JP2018066901A - Image forming apparatus and image forming program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can more reliably correct density unevenness in a main scanning direction compared with a case where the image forming apparatus corrects density unevenness in the main scanning direction only with correction of the amount of exposure, and an image forming program.SOLUTION: An image forming apparatus forms a test image and detects the density of the test image (100, 102), calculates information on correction of a developing bias on the basis of the detected density and sets the calculated correction information to a correction control part (104), subsequently forms a test image again by using the correction information (106), and detects the density of the test image (108). When the density unevenness is not within a predetermined allowable range, the image forming apparatus corrects the amount of exposure conducted by an exposure device to correct a density unevenness in a main scanning direction (110, 112).SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus and an image forming program.

  Patent Document 1 proposes an image forming apparatus that corrects density unevenness by forming a test image, detecting density unevenness, and correcting the development bias and charging bias.

JP 2013-125132 A

  In the electrophotographic image forming apparatus, the density unevenness in the main scanning direction cannot be corrected by the correction by the developing bias or the charging bias, and the density unevenness in the main scanning direction can be corrected by correcting the exposure amount. However, there is a possibility that it cannot be corrected. Therefore, the present invention provides an image forming apparatus and an image forming program capable of more reliably correcting density unevenness in the main scanning direction than when correcting density unevenness in the main scanning direction only by correcting the exposure amount. The purpose is to provide.

  The image forming apparatus according to claim 1, a charging device that charges the image carrier with a charging bias, an exposure device that exposes the charged image carrier to form a latent image, and the latent image with a developing bias. A developing device for developing a toner image on the surface of the image carrier, a transfer device for transferring the toner image to a transfer medium by a transfer bias, and a toner image on the image carrier or the transfer medium A detection unit that detects density unevenness of the transferred toner image and a detection result of the detection unit are used to correct at least one of the charging bias, the development bias, and the transfer bias to determine a plurality of predetermined values. And a correction unit that corrects the exposure amount by the exposure apparatus after reducing variation in density unevenness in the sub-scanning direction at the position in the main scanning direction.

  According to a second aspect of the present invention, in the first aspect of the present invention, the correction unit uses at least one of the charging bias, the development bias, and the transfer bias using a detection result of the detection unit. The exposure amount is corrected after correcting the maximum value of density unevenness in the sub-scanning direction at the plurality of positions in the main scanning direction within a predetermined allowable range.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the correction unit corrects the developing bias by using a detection result of the detection unit to correct the density in the sub-scanning direction. After the unevenness variation is reduced, the exposure amount is corrected.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the correction unit corrects the developing bias using the detection result of the detection unit, and performs the sub-scanning. Even if the variation in density unevenness in the direction is reduced, if the variation in density unevenness in the sub-scanning direction does not fall within the exposure amount correction range, after correcting at least one of the charging bias and the transfer bias, The exposure amount is corrected.

  An image forming program according to a fifth aspect causes a computer to function as a detection unit and a correction unit of the image forming apparatus according to any one of the first to fourth aspects.

  According to the image forming apparatus of claim 1, an image that can more reliably correct the density unevenness in the main scanning direction than the case of correcting the density unevenness in the main scanning direction only by correcting the exposure amount. A forming apparatus can be provided.

  According to the second aspect of the present invention, the correction range for correcting the exposure amount can be narrowed compared to the case of correcting the density unevenness in the main scanning direction only by correcting the exposure amount.

  According to the third aspect of the present invention, density unevenness occurring during development can be more reliably suppressed as compared with the case where the exposure amount of the exposure apparatus is corrected after correcting the charging bias or the transfer bias.

  According to the fourth aspect of the present invention, it is possible to more reliably correct the density unevenness in the main scanning direction than when correcting the exposure amount of the exposure apparatus after correcting the developing bias.

  According to the image processing program of claim 5, an image that can more reliably correct the density unevenness in the main scanning direction than the case of correcting the density unevenness in the main scanning direction only by correcting the exposure amount. A formation program can be provided.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an exemplary embodiment. 2 is a block diagram illustrating a schematic configuration for correcting density unevenness in the image forming apparatus according to the first embodiment. FIG. FIG. 10 is a diagram for explaining an example of correcting the developing bias so that the maximum value of density unevenness in the sub-scanning direction at a plurality of main scanning direction positions is minimized. 6 is a flowchart illustrating an example of a flow of processing performed when correcting density unevenness in the image forming apparatus according to the first embodiment. FIG. 10 is a block diagram illustrating a schematic configuration for correcting density unevenness in an image forming apparatus according to a second embodiment. 10 is a flowchart illustrating an example of a flow of processing performed when correcting density unevenness in the image forming apparatus according to the second embodiment.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus 10 according to the present embodiment. In this embodiment, an image forming apparatus that forms a color image by an electrophotographic method will be described as an example.

  As shown in FIG. 1, in the image forming apparatus 10, an endless belt-like intermediate transfer belt 12 is supported by a plurality of rolls 14 with a predetermined tension.

  On the intermediate transfer belt 12, along the belt conveyance direction X, an image of a color corresponding to each of yellow (Y), magenta (M), cyan (C), and black (K) colors. The image forming units 16Y, 16M, 16C, and 16K are provided in order. In the following description, reference numerals corresponding to the respective colors are omitted unless otherwise specified.

  Each image forming unit 16 is provided with a photosensitive drum 18 as an example of an image holding member corresponding to each color. Each of the photosensitive drums 18 is rotatably supported on an apparatus main body (not shown). Further, around each photosensitive drum 18, along the rotation direction (counterclockwise direction in FIG. 1) of each photosensitive drum 18, a cleaning unit 20, a static eliminator (not shown), a charging device 22, and an exposure device. 24, a developing device 26, and a primary transfer roll 28 as an example of a transfer device are sequentially arranged.

  That is, after the toner remaining on the photosensitive drum 18 is removed by the cleaning unit 20, the charge on the photosensitive drum 18 is neutralized by the static eliminator, the charging bias voltage is applied by the charging device 22, and the photosensitive drum 18 is Charged. Then, the exposure device 24 irradiates and exposes light modulated according to the image to be formed on the surface of the photosensitive drum 18 to form a latent image. The latent image formed by the exposure device 24 is developed by the development device 26 by applying a development bias voltage, and a toner image is formed on the photosensitive drum 18. The toner image formed on the photosensitive drum 18 is transferred onto the intermediate transfer belt 12 by the primary transfer roll 28 by applying a transfer bias voltage. At this time, a color image is formed on the intermediate transfer belt 12 by being transferred onto the intermediate transfer belt 12 so that the toner images formed by the image forming units 16 overlap each other. Note that sub-scanning is performed by the photosensitive drum 18, and main scanning is performed by the exposure device 24.

  Further, the image forming apparatus 10 detects the density of toner images of Y, M, C, and K colors formed on the intermediate transfer belt 12 and measures the density distribution (density unevenness) of the image. The density sensor 30 is disposed downstream of the black image forming unit 16K in the belt conveyance direction (X direction in FIG. 1). As the density sensor 30, for example, a reflection type photosensor arranged in a large number in the main scanning direction can be applied.

  On the other hand, a sheet as an image formation target is accommodated in a sheet feeding unit (not shown), fed out one by one, conveyed along a predetermined path, and sent to the press contact position of the secondary transfer roll 32. Then, after the color image on the intermediate transfer belt 12 is collectively transferred to a sheet as a medium to be transferred by the secondary transfer roll 32, a fixing process (heating, pressing, etc.) is performed by the fixing device 34, and the color image is formed. The formed paper is conveyed from the image forming apparatus 10 and discharged.

  Next, a configuration for correcting density unevenness of the image forming apparatus 10 according to the present embodiment will be described.

(First embodiment)
FIG. 2 is a block diagram illustrating a schematic configuration for correcting density unevenness in the image forming apparatus 10 according to the first embodiment.

  The image forming apparatus 10 according to the present embodiment includes a density unevenness correction unit 40 as an example of a correction unit that corrects density unevenness. In this embodiment, the density unevenness correction unit 40 includes the four-color image forming unit 16, and thus corrects the density unevenness for each color. However, the following description focuses on one image forming unit 16. To do.

  The density unevenness correction unit 40 includes a correction control unit 46 that corrects density unevenness caused by various factors such as eccentricity of the photosensitive drum 18 and the magnetic roll in the developing device 26.

  The correction control unit 46 corrects the density unevenness by detecting the density unevenness and controlling the developing bias correction unit 44 and the exposure amount correction unit 43.

  The correction control unit 46 is connected to a density sensor 30, a development bias correction unit 44, and an exposure amount correction unit 43 as an example of a detection unit.

  In the detection of density unevenness, a predetermined test image is formed on the intermediate transfer belt 12, and the density of the formed image is directly detected by the density sensor 30, thereby detecting density unevenness in the sub-scanning direction. Note that the predetermined test image may have any shape as long as density unevenness in the sub-scanning direction can be detected.

  The correction control unit 46 calculates the development bias correction information calculated by the correction control unit 46 and the exposure amount correction information by the exposure device 24, and the development bias correction unit 44 and the exposure amount are calculated based on the calculated correction information. The correction unit 43 is controlled.

  The development bias correction unit 44 corrects the density unevenness by correcting the development bias of the development device 26 using the development bias correction information calculated by the correction control unit 46.

  The exposure amount correction unit 43 corrects the density unevenness in the main scanning direction by correcting the exposure amount of the exposure device 24 using the exposure amount correction information calculated by the correction control unit 46.

  In the present embodiment, the density unevenness in the circumferential direction (sub-scanning direction) of the photosensitive drum 18 that is the sub-scanning direction of the image by at least one of the method of correcting the exposure amount of the exposure device 24 and the method of correcting the developing bias. It is possible to correct. On the other hand, density unevenness in the axial direction (main scanning direction) of the photosensitive drum 18 that is the main scanning direction of the image cannot be corrected by the developing bias, and the exposure amount of the exposure device 24 needs to be corrected. However, when the correction range based on the exposure amount is narrow, correction may not be possible.

  Therefore, in the present embodiment, the correction control unit 46 controls the development bias correction unit 44 to correct the development bias, thereby correcting density unevenness in the sub-scanning direction, that is, a plurality of positions predetermined in the main scanning direction. The correction is performed so that the maximum absolute value of the amplitude of the density unevenness generated in the sub-scanning direction after correction becomes smaller. Here, the correction to be small means that the correction is small enough to be within the correction range in which the uneven density correction by the exposure amount correction unit 43 performed thereafter can be corrected. Then, after the maximum value of the absolute value of the density unevenness in the sub-scanning direction at each position is reduced, that is, after the variation in density unevenness in the sub-scanning direction at a plurality of main scanning direction positions is reduced, the correction control unit 46 controls the exposure amount correction unit 43 to correct the exposure amount, thereby correcting the density unevenness in the main scanning direction.

  As a method of correcting density unevenness in the sub-scanning direction, the length of one round of the magnetic roll in the photosensitive drum 18 and the developing device 26, which is a member contributing to density unevenness, is defined as a single width in the sub-scanning direction. The development bias may be set so that this is repeated in the sub-scanning direction, or the development bias may be set by defining one period of density unevenness as a single sub-scanning direction width. Good.

  In the present embodiment, for example, the main scanning direction is divided into a left region, a central region, and a right region, and as shown in FIG. 3, the amplitude of density unevenness in the sub-scanning direction in the left region before correction is 3, Assume that the amplitude of density unevenness in the sub-scanning direction in the central region in the scanning direction is 1, and the amplitude of density unevenness in the sub-scanning direction in the right region in the main scanning direction is 0. In this case, the correction is such that the development bias correction unit 44 cancels out the density unevenness of the amplitude 1.5 so that the maximum value of the amplitude of the density unevenness in the sub-scanning direction of each region after the correction becomes small. Apply the correction. Since the bias correction by the developing bias correction unit 44 is applied with the same intensity over the entire area in the main scanning direction, the intensity is corrected so that the density unevenness with an amplitude of 1.5 is canceled over the entire area. Thereby, the amplitude of density unevenness in the sub-scanning direction in the left area is 1.5, the amplitude of density unevenness in the sub-scanning direction in the central area is -0.5, and the amplitude of density unevenness in the sub-scanning direction in the right area is -1. .5 is corrected. Here, the amplitude is negative in terms of calculation, but this is a state where the amplitude is the same and the phase is opposite to that in the positive case. For example, density unevenness with an amplitude of −1.5 means density unevenness with the same amplitude and opposite phase as the density unevenness with amplitude 1.5. In other words, the absolute values of the amplitude are 1.5 for the left region, 0.5 for the central region, and 1.5 for the right region, respectively. The density unevenness that could not be corrected here is corrected by the exposure amount, but the maximum amplitude of the density unevenness that must be corrected by the exposure amount correction from 3 to 1.5 due to the correction by the development bias, and the remaining The correction range necessary for correcting the density unevenness is narrowed by 1.5. Then, after narrowing the correction range in this way, the exposure unevenness in the main scanning direction is corrected by correcting the exposure amount of the exposure device 24. That is, by correcting the developing bias, the correction range when correcting the exposure amount is narrowed to prevent insufficient correction.

  In the present embodiment, the main scanning direction will be described based on an example in which the left region, the central region, and the right region are divided into three. However, it is sufficient that the main scanning direction is divided into two or more. It can be appropriately selected depending on the unevenness correction accuracy. Further, uneven density in the sub-scanning direction at a predetermined position in each area may be detected, or average uneven density in each area may be detected.

  Next, a process performed when correcting the density unevenness in the image forming apparatus 10 according to the present embodiment will be described. FIG. 4 is a flowchart illustrating an example of a flow of processing performed when correcting density unevenness in the image forming apparatus 10 according to the first embodiment. Note that the process of FIG. 4 shows a part of the process when correcting the density unevenness. Further, the process of FIG. 4 may be started at the time of activation, a predetermined timing after each elapse of time, or may be started by a user instruction.

  In step 100, the image forming unit 16 forms a predetermined test image and proceeds to step 102. In this embodiment, since the image is formed with four colors C, M, Y, and K, a predetermined test image is formed for each color, and the following processing is performed for each color. As the test image, for example, a test image such as a strip-shaped image along the main scanning direction may be applied, or a test image of another shape may be applied.

  In step 102, the density sensor 30 detects the density of the test image and proceeds to step 104. Thus, the density unevenness in the axial direction of the photosensitive drum, which is the sub-scanning direction, in the three regions in the main scanning direction of the image is detected.

  In step 104, the correction control unit 46 calculates correction information for correcting the developing bias of the developing device 26 based on the density of the test image detected by the density sensor 30, and calculates it to the developing bias correcting unit 44. The correction information thus set is set, and the routine proceeds to step 106. In the present embodiment, development bias correction information is calculated so as to reduce the maximum absolute value of the amplitude of density unevenness in the sub-scanning direction in each corrected region, and is set in the development bias correction unit 44. The correction control unit 46 corrects the developing bias of the developing device 26 using the set correction information, whereby the detected absolute value of the absolute value of the density unevenness in the sub-scanning direction in the three regions in the main scanning direction is obtained. Get smaller.

  In step 106, the image forming unit 16 re-forms a predetermined test image using the correction information set in the developing bias correction unit 44 and proceeds to step 108.

  In step 108, the density sensor 30 detects the density of the test image again, and proceeds to step 110. That is, the difference in density unevenness in the sub-scanning direction in the three regions in the main scanning direction of the test image formed with the developing bias corrected is detected.

  In step 110, the correction control unit 46 determines whether the difference in density unevenness of the test image detected by the density sensor 30 is within a predetermined allowable range. Thus, it is determined whether or not further correction is necessary. If the determination is negative, the process proceeds to step 112. If the determination is positive, the difference in density unevenness is corrected by correcting the development bias. Since it is suppressed to within the allowable range, the processing is terminated as it is.

  In step 112, the correction control unit 46 calculates correction information for controlling the exposure amount of the exposure apparatus 24 based on the detection result of the density sensor 30 and sets the correction information in the exposure amount correction unit 43. Then, the exposure amount of the exposure device 24 is corrected, and the series of processes is completed. That is, the remaining density unevenness in the main scanning direction in which the correction range is narrowed is corrected by correcting the exposure amount of the exposure device 24.

  As described above, even when the exposure amount cannot be corrected only by correcting the exposure amount of the exposure device 24, the correction range for correcting the exposure amount by correcting the developing bias before correcting the exposure amount. By narrowing, the density unevenness in the main scanning direction is further corrected.

(Second Embodiment)
FIG. 5 is a block diagram illustrating a schematic configuration for correcting density unevenness in the image forming apparatus 10 according to the second embodiment. In addition, about the same structure as 1st Embodiment, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  In the first embodiment, the correction bias is corrected to narrow the density unevenness correction range in the main scanning direction, and then the exposure unevenness of the exposure device 24 is corrected to correct the density unevenness. Is narrow, the correction range cannot be narrowed only by the developing bias. Therefore, in the second embodiment, as a method for narrowing the correction range, at least one of correction of the charging bias of the charging device 22 and correction of the transfer bias of the transfer device is further added.

  That is, as shown in FIG. 5, the charging bias correction unit 48 and the transfer bias correction unit 50 are further connected to the correction control unit 46 in the first embodiment.

  The correction control unit 46 calculates charging bias correction information of the charging device 22 and correction information of the transfer bias of the primary transfer roll 28 for correcting the detected density unevenness, and the charging bias is calculated based on the calculated correction information. The correction unit 48 and the transfer bias correction unit 50 are further controlled.

  The charging bias correction unit 48 corrects the density unevenness by correcting the charging bias of the charging device 22 using the charging bias correction information of the charging device 22 for correcting the detected density unevenness.

  The transfer bias correction unit 50 corrects the density unevenness by correcting the transfer bias of the primary transfer roll 28 using the transfer bias correction information of the primary transfer roll 28 for correcting the detected density unevenness.

  In the present embodiment, when the correction range cannot be narrowed by the correction of the development bias correction unit 44 under the control of the correction control unit 46, the development bias and the charging bias are corrected. The charging bias and the transfer bias are corrected.

  Next, a process performed when correcting the density unevenness in the image forming apparatus 10 according to the present embodiment will be described. FIG. 6 is a flowchart illustrating an example of a flow of processing performed when correcting density unevenness in the image forming apparatus 10 according to the second embodiment. The process of FIG. 6 shows a part of the process when correcting the density unevenness, and the same processes as those in the first embodiment are denoted by the same reference numerals. Further, the processing of FIG. 6 may be started at the time of activation, a predetermined timing after each elapse of time, or may be started by an instruction of a user.

  In step 100, the image forming unit 16 forms a predetermined test image and proceeds to step 102. In this embodiment, since there are four colors C, M, Y, and K, a predetermined test image is formed for each color, and the following processing is performed for each color. As the test image, for example, a test image such as a strip-shaped image along the main scanning direction may be applied, or a test image of another shape may be applied.

  In step 102, the density sensor 30 detects the density of the test image and proceeds to step 103. Thus, the density unevenness in the axial direction of the photosensitive drum, which is the sub-scanning direction, in the three regions in the main scanning direction of the image is detected.

  In step 103, the correction control unit 46 determines whether or not the unevenness of density is within the correction range of the exposure amount only by correcting the developing bias, thereby determining whether or not the developing bias can be corrected. If the determination is affirmative, the process proceeds to step 104, and if the determination is negative, the process proceeds to step 114.

  In step 104, the correction control unit 46 calculates correction information for correcting the developing bias of the developing device 26 based on the density of the test image detected by the density sensor 30, and calculates it to the developing bias correcting unit 44. The correction information thus set is set, and the routine proceeds to step 106. In the present embodiment, development bias correction information is calculated so as to reduce the maximum absolute value of the amplitude of density unevenness in the sub-scanning direction in each corrected region, and is set in the correction control unit 46. The correction control unit 46 corrects the developing bias of the developing device 26 using the set correction information, whereby the detected absolute value of the absolute value of the density unevenness in the sub-scanning direction in the three regions in the main scanning direction is obtained. Get smaller.

  In step 106, the image forming unit 16 re-forms a predetermined test image using the correction information set in the developing bias correction unit 44 and proceeds to step 108.

  In step 108, the density sensor 30 detects the density of the test image again, and proceeds to step 110. That is, the difference in density unevenness in the sub-scanning direction in the three regions in the main scanning direction of the test image formed with the developing bias corrected is detected.

  In step 110, the correction control unit 46 determines whether the difference in density unevenness of the test image detected by the density sensor 30 is within a predetermined allowable range. Thus, it is determined whether or not further correction is necessary. If the determination is negative, the process proceeds to step 112. If the determination is positive, the difference in density unevenness is corrected by correcting the development bias. Since it is suppressed to within the allowable range, the processing is terminated as it is.

  In step 112, the correction control unit 46 calculates correction information for controlling the exposure amount of the exposure apparatus 24 based on the detection result of the density sensor 30 and sets the correction information in the exposure amount correction unit 43. Then, the exposure amount of the exposure device 24 is corrected, and the series of processes is completed. That is, the remaining density unevenness in the main scanning direction in which the correction range is narrowed is corrected by correcting the exposure amount of the exposure device 24.

  On the other hand, in step 114, the correction controller 46 determines whether the density unevenness is within the exposure amount correction range by the correction of the developing bias and the correction of the charging bias. If the determination is affirmative, the process proceeds to step 116, and if the determination is negative, the process proceeds to step 118.

  In step 116, the correction controller 46 calculates correction information for correcting each of the developing bias of the developing device 26 and the charging bias of the charging device 22 based on the density of the test image detected by the density sensor 30. Then, correction information is set in each of the developing bias correction unit 44 and the charging bias correction unit 48, and the process proceeds to step 106. That is, when the developing bias and the charging bias are corrected for the density unevenness in the sub-scanning direction in each region, the developing bias and the charging bias are set so that the maximum absolute value of the density unevenness in the sub-scanning direction is reduced. The correction information for each charging bias is calculated, and the correction information is set in each correction unit. Each of the developing bias correcting unit 44 and the charging bias correcting unit 43 corrects each of the developing bias and the charging bias using the set correction information, thereby suppressing the detected density unevenness. For example, the correction information for the developing bias and the correction information for the charging bias are calculated after the correction information for the developing bias is calculated, and then the correction information for the charging bias that is insufficient for the exposure amount correction range is calculated.

  In step 118, the correction control unit 46 corrects each of the developing bias of the developing device 26, the transfer bias, and the charging bias of the charging device 22 based on the density of the test image detected by the density sensor 30. Each correction information is calculated. Then, correction information is set in each of the developing bias correction unit 44, the transfer bias correction unit 50, and the charging bias correction unit 48, and the process proceeds to step 106. That is, when the development bias, transfer bias, and charging bias are corrected for the density unevenness amplitude in the sub-scanning direction in each region, the maximum absolute value of the density unevenness amplitude in the sub-scanning direction becomes small. As described above, correction information for each of the developing bias, the transfer bias, and the charging bias is calculated, and the correction information is set in each correction unit. The development bias correction unit 44, the transfer bias correction unit 50, and the charging bias correction unit 48 each correct the development bias, the transfer bias, and the charging bias using the set correction information, thereby detecting the detected density. Unevenness is suppressed. For each development bias, transfer bias, and charging bias correction information, for example, after calculating the development bias correction information, charging bias correction information that is insufficient for the exposure amount correction range is calculated. Further, transfer bias correction information corresponding to the exposure amount correction range is calculated.

  Note that the correction in the transfer bias cannot correct the image in the darkening direction, and thus the steps 114 and 118 may be omitted in the processing of FIG. That is, if the exposure bias correction range is not sufficient in step 103 and the exposure bias cannot be corrected in step 103, the process proceeds to step 116 to correct the charging bias in addition to the development bias. .

  As described above, in this embodiment, even if the developing bias is corrected, the charging bias and the transfer bias are corrected even if the exposure amount is corrected and the density unevenness in the main scanning direction is not within the correction range. Due to this correction, density unevenness is suppressed within the exposure amount correction range. Thereby, density unevenness in the main scanning direction is suppressed by correcting the exposure amount.

  In each of the above embodiments, the density sensor 30 detects the density of the image transferred to the intermediate transfer belt. However, the present invention is not limited to this. For example, it may be provided on the downstream side in the transport direction of the secondary transfer roll 32 in the paper transport path to detect the density of the image formed on the paper.

  In each of the above embodiments, an image forming apparatus that forms a color image has been described as an example. However, the present invention is not limited to this. For example, an image forming apparatus that forms a single color image by the single image forming unit 16 may be applied.

  Further, the processing performed by the image forming apparatus 10 according to each of the above embodiments may be processing performed by software, processing performed by hardware, or processing combining both. Further, the processing performed in the image forming apparatus 10 may be stored and distributed as a program in a storage medium.

  Further, the present invention is not limited to the above, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 16 Image forming part 18 Photosensitive drum 22 Charging apparatus 24 Exposure apparatus 26 Developing apparatus 28 Primary transfer roll 30 Density sensor 40 Density unevenness correction part 43 Exposure amount correction part 44 Development bias correction part 46 Correction control part 48 Charging Bias correction unit 50 Transfer bias correction unit

Claims (5)

A charging device for charging the image carrier with a charging bias;
An exposure device that exposes the charged image carrier to form a latent image; and
A developing device for developing the latent image with a developing bias to form a toner image on the surface of the image carrier;
A transfer device for transferring the toner image to a transfer medium by a transfer bias;
A detection unit that detects density unevenness of the toner image on the image carrier or the toner image transferred to the transfer medium;
Using the detection result of the detection unit, at least one of the charging bias, the developing bias, and the transfer bias is corrected to reduce variation in density unevenness in the sub-scanning direction at a plurality of predetermined positions in the main scanning direction. After that, a correction unit for correcting the exposure amount by the exposure apparatus,
An image forming apparatus including:   The correction unit corrects at least one of the charging bias, the development bias, and the transfer bias using the detection result of the detection unit, and corrects uneven density in the sub-scanning direction at the plurality of main scanning direction positions. The image forming apparatus according to claim 1, wherein the exposure amount is corrected after a maximum value falls within a predetermined allowable range.   The correction unit corrects the exposure amount after correcting the development bias to reduce variation in density unevenness in the sub-scanning direction using the detection result of the detection unit. The image forming apparatus described.   Even if the correction unit corrects the development bias using the detection result of the detection unit to reduce the variation in density unevenness in the sub-scanning direction, the variation in density unevenness in the sub-scanning direction is reduced by the exposure amount. 4. The image forming apparatus according to claim 1, wherein the exposure amount is corrected after correcting at least one of the charging bias and the transfer bias in a case where the exposure bias is not within the correction range. 5.   An image forming program for causing a computer to function as a detecting unit and a correcting unit of the image forming apparatus according to claim 1.