JP4270123B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus having a smoothing processing function.

In an image forming apparatus that reproduces halftones by performing error diffusion processing on input image data, in order to smooth out jagged edges (referred to as jaggy) of line images, character images, patch images, and the like. Smoothing processing is performed on the image data (see, for example, Patent Document 1 and Patent Document 2).
JP-A-9-130628 JP-A-10-336454

  However, when the smoothing process is performed on the image data, the jaggy at the edge portion is reduced, but there is a problem that a white spot is generated inside the halftone patch. This is because, within a halftone patch, a set of image data in which the error diffusion processed image data (dots on the transfer material) forming the patch is accidentally connected in a line shape is erroneously regarded as a line image. This is because, as a result of the discrimination and smoothing processing, the positions and sizes of dots that were originally scattered moderately are changed, and a gap between dots is generated. FIG. 8 shows an example of images before and after the smoothing process. As shown in FIG. 8, it can be seen that white spots (white spots) are generated in the area where dots are connected in a line shape in the image before the smoothing process.

  This problem can be solved if the image processing unit in the image forming apparatus has a very high discrimination accuracy of the image area and the edge part and the patch part can be completely separated, but the image data randomly scattered by the error diffusion process However, it is difficult to separate the image area. In addition, such a process is not preferable because it is expected to take a lot of time and cost for a large capacity memory.

  On the other hand, if the dots subjected to the smoothing process are made too large in order to prevent the occurrence of white spots, the dot gap will be reduced, but this time the dots that have been subjected to the smoothing process will be clustered and black dots (monochrome In the case of color, each color of the developing means is not preferable.

  An object of the present invention is to reduce the gap between dots that cause white spots by changing the size of the dots constituting the image data subjected to the smoothing process.

According to the first aspect of the present invention, there is provided an exposure unit that exposes an image carrier by a laser scanning optical system to form a latent image, and binarization that binarizes input image data using an error diffusion method. A processing unit;
A smoothing processing unit for performing a smoothing process for changing at least dot positions on the binarized image data; the image data on which the smoothing process has been performed among the binarized image data; and the smoothing A discriminating unit that discriminates image data that has not been processed, and a size of dots that constitute image data that has been discriminated by the discriminating unit from the binarized image data that has been subjected to the smoothing processing. A first change processing unit that makes the dot larger than the original dot, and main dots of the dots constituting the image data that is determined not to have been subjected to the smoothing process by the determination unit among the binarized image data Dot size can be changed by changing the width in the scanning direction within the range of 80 to 100% of the full-size dot width. Comprising a second changing unit for further, wherein the first changing unit, based on the size of the second dots is changed by changing unit, of the image data to which the smoothing processing has been performed A change process is performed so that the dot size does not exceed the dot size of the image data that has not been subjected to the smoothing process, and the exposure unit is based on the dot size changed by the first change processing unit. The exposure processing is performed.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the exposure unit emits light from the laser scanning optical system according to the dot size changed by the first change processing unit. It is characterized by changing.

  According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the exposure unit has a light emission intensity of the laser scanning optical system in accordance with a dot size changed by the first change processing unit. It is characterized by changing.

Invention according to claim 4, in the image forming apparatus according to claim 1, wherein the first change processing unit, the width of the dots in the main scanning direction of the image data to which the smoothing processing has been performed, the original It is characterized by being changed to 1.1 to 1.5 times the dot.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the exposure unit has the dot size changed by the second change processing unit. The light emission time of the laser scanning optical system is changed.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the exposure unit has the dot size changed by the second change processing unit. The light emission intensity of the laser scanning optical system is changed.

  According to the present invention, the image data binarized by the error diffusion method is subjected to the smoothing process, and the size of the dots constituting the image data subjected to the smoothing process is changed, so that the white point (the color of the transfer material) ) It is possible to reduce the gap between dots, which is the cause of the occurrence.

  In particular, it is possible to surely suppress the occurrence of white spots by changing the size of the dots constituting the image data subjected to the smoothing process so as to increase at a predetermined magnification.

  In addition, among the binarized image data, the dot size of the image data subjected to the smoothing process is changed at an appropriate magnification based on the size of the dots constituting the image data that has not been subjected to the smoothing process. As a result, even if there is a part that is misidentified as a line in the halftone patch, the occurrence of white spots and black spots (in the case of monochrome, each color of the developing means in the case of color) on the transfer material is suppressed. And the smoothness of the edge portion can be maintained.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First, the configuration in the present embodiment will be described.

  FIG. 1 shows a cross-sectional view of an image forming apparatus 100 to which the present invention is applied. As shown in FIG. 1, the image forming apparatus 100 includes an image reading unit 11 and an image forming main body unit 13.

  The image reading unit 11 is installed on the upper part of the image forming main body unit 13 and includes an automatic document feeder 11a and a document image scanning exposure device 11b. The automatic document feeder 11a conveys the document g placed on the document tray by the conveyance mechanism and sends it to the document image scanning exposure apparatus 11b. The document image scanning exposure apparatus 11b irradiates the conveyed document g (or the document g placed on the document table) with light from the light source, and the reflected light is converted into an electrical signal (analog) by a CCD (Charge-Coupled Device). A digital image signal (hereinafter referred to as image data) is obtained by converting the analog signal into a digital signal by an A / D converter.

  The image forming main body 13 includes an image forming unit 131 that forms an image, a fixing unit 7, and a paper feeding unit 8.

  The image forming unit 131 charges the exposure unit 1 that forms an electrostatic latent image by scanning a laser beam on an image carrier (photosensitive drum) with a polygon mirror, the image carrier 2, and the image carrier 2. The charging unit 3, the developing unit 4 that attaches toner on the image carrier 2, the transfer unit 5, and the cleaning unit 6 that cleans the toner remaining on the peripheral surface of the image carrier 2.

  The fixing unit 7 fixes the toner image on the recording paper P by performing a heat fixing process on the recording paper P as a transfer material.

  The paper feed unit 8 includes a paper feed cassette that stores recording paper P of various sizes, a paper feed roller, and the like, and conveys the recording paper P of a specified size to the image forming unit 131.

  FIG. 2 shows a main configuration of the control system of the image forming apparatus 100. As shown in FIG. 2, the image forming apparatus 100 includes a control unit 10, an image reading unit 11, an image processing unit 12, an image forming main body unit 13, a display operation unit 14, an image memory 15, and a storage unit 16. Note that the image reading unit 11 and the image forming main body unit 13 have already been described with reference to FIG.

  The control unit 10 is configured by a CPU (Central Processing Unit) or the like, and controls the operation of each unit of the image forming apparatus 100 according to a control program stored in the storage unit 16.

  The image processing unit 12 performs image processing on the image data input from the image reading unit 11 in accordance with a control signal input from the control unit 10. Details of the image processing unit 12 will be described later with reference to FIG.

  The display operation unit 14 includes a display unit 141 and an operation unit 142. The display unit 141 includes a display screen such as an LCD (Liquid Crystal Display), and performs a required display process according to a display control signal input from the control unit 10. The operation unit 142 includes various keys such as a copy start key and a numeric keypad, and outputs operation signals of these keys to the control unit 10. Further, the operation unit 142 has a touch panel provided so as to cover the display screen of the display unit 141, detects a coordinate instructed to be touched by a coordinate reading principle such as electromagnetic induction type, magnetostrictive type, pressure sensitive type, The detected coordinates are output to the control unit 10 as a position signal.

  The image memory 15 temporarily stores image data read by the image reading unit 11 and subjected to image processing by the image processing unit 12.

  The storage unit 16 is configured by an HD (Hard Disc), a nonvolatile semiconductor memory, or the like, and stores various control programs for controlling each unit of the image forming apparatus 100, data used in these programs, and the like.

  FIG. 3 shows the configuration of the image processing unit 12. As shown in FIG. 3, the image processing unit 12 includes an image data input unit 20, a binarization processing unit 21, a smoothing processing unit 22, a determination unit 23, a first change processing unit 24, and a second change processing unit 25. The image data output unit 26 is configured.

  The image data input unit 20 subjects the image data obtained by the image reading unit 11 to various image processing such as correction of variation in reading density in the image reading unit 11, area determination, data compression, and the like, and processed image data Is output to the binarization processing unit 21.

  The binarization processing unit 21 performs binarization processing on the image data input from the image data input unit 20 using an error diffusion method, and outputs the result to the smoothing processing unit 22.

  The smoothing processing unit 22 performs smoothing processing on the image data after binarization processing, adds smoothing information to the image data after smoothing processing, and outputs the image data to the determination unit 23. The smoothing information includes data indicating the presence / absence of the smoothing process for each pixel, and data regarding the smoothing process (dot size, dot position within the same pixel) for the pixels subjected to the smoothing process. .

  In this embodiment, a template matching method is used as the smoothing process. In this template matching method, a pixel arrangement around a target pixel is compared with a pixel arrangement of a template prepared in advance (for example, a template of 100 patterns or more), and when both match, the template is set. Based on the dot size and the dot position, the dot size and the dot position of the target pixel are changed. This algorithm is executed for all pixels to be image processed.

  FIG. 4 shows an example of a template used for template matching. In FIG. 4, when the pixel arrangement around the pixel of interest in the processing target image matches this template, the width of the dot of the pixel of interest in the main scanning direction is set to 60% of the original width, and the dot of the dot within the same pixel. This means that the position is right-justified.

  FIGS. 5A and 5B respectively show an example of changing the dot size and an example of changing the dot position in the smoothing process. In FIG. 5, the dot size is divided into six stages according to the width in the main scanning direction, with the original dot size being 100%, and there are three types of dot positions, left justified, center and right justified in one pixel. The case where it can be divided is shown.

  Note that the method of the smoothing process applied by the smoothing processing unit 22 is not limited to the template matching method, and other methods may be used.

  The discriminating unit 23 uses the smoothing information included in the image data input from the smoothing processing unit 22 to perform image data that has been subjected to the smoothing process (hereinafter referred to as image data α) and an image that has not been subjected to the smoothing process. Data (hereinafter referred to as image data β) is determined, and data indicating the determination result is output to the first change processing unit 24 and the second change processing unit 25.

  The first change processing unit 24 makes the dot size of the image data α out of the binarized image data larger than the original size at a predetermined magnification set according to the dot size of the image data β. The image data after the change processing is output to the image data output unit 26.

  In the dot size changing process in the first change processing unit 24, the dot size of the image data α is determined based on the data input from the second change processing unit 25 and indicating the dot size of the image data β. It is preferable not to exceed the dot size of the data β. This is because if the dot size of the image data α is larger than the dot size of the image data β, black spots (black in the case of monochrome, each color in the image forming unit 131 in the case of color) may be generated, or instead jaggy. This is because there is a possibility of occurrence. In addition, when the dots of the image data β are made smaller in order to reduce the toner consumption, if the dot size of the image data α is larger, a smoothing process is often performed. When printing a large amount of toner, the toner consumption may increase unexpectedly.

  The following two methods can be applied as means for changing the dot size for the image data α.

  The first size changing method is a method of changing the dot width (pulse width) in the main scanning direction by changing the light emission time of the laser scanning optical system in the exposure unit 1 (pulse width modulation).

  In the second size changing method, the light emission intensity (laser power) of the laser scanning optical system in the exposure unit 1 is changed (light intensity modulation), whereby the dot width in the main scanning direction and / or the length in the sub-scanning direction. It is a method to change.

  The second change processing unit 25 changes the dot size of the image data β that has not been subjected to the smoothing process in the binarized image data within a range in which the solid image density does not change, and the change process The subsequent image data is output to the image data output unit 26, and data indicating the changed dot size is output to the first change processing unit 24. The change of the dot size in the second change processing unit 25 depends on γ of the image forming unit 131, but it is preferable to change the width of the full size dot in the main scanning direction in the range of 80% to 100%. Here, γ in the image forming unit 131 means gradation that is determined by image forming (mainly charging, exposure, development) conditions of the image carrier.

  As the dot size changing means in the second change processing unit 25, as in the first size change processing unit 24, one of the first size change method and the second size change method described above is applied. be able to.

  The image data output unit 26 synthesizes the image data input from the first change processing unit 24 and the image data input from the second change processing unit 25, and combines the combined image data with the image forming main body unit 13. Output to.

  In order to stably suppress the occurrence of white spots or black spots in the image data, dot reproduction is performed for at least one of the charging conditions, the developing conditions, and the exposure conditions in the image forming section 131 in accordance with the variation of γ in the image forming section 131. It is preferable to correct so that the property is constant. The timing of these corrections includes, for example, every predetermined number of printed sheets, every predetermined driving time in the image forming unit 131, every predetermined driving distance, etc. when the environment changes.

  Next, a specific example of the dot size changing process in the first change processing unit 24 and the second change processing unit 25 will be described with reference to Example 1 and Example 2. In the following Example 1 and Example 2, the following conditions are adopted in the image processing unit 12, the image forming unit 131, and the fixing unit 7 unless otherwise specified.

Image formation method: electrophotographic (Carlson process) dry two-component magnetic brush reversal development method;
Image carrier: negatively charged OPC (Organic Photo Conductor) drum (film thickness 30 μm), drum diameter φ = 80 mm, linear rotation speed 280 mm / sec, charging potential −750 V;
Band electrode: Scorotron, charging current value -800μA, grid voltage -730V;
Exposure section: laser scanning method, wavelength 780 nm, resolution 600 dpi, laser power (emission intensity) = 150 to 500 μW (typical 300 μW), beam diameter main scanning direction 60 μm, beam diameter sub-scanning direction 80 μm, incident angle to OPC drum = 10 Degrees (= 0.17 radians), 256 exposure levels with pulse width modulation;
Halftone reproduction method: binary error diffusion method;
Smoothing processing: The size and position of the dot at the edge detected by the template matching method is changed. Size change is 6 levels with the width of dots in the main scanning direction divided into 6 levels. There are three types of dot position changes: left justified, center and right justified within the same pixel.
Developer in developing section: carrier particle size 60 μm, toner particle size 6.5 μm (non-magnetic, manufactured by emulsion polymerization method), toner concentration 5%, shape factor SF-1 = 120, shape factor SF-2 = 110;
Here, the shape factor SF-1 indicates the degree of sphericity, and the shape factor SF-2 indicates the degree of unevenness, which are defined as Equation (1) and Equation (2), respectively.
SF-1 = (Lmax ² / A) × (π / 4) × 100 (1),
SF-2 = (Laround ² / A) × (1 / 4π) × 100 (2),
Lmax: maximum diameter, Laround: circumference, A: toner projected area;
Developing unit in developing unit: bias-600V, sleeve diameter φ = 40mm, rotation linear velocity 560mm / sec, developing magnetic angle +6 degrees, toner recycling system to return residual toner removed by cleaning to developing unit, developing magnet Vertical magnetic field peak magnetic flux density 100mT, OPC drum surface to developing sleeve surface distance 0.50mm, developer transport amount 90mg / cm ² ;
Toner density control: Detect the toner density using a magnetic permeability sensor and control the replenishment toner amount;
Transfer separation electrode: electrostatic transfer / electrostatic separation method;
Cleaning part: Urethane rubber blade counter system;
Fixing part: Heat roller fixing method.

  In each of the following examples, when a non-magnetic toner is used for the developing portion, it is particularly effective when a small-diameter polymerized toner is employed. This is because the small-diameter polymerized toner has a sharp physical property distribution, a uniform shape, and a small diameter, so that the dot reproducibility is good, and thereby, the dot gap or dot grouping that is the problem to be solved by the present invention. This is because white spots or black spots are likely to occur. In particular, it is effective to use a toner having a toner particle size of 9 μm or less, a shape factor SF-1 of 100 to 140, and a shape factor SF-2 of 100 to 120.

  Example 1 shows an example in which the width in the main scanning direction of the dot subjected to the smoothing process is changed by changing the exposure time of the laser scanning optical system in the exposure unit (pulse width modulation).

  FIG. 6 shows the occurrence of white spots and black spots inside the halftone patch (absolute reflection image density is 0.4 to 0.6) when the image processing is performed in the first embodiment. In FIG. 6, D1a is a magnification that makes the width of the dot of the image data α subjected to the smoothing process larger in the main scanning direction than the width of the original dot by pulse width modulation, and D1b is subjected to the smoothing process. This is a ratio (%) to the width of the full dot size when the width in the main scanning direction of the dots of the image data β not changed is changed by pulse width modulation. FIG. 6 shows the result of visual observation for each combination of values of D1a and D1b and the result of observation with a magnification set to 30 times with a microscope. Further, in FIG. 6, “no white spots / black spots” means that white spots / black spots did not occur even when observed at a magnification of 30 times with a microscope.

  In FIG. 6, as described above, the dot size of the image data α that has been subjected to the smoothing process is controlled so as not to exceed the dot size of the image data β that has not been subjected to the smoothing process.

  FIG. 6 shows the result when the width of the dot of the image data β that has not been subjected to the smoothing process is changed by pulse width modulation. The width of the dot in the main scanning direction is the light intensity. Even when it is changed by modulation, the same result as in FIG. 6 is obtained.

  According to FIG. 6, it can be seen that when D1a = 1.0 to 1.1 times, the larger the dots that have not been subjected to the smoothing process, the more the generation of white spots cannot be suppressed. At D1a = 1.1 to 1.2 times, it is not noticeable visually, but it can be seen that white spots are generated when enlarged by a microscope. When D1a is 1.6 times or more, the smaller the dots that have not been subjected to the smoothing process, the more black spots cannot be suppressed. When D1a = 1.4 to 1.5 times, it is not conspicuous visually, but it can be seen that black spots are generated when enlarged by a microscope. It can be seen that when D1a = 1.2 to 1.4 times, white spots or black spots are not generated by visual observation or magnification by a microscope, regardless of the size of the dots that have not been subjected to the smoothing process. Further, since the size of the dot subjected to the smoothing process is changed uniformly, the edge portion hardly fluctuates, and the edge is within the range of D1a = 1.2 to 1.4 times. The jaggy of the part can be kept in a smooth state.

  Example 2 shows an example in which the width in the main scanning direction of the dot subjected to the smoothing process is changed by changing the light emission intensity (laser power) of the laser scanning optical system in the exposure unit (light intensity modulation).

  FIG. 7 shows the occurrence of white spots and black spots inside the halftone patch (absolute reflection image density is 0.4 to 0.6) when the image processing in the second embodiment is performed. In FIG. 7, D2a is a magnification for making the width of the dot of the image data α subjected to the smoothing process larger in the main scanning direction than the original dot width by light intensity modulation, and D2b is the smoothing process. This is the ratio (%) to the width of the full dot size when the width in the main scanning direction of the dots of the image data β not changed is changed by pulse width modulation. FIG. 7 shows the result of visual observation for each combination of the values of D2a and D2b and the result of observation with a magnification set to 30 times with a microscope. Further, in FIG. 7, “no white spot / black spot” means that no white spot / black spot was generated even when observed with a microscope at a magnification of 30 times.

  Further, also in FIG. 7, as described above, the dot size of the image data α that has been subjected to the smoothing process is controlled so as not to exceed the dot size of the image data β that has not been subjected to the smoothing process. .

  FIG. 7 shows the result when the width of the dot of the image data β not subjected to the smoothing process in the main scanning direction is changed by pulse width modulation. The width of the dot in the main scanning direction is represented by the light intensity. Even when it is changed by modulation, the same result as in FIG. 7 is obtained.

  According to FIG. 7, it can be seen that when D2a = 1.0 to 1.1 times, the larger the dots that have not been subjected to the smoothing process, the more the occurrence of white spots cannot be suppressed. At D2a = 1.1 to 1.2 times, it is not noticeable visually, but it can be seen that white spots are generated when enlarged by a microscope. When D2a = 1.6 times or more, the smaller the dots that have not been subjected to the smoothing process, the more difficult it is to suppress the occurrence of black spots. When D2a = 1.4 to 1.5 times, it is not conspicuous by visual observation, but it can be seen that black spots are generated when enlarged by a microscope. It can be seen that when D2a = 1.2 to 1.4 times, white spots or black spots are not generated by visual observation or enlargement with a microscope, regardless of the size of the dots that have not been subjected to the smoothing process. Further, since the size of the dot subjected to the smoothing process is changed uniformly, the edge portion hardly fluctuates, and if D2a is within the range of 1.2 to 1.4 times, the edge The jaggy of the part can be kept in a smooth state.

  Comparing FIG. 6 and FIG. 7, it can be seen that Example 1 and Example 2 have the same result. This is because both have the same dot reproducibility. As a result, even if the dot reproducibility changes due to environmental fluctuations or aging of consumable parts, always correcting the charging conditions, development conditions, exposure conditions, etc. in the image forming unit 131 so that the dot reproducibility is the same. It is possible to obtain an image without white spots or black spots.

  Further, according to the results of Example 1 and Example 2, in order to obtain an image with no occurrence of white spots or black spots, the width of the dots of the image data α subjected to the smoothing process in the main scanning direction is set to the original width. It may be 1.1 to 1.5 times, more preferably 1.2 to 1.4 times the dot width.

  As described above, according to the embodiment of the present invention, Example 1 and Example 2, among the image data binarized by the error diffusion method, the dots constituting the image data α subjected to the smoothing process are displayed. By changing the size so that it is larger than the original size, it is possible to reduce the dot gap that causes white spots.

  Also, among the binarized image data, the dot size of the image data α that has been subjected to the smoothing process is set at an appropriate magnification based on the size of the dots that constitute the image data β that has not been subjected to the smoothing process. By changing, even if there is image data misidentified as a line inside the halftone patch, the occurrence of white spots and black spots on the transfer material can be suppressed, and the smoothness of the edge portion can be reduced. Can keep.

1 is a cross-sectional view of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a main configuration of a control system of the image forming apparatus according to the present exemplary embodiment. It is a block diagram which shows the structure of an image process part. It is a figure which shows an example of the template data used by the template matching of a smoothing process. It is a figure which shows the change of the dot size in a smoothing process, and the change of a dot position. FIG. 6 is a diagram illustrating the occurrence of white spots / black spots inside a halftone patch according to the first embodiment. FIG. 10 is a diagram illustrating the occurrence of white spots and black spots inside a halftone patch in Example 2. It is a figure which shows an example of the image before a smoothing process, and the image after a smoothing process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exposure part 2 Image carrier 3 Charging part 4 Developing part 5 Transfer part 6 Cleaning part 7 Fixing part 8 Feeding part 10 Control part 11 Image reading part 12 Image processing part 13 Image forming main body part 131 Image forming part 14 Display operation part Reference Signs List 15 image memory 16 storage unit 20 image data input unit 21 binarization processing unit 22 smoothing processing unit 23 discrimination unit 24 first change processing unit 25 second change processing unit 26 image data output unit 100 image forming apparatus

Claims (6)

An exposure unit that exposes the image carrier with a laser scanning optical system to form a latent image;
A binarization processing unit that binarizes the input image data using an error diffusion method;
A smoothing processing unit for performing a smoothing process of changing at least the position of the dots with respect to the binarized image data;
Among the binarized image data, a determination unit for determining image data that has been subjected to the smoothing process and image data that has not been subjected to the smoothing process;
A first change processing unit that makes a size of a dot constituting the image data determined to have been subjected to the smoothing processing by the determination unit out of the binarized image data, larger than the original dot;
Of the binarized image data, the width in the main scanning direction of the dots constituting the image data determined not to have been subjected to the smoothing process by the determination unit is set with respect to the width of the full size dot. A second change processing unit that changes the size of the dots by changing in a range of 80 to 100% ,
In the first change processing unit, the dot size of the image data subjected to the smoothing process is not subjected to the smoothing process based on the dot size changed by the second change processing unit. Change the image data so that it does not exceed the dot size.
The image forming apparatus, wherein the exposure unit performs an exposure process based on a dot size changed by the first change processing unit.   The image forming apparatus according to claim 1, wherein the exposure unit changes a light emission time of the laser scanning optical system according to a dot size changed by the first change processing unit.   The image forming apparatus according to claim 1, wherein the exposure unit changes a light emission intensity of the laser scanning optical system according to a dot size changed by the first change processing unit.   The first change processing unit changes the dot width in the main scanning direction of the image data subjected to the smoothing process to 1.1 to 1.5 times the original dot. The image forming apparatus according to 1. The said exposure part changes the light emission time of the said laser scanning optical system according to the size of the dot changed by the said 2nd change process part , The any one of Claims 1-4 characterized by the above-mentioned. Image forming apparatus. The said exposure part changes the light emission intensity | strength of the said laser scanning optical system according to the size of the dot changed by the said 2nd change process part , The any one of Claims 1-4 characterized by the above-mentioned. Image forming apparatus.

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