JP6890772B2 - Image forming apparatus, image forming method and image forming program - Google Patents

Description

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

Various techniques have been proposed to suppress the edge effect, which is a phenomenon in which toner as a developer is concentrated on the edge portion (edge portion) of an image region and the density of the image becomes non-uniform. Specifically, for example, Patent Document 1 describes an edge detecting means for detecting an edge portion of output image data and an edge correcting means for performing density correction on the edge portion data detected by the edge detecting means. We are proposing an exposure unit control device equipped with. Patent Document 2 has a means for estimating the amount of transferred toner (also referred to as the amount of adhered toner in the present specification) from the cumulative value of image data and appropriately controlling the amount of heat, and is an image in which power consumption is reduced. In the forming apparatus, we propose a technique capable of outputting a good image without deteriorating the fixing property of the image even if the line widths of the images are different. Patent Document 3 detects an end portion in which peripheral pixels have a predetermined gradation difference pattern, and for each attention pixel in a predetermined range from the end portion, the pixel value of a predetermined pixel region in front of the attention pixel is set. We are proposing a technique for adjusting the amount of toner in the pixel of interest based on the difference between the total sum and the sum of the pixel values in the pixel region behind the pixel of interest.

Japanese Unexamined Patent Publication No. 2009-118378 Japanese Unexamined Patent Publication No. 5-333728 Japanese Unexamined Patent Publication No. 2014-068084

However, the inventor of the present application has newly found that the range of the edge effect fluctuates according to the rotation speed of the photoconductor in the electrophotographic development performed on the photoconductor in the unsaturated state.

The present invention has been made in view of such a situation, and provides a technique for appropriately reducing the edge effect according to the rotation speed of the photoconductor in an electrophotograph developed with a photoconductor in an unsaturated state. With the goal.

The image forming apparatus of the present invention includes a photoconductor that can rotate at a plurality of peripheral speeds, an exposure unit that exposes the photoconductor to form an electrostatic latent image based on image data, a magnetic roller, and a developing roller. A toner layer having a thickness corresponding to the difference in the potential difference between the magnetic roller and the developing roller is formed on the developing roller, and the developing bias potential and the electrostatic latency, which are the potentials of the developing roller, are formed. The first calibration process is executed by adjusting the developing unit for adhering toner from the toner layer to the photoconductor based on the image and the development bias potential of the developing unit within a preset adjustment range. A calibration unit that sets a dot area ratio for forming a solid image when the potential limit value is within the adjustment range in the first calibration process and executes the second calibration process, and the second calibration process. When the processing is executed, the rear end pixel group constituting the range to be corrected from the rear end pixels of the peripheral speed is specified according to the selection of any of the plurality of peripheral speeds, and the rear end pixels are specified. It is provided with an image processing unit that reduces the amount of toner adhering to the edge pixel group.

The image forming method of the present invention includes a photoconductor that can rotate at a plurality of peripheral speeds, an exposed portion that exposes the photoconductor to form an electrostatic latent image based on image data, a magnetic roller, and a developing roller. A toner layer having a thickness corresponding to the difference in potential difference between the magnetic roller and the developing roller is formed on the developing roller, and the developing bias potential and the electrostatic latent image, which are the potentials of the developing roller, are formed. Based on the above, the development step of adhering the toner from the toner layer to the photoconductor and the development bias potential of the development step are adjusted within a preset adjustment range to execute the first calibration process, and the first calibration process is executed. A calibration step of setting a dot area ratio for forming a solid image when the potential limit value within the adjustment range is reached in the calibration process of 1 and executing the second calibration process, and the second calibration process. When is executed, a rear end pixel group constituting a range to be corrected from the rear end pixels of the peripheral speed is specified according to the selection of any of the plurality of peripheral speeds, and the rear end is specified. It includes an image processing step of reducing the amount of toner adhering to the partial pixel group.

The present invention provides an image forming program for controlling an image forming apparatus that forms an image on an image forming medium according to image data. The image forming apparatus includes a plurality of photoconductors that can rotate at peripheral speed, an exposure unit that exposes the photoconductor to form an electrostatic latent image based on image data, a magnetic roller, and a developing roller. Then, a toner layer having a thickness corresponding to the toner layer forming potential difference between the magnetic roller and the developing roller is formed on the developing roller, and the developing bias potential which is the potential of the developing roller and the electrostatic latent image are formed. The image forming program includes a developing unit for adhering toner from the toner layer to the photoconductor based on the above, and the image forming program adjusts the developing bias potential of the developing unit within a preset adjustment range to perform the first calibration process. To execute the second calibration process by setting the dot area ratio for forming a solid image when the potential limit value within the adjustment range is reached in the first calibration process, and When the second calibration process is executed, a rear end pixel group forming a range to be corrected from the rear end pixels of the peripheral speed is selected according to the selection of any of the plurality of peripheral speeds. The image forming apparatus is made to function as an image processing unit that identifies and reduces the amount of toner adhering to the rear end pixel group.

According to the present invention, it is possible to appropriately reduce the edge effect according to the rotation speed of the photoconductor in an electrophotograph developed with a photoconductor in a non-saturated state.

It is a block diagram which shows the functional structure of the image forming apparatus 1 which concerns on one Embodiment of this invention. It is sectional drawing which shows the whole structure of the image forming apparatus 1 which concerns on one Embodiment. It is a side sectional view which showed the structure of the developing part 100 which concerns on one Embodiment of this invention. It is a conceptual diagram which shows the state that the rear end accumulation occurs in the development process which concerns on one Embodiment. It is a flowchart which shows the content of the half patch calibration processing procedure of the image forming apparatus 1 which concerns on one Embodiment. It is a flowchart which shows the content of the image formation processing procedure of the image formation apparatus 1 which concerns on one Embodiment.

Hereinafter, embodiments for carrying out the present invention (hereinafter, referred to as “embodiments”) will be described with reference to the drawings.

FIG. 1 is a block diagram showing a functional configuration of an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 includes a control unit 10, an image forming unit 20, a storage unit 40, an image reading unit 50, and a fixing unit 80. The image reading unit 50 reads an image from the original and generates an image data ID which is digital data.

The image forming unit 20 includes a color conversion processing unit 21, a halftone processing unit 22, a density sensor 28 for calibration, an exposure unit 29, and a photoconductor drum (image carrier) 30c to 30k which is an amorphous silicon photoconductor. It has a developing unit 100c to 100k and a charging unit 25c to 25k. The color conversion processing unit 21 color-converts the color space of the image data ID, which is RGB data, into CMYK data having a color space that can be reproduced by the development units 100c to 100k. The halftone processing unit 22 executes halftone processing on the CMYK data to generate print data PD as CMYK halftone data. The halftone data represents the formation state of dots formed by each CMYK toner, and is also called dot data.

The control unit 10 includes main storage means such as RAM and ROM, and control means such as MPU (Micro Processing Unit) and CPU (Central Processing Unit). Further, the control unit 10 has controller functions related to interfaces such as various I / O, USB (universal serial bus), bus, and other hardware, and controls the entire image forming apparatus 1. The control unit 10 includes an end detection unit 11 and an image processing unit 12.

The end portion detecting unit 11 detects the rear end pixel of the end portion (edge pixel) of the image area. The end detection unit 11 may detect the rear end pixel based on the relationship between the pixel values of the pixel of interest and the adjacent pixel, or detect the rear end pixel using a filter such as a differential filter or a Sobel filter. You may. The rear-end pixel is defined as the rear-end pixel on the rear-end side with reference to the peripheral speed direction of the photoconductor drum (described later). The function of the image processing unit 12 will be described later.

The storage unit 40 is a storage device including a hard disk drive, a flash memory, or the like which is a non-temporary recording medium, and stores control programs and data of processes executed by the control unit 10. In the present embodiment, the storage unit 40 further stores the calibration data CD1 and the correction data CD2. The calibration data CD1 and the correction data CD2 can be configured as, for example, a LUT (Look Up Table). The contents of the calibration data CD1 and the correction data CD2 will be described later.

FIG. 2 is a cross-sectional view showing the overall configuration of the image forming apparatus 1 according to the embodiment. The image forming apparatus 1 of the present embodiment is a tandem type color printer. The image forming apparatus 1 has photoconductor drums (image carriers) 30m, 30c, 30y, and 30k arranged in a row in a housing 70 corresponding to magenta, cyan, yellow, and black colors. Development units 100m, 100c, 100y and 100k are arranged adjacent to the photoconductor drums 30m, 30c, 30y and 30k, respectively.

The photoconductor drums 30m, 30c, 30y and 30k are irradiated (exposed) with laser beams Lm, Lc, Ly and Lk for each color from the exposure unit 29. By this irradiation, electrostatic latent images are formed on the photoconductor drums 30m, 30c, 30y and 30k. The developing units 100m, 100c, 100y and 100k adhere the toner to the electrostatic latent images formed on the surfaces of the photoconductor drums 30m, 30c, 30y and 30k while stirring the toner. As a result, the developing process is completed, and toner images of each color are formed on the surfaces of the photoconductor drums 30c to 30k.

The image forming apparatus 1 has an endless intermediate transfer belt 27. The intermediate transfer belt 27 is stretched on the tension roller 24, the drive roller 26a, and the driven roller 26b. The intermediate transfer belt 27 is circulated and driven by the rotation of the drive roller 26a.

For example, the black toner image on the photoconductor drum 30k is primarily transferred to the intermediate transfer belt 27 by sandwiching the intermediate transfer belt 27 between the photoconductor drum 30k and the primary transfer roller 23k and driving the intermediate transfer belt 27 to circulate. Toner. This point is the same for the three colors of cyan, yellow, and magenta.

A full-color toner image is formed on the surface of the intermediate transfer belt 27 by performing primary transfer so that the intermediate transfer belts 27 are superposed on each other at predetermined timings. The calibration density sensor 28 is arranged at a position where the density of the toner image before the primary transfer is completed and the density of the toner image before the secondary transfer can be measured. The full-color toner image is then secondarily transferred to the printing paper P supplied from the paper feed cassette 60, and fixed to the printing paper P as the printing medium by the fixing roller pair 81 of the fixing unit 80.

FIG. 3 is a side sectional view showing the structure of the developing unit 100 according to the embodiment of the present invention. The developing units 100m, 100c, 100y and 100k have the same configuration, and these are also simply referred to as the developing unit 100. The developing unit 100 includes two stirring and transporting members 141 and 142, a magnetic roller 143, a developing roller (developer carrier) 144, a developing container 145, and a regulating blade 146.

The developing container 145 constitutes the outer shell of the developing unit 100. A partition portion 145b is provided at the lower part of the developing container 145. The partition portion 145b partitions the inside of the developing container 145 into a first transport chamber 145a and a second transport chamber 145c. The first transport chamber 145a and the second transport chamber 145c extend in a columnar direction in the direction perpendicular to FIG. 3, and accommodate a two-component developer (also simply referred to as a developer) composed of a magnetic carrier and black toner.

The developing container 145 further holds a magnetic roller 143 and a developing roller 144. The developing container 145 is formed with an opening 147 that exposes the developing roller 144 toward the photoconductor drum 30 (30k).

The two stirring and transporting members 141 and 142 are cyclically moved while stirring the developer inside the first transport chamber 145a and the second transport chamber 145c, respectively. The stirring and transporting member 142 supplies a positively charged developer to the magnetic roller 143 as a magnetic brush. The magnetic roller 143 has a non-magnetic rotating sleeve 143a and a fixed magnet body 143b fixed inside the rotating sleeve 143a. The magnetic roller 143 and the developing roller 144 face each other with a predetermined clearance. The regulation blade 146 adjusts the magnetic brush to a preset predetermined height.

The developing roller 144 has a rotatable non-magnetic developing sleeve 144a and a developing roller side magnetic pole 144b fixed inside the developing sleeve 144a. A magnetic roller potential Vmag is applied to the magnetic roller 143. A development bias potential Vslv is applied to the developing roller 144.

In the present embodiment, the surface potential of the photoconductor drum 30 is set to 20 V, and a developing electric field is formed between the photoconductor drum 30 and the developing roller 144. On the other hand, an alternating bias in which a DC potential of 20 to 80 V as a development bias potential Vslv and a sinusoidal potential having a peak-to-peak value of 2000 V at a frequency of 2 kHz are superimposed is applied to the developing roller 144. A direct current potential of 200 V is applied to the magnetic roller 143 as the magnetic roller potential Vmag during development, and a direct current potential of −200 V is applied to the magnetic roller 143 during non-development.

As a result, at the time of development, the time of the development bias potential Vslv <magnetic roller potential Vmag (potential state in which the toner is supplied to the development roller 144) becomes longer, and the time for the toner to be supplied to the development roller 144 becomes longer. During non-development, the development bias potential Vslv> magnetic roller potential Vmag (potential state in which the toner is recovered from the developing roller 144) becomes longer, and the time for the toner to be recovered from the developing roller 144 becomes longer.

Further, by adjusting the magnetic roller potential Vmag applied to the magnetic roller 143 during development and non-development, the toner layer formation potential difference ΔV between the development bias potential Vslv and the magnetic roller potential Vmag during development is changed. Can be done. As a result, the developing roller 144 has a thin toner layer (simply toner) having a thickness D (see FIG. 4A described later) corresponding to the toner layer forming potential difference ΔV between the developing bias potential Vslv and the magnetic roller potential Vmag. Also called a layer.) Is formed.

The developing roller 144 attaches toner to the photoconductor drum 30 via an opposing portion (development nip) having a predetermined clearance with the photoconductor drum 30, and forms a toner image on the surface of the photoconductor drum 30. .. The toner image is formed based on the potential difference between the potential of the electrostatic latent image on the surface of the photoconductor drum 30 and the potential difference of the development bias potential Vslv applied to the developing roller 144.

Amorphous silicon photoconductors have a relative permittivity about three times higher than that of organic photoconductors (OPC), and have a feature that the amount of toner that the photoconductor can hold is large with respect to the development contrast potential. Therefore, the amorphous silicon photoconductor can retain more toner than the solid concentration normally used. Therefore, when the amorphous silicon photoconductor is used in a saturated state, it retains an amount exceeding the amount required for the solid concentration. Therefore, in the present embodiment, the amorphous silicon photoconductor is used in a non-saturated state even at a solid density, and almost all the toner formed on the developing roller 144 is developed into the photoconductor and the development is completed to complete the solid density. Is used to determine.

FIG. 4 is a conceptual diagram showing how a rear end pool is generated in the developing process according to the embodiment. FIG. 4A shows how an image is formed at the tip and center of the image. FIG. 4B shows how the image is formed at the rear end of the image. In the present specification, the front end portion, the central portion, and the rear end portion are defined as the front end portion, the central portion, and the rear end portion in order from the traveling direction with reference to the traveling direction of the photoconductor drum 30.

In the present embodiment, as shown in FIG. 4A, the photoconductor drum 30 receives toner from the developing sleeve 144a of the developing roller 144 while neutralizing the potential of the latent image image. At this time, the developing step is configured to be completed not by the saturation of the potential but by the exhaustion of the toner thin layer formed on the developing sleeve 144a in the non-saturated state. The thickness D of the toner thin layer is set to have a thickness T1 for achieving the maximum density at the time of solid development in image formation.

In the present embodiment, as shown in FIG. 4B, the developing sleeve 144a has a peripheral speed Vs1 (full speed mode: 266.7 mm / s) or a peripheral speed Vs2 (half speed mode: 133.3 mm / s). It has a peripheral speed. On the other hand, the photoconductor drum 30 has a peripheral speed of peripheral speed Vd1 (full speed mode) or peripheral speed Vd2 (half speed mode) in the same direction. The peripheral speed Vs1 and the peripheral speed Vs2 of the developing sleeve 144a are set to 1.6 times the peripheral speed Vd1 and the peripheral speed Vd2 of the photoconductor drum 30, respectively. The half-speed mode is an operation mode used to double the image forming process time, for example, when the print medium is thick paper or the like.

In this way, the developing sleeve 144a is configured to form an image while overtaking the photoconductor drum 30. Therefore, at the time of solid development, the surface of the developing sleeve 144a in which toner is not consumed exists in the vicinity of the solid rear end pixel. The surface on which the toner is not consumed overtakes the vicinity of the rear end pixel of the solid latent image in the amorphous silicon photoconductor 30.

At this time, since the photoconductor drum 30 as the amorphous silicon photoconductor is in an unsaturated state, the toner is further developed from the surface of the developing sleeve 144a in which the toner is not consumed. By this development, the rear end pool (thickness T2) as a solid density higher than the density assumed in advance becomes apparent.

FIG. 4C shows a density curve D1 when the peripheral speed of the developing sleeve 144a is peripheral speed Vs1 (full speed mode) and a density curve D2 when the peripheral speed of the developing sleeve 144a is peripheral speed Vs2 (half speed mode). It shows that. The two density curves D1 and D2 are curves that can be generated, for example, by reading a patch formed on a print medium with a resolution of 600 dpi by the image reading unit 50.

According to the experiment of the inventor of the present application, for example, in the case of 600 dpi, the rear end pool is generated in the range of about 25 pixels in the full speed mode, whereas in the half speed mode, it is in the range of about 35 pixels. It was found that the rear end pool was generated. The reason for this is that the range of overdevelopment due to the unsaturated state of the photoconductor drum 30 has expanded due to the lengthening of the developing process time due to the decrease in the peripheral speed of the developing sleeve 144a and the photoconductor drum 30. Guessed.

Further, in the image forming apparatus 1 according to the experiment of the inventor of the present application, the width of the rear end pixel group, which is the rear end pixel group in which the rear end pool is generated, is remarkable even if the set value of the dot area ratio changes. On the other hand, it was found that the density of the rear end pixel group in which the rear end accumulation occurs changes relatively remarkably according to the change of the set value of the dot area ratio. That is, the inventor of the present application shows that the density of the rear end pixel group changes relatively remarkably according to the change of the dot area ratio, and the width of the rear end pixel group changes according to the change of the peripheral speed of the developing sleeve 144a. We found that it changed relatively significantly. The setting value of the dot area ratio will be described later.

FIG. 5 is a flowchart showing the contents of the half patch calibration processing procedure (step S100) of the image forming apparatus 1 according to the embodiment. In the present embodiment, since the amorphous silicon photoconductor is used for the photoconductor drums 30c to 30k, the image forming apparatus 1 is configured so as to express solidness with a half patch in order to suppress the problem of rear end accumulation. There is.

Such a problem of rear end accumulation can be suppressed by expressing solid with a half patch. In this example, the image forming apparatus 1 is assumed to express a solid image with a half patch having a dot area ratio of 70% to 90%. In the present embodiment, the solid density by the half patch is calibrated by adjusting the development bias potential Vslv and the dot area ratio, which are the applied potentials of the developing units 100m, 100c, 100y and 100k.

In step S110, the control unit 10 functions as a calibration unit and forms a chart having a plurality of half patches in which the development bias potential Vslv is changed stepwise on the intermediate transfer belt 27. Specifically, the control unit 10 forms a chart having a plurality of half patches having different development bias potentials Vslv at the dot area ratio (70% in this example) as the initial value before calibration on the intermediate transfer belt 27. .. The plurality of half patches include those having the maximum development bias potential Vslv.

The reason for using a plurality of half patches in which the development bias potential Vslv is changed stepwise is that the toner image is the potential of the electrostatic latent image on the surface of the photoconductor drum 30 and the development bias potential Vslv applied to the development roller 144. This is because it is formed based on the potential difference. Multiple half patches are formed for each of the CMYKs. In the following, a cyan (C) half patch will be described as an example.

In step S120, the control unit 10 measures the patch density of each color (for example, cyan (C)) using the calibration density sensor 28. For the density of the patch, for example, the amount of reflected light of red, which has a complementary color of cyan (C), can be measured. The same processing is performed for MYK.

In the present embodiment, the calibration density sensor 28 emits infrared light from, for example, an LED (not shown), transmits a polarizing filter that transmits only P waves, and irradiates the patch with P waves of infrared light. , The density is detected based on the ratio of the P wave and the S wave of the reflected light detected by the light receiving element. The calibration density sensor 28 also includes a specular reflection method for detecting the regular reflection light from the patch and a diffuse reflection method for detecting the diffuse reflection light from the patch.

In step S130, the control unit 10 executes the development bias adjustment process. In the development bias adjustment process, the control unit 10 has a patch that has reached a preset solid image target density from among a plurality of cyan (C) half patches in which the development bias potential Vslv is changed stepwise. If present, it is performed by selecting the development bias potential Vslv corresponding to the patch. Specifically, when there is a half patch in which the ratio of the P wave and the S wave is equal to or less than the preset threshold value, the control unit 10 calibrates the lowest development bias potential Vslv in the half patch. Adjust to the development bias potential of.

In step S140, if the half patch calibration is possible within the development bias adjustment range, the control unit 10 proceeds to step S195, and the half patch calibration is possible within the development bias potential Vslv adjustment range. If not, the process proceeds to step S150. In step S195, the control unit 10 stores the developed development bias potential Vslv after calibration in the storage unit 40 as a part of the calibration data CD1. Calibration by adjusting the development bias potential Vslv is also called a first calibration process.

If half-patch calibration is not possible within the development bias adjustment range, it means that none of the multiple cyan (C) patches has reached the preset solid image target density. ing. Normally, one of the plurality of half patches reaches the solid image target density, but the solid image target density may not be reached when the toner charge amount is increasing due to, for example, environmental changes. However, if the half patch calibration is not possible within the development bias adjustment range, the problem of rear end accumulation as shown in FIG. 4 will occur.

In step S150, the control unit 10 sets the development bias potential Vslv to the maximum value, adjusts the dot area ratio, and starts the operation mode for calibration. The maximum value of the development bias potential Vslv is also called a potential limit value, and is set from the viewpoint of, for example, the output limit of the development bias and the adverse effect on the image (fog, etc.).

In step S160, the control unit 10 forms a chart having a plurality of half patches whose dot area ratio is changed stepwise on the intermediate transfer belt 27. In this example, the dot area ratio is changed stepwise in the range of the dot area ratio of 71% to 90%.

In step S170, the control unit 10 measures the concentration of the cyan (C) patch using the calibration concentration sensor 28. The calibration density sensor 28 measures the ratio of the P wave and the S wave. The same processing is performed for MYK.

In step S180, the control unit 10 sets the dot area ratio. Specifically, when the control unit 10 has a half patch having a ratio of P wave and S wave equal to or lower than a preset threshold value, the control unit 10 has a half patch having the lowest dot area ratio among the half patches. Acquire the dot area ratio as calibration data. Calibration by setting the dot area ratio is also called a second calibration process. The control unit 10 stores the dot area ratio after calibration in the storage unit 40 as a part of the calibration data CD1.

In step S190, the image processing unit 12 of the control unit 10 executes the correction amount determination process. In the correction amount determination process, the image processing unit 12 determines the correction amount based on the dot area ratio set in step S180. In the present embodiment, the correction amount is set so as to reduce a change in the amount of toner adhering to the rear end pixel group according to the dot area ratio.

Specifically, in the image processing unit 12, for example, the dot area ratio is 90%, and the toner adhesion amount of the rear end pixel group estimated based on the dot area ratio of 90% is the adhesion amount of other regions. The correction amount can be determined so as to thin out 10% when the value reaches 1.2 times. The image processing unit 12 stores the correction amount for each dot area ratio after proofreading in the storage unit 40 as a part of the correction data CD2.

FIG. 6 is a flowchart showing the contents of the image forming process (step S200) in the image forming apparatus 1 according to the embodiment. In step S210, the control unit 10 executes the dot data generation process. In the dot data generation process, the control unit 10 uses a color conversion process or a halftone process to generate dot data (print data PD) representing a dot formation state.

In step S220, the image processing unit 12 of the control unit 10 determines whether or not the dot area ratio is set in the second calibration process. The image processing unit 12 advances the process to step S230 when the dot area ratio is set, and proceeds to step S270 when the dot area ratio is not set. This is because when the dot area ratio is not set in the second calibration process, the problem of rear end accumulation as shown in FIG. 4 is sufficiently suppressed.

In step S230, the control unit 10 determines whether or not the operation mode of the photoconductor drum 30 is the full speed mode. The control unit 10 advances the process to step S240 when it is in the full speed mode, and advances the process to step S250 when it is in the half speed mode.

In step S240, the control unit 10 sets the rear end width for full speed. In this example, the control unit 10 sets the width of the rear end pixel group for full speed within 25 pixels in the sub-scanning direction in the image from the rear end pixel to be corrected. On the other hand, in step S250, the control unit 10 sets the rear end width for full speed. In this example, the control unit 10 sets the width of the rear end pixel group for half speed within 35 pixels in the sub-scanning direction in the image from the rear end pixel to be corrected.

In step S260, the image processing unit 12 of the control unit 10 executes the rear end width data correction process. In the rear end width data correction process, the image processing unit 12 reads out the correction amount of the correction data CD2 stored in the storage unit 40 according to the dot area ratio, and the dot data of the rear end pixel group to be corrected. To adjust the dot formation state (for example, thinning out dots or changing the size). The rear end pixel group is specified by the end detection unit 11 of the control unit 10 using the rear end width.

In this example, the width of the rear end pixel group is adjusted according to the operation mode of the photoconductor drum 30, while the correction amount is common. In the image forming apparatus 1 according to the present embodiment, the width of the rear end pixel group, which is the rear end pixel group in which the rear end pool is generated, does not change remarkably even if the dot area ratio changes, while the rear end This is because it was found that the density of the rear end pixel group in which the accumulation occurs changes according to the change in the dot area ratio.

In step S270, the halftone processing unit 22 of the image forming unit 20 executes halftone processing on the corrected CMYK data to generate print data PD as CMYK halftone data.

As described above, the image forming apparatus 1 according to the embodiment switches the width of the rear end pixel group between the rear end width for full speed and the rear end width for half speed according to the operation mode of the photoconductor drum 30. The gradation value of the rear end width can be corrected. As a result, the image forming apparatus 1 can appropriately reduce the edge effect according to the rotation speed of the photoconductor in the electrograph developed with the photoconductor in the unsaturated state.

The present invention can be implemented not only in the above embodiment but also in the following modifications.

Modification 1: In the above embodiment, the rear end accumulation is suppressed by correcting the gradation value of the rear end pixel group, but the exposure is not limited to the correction of the gradation value of the rear end pixel group. Specifically, by adjusting the amount of exposure light due to the above, the control unit may adjust the amount of exposure light to the rear end pixel group to reduce the amount of toner adhering.

Modification 2: In the above embodiment, the image processing unit reduces the amount of toner adhering to the pixel group constituting the rear end width based on the dot area ratio set in the second calibration process, for example. The calibration density sensor measures the amount of toner adhered to the rear end width and the width of the rear end pixel group, and adjusts the amount of toner adhesion corrected and the width of the rear end pixel group based on this measured value. You may do so.

Modification 3: In the above embodiment, an amorphous silicon photoconductor is used, but the present invention is not limited to the use of an amorphous silicon photoconductor. The present invention can generally be applied to an image forming apparatus that reproduces a solid density with a photoconductor in an unsaturated state.

1 Image forming device 10 Control unit 11 End detection unit 12 Image processing unit 20 Image forming unit 21 Color conversion processing unit 28 Calibration density sensor 29 Exposure unit 40 Storage unit 50 Image reading unit 60 Paper feed cassette 70 Housing

Claims (7)

A photoconductor that can rotate at a plurality of peripheral speeds and forms a solid image in an unsaturated state, an exposure unit that exposes the photoconductor to form an electrostatic latent image based on image data, a magnetic roller, and development. The developing roller has a roller, and a toner layer having a thickness corresponding to the toner layer forming potential difference between the magnetic roller and the developing roller is formed on the developing roller, and the developing bias potential which is the potential of the developing roller and the static. A developing unit that attaches toner from the toner layer to the photoconductor based on an electro-latent image.
The solid when the adjusted within the adjustment range of the developing bias potential is set in advance of the developing unit to perform a first calibration process, it became potential limit value within the adjustment range in the first calibration process A proofreading unit that sets the dot area ratio for forming an image and executes a second proofreading process.
When the second calibration process is executed, a rear end pixel group forming a range to be corrected from the rear end pixels of the peripheral speed is selected according to the selection of any one of the plurality of peripheral speeds. Image processing that specifies regardless of the dot area ratio and determines a common correction amount for the plurality of peripheral speeds for reducing the amount of toner adhering to the rear end pixel group according to the dot area ratio. Department and
An image forming apparatus comprising. The image forming apparatus according to claim 1.
The image processing unit is an image forming apparatus that corrects dot data representing a dot formation state in the rear end pixel group to reduce the amount of toner adhering to the rear end pixel group. The image forming apparatus according to claim 1 or 2.
The image processing unit is an image forming apparatus that adjusts the amount of light of the exposure to the rear end pixel group to reduce the amount of toner adhering to the rear end pixel group. The image forming apparatus according to any one of claims 1 to 3.
The image processing unit is an image forming apparatus that determines a correction amount of a toner adhesion amount to the rear end pixel group based on the adjusted dot area ratio. The image forming apparatus according to any one of claims 1 to 4.
The photoconductor is an amorphous silicon photoconductor, and the photoconductor is an amorphous silicon photoconductor.
The amorphous silicon photoconductor is an image forming apparatus that forms the solid image in an unsaturated state. A photoconductor that can rotate at a plurality of peripheral speeds and forms a solid image in an unsaturated state, an exposure unit that exposes the photoconductor to form an electrostatic latent image based on image data, a magnetic roller, and development. Using a roller, a toner layer having a thickness corresponding to the toner layer forming potential difference between the magnetic roller and the developing roller is formed on the developing roller, and the developing bias potential and the electrostatic are the potentials of the developing roller. A developing step of adhering toner from the toner layer to the photoconductor based on a latent image,
The solid when the adjusted within the adjustment range of the developing bias potential is set in advance of the development process executes the first calibration process, became potential limit value within the adjustment range in the first calibration process A proofreading process in which the dot area ratio for forming an image is set and a second proofreading process is executed, and
When the second calibration process is executed, a rear end pixel group forming a range to be corrected from the rear end pixels of the peripheral speed is selected according to the selection of any of the plurality of peripheral speeds. Image processing that specifies regardless of the dot area ratio and determines a common correction amount for the plurality of peripheral speeds for reducing the amount of toner adhering to the rear end pixel group according to the dot area ratio. Process and
An image forming method comprising. An image forming program for controlling an image forming apparatus that forms an image on an image forming medium according to image data.
The image forming apparatus includes a photoconductor that can rotate at a plurality of peripheral speeds and forms a solid image in an unsaturated state, and an exposure unit that exposes the photoconductor to form an electrostatic latent image based on image data. A magnetic roller and a developing roller are provided, and a toner layer having a thickness corresponding to a toner layer forming potential difference between the magnetic roller and the developing roller is formed on the developing roller, which is the potential of the developing roller. A developing unit for adhering toner from the toner layer to the photoconductor based on the development bias potential and the electrostatic latent image is provided.
The solid when the adjusted within the adjustment range of the developing bias potential is set in advance of the developing unit to perform a first calibration process, it became potential limit value within the adjustment range in the first calibration process The calibration unit that sets the dot area ratio for forming an image and executes the second calibration process, and when the second calibration process is executed, selects one of the plurality of peripheral speeds. Correspondingly, the rear end pixel group constituting the range to be corrected from the rear end pixel of the peripheral speed is specified regardless of the dot area ratio, and the rear end pixel group is assigned according to the dot area ratio. An image forming program that causes the image forming apparatus to function as an image processing unit that determines a common correction amount for the plurality of peripheral speeds for reducing the amount of toner adhering.

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