JP2018124336A - Image forming device and voltage adjustment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device with which it is possible to suppress a reduction in color reproducibility by a small number of patches, and a voltage adjustment method.SOLUTION: The image forming device comprises: a developing unit that corresponds to each color of CMYK; a patch printing unit for printing a first patch that corresponds to first color data A11-A13 and a second patch that corresponds to second color data A21-A23, the converted value of which are the same as the first color data A11-A13, the conversion here meaning a color conversion from a CMYK color space based on a profile that corresponds to the output characteristics of the own device to a Lab color space; and a first adjustment processing unit which, when a difference in colorimetric value between the first patch and the second patch exceeds a first permissible value, adjusts the applied voltage in each of the developing units that correspond to each color of CMYK and causes the difference in colorimetric value between the first patch and the second patch to be shrunk to within the first permissible value.SELECTED DRAWING: Figure 4

Description

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

  In an image forming apparatus capable of forming a color image by an electrophotographic method, the charge amount of toner changes due to changes in temperature and humidity in an installation environment. As a result, the output characteristics of the image forming apparatus are changed, and the color reproducibility of the printed matter is lowered. On the other hand, there is a configuration capable of executing a calibration process for printing a plurality of patches corresponding to a plurality of color data and suppressing a decrease in color reproducibility based on a colorimetric result for each printed patch. It is known as related technology (see Patent Document 1). Specifically, in the related technique, correction data that can correct a deviation between the colorimetric result and each 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, 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 correction using correction data.

  An object of the present invention is 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 an aspect of the present invention includes a developing unit, a patch printing unit, a color measurement unit, a first determination processing unit, and a first adjustment processing unit. The developing unit is provided corresponding to 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 corresponding to an output characteristic of the apparatus. The second patch corresponding to the second color data having the same conversion value by color conversion from the CMYK color space based on the profile to the predetermined color space as the first color data and including each color component of CMY is printed. . The color measuring unit measures colors of the first patch and the second patch printed by the patch printing unit. The first determination processing unit determines whether or not a difference between the colorimetric values of the first patch and the second patch by the colorimetric unit is within a preset first allowable value. The first adjustment processing unit, 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, the CMYK The applied voltage in each of the developing units corresponding to the respective colors is adjusted to reduce the difference between the colorimetric values of the first patch and the second patch within the first allowable value.

  A voltage adjustment method according to another aspect of the present invention is an image forming apparatus including a developing unit that is provided corresponding to each color of CMYK and that develops an electrostatic latent image formed on an image carrier in response to application of a voltage. The first patch corresponding to the predetermined first color data including any two color components of the K color component and CMY, and the preset profile corresponding to the output characteristic of the device itself Printing a second patch corresponding to second color data having a conversion value obtained by color conversion from a CMYK color space based on a predetermined color space to the predetermined color space and including the CMY color components; Measuring the color of each of the printed first patch and the second patch, and a first tolerance in which a difference between the colorimetric values of the first patch and the second patch is set in advance. Determine if it is within the value And when 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 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 showing a system configuration of the image forming apparatus according to the embodiment of the present invention. FIG. 4 is a diagram showing 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 voltage adjustment processing executed in the image forming apparatus according to the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.

[Schematic Configuration of Image Forming Apparatus 10]
First, a schematic configuration of the image forming apparatus 10 according to the embodiment of the present disclosure will be described with reference to FIGS. 1 to 3. Here, FIG. 1 is a schematic cross-sectional view showing the configuration of the image forming apparatus 10. FIG. 2 is a schematic cross-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 machine having a plurality of functions such as a scan function, a facsimile function, and a copy function as well as a print function for forming a color image by electrophotography based on image data. The present invention can be applied to an image forming apparatus capable of forming a color image by an electrophotographic method such as a printer apparatus, a facsimile apparatus, and a copying machine.

  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 conveyed image. A reading unit 8 is provided.

  The ADF 1 is an automatic document conveyance device that includes a document setting unit, a plurality of conveyance rollers, a document pressing unit, 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 CCD (Charge Coupled Device), and can read image data from the 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 processes. 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 (working area) for various processes executed by the CPU. In the control unit 5, various control programs stored in advance in the ROM are executed by the CPU. As a result, the image forming apparatus 10 is comprehensively controlled by the control unit 5. The control unit 5 may be an electronic circuit such as an integrated circuit (ASIC), and is a control unit provided separately from the main control unit that controls the image forming apparatus 10 in an integrated manner. May be.

  The operation display unit 6 is a display unit such as a liquid crystal display that displays various types of information in response to control instructions from the control unit 5, and an operation key or a touch panel that inputs various types of information to the control unit 5 in response to user operations. Has an operation unit.

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

  The image forming unit 3 can execute an image forming process (printing process) for forming a color or monochrome image by electrophotography based on the image data read by the image reading unit 2. The image forming unit 3 can also execute the printing process based on image data input from an information processing apparatus 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 corresponds to Y (yellow), the image forming unit 32 corresponds to C (cyan), the image forming unit 33 corresponds to M (magenta), and the image forming unit 34 corresponds to K (black). is there. As shown in FIGS. 1 and 2, the image forming units 31 to 34 are provided in the order of yellow, cyan, magenta, and black along the conveyance direction D <b> 1 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 stores yellow toner. The toner container 30F of the image forming unit 32 stores cyan toner. The toner container 30F of the image forming unit 33 stores magenta toner. The toner container 30F of the image forming unit 34 stores black toner. The image forming units 31 to 34 form toner images of the colors corresponding to the toners 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 in response to application of a voltage. Specifically, as illustrated 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 in response to application of a voltage. Toner 30C is supplied with toner from toner container 30F. The primary transfer roller 30 </ b> D transfers the toner image formed on the surface of the photosensitive drum 30 </ b> A 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 being transferred 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 30 </ b> A 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 the sheet by the secondary transfer roller 37 (see FIG. 1 or 2). Transport to. As shown in FIG. 2, the intermediate transfer device 36 includes an intermediate transfer belt 361, a driving roller 362, a stretching roller 363, and a belt cleaning unit 364. The intermediate transfer belt 361 is an endless belt member to which a toner image formed on the surface of each photosensitive drum 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 with a driving force supplied from a power source (not shown), thereby causing the intermediate transfer belt 361 to travel along the transport direction D1. The belt cleaning unit 364 cleans the surface of the intermediate transfer belt 361 after being transferred by the secondary transfer roller 37.

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

  The fixing unit 38 melts and fixes the toner image transferred to the sheet by the secondary transfer roller 37 on 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 and fixes the toner image transferred to the sheet to the sheet. The pressure roller 382 presses the sheet that passes through the fixing position P <b> 2 (see FIG. 1) that is a contact portion formed with the fixing roller 381.

  The sheet conveying unit 4 conveys a sheet on which an image is printed by the image forming unit 3. Specifically, as shown in FIG. 1, the sheet conveyance unit 4 includes a conveyance path 40, a paper feed cassette 41, a pickup roller 42, a first conveyance roller 43, a registration roller 44, a second conveyance roller 45, and a discharge roller 46. , And a sheet discharge unit 47. The conveyance path 40 is a sheet moving path that connects the sheet feeding cassette 41 and the sheet discharge unit 47. In the sheet conveyance unit 4, the pickup roller 42, the first conveyance roller 43, the registration roller 44, the second conveyance roller 45, and the discharge roller 46 are rotated by a driving force supplied from a driving source (not shown). As a result, the sheet stored in the sheet feeding cassette 41 is transported along the transport direction D <b> 2 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 on the downstream side in the transport direction D <b> 2 from the registration roller 44 in the transport path 40. Further, the fixing unit 38 of the image forming unit 3 is provided on the downstream side in the transport direction D2 from the secondary transfer roller 37 in the transport path 40.

  In the image forming unit 3, a color image is formed on the sheet supplied from the sheet conveying unit 4 according to the following procedure. The sheet on which the 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 scanning device 35 irradiates the surface of the photosensitive drum 30A with light based on the image data. Thereby, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 30A. The electrostatic latent image on the photoreceptor 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, in the image forming units 32 to 34, a toner image is formed on the photosensitive drum 30 </ b> A of each of the image forming units 32 to 34 by the same processing procedure as that of the image forming unit 31 and transferred to the intermediate transfer belt 361. The Accordingly, yellow, cyan, magenta, and black toner images are sequentially superimposed and transferred onto the surface of the intermediate transfer belt 361. The toner image transferred to the surface of the intermediate transfer belt 361 is conveyed to the transfer position P1 by the secondary transfer roller 37 by the intermediate transfer device 36.

  On the other hand, the sheet conveying unit 4 supplies the sheet to the transfer position P1 in synchronization with the conveyance timing of the toner image to the transfer position P1 by the intermediate transfer device 36. Specifically, the pick-up roller 42 is the uppermost of the sheets stored in the paper feed cassette 41 that has been lifted up to the contact position with the pick-up roller 42 by a lift plate (not shown) provided at the bottom of the paper feed cassette 41. The upper sheet is sent to the conveyance path 40. The sheet sent to the conveyance path 40 by the pickup roller 42 is conveyed to the registration roller 44 by the first conveyance roller 43.

  The registration roller 44 sends the sheet to the transfer position P1 in accordance with the conveyance timing. Specifically, the sheet feeding timing by the registration roller 44 is determined by the control unit 5 based on an electrical 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. It is determined. The secondary transfer roller 37 transfers the toner image formed on the intermediate transfer belt 361 to the sheet fed from the registration roller 44 at the transfer position P1.

  The sheet on which the toner image is transferred by the secondary transfer roller 37 is conveyed to the 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. As a result, the toner image is fixed on the sheet. Thereafter, the sheet on which the toner image is 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.

  By the way, in the image forming apparatus 10, the charge amount of the toner changes due to changes in temperature and humidity in the installation environment. As a result, the output characteristics of the image forming apparatus 10 change, and the color reproducibility of the printed matter is lowered. On the other hand, there is a configuration capable of executing a calibration process for printing a plurality of patches corresponding to a plurality of color data and suppressing a decrease in color reproducibility based on a colorimetric result for each printed patch. Known as related technology. Specifically, in the related technique, correction data that can correct a deviation between the colorimetric result and each 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, 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 correction using 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 P <b> 2 in the transport path 40 in the transport direction D <b> 2 and reads an image from the sheet transported by the sheet transport unit 4. 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 CIS (Contact Image Sensor) including a light emitting unit and a light receiving unit. The light emitting unit irradiates light on the image formed on the sheet. The light receiving unit receives the light emitted from the light emitting unit and reflected by the image on the sheet, and outputs an electrical signal corresponding to the amount of light received. The transport image reading unit 8 acquires the image data by converting 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). 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 image sensor 81 is disposed at a position separated from the fixing position P2 in the transport path 40 by a predetermined distance 81A in the transport direction D2. As a result, the image sensor 81 is prevented from being deteriorated by heat generated from the fixing unit 38. The distance 81A may be appropriately set in consideration of the influence on the image sensor 81 due to heat generated from the fixing unit 38. Further, the image sensor 81 is disposed 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, the ROM of the control unit 5 stores in advance a voltage adjustment program for causing the CPU of the control unit 5 to execute a voltage adjustment process (see the flowchart of FIG. 6) described later. The voltage adjustment program may be recorded on a computer-readable recording medium such as a CD, DVD, or flash memory, and may be installed from the recording medium to 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 color measurement unit 52, a second determination processing unit 53, a second adjustment processing unit 54, a first determination processing unit 55, and a first adjustment process. Unit 56, third determination processing unit 57, notification processing unit 58, and third adjustment processing unit 59. Specifically, the CPU of the control unit 5 executes the voltage adjustment program stored in the ROM. Accordingly, 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 processing. Functions as a unit 57, a notification processing unit 58, and a third adjustment processing unit 59.

  The patch printing unit 51 includes a first patch corresponding to predetermined first color data, a second patch corresponding to predetermined second color data, and a third patch corresponding to 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 expressed in a CMYK color space. Hereinafter, the first patch, the second patch, and the third patch may be collectively referred to as a patch.

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

  Here, in the image forming apparatus 10, a preset output profile corresponding to the output characteristics of the own apparatus is stored in the storage unit 7. The output profile represents data representing colors expressed in the CMYK color space, which is a device-dependent color depending on the output characteristics of the image forming apparatus 10, and Lab, which is a non-device-dependent color that does not depend on the output characteristics of the image forming apparatus 10 This data is used for the first color conversion to be converted into data indicating the color expressed in the color space. For example, the output profile is created based on the color measurement result of the color of the printed matter printed by the image forming apparatus 10 under a predetermined environmental condition when the image forming apparatus 10 is manufactured. 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. The first color conversion is an example of color conversion in the present invention. The first color conversion is to convert data representing a color expressed in the CMYK color space into data representing a color expressed in a non-device-dependent color space different from the Lab color space. 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 and the second color data printed based on the first color data The color of the printed matter printed on the basis of is the same color.

  For example, in the image forming apparatus 10, the three first color data having different color components are stored in the storage unit 7. In the image forming apparatus 10, the three second color data corresponding to the three first color data and the one third color data are stored in the storage unit 7. The patch printing unit 51 corresponds to the three first patches corresponding to the three first color data, the three second patches corresponding to the three second color data, and the one 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 converted values after the first color conversion based on the output profile are the same. The first color data A12 and the second color data A22 are determined so that the converted values after the first color conversion based on the output profile are the same. 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 are the same.

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

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

  Here, FIG. 5 shows the first patch B11 to B13, the second patch B21 to B23, and the third patch B31 as an example of the patch printed on the sheet. In FIG. 5, the image forming area X11 in 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 the plurality of first patches and the plurality of second patches. In this case, the density of the K color component included in the first color data may be different among the plurality of first color data. The patch printing unit 51 may print one first patch and one second patch.

  The printing condition may be that an instruction to execute the printing process is input. Further, the printing 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 color measurement unit 52 measures the colors of the first patch, the second patch, and the third patch printed by the patch printing unit 51. Specifically, the color measurement unit 52 acquires data indicating the colors of the first patch, the second patch, and the third patch.

  For example, the colorimetric unit 52 may use the first patch, the second patch, and the second patch based on image data read from a sheet on which the first patch, the second patch, and the third patch are printed by the transport image reading unit 8. The colors of the two patches and the third patch are 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 represents data representing a color expressed in an RGB color space, which is a device-dependent color depending on the input characteristics of the transport image reading unit 8, in a non-device-dependent color that does not depend on the input characteristics of the transport image reading unit 8. This data is used for the second color conversion for converting into data indicating a color expressed in a certain Lab color space.

  For example, the color measurement 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 color measurement unit 52 calculates an average value of RGB values in the extracted plurality of pixel data. Then, the color measurement unit 52 acquires the Lab value acquired by performing the second color conversion on the average value of the calculated RGB values as data indicating the color of the first patch. Similarly, the color measurement unit 52 acquires data indicating the color of the second patch and data indicating the color of the third patch.

  Note that the color measurement unit 52 is configured so that the image reading unit 2 reads the first patch, the second patch, and the second patch based on image data read from a sheet on which the first patch, the second patch, and the third patch are printed. The color of each of the patch and the third patch may be measured.

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

  When the second adjustment 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 by the second determination processing unit 53 In addition, the applied voltage in the developing unit 30C of the image forming unit 34 corresponding to the K color is adjusted, and the difference between the converted value of the third color data and the colorimetric value of the third patch is set to the second allowable value. A second adjustment process for reducing the value to 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 conversion value of the third color data, the setting of the applied voltage in the developing unit 30C of the image forming unit 34 is performed. 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 conversion value of the third color data, the setting of the applied voltage in the developing unit 30C of the image forming unit 34 is performed. The value is decreased 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, the patch printing unit 51 prints the patch again, and the printed patch is converted into the colorimetric unit. The color is measured by 52. Then, the second determination processing unit 53 determines whether or not the difference between the colorimetric value of the third printed patch and the converted value of the third color data is within the second allowable value. When it is determined that the second allowable value is exceeded, 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 an 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 values 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, based on the difference between the density of the K color component in the converted data and the density of the K color component in the third color data, and the area of the third patch, The amount of toner deficiency or excess in the printed third patch is calculated. The second adjustment processing unit 54 is calculated based on table data indicating the relationship between the increase / decrease value of the applied voltage stored in advance in the storage unit 7 and the increase / decrease value of the toner amount supplied by the developing unit 30C. The increase / decrease value of the applied voltage corresponding to the insufficient amount or the excessive amount is acquired.

  If 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 preset first allowable value.

  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 the first allowable value. It is determined whether it is within the value.

  For example, the first determination processing unit 55 determines that the colorimetric values 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 both Lab colors. In the case of data 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 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 both Lab colors. If the data is expressed in space, it is determined whether or not the difference between the two L values is within the first allowable value.

  Further, the first determination processing unit 55 determines that the colorimetric values 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. When the data is expressed in space, it is determined whether or not the difference between the two 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 CMYK. The applied voltage in each developing unit 30C corresponding to each of the colors is adjusted to reduce the difference between the colorimetric values of the first patch and the second patch within the first allowable value.

  Specifically, the first adjustment processing unit 56 uses the first determination processing unit 55 to determine the difference between the colorimetric values of the first patch and the second patch for any one or more of the pair of patches. When it is determined that the first allowable value is exceeded, 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 for adjusting the applied voltage in the unit 30C and reducing a difference between the colorimetric values of the first patch and the second patch within the first allowable value is executed.

  For example, in the first adjustment process, the colorimetric value of the second patch corresponding to the first patch in which the b value of the colorimetric value of the first patch not including the Y color component does not include the Y color component. Is higher than the b value, the set value of the applied voltage in the developing section 30C of the image forming unit 31 is increased by the adjustment value. On the other hand, in the first adjustment process, the colorimetric value of the second patch corresponding to the first patch in which the b value of the colorimetric value of the first patch not including the Y color component does not include the Y color component. Is lower than the b value, the set value of the applied voltage in the developing section 30C of the image forming unit 31 is decreased by the adjustment value.

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

  In the first adjustment process, the colorimetric value of the second patch corresponding to the first patch in which the a value of the colorimetric value of the first patch not including the M color component does not include the M color component. Is higher than the adjustment value, the set value of the applied voltage in the developing section 30C of the image forming unit 33 is increased by the adjustment value. On the other hand, in the first adjustment process, the colorimetric value of the second patch corresponding to the first patch in which the a value of the colorimetric value of the first patch not including the M color component does not include the M color component. Is lower than the a value, the set value of the applied voltage in the developing section 30C of the image forming unit 33 is decreased by the adjustment value.

  Further, in the first adjustment process, after the set value of the applied voltage in each of the developing units 30C is changed, the 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 allowable value exceeds 1, 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 is within the first allowable value for all the pair of patches. It is repeated until

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

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

  The third determination processing unit 57 determines that 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 for each pair of patches. You may determine whether it is less than 3 tolerance values.

  The notification processing unit 58 uses the third determination processing unit 57 to determine whether the difference between the colorimetric value of the first patch and the converted value of the first color data for the one or a plurality of the pair of patches is the third allowable value. When it is determined that the value has been exceeded, a message that prompts to change one or both of the environmental temperature and the environmental humidity is notified. For example, the notification processing unit 58 causes the operation display unit 6 to display the message.

  Note that the notification processing unit 58 determines whether the difference between the colorimetric value of the second patch and the converted value of the second color data for the one or a plurality of the pair of patches is determined by the third determination processing unit 57. When it is determined that 3 allowable values are exceeded, the message may be notified.

  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. A third adjustment process is executed to reduce the difference between the colorimetric value of the first patch and the converted value of the first color data of the pair of patches determined as.

  For example, in the third adjustment process, when the a value of the conversion value of the first color data not including the Y color component is higher than the a value of the color measurement 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 decreased by a preset value. On the other hand, in the third adjustment process, when the a value of the conversion value of the first color data not including the Y color component is lower than the a value of the color measurement 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 conversion value of the first color data not including the Y color component is higher than the color measurement value b of the first patch not including the Y color component, the image 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 not including the Y color component is lower than the b 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 32 is decreased by a preset value.

  In the third adjustment process, when the a value of the conversion value of the first color data not including the C color component is higher than the a value of the color measurement 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 33 is increased by a preset value. On the other hand, in the third adjustment process, when the a value of the conversion value of the first color data not including the C color component is lower than the a value of the color measurement 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 33 is decreased by a preset value.

  In the third adjustment process, when the b value of the conversion value of the first color data not including the C color component is higher than the color measurement value b of the first patch not including the C color component, the image 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 conversion value of the first color data not including the C color component is lower than the b value of the color measurement 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 decreased by a preset value.

  In the third adjustment process, when the a value of the conversion value of the first color data not including the M color component is higher than the a value of the color measurement 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 decreased by a preset value. On the other hand, in the third adjustment process, when the a value of the conversion value of the first color data not including the M color component is lower than the a value of the color measurement 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 increased by a preset value.

  In the third adjustment process, when the b value of the conversion value of the first color data not including the M color component is higher than the color measurement value b of the first patch not including the M color component, the image 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 conversion value of the first color data not including the M color component is lower than the b value of the color measurement 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 decreased 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 converted value of the second color data by the first color conversion and the color measurement unit 52. 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 the procedure of the voltage adjustment process executed 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 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 conditions are satisfied. For example, when the execution instruction for the printing process is input, the control unit 5 determines that the printing condition is satisfied when a predetermined time has elapsed since the previous patch was printed.

  Here, if the control part 5 judges that the said printing conditions were satisfied (Yes side of S11), it will transfer a process to step S12. If the printing condition is not satisfied (No side in S11), the control unit 5 waits for the printing condition to be satisfied 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 processing of step S11 and step S12 is executed by the patch printing unit 51 of the control unit 5.

  For example, the control unit 5 includes 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 by 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 S <b> 13 is executed by the color measurement unit 52 of the control unit 5.

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

<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 acquired in step S13 is within the second allowable value. It is determined whether or not there is. Here, the process of step S <b> 14 is executed by the second determination processing unit 53 of the control unit 5.

  For example, the controller 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 the range.

  Here, when 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 side of S14), the process is performed. 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 moves the process to step S15. Transition.

<Step S15>
In step S15, the control unit 5 executes the second adjustment process. Here, the process of step S <b> 15 is executed by the second adjustment processing unit 54 of the control unit 5.

  The application in the developing unit 30C of the image forming unit 34 so 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 adjustment process. The voltage is adjusted. In addition, the process of step S14 and step S15 may be abbreviate | omitted.

<Step S16>
In step S <b> 16, 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 the pair of patches. Here, the process of step S <b> 16 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 or not 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.

  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 the pair of patches (Yes in S16) ), The process proceeds to step S18. Further, for any one or a plurality 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 side of S16), The control unit 5 shifts the process to step S17.

<Step S17>
In step S17, the control unit 5 executes the first adjustment process. Here, the process of step S <b> 17 is executed by the first adjustment processing unit 56 of the control unit 5.

  The application in each of the developing units 30C of the image forming units 31 to 33 so that the difference between the colorimetric values of the first patch and the second patch is within the first allowable value by the first adjustment process. The voltage is adjusted. Here, in the image forming apparatus 10, as described above, 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 displayed. 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 are the same color, printing caused due to an environmental change or the like The deviation between the output characteristic at the time and the output characteristic 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 process, the second adjustment process is executed before the first adjustment process, and the applied voltage of the developing unit 30C corresponding to the K color component is adjusted first. As a result, the number of developing units 30C adjusted in the first adjustment process is reduced to three. In the first adjustment process, for each of the pair of patches determined to exceed the first allowable value in step S16, the developing unit 30C corresponding to the color component not included in the first patch. The applied voltage is adjusted. Therefore, the number of developing units 30C to be adjusted when the difference between the colorimetric values of the first patch and the second patch is reduced within the first allowable value in one pair of patches is one. Has been reduced. Accordingly, a plurality of developing units 30C are adjusted when the difference between the colorimetric values of the first patch and the second patch is reduced within the first allowable value in one pair of patches. Compared to the configuration, the processing contents of the first adjustment processing can be simplified.

  Note that if the set value of the density of the K color component included in the first color data (the reference density) is too low, the converted values after the first color conversion based on the output profile are the same. It is conceivable that there is no combination of the first color data and the second color data. In addition, when the reference density is too high, it is considered that the effect of suppressing the decrease in color reproducibility according to the present invention is reduced for a low density color compared to a high density color. For example, the reference concentration is desirably set within a range of 20 percent to 80 percent.

<Step S18>
In step S18, the controller 5 determines that the difference between the colorimetric value of the first patch and the converted value of the first color data obtained by the first color conversion is within the third allowable value for all the pair of patches. It is determined whether or not there is. Here, the process of step S <b> 18 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 each of 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 the range. Further, the controller 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 the range. Further, the control unit 5 determines that the difference between each of 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 the range.

  Here, the controller 5 determines that the difference between the colorimetric value of the first patch and the converted value of the first color data obtained by the first color conversion is within the third allowable value for all the pair of patches. (Yes in S18), the process proceeds to step S11. The difference between the colorimetric value of the first patch and the converted value of the first color data by the first color conversion for any one or a plurality of the pair of patches may exceed the third allowable value. If it is (No side of S18), the control part 5 will transfer a process 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 S <b> 19 is executed by the notification processing unit 58.

  When the deviation between the output characteristics at the time of printing caused by environmental changes or the like and the output characteristics corresponding to the output profile is large, the color of the printed matter printed based on the first color data and the first 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 becomes the same color, the output characteristics at the time of printing and the output characteristics corresponding to the output profile It is possible that a gap between On the other hand, in the voltage adjustment process, the difference between the colorimetric value of the first patch and the converted value of the first color data by the first color conversion for any one or a plurality of the pair of patches The message is notified when the third allowable value is exceeded. As a result, the user is prompted to change either or both of the environmental temperature and the environmental humidity due to the operation of the air conditioner, etc., and the output characteristics at the time of printing caused by the environmental change etc. Can be reduced.

<Step S20>
In step S20, the control unit 5 executes the third adjustment process. Here, the process of step S <b> 20 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. In addition, the process of step S18-step S20, or the process of step S20 may be abbreviate | omitted.

  Thus, in the voltage adjustment process, the first patch corresponding to the first color data and the second patch corresponding to the second color data are printed. Then, by adjusting the applied voltage in each of the developing units 30C so that the color of the first patch and the color of the second patch are the same color, printing at the time of printing caused by an environmental change or the like 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 conveying unit 5: Control unit 6: Operation display unit 7: Storage unit 8: Conveyed image reading unit 10: Image forming apparatuses 31 to 34: Image forming unit 30A: Photoconductor Drum 30C: developing unit 38: fixing unit 40: transport path 51: patch printing unit 52: color measuring 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 which is provided corresponding to each color of CMYK and develops an electrostatic latent image formed on the image carrier in response to application of a voltage;
CMYK color space based on a first patch corresponding to predetermined first color data including any two color components of K color components and CMY, and a preset profile corresponding to output characteristics of the device itself A patch printing unit that prints a second patch corresponding to second color data that has the same color value as that of the first color data and includes each color component of CMY;
A colorimetric unit for measuring the colors of the first patch and the second patch printed by the patch printing unit;
A first determination processing unit that determines whether or not a difference between the colorimetric values of the first patch and the second patch by the colorimetric unit is within a preset first allowable value;
The developing unit corresponding to each color of CMYK 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 A first adjustment processing unit that adjusts the applied voltage in each to reduce the difference between the colorimetric values of the first patch and the second patch within the first allowable value;
An image forming apparatus comprising: The patch printing unit prints the plurality of 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 color component of K having a predetermined reference density,
The patch printing unit includes three first patches having different color components, 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 color measurement 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:
Second determination for determining whether or not a difference between the converted value of the third color data by the color conversion and the colorimetric value of the third patch by the colorimetric unit is within a preset second allowable value. 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, it corresponds to the color K. 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 within the second allowable value; Prepared,
The first determination processing unit determines that a difference between the conversion 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. For each pair of patches including the first patch and the second patch corresponding to the first patch, the difference between the colorimetric values of the first patch and the second patch by the colorimetric unit is the first patch. Determine whether it is within the tolerance,
In the first adjustment processing unit, the difference between the colorimetric values of the first patch and the second patch with respect to 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 first patch exceeds the first allowable value, the application in the developing unit corresponding to a color component not included in the first patch is determined for each of the pair of patches determined to exceed the first allowable value. Adjusting the voltage to reduce the difference between the colorimetric values of each of the first patch and the second patch 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 the first patch and the second patch is within the first allowable value for all the pair of patches, the pair of pairs For each patch, a difference between the colorimetric value of the first patch or the second patch by the colorimetric unit and the converted value of the first color data or the second color data by the color conversion is preset. A third determination processing unit for determining whether the value is within an allowable value;
The difference between the colorimetric value of the first patch or the second patch and the 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. A notification processing unit that notifies a message that prompts a change in one or both of the environmental temperature and the environmental humidity when it is determined that the value exceeds the third allowable value;
An image forming apparatus according to claim 3. When the message is notified by the notification processing unit, the pair of patches that are determined to exceed the third allowable value by adjusting the applied voltage in each of the developing units corresponding to each color of CMY 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 through 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 that is provided on the downstream side in the sheet conveyance direction from the fixing position by the fixing unit in the conveyance path and reads a patch printed by the patch printing unit,
The color measuring 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 by the printing process when a printing process based on image data is executed.
The image forming apparatus according to claim 1. A voltage adjustment method executed in an image forming apparatus that is provided corresponding to each color of CMYK and includes a developing unit that develops an electrostatic latent image formed on an image carrier in response to voltage application,
CMYK color space based on a first patch corresponding to predetermined first color data including any two color components of K color components and CMY, and a preset profile corresponding to output characteristics of the device itself Printing a second patch corresponding to second color data having a conversion value obtained by color conversion from a predetermined color space to a predetermined color space that is the same as the first color data and includes CMY color components;
Measuring the color of each of the printed first patch and the second patch;
Determining whether a difference between the colorimetric values of each 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 applied voltage in 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 within the first allowable value;
A voltage adjustment method including:

Images