The present disclosure relates to a shading correction for correcting density unevenness in a scanning direction.
In electro-photographic image forming apparatuses, density values which deviate from the intended value (hereinafter referred to as density unevenness) may occur in a scanning direction in which an output image is scanned, due to various factors in image forming processes (e.g., sensitivity unevenness of photosensitive drum and exposure unevenness of exposure device). As a technique for correcting such density unevenness in the output image in the scanning direction, there is known a control method of correcting the density unevenness in the output image by light amount correction of the exposure device, based on the density unevenness detected using a detection pattern (i.e., pattern used for detection). The control method is referred to as a main scanning shading by laser power (hereinbelow, referred to as LPWSHD).
In a technique proposed in Japanese Patent Application Laid-open No. 2019-2981, test patterns each having a density that is aimed to be brought closer to a target density under different environmental conditions (the test patterns have image densities different from each other) are formed on a recording medium. Density data of each of the test patterns on the recording medium is then obtained, and an average image density of each of the test patterns is obtained. From among these test patterns, the test pattern having the closest image density to the target image density is selected. A light quantity correction amount in an optimum density range is then determined by calculating an exposure correction value based on the selected density data of the test pattern. Thus, on the environmental condition that the temperature around the image forming apparatus is high, a test pattern having a target density under the high-temperature environment is selected. In contrast, on the environmental condition that the temperature around the image forming apparatus is low, a test pattern having a target density under the low-temperature environment is selected. This is because if the density of the test pattern changes depending on the environmental condition, the density unevenness cannot be corrected at a high accuracy.
As a density unevenness correction method in the scanning direction, there is also known a control method of correcting the density unevenness by generating a plurality of conversion conditions corresponding to different positions in the scanning direction. The control method is referred to as a main scanning shading by a look-up table (hereinbelow, referred to as LUTSHD).
Japanese Patent Application Laid-open No. 2021-24249 discusses a technique for preventing a pseudo contour due to an over correction and a technique for obtaining a high correction accuracy in the LUTSHD, by changing a correction reflection ratio depending on the number of sheets each with the test pattern formed thereon. A user sets the number of sheets to form the test pattern thereon. In the technique discussed in Japanese Patent Application Laid-open No. 2021-24249, an average value of density levels of a plurality of sheets is obtained. Thus, it can be regarded that data with a general density with the density deviation controlled is obtained as the number of sheets increases, and the correction reflection ratio is increased.
According to an aspect of the present disclosure, an image forming apparatus includes an image forming unit including a photosensitive member, a light source configured to expose the photosensitive member to light to form an electrostatic latent image, and a developing roller configured to develop the electrostatic latent image on the photosensitive member, and a controller. The controller is configured to control the image forming unit to form a detection image, obtain density data regarding density levels in a plurality of areas the detection image at a plurality of positions in a scanning direction in which the photosensitive member is scanned with the light from the light source, generate, based on the density data, a first image forming condition for forming a first test image in which a density unevenness in the scanning direction is adjusted, generate, based on the density data, a second image forming condition for forming a second test image in which the density unevenness in the scanning direction is adjusted, the second image forming condition being different from the first image forming condition, and control the image forming unit to form the first test image and the second test image, respectively based on the first image forming condition and the second image forming condition.
Further features of the present disclosure will become apparent from the following description with reference to the attached drawings.
A first embodiment of the present disclosure will be described below.
The image forming apparatus 100 is a color laser printer that forms an image using developers (toners) of yellow (Y), magenta (M), cyan (C), and black (K). The image forming apparatus 100 may be configured as any one of, for example, a printing apparatus, a printer, a copying machine, a multi-function peripheral (MFP), and a facsimile machine. Hereinbelow, letters Y, M, C, and K added to the respective trailing ends of reference symbols indicate that the colors of developers (toners) targeted by corresponding components are Y, M, C, and K, respectively. In the following descriptions, in a case where it is not necessary to distinguish colors, the reference symbols with the Y, M, C, and K omitted are used.
The image forming apparatus 100 includes four image forming units P (image forming unit PY, PM, PC, and PK) for forming images using toners of different colors (Y, M, C, and K), respectively. The image forming units PY, PM, PC, and PK are included in the printer unit 100B. As illustrated in
The image forming units PY, PM, PC, and PK each employ a similar configuration except that the toner colors used by developing devices 4Y, 4M, 4C, and 4K are different. In
The image reading unit 100A includes a document scanner 210 and an automatic document feeding device (hereinbelow, referred to as an ADF) 220. The document scanner 210 can perform image reading using “ADF reading” for reading the original document G fed by the ADF 220 and “document platen reading” for reading the original document G placed on a document platen glass 102.
The image reading unit 100A includes a light source 103, an optical system 104, and a reading sensor 105. The light source 103 emits light to the original document G. The emitted light is reflected by the original document G. The optical system 104 includes a lens and other components, and forms an image of the light reflected by the original document G onto a light receiving surface of the reading sensor 105. The reading sensor 105 is, for example, a Charge-Coupled Device (CCD) sensor, and receives the reflected light focused on the light receiving surface. The image reading unit 100A generates image data representing the image of the original document G corresponding to the reflected light received by the reading sensor 105, and transmits the generated image data to the printer unit 100B. The light source 103, the optical system 104, and the reading sensor 105 are integrally formed as a reading unit, and move in a direction indicated by an arrow illustrated in
The reading sensor 105 outputs luminance values corresponding to the received reflected light. In a case where shading is performed, the luminance values are converted into density values by an image processing unit 108.
As for the printer unit 100B, descriptions are mainly provided of Y components, since the M, C, and K components are similar to the Y components except for colors. The printer unit 100B performs image formation based on the image data generated by the image reading unit 100A. The printer unit 100B can also perform image formation based on image data received from an external apparatus via a network or a telephone line.
The printer unit 100B includes the control unit 110 for controlling the entire image forming apparatus 100. The control unit 110 includes a central processing unit (CPU) 111, a random access memory (RAM) 112, and a read-only memory (ROM) 113. The printer unit 100B further includes a printer control unit 109 for controlling an image forming operation (printing operation) using the image forming units PY, PM, PC, and PK. The configuration of the image forming apparatus 100 is not limited to the configuration having the printer control unit 109 to control the image forming operation, and, for example, may have a configuration in which the control unit 110 also controls the image forming operation.
The image forming units P each include a photosensitive drum (photosensitive member) 1, and components that are arranged near the photosensitive drum 1, namely, a charging device 2, an exposure device 3, the developing device 4, a potential sensor 5, a primary transfer roller 7, and a cleaning device 8. The photosensitive drum 1 rotates in an arrow R1 direction. The charging device 2 charges the surface of the photosensitive drum 1 to a predetermined potential.
The exposure device 3 emits a laser beam (light beam) based on the input image signal (input image data) to expose the photosensitive drum 1 by scanning the laser beam on the surface of the photosensitive drum 1. In this way, an electrostatic latent image is formed on the photosensitive drum 1 based on the input image data. The exposure device 3 includes a rotational multifaceted mirror (hereinbelow, referred to as a polygon mirror) for scanning the laser beam. The polygon mirror deflects the laser beam so as to scan the surface of the photosensitive drum 1 with the laser beam by emitting the laser beam to one of a plurality of reflection surfaces. The exposure device 3 functions as an exposure unit for exposing the photosensitive drum 1 to form the electrostatic latent image.
The developing device 4 includes a developing roller for bearing and supplying toner to the photosensitive drum 1, and develops the electrostatic latent image by attaching toner born on the developing roller to the electrostatic latent image on the photosensitive drum 1. In this way, a toner image is formed on the photosensitive drum 1. The potential sensor 5 is disposed near the photosensitive drum 1 and between the developing device 4 and the exposure position to which the exposure device 3 performs exposure. The potential sensor 5 can detect the potential of the electrostatic latent image formed on the photosensitive drum 1.
The primary transfer roller 7 presses the inner surface of the intermediate transfer belt 6 to form a primary transfer nip portion T1 between the photosensitive drum 1 and the intermediate transfer belt 6. The primary transfer roller 7 transfers the toner image born on the photosensitive drum 1 onto the intermediate transfer belt 6 by a transfer bias voltage being applied.
The cleaning device 8 collects toner remaining on the photosensitive drum 1 after the toner image is transferred onto the intermediate transfer belt 6.
The four color toner images each formed on the corresponding one of the photosensitive drums 1Y, 1M, 1C, and 1K in the image forming units PY, PM, PC, and PK are sequentially transferred onto the intermediate transfer belt 6 in an overlapped manner (primary transfer). Thus, a multi-color toner image including Y, M, C, and K is formed on the intermediate transfer belt 6.
The intermediate transfer belt 6 is supported by a tension roller 61, a drive roller 62, and an opposing roller 63, and is driven by the drive roller 62, and rotates at a predetermined speed in an arrow R2 direction. The toner image formed on the intermediate transfer belt 6 is conveyed, along with the rotation of the intermediate transfer belt 6, to a secondary transfer nip portion T2 of the intermediate transfer belt 6 and a secondary transfer roller 64. The toner image on the intermediate transfer belt 6 is transferred onto a sheet S by the secondary transfer roller 64. A cleaning device 68 collects toner remaining on the intermediate transfer belt 6 after the toner image is transferred onto the sheet S from the intermediate transfer belt 6.
The sheet S is fed and conveyed from a paper cassette 65 in synchronization with a timing at which the toner image on the intermediate transfer belt 6 reaches the secondary transfer nip portion T2. The sheet S can be referred to as, for example, recording paper, a recording material, a recording medium, a printing sheet, a transfer material, and transfer paper. The sheet S is separated from other sheets one by one by a separation roller 66, fed to a conveyance path, and conveyed through the conveyance path toward a registration roller pair 67. The registration roller pair 67 keeps the sheet S standby in a stopped state on the conveyance path, and is driven to feed the sheet S into the secondary transfer nip portion T2 in synchronization with the conveyance timing of the toner image on the intermediate transfer belt 6. In this way, the toner image on the intermediate transfer belt 6 is transferred onto the sheet S at the secondary transfer nip portion T2 (secondary transfer).
The sheet S with the toner image transferred thereon is conveyed to a fixing device 11 by a conveyance belt 10. The fixing device 11 applies heat and pressure to the toner image transferred on the sheet S to fix the toner image on the sheet S. After the fixing processing by the fixing device 11 is finished, the sheet S is discharged outside the image forming apparatus 100 (e.g., discharge tray).
The light amount control circuit 190 controls the light amount (power) of the laser beam output from the exposure device 3. The light amount control circuit 190 determines the light amount of the laser beam output from the exposure device 3 so that a desired image density can be obtained with respect to the laser drive signal. The light amount of the laser beam corresponds to the exposure amount by the exposure device 3, and is an example of an image forming condition. The pattern generator 192 holds image data for forming a test pattern, which is a pattern image used for density measurement described below.
The γ correction circuit 209 converts an input image signal (input values) included in the input image data into an output image signal (output values) by referring to a gradation correction table (γ LUT). The gradation correction table is a conversion table for converting the input values of the image data to correct the gradation characteristic of the image formed by the image forming unit P to an ideal gradation characteristic. The correspondence relationship between the output image signal and the density is obtained in advance and stored in the ROM 113. The gradation correction table generated based on the correspondence relationship is stored in the γ correction circuit 209.
The pulse-width modulation circuit 191 generates the laser drive signal based on the image signal that has been converted based on the gradation correction table and the light amount determined by the light amount control circuit 190 and has been output from the γ correction circuit 209. The laser drive signal is a pulse width modulation (PWM) signal, and used to modulate the laser beam output from the exposure device 3. The pulse-width modulation circuit 191 outputs, as the laser drive signal, a pulse signal with a pulse width (time width) corresponding to a density indicated by the input image signal for each pixel. The pulse width of the laser drive signal is wide for a high density pixel, narrow for a low density pixel, and middle for a middle density pixel.
The exposure device 3 forms on the photosensitive drum 1 an image (electrostatic latent image) with the gradation expressed using an area coverage modulation corresponding to the pulse width of the laser drive signal. More specifically, the laser beam source (semiconductor laser) of the exposure device 3 emits light only during a time period corresponding to the pulse width of the supplied laser drive signal. The laser beam source is driven longer as the density of the formation target pixel is higher, and driven shorter as the density of the formation target pixel is lower. Thus, a dot size (area) of the electrostatic latent image formed on the photosensitive drum 1 becomes different depending on the density of the pixel. In other words, the exposure device 3 exposes a longer range in the scanning direction for the high density pixel, and a shorter range in the scanning direction for the low density pixel. In the present exemplary embodiment, the scanning direction is orthogonal to the sheet conveyance direction. Hereinbelow, the scanning direction is described as a main scanning direction. A sub scanning direction is a sheet conveyance direction, that is, a direction orthogonal to the main scanning direction.
A density sensor 12 is provided near the photosensitive drum 1 and between the developing device 4 and the primary transfer nip portion T1. The density sensor 12 is a photosensor for detecting the density of the toner image formed on the photosensitive drum 1. The control unit 110 (CPU 111) can measure the density of the toner image formed on the photosensitive drum 1, using the density sensor 12.
In the present embodiment, the control unit 110 (CPU 111) obtains measurement data indicating a measurement result of a test pattern density and performs processing based on the measurement result, by performing the “document platen reading” or the “ADF reading” using the image reading unit 100A. The control unit 110 (CPU 111) further controls generation of the test pattern for the density unevenness correction with the printer unit 100B, as well as correction of the exposure amount of the exposure device 3 in the image formation by the printer unit 100B.
The image forming apparatus 100 corrects the density unevenness in the main scanning direction occurring in the image (output image) formed by the printer unit 100B using a shading function included in the exposure device 3. The exposure device 3 can adjust the strength (exposure amount) of the laser beam output from the laser beam source, using the shading function. The density unevenness in the main scanning direction occurring in the output image can be corrected by adjusting (correcting) the light amount of the laser beam based on the density unevenness in the main scanning direction to occur in the output image.
In the image forming apparatus 100, an image formation area in which an image is formed by scanning the laser beam in the main scanning direction is divided into a plurality of areas each with an equal length in the main scanning direction, and the light amount setting (LPW) of the exposure device 3 is determined for each divided area. For example, the image formation area is divided into 14 areas of A to N (refer to
The above-described exposure correction amount ΔLPW is obtainable based on the γ characteristic of the image forming engine equivalent to the density characteristic indicating the correspondence relationship between a light amount setting value of the exposure device 3 and the density value of the output image. In a case where the exposure correction amount ΔLPW is determined for each area described above using the γ characteristic determined in advance to be the γ characteristic, the correction accuracy of the density unevenness may decrease with a change in the γ characteristic of the image forming engine.
The state of the image forming apparatus 100 includes a potential characteristic of the photosensitive drum, a toner charging characteristic, an attachment tolerance of each component, a potential of the photosensitive drum at a time of image formation, and an exposure amount of the laser beam at a time of image formation. For example, as illustrated in
Thus, the image forming apparatus 100 initially outputs a density unevenness detection pattern, and determines a plurality of exposure correction amounts ΔLPW based on the measurement result of the pattern. The image forming apparatus 100 outputs a plurality of the patterns corresponding one-to-one to the plurality of exposure correction amounts ΔLPW, and corrects the density unevenness accurately, by selecting an appropriate exposure correction amount ΔLPW from among the plurality of patterns. In this case, the plurality of patterns (a plurality of test images) corresponding to the plurality of exposure correction amounts ΔLPW is used for determining the correction amount, and used for determination of a gain serving as a correction condition for increasing or decreasing of the correction amount of the exposure amount.
Next, a description will be provided of correction processing for correcting the density unevenness in the main scanning direction that occurs in the image (output image) formed by the printer unit 100B. This correction processing is performed by the control unit 110 of the image forming apparatus 100.
The control unit 110 initially displays a screen 231 illustrated in
In step S102, in response to the user placing the sheet S with the density unevenness detection pattern 50 formed thereon on the image reading unit 100A and pressing the button 242 on the screen 232, the control unit 110 controls the image reading unit 100A to read the density unevenness detection pattern 50 on the sheet S. In this way, the control unit 110 obtains a read result, read by the reading sensor 105, for the image (density unevenness detection pattern 50) on the sheet S. In this case, the user can select a reading mode to be used by the image reading unit 100A from the “document platen reading” and the “ADF reading”.
Next, in step S103, the control unit 110 obtains density values in areas A to N (density data) in the main scanning direction for each of the band images in the density unevenness detection pattern 50, and stores the density values of the areas A to N of each of the band images in the main scanning direction in the RAM 112 as a density profile. The density profile is a detection result detected as information regarding the density of the density unevenness detection pattern 50. In step S103, since the signal output from the reading sensor 105 has a signal value (luminance value) corresponding to the luminance, the control unit 110 obtains the density value converted from the luminance value by the image processing unit 108.
Hereinbelow, a description is provided of a method of correcting the density unevenness of the yellow image based on the density profile of the yellow band image, from among the density profiles of the band images of four colors (Y, M, C, and K). The methods of correcting the density unevenness of the other color images from the density profiles of the band images of the other colors (M, C, and K) are similar to that for the yellow image.
In step S104, the control unit 110 calculates an average density value, which is an average value of the density values of the areas A to N based on the density profile stored in the RAM 112, and calculates a difference value (density difference ΔD) between the average density value and each of the density values of the areas A to N. The distribution of the density differences ΔD for each of the band images equates to the distribution of the density unevenness in the main scanning direction occurring in the output image. The density difference ΔD of each of the areas A to N equates to the density correction value in the correction processing of the density unevenness of the output image. The average density value is a target density value (target data) in the correction processing. Here, the density target value (target data) is not limited to the average density value. The density target value (target data) may be, for example, a predetermined density value.
Next, as illustrated in
In step S106, after the user presses the button 243 on the screen 233, the control unit 110 controls the printer unit 100B to print on the sheets S the correction amount determination patterns 91 to 95 illustrated in
Instead of the correction amount determination patterns 91 to 95, the correction amount determination pattern 96 based on the plurality of gains, illustrated in
After the correction amount determination patterns 91 to 95 (or the correction amount determination pattern 96) are printed, the control unit 110 displays a screen 234 illustrated in
In step S107, if the button 244 is pressed on the screen 234 (YES in step S107), the control unit 110 determines that the automatic adjustment of the exposure correction amounts ΔLPW is selected, and the processing proceeds to step S108. In the case where automatic adjustment is selected, the control unit 110 displays a screen 235 illustrated in
Here, the user may select the “document platen reading” or the “ADF reading” to read by the image reading unit 100A the sheets S with the correction amount determination patterns 91 to 95 (or the correction amount determination pattern 96) formed thereon. In a case where the “document platen reading” is selected by the user, the image reading unit 100A reads the correction amount determination patterns 91 to 95 (or the correction amount determination pattern 96) formed on the sheets S placed on the document platen glass 102. In a case where the “ADF reading” is selected by the user, the image reading unit 100A reads the correction amount determination patterns 91 to 95 (or the correction amount determination pattern 96) formed on the sheets S while feeding the sheets S, placed on the tray of the ADF 220, one by one. Thus, in the case where the correction amount determination patterns 91 to 95 are formed on the plurality of separate sheets S, the “ADF reading” is suitable.
In step S109, the control unit 110 determines a profile with the smallest difference between a maximum density and a minimum density from the plurality of density profiles after correction (profiles 1 to 5). In step S111, the control unit 110 determines the exposure correction amount ΔLPW that has been used to generate the profile. For example, in
Next, a case where the manual adjustment is selected in step S107 will be described. In a case where the button 245 is pressed on the screen 234, the control unit 110 determines that the manual adjustment of exposure correction amount ΔLPW is selected. If the manual adjustment is selected (NO in step S107), the processing proceeds to step S110. In step S110, the control unit 110 displays a screen 236 illustrated in
After determining the exposure correction amount ΔLPW in step S111, the control unit 110 ends the processing of the flowchart in
Using the image forming apparatus 100 in a plurality of different states X and Y, an effect of correction of the exposure unevenness in the main scanning direction which occurs in the output image, in a case where the correction processing described above is applied to the image forming apparatus 100 in the state X or Y, will be described.
According to the correction processing in the present embodiment, the optimum correction amount is selected using the correction amount determination patterns 91 to 95 (or the correction amount determination pattern 96). Thus, the exposure correction amount ΔLPW3 is selected in the state X, and the exposure correction amount ΔLPW2 is selected in the state Y, for example. This enables appropriate control of the density unevenness in the main scanning direction in any of the states X and Y in the correction processing.
A second embodiment of the present disclosure will be described below. The image forming apparatus 100 according to the first embodiment executes a main scanning shading (referred to as LPWSHD) to correct the density unevenness by changing the laser power irradiating a plurality of areas on the photosensitive drum 1 in the main scanning direction. The main scanning shading that corrects the density unevenness in the main scanning direction includes, in addition to the LPWSHD, a method of correcting the density unevenness in the main scanning direction by creating look-up tables (LUTs) corresponding one-to-one to the plurality of areas on the photosensitive drum 1 (such a method is referred to as look-up table shading [LUTSHD]). The LUTSHD can correct the density unevenness with different gradation levels highly accurately compared with the LPWSHD. Hereinbelow, the image forming apparatus 100 that executes the LUTSHD as correction processing will be described. In addition, components similar to those of the first embodiment are assigned the same numbers and the detailed descriptions thereof are omitted.
The control unit 110 converts the image data to correct the density unevenness in the main scanning direction of the image to be formed. In order to correct the density unevenness in the main scanning direction, the control unit 110 converts the image data based on a plurality of LUTs corresponding one-to-one to a plurality of positions in the main scanning direction (main scanning positions). Each of the LUTs is a one-dimensional table indicating a correspondence relationship between the input image signal (image signal value before conversion) and the output image signal (image signal value after conversion).
The density unevenness detection pattern for the LUTSHD has a limited number of gradation levels, so that if the correction is performed using the measurement result, the continuousness of the density and the continuousness of the gradation may be lost in the undetected gradation. As a result, there is a possibility that the pseudo contour occurs in the formed image.
To prevent or reduce the occurrence of the pseudo contour, the correction result needs to be controlled using the correction reflection ratio serving as a correction condition. The correction reflection ratio is a coefficient expressing a ratio to be reflected on the correction amount from the measurement result of the image density. If the correction reflection ratio is 100% (coefficient is 1), the image signal value after conversion is determined so that the difference between the density of the read result and the ideal density is “0”. If the correction reflection ratio is 80%, the image signal value after conversion is determined so that 80% (coefficient is 0.8) of the difference between the density of the read result and the ideal density is corrected. The correction reflection ratio is stored, for example, in the ROM 113, and used when the image density is measured.
Thus, lowering the correction reflection ratio controls the occurrence of pseudo contour. However, the effect of correcting the density unevenness decreases with the lowered correction reflection ratio. Thus, the image forming apparatus 100 forms a density unevenness detection pattern for the LUTSHD, and calculates, based on the measurement result of the pattern, LUTs corresponding to each of the plurality of areas in the main scanning direction for every plurality of correction reflection ratios. The correction accuracy of the density unevenness is improved while controlling the occurrence of the pseudo contour, by outputting the correction amount determination pattern on which the LUTs corresponding to the plurality of areas in the main scanning direction are reflected, and selecting appropriate LUTs corresponding to the plurality of areas in the main scanning direction.
Next, a description will be provided of correction processing for correcting the density unevenness in the main scanning direction which occurs in the image (output image) formed by the printer unit 100B. This correction processing is performed by the control unit 110 of the image forming apparatus 100. In the LUTSHD, the density unevenness detection pattern 51 is formed on the sheet S as the density unevenness detection pattern.
The control unit 110 stores in the RAM 112 density values obtained from the density values in the areas 1 to 32 (
The control unit 110 determines an average density value that is an average value of the density values in the areas 1 to 32, and a density difference ΔD that is a difference between the average density value and each of the density values in the areas, based on the density profiles stored in the RAM 112. The distribution of the density differences ΔD with respect to the average density value in the main scanning direction for each of the band images equivalents to the density unevenness in the main scanning direction occurring in the output image. The density difference ΔD for each of the areas 1 to 32 equivalents to the density correction amount in the correction processing of the density unevenness of the output image, and the average density value equivalents to the density target value (target data) in the correction processing. The density target value (target data) is not limited to the average density value. The density target value (target data) may be, for example, a predetermined density.
The control unit 110 generates LUTs corresponding one-to-one to the plurality of areas in the main scanning direction based on the density profile and a plurality of correction reflection ratios (60%, 70%, 80%, 90%, and 100%). The correction amount determination pattern is formed on the plurality of sheets S based on the LUTs corresponding one-to-one to the plurality of areas in the main scanning direction.
The control unit 110 generates a density profile based on each of the correction reflection ratios of the LUTSHD. The control unit 110 determines whether the pseudo contour has occurred for the density profile for each of the generated correction reflection ratios.
<Effect of Density Unevenness Correction through Image Data Conversion>
Next, using the image forming apparatus 100 in different states a and (3, a description will be provided of a correction effect obtained by increasing the correction accuracy of the density unevenness while controlling the occurrence of the pseudo contour, in a case where the correction processing for the LUTSHD is applied to the image forming apparatus 100 in each state.
In contrast, the correction amount with a higher correction reflection ratio is selectable while controlling the occurrence of the pseudo contour, in the correction processing for the image forming apparatus 100 in each state. More specifically, 70% is selectable as the correction reflection ratio in the state α, and 90% can be selected as the correction reflection ratio in the state β. In this way, in the correction processing, each of the density values in the density profile after correction is correctable to a value close to the average density value in each of the states α and βwhile controlling the occurrence of the pseudo contour.
The density profiles in the first and second embodiments have been described to be values converted from the luminance values of the pattern into the density levels. However, a luminance profile may be used instead of the density profile.
According to the present disclosure, the test image in which the density unevenness in the main scanning direction is corrected in different levels is printable. Thus, it is possible to control the occurrence of a new density unevenness caused by the correction amount of the density unevenness excessively increasing. It is also possible to control the occurrence of a situation in which the density unevenness is not sufficiently reduced because of the insufficient correction amount of the density unevenness. It is yet also possible to save the user from having to repeat many times the control of correcting the density unevenness caused by the excessive correction amount or insufficient correction amount being set.
Embodiment(s) of the present disclosure can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.
While the present disclosure has been described with reference to embodiments, it is to be understood that the disclosure is not limited to the disclosed embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of priority from Japanese Patent Application No. 2021-199626, filed Dec. 8, 2021, which is hereby incorporated by reference herein in its entirety.
Number | Date | Country | Kind |
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2021-199626 | Dec 2021 | JP | national |