JP2006195246A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which the number of pixels can be corrected by recognizing an exact state of toner adhesion per dot, and an exact count number of pixel consumption can be obtained with a reduced amount of toner consumption even with lapse of time. <P>SOLUTION: The image forming apparatus of an electrophotographic system including a pixel number counter to count the written the pixel number is equipped with an adjacent pixel recognition means to recognize the write information of the pixel adjacent to the notice pixel in image data and a pixel number correcting means to correct the number of pixels of the notice pixel by the write information of the adjacent pixels and to input the same to the pixel number counter. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotographic image forming apparatus using pixel number counting means.

  In image forming apparatuses that record by attaching toner to paper according to image data, such as laser printers, digital copiers, and plain paper facsimile machines, the number of dots of pixels written on the photoconductor is counted and added. The cumulative amount of toner is detected (see, for example, Patent Document 1). In performing such a pixel count, the amount of toner consumed for writing one pixel is converted using a reference table (lookup table, LUT) and added to the count value thus far. A correction method to be obtained is known (for example, see Patent Document 2). In addition, Patent Document 3 also touches on a technique for accurately predicting the toner consumption based on the number of pixels counted by correcting each image element and the number of corrected pixels.

  In Japanese Patent Laid-Open No. 2004-260260, a pixel count count addition value is acquired by selecting from a plurality of LUTs according to the size of the writing resolution or the toner remaining amount detection result. In addition, by recognizing the relationship between adjacent pixels of each pixel to be written, an addition value for an isolated / thin line / dense pixel is obtained more accurately. FIG. 11 is a block diagram of the main part of the image forming apparatus in Patent Document 2. In FIG. 11, converted values obtained by giving multi-valued image data corresponding to each pixel to the LUT 111 are input to an adder and a counter to obtain a count value (toner consumption) per page or cumulative number of pixels. . By inputting the image data to the address input terminal of the LUT 111, the converted value of the image data stored in the LUT 111 in advance is output, the value is set in the adder 112, and the set value and the adder 113 are set. When the remaining lower bits are added to the carry (upper bit), the carry causes the counter 114 to count up. This counter output value becomes the cumulative pixel count value.

Japanese Patent Laid-Open No. 07-005766 JP 2002-244495 A JP 2002-214865 A

  However, in an electrophotographic image forming apparatus, one dot (one pixel) written on the image carrier is greatly affected by the dots adjacent thereto. For this reason, even with the same 1-dot writing pixel, the amount of toner adhering to one dot differs between one dot in white solid and one dot in black solid. Therefore, in the case of the toner consumption detection method that counts one pixel as it is without considering the state of adjacent pixels, a large error occurs over time, and accurate residual toner amount detection and toner end detection based on the pixel count number are performed. There is a bug that you can not.

  Accordingly, in the present invention, an accurate toner adhesion amount state for each dot can be recognized, the number of pixels can be corrected, and an accurate consumption pixel count number can be obtained with little toner consumption amount detection error over time. An object is to provide a forming apparatus.

According to a first aspect of the present invention, there is provided an electrophotographic image forming apparatus for writing input image data on an image carrier with a laser beam and developing the toner using toner, and a pixel number counter for counting the number of written pixels. An image forming apparatus comprising: an adjacent pixel recognizing unit that recognizes write information of a pixel adjacent to a target pixel, correcting the number of pixels of the target pixel based on the write information of the adjacent pixel, and inputting the corrected pixel number to the pixel number counter The correction means is provided. As a result, by grasping the accurate number of consumed pixels, it is possible to grasp an accurate cumulative pixel count without error even over time, and to always present accurate toner remaining amount information to the user. In addition, since accurate toner consumption can be grasped, toner end and toner near end can be detected without using a mechanical toner end sensor, and the mechanism can be simplified and the cost can be reduced.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the pixel number correcting means sums the number of pixels that have been written among several pixels adjacent to the target pixel. The number of pixels of interest is corrected based on a coefficient corresponding to the total number. The effects described above can be obtained, and a more accurate cumulative pixel count can be obtained by increasing the number of sampling of the peripheral dots.

  According to the third aspect of the present invention, the multi-value control is possible for the writing of the image data. The same effect as described above can also be obtained in multi-value control using an intermediate light quantity that can realize smoother gradation. According to a fourth aspect of the present invention, in the image forming apparatus according to the first or second aspect, writing of image data can be multi-value controlled, and the pixel number correcting means refers to a look-up table during multi-value control writing. The number of pixels of interest can be corrected based on the coefficient obtained in this way, and the lookup table is changed for each type of image processing such as a difference in output mode. For this reason, the above-described effect can be obtained even in multi-value control using an intermediate light quantity that can realize smoother gradation.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect of the present invention, the image data writing can be multi-value controlled, and the pixel number correcting means can select the type of image processing such as the difference in the selected output mode. Accordingly, the number of pixels counted at the time of writing is corrected by multiplying by a coefficient determined for each image processing. For this reason, the above-mentioned effect can be obtained even in multi-value control using an intermediate light quantity that can realize smooth gradation.

  According to the present invention, an accurate toner adhesion amount state for each dot can be recognized, the number of pixels can be corrected, and an accurate consumption pixel count number can be obtained with little toner consumption amount detection error over time. A forming device is obtained. The toner end or toner near end can be detected without using a mechanical toner end sensor. In this case, the mechanism can be simplified and the cost can be reduced.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The exemplary apparatus described below applies the present invention to a color image forming apparatus installed in a color copying machine or the like, but the present invention can be similarly applied to a monochrome image forming apparatus. FIG. 1 is a side sectional view showing the overall configuration of a color image forming apparatus according to an embodiment of the present invention.

  In the color image forming apparatus 100 shown in FIG. 1, the photosensitive member that carries the electrostatic latent image formed by laser writing and the developed toner image is a photosensitive belt as a flexible belt-like image carrier. 1. The photosensitive belt 1 is installed between the rotation rollers 2, 31, 32, and is rotated (sub-scanned) in the direction of arrow A (clockwise) in the drawing by the rotation driving of the rotation roller 2, and the belt surface is The image forming surface is configured. As means for forming an electrostatic latent image and a toner image on the photoreceptor belt 1, a charging charger 4 for uniformly charging the surface of the photoreceptor belt 1, a laser writing unit 5, color developing devices 6a, 6b, 6c, 6d. The color developing devices 6a, 6b, 6c, and 6d are composed of developing units for magenta, cyan, yellow, and black, which are color constituent colors. The developing unit used here includes developing means adapted to perform development with a one-component developer (toner).

  Further, the exemplary apparatus has an intermediate transfer belt 10 because the image on the photosensitive belt 1 is formed on the transfer paper via the intermediate transfer member. The intermediate transfer belt 10 is installed between the rotation rollers 11 and 12, and is rotated in the direction of arrow B (counterclockwise) in the drawing by the rotation driving of the rotation roller 11. The photosensitive belt 1 and the intermediate transfer belt 10 are in contact with each other at a portion where the rotation roller 32 of the photosensitive belt 1 is provided. On the intermediate transfer belt 10 side of the contact portion, a conductive bias roller 13 is in contact with the back surface of the intermediate transfer belt 10 under predetermined conditions. Constituent elements related to transfer paper processing include a paper feed unit (paper cassette) 17, paper feed roller 18, transport roller pair 19 a and 19 b, registration roller pair 20 a and 20 b, and intermediate transfer belt 10. A transfer roller 14 for transferring the image, a fixing device 80, a pair of paper discharge rollers 81a and 81b, and a paper discharge stack portion 82.

  Here, an image forming operation of the color image forming apparatus 100 of the embodiment shown in FIG. 1 will be described. In FIG. 1, a photosensitive belt 1 as a flexible belt-like image carrier is uniformly charged by a charger 4 and then laser light is controlled by a laser writing unit 5 based on image information. As a result of this scanning exposure, an electrostatic latent image is formed on the surface. The image information used in one step of scanning and exposing the photosensitive belt 1 while rotating it in the direction of arrow A in FIG. 1 to form an electrostatic latent image is a magenta, cyan, yellow, and black color of a desired full-color image. This is monochromatic image information decomposed into information, and the light emission of the semiconductor laser is controlled by this information. The generated laser beam is scanned and optical path adjusted by an optical device, and output as writing beam light L. The electrostatic latent image formed based on the monochrome image information is converted into magenta (M), cyan (C), yellow (Y), and black (Bk) toners by the color developing devices 6a, 6b, 6c, and 6d. Each color image is developed, and each color image is sequentially formed on the photosensitive belt 1.

  The M, C, Y, and Bk monochromatic images formed on the photosensitive belt 1 rotating in the direction of arrow A are synchronized with the photosensitive belt 1 and are intermediate transfer belts rotating in the direction of arrow B in FIG. Then, the images are sequentially transferred onto the upper surface 10 by the action of a predetermined transfer bias applied to the bias roller 13. The M, C, Y, and Bk images superimposed on the intermediate transfer belt 10 are fed from a paper feed table (paper feed cassette) 17 through a paper feed roller 18, transport roller pairs 19a and 19b, and resist roller pairs 20a and 20b. The transfer roller 14 collectively transfers the transfer paper 17a conveyed to the transfer unit. After the transfer is completed, the transfer paper 17a is fixed by the fixing device 80 to complete a full-color image, and the print image is discharged to the paper discharge stack section 82 through the paper discharge roller pair 81a and 81b.

  Note that the toner on the photosensitive belt 1 is cleaned as the final step of image formation on the photosensitive belt 1 in FIG. For this purpose, a cleaning blade 15 that is always in contact with the photosensitive belt 1 is provided. Similarly, the intermediate transfer belt 10 is also provided with a cleaning device 16. The cleaning brush 16a of the cleaning device 16 is held at a position separated from the surface of the intermediate transfer belt 10 during the image forming operation, and after the formed image is transferred onto the transfer paper 17a, it is brought into contact with the surface of the intermediate transfer belt 10. The Further, the photosensitive belt 1, the charging charger 4, the intermediate transfer belt 10, the cleaning blade 15, and the cleaning device 16 can be integrated so as to be detachable from the main body as a process cartridge.

  Next, the control system of the color image forming apparatus shown in FIG. 1 will be described. FIG. 2 is a schematic block diagram showing an example of the control system of this color image forming apparatus. As shown in FIG. 2, in addition to the functions described so far, a main control unit 101, an operation display unit 102, an image memory unit 107, an optical writing unit 108, and the like are provided.

  The operation display unit 102 includes a touch panel or the like fixed to a housing of a machine main body (not shown), and includes a display unit that displays an image for a user and an operation unit that receives a key input from the user. Then, an image is displayed based on a control signal from the main control unit 101, or input information received by the operation unit is output to the main control unit 101. The main control unit 101 includes a ROM, a RAM, a CPU, and the like (not shown) and controls the entire machine. The operation display unit 102, the paper feed unit 103, the fixing unit 104, the secondary transfer roller 105, and the intermediate transfer unit 106 are electrically connected. Furthermore, an image memory unit 107, an optical writing unit (optical unit) 108, a photosensitive unit 110, a developing unit 111, and the like are also electrically connected.

  Color image information sent from a personal computer or a scanner (not shown) is temporarily stored in the image memory unit 107 via the main control unit 101 and then written in the optical writing unit 108 as color separation image data for each color. Control circuit 109. The writing control circuit 109 drives the semiconductor laser while rotating the polygon mirror by driving the polygon motor based on the transmitted color separation image data. The laser beam LD emitted from the semiconductor laser by this driving is reflected by a regular hexahedral polygon mirror and deflected in the main scanning direction, while optically scanning the photoreceptor of the photoreceptor unit 110 via a reflection mirror (not shown). To do. The writing control circuit 109 calculates the number of writing pixels based on the color separation image data of each color, and transmits the result to the main control unit 101.

  Each color developing device consumes toner as it develops the electrostatic latent image on the surface of the photoreceptor. The main control unit 101 serving as a control unit performs predetermined control necessary for consumption of toner based on the calculated value of the number of write pixels sent from the write control circuit 109 for each color developing device. It has become. The main control unit 101 performs toner near-end determination processing and toner end determination processing as related predetermined control. The toner near-end determination process is a process for individually determining whether or not the remaining amount of toner in the developing device of each color is about to disappear, and reporting the toner near-end to the user when it is likely to disappear. It is. The toner end determination process is a process for determining whether or not to issue a toner shortage alarm for each color developing device and notifying the user of the toner shortage alarm according to the result.

  In the following, the pixel number correcting means in the case of monochromatic two gradation control in the present embodiment will be described. The pixel number correcting means can be realized in a form including an adjacent pixel recognizing means mainly including a process with an arithmetic function executed by a CPU in the main control unit 101 according to a predetermined program. Of course, the entire configuration may be configured as dedicated hardware controlled by the main control unit 101.

3A to 3D show a target pixel and an adjacent pixel adjacent thereto in the present embodiment. The center of the 3 × 3 matrix is the target pixel, and the surrounding eight pixels are referred to as adjacent pixels. For example, Fig. 3 (a)
The amount of toner adhering to the pixel of interest differs between when there is no writing in the adjacent pixel and when there is writing in four of the adjacent pixels as shown in FIG. This is because, as schematically shown in FIG. 4, the laser beams of adjacent dots are overlapped, so that the overlapped portion is in a state equivalent to the case where a stronger light amount is irradiated on the photoconductor. .

In the example of this embodiment, the following formula (1) is established, where A is the number of pixels of interest that are written, and 1 is the number of pixels of interest when there is writing in all pixels adjacent to the pixel of interest.
A = 0.75 + 0.25 × n / 8 (1)
Here, n is the number of writing in adjacent pixels.
For example, in FIG. 3C, since n = 4, A = 0.875 pixels.

Further, even if there is no writing in the target pixel, if there is writing in the adjacent pixel, the toner actually adheres to the target pixel due to the influence, so if the number of the target pixel when there is no writing in the target pixel is B In the example of the present embodiment, the following expression (2) is established.
B = 0 + 0.25 x n / 8 (2)
Holds.
For example, in FIG. 3D, since n = 6, B = 0.1875 pixels.

  The pixel number A or B of the target pixel described above is sequentially added to the pixel number counter as the corrected pixel number and accumulated, and is referred to for processing related to the toner consumption amount.

  Next, the operation of the pixel number correcting unit in the case of multi-value control in the embodiment will be described. In the apparatus (laser writing apparatus) of the present embodiment, multi-value control is performed for writing, and there are nine writing light amounts. In simple terms, there are nine tones of light intensity from full light emission to extinction. In the apparatus of the present embodiment, since 600 dots / inc, 1 pixel = 1 dot is formed by a circle of about 0.042 mm.

  For example, as schematically shown in FIG. 5, even when a full-color image is output (FIG. 5 (a)), when the light amount of one pixel is full (8/8) light amount (black solid), 3 / In 8 light quantities (halftone), the density is different, resulting in a difference between a black solid image (b) and a halftone image (c). At this time, the amount of toner adhering to the photoconductor naturally varies. The graph in FIG. 6 illustrates the relationship between the write light amount and the toner adhesion amount. Because it has an S-shaped curve with a central γ (tilt), the 1/8 and 2/8 light levels are almost the same as the 0/8 light level, and the 6/8 and 7/8 light levels are almost the same. Black solid with the same amount of toner as 8/8 light. FIG. 7 shows a look-up table corresponding to the relationship between the write value and the pixel number C. By changing the weighting between the write value (light amount value) 0/8 to 8/8, it is possible to obtain the number of pixels C corrected more accurately according to the write light amount.

  As described above, the correction of the number of pixels for correcting the number of pixels of interest based on the writing information of adjacent pixels is also effective for multilevel writing. In this case, the pixel number C corrected using the look-up table in FIG. 7 may be associated with the target pixel in FIG. 3 and each adjacent pixel. FIG. 8 is a diagram illustrating an example of the corrected number of pixels of the target pixel and adjacent pixels.

As shown in FIG. 8A, assuming that the number of corrected pixels A ′, the number C0 of multi-valued write pixels of the target pixel, the adjacent pixels n1 to n8, and the number of multivalued write pixels C1 to C8, respectively, 3) holds.
A '= 0.75 x C0 + 0.25 x (n1 x C1 + n2 x C2 + ... n8 x C8) / 8 (3)
Holds.

For example, if the target pixel and the adjacent pixel have a write value as shown in FIG.
A '= 0.75 × 0.9 + 0.25 × (1 × 1 + 1 × 1 + 1 × 0.3 + 1 × 0.3 + 0 + 1 × 0.1 + 1 × 0.1 + 0) / 8
= 0.675 + 0.0875 = 0.7625 pixels.

  Multi-level write light intensity control includes laser beam light intensity and duty ratio (ON, OFF interval is 600 dpi, but the ON time is shortened to reduce 1 dot light intensity). Pixel number correction control is established.

[Second Embodiment]
The pixel number correction means in the first embodiment described above is very accurate because correction is performed for each pixel. However, since the calculation is performed for each pixel, the main control unit 101 requires high processing capability. Is done. The processing power of computing devices has been dramatically improved with the advancement of computers, and in the future, it is predicted that high-processing power and low-priced CPUs will be mainstream. A very effective and simpler method is shown as a second embodiment.

  The second embodiment corresponds to multi-value control, and corrects the number of pixels based on the selected image processing mode. That is, the correction value of the lookup table in the pixel number correction unit is determined according to the type of image processing. For example, in the case of a copying machine, the selected image processing includes a character photo mode, a character mode, and a photo mode. Similar to the first embodiment, the pixel value correcting means can be realized mainly by a process with an arithmetic function executed by a CPU in the main control unit 101 according to a predetermined program. Note that the lookup table may be incorporated as in Patent Document 2 (see FIG. 11).

  In the image forming apparatus according to the second embodiment, the pixel number correcting unit is configured to be able to correct the number of pixels of the target pixel based on the coefficient obtained by referring to the look-up table at the time of multi-value control writing. The look-up table is changed for each type of image processing, such as the difference between the two.

  An example of a lookup table used for counting the number of pixels is shown in FIG. A number of such look-up tables exist independently for each color and mode, and a predetermined look-up table associated with the color and mode selected at the time of output is used for pixel number correction. Therefore, even if the same document is copied, the total number of pixels of the document that is corrected and output to the pixel number counter differs depending on the output mode selected at the time of copying. Accordingly, the cumulative pixel count number and the actual toner consumption can be controlled almost in proportion.

In the case of only the above-described correction, even if image processing is performed in the same character mode, the relationship between the cumulative pixel count and the toner consumption amount is slightly shifted due to the image area ratio, the image density, and the like. Therefore, in the present embodiment, in order to obtain higher accuracy, the correction coefficient k as shown in the table of FIG. 9 is multiplied for correction by the pixel number correcting means.
That is, assuming that the total number of pixels in one page is B and the total number of corrected pixels is B ′, the corrected number of pixels B ′ is easily derived by the following equation (4).
B ′ = B × k ………… (4)

  The sampling number of adjacent pixels, the look-up table, and various coefficients described so far are numerical values optimized in the apparatus of this embodiment. In actual implementation, exposure characteristics, photoconductor characteristics, development characteristics, etc. The optimum value differs depending on the case. The correction described in the first embodiment may be used in combination with the correction in the second embodiment described above.

  [Embodiment] Next, an embodiment of toner end detection processing and toner near end detection processing will be described. When these processes are performed, if a monochrome Bk full-color image is output with a resolution of 600 dots / inc and a single A4 size, the pixel area of Bk is 31.68 Mdot (normally there are several mm write-protected areas on the top, bottom, left and right, The effective size was calculated as 8inc × 11inc (1Mdot = 1000000dot).

  The toner consumption amount can be grasped by the pixel count number (Ngaso) obtained by adding the pixel area for each image formation for each color immediately after the toner supply. For example, if 100 sheets of all A4 monochrome Bk solids are output after replenishing toner, the pixel count will be 3168M pixel count. The number guaranteed for use with one toner cartridge is generally calculated as A4, 5%. In the case of 3000 toner cartridges, the pixel count (Ngmax) at the end of toner is 31.68M × 0.05 × 3000 = 4752M pixels. Therefore, with the 3168M pixel count, it can be seen that the cartridge consumption is 67% and the toner remaining amount is 33%.

  FIG. 10 shows a flowchart of pixel number addition, toner end detection, and toner near end detection during output. When an image formation command for one page is issued, image formation information (image information of one page of print or copy data) is obtained, and based on this information, a pixel number count A (M, C, Y, K) is obtained (step; S11), and added to the pixel count number Ngaso (M, C, Y, K) of each color individually (step; S12).

  In this embodiment, the toner near end is displayed before the toner end (step; S13). This is because Ngaso (M, C, Y, K) has 792M pixels that can output 500 sheets at A4, 5%, and toner end (pixel count number Ngmax (M, C, It is determined whether or not the value subtracted from (Y, K)) has been reached (step; S13), and when it is reached (S13: Yes), Ngaso (M, C, Y, K) further guarantees the toner cartridge of each color. It is determined whether or not the pixel count number Ngmax (M, C, Y, K) corresponding to the number of sheets has been reached (step; S14). If not reached (S14: No), the toner near end is displayed and the next is displayed. The process proceeds to the next page (step; S15). In this embodiment, the number is equivalent to 500. However, since the machine speed and user needs differ depending on the model, an optimum value may be set for the near-end number. In the case of No in step S13, the process proceeds to the next page.

  As described above, it is determined whether Ngaso (M, C, Y, K) has reached the pixel count number Ngmax (M, C, Y, K) corresponding to the guaranteed number of toner cartridges for each color (step; S14). In step S16, when it is reached (S14: Yes), it is determined that the toner end is reached, and the toner end is displayed to stop image formation (step S16). When Ngmax (M, C, Y, K) is not reached (S14: No), the toner near-end display is displayed as described above (step S15). In this embodiment, the image forming operation of the machine is stopped, but it may be determined by the user without stopping depending on the use conditions.

1 is a side sectional view of a color image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic block diagram illustrating an example of a control system of the color image forming apparatus in FIG. 1. (a)-(d) is explanatory drawing which showed the attention pixel and the adjacent pixel adjacent to it in embodiment. It is a conceptual diagram which shows typically a mode that toner adheres to a pixel. (a)-(c) is explanatory drawing which shows typically a mode that a toner adheres to a pixel. 6 is a graph showing a relationship between a write light amount and a toner adhesion amount. 6 is a look-up table corresponding to the relationship between a write value and the number of pixels C. (a), (b) is a figure which shows the example of the corrected pixel number of an attention pixel and an adjacent pixel. It is a table | surface figure which shows an example of the correction coefficient k in a pixel number correction | amendment means. It is a flowchart which shows one Example of a process of an apparatus. It is a block diagram which shows the known structure for a pixel number count.

Explanation of symbols

1 ... Photoreceptor belt (photoreceptor)
4 ... Charging charger 5 ... Laser writing units 6a, 6b, 6c, 6d ... Color developing device 10 ... Intermediate transfer belt 14 ... Transfer roller 16 ... Cleaning device 17 ... Paper feed stand (paper feed cassette)
80 ... fixing device 82 ... paper discharge stack unit 100 ... color image forming apparatus 101 ... main control unit 102 ... operation display unit 103 ... feed unit 104 ... fixing unit 105 ... secondary transfer roller 106 ... intermediate transfer unit 107 ... image memory Unit 108: Optical writing unit (optical unit)
109 ... Write control circuit 110 ... Photoconductor unit 111 ... Development unit

Claims (5)

An electrophotographic image forming apparatus that writes input image data on an image carrier with a laser beam and develops the toner using a toner, the image forming apparatus including a pixel number counter that counts the number of written pixels.
An adjacent pixel recognition unit that recognizes writing information of a pixel adjacent to the target pixel, and a pixel number correction unit that corrects the number of pixels of the target pixel based on the writing information of the adjacent pixel and inputs the corrected pixel number to the pixel number counter. An image forming apparatus.   The pixel number correcting means adds up the number of pixels that have been written among several pixels adjacent to the target pixel, and corrects the number of pixels of the target pixel based on a coefficient corresponding to the total number. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the writing of the image data is capable of multi-value control.   The writing of the image data can be multi-value controlled, and the pixel number correction unit is configured to be able to correct the number of pixels of the target pixel based on a coefficient obtained by referring to a look-up table at the time of multi-value control writing. The image forming apparatus according to claim 1, wherein the lookup table is changed for each type of image processing such as a mode difference. The writing of the image data can be multi-value controlled, and the pixel number correcting means determines the number of pixels counted at the time of writing for each image processing according to the type of image processing such as the difference in the selected output mode. The image forming apparatus according to claim 4, wherein the correction is performed by multiplying the obtained coefficient.

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