Optical scanning device

Abstract

The present invention provides an optical scanning device that can make the black or white streaks at the seams connecting the scanning areas of multiple optical scanning devices less noticeable. [Solution] The present invention comprises a plurality of optical scanning devices, each including a photoreceptor, a light source, a light source lighting means for lighting the light source, a deflector for scanning the light from the light source lit by the light source lighting means on the photoreceptor in the main scanning direction, a light detection sensor positioned near the starting position of the light scanning in the main scanning direction, and a write control unit that determines a write timing to start scanning the light in the main scanning direction and controls the light source lighting means according to the write timing. The plurality of optical scanning devices divide the scanning area on the photoreceptor in the main scanning direction, scans the divided scanning area in directions away from each other, and generates and randomly varies the write timing based on a synchronization detection signal generated by receiving light with the light detection sensor.

Description

Technical Field

[0005]

[0001] The present invention relates to an optical scanning device.

Background Art

[0002] In an image forming apparatus that arranges a plurality of optical scanning devices side by side in the main scanning direction to realize a wide image area, a technique has been developed to increase the positional accuracy of the joints of the scanning areas of the plurality of optical scanning devices by setting the scanning directions of the plurality of optical scanning devices to be separated from each other starting from the starting point. Patent Document 1 discloses a configuration in which the scanning methods of a plurality of optical scanning devices are set to be separated from each other starting from the starting point for the purpose of preventing image quality degradation at the joints of the scanning areas of the plurality of optical scanning devices.

Summary of the Invention

Problems to be Solved by the Invention

[0003] However, in an image forming apparatus in which the scanning directions of a plurality of optical scanning devices are separated from each other starting from the starting point, when the writing positions of each optical scanning device are slightly shifted, the density of the images at the joints of the scanning areas of the plurality of optical scanning devices becomes stable for each scan, so white streaks and black streaks are likely to occur.

[0004] The present invention has been made in view of the above, and an object thereof is to provide an optical scanning device capable of making black streaks and white streaks at the joints of the scanning areas of a plurality of optical scanning devices less noticeable.

Means for Solving the Problems

[0005] To solve the above-mentioned problems and achieve the objective, the present invention has a plurality of optical scanning devices, each comprising: a photoreceptor; a light source; a light source lighting means for lighting the light source; a deflector for scanning the light from the light source lit by the light source lighting means on the photoreceptor in the main scanning direction; a light detection sensor positioned near the starting position of the light scanning in the main scanning direction; and a write control unit that determines a write timing to start scanning the light in the main scanning direction and controls the light source lighting means according to the write timing. The plurality of optical scanning devices divide the scanning area on the photoreceptor in the main scanning direction, scans the divided scanning area in directions away from each other, generates the write timing based on a synchronization detection signal generated by receiving light with the light detection sensor, and the write timing of each of the plurality of optical scanning devices randomly fluctuates every predetermined number of light scans in the main scanning direction. [Effects of the Invention]

[0006] According to the present invention, the black and white streaks at the seams between the scanning areas of multiple optical scanning devices can be made less noticeable. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a diagram illustrating an example of an image forming apparatus according to the first embodiment. [Figure 2] Figure 2 is a diagram illustrating an example of an imaging apparatus included in the image forming apparatus according to the first embodiment. [Figure 3] Figure 3 is a top view of the optical beam scanning device included in the image forming apparatus according to the first embodiment. [Figure 4] Figure 4 is a diagram illustrating an example of a light beam scanning apparatus included in the image forming apparatus according to the first embodiment. [Figure 5] Figure 5 is a diagram illustrating an example of a light beam scanning apparatus in an image forming apparatus according to the first embodiment. [Figure 6]Figure 6 is a diagram illustrating an example of dot arrangement drawn by two optical beam scanning devices in an image forming apparatus according to the first embodiment. [Figure 7] Figure 7 illustrates an example of black or white streaks that occur at the junction of the scanning areas of two optical beam scanning devices. [Figure 8] Figure 8 is a diagram illustrating an example of a light beam scanning device included in the image forming apparatus according to the first embodiment. [Figure 9] Figure 9 shows an example of a timing chart of an LGATE signal in which jitter is superimposed on the assertion timing in an image forming apparatus according to the first embodiment. [Figure 10] Figure 10 is a diagram illustrating an example of dot arrangement when jitter is introduced into the write timing in the image forming apparatus according to the first embodiment. [Figure 11] Figure 11 is a diagram illustrating an example in which the amount of jitter is changed according to image data in an image forming apparatus according to the second embodiment. [Figure 12] Figure 12 is a diagram illustrating an example of a hardware configuration for determining the grayscale of image data in an image forming apparatus according to the second embodiment. [Figure 13] Figure 13 is a diagram illustrating an example of a hardware configuration for determining the grayscale of image data in an image forming apparatus according to the second embodiment. [Figure 14] Figure 14 is a diagram illustrating an example of a process for determining the dot density at seams on a page-by-page basis in an image forming apparatus according to the second embodiment. [Modes for carrying out the invention]

[0008] An embodiment of an image forming apparatus using an optical scanning device will be described in detail below with reference to the attached drawings.

[0009] (First Embodiment) Figure 1 is a diagram illustrating an example of an image forming apparatus according to the first embodiment. The printer 100 of the image forming apparatus according to this embodiment has an intermediate transfer unit in the center, and the intermediate transfer unit has an endless belt, the intermediate transfer belt 10. The intermediate transfer belt 10 is wrapped around three support rollers 14 to 16 and is driven to rotate clockwise. To the right of the second support roller 15 is an intermediate transfer body cleaning unit 17 that removes residual toner remaining on the intermediate transfer belt 10 after image transfer. Along the direction of movement of the intermediate transfer belt 10 between the first support roller 14 and the second support roller 15 is an imaging apparatus 20 which has photoreceptor units 40 of yellow (Y), magenta (M), cyan (C), and black (K), a charging unit 18, a developing unit, and a cleaning unit, and the imaging apparatus 20 is detachably attached to the printer 100 body.

[0010] Above the imaging device 20 is a light beam scanning device 21 that irradiates each photoreceptor drum (an example of a photoreceptor) of each color photoreceptor unit with laser light for image formation. Below the intermediate transfer belt 10 is a secondary transfer unit 22. The secondary transfer unit 22 is positioned so as to push up the intermediate transfer belt 10 and press it against the third support roller 16 by stretching an endless belt, the secondary transfer belt 24, between two rollers 23. This secondary transfer belt 24 transfers the image on the intermediate transfer belt 10 onto the paper. Next to the secondary transfer unit 22 is a fixing unit 25 that fixes the transferred image on the paper, and the paper with the toner image transferred onto it is fed into it. The fixing unit 25 fixes the toner image transferred onto the paper to the paper by melting and pressing it using an endless belt, the fixing belt 26, and a heating and pressurizing roller 27. Below the secondary transfer unit 22 and the fixing unit 25 is a sheet reversal unit 28 that feeds out the paper immediately after an image has been formed on the front surface, inverting it to record an image on the back side as well.

[0011] When the start switch on the operation unit of the image forming apparatus is pressed, if there is a document on the document feed tray 30 of the automatic document feeder (ADF) 400, it is transported onto the contact glass 32. If there is no document in the ADF 400, the scanner of the image reading unit 300 is driven to read a manually placed document on the contact glass 32, and the first carriage 33 and the second carriage 34 are driven to read and scan. Light is emitted from the light source on the first carriage 33 onto the contact glass, and the reflected light from the document surface is reflected by the first mirror on the first carriage 33 and directed towards the second carriage 34, where it is reflected by the mirror on the second carriage 34 and formed on the CCD 36, which is a reading sensor, through the imaging lens 35. Based on the image signal obtained by the CCD 36, Y, M, C, and K color recording data are generated.

[0012] Furthermore, when the start switch is pressed, or when an image output instruction is received from a PC or other device, or when a fax output instruction is received, the rotation drive of the intermediate transfer belt 10 is started, and the preparation for image creation of each unit of the image creation device 20 is started. Then, the image creation sequence for each color is started, and an exposure laser modulated based on the recorded data of each color is projected onto the photoreceptor drum for each color, and through the image creation process for each color, the toner images of each color are superimposed and transferred onto the intermediate transfer belt 10 as a single image. The paper is fed into the secondary transfer unit 22 at a timing that coincides with the leading edge of this toner image entering the secondary transfer unit 22, thereby transferring the toner image on the intermediate transfer belt 10 to the paper. The paper with the transferred toner image is then sent to the fuser unit 25, where the toner image is fixed to the paper.

[0013] Note that for the above-mentioned paper, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotationally driven, a sheet is fed out from one of the paper feed trays 44 provided in multiple stages in the paper feed unit 43, separated by only one sheet by the separation roller 45, put into the conveyance roller unit 46, conveyed by the conveyance roller 47, and guided to the conveyance roller unit 48 in the printer 100. After hitting and stopping against the registration roller 49 of the conveyance roller unit 48, it is sent to the secondary transfer unit 22 at the aforementioned timing. It is also possible to insert the paper on the manual feed tray 51 for paper feeding. When the user inserts the paper on the manual feed tray 51, the printer 100 rotationally drives the paper feed roller 50 to separate one sheet of the sheet on the manual feed tray 51 and draw it into the manual paper feed path 53, and also hits and stops against the registration roller 49.

[0014] The paper that has undergone the fixing process by the fixing unit 25 and is discharged is guided to the discharge roller 56 by the switching claw 55 and stacked on the paper discharge tray 57. Or, it is guided to the sheet reversing unit 28 by the switching claw 55, reversed there, and guided back to the transfer position again. After recording an image on the back side as well, it is discharged onto the paper discharge tray 57 by the discharge roller 56. On the other hand, the residual toner remaining on the intermediate transfer belt 10 after image transfer is removed by the intermediate transfer body cleaning unit 17 in preparation for the next image formation.

[0015] FIG. 2 is a diagram for explaining an example of an image forming device included in the image forming apparatus according to the first embodiment. In the present embodiment, the image forming device 20 includes four sets of image forming units and four sets of light beam scanning devices 21 in order to form a color image in which four-color (yellow, magenta, cyan, black) images are overlapped.

[0016] The optical beam scanning device 21 (an example of an optical scanning device) will be described with reference to FIG. 3. An LD unit is provided that selectively emits an optical beam by being driven and modulated according to image data. The emitted optical beam is deflected by a polygon mirror rotated by a polygon motor, passes through an fθ lens, is reflected by a folding mirror, and scans the photosensitive drum. The optical beam scanning devices 21-1 and 21-2 (see FIG. 3), which are examples of an optical writing device that forms a latent image by scanning an optical beam corresponding to image data on the photosensitive drum with one LD unit, are arranged in a plurality in the main scanning direction. The plurality of optical beam scanning devices 21-1 and 21-2 form a latent image by irradiating optical beams to a plurality of regions (divided regions) divided by each of the optical beam scanning devices 21-1 and 21-2 on the photosensitive drum, where the scanning regions on the photosensitive drum are divided in the main scanning direction. Also, the plurality of optical beam scanning devices 21-1 and 21-2 scan different regions obtained by dividing the scanning region on the photosensitive drum in the main scanning direction in a direction away from each other.

[0017] For each color, around the photosensitive drum, there are provided a charger (charging unit 18), a developing unit that visualizes the latent image, a transferrer, a cleaning unit, and a discharger. By performing charging, exposure, development, and transfer, which are normal electrophotographic processes, an image of the first color is formed on the intermediate transfer belt 10. Next, by transferring images in the order of the second color, the third color, and the fourth color, a color image in which four-color images are superimposed is formed. Further, by transferring the image formed on the intermediate transfer belt 10 to the recording paper (paper) being conveyed by the secondary transfer unit 22, a color image in which four-color images are superimposed can be formed on the recording paper. Then, the image on the recording paper is fixed by the fixing unit 25. An intermediate transfer body cleaning unit 17 is provided to remove the toner image on the intermediate transfer belt 10.

[0018] A secondary transfer belt cleaning unit is provided to remove the toner image on the secondary transfer belt 24. Also, for each color, there is provided a toner bottle containing toner to be supplied to the developing unit.

[0019] Figure 3 is a top view of the light beam scanning device of the image forming apparatus according to the first embodiment. The light beam scanning device 21 has the same configuration for each color. For each color, two light beam scanning devices 21, light beam scanning device 21-1 and light beam scanning device 21-2, are installed side by side in the scanning direction. Light beam scanning devices 21-1 and 21-2 have the same configuration, and the light beam emitted from the LD unit passes through the CYL (cylinder lens), enters the polygon mirror, the polygon mirror rotates to deflect the light beam, passes through the fθ lens, and is scanned on the photoreceptor drum by the folding mirror.

[0020] The main scanning direction write-out end is equipped with a synchronization mirror, a synchronization lens, and a synchronization sensor. The light beam that passes through the fθ lens is reflected by the synchronization mirror, focused by the synchronization lens, and incident on the synchronization sensor. The synchronization sensor acts as a synchronization sensor for detecting a synchronization detection signal that determines the write-out timing of the main scan. In other words, the synchronization sensor is an example of a light detection sensor positioned near the starting position of the light scan in the main scanning direction. In this embodiment, the scanning directions of the light beam scanning device 21-1 and the light beam scanning device 21-2 are opposite to each other in the main scanning direction.

[0021] Figure 4 is a diagram illustrating an example of a light beam scanning device in an image forming apparatus according to the first embodiment. In this embodiment, the light beam scanning devices 21-1 and 21-2 include a write control unit 401, a light source lighting means 402, a light source 403, a deflector 404, and a synchronization sensor 405. The write control unit 401 determines the write timing in the main scanning direction and controls the light source lighting means 402 to light up the light source 403 according to the write timing. Here, the write timing is an example of the write timing at which the light beam scanning devices 21-1 and 21-2 start scanning light in the main scanning direction. The light source lighting means 402 is an example of a light source lighting means for lighting up the light source 403. The deflector 404 is an example of a deflector that scans the light from the light source 403 on a photoreceptor drum (an example of a photoreceptor) in the main scanning direction. The synchronization sensor 405 is positioned near the write start position (scan start position) in the main scanning direction on the photoreceptor drum (also called the leading edge in the main scanning direction, or near the main scanning start), detects the light from the light source 403, and outputs a synchronization detection signal XDETP.

[0022] Light emitted from the light source 403 is scanned horizontally by the deflector 404. When light is input to the synchronization sensor 405 at the leading end of the scanning direction (main scanning direction) of the photoreceptor drum, the synchronization sensor 405 outputs a synchronization detection signal XDETP, which is sent to the write control unit 401. The write control unit 401 determines the write timing in the main scanning direction according to the synchronization detection signal XDETP, controls the light source lighting means 402, and lights up the light source 403.

[0023] In other words, the write control unit 401 generates the write timing based on the synchronization detection signal XDETP generated by receiving light with the synchronization sensor 405. Then, it randomly changes the write timing of each of the multiple light beam scanning devices 21-1, 21-2 after a predetermined number of light scans in the main scanning direction. This makes it possible to make the black or white streaks at the seams of the scanning areas of the multiple light beam scanning devices 21-1, 21-2 less noticeable.

[0024] Figure 5 is a diagram illustrating an example of an optical beam scanning apparatus in an image forming apparatus according to the first embodiment. In this embodiment, the write control unit 401 controls the light source lighting means 402 by generating an LGATE signal that controls the start and end of writing the image in the main scanning direction after a predetermined number of write clocks from the synchronization detection signal XDETP.

[0025] Figure 6 is a diagram illustrating an example of dot arrangement drawn by two optical beam scanning devices in an image forming apparatus according to the first embodiment. Figure 7 is a diagram illustrating an example of black or white streaks occurring at the seams between the scanning areas of the two optical beam scanning devices. If the positional accuracy of the dots near the seams between the scanning areas of the two optical beam scanning devices 21-1 and 21-2 is high with each scan, the seam will appear as a white streak (see Figure 7) when the leading dots on the left and right are slightly separated, and as a black streak (see Figure 7) when the leading dots on the left and right are slightly closer together, making the seam noticeable.

[0026] Figure 8 is a diagram illustrating an example of a light beam scanning device in an image forming apparatus according to the first embodiment. Figure 9 is a diagram illustrating an example of a timing chart of an LGATE signal in which jitter is superimposed on the assert timing (image writing start timing) in an image forming apparatus according to the first embodiment. In this embodiment, when the write control unit 401 generates the LGATE signal from the synchronization detection signal XDETP, it introduces jitter into the assert timing of LGATE based on the input from the jitter generation unit 401b. Normally, the assert timing of the LGATE signal is always generated at a fixed timing based on the timing of the synchronization detection signal XDETP.

[0027] On the other hand, in this embodiment, the write control unit 401 inputs the synchronization detection signal XDETP to the random number generator 401a, and the LGATE generation unit 401c changes the assertion timing of the LGATE signal based on the input from the jitter generation unit 401b according to the value of the random number generated by the random number generator 401a. That is, the random number generator 401a is an example of a random number generation unit that generates random numbers based on the timing of the synchronization detection signal XDETP. The jitter generation unit 401b is an example of a jitter generation unit that generates jitter according to the random number. The LGATE generation unit 401c is an example of a generation unit that changes the write timing according to the jitter. As a result, the write control unit 401 randomly changes the write timing of each of the multiple optical beam scanning devices 21-1 and 21-2 for each scan of light in the main scanning direction.

[0028] Figure 10 is a diagram illustrating an example of dot arrangement when jitter is applied to the write timing in an image forming apparatus according to the first embodiment. In this embodiment, the write control unit 401 randomly applies jitter to the write timing of the dot at the write start position at the joints of the scanning areas of the left and right units (two optical beam scanning devices 21-1, 21-2). As a result, the distance between dots at the joints of the scanning areas of the left and right units changes randomly, so the density is dispersed compared to when the distance between dots is stable, making it less likely for white or black streaks to occur.

[0029] The write control unit 401 changes the assertion timing of the LGATE signal by setting the random numbers generated by the random number generator 401a to 0 to F (hex) and the jitter to -8 / 8 to +7 / 8, as shown in Table 1 below. [Table 1]

[0030] Thus, according to the image forming apparatus of the first embodiment, black and white streaks at the seams of the scanning areas of the multiple optical beam scanning devices 21-1 and 21-2 can be made less noticeable. In this embodiment, correction is applied by adding jitter to each line, but jitter may also be applied to every predetermined number of lines, such as every two lines, or even if applied to each line, the amount of jitter applied to each predetermined number of lines may be changed.

[0031] (Second Embodiment) This embodiment is an example in which the density of an image is determined based on the pixel count results at the seams of the scanning areas of multiple optical beam scanning devices, jitter is generated according to the density, and the writing timing is changed according to the jitter. In the following description, the same configuration as in the first embodiment will be omitted from the explanation.

[0032] Figure 11 illustrates an example of changing the amount of jitter according to image data in an image forming apparatus according to the second embodiment. The black and white streaks at the seams of the scanning areas of the optical beam scanning devices 21-1 and 21-2 are not easily visible in solid images, but become noticeable in the case of light halftones. Therefore, the write control unit 401 may adjust the jitter according to the density (shade) of the image data, as shown in Figure 11.

[0033] Figures 12 and 13 illustrate an example of a hardware configuration for determining the density of image data in an image forming apparatus according to the second embodiment. In this embodiment, the write control unit 401 calculates the dot density at the center of the input image data using a pixel counting unit 401d. That is, the pixel counting unit 401d is an example of a pixel counting unit that counts pixels at the seams of the scanning areas of the optical beam scanning devices 21-1 and 21-2.

[0034] The image data discrimination unit 401e calculates a dot density parameter by superimposing the presence or absence of dots and the gradation. In other words, the image data discrimination unit 401e is an example of an image data discrimination unit that determines the density of an image based on the pixel count result by the pixel count unit 401d. The jitter generation unit 401b generates jitter according to the density determined by the image data discrimination unit 401e. This adjusts the jitter according to the image, for example, by not adding jitter when there is no image data near the seam, reducing the amount of jitter for halftones that are close to solid as the seam lines are less visible to the naked eye, and increasing the amount of jitter for light halftones as the seam lines are more visible to the naked eye. As a result, it is possible to optimize image quality and side effects (vertical line distortion).

[0035] For example, as shown in Figure 13, the connection point between the scanning areas of the two optical beam scanning devices 21-1 and 21-2 is defined as a total of four dots, consisting of two dots at the scanning start point of the left and right units (the two optical beam scanning devices 21-1 and 21-2). The grayscale of all four pixels in the area indicated by (1) is set to 12 / 16, all four pixels in the area indicated by (2) are set to no dots, and all four pixels in the area indicated by (3) are set to 4 / 16. The image data discrimination unit 401e then calculates the dot density of each of the areas indicated by (1) to (3) as shown below. (1) The dot density of the part shown = 12 / 16 * 4 = 3 (2) The dot density of the part shown = 0 * 4 = 0 (3) The dot density of the part shown = 4 / 16 * 4 = 1

[0036] Then, the image data discrimination unit 401e determines the image density according to the calculated dot density, in accordance with the following conditions. Dot density = 0: No dots 0 < Dot density ≤ 2: Low density 2 <Dot density: High density>

[0037] If the dot density in the relevant area is high, as shown in (1), the jitter generation unit 401b restricts the random numbers and superimposes jitter in the range of -4 / 8 to 4 / 8 dots. If there are no dots in the relevant area, as shown in (2), the jitter generation unit 401b is uncorrected. If the dot density in the relevant area is low, as shown in (3), the jitter generation unit 401b superimposes jitter in the range of -8 / 8 to 7 / 8 dots without restricting the random numbers. In other words, if the calculated density is higher than a preset density, the jitter generation unit 401b may generate jitter by restricting the random numbers, and if the calculated density is less than or equal to a preset density, it may generate jitter without restricting the random numbers. [Table 2]

[0038] The dot density calculation formula, random number resolution, and correction threshold shown above are merely examples. In this embodiment, the image data discrimination unit 401e may determine the density for each scan in the main scanning direction. In that case, the jitter generation unit 401b generates jitter for each scan in the main scanning direction. This enables optimal correction for the entire image.

[0039] Figure 14 is a diagram illustrating an example of a process for determining the dot density at the seams on a page-by-page basis in an image forming apparatus according to the second embodiment. In this embodiment, the pixel counting unit 401d counts the dots at the seams of the printed pages (the translucent areas shown in Figure 14), and adds jitter on a page-by-page basis according to the count value. That is, the image data discrimination unit 401e determines the density for each page of the image data. In this case, the jitter generation unit 401b generates jitter for each page. Although the effect is smaller than measuring and adding jitter for each scan in the main scanning direction, there is an advantage in that the density discrimination and jitter addition processes are lighter.

[0040] Thus, according to the image forming apparatus of the second embodiment, jitter can be adjusted according to the image, making it possible to optimize image quality and side effects (vertical line distortion).

[0041] Examples of the present invention are as follows: <1> Photoreceptor and The optical scanning device comprises a light source, a light source illuminating means for illuminating the light source, a deflector for scanning the light from the light source illuminated by the light source illuminating means on the photoreceptor in the main scanning direction, a light detection sensor positioned near the starting position of light scanning in the main scanning direction, and a write control unit that determines a write timing to start scanning the light in the main scanning direction and controls the light source illuminating means according to that write timing. Multiple optical scanning devices divide the scanning area on the photoreceptor in the main scanning direction, and scan the different regions divided from the scanning area in directions away from each other. The write control unit generates the write timing based on the synchronization detection signal generated by receiving light with the light detection sensor. The writing timing of each of the plurality of optical scanning devices varies randomly every predetermined number of light scans in the main scanning direction. <2> The write control unit, A random number generator that generates random numbers based on the timing of the synchronization detection signal, A jitter generation unit that generates jitter according to the aforementioned random number, A generation unit that changes the writing timing according to the jitter, Equipped with <1> The optical scanning device described above. <3> The write control unit, A pixel counting unit that counts pixels at the seams of scanning areas of multiple optical scanning devices, An image data discrimination unit that determines the density of an image based on the pixel count result by the pixel count unit, A jitter generating unit that generates jitter according to the concentration, A generation unit that changes the writing timing according to the jitter, Equipped with <2> The optical scanning device described above. <4> The image data discrimination unit determines the density for each scan in the main scanning direction, The jitter generating unit generates jitter with each scan in the main scanning direction. <3> The optical scanning device described above. <5> The image data discrimination unit determines the density for each page of the image data, The jitter generating unit generates jitter for each page. <3> The optical scanning device described above. <6> The jitter generating unit generates jitter by restricting the random numbers when the concentration is higher than a preset concentration, and generates jitter without restricting the random numbers when the concentration is less than or equal to the preset concentration. <3> from <5> An optical scanning device as described in any one of the following. [Explanation of Symbols]

[0042] 21-1, 21-2 Optical beam scanning device 401 Write Control Unit 401a Random Number Generator 401b Jitter generation section 401c LGATE generation part 401d Pixel Counting Unit 401e Image Data Discrimination Unit 402 Light source lighting means 403 Light source 404 Deflector 405 Synchronization Sensor [Prior art documents] [Patent Documents]

[0043] [Patent Document 1] Japanese Patent Application Publication No. 11-095152

Claims

1. Photoreceptor and The optical scanning device comprises a plurality of optical scanning devices, each including a light source, a light source illuminating means for illuminating the light source, a deflector for scanning the light from the light source illuminated by the light source illuminating means on the photoreceptor in the main scanning direction, a light detection sensor positioned near the starting position of the light scanning in the main scanning direction, and a write control unit that determines the write timing for starting the scanning of light in the main scanning direction and controls the light source illuminating means according to the write timing. Multiple optical scanning devices divide the scanning area on the photoreceptor in the main scanning direction, and scan the different regions divided from the scanning area in directions away from each other. The write control unit generates the write timing based on the synchronization detection signal generated by receiving light with the light detection sensor. The writing timing of each of the plurality of optical scanning devices varies randomly every predetermined number of light scans in the main scanning direction.

2. The write control unit, A random number generator that generates random numbers based on the timing of the synchronization detection signal, A jitter generation unit that generates jitter according to the aforementioned random number, A generation unit that changes the writing timing according to the jitter, The optical scanning apparatus according to claim 1, comprising:

3. The write control unit, A pixel counting unit that counts pixels at the seams of scanning areas of multiple optical scanning devices, An image data discrimination unit that determines the density of an image based on the pixel count result by the pixel count unit, A jitter generating unit that generates jitter according to the concentration, A generation unit that changes the writing timing according to the jitter, The optical scanning apparatus according to claim 2, comprising:

4. The image data discrimination unit determines the density for each scan in the main scanning direction, The optical scanning apparatus according to claim 3, wherein the jitter generating unit generates jitter for each scan in the main scanning direction.

5. The image data discrimination unit determines the density for each page of the image data, The optical scanning apparatus according to claim 3, wherein the jitter generating unit generates jitter for each page.

6. The optical scanning apparatus according to claim 3, wherein the jitter generating unit generates jitter by restricting the random numbers when the concentration is higher than a preset concentration, and generates jitter without restricting the random numbers when the concentration is less than or equal to the preset concentration.

Images