 for color correction is formed in the margin areas SB on both sides in the direction perpendicular to the sheet material transport direction (main scanning direction), and a gradation patch pattern 400 is also formed in the margin area SC on the leading end side of the sheet material S and in the margin area SD on the trailing end side.

[0054] For example, when the sheet material S is A3 size or SRA3 size, the length in the sub-scanning direction is longer, so the area for forming the gradation patch pattern 400 can be secured in the margin areas SB, SB at both ends in the main scanning direction. Therefore, priority is given to arranging the gradation patch pattern 400 in the margin area SB. In this case, if the area required for the gradation patch pattern 400 is sufficient in the margin area SB alone, it is arranged only in the margin area SB, and when the margin areas SB on both sides are insufficient, the gradation patch pattern 400 is also arranged in the margin area SC at the leading end and the margin area SD at the trailing end.

[0055] Furthermore, in the case of a sheet material S having a longer main scanning direction, such as an A4 size sheet S, priority is given to the arrangement of the gradation patch pattern 400 in the leading blank area SC and the trailing blank area SD.

[0056] Other possible combinations of areas in which the gradation patch pattern 400 is arranged include only the side margin area SB, only the leading margin area SC, only the trailing margin area SD, and only the leading and trailing margin areas SC and SD.

[0057] Next, the printing process (forming process) of a gradation patch image (gradation patch pattern) by the control unit in the first embodiment will be described with reference to the flow diagram of FIG.

[0058] This process is started by a user executing a print command, and the control unit 300 receives print data for a print image (step S1, hereinafter simply referred to as "S1").Then, the control unit 300 analyzes the print data (S2), and determines the shape (patch shape) of the gradation patches P that make up the gradation patch pattern 400 based on the analysis results (S3).

[0059] Thereafter, the control unit 300 performs general image processing and color correction calculated from the results of reading the gradation patches P of the gradation patch pattern 400 by the inspection unit 240 (S4).

[0060] Then, a print image is printed in the image area SA of the sheet material S, and a gradation patch pattern 400 (patch image) consisting of gradation patches P is printed in the margin area SB (S5).

[0061] Next, the print data (print image) analysis process of Fig. 5 will be described with reference to Fig. 6 and Fig. 7. Fig. 6 is a flow diagram for explaining the print data analysis process, and Fig. 7 is an explanatory diagram for explaining the density information acquisition process.

[0062] First, the control unit 300 acquires information on the type of the sheet material S (hereinafter referred to as "paper type information") (S11). Here, since the paper type information is the paper type information set in advance by the operation unit 203 and stored in the ROM 303, the control unit 300 acquires the paper type information from the ROM 303.

[0063] Next, margin information of the sheet material S is obtained (S12). Here, the margin information is information on the margin areas SB, SB at both ends in the main scanning direction described above. Note that, when gradation patch patterns 400 are arranged in the margin areas SC, SD at the leading and trailing ends, information on the margin areas SC, SD is also obtained. The margin information is a value set by the user via the operation unit 203 and is obtained by the CPU 301.

[0064] Thereafter, the print data (image data) of the print image is divided into area units, the gradation values ​​are measured, and density information is obtained (S13).

[0065] For example, as shown in Fig. 7, image data is divided into pixel area units in the main scanning direction X and sub-scanning direction Y, and the average pixel density is measured for C, M, Y, and K in each area, and this is used as the gradation value. Here, it is divided into "main scanning N x sub-scanning M" areas.

[0066] Measuring the gradation value in area units and measuring the average pixel density means converting the density of the target pixel in a divided area and dividing it by the number of pixels in that area.

[0067] Next, the patch process for determining the patch shape of Fig. 5 will be described with reference to Fig. 8 and Fig. 9. Fig. 8 is a flow diagram for explaining the patch process, and Fig. 9 is an explanatory diagram for explaining the priority tone determination process.

[0068] First, the control unit 300 determines the priority order of the colors K, C, M, and Y (S21). Here, the number of regions with a density value greater than "0" is counted from the results of measuring the density values ​​of K, C, M, and Y for each divided region, and the priority order is determined based on the number of counts. The priority order may also be determined by accumulating the density for each region and accumulating (density x number of regions).

[0069] Next, a priority gradation is determined for each color (K, C, M, Y) (S22). Here, too, the results of measuring the density values ​​of K, C, M, Y for each divided area are used.

[0070] For example, as shown in Fig. 9, the gradation values ​​from 0 to 255 are classified into eight gradation range groups (No. 1 to No. 8). Then, the density values ​​of each color (KCMY) in the divided regions are counted for each of the eight classifications.

[0071] As a result, the count results of each of KCMY are obtained, for example, as shown in Fig. 9. Therefore, in this embodiment, the gradations with a count value of 20 or more are determined as prioritized gradations, and the gradations in classifications No. 6, No. 7, and No. 8 of all colors of KCMY are determined as prioritized gradations.

[0072] Next, the patch width of the gradation patch P in the main / sub-scanning directions is determined (S23).

[0073] Here, the patch width in the sub-scanning direction is determined from the margin information. If there is sufficient margin, the gradation patch pattern 400 of all colors and all tones may be arranged. If the area is insufficient, the number and width of gradation patches are determined so that the prioritized colors and tones fit within the margin area SB.

[0074] The patch width of the gradation patch P in the sub-scanning direction is determined as a reference width based on the size of the sheet material S. The reference width is a uniform width with no priority order. Based on the priority order of color and gradation value, the gradation patch P of a low priority gradation, i.e., a gradation other than the prioritized gradation, is made into a gradation patch Pb with a narrower sub-scanning width, and the gradation patch P of a high priority gradation, i.e., a gradation patch P of a prioritized gradation, is made into a gradation patch Pa with a wider sub-scanning width.

[0075] For example, the sub-scanning width of the tone patch P (Pb) of a tone other than the prioritized tone is set to half the reference width. The sub-scanning width of the tone patch P (Pa) of the prioritized tone is allocated the surplus width resulting from setting the tone patch Pb of a tone other than the prioritized tone to half the reference width.

[0076] In other words, Sub-scanning width of tone patch Pb of tone other than the priority tone = reference width x 0.5 Sub-scanning width of tone patch Pa of prioritized tone = reference width x 0.5 x number of tone patches Pb of tones other than the prioritized tone / number of tone patches Pa of prioritized tone + reference width Let us assume that.

[0077] In this embodiment, as shown in Fig. 3(a), there is no priority order for colors, and gradations with high gradation values ​​(classifications No. 6 to No. 8 in Fig. 9) are prioritized gradations, with the sub-scanning width of the gradation patches P being made wider, while gradations other than the prioritized gradations (classifications No. 1 to No. 5 in Fig. 9) have a narrower sub-scanning width. Also, by generating the gradation patches P from the lighter density side to the darker side for the first color and generating the gradation patches P from the darker side for the second color, the density difference between adjacent gradation patches P is reduced.

[0078] As described above, in this embodiment, a gradation patch is formed by carrying out the steps of acquiring density information from image information of a printed image, determining the width of the gradation patch to be image-formed in the sheet material transport direction from the acquired density information, and forming the gradation patches having different widths in the sheet material transport direction in the margin area of ​​the sheet material.

[0079] Next, the operation of the inspection unit will be described with reference to the flow chart of FIG.

[0080] This process is executed when the user starts the printing operation by executing printing. First, the inspection unit 309 determines whether or not a patch image is to be formed (S31). This determination is made by checking the presence / absence information of the patch image from the CPU 301.

[0081] If a patch image is present, the patch image is read by the in-line sensor 241 (S32). The timing of reading is controlled by detecting the sheet material S by the passage sensor 260.

[0082] Then, based on the result of reading, the average density value of each patch is calculated (S33). The position and sub-scanning width of each patch can be read accurately by inputting information from the CPU 301 to the inspection unit 309.

[0083] Thereafter, a color correction value is calculated from the difference between the target value and the read value (S34), and transmitted to the printer unit 307. The printer unit 307 corrects the color of the image based on the received color correction value.

[0084] Next, a second embodiment of the present invention will be described with reference to Fig. 11 and Fig. 12. Fig. 11 is an explanatory diagram for explaining gradation patches in the second embodiment, and Fig. 12 is an explanatory diagram for explaining a priority gradation determination process in the same embodiment.

[0085] In this embodiment, the number of gradation patches P of the prioritized color is increased, the number of gradation patches P of colors other than the prioritized color is decreased, and the sub-scanning width of the gradation patch P of the prioritized gradation is increased. Note that, although this embodiment is carried out under both conditions of whether or not the color is prioritized and whether or not the gradation is prioritized, it may be carried out under only one condition.

[0086] This improves real-time performance.

[0087] For example, in the example of Fig. 11, K and M are prioritized among the colors (K, C, M, Y) based on the count value of the density value of each region as shown in Fig. 12. The higher gradations of K and M are prioritized, and the number of gradation patches P for the prioritized gradations is increased to increase the number of gradations of the prioritized gradations, and the sub-scanning width on the higher gradation side is made wider. Note that the sub-scanning width in Fig. 12 is usually the same as the reference width.

[0088] On the other hand, since there is no density for C and Y, which are not prioritized colors, the number of C and Y gradation patches P is reduced. In this case, the gradation difference of the gradation patches P of K and M, which are prioritized colors, is smaller than the gradation difference of the gradation patches P of C and Y, which are colors other than the prioritized colors.

[0089] This ensures that the sub-scanning width of all gradation patches P of all colors does not change from the gradation patch pattern 400 formed with the reference width (normal sub-scanning width).

[0090] The relationship between the gradation patches P of the prioritized colors K and Y and the gradation classification No. is as shown in Figure 12. In this example, the gradation patches corresponding to classifications No. 0.3 and No. 0.4 are two (multiple) gradation patches P with different gradation values, as shown in Figure 11. By using multiple gradation patches P, it is possible to improve detection and correction accuracy compared to other gradations.

[0091] Next, a third embodiment of the present invention will be described with reference to Fig. 13. Fig. 13 is an explanatory diagram for explaining a tone patch in the third embodiment.

[0092] In this embodiment, when there is no density for the colors C and Y, as in the counting result shown in Fig. 12 described in the second embodiment, tone patches for C and Y are not formed. In other words, this is an embodiment in which tone patches for colors other than the prioritized color are not formed.

[0093] This improves real-time performance.

[0094] Next, a fourth embodiment of the present invention will be described with reference to Fig. 14. Fig. 14 is an explanatory diagram for explaining the fourth embodiment.

[0095] In this embodiment, density information is obtained from the image information of the printed image to be formed on the following sheet material, the sub-scanning width of the gradation patch P is determined from the obtained density information, and the gradation patch P with a different sub-scanning width is formed in the margin area SB of the preceding sheet material.

[0096] For example, when a first sheet S1 is the preceding sheet, density information is obtained from image information of a print image for a second sheet S2, which is the following sheet. Then, the sub-scanning width of the gradation patches P constituting the gradation patch pattern 400 is determined from the obtained density information, and gradation patches P with different sub-scanning widths are formed in the margin area SB of the preceding sheet S1.

[0097] Similarly, when the second sheet material S2 is the preceding sheet material, density information is obtained from image information of the print image for the third sheet material S3, which is the succeeding sheet material. Then, the sub-scanning width of the gradation patches P constituting the gradation patch pattern 400 is determined from the obtained density information, and the gradation patches P with different sub-scanning widths are formed in the margin area SB of the preceding sheet material S2.

[0098] In other words, in this embodiment, for two sheets of sheet material that are transported in succession, the succeeding sheet material is treated as the "following sheet material," and density information is obtained from the printing information for the succeeding sheet material to form a gradation patch on the preceding sheet material.

[0099] Then, the gradation patch pattern 400 of the first sheet material S1 is read by the inspection unit 240, a color correction value is calculated according to the read result, and color correction is performed when forming an image with the print information on the second sheet material S2. Similarly, the gradation patch pattern P of the second sheet material S2 is read by the inspection unit 240, a color correction value is calculated according to the read result, and color correction is performed when forming an image with the print information on the third sheet material S3.

[0100] This improves real-time performance.

[0101] Next, a fifth embodiment of the present invention will be described with reference to Figures 15 and 16. Figure 15 is an explanatory diagram of an image forming apparatus according to the fifth embodiment, and Figure 16 is an explanatory diagram for explaining the operation of the same.

[0102] In the image forming apparatus 200 of this embodiment, the sheet material S that has passed through the inspection unit 240 is transported to a reverse path 225 via a transport path switching unit 224. The inspection unit 240 also includes an in-line sensor 241 that reads one side of the sheet material S.

[0103] By providing the conveying path of the image forming apparatus 200 configured in this manner, the pattern of the fourth embodiment can be realized even when printing is performed on the front and back sides of the sheet material S. That is, as shown in Fig. 16, the front side of the sheet material S1 is the preceding sheet material, and density information is obtained from image information of the print image on the back side of the first sheet material S1, which is the following sheet material. Then, the sub-scanning width of the gradation patches P constituting the gradation patch pattern 400 is determined from the obtained density information, and gradation patches P with different sub-scanning widths are formed in the margin area SB on the front side of the preceding sheet material S1.

[0104] After the image is formed on the front surface of the sheet S1, the in-line sensor 241 reads the gradation patch pattern 400 on the front surface of the sheet S1. The sheet S1 passes through the transport path switching unit 224 and the inversion path 225, and an image is formed on the rear surface of the sheet S1.

[0105] At this time, the back surface of the first sheet material S1 is set as the preceding sheet material, and the front surface of the second sheet material S2 is set as the following sheet material, and similarly, density information is obtained from image information of the print image on the front surface of the sheet material S2. Then, the sub-scanning width of the gradation patches P constituting the gradation patch pattern 400 is determined from the obtained density information, and the gradation patches P with different sub-scanning widths are formed in the margin area SB on the back surface of the sheet material S1.

[0106] After the image is formed on the rear surface of the sheet S1, the in-line sensor 241 reads the gradation patch pattern 400 on the rear surface of the sheet S1, and the sheet S1 is discharged.

[0107] In this way, even when performing double-sided printing, the surface to be printed first of the successive printing surfaces can be treated as the leading sheet material, and the surface to be printed next can be treated as the trailing sheet material, and image formation and correction of the gradation patch pattern can be performed.

[0108] Next, a fifth embodiment of the present invention will be described with reference to Fig. 17. Fig. 17 is an explanatory diagram for explaining the fifth embodiment.

[0109] In this embodiment, the tone patch is formed by acquiring density information from print information for a following sheet material that is two or more sheets away from the preceding sheet material.

[0110] For example, when the first sheet S1 is the preceding sheet, density information is obtained from image information of a print image for the fourth sheet S4 (the sheet three sheets behind the preceding sheet), which is the succeeding sheet.Then, the sub-scanning width of the gradation patch P is determined from the obtained density information, and the gradation patch P with a different sub-scanning width is formed in the margin area SB of the preceding sheet S1.

[0111] Similarly, when the second sheet S2 is the preceding sheet, density information is obtained from the image information of the print image for the fifth sheet S5, which is the succeeding sheet. Then, the sub-scanning width of the gradation patch 400 is determined from the obtained density information, and the gradation patch 400 with a different sub-scanning width is formed in the margin area SB of the preceding sheet S2.

[0112] In this example, the sheet material three sheets away from the sheet material S, which is the preceding sheet material, is treated as the following sheet material, and density information is obtained from the printing information for the following sheet material to determine the sub-scanning width of the gradation patch, and the gradation patch is formed in the margin area of ​​the preceding sheet material.

[0113] That is, as in the fourth embodiment, if two sheets conveyed in succession are the leading sheet and the trailing sheet, a correction value for the trailing sheet is calculated after the leading sheet reaches the position of the inspection unit 240. Therefore, in order to reflect the color correction on the next page, the normal printing speed is slowed down, that is, the interval (paper gap) between the consecutive sheets S is widened. As a result, there is a risk of a decrease in productivity.

[0114] Therefore, the preceding and succeeding sheets are set at intervals that do not reduce the productivity of the device. The example in Fig. 17 is an example in which the correction result can be reflected on the fourth sheet S4 by reading the gradation patch P for the fourth sheet S4 formed on the first sheet S1 without reducing the productivity.

[0115] In addition, this embodiment is not limited to the case where the following sheet material is (preceding sheet material + 3) as in the example of Figure 17 above, but also includes the case where the following sheet material is (preceding sheet material + m) (m = an integer greater than or equal to 2).

[0116] This makes it possible to perform correction without reducing productivity and ensure color accuracy.

[0117] Next, an example of a printing process of a gradation patch by the control unit in the sixth embodiment will be described with reference to the flow chart of FIG.

[0118] This process is started by a user executing print, and the control unit 300 receives print data for all pages and sets N to 0 (S41). Then, the control unit 300 determines whether or not there is print data for the (N+3)th page (S42).

[0119] Here, when there is printing data on the (N+3)th page, the control unit 300 analyzes the printing data on the (N+3)th page (S43), and determines the shape (patch shape) of the gradation patch 400 on the (N+3)th page based on the analysis results (S44).

[0120] Thereafter, the control unit 300 performs general image processing and color correction calculated from the reading result of the inspection unit 240 (S45). However, when N=1, 2, or 3, default color correction is performed.

[0121] Then, the print image (print data) of the (N)th page and the image (patch image) of the gradation patch 400 of the (N+3)th page are printed (S46). The gradation patch 400 has the shape determined in step S44.

[0122] On the other hand, if there is no print data for the (N+3)th page in step S42, the control unit 300 sets the patch to OFF (S49), and then the process proceeds to step S45.

[0123] In this case, in steps S45 and S46, general image processing and color correction calculated from the reading results of the inspection unit 240 are performed, and when the print image (print data) of the (N)th page is printed, the gradation patch P is not formed.

[0124] Thereafter, it is determined whether or not all pages have been printed (S47), and if not, N=(N+1) is set (S48), and the process returns to step S42; if all pages have been printed, the process ends.

[0125] Next, a seventh embodiment of the present invention will be described with reference to Fig. 19. Fig. 19 is an explanatory diagram of an example of a gradation patch pattern in this embodiment.

[0126] In each of the above-described embodiments, the width of one gradation patch P in each gradation patch pattern 400 is made different from each other. In this embodiment, however, for example, the entire gradation patch pattern 400 of KCMY is made different.

[0127] 19, the width of the entire gradation patch pattern 400K for K (No. 1 to 9) is set larger than the width of the entire gradation patch pattern 400M for M (No. 1 to 9). Note that in this example, there are many gradations of K and few or no gradations of M (C, Y).

[0128] The above-described embodiments are not limited to printing gradation patches on all sheet materials. For example, gradation patches may be printed every predetermined number of prints. If gradation patches are printed every 5 sheets, gradation patches are printed on the preceding sheet materials based on the print image (print data) of the 5th sheet (10th sheet, 15th sheet, etc.). Also, when the print image (print data) satisfies a predetermined condition, the gradation patches may be printed on the preceding sheet materials. [Explanation of symbols]

[0129] 200 Image forming device 201 Device body 202 Scanner section 203 Operation section 210 Image forming section 220 Sheet material conveying section 230 Fixing unit 240 Inspection unit (reading means) 300 Control section (means for controlling) S Sheet material

Claims

1. Obtain density information from image information of the print image; a means for determining a width of a gradation patch to be image-formed in a sheet material conveying direction from the acquired density information, and controlling the formation of the gradation patches having different widths in the sheet material conveying direction in a marginal area of ​​the sheet material, The formed tone patch has a width of the tone patch of a prioritized tone that is wider than a width of the tone patch of a tone other than the prioritized tone.

1. An image forming apparatus comprising:

2. The gradation difference of the gradation patch of a prioritized color is smaller than the gradation difference of the gradation patch of a color other than the prioritized color, and The number of the tone patches of the prioritized color is greater than the number of the tone patches of the colors other than the prioritized color.

2. The image forming apparatus according to claim 1,

3. The tone patches of colors other than the priority color are not formed.

2. The image forming apparatus according to claim 1,

4. The prioritized gradation is determined based on the width of the print image and the margin area.

4. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi-color image forming apparatus.

5. The print image and the width of the margin area are data to be printed for each fixed number of sheets.

5. The image forming apparatus according to claim 4.

6. The density information is obtained from image information of a print image to be formed on a succeeding sheet material; Forming the gradation patch on the preceding sheet material 6. The image forming apparatus according to claim 1,

7. When there is no print image to be formed on the following sheet material, the gradation patch is not formed on the preceding sheet material.

7. The image forming apparatus according to claim 6,

8. a reading means for reading the gradation patch of the sheet material; and a means for calculating a color correction value from the reading result of the reading means.

8. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi-function device.

9. acquiring density information from image information of a print image; determining a width of a gradation patch to be image-formed in a sheet material conveyance direction from the acquired density information; forming the gradation patches having different widths in the sheet material conveying direction in a marginal area of ​​the sheet material; The formed tone patch has a width of the tone patch of a prioritized tone that is wider than a width of the tone patch of a tone other than the prioritized tone. A method for forming a gradation patch comprising:

10. An evaluation chart of an image forming apparatus formed on a sheet material by an image forming apparatus, A print image formed in an image area; a gradation patch formed outside the image area; The tone patches have different widths in the conveyance direction of the sheet material, and the width of the tone patch of a prioritized tone is wider than the width of the tone patch of a tone other than the prioritized tone. 1 is an evaluation chart for an image forming apparatus according to the present invention.

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