JP2017105005A - Image forming device, image processing device and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device that can suppress unnecessary radiation noise and reduce consumption amounts of developer.SOLUTION: The image forming device comprises: identifying means that identifies pixels to be corrected, on the basis of image data; correcting means that corrects exposure amounts by exposing means relative to the pixels to be corrected, from exposure amounts that the image data indicates; determining means that determines sub pixels to be exposed and sub pixels not to be exposed, with respect to the pixels respectively, on the basis of the exposure amounts of the corrected pixels; and memorizing means that memorizes exposure patterns for a predetermined number of continuous pixels of the same exposure amounts, with respect to the exposure amounts respectively. The determining means, when the pixels with the same exposure amounts continue in a predetermined number or more, determines the sub pixels to be exposed and the sub pixels not to be exposed by using the exposure patterns memorized by the memorizing means, with respect to the pixels continuing in the predetermined number or more, where intervals of the sub pixels not to be exposed are not made constant in the exposure patterns memorized by the memorizing means.SELECTED DRAWING: Figure 10

Description

  The present invention relates to a technique for reducing developer consumption and preventing unwanted radiation in an image forming apparatus.

  In an image forming apparatus, it is required to maintain the quality of an image to be formed and reduce the consumption of toner as a developer. Patent Document 1 discloses a configuration in which an exposure time is shortened by pulse width modulation in order to suppress image quality deterioration due to sweeping. Patent Document 2 discloses a configuration for adjusting the exposure amount in order to suppress image quality deterioration due to the edge effect.

JP 2003-345076 A JP 2000-343748 A

  In recent years, there has been an increasing demand for image forming apparatuses to reduce developer consumption. In addition, image forming apparatuses are also required to suppress unnecessary radiation noise (radiated electromagnetic waves).

  The present invention provides an image forming apparatus, an image processing apparatus, and a program capable of suppressing unnecessary radiation noise and reducing the consumption of developer.

  According to one aspect of the present invention, an image forming apparatus includes a photosensitive member, an exposure unit that exposes the photosensitive member to form an electrostatic latent image, and develops the electrostatic latent image of the photosensitive member with a developer. A developing unit that forms an image, a specifying unit that specifies a correction target pixel from pixels of an image formed from the image data, and an exposure amount by the exposure unit for the correction target pixel, Correction means for correcting from the exposure amount indicated by the image data, determination means for determining a subpixel to be exposed and a subpixel not to be exposed for each pixel based on the exposure amount of each pixel after correction by the correction means, and each exposure Storage means for storing an exposure pattern for a predetermined number of consecutive pixels having the same exposure amount with respect to the amount, and the determining means is configured to store the predetermined number when pixels having the same exposure amount continue for the predetermined number or more. that's all For the subsequent pixels, the exposure pattern stored in the storage unit is used to determine the subpixel to be exposed and the subpixel not to be exposed for each of the predetermined number of pixels. In the exposure pattern stored in the storage unit, exposure is performed. The interval between the sub-pixels not to be performed is not constant.

  According to the present invention, unnecessary radiation noise can be suppressed and developer consumption can be reduced.

1 is a configuration diagram of an image forming apparatus according to an embodiment. Explanatory drawing of the image development system by one Embodiment. The figure which shows the image which the edge effect and sweeping produced. The figure which shows the control structure of the exposure amount by one Embodiment. The functional block diagram of CPU for controlling the exposure amount by one Embodiment. The flowchart of the correction process by one Embodiment. The figure which shows the correction width | variety parameter and exposure amount adjustment parameter by one Embodiment. The figure which shows the pixel value of the image by one Embodiment, and the correction object pixel of this image. The figure which shows the exposure pattern of 1 pixel by one Embodiment. The figure which shows the exposure pattern of 5 pixels by one Embodiment. The figure which shows the unnecessary radiation noise by one Embodiment. The figure which shows the correction width | variety parameter and exposure amount adjustment parameter by one Embodiment. The figure which shows the exposure pattern of 2 pixels by one Embodiment. The figure which shows the exposure pattern of 10 pixels and 6 pixels by one Embodiment.

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. In addition, the following embodiment is an illustration and does not limit this invention to the content of embodiment. In the following drawings, components that are not necessary for the description of the embodiments are omitted from the drawings.

<First embodiment>
FIG. 1 is a configuration diagram of an image forming apparatus 101 according to the present embodiment. The photosensitive member 1 serving as an image carrier is rotationally driven in the direction of the arrow in the figure during image formation. The charging unit 2 charges the surface of the photoreceptor 1 to a uniform potential. The exposure unit 7 exposes the surface of the charged photoconductor 1 with light based on image data to form an electrostatic latent image on the photoconductor 1. The exposure unit 7 is driven by a drive signal 71 output from the image calculation unit 9. The exposure control unit 19 of the image calculation unit 9 adjusts the exposure intensity by the exposure unit 7 to a target value by the voltage Va.

  The developing unit 3 includes a container 13 for storing toner as a developer, and a developing roller 14. The toner may be a non-magnetic one-component toner, a two-component toner, or a magnetic toner. The regulating blade 15 is provided to regulate the layer thickness of the toner supplied to the developing roller 14 to a predetermined value. The regulating blade 15 can also be configured to impart charge to the toner. The toner is conveyed to the developing area 16 by the developing roller 14. The developing area 16 is an area where the developing roller 14 and the photoreceptor 1 are close to or in contact with each other, and is an area where toner is attached to the electrostatic latent image. The developing unit 3 attaches toner to the electrostatic latent image formed on the photoreceptor 1 and visualizes it as a toner image. The transfer unit 4 transfers the toner image formed on the photoreceptor 1 to the recording material P. The fixing unit 6 applies heat and pressure to the recording material P to fix the toner image transferred to the recording material P to the recording material P.

  The CPU 10 of the image calculation unit 9 is a control unit that comprehensively controls the entire image forming apparatus 101. In addition, not only the structure which performs all the control demonstrated below by CPU10 but it can be set as the structure which ASIC18 performs a part of it. Further, the ASIC 18 may perform all of the control described below. The memory 11 is a storage unit that stores image data 111 and holds an LUT 112 and exposure pattern data 113. The LUT 112 is a look-up table and includes a correction width parameter and an exposure amount adjustment parameter which will be described later. The detection unit 12 detects status information indicating the status of the image forming apparatus 101 and notifies the CPU 10 of the status information. The state information includes, for example, environment information or use state information, or both of them. The environmental information is information indicating the environment of the image forming apparatus such as environmental temperature and environmental humidity. The use state information is information indicating the degree of deterioration due to the use of the image forming apparatus 101, such as the number of formed images, the cumulative operating time of the image forming apparatus 101, the surface resistance value of the photosensitive member 1, and the like. The image calculation unit 9 receives image data transmitted from the host computer 8, suppresses the effects of edge effects and sweeping based on the correction width parameter and the exposure amount adjustment parameter held by the LUT 112, and reduces toner consumption. As described above, the image data is corrected.

  Next, the developing method in the developing unit 3 will be described with reference to FIGS. 2 (A) and 2 (B). FIG. 2A shows a configuration in the jumping development system. In the jumping development method, the developing roller 14 and the photoreceptor 1 are not brought into contact with each other, and a gap 17 having a predetermined distance is provided. An AC bias offset by a DC bias is used as the developing bias output from the developing roller 14. FIG. 2B shows a configuration in the contact development method. In the contact development method, the developing roller 14 and the photoreceptor 1 are brought into contact with each other. A DC bias is used as the developing bias output from the developing roller 14. In the contact development method, for example, the rotation directions of the photosensitive member 1 and the developing roller 14 are opposite to each other as shown in FIG. 2B, that is, in the developing region 16, the respective surfaces move in the same direction. Configure as follows.

  Next, the edge effect and sweeping in which the amount of toner attached to the electrostatic latent image increases at the edge portion will be described. The edge effect is an electrostatic latent image formed on the photosensitive member 1, that is, an electric field concentrates on the boundary between the exposure area and the other non-exposure area, so that excessive toner is present at the edge of the electrostatic latent image. It is a phenomenon that adheres to. FIG. 3A shows a toner image 400 in which an edge effect has occurred. An arrow A in FIG. 3A indicates the toner image conveyance direction, that is, the rotation direction of the photosensitive member 1. It should be noted that the image data from which the toner image 400 is based has the same value for all pixels, that is, the toner image 400 is an image having a uniform density. When the edge effect occurs, the toner concentrates and adheres to the edge region 402a of the toner image 400. As a result, the density of the edge region 402a is higher than the density of the non-edge region 401a. The edge effect mainly occurs in the jumping development method in which there is a gap between the photoreceptor 1 and the developing roller 14.

  On the other hand, sweeping is a phenomenon in which toner concentrates on the rear end of the photoreceptor image 1 in the rotation direction of the toner image. FIG. 3B shows the toner image 410 in which sweeping has occurred. An arrow A in FIG. 3B indicates the toner image conveyance direction, that is, the rotation direction of the photoreceptor 1. Note that the image data that is the basis of the toner image 410 has the same value for all pixels, that is, the toner image 410 is an image having a uniform density. When sweeping occurs, toner concentrates and adheres to the rear end region 402b of the toner image 410. As a result, the density of the rear end area 402b is higher than the density of the other areas 401b.

  FIG. 4 shows a control configuration of the exposure unit 7. The exposure control unit 19 includes an IC 2003 including an 8-bit DA converter (DAC) 2021 and a regulator (REG) 2022. The IC 2003 adjusts the voltage VrefH output from the regulator 2022 based on the intensity adjustment signal 73 set by the CPU 10. The voltage VrefH is a reference voltage for the DA converter 2021. When the IC 2003 sets the input data 2020 of the DA converter 2021, the DA converter 2021 outputs the voltage Va to the exposure unit 7. The VI conversion circuit 2306 of the exposure unit 7 converts the voltage Va into a current value Id and outputs it to the driver IC 2009. The driver IC 2009 controls the exposure intensity of the exposure unit 7 based on the current value Id. That is, the exposure control unit 19 can control the exposure intensity of the exposure unit 7 by the voltage Va. The driver IC 2009 switches the switch (SW) of the driver IC 2009 in accordance with the drive signal 71 output from the image calculation unit 9. SW performs ON / OFF control of light emission of the LD by switching whether the current IL is supplied to the laser diode (LD) of the exposure unit 7 or to the dummy resistor R1.

  FIG. 5 shows a functional block of the CPU 10 that adjusts the exposure amount to suppress the edge effect. In the present embodiment, the CPU 10 adjusts the exposure amount. However, as described above, the CPU 10 may be configured with the ASIC 18 or may be configured with the ASIC 18 alone. The state detection unit 610 receives the state information detected by the detection unit 12 and outputs it to the parameter setting unit 602. Based on the state information, the parameter setting unit 602 notifies / sets the correction width parameter corresponding to the received state information among the correction width parameters of the LUT 112 to the image analysis unit 601. Also, the parameter setting unit 602 notifies / sets the exposure amount adjustment parameter corresponding to the received state information among the exposure amount adjustment parameters of the LUT 112 to the exposure amount adjustment unit 603. The image data 604 transmitted from the host computer 8 is stored in the memory 11. The image analysis unit 601 identifies pixels that can cause an edge effect from the pixels of the image formed by the image data 604 based on the correction width parameter, and notifies the exposure amount adjustment unit 603 of the identified pixels. Here, the image means a continuous pixel region to which the toner adheres, and the image analysis unit 601 specifies pixels that can cause an edge effect in the region from the edge of the region to which the toner adheres. . The exposure amount adjustment unit 603 corrects the pixel value of the pixel specified by the image analysis unit 601 based on the exposure amount adjustment parameter, and generates corrected image data. Further, the exposure amount adjustment unit 603 determines an exposure pattern based on the corrected exposure amount of each pixel, that is, the corrected pixel value, generates a PWM signal as the drive signal 71, and performs exposure using the PWM signal. The unit 7 is driven. The determination of the exposure pattern will be described later. The correction width parameter indicates the range of pixels in which the edge effect can occur in terms of the number of pixels from the edge pixels. For example, if the correction width parameter is “3”, it is determined that an edge effect occurs in three pixels on the edge side of the region to which the toner adheres. The exposure adjustment parameter indicates the correction amount of the exposure amount of the correction target pixel. For example, in the present embodiment, the exposure reduction ratio is shown, but any other value can be used.

  FIG. 6 is a flowchart of an image forming process based on received image data. In step S10, the state detection unit 610 receives the state information detected by the detection unit 12. In step S11, the state detection unit 610 determines whether exposure amount adjustment is necessary based on the state information and the LUT 112. FIG. 7 shows an example of the LUT 112. Conditions 1 to 4 in FIG. 7 evaluate the use state of the image forming apparatus 101 in four stages. In this example, it is assumed that the degree of deterioration of the image forming apparatus 101 progresses in the order of conditions 1 to 4. For example, when the cumulative image forming number is used as the status information, for example, if the cumulative image forming number is 0 to 1000, Condition 1 is used, and if the cumulative image forming number is 1001 to 2000, Condition 2 is used. . Furthermore, Condition 3 is used when the cumulative image formation number is from 2001 to 3000, and Condition 4 is used when the cumulative image formation number is 3001 or more. Here, “−” in condition 4 in FIG. 7 indicates that the exposure amount is not corrected. Therefore, if the cumulative number of image formation sheets acquired as the status information in S10 is 3001 or more, the status detection unit 610 determines in S11 that it is not necessary to adjust the exposure amount. In this case, the CPU 10 forms an image based on the image data in S17. On the other hand, if the cumulative image forming number acquired as the status information in S10 is 3000 or less, the status detection unit 610 determines in S11 that the exposure amount needs to be adjusted.

  If the exposure amount needs to be adjusted, the parameter setting unit 602 determines the one to be used from the correction width parameter and the exposure amount adjustment parameter indicated in the LUT 112 based on the state information in S12, and sets each of them to the image analysis unit 601. Notification / setting to the exposure amount adjustment unit 603. For example, when the state information acquired in S10 matches the condition 3, the parameter setting unit 602 indicates that the correction width parameter is “3”, that is, the third pixel from the edge of the image is the correction target pixel. Notify that there is. Furthermore, in condition 3, the exposure amount adjustment parameter indicates that the exposure amount of the correction target pixel is decreased by 12.5%. Therefore, the parameter setting unit 602 notifies / sets the exposure amount adjustment unit 603 to reduce the exposure amount of the correction target pixel by 12.5%.

  In step S13, the image analysis unit 601 specifies a correction target pixel based on the correction width parameter and the image data. In step S14, the exposure adjustment unit 603 adjusts and corrects the exposure of the correction target pixel based on the exposure adjustment parameter. Thereafter, in S15, the exposure amount adjustment unit 603 determines whether or not a pixel having the same exposure amount continues for a correction target pixel for a predetermined number of threshold values or more. If the predetermined number or more does not continue, the CPU 10 forms an image in S17. On the other hand, if a predetermined number or more continues, the exposure adjustment unit 603 selects an exposure pattern of the correction target pixel from the exposure pattern data 113 stored in the memory 111 in S16, and forms an image in S17. In this way, the exposure amount adjustment unit 603 determines an exposure pattern based on the exposure pattern data 113 when the same exposure amount continues. After forming the image in S17, the CPU 10 determines whether the printing is finished in S18. If not finished, the CPU 10 repeats the processing from S10.

  FIG. 8A shows pixel values of image data. The pixel value “255” is black, and the pixel value “0” indicates white, that is, a pixel to which toner is not attached. FIG. 8B shows a pixel that the image analysis unit 601 specifies as a correction target pixel when the correction width parameter is “3”. In FIG. 8B, a value “0” indicates a pixel that is not a correction target, and a pixel having a value other than “0” indicates a correction target pixel. The value of the correction target pixel indicates the distance from the edge (shortest value). The image analysis unit 601 specifies a correction target pixel and notifies the exposure amount adjustment unit 603 of distance information from the edge regarding the pixel.

  Next, exposure amount correction based on the exposure amount adjustment parameter in the exposure amount adjustment unit 603 will be described. In this embodiment, the exposure intensity is constant at a predetermined value Va, and one pixel is divided into N sub-pixels, and then the number of sub-pixels exposed at the predetermined value and the number of sub-pixels not exposed are changed. The exposure amount of one pixel is adjusted. FIG. 9A shows a case where the exposure amount of the pixel whose pixel value is “255” is reduced by 12.5% when N = 8. Note that the exposure amount of the pixel value “255” before correction is 100%, which corresponds to exposing all the subpixels with a predetermined value. That is, FIG. 9A shows an example in which one pixel is exposed with an exposure amount of 87.5%. FIG. 9B shows a case where the exposure amount of a pixel whose pixel value is “255” is reduced by 25%, that is, a case where one pixel is exposed with an exposure amount of 75%.

  Here, one pulse of the PWM signal corresponds to one sub-pixel, but in the case where pixels with the same exposure amount are continuous, it is unnecessary from the image forming apparatus 101 if the exposure patterns of the pixels with the same exposure amount are the same. Radiant noise is likely to occur. Here, the exposure pattern of one pixel is a pattern of subpixels that are exposed and one pixel that are not exposed, that is, an on / off pattern of a PWM signal corresponding to one pixel. For this reason, in the present embodiment, for each exposure amount, the exposure pattern of each pixel used when a predetermined number or more of pixels having the same exposure amount continue is stored in the memory 11 as exposure pattern data 113 in advance. deep.

  FIG. 10A shows an exposure pattern of each pixel when five pixels having an exposure amount of 87.5% are consecutive. Similarly, FIG. 10B shows an exposure pattern of each pixel when five pixels having an exposure amount of 75% are consecutive. In FIGS. 10A and 10B, the number of consecutive pixels to be exposed between sub-pixels not to be exposed is different. Therefore, unnecessary radiation can be suppressed as compared with the case where the exposure patterns of the five pixels are the same. When the exposure time shown in FIG. 9 (A) is repeated and the exposure pattern shown in FIG. 10 (A) is used when the scanning time of one pixel is 80 nsec, the Fourier transform result of the radiation noise is shown in FIG. Shown in The spectrum intensity when exposed as shown in FIG. 10A can be suppressed to about half of the spectrum intensity when the exposure pattern of FIG. 9A is repeated.

  In FIGS. 10A and 10B, in order to prevent density unevenness, the non-exposed subpixels of adjacent pixels are not connected. In this manner, the exposure amount adjustment unit 603 determines whether or not the corrected exposure amount is continuous for 5 pixels or more. If not, for example, the exposure pattern shown in FIG. 9 is used. If it is continuous, the exposure pattern shown in FIG. 10 is used. Thereby, unnecessary radiation noise can be suppressed.

  Unlike the edge effect, sweeping occurs only on the rear end side in the rotation direction of the photoconductor 1 of the image. Therefore, when correcting sweeping, the correction target pixel is the edge at the rear end in the rotation direction. The other processing is the same as the edge effect.

  In the flowchart of FIG. 6, it is determined whether the same exposure amount continues for a predetermined number or more only for the corrected exposure amount of the correction target pixel, and when the predetermined number or more continues, the predetermined number is based on the exposure pattern data 113. The exposure pattern was determined as follows. However, it may be configured to determine whether or not the same exposure amount continues for all the pixels after the exposure amount correction by the exposure adjustment parameter regardless of whether or not the pixel is a correction target pixel. In other words, when the same exposure amount continues for all the pixels after the exposure amount correction, an exposure pattern in units of a predetermined number may be determined based on the exposure pattern data 113. Moreover, although the case where five images were continued as an example was demonstrated above, it is not restricted to this, The number of continuous pixels can be set suitably.

  As described above, the image analysis unit 601 specifies the correction target pixel among the pixels of the image formed by the image data based on the image data and the correction width parameter. Then, the exposure amount adjustment unit 603 corrects the exposure amount by the exposure unit 7 for the correction target pixel from the exposure amount indicated by the image data using the exposure amount adjustment parameter. Furthermore, the exposure amount adjustment unit 603 determines a subpixel to be exposed and a subpixel not to be exposed for each pixel based on the corrected exposure amount of each pixel. At this time, the exposure amount adjustment unit 603 determines whether or not a predetermined number of pixels having the same exposure amount continue. When a predetermined number or more than a predetermined number of pixels having the same exposure amount are continuous, the predetermined number of consecutive pixels are sub-exposures for exposing each of the predetermined number of pixels based on the exposure pattern data 113 stored in the memory 11. A pixel and a sub-pixel that is not exposed are determined. For example, the predetermined number is 5 pixels as shown in FIG. It is assumed that 13 pixels having an exposure amount of 87.5% are continuous. In this case, the pattern shown in FIG. 10A is applied to the first five consecutive pixels. Then, the pattern of FIG. 10A is also applied to five consecutive pixels following the first five consecutive pixels. For the remaining three pixels, the pattern of the first three pixels in FIG. 10A is applied, or the pattern in FIG. 9A is repeated three times. As shown in FIG. 10, the memory 11 stores, as exposure pattern data 113, an exposure pattern in units of the predetermined number, which is used when a predetermined number of pixels having the same exposure amount continue for each exposure amount. Yes. In this exposure pattern data, the interval between the sub-pixels that are not exposed is not constant. More specifically, the intervals of the sub-pixels that are not exposed are all different. Thereby, unnecessary radiation noise can be suppressed as compared with repeating the pattern of FIG. 9A 13 times. The exposure amount adjustment unit 603 uses an exposure pattern in units of one pixel as shown in FIG. 9 when the number of consecutive pixels having the same exposure amount is less than a predetermined number. Further, even when the number of consecutive pixels having the same exposure amount is less than a predetermined number, it is possible to extract and apply a portion corresponding to the number of consecutive pixels from the exposure pattern of the predetermined number of pixels shown in FIG. For example, it is assumed that three pixels having an exposure amount of 87.5% are consecutive. In this case, instead of repeating the pattern of FIG. 9A three times, the exposure pattern of the first three pixels of FIG. 10A can be used. Furthermore, when pixels having the same exposure amount are continuous, the exposure pattern of a predetermined number of pixels shown in FIG. 10 may be applied regardless of the continuous number.

<Second embodiment>
In the first embodiment, when the number of consecutive pixels having the same exposure amount is less than a predetermined number, the exposure pattern is determined in units of one pixel. In the present embodiment, when the number of consecutive pixels having the same exposure amount is less than a predetermined number, the exposure pattern is determined in units of a plurality of pixels. In the following description, an example in which an exposure pattern is determined in units of two pixels will be described. FIG. 12 shows an example of the LUT 112 in the present embodiment. The main difference between FIG. 12 and the LUT 112 (FIG. 7) in the first embodiment is that the adjustment ratio of the exposure adjustment parameter is finely carved. That is, in FIG. 7, it is 12.5% increments, but in FIG. 12, it is 6.25% increments.

In order to correct the exposure amount in increments of 6.25%, when the exposure amount is controlled by dividing one pixel into 16 sub-pixels, the number of exposure pattern data 113 increases, thereby increasing the capacity to be stored. To do. Furthermore, it is necessary to improve the speed of the CPU 10. Therefore, in this embodiment, the number of subpixels of one pixel is eight. In this embodiment, the exposure pattern is determined in units of two pixels. In addition,
FIGS. 13A and 13B show exposure patterns when the exposure amount of a pixel having a pixel value “255”, that is, a pixel with an exposure amount of 100% is reduced by 6.25% and 18.75%, respectively. Is shown. In FIG. 13A, the exposure amount is reduced by 12.5% in the first pixel, but the exposure amount is not reduced in the second pixel, and thus the average exposure amount in the two pixels is reduced. The amount is 6.25%. Similarly, in FIG. 13B, the exposure amount is reduced by 25% in the first pixel and the exposure amount is reduced by 12.5% in the second pixel, so that the average exposure amount in the two pixels is reduced. The reduction amount is 18.75%. By adjusting the exposure amount in units of a plurality of pixels, although the density uniformity is slightly inferior, the exposure amount can be set finely without increasing the number of subpixels of one pixel. Note that when the correction target pixel is one pixel, the correction may not be performed.

  FIG. 14A shows an exposure pattern in the case where a predetermined number or more of pixels having an exposure amount of 93.75% are continuous, and in FIG. FIG. 14B shows an exposure pattern in a case where pixels having an exposure amount of 81.25% continue for a predetermined amount or more, and in FIG. 14B, six pixels or more continue. Similar to the first embodiment, since the exposure pattern is set so that the interval between the non-exposed subpixels is not constant, it is unnecessary as compared with the case of repeating the pattern shown in FIG. 13 (A) or FIG. 13 (B). Radiation noise can be suppressed.

  As described above, also in the present embodiment, when a predetermined number or more of pixels having the same exposure amount are consecutive, the exposure pattern for the predetermined number of consecutive pixels is determined based on the exposure pattern data 113 shown in FIG. On the other hand, when the number of consecutive pixels having the same exposure amount is less than a predetermined number, as shown in FIG. 13, an exposure pattern is determined in units of a plurality of pixels, in this embodiment, two pixels. Note that the number of pixels is a value less than a predetermined number. This reduces the edge effect or sweeping of the developer while suppressing radiation noise. Therefore, excessive consumption of toner can be suppressed. In addition, a fine step exposure amount can be set without increasing the number of subpixels.

[Other Embodiments]
The above embodiments have been described using the image forming apparatus 101. However, the present invention can also be realized as an image processing apparatus that outputs a PWM signal to the image forming apparatus. The image processing apparatus has an image calculation unit 9 shown in FIG. 1, corrects image data, determines an exposure pattern, and generates a PWM signal. Then, the image processing apparatus supplies and outputs a PWM signal to the image forming apparatus instead of the exposure unit 7.

  The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

  1: Photoconductor, 7: Exposure unit, 3: Development unit, 601: Image analysis unit, 603: Exposure adjustment unit, 11, Memory

Claims (13)

A photoreceptor,
Exposure means for exposing the photoreceptor to form an electrostatic latent image;
Developing means for developing the electrostatic latent image of the photoreceptor with a developer to form an image;
A specifying means for specifying a correction target pixel from among pixels of an image formed from the image data based on the image data;
Correction means for correcting an exposure amount by the exposure means for the correction target pixel from an exposure amount indicated by the image data;
Determining means for determining a sub-pixel to be exposed and a sub-pixel not to be exposed for each pixel based on an exposure amount of each pixel after correction by the correction means;
Storage means for storing an exposure pattern for a predetermined number of consecutive pixels having the same exposure amount for each exposure amount;
With
When the predetermined number of pixels having the same exposure amount continue for the predetermined number or more, the determining unit uses the exposure pattern stored in the storage unit for the pixels having the predetermined number or more, thereby exposing each predetermined number of pixels. Determine the subpixels to be exposed and the subpixels not to be exposed,
In the exposure pattern stored in the storage unit, the interval between the sub-pixels not exposed is not constant.   The image forming apparatus according to claim 1, wherein in the exposure pattern stored in the storage unit, the intervals of the sub-pixels not exposed are all different intervals.   3. The determination unit according to claim 1, wherein when the number of consecutive pixels having the same exposure amount is smaller than the predetermined number, the determination unit determines a sub-pixel to be exposed and a sub-pixel not to be exposed in units of one pixel. Image forming apparatus.   When the number of consecutive pixels having the same exposure amount is smaller than the predetermined number, the determining unit is a part of the exposure pattern of the predetermined number of pixels stored in the storage unit, and the same number of pixels as the continuous number is stored. The image forming apparatus according to claim 1, wherein a subpixel to be exposed and a subpixel to be not exposed are determined by a corresponding portion.   The determining unit determines a sub-pixel to be exposed and a sub-pixel not to be exposed in a plurality of pixel units smaller than the predetermined number when the number of consecutive pixels having the same exposure amount is smaller than the predetermined number. The image forming apparatus according to 1 or 2.   The said specifying means specifies the said correction target pixel based on the 1st information which shows a correction target pixel by the distance from the edge of the image formed with the said image data, The any one of Claim 1 to 5 characterized by the above-mentioned. The image forming apparatus described in the item. Holding means for holding a plurality of first information;
Detecting means for detecting state information indicating a state of the image forming apparatus;
Further comprising
The image forming apparatus according to claim 6, wherein the specifying unit determines first information used for specifying the correction target pixel from the plurality of first information based on state information detected by the detecting unit. apparatus.   The image forming apparatus according to claim 7, wherein the state information includes environment information.   The image forming apparatus according to claim 7, wherein the state information includes use state information indicating a degree of deterioration due to use of the image forming apparatus.   The image forming apparatus according to claim 1, wherein the correction unit corrects an exposure amount of the correction target pixel based on second information indicating a correction amount of the correction target pixel. .   The image forming apparatus according to claim 1, wherein the correction unit reduces an exposure amount of the correction target pixel from an exposure amount indicated by the image data. An image forming apparatus comprising: a photosensitive member; an exposing unit that exposes the photosensitive member to form an electrostatic latent image; and a developing unit that develops the electrostatic latent image of the photosensitive member with a developer to form an image. An image processing apparatus for supplying image data for forming the image,
A specifying means for specifying a correction target pixel from among pixels of an image formed from the image data based on the image data;
Correction means for correcting an exposure amount by the exposure means for the correction target pixel from an exposure amount indicated by the image data;
Determining means for determining a sub-pixel to be exposed and a sub-pixel not to be exposed for each pixel based on an exposure amount of each pixel after correction by the correction means;
Output means for outputting to the image forming apparatus information indicating a pixel to be exposed and a sub-pixel not to be exposed for each pixel determined by the determining means;
Storage means for storing an exposure pattern for a predetermined number of consecutive pixels having the same exposure amount for each exposure amount;
With
When the predetermined number of pixels having the same exposure amount continue for the predetermined number or more, the determining unit uses the exposure pattern stored in the storage unit for the pixels having the predetermined number or more, thereby exposing each predetermined number of pixels. Determine the subpixels to be exposed and the subpixels not to be exposed,
The image processing apparatus according to claim 1, wherein in the exposure pattern stored in the storage means, the interval between the sub-pixels not exposed is not constant.   A program for causing a computer to function as the image processing apparatus according to claim 12.

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