Color image forming apparatus and method

Abstract

The application provides a color image forming device and method, which comprises a controller, laser scanning units corresponding to each color channel, and photosensitive members corresponding to each laser scanning unit. The laser scanning units perform laser scanning on the corresponding photosensitive members in a non-constant linear velocity in a main scanning direction to form an electrostatic latent image. The controller modulates the scanning frequency of the laser scanning units according to a frequency characteristic curve, so that the scanning frequency of the laser scanning units at the end of the photosensitive member is high, and image data is added at a preset position, and the laser scanning units are controlled to not emit light in the section corresponding to the image data. Therefore, before scanning the first effective data of the image to be formed, the added image data is scanned first, so that the scanning frequency of the first effective data can be increased to a certain value. Since the laser scanning units do not emit light in the section corresponding to the added image data, the added image data will not form an image, and the normal formation of the image to be formed is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical scanning, and in particular to a color image forming device and method. BACKGROUND

[0002] A laser printer generally includes a laser scanning unit for exposing a photosensitive member. The laser scanning unit emits laser light according to image data, the laser light is reflected by a rotating polygon mirror, the reflected light is transmitted through a scanning lens, and the transmitted light irradiates a photosensitive drum to expose the photosensitive drum. As the polygon mirror rotates, the laser spot formed on the surface of the photosensitive drum moves continuously to achieve scanning, thereby forming a latent image on the photosensitive member.

[0003] When the angular velocity of the polygon mirror is constant, since the distance between the polygon mirror and the two ends of the photosensitive drum and the distance in the middle of the photosensitive drum are different, and the linear velocity is equal to the angular velocity multiplied by the radius, the linear velocity of the light spot moving in the main scanning direction is not constant. This inconsistency in linear velocity can cause scanning deviation, i.e., the formed print effect can have misaligned pixels and inconsistent pixel width.

[0004] The prior art has a technology of performing electrical correction to change the image clock frequency during a scanning operation, so that when the light spot does not move at a uniform speed on the surface of the photosensitive member, the light spot formed on the surface of the photosensitive member does not have pixel deviation.

[0005] However, in the above technology, since the laser scanning starts from one end of the photosensitive drum to the other end of the photosensitive drum, and the light emission period at the end is short, the scanning frequency is high, and the existing controller needs to first raise the scanning frequency to a certain value before changing along the modulation curve. However, the existing type of chip has a slow time to raise the scanning frequency to a certain value when modulating the frequency, resulting in that when the first effective data needs to be scanned, the scanning frequency has not yet been raised to a certain value, so that the image cannot be normally formed. SUMMARY

[0006] The present application provides a color image forming device and method to solve the problem that when the first effective data is scanned, the scanning frequency has not yet been raised to a certain value, and the image cannot be normally formed.

[0007] In a first aspect, the present application provides a color image forming device, the device comprising:

[0008] a controller, a plurality of laser scanning units corresponding to a plurality of color channels, and a plurality of photosensitive members corresponding to the plurality of laser scanning units;

[0009] the laser scanning units are configured to perform laser scanning on the corresponding photosensitive members in the main scanning direction at a non-constant linear velocity to form an electrostatic latent image;

[0010] The controller is configured to modulate the scanning frequency of the laser scanning unit according to a frequency modulation characteristic curve, so as to make the scanning frequency of the laser scanning unit at the end portions of the photosensitive member higher than the scanning frequency at the intermediate portion between the end portions.

[0011] The controller is further configured to add image data at a preset position to increase the width of the image to be formed.

[0012] The controller is further configured to control the laser scanning unit to not emit light in the first section corresponding to the image data.

[0013] Optionally, the controller is configured to add at least one column of image data at the initial printing side of each color channel corresponding to the image to be formed, so as to increase the width of the image to be formed.

[0014] Optionally, the controller is configured to add the same number of columns of image data at the initial printing side of each color channel corresponding to the image to be formed.

[0015] Optionally, the controller is configured to add different numbers of columns of image data at the initial printing side of each color channel corresponding to the image to be formed.

[0016] The controller is further configured to shift the image data of at least one color channel to the left or to the right to calibrate the color registration.

[0017] Optionally, the controller is configured to add image data at one side of the image to be formed in the scanning direction to increase the width of the image to be formed.

[0018] Optionally, the controller is further configured to add image data at a side of the image to be formed other than the scanning direction to increase the width of the image to be formed.

[0019] Optionally, the controller is configured to add image data at the initial printing side of the image to be formed according to the width of the printing paper, and the width of the image to be formed after the addition is less than or equal to the width of the printing paper.

[0020] Optionally, the laser scanning unit comprises a rotating polygon mirror that reflects the laser, and the laser reflected by the rotating polygon mirror is applied to the photosensitive member through an image forming lens to form an electrostatic latent image on the photosensitive member.

[0021] In a second aspect, the present application provides a color image forming method, which is used in a color image forming apparatus, the apparatus comprising a plurality of laser scanning units corresponding to a plurality of color channels, and a plurality of photosensitive members corresponding to the plurality of laser scanning units, the method comprising:

[0022] modulating a scanning frequency of the laser scanning unit according to a frequency modulation characteristic curve, so as to make the scanning frequency of the laser scanning unit at the end portions of the photosensitive member higher than the scanning frequency at the intermediate portion between the end portions;

[0023] adding image data at a preset position to increase a width of the image to be formed;

[0024] controlling the laser scanning unit to not emit light at the position corresponding to the image data;

[0025] controlling the laser scanning unit to perform laser scanning on the photosensitive member at a non-constant line speed in the main scanning direction to form the latent electrostatic image.

[0026] Optionally, the adding image data at a preset position to increase a width of the image to be formed specifically comprises:

[0027] adding at least one column of image data image at an initial printing side of each color channel corresponding to the image to be formed to increase the width of the image to be formed.

[0028] The color image forming apparatus provided by the present application can increase the scanning frequency during the period of scanning the added image data, so that when the first effective data is scanned, the scanning frequency can be increased to a certain value, and since the laser scanning unit does not emit light in the first section corresponding to the added image data, the added image data will not form an image, thereby ensuring the normal formation of the image to be formed. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0030] Figure 1 is a schematic view of an image forming apparatus;

[0031] Figure 2 is a sectional view of a laser scanning unit along the main scanning direction;

[0032] Figure 3 is a schematic view of a solution to scanning deviation;

[0033] Figure 4 is a schematic view of a frequency modulation characteristic curve;

[0034] Figure 5 is a schematic view of a frequency modulation characteristic curve of an embodiment of the present application;

[0035] Figure 6 An image diagram provided for an embodiment of the present application;

[0036] Figure 7 An image width diagram for an embodiment of the present application;

[0037] Figure 8 A flow diagram of a color image forming method for an embodiment of the present application. DETAILED DESCRIPTION

[0038] For the purpose of making the purpose, technical scheme and advantages of the present application more clear, the technical scheme of the present application will be described clearly and completely below in combination with the drawings in the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0039] Figure 1 A diagram of an image forming apparatus is shown, as shown in Figure 1 The image forming apparatus includes an image signal generating unit 100, a control unit 1, a laser scanning unit 400 and a photosensitive drum 4. The image signal generating unit 100 outputs an image signal, the control unit 1 outputs a control signal, and a laser driving unit 300 in the laser scanning unit 400 generates a scanning light (laser) 208 in response to the image signal and the control signal, and scans onto the photosensitive drum 4. The photosensitive drum 4 with a charged surface is scanned by the laser 208, so that a latent image is formed on the surface of the photosensitive drum 4. The image forming apparatus further includes a developing unit (not shown), which applies toner to the latent image to form a toner image corresponding to the latent image, and the toner image is transferred to a recording medium (such as paper), thus completing an image forming process. An example of the controller of the present application is the whole composed of the image signal generating unit 100 and the control unit 1.

[0040] Figure 2 is an interface diagram of the laser scanning unit 400 along the main scanning direction. The main scanning direction is a direction parallel to the surface of the photosensitive drum 4 and orthogonal to the moving direction on the surface of the photosensitive drum 4. In this exemplary embodiment, the laser (light beam) emitted by the laser emitting unit 401 is reflected by the reflecting surface of the rotating polygon mirror 405 after passing through the optical lens group (not shown), as the scanning light 208, which irradiates the scanning surface 407 of the photosensitive drum 4, forming a photoelectric image. In the case where the rotating polygon mirror 405 is rotated in the direction indicated by the arrow A at a constant angular velocity by the driving unit (not shown), the light spot moves on the scanning surface 407 in the main scanning direction, so that an electrostatic latent image is formed on the scanning surface 407.

[0041] It can be understood that the basic principle of the image forming device is to charge the surface of the photosensitive drum 4 with static electricity, and then use the laser emitting unit 401 to emit laser on the photosensitive drum 4 in one direction row by row. The laser emitting unit 401 can emit light or not emit light in a unit time. The place where the light is emitted forms a latent image, and the subsequent adsorption of carbon powder forms an image. The place where the light is not emitted will not form an image.

[0042] By Figure 2 As can be seen, the position of the laser emitting unit 401 is fixed. In order to make the laser move on the scanning surface 407, the laser needs to be deflected by rotating the rotating polygon mirror 405 to make the light beam scan in the same direction multiple times. When the rotation angular velocity of the rotating polygon mirror 405 is constant, since the distance between the rotating polygon mirror 405 and the two ends of the photosensitive drum 4 and the distance in the middle of the photosensitive drum 4 are different, and the linear velocity is equal to the angular velocity multiplied by the radius, therefore the linear velocity of the light spot moving in the main scanning direction is not constant, that is, the linear velocity at the two ends of the photosensitive drum 4 is greater than that at the center of the photosensitive drum 4. This inconsistency of linear velocity can cause scanning deviation, that is, the printing effect formed may have misaligned pixels or inconsistent pixel width.

[0043] The traditional correction method is optical correction. By designing the image forming lens 406 as a lens with F-θ characteristics, the F-θ lens can realize linear scanning with equal angular velocity of incident light, so that the moving speed of the light spot in the scanning direction of the photosensitive drum 405 is uniform. However, the lens with F-θ characteristics tends to be large in volume, which needs to occupy more space inside the printer, and is also high in price. Or, the F-θ lens of some image forming devices is not sufficient to completely correct the laser in the main scanning direction to be linear.

[0044] For this, the prior art discloses a method of adjusting the control period to reduce the scanning deviation, the principle of which is shown in Figure 3 , which makes the control period T2 of the image pixels in the end region shorter than the control period T1 of the image pixels in the central region, so that the light emitting period of the laser at the end of the photosensitive drum is shorter, and the light emitting period of the laser at the center of the photosensitive drum is longer, to correct the imbalance of the linear velocity.

[0045] Since the laser scanning starts from one end to the other end, and the light emitting period at the end is short, the frequency is high. The existing controller such as the SOC (System on Chip) of the printer needs to first raise the scanning frequency to a certain value when modulating the frequency, and then change along the modulation curve. However, the time for raising the scanning frequency to a certain value when modulating the frequency of the existing type of chip is relatively slow, so that when the first effective data needs to be scanned, the scanning frequency has not yet been raised to a certain value, so that the image cannot be normally formed.

[0046] Based on the above problems, the present application provides a color image forming device, a controller is configured to increase image data at a preset position to increase the width of the image to be formed, and control the laser scanning unit not to emit light in the first section corresponding to the image data, so that the period of scanning the increased image data can be used as the period of increasing the scanning frequency, so that the modulation frequency can be increased to a certain value when scanning the first effective data, and because the laser scanning unit does not emit light in the first section corresponding to the increased image data, the increased image data will not form an image, thereby ensuring the normal formation of the image to be formed.

[0047] The technical solutions of the present application will be described in detail below with specific examples. The following specific examples can be combined with each other, and the same or similar concepts or processes may not be described in detail in some examples.

[0048] The color image forming device provided by the embodiments of the present application comprises:

[0049] A controller, a plurality of laser scanning units corresponding to the color channels, and a plurality of photosensitive members corresponding to the laser scanning units.

[0050] The laser scanning unit is configured to perform laser scanning on the corresponding photosensitive member in the main scanning direction at a non-constant linear velocity to form an electrostatic latent image.

[0051] The controller is configured to modulate the scanning frequency of the laser scanning unit according to the frequency modulation characteristic curve, so that the scanning frequency of the laser scanning unit at the end of the photosensitive member is higher than the scanning frequency at the intermediate part between the ends; is further configured to increase image data at a preset position to increase the width of the image to be formed; and is further configured to control the laser scanning unit not to emit light in the first section corresponding to the image data.

[0052] In an implementation manner, one end of the actual frequency modulation characteristic curve of the controller has a section, i.e., a first section, that does not conform to the standard frequency modulation characteristic curve, and the increased image data is used to make the laser scanning unit not emit light in the first section, so as to avoid the scanning unit performing laser scanning at a frequency that does not conform to the frequency modulation characteristic curve; after the first section ends, the remaining section conforms to the frequency modulation characteristic, so that the laser scanning unit can perform laser scanning at a frequency that conforms to the frequency modulation characteristic curve, so as to obtain an accurate electrostatic latent image.

[0053] In the embodiments of the present application, the color image forming device comprises a plurality of laser scanning units and a plurality of photosensitive members, each color channel corresponds to a laser scanning unit, and each laser scanning unit corresponds to a photosensitive member. In actual application, the color image forming device can comprise four laser scanning units corresponding to four color channels, wherein the four color channels comprise a cyan color channel, a magenta color channel, a yellow color channel, and a black color channel.

[0054] For any laser scanning unit in the color image forming apparatus, the laser emitted by the laser emitting unit 401 is reflected by the reflective surface of the rotating polygon mirror 405 as scanning light 208. This scanning light 208 illuminates the scanning surface 407 of the photosensitive drum 4, forming a photoelectric image. When the rotating polygon mirror 405 rotates at a constant angular velocity in the direction indicated by arrow A, the light spot moves on the scanning surface 407 in the main scanning direction, causing an electrostatic latent image to form on the scanning surface 407. Figure 2 As shown. Since the rotational angular velocity of the rotating polygonal mirror 405 is constant, the distance between the reflecting surface and the end region of the photosensitive drum is farther than that between the end regions. Furthermore, since linear velocity is equal to the product of angular velocity and radius, it is easy to see that the scanning linear velocity is higher in the end region than in the middle region between the end regions. That is, the scanning unit of this embodiment performs laser scanning on the surface of the photosensitive member with a non-constant linear velocity, so the scanning speed in the end region on the scanning surface 407 is higher than that in the middle region.

[0055] To address scanning deviations caused by inconsistent linear velocities, the controller is configured to modulate the scanning frequency of the laser scanning unit according to a frequency modulation characteristic curve. This ensures that the scanning frequency at the ends of the photosensitive element is higher than the scanning frequency in the middle section between the ends, thus correcting for uneven scanning linear velocities. It can be understood that the frequencies at the two ends of the frequency modulation characteristic curve are higher than the frequencies at the midpoint between the ends, such as... Figure 4 As shown.

[0056] Furthermore, since laser scanning moves from one end of the photosensitive component to the other, the scanning frequency needs to be increased to a certain value first. This increase is relatively slow, meaning that by the time the first valid data is scanned, the scanning frequency hasn't reached the required level, preventing proper image data formation. Therefore, the controller is also configured to add image data at a preset position to increase the width of the image to be formed and to control the laser scanning unit to not emit light within the first segment corresponding to the added image data. Before scanning the first valid data of the image to be formed, the added image data is scanned first. During the period of scanning the added image data, the scanning frequency can be increased so that it reaches a certain value when scanning the first valid data. Since the laser scanning unit doesn't emit light within the first segment corresponding to the added image data, the added image data won't form an image, thus ensuring the normal formation of the image to be formed. Figure 6 As shown. For example, after adding image data at a preset location, the actual effective curve of frequency modulation is as follows. Figure 5 As shown.

[0057] In some examples, the controller increases the image data on one side of the image to be formed along the scanning direction to increase the width of the image to be formed. The scanning direction can be determined according to the characteristics of the laser scanning unit, for example, one type of laser scanning unit is configured to scan from left to right along the axis direction of the photosensitive drum, and the image data can be increased on the left side of the image data of the image to be formed; another type of laser scanning unit is configured to scan from right to left along the axis direction of the photosensitive drum, and the image data can be increased on the right side of the image data of the image to be formed. The above scanning process corresponds to one row of pixels in the image data. It can be understood that one page of image data is composed of multiple rows of image pixels, and multiple scans need to be performed, so during the printing of one page of image data, the same width of image data is added to each row of one color channel to improve the accuracy of one page of image data.

[0058] Since the laser scanning unit does not emit light in the first section corresponding to the increased image data, the increased image data will not form an image, which can avoid the laser scanning unit to perform laser scanning to form a defective latent image when the frequency characteristics do not meet the requirements.

[0059] The controller can also increase the image data on the side other than the side of the image to be formed along the scanning direction to increase the width of the image to be formed. For example, when the image data of the image to be formed is scanned from left to right, the image data can be increased on the right side of the image data of the image to be formed; when the image data of the image to be formed is scanned from right to left, the image data can be increased on the left side of the image data of the image to be formed. At this time, the final width of the image to be formed is the actual effective width X of the image to be formed + the width of the image corresponding to the left increased image data (N bit columns) + the width of the image corresponding to the right increased image data (M bit columns), as shown in Figure 7 The number of columns of the image data increased on both sides can be the same or different. For example, the actual effective width of the image to be formed is X bit, the width of the image corresponding to the left increased image data can be configured as N bit columns of white space, and the width of the image corresponding to the right increased image data can be configured as M bit columns of white space (N, M are arbitrary values). In actual application, the final width of the image to be formed is an integer multiple of 2 Y bit (Y can be determined according to the word length of the controller).

[0060] For example, at least one column of image data can be increased on the initial printing side of the cyan channel, at least one column of image data can be increased on the initial printing side of the magenta channel, at least one column of image data can be increased on the initial printing side of the yellow channel, and at least one column of data can be increased on the initial printing side of the black channel. In some implementations, the initial printing side refers to the side where the laser scanning unit starts scanning, for example, in the embodiment shown in Figure 5 the left side is the initial printing side.

[0061] As an implementation, the controller can increase the image data of the same column number on the initial printing side of each color channel corresponding to the image to be formed, or increase the image data of different column numbers, which needs to be determined according to the color registration deviation between different color channels. Color registration refers to the requirement that multiple colors need to be accurately overlapped together when printing a color pattern using multiple color channels. If there is a color registration deviation between different channels, the output image will have color misregistration and other problems, thereby reducing the image quality. In the embodiment of the present application, different color channels can have different frequency modulation characteristic curves, and thus different widths of image data need to be increased. Otherwise, if the same width of image data is increased for different frequency modulation characteristic curves, the output image will have color registration deviation. Therefore, the implementation of the embodiment of the present application can further solve the color registration deviation problem caused by different frequency modulation characteristic curves of different channels, and can avoid reducing the image quality.

[0062] As another implementation, the controller increases the image data of different column numbers on the initial printing side of each color channel corresponding to the image to be formed, and shifts the image data of at least one color channel to the left or to the right to calibrate the color registration. When the initial printing side of each color channel increases the image data of different column numbers, the image data of at least one color channel can be shifted to the left or to the right to shift the image of the color channel to the left or to the right, so that the images of each color channel are overlapped together, thereby ensuring the normal formation of the image to be formed. For example, a debug mode can be provided on the printer panel, and the debug personnel or maintenance personnel can set the column number of the image data to be increased for each color channel in the debug mode. This is because the frequency characteristics may change due to aging after the printer is shipped, and therefore a debug mode can be provided for the debug personnel to adjust the column number of the image data that has been increased before shipment.

[0063] For example, the controller increases the image data on the initial printing side of each color channel corresponding to the image to be formed according to the width of the printing paper, and the width of the image to be formed after the increase is less than or equal to the width of the printing paper, so as to ensure the integrity of the printing.

[0064] In a possible implementation, the laser scanning unit includes a rotating polygon mirror that reflects the laser, and the laser reflected by the rotating polygon mirror passes through the image forming lens and is applied to the photosensitive member to form an electrostatic latent image on the photosensitive member.

[0065] The color image forming apparatus provided by the embodiment of the present application is described in detail above, and the embodiment of the present application further provides a color image forming method. The color image forming method is used in the color image forming apparatus, and the color forming apparatus includes each laser scanning unit corresponding to each color channel, and each photosensitive member corresponding to each laser scanning unit, such as Figure 8As shown, the color image forming method provided by the embodiment of the present application comprises:

[0066] S101, modulating the scanning frequency of the laser scanning unit according to the frequency modulation characteristic curve, so that the scanning frequency of the laser scanning unit at the end of the photosensitive member is higher than that at the middle part between the ends.

[0067] In the embodiment, the frequency at both ends of the frequency modulation characteristic curve is higher than that at the middle position between the two ends, and then the scanning frequency of the laser scanning unit is modulated according to the frequency modulation characteristic curve, so that the scanning frequency of the laser scanning unit at the end of the photosensitive member is higher than that at the middle part between the ends, to correct the imbalance of the scanning line speed.

[0068] S102, adding image data at the preset position to increase the width of the image to be formed.

[0069] For example, the preset position is the initial printing side of each color channel, and at least one column of image data can be added at the initial printing side of each color channel corresponding to the image to be formed to increase the width of the image to be formed.

[0070] S103, controlling the laser scanning unit not to emit light in the first section corresponding to the image data.

[0071] Controlling the laser scanning unit not to emit light in the first section corresponding to the added image data, the first effective data of the image to be formed will be scanned first, and the scanning frequency can be increased during the period of scanning the added image data (for example, Figure 5 As shown), so that the scanning frequency can be increased to a certain value when scanning the first effective data, and since the laser scanning unit does not emit light in the section corresponding to the added image data, the added image data will not form an image, thereby ensuring the normal formation of the image to be formed.

[0072] S104, controlling the laser scanning unit to perform laser scanning on the corresponding photosensitive member in the main scanning direction at a non-constant line speed to form an electrostatic latent image.

[0073] The present embodiment can be applied to color image forming devices without F-θ lens, and can also be applied to color image forming devices containing optical correction lens but the correction characteristics of the lens are not sufficient to completely correct the scanning light beam to be linear. The same parts of the embodiment corresponding to the color image forming device will not be repeated here.

[0074] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for part or all of the technical features. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A color image forming apparatus characterized by comprising: The device comprises: a controller, each laser scanning unit corresponding to each color channel, and each photosensitive member corresponding to each laser scanning unit; the laser scanning unit is configured to perform laser scanning on the corresponding photosensitive member in the main scanning direction at a non-constant linear velocity to form an electrostatic latent image; the controller is configured to modulate the scanning frequency of the laser scanning unit according to a frequency modulation characteristic curve, so that the scanning frequency of the laser scanning unit at the end of the photosensitive member is higher than that at the middle part between the ends; the controller is further configured to increase image data at a preset position to increase the width of the image to be formed; the controller is further configured to control the laser scanning unit not to emit light in the first section corresponding to the image data; the controller is configured to increase at least one column of image data on the initial printing side of each color channel corresponding to the image to be formed, so as to increase the width of the image to be formed; wherein the controller is configured to increase different numbers of columns of image data on the initial printing side of each color channel corresponding to the image to be formed, or to increase the same number of columns of image data on the initial printing side of each color channel corresponding to the image to be formed.

2. The apparatus of claim 1, wherein, The controller is further configured to shift the image data of at least one color channel to the left or to the right to calibrate the color registration.

3. The apparatus of claim 1 or 2, wherein, The controller is configured to increase image data on one side of the image to be formed in the scanning direction to increase the width of the image to be formed.

4. The apparatus of claim 1 or 2, wherein, The controller is further configured to increase image data on a side of the image to be formed other than the scanning direction to increase the width of the image to be formed.

5. The apparatus of claim 1 or 2, wherein, The controller is configured to increase image data on the initial printing side of the image to be formed according to the width of the printing paper, and the width of the image to be formed after the increase is less than or equal to the width of the printing paper.

6. The apparatus of claim 1 or 2, wherein, The laser scanning unit comprises a rotating polygon mirror that reflects laser light, and the laser light reflected by the rotating polygon mirror is applied to the photosensitive member through an image forming lens to form an electrostatic latent image on the photosensitive member.

7. A color image forming method characterized by The method is used in a color image forming device, the device comprising each laser scanning unit corresponding to each color channel, and each photosensitive member corresponding to each laser scanning unit, and the method comprises: modulating the scanning frequency of the laser scanning unit according to a frequency modulation characteristic curve, so that the scanning frequency of the laser scanning unit at the end of the photosensitive member is higher than that at the middle part between the ends; increasing image data at a preset position to increase the width of the image to be formed; controlling the laser scanning unit not to emit light in the first section corresponding to the image data; controlling the laser scanning unit to perform laser scanning on the corresponding photosensitive member in the main scanning direction at a non-constant linear velocity to form an electrostatic latent image; wherein the image data is increased at a preset position to increase the width of the image to be formed; the increasing of the image data at the preset position to increase the width of the image to be formed specifically comprises: adding at least one column of image data images on the initial printing side of each color channel corresponding to the image to be formed to increase the width of the image to be formed; the adding at least one column of image data images on the initial printing side of each color channel corresponding to the image to be formed specifically comprises: adding different column numbers of image data on the initial printing side of each color channel corresponding to the image to be formed, or adding the same column numbers of image data on the initial printing side of each color channel corresponding to the image to be formed.

Images