JP2018077516A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can maintain the gradation and quality of an image.SOLUTION: An image forming apparatus comprises: conversion means that converts image data on the basis of a conversion condition; image forming means that forms images on the basis of the image data converted by the conversion means; image carriers that carry images for measurement formed by the image forming means; measuring means that measures the images for measurement on the image carriers; creation means that causes the image forming means to form the plurality of images for measurement while the image forming means continuously forms the plurality of images, and creates the conversion condition on the basis of the measurement value for the plurality of images for measurement measured by the measuring means; and determination means that determines an image forming condition for the image forming means to form a plurality of images for measurement next time on the basis of the measurement value for a predetermined image for measurement included in the plurality of images for measurement measured by the measuring means. The conversion condition used by the conversion means to convert the image data until the image forming means forms a plurality of images for measurement next time is set on the basis of the conversion condition created by the creation means.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a density control technique in an image forming apparatus.

  In an image forming apparatus using an electrophotographic method, density stability and gradation stability of an output image are required. Therefore, in Patent Documents 1 and 2, a test pattern is formed on an image carrier, and the density of the formed test pattern is read by a sensor or the like, thereby adjusting image forming conditions and generating a gradation correction table to stabilize the image quality. The structure to be made is disclosed.

Japanese Patent Laid-Open No. 04-267272 JP 06-198973 A

  The density of the image formed by the image forming apparatus depends on the charge amount of the developer itself in addition to the image forming conditions such as the development contrast potential. For example, when the consumption amount of the developer increases depending on the use situation of the user, the developer in the developing unit is used for image formation without being sufficiently charged by friction. In this case, the density of the formed image is high. On the contrary, when the consumption amount of the developer is reduced depending on the use state of the user, the charge amount of the developer in the developing unit is increased more than expected due to frictional charging. In this case, the density of the formed image is low. Here, for example, if the charge amount of the developer in the developing unit continues to increase, the output image data value with respect to the input image data value of the gradation correction table is continuously increased by density control to compensate for the decrease in density. However, the output image data value has a maximum value. Therefore, when the charge amount of the developer in the developing unit continues to increase, the gradation correction table generated in the density control converts all input image data values that are equal to or greater than a predetermined value to the maximum value of the same output image data value. There is a possibility of becoming a thing. In this case, the gradation cannot be maintained. Further, when the charge amount of the developer in the developing unit continues to decrease, the output image data value with respect to the input image data value of the gradation correction table is continuously lowered by the density control. In this case, jaggy may occur in the line portion of the formed image.

  In view of the above problems, the present invention provides an image forming apparatus capable of maintaining the gradation and quality of an image.

  According to one aspect of the present invention, an image forming apparatus includes: a conversion unit that converts image data based on a conversion condition; an image formation unit that forms an image based on the image data converted by the conversion unit; An image carrier that carries the measurement image formed by the image forming unit, a measurement unit that measures the measurement image on the image carrier, and the image forming unit continuously forms a plurality of images. A generating unit that forms a plurality of measurement images on the image forming unit and generates conversion conditions based on measurement values of the plurality of measurement images by the measuring unit, and the image forming unit includes the plurality of image forming units. Determining means for determining image forming conditions for forming the next measurement image based on measurement values of predetermined measurement images included in the plurality of measurement images measured by the measurement means. Shi The conversion condition used by the conversion unit to convert the image data until the image forming unit forms the plurality of measurement images next time is set based on the conversion condition generated by the generation unit. It is characterized by that.

  According to the present invention, the gradation and quality of an image can be maintained.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. The figure which shows the test pattern by one Embodiment. The flowchart of the gradation correction control by one Embodiment. The figure which shows the test pattern formed by the gradation correction control by one Embodiment. The figure which shows the relationship between the input image data value and target density by one Embodiment. 10 is a flowchart of correction control of a gradation correction table according to an embodiment. The figure which shows the image formed by one Embodiment. The figure which shows an example of the gradation correction table obtained by correct | amending only by the detection result of the formed image. Explanatory drawing of the replacement process by one Embodiment. The graph which shows the reverse conversion table by one Embodiment. The graph which shows the gradation correction table after correction | amendment by one Embodiment. 6 is a flowchart of gradation correction table correction control according to an embodiment.

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. The following embodiments are for the purpose of explanation, and do not limit the scope of the present invention to the embodiments. In the following drawings, components that are not necessary for the description of the embodiments are omitted from the drawings.

<First embodiment>
FIG. 1 is a configuration diagram of an image forming apparatus 100 according to the present embodiment. In the image forming apparatus 100 of FIG. 1, yellow, magenta, cyan, and black image forming portions PY, PM, PC, and PK are arranged along the intermediate transfer belt 6. The photoconductor 1Y of the image forming unit PY is an image carrier and is driven to rotate in the direction of the arrow in the figure and is charged to a predetermined potential by the charging unit 2Y. The exposure unit 3Y scans and exposes the photoconductor 1Y with light to form an electrostatic latent image on the surface of the photoconductor 1Y. The developing unit 4Y outputs a developing bias, supplies yellow toner (developer) to the electrostatic latent image on the photoreceptor 1Y, and visualizes it as a toner image. The primary transfer roller 7Y outputs a primary transfer bias to transfer the toner image formed on the photoreceptor 1Y to the intermediate transfer belt 6. Further, the image forming unit PY includes a density sensor 12Y for detecting the density of the toner image formed on the photoreceptor 1Y. For example, the density sensor 12Y irradiates the photoreceptor 1Y with light, and detects the density by the reflected light.

  Since the image forming units PM, PC, and PK and the image forming unit PY have the same configuration except for the color of the toner to be used, description of the image forming units PM, PC, and PK is omitted. In the following description, when it is not necessary to distinguish colors, reference numerals excluding characters Y, M, C, and K are used. Note that a multicolor toner image is formed on the intermediate transfer belt 6 by superimposing and transferring the toner images formed on the photoreceptor 1 of each image forming unit to the intermediate transfer belt 6.

  The intermediate transfer belt 6 is stretched by three rollers 61, 62 and 63 and is driven to rotate in the direction of an arrow R2 in the drawing. The recording material P taken out from the cassette 65 is conveyed by a roller pair 66 and 67 toward a secondary transfer portion T2 constituted by a roller 63 and a secondary transfer roller 64. The toner image transferred to the intermediate transfer belt 6 is transferred to the recording material P at the secondary transfer portion T2. Thereafter, the recording material P is heated and pressurized in the fixing unit 11, the toner image is fixed on the recording material P, and is discharged outside the apparatus.

  The light source 103 of the reading unit 216 irradiates the recording material placed on the document table 102 with light, and the CCD sensor 105 receives the reflected light and reads the image of the recording material. The image data read by the CCD sensor 105 is subjected to predetermined image processing by the reader image processing unit 108 and the printer control unit 109. The image forming apparatus 100 according to the present embodiment prints image data received via a telephone line (FAX) or image data received from a computer via a network in addition to the image read by the reading unit 216. It is configured so that it can be performed. The operation unit 20 includes a display unit 218 for the user to operate the image forming apparatus 100 and display the state of the image forming apparatus 100 to the user. The control unit 110 comprehensively controls the image forming operation of the image forming apparatus 100 and includes a CPU 111, a RAM 112, and a ROM 113. The control unit 110 determines and acquires density information of the toner image formed on the photoconductor 1 based on a signal from the density sensor 12. The CPU 111 uses the program and various data stored in the ROM 113 and controls the image forming apparatus 100 using the RAM 112 as a work area. Furthermore, the image forming apparatus 100 includes an environmental sensor 30 that acquires environmental information in the image forming apparatus, for example, one or both of temperature and humidity, and notifies the control unit 110 of the environmental information.

  Next, density control according to the present embodiment will be described. The density control of the present embodiment includes tone correction control for generating a tone correction table (γLUT) and tone correction table correction control for correcting the tone correction table generated by the tone correction control. Yes. The density control is performed for each color. In the present embodiment, the gradation correction control is executed by a user operation or satisfying a predetermined condition. In the gradation correction control, a toner image is formed and fixed on a recording material, and the fixed toner image is read by the reading unit 216 to determine image forming conditions related to density. In this tone correction control, image forming conditions for forming an image with a target maximum density (hereinafter referred to as a maximum density condition value) and image data input to realize the target density A gradation correction table for converting the value of is generated. Further, using the generated gradation correction table, a test pattern R shown in FIG. 2A is formed on the photosensitive member 1 with the determined maximum density condition value. In the present embodiment, the test pattern R is an image pattern including 10 types of density (gradation) including a solid image (maximum density image), as shown in FIG. However, other numbers of gradations may be used. The image forming apparatus 100 measures the density of the test pattern R with the density sensor 12, and the correspondence between the value of the image data used to form the test pattern R and the density formed on the photoconductor 1 with the value. Is obtained.

  Thereafter, every time a predetermined number of sheets are passed during continuous image formation, the image forming apparatus 100 performs correction control of the gradation correction table (hereinafter simply referred to as correction control). In the correction control, the test pattern Q shown in FIG. 2B is formed on the photoconductor 1, and the density of the test pattern Q is detected by the density sensor 12 to correct the gradation correction table. In the correction control, the test pattern Q is formed in a region during the formation of the toner image to be printed on the surface of the photoreceptor 1 as shown in FIG. The input values used to form the test pattern Q are stored in the ROM 113 or RAM 112. In this embodiment, the input values used to form the test pattern Q are five different values including the maximum image data value. That is, the test pattern Q is a pattern including images of five different densities (tones) including a solid (maximum density) image. However, other numbers of gradations may be used.

  First, details of the gradation correction control will be described with reference to FIG. In S10, the control unit 110 forms a test pattern with image data having a value indicating the maximum density on the recording material. FIG. 4A is an example of a test pattern formed in S10. The test pattern shown in FIG. 4A is formed, for example, when the input image data value is represented by 8 bits, with 255 indicating the maximum density as the input value, and changing the image forming conditions relating to the density. is there. In the following description, the image forming condition that is changed to control the density is the exposure amount, but other image forming conditions relating to the density, for example, other values that change the development contrast such as the developing bias and the charging bias are changed. It is also possible to use a form. Furthermore, the form which changes the several image formation conditions regarding a density | concentration may be sufficient. The user sets the recording material on which the test pattern is formed on the reading unit 216, and in S11, the control unit 110 causes the reading unit 216 to read the test pattern and detects its density. In S12, the control unit 110 determines the maximum density condition value based on the detected density, that is, the value of the image forming condition for setting the toner image formed with the maximum value of the input value as the target maximum density. As described above, in this example, the image forming condition is the exposure amount.

  Subsequently, in S13, the control unit 110 forms a test pattern for gradation correction on the recording material. FIG. 4B is an example of a test pattern formed in S13. For example, when the input image data value is 8 bits, the test pattern shown in FIG. 4B is formed by a plurality of values selected from 0 to 255. The user sets the recording material on which the test pattern is formed on the reading unit 216, and in S14, the control unit 110 causes the reading unit 216 to read the test pattern and detects the density thereof. The control unit 110 generates a gradation correction table in S15 based on the detected density. Thereafter, the control unit 110 forms a test pattern R shown in FIG. 2A on the photoconductor 1 in S16, and the density sensor 12 detects the density in S17. The control unit 110 generates target density information that is a correspondence relationship between the input value used for image formation in S16 and the density of each image of the test pattern R formed with the input value detected in S17, and then in S18. To the RAM 112. FIG. 5 shows the relationship between the value of the input image data obtained by interpolating the target density information stored in S18 and the density of the image formed on the photoconductor 1. Hereinafter, the detected density of each image of the test pattern R detected in S17 is referred to as a target density corresponding to the input value used for forming each image. Further, the detected density of the solid image of the test pattern R is called a target maximum density.

  Subsequently, the correction control of the gradation correction table according to the present embodiment will be described with reference to FIG. As described above, the correction control is executed every time a predetermined number of sheets are passed during continuous image formation. When the correction control is started, the control unit 110 changes the image forming condition relating to the density, that is, the exposure amount in the present embodiment, in S20 when the process of S27 in FIG. 6 is performed in the previous correction control. If the process of S27 in FIG. 6 has not been performed in the previous correction control, the image forming conditions relating to the density are not changed. Details of the processing in S27 and the change in exposure amount in S20 will be described later. Subsequently, the control unit 110 detects the density of each image of the test pattern Q formed by the density sensor 12 in S22 after forming the test pattern Q shown in FIG. The test pattern Q is formed using a gradation correction table stored in the RAM 112.

  Subsequently, in S23, the control unit 110 determines whether or not the target maximum density is higher than the detected maximum density of the test pattern Q, that is, the detected density of the solid image of the test pattern Q. Here, when the detected maximum density is higher than the target maximum density, the output image data value for the maximum value of the input image data value in the gradation correction table is changed to a smaller value in order to obtain an image of the target maximum density. Will be. However, if the output image data value with respect to the maximum input image data value of the gradation correction table is lowered too much, jaggies may occur as shown in FIG. 7A, and the quality of characters and line portions may deteriorate. There is. Therefore, in this case, the control unit 110 determines whether or not the maximum value (output maximum value) of the output image data of the gradation correction table (γLUT) can be further lowered in S24. Specifically, in the present embodiment, it is determined whether the maximum output value of the gradation correction table to be corrected is already equal to or less than the first threshold value. It is determined that it cannot be performed, and the process of S27 is executed. On the other hand, if it is not less than the first threshold, the process of S28 is executed. For example, when the gradation correction table is for converting an 8-bit input image data value into a 10-bit output image data value, as an example, 800 can be used as the first threshold value.

  Further, when S23 is “No”, the control unit 110 determines whether or not the maximum detected density of the test pattern Q is lower than the target maximum density in S25. Here, when the detected maximum density is lower than the target maximum density, the output image data value for the maximum value of the input image data value in the gradation correction table is changed to a larger value in order to obtain an image of the target maximum density. Will be. However, if the output image data value with respect to the maximum value of the input image data value in the gradation correction table is increased too much, the gradation correction table has characteristics as shown by the solid line in FIG. 8, and the gradation cannot be maintained near the maximum density. there is a possibility. Note that a dotted line in FIG. 8 indicates a gradation correction table that can maintain gradation. Therefore, in this case, the control unit 110 determines whether or not the maximum value (output maximum value) of the output image data in the gradation correction table (γLUT) can be further increased in S26. Specifically, in this embodiment, it is determined whether the maximum output value of the correction target gradation correction table is already equal to or greater than the second threshold value, and if it is equal to or greater than the second threshold value, the output value can be further increased. The process of S27 is executed by determining that it cannot be performed. On the other hand, if it is not greater than or equal to the second threshold, the process of S28 is executed. For example, when the gradation correction table converts an 8-bit input image data value into a 10-bit output image data value, 1023 can be used as the second threshold value as an example.

  Subsequently, the process in S27 will be described with reference to FIG. 9A and 9B, reference numeral 81 is a detection result of the density of the solid image of the test pattern Q, and reference numeral 83 is referred to as four other images (hereinafter referred to as an intermediate density image). ) Concentration detection results. Also, the dotted lines in FIGS. 9A and 9B indicate the relationship between the input image data value indicated by the target density information and the density. For example, when the output maximum value of the current gradation correction table is already equal to or smaller than the first threshold value in S24 of FIG. 6, the detected density 81 of the solid image of the test pattern Q shown in FIG. The target maximum density indicated by reference numeral 82 is changed. However, a predetermined density smaller than the detected density and higher than the target maximum density may be used. Similarly, when the output maximum value of the current gradation correction table is already equal to or greater than the second threshold value in S26, in S27, the detection density 81 of the solid image of the test pattern Q shown in FIG. The target maximum density indicated by 82 is changed. However, it may be a predetermined density that is larger than the detected density and lower than the target maximum density.

  Subsequently, the process in S28 of FIG. 6 will be described. When S27 is not executed, the control unit 110 sets the measured value of the test pattern Q as a processing value. When S27 is executed, the control unit 110 processes a value obtained by replacing the measured value with a predetermined density for the density of the solid image. The processing values are plotted as shown in FIG. 9 and linear interpolation is performed between the values. Then, each processing value is inversely transformed with respect to the target density information indicated by the dotted lines in FIGS. 9A and 9B to generate an inverse conversion table. FIG. 10 is a graph showing the input image data values and the output image data values indicated by the inverse conversion table. The dotted line in FIG. 10 shows an inverse conversion table when each processing value is the same as the target density information, that is, on the dotted line in FIG. 9, and the input image data value and the output image data value are the same value. On the other hand, the solid line in FIG. 10 shows an example of an inverse conversion table when the processing value is higher than the target density as shown in FIG. In the solid line in FIG. 10, the output image data value is converted to a value smaller than the input image data value in order to bring the obtained density close to the target density.

  In S28, the control unit 110 updates the gradation correction table (γLUT) held in the RAM 112 using the inverse conversion table. The dotted line in FIG. 11 is a graph representing the gradation correction table before correction, and the solid line is a graph representing the gradation correction table after correction when the inverse conversion table is the solid line in FIG. It is. For example, the corrected gradation correction table is obtained by multiplying the output image data value corresponding to the same input image data value in the gradation correction table before correction and the inverse conversion table and dividing by the input image data value. Desired. The control unit 110 stores the corrected gradation correction table in the RAM 112 and ends the correction control. At this time, whether or not the process of S27 is executed for the next correction control is also stored in the RAM 112. When the control unit 110 finishes the correction control, the control unit 110 forms an image using the gradation correction table stored in the RAM 112.

  When the processing of S27 is executed, the tone correction table is corrected by assuming that a predetermined density is a detection result for the solid image of the test pattern Q instead of the actual detection result. Therefore, the density of the image formed using the gradation correction table corrected in this way is deviated from the target density in the vicinity of the maximum density. Therefore, in the present embodiment, when the process of S27 is executed, the image forming conditions relating to the density that is the exposure amount are changed in the present embodiment. Specifically, as shown in FIG. 9A, when it is determined that the density of the formed image is higher than the target maximum density but the maximum output value of the gradation correction table cannot be lowered, the exposure amount And the density of the image actually formed with the same input image data value is lowered. Similarly, as shown in FIG. 9B, when it is determined that the density of the formed image is lower than the target maximum density but the maximum output value of the gradation correction table cannot be increased, the exposure amount is increased. The density of the image actually formed with the same input image data value is increased. However, in a certain correction control, if the exposure amount is changed after the execution of S27, the subsequent image formation is performed under image formation conditions different from those when the test pattern Q is formed in S21. The density will deviate from the target density. Therefore, in the present embodiment, the control unit 110 stores that the process of S27 has been executed, and changes the exposure amount in S20 when the correction control is executed next, that is, before the test pattern Q is formed. To do. The change amount is increased or decreased in units of a predetermined amount.

  In order to confirm the effect of the present embodiment, when 10,000 sheets are continuously printed and the gradation correction table is corrected using only the actual detection result of the test pattern Q, as shown in FIG. Comparison was made with the case where the gradation correction table was corrected. When the gradation correction table was corrected using only the actual detection result of the test pattern Q, jaggy occurred as shown in FIG. On the other hand, when the gradation correction table was corrected according to FIG. 6, no jaggy occurred as shown in FIG. 7B.

  As described above, an allowable range is provided for the output image data value with respect to the maximum input image data value of the gradation correction table, and the control unit 110 determines whether the output image data value of the corrected gradation correction table is outside this allowable range. Determine whether or not. If it is determined that the density is outside the allowable range, the control unit 110 changes the detected density of the image having the maximum density of the test pattern Q to a predetermined density. In addition, when the detected density of the image having the maximum density of the test pattern Q is changed to a predetermined density, the density-related image forming condition is changed when executing the correction control of the next gradation correction table. With this configuration, deviation of the formed image density from the target density can be reduced.

<Second embodiment>
In the first embodiment, only the detection result of the solid image of the test pattern Q is changed in the correction control. If the detection result of the solid image is changed, the exposure amount is changed at the start of the next correction control. However, if the reduction of the formed image density continues and the reduction amount of the image density is larger than the change amount of the exposure amount, the output is performed when the input image data value is not less than the predetermined value as shown by the solid line in FIG. There is a possibility that the gradation correction table having the same image data value is corrected. In this case, the gradation cannot be maintained. In the present embodiment, the detection result is changed not only for the solid image of the test pattern Q but also for the intermediate density image. It should be noted that the images whose detection results are changed can be all images of the test pattern Q or images with a predetermined density or higher. In the present embodiment, all five images of the test pattern Q are to be changed.

  FIG. 12 is a flowchart of the correction control of the gradation correction table according to the present embodiment. 12 is obtained by replacing S23 to S27 in FIG. 6, and S20 to S22 and S28 are the same as those in FIG. In FIG. 12, i is an index for distinguishing five images of the test pattern Q. Ri is the detected density in S22 of the image i, and Ti is the target density corresponding to the input value of the image data used to form the image i. Further, Oi is the output image data value of the gradation correction table for the input image data value used to form the image i. Further, Th1i and Th2i are the lower limit and upper limit of the allowable range of the output image data value of the gradation correction table with respect to the input image data value used to form the image i. Th1i and Th2i for the intermediate density image are, for example, 0.8 times the output image data value relative to the input image data value used for forming the image i in the gradation correction table generated by the gradation correction control, and 1. It can be determined such as 2 times. Note that Th1i and Th2i for the solid image are the same as in the first embodiment. The control unit 110 executes each process in FIG. 12 for each image i. With this configuration, it is possible to prevent the halftone portion of the gradation correction table from being continuously corrected and to maintain the gradation.

<Third embodiment>
In the first embodiment and the second embodiment, the exposure value to be changed in S20 of FIG. 6 is a predetermined value. However, if the characteristic change of the image forming apparatus is large and cannot be compensated for by the exposure amount changed in S20, the density shift may become too large. In the present embodiment, the exposure amount changed in S20 of FIG. 6 is variable. Hereinafter, how to determine the exposure amount to be changed will be described. In addition, the other process of this embodiment is the same as that of 1st embodiment and 2nd embodiment.

First, the control unit 110 obtains the rate of change of the detected density 81 of the solid image of the test pattern Q shown in FIGS. 9A and 9B with reference to the target maximum density 82 using the following equation.
Rate of change = (detected density / target maximum density−1) × 100
The exposure amount to be changed is increased as the absolute value of the change rate increases. For example, if the absolute value of the change rate is within 10%, the reference amount is the same as that of the first embodiment, and if the absolute value of the change rate is greater than 10% and not more than 20%, the reference amount is doubled. If the absolute value is larger than 30%, it can be set to three times the reference amount. The control unit 110 obtains the exposure amount to be changed in S27 of FIG. 6 or S37 of FIG. 12 and stores it in the RAM 112. When executing the correction control of the next gradation correction table, the control unit 110 executes the RAM 112 in S20 of FIG. The amount of exposure is increased or decreased based on the value held in.

  As described above, the gradation of the image to be formed can be maintained by determining the change amount of the exposure amount according to the change in the characteristics of the image forming apparatus, and the density can be brought close to the target density.

[Other Embodiments]
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

  110: control unit, 1: photoconductor, 12: density sensor

Claims (11)

Conversion means for converting image data based on conversion conditions;
Image forming means for forming an image based on the image data converted by the converting means;
An image carrier that carries a measurement image formed by the image forming means;
Measuring means for measuring the measurement image on the image carrier;
While the image forming unit continuously forms a plurality of images, the image forming unit forms a plurality of measurement images, and the conversion is performed based on the measurement values of the plurality of measurement images by the measurement unit. Generating means for generating a condition;
Image forming conditions for the image forming unit to form the plurality of measurement images next time are determined based on measurement values of predetermined measurement images included in the plurality of measurement images measured by the measurement unit. Determining means to
The conversion condition used by the conversion unit to convert the image data until the image forming unit forms the plurality of measurement images next time is set based on the conversion condition generated by the generation unit. An image forming apparatus. The plurality of measurement images include the predetermined measurement image and another measurement image different from the predetermined measurement image,
The generation means includes a first generation process for generating the conversion condition based on a measurement value of the predetermined measurement image and a measurement value of the other measurement image, and the measurement value of the predetermined measurement image. And a second generation process for generating the conversion condition based on the predetermined measurement value and the measurement value of the other image for measurement using a predetermined measurement value instead of The image forming apparatus according to claim 1. The plurality of measurement images include the predetermined measurement image and another measurement image different from the predetermined measurement image,
The generation unit generates the conversion condition based on a measurement value of the predetermined measurement image and a measurement value of the other measurement image, or a predetermined value instead of the measurement value of the predetermined measurement image. Determining whether to use the measurement value to generate the conversion condition based on the predetermined measurement value and the measurement value of the other measurement image based on the measurement value of the predetermined measurement image; The image forming apparatus according to claim 1, wherein: The plurality of measurement images include the predetermined measurement image and another measurement image different from the predetermined measurement image,
The generation means determines whether to generate the conversion condition using the measurement value of the predetermined measurement image and the measurement value of the other measurement image,
When the generation unit does not generate the conversion condition using the measurement value of the predetermined measurement image and the measurement value of the other measurement image, the generation unit generates a predetermined value instead of the measurement value of the predetermined measurement image. The image forming apparatus according to claim 1, wherein the conversion condition is generated based on the predetermined measurement value and the measurement value of the other measurement image using the measurement value. The conversion condition is a one-dimensional table for converting an input value of image data into an output value,
The generation unit causes the conversion unit to convert measurement image data based on the conversion condition, and causes the image forming unit to form the plurality of measurement images based on the converted measurement image data.
The generation unit is configured to generate the predetermined measurement image based on the measurement value of the predetermined measurement image and the conversion result of the predetermined input value in the one-dimensional table used to form the plurality of measurement images. 5. The image forming apparatus according to claim 4, wherein whether or not to generate the conversion condition is determined using an image measurement value and the measurement value of the other measurement image.   When the measurement value of the predetermined measurement image is darker than a predetermined density and the conversion result of the predetermined input value is smaller than a threshold value, the generation unit generates the predetermined measurement value and the other measurement image. The image forming apparatus according to claim 5, wherein the conversion condition is generated based on a measurement value.   The generation unit is configured to output the predetermined measurement value and the other measurement image when the measurement value of the predetermined measurement image is thinner than the predetermined density and the conversion result of the predetermined input value is larger than a threshold value. The image forming apparatus according to claim 5, wherein the conversion condition is generated based on the measurement value.   The image forming apparatus according to claim 6, wherein the conversion result of the predetermined input value is a conversion result corresponding to a maximum input value in the one-dimensional table.   The image forming apparatus according to claim 2, wherein the predetermined measurement image is darker than a density of the other measurement image.   The image forming apparatus according to claim 1, wherein the image forming condition is a condition for adjusting a maximum density of an image formed by the image forming unit. The image forming unit includes a photoconductor, an exposure unit that exposes the photoconductor to form an electrostatic latent image, and a developing unit that develops the electrostatic latent image on the photoconductor,
The image forming apparatus according to claim 1, wherein the image forming condition includes an exposure intensity of the exposure unit.