JP6624096B2 - Image forming apparatus, voltage adjustment method - Google Patents

Description

  The present invention relates to an image forming apparatus capable of forming a color image by an electrophotographic method, and a voltage adjusting method executed in the image forming apparatus.

  2. Description of the Related Art In an image forming apparatus capable of forming a color image by an electrophotographic method, the charge amount of toner changes due to a change in temperature and humidity in an installation environment. As a result, the output characteristics of the image forming apparatus change, and the color reproducibility of the printed matter is reduced. On the other hand, there is a configuration in which a plurality of patches corresponding to a plurality of color data are printed, and a calibration process for suppressing a decrease in color reproducibility can be executed based on a colorimetric result for each of the printed patches. It is known as a related technique (see Patent Document 1). Specifically, in the related art, correction data capable of correcting a deviation between a color measurement result and color data for each printed patch is generated, and the print data is corrected by the generated correction data. .

JP 2012-119799 A

  However, in the related art described above, the correction data corresponding to a color different from the color of the printed patch is generated by interpolation based on the correction data corresponding to the color of the printed patch. Therefore, in the related art described above, it is necessary to print a large number of patches in order to improve the accuracy of the correction using the correction data.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus and a voltage adjustment method capable of suppressing a decrease in color reproducibility with a small number of patches.

  An image forming apparatus according to one aspect of the present invention includes a developing unit, a patch printing unit, a colorimetric unit, a first determination processing unit, and a first adjustment processing unit. The developing unit is provided for each color of CMYK, and develops an electrostatic latent image formed on the image carrier in response to application of a voltage. The patch printing unit includes a first patch corresponding to predetermined first color data including any two color components of the K color component and CMY, and a preset patch corresponding to an output characteristic of the own device. A second patch corresponding to the second color data including a CMYK color space having the same conversion value as the first color data by color conversion from the CMYK color space based on the profile to the predetermined color space is printed. . The colorimeter measures the color of each of the first patch and the second patch printed by the patch printing unit. The first determination processing unit determines whether a difference between the colorimetric values of the first patch and the second patch by the colorimetric unit is within a first allowable value set in advance. The first adjustment processing unit is configured to, when the first determination processing unit determines that the difference between the colorimetric values of the first patch and the second patch exceeds the first allowable value, perform the CMYK operation. By adjusting the applied voltage in each of the developing units corresponding to the respective colors, the difference between the colorimetric values of the first patch and the second patch is reduced to within the first allowable value.

  A voltage adjusting method according to another aspect of the present invention includes an image forming apparatus provided corresponding to each color of CMYK and including a developing unit that develops an electrostatic latent image formed on an image carrier in response to application of a voltage. And a first patch corresponding to predetermined first color data including any two color components of the K color component and CMY, and a preset profile corresponding to the output characteristic of the own device. Printing a second patch corresponding to the second color data that has the same conversion value as the first color data from the CMYK color space based on the color conversion to the predetermined color space and includes the CMY color components. Measuring the color of each of the printed first patch and the second patch, and determining the difference between the colorimetric values of the first patch and the second patch in a first tolerance set in advance. Determine if it is within the value And when it is determined that the difference between the colorimetric values of the first patch and the second patch exceeds the first allowable value, the developing unit corresponding to each color of CMYK Adjusting the applied voltage to reduce the difference between the colorimetric values of each of the first patch and the second patch to within the first allowable value.

  According to the present invention, an image forming apparatus and a voltage adjustment method capable of suppressing a decrease in color reproducibility with a small number of patches are realized.

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration of an image forming unit and an intermediate transfer device of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a block diagram illustrating a system configuration of the image forming apparatus according to the embodiment of the present invention. FIG. 4 is a diagram illustrating an example of color data used in the image forming apparatus according to the embodiment of the present invention. FIG. 5 is a diagram illustrating an example of a patch printed by the image forming apparatus according to the embodiment of the present invention. FIG. 6 is a flowchart illustrating an example of a voltage adjustment process performed by the image forming apparatus according to the embodiment of the present disclosure.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. Note that the following embodiments are merely examples embodying the present invention, and do not limit the technical scope of the present invention.

[Schematic Configuration of Image Forming Apparatus 10]
First, a schematic configuration of an image forming apparatus 10 according to an embodiment of the present invention will be described with reference to FIGS. Here, FIG. 1 is a schematic sectional view showing the configuration of the image forming apparatus 10. FIG. 2 is a schematic sectional view showing the configuration of the image forming units 31 to 34 and the intermediate transfer device 36.

  The image forming apparatus 10 is a multifunction peripheral having a plurality of functions such as a scan function, a facsimile function, and a copy function, in addition to a print function of forming a color image by an electrophotographic method based on image data. The present invention is applicable to an image forming apparatus such as a printer, a facsimile, and a copying machine that can form a color image by an electrophotographic method.

  As shown in FIGS. 1 and 3, the image forming apparatus 10 includes an ADF 1, an image reading unit 2, an image forming unit 3, a sheet conveying unit 4, a control unit 5, an operation display unit 6, a storage unit 7, and a conveying image. A reading unit 8 is provided.

  The ADF 1 is an automatic document feeder that includes a document setting unit, a plurality of conveyance rollers, a document presser, and a paper discharge unit, and conveys a document read by the image reading unit 2. The image reading unit 2 includes a document table, a light source, a plurality of mirrors, an optical lens, and a charge coupled device (CCD), and can read image data from a document.

  The control unit 5 includes control devices such as a CPU, a ROM, and a RAM (not shown). The CPU is a processor that executes various arithmetic processing. The ROM is a non-volatile storage unit in which information such as a control program for causing the CPU to execute various processes is stored in advance. The RAM is a volatile storage unit used as a temporary storage memory (work area) for various processes executed by the CPU. In the control unit 5, the CPU executes various control programs stored in the ROM in advance. Thus, the control unit 5 controls the image forming apparatus 10 as a whole. The control unit 5 may be configured by an electronic circuit such as an integrated circuit (ASIC), and is a control unit provided separately from a main control unit that controls the image forming apparatus 10 in an integrated manner. May be.

  The operation display unit 6 includes a display unit such as a liquid crystal display that displays various information according to a control instruction from the control unit 5, and an operation key or a touch panel that inputs various information to the control unit 5 according to a user operation. Operation unit.

  The storage unit 7 is a storage device such as a solid state drive (SSD) or a hard disk drive (HDD). The storage unit 7 stores image data and the like read by the image reading unit 2.

  The image forming unit 3 can execute an image forming process (printing process) for forming a color or monochrome image by an electrophotographic method based on the image data read by the image reading unit 2. Further, the image forming section 3 can execute the printing process based on image data input from an information processing device such as an external personal computer.

  Specifically, as shown in FIGS. 1 and 2, the image forming unit 3 includes a plurality of image forming units 31 to 34, an optical scanning device 35, an intermediate transfer device 36, a secondary transfer roller 37, and a fixing unit 38. Is provided.

  The image forming unit 31 is an electrophotographic image forming unit corresponding to Y (yellow), the image forming unit 32 is C (cyan), the image forming unit 33 is M (magenta), and the image forming unit 34 is K (black). is there. As shown in FIGS. 1 and 2, the image forming units 31 to 34 are arranged in the order of yellow, cyan, magenta, and black along the transport direction D1 of the intermediate transfer belt 361 of the intermediate transfer device 36.

  As shown in FIGS. 1 and 2, each of the image forming units 31 to 34 includes a photosensitive drum 30A, a charging roller 30B, a developing unit 30C, a primary transfer roller 30D, a drum cleaning unit 30E, and a toner container 30F. The toner container 30F of the image forming unit 31 contains yellow toner. The toner container 30F of the image forming unit 32 contains cyan toner. The toner container 30F of the image forming unit 33 contains magenta toner. The toner container 30F of the image forming unit 34 contains black toner. Each of the image forming units 31 to 34 forms a toner image of a corresponding color using the toner stored in the toner container 30F.

  An electrostatic latent image is formed on the surface of the photosensitive drum 30A (an example of the image carrier of the present invention). The charging roller 30B charges the surface of the photosensitive drum 30A. The developing unit 30C develops the electrostatic latent image formed on the surface of the photosensitive drum 30A according to the application of the voltage. Specifically, as shown in FIG. 2, the developing unit 30C includes a developing roller 30C1. The developing roller 30C1 supplies the toner in the developing unit 30C to the surface of the photosensitive drum 30A according to the application of the voltage. Toner is supplied to the developing unit 30C from the toner container 30F. The primary transfer roller 30D transfers the toner image formed on the surface of the photosensitive drum 30A to the intermediate transfer belt 361 of the intermediate transfer device 36. The drum cleaning unit 30E cleans the surface of the photosensitive drum 30A after the transfer by the primary transfer roller 30D.

  The optical scanning device 35 forms an electrostatic latent image on the surface of each of the photosensitive drums 30A of the image forming units 31 to 34.

  The intermediate transfer device 36 transfers the toner image transferred from each of the photosensitive drums 30A of the image forming units 31 to 34 to the intermediate transfer belt 361 onto a sheet by the secondary transfer roller 37 (see FIG. 1 or FIG. 2). Transport to As shown in FIG. 2, the intermediate transfer device 36 includes an intermediate transfer belt 361, a driving roller 362, a tension roller 363, and a belt cleaning unit 364. The intermediate transfer belt 361 is an endless belt member onto which the toner image formed on the surface of each of the photosensitive drums 30A is transferred. The intermediate transfer belt 361 is stretched by a driving roller 362 and a stretching roller 363. The drive roller 362 rotates the intermediate transfer belt 361 along the transport direction D1 by rotating with a driving force supplied from a power source (not shown). The belt cleaning unit 364 cleans the surface of the intermediate transfer belt 361 after the transfer by the secondary transfer roller 37.

  The secondary transfer roller 37 transfers the toner image transferred onto the surface of the intermediate transfer belt 361 by the image forming units 31 to 34 to a sheet.

  The fixing unit 38 melts and fixes the toner image transferred to the sheet by the secondary transfer roller 37 to the sheet. As shown in FIG. 1, the fixing unit 38 includes a fixing roller 381 and a pressure roller 382. The fixing roller 381 is provided in contact with the pressure roller 382, and heats the toner image transferred to the sheet to fix it on the sheet. The pressure roller 382 presses a sheet passing through a fixing position P2 (see FIG. 1), which is a contact portion formed between the pressure roller 381 and the fixing roller 381.

  The sheet transport unit 4 transports a sheet on which an image is printed by the image forming unit 3. Specifically, as shown in FIG. 1, the sheet transport unit 4 includes a transport path 40, a paper feed cassette 41, a pickup roller 42, a first transport roller 43, a registration roller 44, a second transport roller 45, and a discharge roller 46. , And a sheet discharging section 47. The transport path 40 is a sheet movement path that connects the sheet cassette 41 and the sheet discharge unit 47. In the sheet transport unit 4, the pickup roller 42, the first transport roller 43, the registration roller 44, the second transport roller 45, and the discharge roller 46 rotate by a driving force supplied from a drive source (not shown). Thus, the sheets stored in the sheet cassette 41 are conveyed in the conveying direction D2 and discharged to the sheet discharge unit 47. As shown in FIG. 1, the secondary transfer roller 37 of the image forming unit 3 is provided downstream of the registration roller 44 in the transport path 40 in the transport direction D2. Further, the fixing unit 38 of the image forming unit 3 is provided on the transport path 40 downstream of the secondary transfer roller 37 in the transport direction D2.

  The image forming unit 3 forms a color image on a sheet supplied from the sheet conveying unit 4 in the following procedure. The sheet on which an image is formed is a sheet material such as paper, coated paper, postcard, envelope, and OHP sheet.

  First, in the image forming unit 31, the photosensitive drum 30A is uniformly charged to a predetermined potential by the charging roller 30B. Next, the light based on the image data is irradiated on the surface of the photosensitive drum 30A by the optical scanning device 35. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 30A. Then, the electrostatic latent image on the photosensitive drum 30A is developed (visualized) as a yellow toner image by the developing unit 30C. Subsequently, the yellow toner image formed on the photosensitive drum 30A is transferred to the intermediate transfer belt 361 by the primary transfer roller 30D. On the other hand, the toner remaining on the surface of the photosensitive drum 30A is removed by the drum cleaning unit 30E.

  Next, also in the image forming units 32 to 34, a toner image is formed on the photosensitive drum 30A of each of the image forming units 32 to 34 according to the same processing procedure as the image forming unit 31, and is transferred to the intermediate transfer belt 361. You. As a result, yellow, cyan, magenta, and black toner images are sequentially transferred onto the surface of the intermediate transfer belt 361 in a superimposed manner. The toner image transferred to the surface of the intermediate transfer belt 361 is transported by the intermediate transfer device 36 to a transfer position P1 by the secondary transfer roller 37.

  On the other hand, the sheet transport unit 4 supplies the sheet to the transfer position P1 in accordance with the timing at which the intermediate transfer device 36 transports the toner image to the transfer position P1. Specifically, the pick-up roller 42 is, of the sheets accommodated in the paper feed cassette 41, most lifted to a position where it comes into contact with the pickup roller 42 by a lift plate (not shown) provided at the bottom of the paper feed cassette 41. The upper layer sheet is sent out to the transport path 40. The sheet delivered to the transport path 40 by the pickup roller 42 is transported to the registration roller 44 by the first transport roller 43.

  Then, the registration roller 44 sends the sheet to the transfer position P1 in synchronization with the transport timing. Specifically, the sheet sending timing of the registration roller 44 is controlled by the control unit 5 based on an electric signal output from a registration sensor (not shown) provided upstream of the registration roller 44 in the conveyance path 40 in the conveyance direction D2 with respect to the conveyance path 40. It is determined. The secondary transfer roller 37 transfers the toner image formed on the intermediate transfer belt 361 to the sheet sent from the registration roller 44 at the transfer position P1.

  The sheet on which the toner image has been transferred by the secondary transfer roller 37 is transported to a fixing position P2 by the fixing unit 38. The toner image transferred to the sheet is heated by the fixing unit 38 when the sheet passes the fixing position P2. Thereby, the toner image is fixed on the sheet. Thereafter, the sheet on which the toner image has been fixed is discharged to the discharge roller 46 by the second transport roller 45. The discharge roller 46 discharges the sheet to the sheet discharge unit 47.

  Meanwhile, in the image forming apparatus 10, the charge amount of the toner changes due to a change in temperature and humidity in an installation environment. As a result, the output characteristics of the image forming apparatus 10 change, and the color reproducibility of the printed matter decreases. On the other hand, there is a configuration in which a plurality of patches corresponding to a plurality of color data are printed, and a calibration process for suppressing a decrease in color reproducibility can be executed based on a colorimetric result for each of the printed patches. Known as related technology. Specifically, in the related art, correction data capable of correcting a deviation between a color measurement result and color data for each printed patch is generated, and the print data is corrected by the generated correction data. .

  However, in the related art described above, the correction data corresponding to a color different from the color of the printed patch is generated by interpolation based on the correction data corresponding to the color of the printed patch. Therefore, in the related art described above, it is necessary to print a large number of patches in order to improve the accuracy of the correction using the correction data. On the other hand, in the image forming apparatus 10 according to the embodiment of the present invention, as described below, it is possible to suppress a decrease in color reproducibility with a small number of patches.

  The transport image reading unit 8 is provided downstream of the fixing position P2 in the transport path 40 in the transport direction D2, and reads an image from a sheet transported by the sheet transport unit 4. Here, the transport image reading unit 8 is an example of the image reading unit in the present invention.

  Specifically, the transport image reading unit 8 includes an image sensor 81 as shown in FIG. The image sensor 81 is an image sensor such as a contact image sensor (CIS) including a light emitting unit and a light receiving unit. The light emitting unit emits light to an image formed on the sheet. The light receiving unit receives light emitted from the light emitting unit and reflected by an image on a sheet, and outputs an electric signal according to a received light amount. The transport image reading unit 8 converts the electric signal output from the light receiving unit of the image sensor 81 into a digital signal by an analog front-end circuit (not shown) to obtain image data. The image data acquired by the transport image reading unit 8 is output to the control unit 5.

  Here, as shown in FIG. 1, the imaging element 81 is arranged at a position separated from the fixing position P2 in the transport path 40 by a predetermined distance 81A in the transport direction D2. Thus, the deterioration of the image sensor 81 due to the heat generated from the fixing unit 38 is suppressed. Note that the distance 81A may be appropriately set in consideration of the influence of heat generated from the fixing unit 38 on the image sensor 81 and the like. Further, the image sensor 81 is arranged at a position separated from the position of the discharge roller 46 in the transport path 40 by a predetermined distance in consideration of the influence of disturbance light.

  On the other hand, in the ROM of the control unit 5, a voltage adjustment program for causing the CPU of the control unit 5 to execute a voltage adjustment process (see a flowchart of FIG. 6) described later is stored in advance. Note that the voltage adjustment program may be recorded on a computer-readable recording medium such as a CD, a DVD, or a flash memory, and may be installed from the recording medium into a storage unit such as the storage unit 7.

  Then, as shown in FIG. 3, the control unit 5 includes a patch printing unit 51, a colorimetric unit 52, a second determination processing unit 53, a second adjustment processing unit 54, a first determination processing unit 55, a first adjustment process. Unit 56, a third determination processing unit 57, a notification processing unit 58, and a third adjustment processing unit 59. Specifically, the CPU of the control unit 5 executes the voltage adjustment program stored in the ROM. Thereby, the control unit 5 includes the patch printing unit 51, the color measurement unit 52, the second determination processing unit 53, the second adjustment processing unit 54, the first determination processing unit 55, the first adjustment processing unit 56, and the third determination process. It functions as the unit 57, the notification processing unit 58, and the third adjustment processing unit 59.

  The patch printing unit 51 includes a first patch corresponding to the predetermined first color data, a second patch corresponding to the predetermined second color data, and a third patch corresponding to the predetermined third color data. Print the patch. Here, the first color data, the second color data, and the third color data are data indicating colors represented in a CMYK color space. In the following, the first patch, the second patch, and the third patch may be collectively referred to as patches.

  Specifically, the first color data includes any two color components of a K color component of a predetermined reference density and CMY. That is, the density of any one of the CMY color components in the first color data is zero (no color component). Further, the second color data includes CMY color components. That is, the density of the K color component in the second color data is zero (no color component). Further, the third color data includes only the K color component of the reference density. That is, in the third color data, the density of each color component of CMY is zero (no color component). For example, the reference concentration is 50 percent as a percentage.

  Here, in the image forming apparatus 10, a preset output profile corresponding to the output characteristic of the image forming apparatus 10 is stored in the storage unit 7. The output profile converts data representing a color expressed in the CMYK color space, which is a device-dependent color that depends on the output characteristics of the image forming apparatus 10, into Lab, a non-device-dependent color that does not depend on the output characteristics of the image forming apparatus 10. This is data used for the first color conversion for converting into data indicating a color expressed in a color space. For example, when the image forming apparatus 10 is manufactured, the output profile is created based on a color measurement result of a color of a printed matter printed by the image forming apparatus 10 under predetermined environmental conditions. Here, the output profile is an example of a preset profile in the present invention. The Lab color space is an example of a predetermined color space in the present invention. Further, the first color conversion is an example of the color conversion in the present invention. The first color conversion is for converting data indicating a color expressed in a CMYK color space into data indicating a color expressed in a non-device-dependent color space different from the Lab color space. Is also good.

  In the image forming apparatus 10, the first color data and the second color data are determined so that the converted values after the first color conversion based on the output profile are the same. Therefore, in the image forming apparatus 10, when the output characteristics at the time of printing are the same as the output characteristics at the time of creating the output profile, the color of the printed matter printed based on the first color data and the second color data And the color of the printed matter printed on the basis of the same color.

  For example, in the image forming apparatus 10, the first color data having three different color components is stored in the storage unit 7. In the image forming apparatus 10, three second color data corresponding to three first color data and one third color data are stored in the storage unit 7. The patch printing unit 51 corresponds to three of the first patches corresponding to the three first color data, three of the second patches corresponding to the three second color data, and one of the third color data. One third patch to be printed is printed. That is, in the image forming apparatus 10, the patch printing unit 51 prints a total of seven patches.

  Here, FIG. 4 shows, as an example of the first color data, the second color data, and the third color data, first color data A11 to A13, second color data A21 to A23, and third color data. A31 is shown. In FIG. 4, the density of the color component included in each color data is shown as a percentage. The first color data A11 and the second color data A21 are determined so that the conversion values after the first color conversion based on the output profile are the same. Further, the first color data A12 and the second color data A22 are determined such that the converted values after the first color conversion based on the output profile are the same. Further, the first color data A13 and the second color data A23 are determined so that the converted values after the first color conversion based on the output profile become the same.

  For example, when a predetermined printing condition is satisfied, the patch printing unit 51 prints the first patch, the second patch, and the third patch.

  For example, the printing condition is that an instruction to execute a printing process based on image data is input in the image forming apparatus 10 after a predetermined time has elapsed from the time of printing the previous patch. When the printing condition is satisfied, the patch printing unit 51 prints a patch at a predetermined specific position on a sheet on which an image is formed in the printing process. Specifically, the specific position is a position outside the image forming area based on the image data on the sheet. When an image is formed on a plurality of sheets in the printing process, the patch printing unit 51 may print a patch on any one of the sheets.

  Here, FIG. 5 shows a first patch B11 to B13, a second patch B21 to B23, and a third patch B31 as examples of patches printed on a sheet. In FIG. 5, the image forming area X11 on the sheet X10 is indicated by a two-dot chain line. The first patches B11 to B13 are patches corresponding to the first color data A11 to A13. The second patches B21 to B23 are patches corresponding to the second color data A21 to A23. The third patch B31 is a patch corresponding to the third color data A31.

  Note that the patch printing unit 51 may print only a plurality of the first patches and a plurality of the second patches. In this case, the density of the K color component included in the first color data may be different from each other in the plurality of first color data. Further, the patch printing unit 51 may print one first patch and one second patch.

  Further, the printing condition may be that an instruction to execute the printing process is input. Further, the print condition may be that a predetermined time has elapsed since the previous patch was printed. Further, the printing conditions may be different from those described above.

  The colorimeter 52 measures the colors of the first patch, the second patch, and the third patch printed by the patch printing unit 51. Specifically, the colorimetric unit 52 acquires data indicating the color of each of the first patch, the second patch, and the third patch.

  For example, the colorimetric section 52 performs the first patch, the second patch, and the second patch based on image data read from the sheet on which the first patch, the second patch, and the third patch are printed by the transport image reading section 8. The color of each of the two patches and the third patch is measured.

  Here, in the image forming apparatus 10, a preset input profile corresponding to the input characteristics of the transport image reading unit 8 is stored in the storage unit 7. The input profile converts data representing a color expressed in the RGB color space, which is a device-dependent color depending on the input characteristics of the transport image reading unit 8, into non-device-dependent colors that do not depend on the input characteristics of the transport image reading unit 8. This is data used for the second color conversion for converting into data indicating a color expressed in a certain Lab color space.

  For example, the colorimetric unit 52 extracts a plurality of pixel data constituting the image of the first patch from the image data read by the transport image reading unit 8. Subsequently, the colorimetric unit 52 calculates an average value of the RGB values in the extracted plurality of pixel data. Then, the colorimetric unit 52 acquires a Lab value acquired by performing the second color conversion on the calculated average value of the RGB values as data indicating the color of the first patch. Similarly, the colorimetric unit 52 acquires data indicating the color of the second patch and data indicating the color of the third patch.

  Note that the colorimetric unit 52 performs the first patch, the second patch, and the second patch based on image data read from the sheet on which the first patch, the second patch, and the third patch are printed by the image reading unit 2. The color of each of the patch and the third patch may be measured.

  The second determination processing unit 53 determines that the difference between the converted value of the third color data by the first color conversion and the colorimetric value of the third patch by the colorimetric unit 52 is within a preset second allowable value. Is determined. For example, when both the conversion value of the third color data by the first color conversion and the colorimetric value of the third patch by the colorimetric unit 52 are Lab values, the second determination processing unit 53 It is determined whether or not the difference is within the second allowable value.

  The second adjustment processing unit 54 is configured to determine that the second determination processing unit 53 determines that the difference between the converted value of the third color data and the colorimetric value of the third patch exceeds the second allowable value. In addition, the applied voltage in the developing unit 30C of the image forming unit 34 corresponding to the color K is adjusted, and the difference between the converted value of the third color data and the colorimetric value of the third patch is set in the second allowable range. A second adjustment process for reducing the value within the value is executed.

  For example, in the second adjustment process, when the L value of the colorimetric value of the third patch is higher than the L value of the converted value of the third color data, the setting of the applied voltage in the developing unit 30C of the image forming unit 34 The value is increased by a predetermined adjustment value. On the other hand, in the second adjustment process, when the L value of the colorimetric value of the third patch is lower than the L value of the converted value of the third color data, the setting of the applied voltage in the developing unit 30C of the image forming unit 34 The value is reduced by the adjustment value. For example, the adjustment value is 5 volts.

  In the second adjustment process, after the set value of the applied voltage in the developing unit 30C of the image forming unit 34 is changed, a patch is printed again by the patch printing unit 51, and the printed patch is The color is measured by 52. Then, the second determination processing unit 53 determines whether the difference between the colorimetric value of the third patch reprinted and the converted value of the third color data is within the second allowable value. If it is determined that the value exceeds the second allowable value, the set value of the applied voltage is changed again. The processing described above is performed until the second determination processing unit 53 determines that the difference between the colorimetric value of the third patch and the converted value of the third color data is within the second allowable value. ,Repeated.

  Note that the second adjustment processing unit 54 may acquire the increase / decrease value of the applied voltage based on the colorimetric value of the third patch. For example, the second adjustment processing unit 54 converts the colorimetric value of the third patch expressed in the Lab color space into data expressed in the CMYK color space using the output profile. Subsequently, the second adjustment processing unit 54 calculates a difference between the density of the K color component in the converted data and the density of the K color component of the third color data, and the area of the third patch. The amount of toner shortage or excess in the printed third patch is calculated. Then, the second adjustment processing unit 54 is calculated based on table data indicating the relationship between the increase / decrease value of the applied voltage previously stored in the storage unit 7 and the increase / decrease value of the toner amount supplied by the developing unit 30C. An increase / decrease value of the applied voltage corresponding to the shortage amount or the excess amount is obtained.

  When the patch printing unit 51 does not print the third patch, the control unit 5 may not include the second determination processing unit 53 and the second adjustment processing unit 54.

  The first determination processing unit 55 determines whether or not the difference between the colorimetric values of the first patch and the second patch by the colorimetric unit 52 is within a first allowable value set in advance.

  Specifically, the first determination processing unit 55 determines that the difference between the converted value of the third color data and the colorimetric value of the third patch is within the second allowable value by the second determination processing unit 53. The difference between the colorimetric values of the first patch and the second patch for each pair of patches including the first patch and the second patch corresponding to the first patch is equal to the first tolerance. It is determined whether it is within the value.

  For example, the first determination processing unit 55 determines that the colorimetric values of each of the first patch not including the Y color component and the second patch corresponding to the first patch not including the Y color component are Lab colors. If the data is expressed in space, it is determined whether or not the difference between the two b values is within the first allowable value.

  Further, the first determination processing unit 55 determines that the colorimetric values of each of the first patch not including the C color component and the second patch corresponding to the first patch not including the C color component are Lab colors. If the data is expressed in space, it is determined whether or not the difference between the L values is within the first allowable value.

  Further, the first determination processing unit 55 determines that the colorimetric values of each of the first patch not including the M color component and the second patch corresponding to the first patch not including the M color component are Lab colors. If the data is expressed in space, it is determined whether or not the difference between the two a values is within the first allowable value. The first allowable value may be a different value for each of the L value, the a value, and the b value.

  When the first determination processing unit 55 determines that the difference between the colorimetric values of the first patch and the second patch exceeds the first allowable value, the first adjustment processing unit 56 performs a CMYK operation. By adjusting the applied voltage in each of the developing units 30C corresponding to the respective colors, the difference between the colorimetric values of the first patch and the second patch is reduced to within the first allowable value.

  Specifically, the first adjustment processing unit 56 determines the difference between the colorimetric values of the first patch and the second patch for any one or a plurality of the pair of patches by the first determination processing unit 55. When it is determined that the value exceeds the first allowable value, the development corresponding to a color component not included in the first patch is performed for each of the pair of patches determined to exceed the first allowable value. A first adjustment process of adjusting the applied voltage in the unit 30C to reduce the difference between the colorimetric values of the first patch and the second patch within the first allowable value is performed.

  For example, in the first adjustment process, the b value of the colorimetric value of the first patch that does not include the Y color component is equal to the colorimetric value of the second patch that corresponds to the first patch that does not include the Y color component. Is higher than the b value, the set value of the applied voltage in the developing unit 30C of the image forming unit 31 is increased by the adjustment value. On the other hand, in the first adjustment process, the b value of the colorimetric value of the first patch that does not include the Y color component is equal to the colorimetric value of the second patch that corresponds to the first patch that does not include the Y color component. Is smaller than the b value, the set value of the applied voltage in the developing unit 30C of the image forming unit 31 is reduced by the adjustment value.

  In the first adjustment processing, the L value of the colorimetric value of the first patch that does not include the C color component is equal to the colorimetric value of the second patch that corresponds to the first patch that does not include the C color component. Is higher than the L value, the set value of the applied voltage in the developing unit 30C of the image forming unit 32 is reduced by the adjustment value. On the other hand, in the first adjustment process, the L value of the colorimetric value of the first patch that does not include the C color component is the colorimetric value of the second patch that corresponds to the first patch that does not include the C color component. Is lower than the L value, the set value of the applied voltage in the developing unit 30C of the image forming unit 32 is increased by the adjustment value.

  Further, in the first adjustment processing, the a value of the colorimetric value of the first patch that does not include the M color component is equal to the colorimetric value of the second patch that corresponds to the first patch that does not include the M color component. Is higher than the value a, the set value of the applied voltage in the developing unit 30C of the image forming unit 33 is increased by the adjustment value. On the other hand, in the first adjustment process, the a value of the colorimetric value of the first patch that does not include the M color component is equal to the colorimetric value of the second patch that corresponds to the first patch that does not include the M color component. Is lower than the value a, the set value of the applied voltage in the developing unit 30C of the image forming unit 33 is reduced by the adjustment value.

  In the first adjustment process, after the set value of the applied voltage in each of the developing units 30C is changed, a patch is printed again by the patch printing unit 51, and the printed patch is measured by the colorimetric unit 52. Is done. Then, the first determination processing unit 55 determines whether or not the difference between the colorimetric values of the first patch and the second patch printed again is within the first allowable value. If it is determined that the value exceeds one allowable value, the set value of the applied voltage is changed again. In the processing described above, the first determination processing unit 55 determines that the difference between the colorimetric values of the first patch and the second patch for all the pair of patches is within the first allowable value. Until it is repeated.

  The third determination processing unit 57 determines that the difference between the colorimetric values of the first patch and the second patch for all the pair of patches is within the first tolerance by the first adjustment processing unit 56. In this case, a difference between a colorimetric value of the first patch by the colorimetric unit 52 and a conversion value of the first color data by the first color conversion is set in advance for each of the pair of patches. It is determined whether it is within the value.

  For example, when the converted value of the first color data and the colorimetric value of the first patch are both data expressed in the Lab color space, the third determination processing unit 57 determines the L value, the a value, It is determined whether or not each difference of the b value is within the third allowable value.

  The third determination processing unit 57 determines, for each of the pair of patches, the difference between the colorimetric value of the second patch by the colorimetric unit 52 and the converted value of the second color data by the first color conversion. It may be determined whether the value is within three allowable values.

  The notification processing unit 58 determines whether the difference between the colorimetric value of the first patch and the converted value of the first color data for any one or more of the pair of patches by the third determination processing unit 57 is the third allowable value. If it is determined that the value exceeds the value, a message to prompt the user to change one or both of the environmental temperature and the environmental humidity is issued. For example, the notification processing unit 58 causes the operation display unit 6 to display the message.

  In addition, the notification processing unit 58 determines the difference between the colorimetric value of the second patch and the converted value of the second color data for any one or a plurality of the pair of patches by the third determination processing unit 57. The message may be notified when it is determined that the number exceeds the three allowable values.

  When the message is notified by the notification processing unit 58, the third adjustment processing unit 59 adjusts the applied voltage in each of the developing units 30C corresponding to each color of CMY, and exceeds the third allowable value. Executing a third adjustment process for reducing the difference between the colorimetric value of the first patch of the pair of patches determined as above and the converted value of the first color data.

  For example, in the third adjustment process, when the a value of the converted value of the first color data that does not include the Y color component is higher than the a value of the colorimetric value of the first patch that does not include the Y color component, The set value of the applied voltage in the developing unit 30C of the image forming unit 33 is reduced by a preset value. On the other hand, in the third adjustment process, when the a value of the converted value of the first color data not including the Y color component is lower than the a value of the colorimetric value of the first patch not including the Y color component, The set value of the applied voltage in the developing unit 30C of the image forming unit 33 is increased by a preset value.

  In the third adjustment process, when the b value of the converted value of the first color data not including the Y color component is higher than the colorimetric value b of the first patch not including the Y color component, The set value of the applied voltage in the developing unit 30C of the forming unit 32 is increased by a preset value. On the other hand, in the third adjustment process, when the b value of the converted value of the first color data that does not include the Y color component is lower than the b value of the colorimetric value of the first patch that does not include the Y color component, The set value of the applied voltage in the developing unit 30C of the image forming unit 32 is reduced by a preset value.

  In the third adjustment process, when the a value of the converted value of the first color data that does not include the C color component is higher than the a value of the colorimetric value of the first patch that does not include the C color component, The set value of the applied voltage in the developing unit 30C of the image forming unit 33 is increased by a preset value. On the other hand, in the third adjustment process, when the a value of the converted value of the first color data that does not include the C color component is lower than the a value of the colorimetric value of the first patch that does not include the C color component, The set value of the applied voltage in the developing unit 30C of the image forming unit 33 is reduced by a preset value.

  In the third adjustment processing, when the b value of the conversion value of the first color data not including the C color component is higher than the b of the colorimetric value of the first patch not including the C color component, The set value of the applied voltage in the developing unit 30C of the forming unit 31 is increased by a preset value. On the other hand, in the third adjustment process, when the b value of the converted value of the first color data not including the C color component is lower than the b value of the colorimetric value of the first patch not including the C color component, The set value of the applied voltage in the developing unit 30C of the image forming unit 31 is reduced by a preset value.

  In the third adjustment process, when the a value of the converted value of the first color data not including the M color component is higher than the a value of the colorimetric value of the first patch not including the M color component, The set value of the applied voltage in the developing unit 30C of the image forming unit 32 is reduced by a preset value. On the other hand, in the third adjustment process, when the a value of the converted value of the first color data that does not include the M color component is lower than the a value of the colorimetric value of the first patch that does not include the M color component, The set value of the applied voltage in the developing unit 30C of the image forming unit 32 is increased by a preset value.

  In the third adjustment process, when the b value of the converted value of the first color data not including the M color component is higher than the colorimetric value b of the first patch not including the M color component, The set value of the applied voltage in the developing unit 30C of the forming unit 31 is increased by a preset value. On the other hand, in the third adjustment processing, when the b value of the converted value of the first color data not including the M color component is lower than the b value of the colorimetric value of the first patch not including the M color component, The set value of the applied voltage in the developing unit 30C of the image forming unit 31 is reduced by a preset value.

  The third adjustment processing unit 59 adjusts the applied voltage in each of the developing units 30C corresponding to each color of CMY, and converts the conversion value of the second color data by the first color conversion and the The difference from the colorimetric value of the second patch may be reduced.

  Further, the control unit 5 may not include the third adjustment processing unit 59. Further, the control unit 5 may not include the third determination processing unit 57, the notification processing unit 58, and the third adjustment processing unit 59.

[Voltage adjustment processing]
Hereinafter, an example of a procedure of a voltage adjustment process performed by the control unit 5 in the image forming apparatus 10 will be described with reference to FIG. Here, steps S11, S12,... Represent the numbers of the processing procedures (steps) executed by the control unit 5.

<Step S11>
First, in step S11, the control unit 5 determines whether or not the printing condition has been satisfied. For example, the control unit 5 determines that the printing condition has been satisfied when a predetermined time has elapsed since the previous patch was printed when the execution instruction of the printing process was input.

  Here, if the control unit 5 determines that the printing condition is satisfied (Yes in S11), the control unit 5 shifts the processing to step S12. If the printing conditions are not satisfied (No in S11), the control unit 5 waits for the satisfaction of the printing conditions in step S11.

<Step S12>
In step S12, the control unit 5 prints the three first patches, the three second patches, and the third patch. Here, the processes of step S11 and step S12 are executed by the patch printing unit 51 of the control unit 5.

  For example, the control unit 5 may store the first color data A11 to A13, the second color data A21 to A23, and the first color data A31 corresponding to the third color data A31 at the specific position on the sheet on which an image is formed in the printing process. The patches B11 to B13, the second patches B21 to B23, and the third patch B31 are printed.

<Step S13>
In step S13, the control unit 5 measures the colors of the first patch, the second patch, and the third patch printed in step S12. Here, the process of step S13 is executed by the colorimetric unit 52 of the control unit 5.

  For example, the control unit 5 performs the first patch B11 based on the image data read from the sheet on which the first patches B11 to B13, the second patches B21 to B23, and the third patch B31 are printed by the transport image reading unit 8. To B13, the second patches B21 to B23, and the third patch B31.

<Step S14>
In step S14, the control unit 5 determines that the difference between the converted value of the third color data by the first color conversion and the colorimetric value of the third patch obtained in step S13 is within the second allowable value. It is determined whether or not there is. Here, the process of step S14 is executed by the second determination processing unit 53 of the control unit 5.

  For example, the control unit 5 determines that the difference between the L value of the converted value of the third color data A31 by the first color conversion and the L value of the colorimetric value of the third patch B31 acquired in step S13 is the second allowable value. It is determined whether it is within.

  Here, if the control unit 5 determines that the difference between the converted value of the third color data and the colorimetric value of the third patch is within the second allowable value (Yes in S14), the process proceeds to step S14. The process proceeds to S16. If the difference between the converted value of the third color data and the colorimetric value of the third patch exceeds the second allowable value (No in S14), the control unit 5 proceeds to step S15. Migrate.

<Step S15>
In step S15, the control unit 5 executes the second adjustment processing. Here, the process of step S15 is executed by the second adjustment processing unit 54 of the control unit 5.

  According to the second adjustment process, the application of the voltage in the developing unit 30C of the image forming unit 34 is performed such that the difference between the converted value of the third color data and the colorimetric value of the third patch is within the second allowable value. The voltage is adjusted. Note that the processing of step S14 and step S15 may be omitted.

<Step S16>
In step S16, the control unit 5 determines whether or not the difference between the colorimetric values of the first patch and the second patch is within the first allowable value for all of the pair of patches. Here, the process of step S16 is executed by the first determination processing unit 55 of the control unit 5.

  For example, the control unit 5 determines whether the difference between the b value of the colorimetric value of the first patch B11 and the b value of the colorimetric value of the second patch B21 is within the first allowable value. Further, the control unit 5 determines whether the difference between the a value of the colorimetric value of the first patch B12 and the a value of the colorimetric value of the second patch B22 is within the first allowable value. Further, the control unit 5 determines whether or not the difference between the L value of the colorimetric value of the first patch B13 and the L value of the colorimetric value of the second patch B23 is within the first allowable value.

  Here, when the control unit 5 determines that the difference between the colorimetric values of the first patch and the second patch is within the first allowable value for all of the pair of patches (Yes in S16) ), And the process proceeds to step S18. In addition, for any one or more of the pair of patches, if the difference between the colorimetric values of the first patch and the second patch exceeds the first allowable value (No in S16), The control unit 5 shifts the processing to step S17.

<Step S17>
In step S17, the control unit 5 executes the first adjustment processing. Here, the process of step S17 is executed by the first adjustment processing unit 56 of the control unit 5.

  According to the first adjustment process, the application of each of the developing units 30C of the image forming units 31 to 33 is performed such that the difference between the colorimetric values of the first patch and the second patch is within the first allowable value. The voltage is adjusted. Here, as described above, in the image forming apparatus 10, when the output characteristics at the time of printing and the output characteristics corresponding to the output profile are the same, the printed matter printed based on the first color data is output. The color and the color of the printed matter printed based on the second color data are the same color. In other words, when the applied voltage in each of the developing units 30C is adjusted so that the color of the first patch and the color of the second patch become the same color, the printing caused by an environmental change or the like is performed. The deviation between the output characteristics at the time and the output characteristics corresponding to the output profile is reduced or eliminated. Therefore, the first adjustment process can reduce or eliminate the deviation between the output characteristics at the time of printing and the output characteristics corresponding to the output profile.

  Here, in the voltage adjustment processing, the second adjustment processing is executed before the first adjustment processing, and the applied voltage of the developing unit 30C corresponding to the K color component is adjusted first. Thereby, the number of the developing units 30C adjusted in the first adjustment process is reduced to three. Further, in the first adjustment process, each of the pair of patches determined to exceed the first allowable value in step S16 is processed by the developing unit 30C corresponding to a color component not included in the first patch. The applied voltage is adjusted. Therefore, the number of developing units 30C adjusted when the difference between the colorimetric values of the first patch and the second patch in one pair of patches is reduced to within the first allowable value is one. Has been reduced. Thereby, the number of the developing units 30C adjusted when the difference between the colorimetric values of the first patch and the second patch in one pair of patches is reduced to within the first allowable value is plural. It is possible to simplify the processing content of the first adjustment processing as compared with the configuration described below.

  If the set value of the density of the K color component (the reference density) included in the first color data is too low, the converted value after the first color conversion based on the output profile becomes the same. It is possible that there is no combination of the first color data and the second color data. When the reference density is too high, it is considered that the effect of suppressing a decrease in color reproducibility according to the present invention for low-density colors is reduced as compared with high-density colors. For example, it is desirable that the reference density is set within a range of 20% to 80%.

<Step S18>
In step S18, the control unit 5 determines that the difference between the colorimetric value of the first patch and the conversion value of the first color data by the first color conversion is within the third allowable value for all of the pair of patches. It is determined whether or not there is. Here, the process of step S18 is executed by the third determination processing unit 57 of the control unit 5.

  For example, the control unit 5 determines that the difference between the L value, the a value, and the b value in the colorimetric value of the first patch B11 and the converted value of the first color data A11 by the first color conversion is the third allowable value. It is determined whether it is within. Further, the control unit 5 determines that the difference between the L value, the a value, and the b value in the colorimetric value of the first patch B12 and the converted value of the first color data A12 by the first color conversion is the third allowable value. It is determined whether it is within. Further, the control unit 5 determines that the difference between the L value, the a value, and the b value in the colorimetric value of the first patch B13 and the converted value of the first color data A13 by the first color conversion is the third allowable value. It is determined whether it is within.

  Here, the control unit 5 determines that the difference between the colorimetric value of the first patch and the conversion value of the first color data by the first color conversion is within the third allowable value for all of the pair of patches. Is determined (Yes in S18), the process proceeds to step S11. In addition, for any one or a plurality of the pair of patches, a difference between a colorimetric value of the first patch and a conversion value of the first color data by the first color conversion exceeds the third allowable value. If it is (No in S18), the control unit 5 shifts the processing to step S19.

<Step S19>
In step S19, the control unit 5 notifies the message. For example, the control unit 5 causes the operation display unit 6 to display the message. Here, the process of step S19 is executed by the notification processing unit 58.

  If there is a large difference between the output characteristics at the time of printing and the output characteristics corresponding to the output profile caused by environmental changes and the like, the color of the printed matter printed based on the first color data and the color of the Even if the applied voltage in each of the developing units 30C is adjusted so that the color of the printed matter printed based on the two-color data is the same color, the output characteristics during printing and the output characteristics corresponding to the output profile It is conceivable that a difference between the two remains. On the other hand, in the voltage adjustment processing, a difference between a colorimetric value of the first patch and a conversion value of the first color data by the first color conversion is determined for any one or a plurality of the pair of patches. If the third tolerance is exceeded, the message is broadcast. Thereby, the user is prompted to change either or both of the environmental temperature and the environmental humidity due to the operation of the air conditioning and the like, and the output characteristics at the time of printing caused by the environmental changes and the output characteristics corresponding to the output profile are obtained. Can be reduced.

<Step S20>
In step S20, the control unit 5 executes the third adjustment processing. Here, the process of step S20 is executed by the third adjustment processing unit 59 of the control unit 5. The third adjustment process suppresses a decrease in color reproducibility for a tertiary color including at least the K color component. Note that the processing of steps S18 to S20 or the processing of step S20 may be omitted.

  As described above, in the voltage adjustment processing, the first patch corresponding to the first color data and the second patch corresponding to the second color data are printed. Then, the applied voltage in each of the developing units 30C is adjusted so that the color of the first patch and the color of the second patch become the same color. The deviation between the output characteristics and the output characteristics corresponding to the output profile is reduced or eliminated. Therefore, it is possible to suppress a decrease in color reproducibility with a small number of patches.

1: ADF
2: Image reading unit 3: Image forming unit 4: Sheet transport unit 5: Control unit 6: Operation display unit 7: Storage unit 8: Transport image reading unit 10: Image forming devices 31 to 34: Image forming unit 30A: Photoconductor Drum 30C: developing unit 38: fixing unit 40: transport path 51: patch printing unit 52: colorimetric unit 53: second determination processing unit 54: second adjustment processing unit 55: first determination processing unit 56: first adjustment processing Unit 57: third determination processing unit 58: notification processing unit 59: third adjustment processing unit 81: image sensor

Claims (8)

A developing unit that is provided for each of CMYK colors and develops an electrostatic latent image formed on the image carrier in response to application of a voltage;
A first patch corresponding to predetermined first color data including any two color components of the K color component and CMY, and a CMYK color space based on a preset profile corresponding to output characteristics of the own device A patch printing unit that prints a second patch corresponding to the second color data including each of the CMY color components, the conversion value of which is the same as the first color data and the conversion value by the color conversion from the color conversion to a predetermined color space;
A colorimeter that measures the color of each of the first patch and the second patch printed by the patch printing unit;
A first determination processing unit that determines whether a difference between colorimetric values of the first patch and the second patch by the colorimetric unit is within a first allowable value set in advance,
If the first determination processing unit determines that the difference between the colorimetric values of the first patch and the second patch exceeds the first allowable value, the developing unit corresponding to each color of CMYK A first adjustment processing unit that adjusts an applied voltage in each of the first and second patches to reduce a difference between colorimetric values of the first patch and the second patch to within the first allowable value;
An image forming apparatus comprising: The patch printing unit prints a plurality of the first patches and the second patches corresponding to the first patches,
The image forming apparatus according to claim 1. The first color data includes a K color component having a predetermined reference density,
The patch printing unit includes three first patches having different color components from each other, the second patch corresponding to each of the first patches, and third color data including only the K color component of the reference density. Print the corresponding third patch,
The colorimetric unit measures the color of each of the first patch, the second patch, and the third patch printed by the patch printing unit,
The image forming apparatus includes:
A second determination for determining whether a difference between a converted value of the third color data by the color conversion and a colorimetric value of the third patch by the colorimetric unit is within a second allowable value set in advance; A processing unit;
If the second determination processing unit determines that the difference between the converted value of the third color data and the colorimetric value of the third patch exceeds the second allowable value, the color corresponding to the color K is determined. A second adjustment processing unit that adjusts the applied voltage in the developing unit to reduce the difference between the converted value of the third color data and the colorimetric value of the third patch to within the second allowable value. Prepare,
The first determination processing unit is configured to determine whether a difference between the converted value of the third color data and the colorimetric value of the third patch is within the second allowable value by the second determination processing unit. The difference between the colorimetric values of the first patch and the second patch by the colorimetric unit for each pair of patches including the first patch and the second patch corresponding to the first patch is the first patch. Determine whether it is within the allowable value,
The first adjustment processing unit determines that a difference between the colorimetric values of the first patch and the second patch for any one or a plurality of the pair of patches by the first determination processing unit is the first allowable value. When it is determined that the value exceeds the first allowable value, the application in the developing unit corresponding to a color component not included in the first patch is performed for each of the pair of patches determined to exceed the first allowable value. Adjusting a voltage to reduce a difference between colorimetric values of the first patch and the second patch to within the first allowable value;
The image forming apparatus according to claim 2. When the first determination processing unit determines that the difference between the colorimetric values of each of the first patch and the second patch is within the first allowable value for all of the pair of patches, A third preset difference between a colorimetric value of the first patch or the second patch by the colorimetric unit and a converted value of the first color data or the second color data by the color conversion for each patch. A third determination processing unit that determines whether the value is within an allowable value;
A difference between a colorimetric value of the first patch or the second patch and a converted value of the first color data or the second color data for any one or a plurality of the pair of patches by the third determination processing unit; When it is determined that exceeds the third allowable value, the notification processing unit that notifies a message that prompts the user to change one or both of the environmental temperature and the environmental humidity,
The image forming apparatus according to claim 3, further comprising: When the message is notified by the notification processing unit, the applied voltage in each of the developing units corresponding to each color of CMY is adjusted, and the pair of patches determined to exceed the third allowable value is adjusted. And a third adjustment processing unit that reduces a difference between the colorimetric value of the first patch and the converted value of the first color data.
The image forming apparatus according to claim 4. A conveyance path on which a sheet on which an image is printed is conveyed;
A fixing unit for fixing the toner image transferred to the sheet,
An image reading unit provided downstream of the fixing position of the fixing unit in the conveyance path in the sheet conveyance direction from the fixing position, and reading a patch printed by the patch printing unit;
The color measurement unit measures the color of the patch based on image data read by the image reading unit,
The image forming apparatus according to claim 1. The patch printing unit prints a patch at a predetermined specific position on a sheet on which an image is formed in the printing process when a printing process based on the image data is performed,
The image forming apparatus according to claim 1. A voltage adjustment method which is provided in correspondence with each color of CMYK and is performed in an image forming apparatus including a developing unit that develops an electrostatic latent image formed on an image carrier in response to application of a voltage,
A first patch corresponding to predetermined first color data including any two color components of the K color component and CMY, and a CMYK color space based on a preset profile corresponding to output characteristics of the own device Printing a second patch corresponding to the second color data having the same conversion value as the first color data from the color conversion to the predetermined color space and including the respective CMY color components;
Measuring the color of each of the printed first patch and the second patch;
Determining whether or not the difference between the colorimetric values of the first patch and the second patch is within a first allowable value set in advance;
When it is determined that the difference between the colorimetric values of the first patch and the second patch exceeds the first allowable value, the voltage applied to each of the developing units corresponding to each color of CMYK is adjusted. Reducing the difference between the colorimetric values of the first patch and the second patch to within the first tolerance value;
Voltage adjustment method including:

Images