Image formation apparatus and image density adjustment method

Abstract

To allow density unevenness to be adjusted, even at the occurrence of density unevenness that cannot be dealt with by correcting image data.SOLUTION: An image formation apparatus 1 comprises: a density calculation section 51 for calculating a density for each main scan position, based on a read image of a density adjustment chart; a correction value calculation section 52 for calculating a density correction value for each main scan position with respect to image data, based on the density; a light amount change amount calculation section 53 for calculating a light amount change amount for each main scan position of a light source part of an image formation section, based on the density; and a control section 40 for performing change control of an output light amount of the light source part, according to a level of the density.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus and an image density adjusting method. [Background technology]

[0002] Image forming devices such as multifunction peripherals and printers use multiple laser light sources (e.g., laser diodes: LDs) to record images on recording materials at high speed. Laser beams from the multiple laser light sources are used to write a multi-line image onto the photoconductor in a single scan, thereby forming an image on the photoconductor. This image formation is repeated in the sub-scanning direction to form a page of image. Furthermore, in image forming devices, density can vary at each main scanning position due to various factors, resulting in density unevenness. To address this issue, a technology has been proposed for uniforming density by measuring density at each main scanning position, calculating a density correction value, and converting image data, such as that described in Patent Document 1.

[0003] Patent Document 1 describes identifying the minimum density from a plurality of pieces of input density information and setting the identified density as a target density. It also describes identifying the error between each of the densities identified from the plurality of pieces of input density information and the set target density. It also describes setting the amount of gradation correction for each position corresponding to the input density information based on the identified error. It also describes correcting the gradation of the image data based on the set amount of gradation correction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-191414 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, Patent Document 1 proposes a technology for adjusting the balance of image density by correcting image data. However, when the density correction value for image data is large, a problem may occur in which the correction value cannot be accommodated due to component performance limitations in the image forming unit. Furthermore, density unevenness may occur due to defects in printing components in the image forming apparatus. There is also a problem in that density unevenness caused by defects in printing components cannot be addressed by correcting image data. Therefore, the image density balance adjustment technology by correcting image data as described in Patent Document 1 cannot solve the above-mentioned problems.

[0006] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to be able to adjust the density balance even when density unevenness occurs that cannot be addressed by image data correction. [Means for solving the problem]

[0007] In order to solve the above problem, the image forming apparatus of the present invention includes a density calculation unit that calculates the density for each main scanning position based on the read image of the density adjustment chart, a correction value calculation unit that calculates a density correction value for each main scanning position for the image data based on the density, a light quantity change calculation unit that calculates the amount of change in light quantity for each main scanning position of the light source unit of the image forming unit based on the density, and a control unit that controls the change in the output light quantity of the light source unit based on the amount of change in light quantity depending on the level of density. The image forming apparatus described above is one aspect of the present invention, and the image density adjusting method that reflects one aspect of the present invention is configured in the same manner as the image forming apparatus described above. [Effects of the Invention]

[0008] According to the present invention having the above configuration, even if density unevenness occurs that cannot be addressed by image data correction, it is possible to adjust the density balance. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view showing an example of the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] 1 is a diagram showing an example of the configuration of an exposure device and its periphery in an image forming apparatus according to an embodiment of the present invention; [Figure 3] 1 is a block diagram illustrating an example of a functional configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 4] 10A and 10B are diagrams showing examples of density profiles of a plurality of gradations calculated in an image forming apparatus according to an embodiment of the present invention; [Figure 5] 10A and 10B are diagrams illustrating an example of a change in light amount calculated in an image forming apparatus according to an embodiment of the present invention. [Figure 6] 6A and 6B are diagrams showing density profiles of each tone after light amount adjustment in an image forming apparatus according to an embodiment of the present invention. [Figure 7] 5 is a diagram showing a procedure of an image density adjustment process in an image forming apparatus according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functions or configurations are designated by the same reference numerals, and redundant description will be omitted.

[0011] <One embodiment> [Configuration example of image forming device] First, a configuration example of an image forming apparatus according to an embodiment of the present invention will be described. Fig. 1 is a schematic cross-sectional view showing a configuration example of an image forming apparatus 1 according to this embodiment.

[0012] The image forming apparatus 1 is an example of an image forming apparatus that forms an image on a recording material by electrophotography. The image forming apparatus 1 is a multifunction digital image forming apparatus (MFP: Multifunction Peripheral) that has multiple functions, such as a print function, a copy function, a facsimile function, and a scan function. The image forming apparatus 1 forms an image on a recording material based on document image data obtained by reading an image from a document or document image data received from an external terminal device. Hereinafter, the recording material will also be referred to as "paper."

[0013] As shown in FIG. 1, the image forming apparatus 1 includes a reading unit 12, an image forming unit 13, an operation display unit 15, a manual feed tray T1, a paper feed tray T2, and a paper discharge tray T3.

[0014] The reading unit 12 scans and exposes an image of a document placed on a document table or an automatic document feeder (ADF) (not shown) using the optical system of a scanning exposure device, reads the reflected light using a line image sensor, and outputs the read image.

[0015] The image forming unit 13 forms an image on the paper P according to the pixel value of each pixel in the document image data. The image forming unit 13 has four image writing units 131 for forming toner images of four colors, cyan (C), magenta (M), yellow (Y), and black (K), respectively. The image writing units 131 include image writing units 131Y, 131M, 131C, and 131K shown in FIG. 1. The image forming unit 13 also includes an intermediate transfer belt 132, a transfer roller 133 (secondary transfer roller), a fixing unit 134, and the like. Hereinafter, the image writing units 131Y, 131M, 131C, and 131K may be referred to collectively or without any particular distinction being made therebetween as the image writing unit 131.

[0016] The four image writing units 131Y, 131M, 131C, and 131K are arranged in series (tandem) along the belt surface of the intermediate transfer belt 132. The four image writing units 131Y, 131M, 131C, and 131K form images of the respective colors of C, M, Y, and K. The image writing units 131 have the same configuration except for the colors of the images they form. As shown in FIG. 1, the image writing unit 131 includes an exposure device 131a and a photosensitive member 131b (an example of an image carrier). The image writing unit 131 also includes a developing unit 131c, a charging unit 131d, a cleaning unit 131e, and a primary transfer roller 131f.

[0017] During image formation processing, the charging unit 131d in each image writing unit 131 charges the outer peripheral surface of the drum-shaped photoconductor 131b. Then, the charging unit 131d scans the outer peripheral surface of the photoconductor 131b with a light beam (light beam) emitted by the exposure device 131a based on the document image data, forming an electrostatic latent image. In this state, when the developing unit 131c supplies a color material such as toner and develops it, an image is formed on the outer peripheral surface of the photoconductor 131b.

[0018] The primary transfer roller 131f primarily transfers the image formed on the photosensitive member 131b onto the intermediate transfer belt 132, superimposing the image onto the intermediate transfer belt 132. As a result, an image made up of each color is formed on the intermediate transfer belt 132. The intermediate transfer belt 132 is an image carrier that is wound around multiple rollers and rotates. After the primary transfer, the cleaning unit 131e removes color material remaining on the photosensitive member 131b.

[0019] Furthermore, intermediate transfer belt 132 feeds paper from manual feed tray T1 or paper feed tray T2 in time with the timing at which it reaches the position of transfer roller 133. Transfer roller 133 is one of a pair of rollers, one of which is in pressure contact with intermediate transfer belt 132 and the other of which winds around intermediate transfer belt 132. The pressure of transfer roller 133 causes a second transfer of an image from intermediate transfer belt 132 onto the paper.

[0020] The paper is then transported to the fixing unit 134, where it is subjected to a fixing process and then discharged to the paper output tray T3. The fixing process involves applying heat and pressure to the paper with the fixing roller 134a to fix the image to the paper. When forming images on both sides of the paper P, the paper is transported to the reversing path 135 to reverse the paper surface, and then the paper is fed again to the position of the transfer roller 133.

[0021] The operation display unit 15 is composed of a display unit and an operation unit. The display unit is composed of a display device such as an LCD (Liquid Crystal Display) or an organic EL (Electro-luminescence) display. The operation unit is composed of a touch sensor or the like. The display unit and operation unit are integrally formed, for example, as a touch panel. The operation display unit 15 generates an operation signal representing the operation content input by the operator to the operation unit, and supplies the operation signal to a control unit 40 (see FIG. 3 described below) described later. Furthermore, the operation display unit 15 displays the operation content by the operator, setting information, etc. on the display unit based on a display signal supplied from the control unit 40 described later. It is also possible to configure the operation unit as a mouse, tablet, etc., separately from the display unit.

[0022] Next, an example of the configuration of an exposure device and its periphery in the image forming apparatus 1 will be described. Fig. 2 is a diagram showing an example of the configuration of an exposure device and its periphery in the image forming apparatus 1 according to this embodiment. The exposure device 131a shown in Fig. 2 is an exposure device for the image writing section 131, and the exposure devices for the other writing units also have a similar configuration. Fig. 2 describes an example in which one light source (laser diode) is used for one scan.

[0023] 2, the exposure device 131a includes a light source unit 21, an optical system 22a, and a polygon mirror 23. The exposure device 131a also includes an optical system 22b, a first optical sensor 24, a second optical sensor 25, a detection circuit 30, and a control unit 40.

[0024] The light source unit 21 has a laser diode 21L and a driver circuit 21D. The laser diode 21L (an example of a light source) is a light source that emits laser light. The spot diameter of the laser light emitted from the laser diode 21L and scanned increases as the ambient temperature decreases, and decreases as the ambient temperature increases.

[0025] The optical system 22a is a group of various lenses arranged between the laser diode 21L and the polygon mirror 23. The optical system 22b is a group of various lenses arranged between the polygon mirror 23 and the photosensitive element 131b, the first optical sensor 24, and the second optical sensor 25. For example, an fθ lens is used in the optical systems 22a and 22b.

[0026] The polygon mirror 23 (an example of a scanning unit) is an element having an axis perpendicular to the axis of the photosensitive member 131b, a polygonal cross section perpendicular to the axis, and mirrors on its side faces. The polygon mirror 23 rotates around its axis and scans the laser light emitted from the laser diode 21L along the axial direction (main scanning direction) of the photosensitive member 131b.

[0027] The first optical sensor 24 is a sensor that receives the laser light scanned by the polygon mirror 23 in order to generate a main scanning synchronization signal. The first optical sensor 24 is disposed at a position upstream of the photosensitive element 131b on the line scanned by the laser light (upstream in the scanning direction). When the laser light is incident on the first optical sensor 24, the first optical sensor 24 induces an output voltage corresponding to the light amount (e.g., lm·S) and outputs it as a first detection signal. The first optical sensor 24 can detect the timing when the spot of the laser light passes that position.

[0028] The second optical sensor 25 is disposed at a position downstream (downstream in the scanning direction) of the photosensitive element 131b on the line scanned by the laser light. When the laser light is incident on the second optical sensor 25, it induces an output voltage according to the amount of light and outputs it as a second detection signal. The second optical sensor 25 can detect the timing when the spot of the laser light passes that position. The first optical sensor 24 and the second optical sensor 25 have the same specifications. The first detection signal and the second detection signal may be collectively referred to as the detection signal. The detection circuit 30 detects a detection signal including the first detection signal and the second detection signal and outputs it to the control unit 40.

[0029] The driver circuit 21D is a circuit that drives the laser diode 21L. The driver circuit 21D controls the laser diode 21L to emit laser light based on a drive signal (light intensity command value) for image formation input from the control unit 40. The driver circuit 21D follows instructions from the control unit 40 and controls the light intensity of the laser diode 21L using, for example, an automatic power control circuit or an automatic current control circuit based on a reference voltage.

[0030] 2 shows the light source unit 21 having one laser diode 21L and one driver circuit 21D. In reality, the light source unit 21 may be equipped with a plurality of laser diodes 21L. In this case, the polygon mirror 23 scans in the main scanning direction with each of a plurality of laser beams (spot beams) emitted from the plurality of laser diodes 21L at different positions in the sub-scanning direction.

[0031] [Example of functional configuration of image forming device] Next, the functional configuration of the image forming apparatus 1 will be described. Fig. 3 is a block diagram showing an example of the functional configuration of the image forming apparatus 1 according to this embodiment. In addition to the components shown in Figs. 1 and 2, the image forming apparatus 1 includes a density calculation unit 51, a correction value calculation unit 52, and an image data conversion unit 54 shown in Fig. 3. The image forming apparatus 1 also includes a light amount change amount calculation unit 53, and a storage unit 60. The components of the image forming apparatus 1 are connected via a bus B so as to be able to send and receive information data to and from each other.

[0032] The control unit 40 is configured to include a CPU (Central Processing Unit), RAM (Random Access Memory), etc. (not shown). The CPU reads various processing programs stored in the storage unit 60, loads them into the RAM, and controls the operation of each component of the image forming apparatus 1. Note that a GPU (Graphics Processing Unit) may be used instead of the CPU, or a CPU and a GPU may be used together.

[0033] The density calculation unit 51 acquires, from the storage unit 60, a read image of the density adjustment chart read by the reading unit 12. The density calculation unit 51 also calculates the density for each main scanning position based on the read image of the density adjustment chart. The density calculation unit 51 also outputs the calculated density for each main scanning position to the correction value calculation unit 52 and the light amount change calculation unit 53. If the density adjustment chart supports multiple gradation settings, the density calculation unit 51 calculates the density for each main scanning position for each of the multiple gradations.

[0034] The correction value calculation unit 52 calculates a density correction value for correcting density unevenness for each main scanning position in the image data based on the density for each main scanning position. Specifically, the correction value calculation unit 52 calculates a density correction value for each main scanning position based on the density at each main scanning position and a predetermined density reference value. The correction value calculation unit 52 also outputs the calculated density correction value to the control unit 40. Note that if the density adjustment chart supports multiple gradation settings, the correction value calculation unit 52 calculates a density correction value for each main scanning position for each of the multiple gradations. Hereinafter, the density correction value will also be referred to as an "image data correction value."

[0035] The light amount change amount calculation unit 53 calculates the amount of change in light amount for each main scanning position based on the density for each main scanning position, in order to change the output light amount of the light source unit 21 of the image forming unit 13. When the density adjustment chart corresponds to a plurality of gradation settings, the light amount change amount calculation unit 53 calculates the amount of change in light amount based on the average value of the densities of the plurality of gradations. The light amount change amount calculation unit 53 also outputs the calculated amount of change in light amount for each scanning position to the control unit 40. The calculation of the amount of change in light amount will be described later with reference to FIGS. 4 to 6. The light amount change amount calculation unit 53 may calculate the amount of change in light amount based on the density correction value calculated by the correction value calculation unit 52.

[0036] The image data conversion unit 54 converts the image data and adjusts the density balance based on the image data correction values ​​stored in the storage unit 60 in accordance with instructions from the control unit 40 .

[0037] In this embodiment, the control unit 40 controls the change in the output light amount of the light source unit 21 based on the amount of change in light amount in accordance with the density level calculated by the correction value calculation unit 52. Here, the density levels include a first level and a second level. The first level is a level at which the density at each main scanning position exceeds the correctable density range (correctable range) due to component performance limitations of the image forming unit. The second level is a level at which the density at each main scanning position is within the correctable range. If the first level exists among the density levels of each gradation, the control unit 40 controls the change in the output light amount of the light source unit 21 based on the amount of change in light amount calculated by the light amount change amount calculation unit 53. In controlling the change in the output light amount of the light source unit 21, the control unit 40 outputs an instruction to each driver circuit 21D to change the output light amount of each laser diode 21L of the light source unit 21 based on the amount of change in light amount at each scanning position. When the density level of each gradation is the second level, the control unit 40 performs conversion control of the image data based on the density correction value (image data correction value) calculated by the correction value calculation unit 52. The control unit 40 also performs control to change the output light amount of the light source unit 21 for main scanning positions within a predetermined range. The predetermined range is a range that includes all main scanning positions, or a range that includes main scanning positions corresponding to densities that exceed the correctable range.

[0038] The storage unit 60 is configured as a computer-readable, non-transitory recording medium storing a program executed by the CPU. The storage unit 60 is configured as a storage device such as an HDD (Hard Disk Drive). The storage unit 60 stores programs and data, such as programs for the CPU to control each unit, an OS (Operating System), and a controller. The storage unit 60 also stores the scanned image of the density adjustment chart scanned by the scanning unit 12. The storage unit 60 also stores the density calculated by the density calculation unit 51. The storage unit 60 also stores the density correction value (image data correction value) calculated by the correction value calculation unit 52 and the amount of light change calculated by the light amount change amount calculation unit 53. The computer-readable, non-transitory recording medium storing the program executed by the CPU is not limited to an HDD. For example, a solid state drive (SSD), a compact disc (CD)-ROM, a digital versatile disc (DVD)-ROM, or the like may be used.

[0039] Next, a method for calculating the amount of change in light quantity based on the density levels of multiple gradations will be described. Fig. 4 is a diagram showing an example of a density profile of multiple gradations calculated in the image forming apparatus 1 according to this embodiment. The horizontal axis in Fig. 4 represents the main scanning position (mm), and the vertical axis represents the image density.

[0040] FIG. 4 shows density profiles (densities for each main scanning position) corresponding to each of the four gradations, and their average values. FIG. 4 also shows a correctable region (region within a thick dashed line) determined by component performance limitations of the image forming unit. As shown in FIG. 4, the density levels corresponding to gradations K1 to K3 are the first level, i.e., levels where densities exceed the correctable region. The density level corresponding to gradation K4 is the second level, i.e., a level within the correctable region. If the first level exists among the density levels of each gradation, the light intensity change amount calculation unit 53 calculates the light intensity change amount for each scanning position based on the average density values ​​of the multiple gradations (see the thick solid line).

[0041] Image density and the change in the amount of light output from the laser diode 21L are proportional to each other, i.e., density = change in light amount × n, where n is a value determined by the characteristics of each component of the image forming unit 13 and is a parameter measured in advance. This proportional relationship is expressed as change in light amount = density × 1 / n. Note that the present invention is not limited to calculating the change in light amount based on density. For example, the change in light amount may be calculated based on a density correction value (image data correction value) calculated by the correction value calculation unit 52.

[0042] FIG. 5 is a diagram showing an example of the amount of change in light quantity calculated in the image forming apparatus 1 according to this embodiment. The horizontal axis in FIG. 5 represents the main scanning position (mm), and the vertical axis represents the amount of change in light quantity (%). The amount of change in light quantity shown in FIG. 5 is calculated based on the equation: amount of change in light quantity = average value of density of each gradation × 1 / n. Therefore, the characteristics of the amount of change in light quantity shown in FIG. 5 are the same as the characteristics of the average value of density of each gradation (see the thick solid line) shown in FIG. 4.

[0043] FIG. 6 is a diagram showing density profiles (densities at each main scanning position) corresponding to each gradation after light intensity adjustment in the image forming apparatus 1 according to this embodiment. The horizontal and vertical axes in FIG. 6 are the same as those in FIG. 4, and therefore will not be described again. The density profiles shown in FIG. 6 are density profiles for each gradation recalculated after changing the light intensity output from the light source unit 21 based on the light intensity change amount shown in FIG. 5. As shown in FIG. 6, the densities for each gradation after light intensity adjustment are within the correctable range. Note that in this embodiment, after changing the light intensity output from the light source unit 21, the control unit 40 controls the density calculation unit 51 and the correction value calculation unit 52 so that their processes are performed again. After changing the light intensity output from the light source unit 21, if the first level is present among the density levels for each gradation recalculated, the control unit 40 notifies the operator of an abnormality.

[0044] [Image density adjustment process procedure] Next, there will be described the procedure of the image density adjustment process in the image forming apparatus 1. Fig. 7 is a diagram showing the procedure of the image density adjustment process in the image forming apparatus 1 according to this embodiment.

[0045] First, the control unit 40 controls printing of a density adjustment chart (S10). In this process, the control unit 40 outputs an instruction to print a density adjustment chart to the image forming unit 13. In addition, the image forming unit 13 prints the density adjustment chart and outputs it to the reading unit 12 in accordance with the instruction from the control unit 40.

[0046] Next, the reading unit 12 reads the density adjustment chart and outputs the read image of the density adjustment chart to the density calculation unit 51 (S11).

[0047] Next, the density calculation unit 51 calculates the density for each main scanning position based on the read image of the density adjustment chart, and outputs the calculated density to the correction value calculation unit 52 and the light amount change amount calculation unit 53 (S12).

[0048] Next, the correction value calculation unit 52 calculates an image data correction value for each main scanning position based on the density at each main scanning position and a predetermined density reference value (S13).The correction value calculation unit 52 also outputs the calculated image data correction value to the control unit 40.

[0049] Next, the control unit 40 determines whether or not there is any density for each gradation that exceeds the correctable range (outside the correctable range) (S14). That is, the control unit 40 determines whether or not there is a first level among the density levels for each gradation. If there is a first level among the density levels for each gradation, the determination in S14 is YES. If the density level for each gradation is a second level (within the correctable range), the determination in S14 is NO.

[0050] When the control unit 40 determines that there is no density outside the correctable area (NO in S14), it performs the process of S22 described below.

[0051] On the other hand, if the control unit 40 determines that there is a density outside the correctable area (YES in S14), the process of S15 is executed. In the process of S15, the control unit 40 outputs an instruction to calculate the amount of change in light quantity to the amount of change in light quantity calculation unit 53. Furthermore, the amount of change in light quantity calculation unit 53 calculates the amount of change in light quantity at each main scanning position based on the amount of change in light quantity = average value of density of each gradation × 1 / n, and outputs the amount of change in light quantity to the control unit 40.

[0052] Next, the control unit 40 controls the change in the output light amount of the light source unit 21 based on the change in the light amount at each main scanning position, and controls the reprinting of the density adjustment chart (S16).

[0053] Next, the reading unit 12 reads the reprinted density adjustment chart and outputs the read image of the density adjustment chart to the density calculation unit 51 (S17).

[0054] Next, the density calculation unit 51 recalculates the image density for each main scanning position based on the read image of the density adjustment chart, and outputs the calculated image density to the correction value calculation unit 52 (S18).

[0055] Next, the correction value calculation unit 52 recalculates the image data correction value for each main scanning position based on the density at each main scanning position and a predetermined density reference value (S19).The correction value calculation unit 52 also outputs the calculated image data correction value to the control unit 40.

[0056] Next, the control unit 40 determines whether or not there is any density of each recalculated tone that exceeds the correctable range (outside the correctable range) (S20).

[0057] When the control unit 40 determines that there is no density outside the correctable area (NO in S20), it performs the process of S22, which will be described later.

[0058] On the other hand, if the control unit 40 determines that there is a density outside the correctable range (YES in S20), it notifies the operator of an abnormality (S21). In this process, the control unit 40 notifies the operator of the abnormal end of the image density adjustment process, for example, via the operation display unit 15. Note that the control unit 40 may also notify the operator of the abnormality via a terminal device connected to the image forming apparatus 1. After the process of S21, the image density adjustment process ends abnormally.

[0059] If the result of S14 is NO or S20 is NO, the control unit 40 stores the image data correction value calculated by the correction value calculation unit 52 in the storage unit 60 (S22).

[0060] Next, the control unit 40 converts the image data, i.e., controls correction of the image data (S23). In this process, the control unit 40 outputs an instruction to convert the image data to the image data conversion unit 54. The image data conversion unit 54 also acquires an image data correction value from the storage unit 60 and converts the image data based on the image data correction value. After the process of S23, the image density adjustment process ends normally.

[0061] Since image density differs depending on the type of recording material, the amount of change in light quantity also differs for each type of recording material. For this reason, the control unit 40 controls the image density adjustment process to be performed for each type of recording material used to print the density adjustment chart.

[0062] [effect] As described above, the image forming apparatus 1 controls the output light quantity of the light source unit 21 to change if the image density adjustment process detects a density that exceeds the correctable range due to component performance limitations of the image forming unit. The image forming apparatus 1 calculates the amount of change in light quantity for each main scanning position based on the density for each main scanning position, the density correction value, and the like. The image forming apparatus 1 also adjusts the output light quantity of the light source unit 21 based on the amount of change in light quantity for each main scanning position. By adjusting the light quantity for each main scanning position, the density falls within the correctable range, making it possible to perform density correction on the image data. Therefore, the image forming apparatus 1 of the present invention can adjust the density balance even if density unevenness that cannot be addressed by image data correction occurs.

[0063] The present invention is not limited to the above-described embodiment, and it goes without saying that various other applications and modifications are possible without departing from the gist of the present invention as set forth in the claims. For example, the above-described embodiment has described the configuration of an image forming apparatus in detail and specifically in order to clearly explain the present invention. The present invention is not necessarily limited to an image forming apparatus having all of the described configurations. In addition, it is possible to replace part of the configuration of the embodiment described here with the configuration of another embodiment. Furthermore, it is also possible to add the configuration of one embodiment to the configuration of another embodiment. In addition, it is also possible to add, delete, or replace part of the configuration of an embodiment with other configurations. In addition, the control lines and information lines shown are those that are considered necessary for the explanation, and do not necessarily show all the control lines and information lines in the product. In reality, it can be assumed that almost all components are interconnected.

[0064] In the above embodiment, the image forming apparatus 1 has been described as controlling the change in the amount of light output by the light source unit 21 when density unevenness occurs that cannot be addressed by image data correction. However, the present invention is not limited to this. For example, the image forming apparatus 1 may control the change in the amount of light output by the light source unit 21 when it determines that the cause of density unevenness is a defective part of the image writing unit 131 of the image forming unit 13. [Explanation of symbols]

[0065] 1...image forming apparatus, 12...reading unit, 13...image forming unit, 131...image writing unit, 15...operation display unit, 21...light source unit, 30...detection circuit, 40...control unit, 51...density calculation unit, 52...correction value calculation unit, 53...light quantity change amount calculation unit, 54...image data conversion unit, 60...storage unit

Claims

1. a density calculation unit that calculates the density for each main scanning position based on the read image of the density adjustment chart; a correction value calculation unit that calculates a density correction value for each main scanning position of the image data based on the density; a light amount change amount calculation unit that calculates a light amount change amount for each main scanning position of a light source unit of an image forming unit based on the density; a control unit that controls a change in the output light amount of the light source unit based on the amount of change in the light amount in accordance with the level of the density. Image forming device.

2. When the density adjustment chart corresponds to a plurality of gradation settings, the density calculation unit calculates the density for each of the plurality of gradations at each main scanning position; the correction value calculation unit calculates the density correction value for each of the plurality of gradations at each main scanning position; The light amount change amount calculation unit calculates the light amount change amount based on an average value of the densities of the plurality of gradations. The image forming apparatus according to claim 1 .

3. The levels of the density include a first level at which the density at each of the main scanning positions exceeds a correctable range due to component performance limitations of the image forming unit, and a second level at which the density at each of the main scanning positions is within the correctable range. The image forming apparatus according to claim 2 .

4. The control unit When the first level exists among the levels of the density of the plurality of gradations, a change control of the output light amount of the light source unit is performed based on the light amount change amount calculated by the light amount change amount calculation unit; When the level of the density of the plurality of gradations is the second level, conversion control of the image data is performed based on the density correction value calculated by the correction value calculation unit. The image forming apparatus according to claim 3 .

5. The control unit controls the change of the output light amount of the light source unit for the main scanning position within a predetermined range. The image forming apparatus according to claim 4 .

6. The predetermined range is a range that includes all of the main scanning positions, or a range that includes the main scanning positions that correspond to the densities that exceed the correctable region. The image forming apparatus according to claim 5 .

7. The control unit controls the density calculation unit and the correction value calculation unit so that the processes are performed again after changing the output light amount of the light source unit. The image forming apparatus according to claim 4 .

8. The control unit performs change control of the output light amount of the light source unit, and then issues an abnormality notification if the first level exists among the recalculated levels of the density of the plurality of gradations. The image forming apparatus according to claim 7 .

9. The light amount change amount calculation unit calculates the light amount change amount based on the density correction value for each main scanning position calculated by the correction value calculation unit. The image forming apparatus according to claim 1 .

10. The control unit controls the density calculation unit, the correction value calculation unit, and the light amount change calculation unit to perform processing, and controls the change in the output light amount of the light source unit, for each type of recording material used to print the density adjustment chart. The image forming apparatus according to claim 1 .

11. When the control unit determines that the density unevenness is caused by a defective part of the image forming unit, the control unit controls to change the output light amount of the light source unit. The image forming apparatus according to claim 1 .

12. calculating a density for each main scanning position based on a read image of the density adjustment chart; calculating a density correction value for each main scanning position of the image data based on the density; calculating a change in the amount of light from a light source unit of an image forming unit for each main scanning position based on the density; and performing a change control of the output light amount of the light source unit based on the amount of change in the light amount in accordance with the level of the density. Image density adjustment method.

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