Writing device and writing method

Abstract

To provide a writing device and a writing method capable of shifting an image position in a main scanning direction in a state where the image position in the main scanning direction of a boundary part of an area irradiated with a light beam by each of two optical scanners is aligned.SOLUTION: A plurality of optical writing means for forming a latent image by irradiating an image carrier with a light beam corresponding to image data are installed side by side in a scanning direction, and the image carrier is divided into a plurality of areas in a main scanning direction. At least one of an area width in which a boundary portion between the areas can be irradiated with the light beam by both of the two adjacent optical writing units and a data amount included in both of the two adjacent optical writing units among the divided image data is secured to be equal to or larger than an adjustment amount of an image position in a main scanning direction.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a writing device and a writing method. [Background technology]

[0002] This is an image forming device (an example of a writing device) that forms an image by irradiating an image carrier with image light corresponding to image data, making the latent image visible using a developing means, and transferring the visualized image onto recording paper.A technology has been devised in which optical scanning devices that irradiate the image carrier with image light corresponding to image data, two per color, are arranged in the scanning direction, and the images are joined together on the image carrier, thereby widening the image width and improving printing speed.

[0003] For example, Patent Document 1 discloses a configuration in which, when optically scanning multiple areas in the main scanning direction using multiple deflection devices that rotate asynchronously, divided image data is delayed based on the results of comparing the scanning timing between adjacent optical scanning devices in order to correct misalignment in the sub-scanning direction between multiple image areas. Summary of the Invention [Problem to be solved by the invention]

[0004] However, in an image forming apparatus using two optical scanning devices per color, when adjusting the image position by stitching together the divided image data on an image carrier such as a photosensitive body, if there is insufficient overlap width of the light beams near the boundary between the areas irradiated with the light beams by each of the two optical scanning devices, or if there is not enough overlapping data for each of the divided image data, it is difficult to shift the image position in the main scanning direction.

[0005] The present invention has been made in consideration of the above, and aims to provide a writing device and a writing method that can shift the image position in the main scanning direction while aligning the image position in the main scanning direction of the boundary part of the area irradiated with the light beam by each of two optical scanning devices. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the present invention provides an optical writing device in which a plurality of optical writing means are arranged in the scanning direction, each of which forms a latent image by irradiating a light beam corresponding to image data onto an image carrier using one scanning means, and the scanning area on the image carrier is divided into a plurality of areas in the main scanning direction, and each of the optical writing means irradiates a light beam onto each of the plurality of areas to form a latent image, a toner developing means for visualizing the latent image, a transfer means for transferring the visualized toner image onto recording paper, and a dividing means for dividing the image data for each of the optical writing means, and at least one of the area width over which the light beam can be irradiated onto the boundary between the plurality of areas by both of the two adjacent optical writing means and the data amount of the divided image data contained in both of the two adjacent optical writing means is ensured to be equal to or greater than the adjustment amount of the image position in the main scanning direction. [Effects of the Invention]

[0007] According to the present invention, it is possible to shift the image positions in the main scanning direction while aligning the image positions in the main scanning direction of the boundary portions of the regions irradiated with light beams by the two optical scanning devices. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating an example of an image forming apparatus according to the present embodiment. [Figure 2] FIG. 2 is a diagram for explaining an example of an image forming device included in the image forming apparatus according to the present embodiment. [Figure 3] FIG. 3 is a top view of the light beam scanning device included in the image forming apparatus according to this embodiment. [Figure 4] FIG. 4 is a diagram for explaining an example of an image formation control unit and a light beam scanning device included in the image forming apparatus according to the present embodiment. [Figure 5]FIG. 5 is a diagram illustrating an example of a writing start position control unit included in the image forming apparatus according to the present embodiment. [Figure 6] FIG. 6 is a diagram for explaining an example of a timing chart of the writing start position control unit in the main scanning direction in the image forming apparatus according to the present embodiment. [Figure 7] FIG. 7 is a diagram for explaining an example of a timing chart of the writing start position control unit in the sub-scanning direction in the image forming apparatus according to the present embodiment. [Figure 8] FIG. 8 is a diagram illustrating an example of an image data dividing unit included in the image forming apparatus according to the present embodiment. [Figure 9] FIG. 9 is a diagram for explaining an example of a printer control unit of the image forming apparatus according to the present embodiment. [Figure 10] FIG. 10 is a diagram for explaining an example of the flow of control processing during printing by the image forming apparatus according to the present embodiment. [Figure 11] FIG. 11 is a diagram for explaining an example of the image position correction process in the image forming apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of a writing device and a writing method will be described in detail with reference to the accompanying drawings.

[0010] FIG. 1 is a diagram illustrating an example of an image forming apparatus according to the present embodiment. A printer 100, which is an image forming apparatus (an example of a writing device) according to the present embodiment, has an intermediate transfer unit at its center, which includes an intermediate transfer belt 10, which is an endless belt. The intermediate transfer belt 10 is wound around three support rollers 14-16 and rotates clockwise. To the right of the second support roller 15, there is an intermediate transfer body cleaning unit 17, which removes residual toner remaining on the intermediate transfer belt 10 after image transfer. Between the first support roller 14 and the second support roller 15, the intermediate transfer belt 10 includes an image forming device 20, which includes photosensitive units 40 for each of the colors yellow (Y), magenta (M), cyan (C), and black (K), a charging unit 18, a developing unit, and a cleaning unit, along its moving direction. The image forming device 20 is detachably attached to the printer 10 body.

[0011] Above the image forming device 20 is a light beam scanning device 21 that irradiates each photosensitive drum of each color photosensitive unit with a laser beam for image formation. Below the intermediate transfer belt 10 is a secondary transfer unit 22. The secondary transfer unit 22 is configured by stretching an endless secondary transfer belt 24 between two rollers 23, pushing the intermediate transfer belt 10 up and against a third support roller 16. This secondary transfer belt 24 transfers the image on the intermediate transfer belt 10 onto paper. Next to the secondary transfer unit 22 is a fixing unit 25 that fixes the transferred image on the paper, and paper with a transferred toner image is fed into it. The fixing unit 25 uses an endless fixing belt 26 and a heating and pressure roller 27 to melt the toner image transferred onto the paper and fix it to the paper by pressing it. Below the secondary transfer unit 22 and the fixing unit 25, there is a sheet inverting unit 28 that inverts the paper immediately after an image has been formed on its front side and sends it out so that an image can also be recorded on its back side.

[0012] When a start switch on the operation unit of the image forming apparatus is pressed, if there is an original 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 original on the ADF 400, the scanner of the image reading unit 300 is driven to read and scan the first carriage 33 and the second carriage 34 in order to read the original placed manually on the contact glass 32. Then, light is emitted from a light source on the first carriage 33 onto the contact glass, and reflected light from the document surface is reflected by a first mirror on the first carriage 33 and directed towards the second carriage 34, and then reflected by a mirror on the second carriage 34 to form an image on the reading sensor CCD 36 through an imaging lens 35. Recording data for each of the colors Y, M, C, and K is generated based on the image signal obtained by the reading sensor 36.

[0013] Furthermore, when a start switch is pressed, an image output instruction is received from a personal computer or the like, or a fax output instruction is received, rotational driving of the intermediate transfer belt 10 begins, and each unit of the image forming device 20 begins preparation for image formation. Then, the image formation sequence for each color begins, and an exposure laser modulated based on the corresponding color recording data is projected onto the photosensitive drum for each color. Through each color image formation process, toner images of each color are transferred onto the intermediate transfer belt 10 in a superimposed manner as a single image. A sheet of paper is fed into the secondary transfer unit 22 at a timing that allows the leading edge of the toner image to simultaneously enter the secondary transfer unit 22, thereby transferring the toner image on the intermediate transfer belt 10 to the paper. In other words, the secondary transfer unit 22 is an example of a transfer means that transfers the image visualized by the developing unit onto the secondary transfer belt 24 (an example of a belt). The paper with the toner image transferred thereto is fed into the fixing unit 25, where the toner image is fixed to the paper.

[0014] The above-mentioned paper is fed by selectively rotating one of paper feed rollers 42 of paper feed table 200, feeding a sheet from one of paper feed trays 44 provided in multiple stages in paper feed unit 43, separating only one sheet by separation roller 45, placing it in transport roller unit 46, transporting it by transport roller 47, and leading it to transport roller unit 48 in printer 100, where it hits and stops against registration roller 49 of transport roller unit 48, and then being sent to secondary transfer unit 22 at the timing mentioned above. Paper can also be fed by inserting it into manual feed tray 51. When a user has inserted paper into manual feed tray 51, printer 100 rotates paper feed roller 50 to separate one sheet from the manual feed tray 51, pull it into manual feed path 53, and similarly hits and stops against registration roller 49.

[0015] After being fixed by the fixing unit 25 and discharged, the paper is guided by the switching claw 55 to the discharge rollers 56 and stacked on the paper discharge tray 57. Alternatively, the paper is guided by the switching claw 55 to the sheet reversing unit 28, where it is reversed and led back to the transfer position, and after an image is recorded on the back side, it is discharged by the discharge rollers 56 onto the paper discharge tray 57. Meanwhile, any residual toner remaining on the intermediate transfer belt 10 after the image transfer is removed by the intermediate transfer body cleaning unit 17 in preparation for next image formation.

[0016] 2 is a diagram illustrating an example of an imaging device included in an image forming apparatus according to this embodiment. In this embodiment, the imaging device 20 includes four sets of image forming units and four sets of light beam scanning devices 21 to form a color image by superimposing images of four colors (yellow, magenta, cyan, and black).

[0017] The light beam scanning device 21 (an example of a light beam scanning device) will be described with reference to Figure 3. It includes an LD unit that selectively emits a light beam by being driven and modulated in accordance with image data. The emitted light 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 a photosensitive drum. The light beam scanning device 21 includes a plurality of light beam scanning devices 21-1 and 21-2 (see Figure 3), which are examples of optical writing means that form latent images by scanning a photosensitive drum (an example of an image carrier) with a light beam according to image data using one LD unit (an example of a scanning means). The light beam scanning device 21 divides a scanning area on the photosensitive drum in the main scanning direction, and forms a latent image by irradiating each of the divided areas (divided areas) with a light beam.

[0018] For each color, a charger (charging unit 18), a development unit (an example of a toner developing means) that visualizes the latent image, a transfer unit, a cleaning unit, and a static eliminator are provided around the photosensitive drum. A first-color image is formed on intermediate transfer belt 10 through the typical electrophotographic process of charging, exposing, developing, and transferring. Images of the second, third, and fourth colors are then transferred in this order to form a color image in which four color images are superimposed. The image formed on intermediate transfer belt 10 is then transferred to conveyed recording paper (paper) by secondary transfer unit 22, forming a color image in which four color images are superimposed on the recording paper. The image on the recording paper is then fixed by fixing unit 25. An intermediate transfer belt cleaning unit 17 is provided to remove the toner image on intermediate transfer belt 10.

[0019] A secondary transfer belt cleaning unit is provided to remove the toner image on the secondary transfer belt 24. Also, a toner bottle containing toner to be replenished to the developing unit is provided for each color.

[0020] 3 is a top view of the light beam scanning device included in the image forming apparatus according to this embodiment. The light beam scanning device 21 has the same configuration for each color. The light beam scanning device 21 for each color is configured with two light beam scanning devices 21-1 and 21-2, which are arranged side by side in the scanning direction. The light beam scanning device 21-1 and the light beam scanning device 21-2 have the same configuration, and the light beam emitted from the LD unit passes through a CYL (cylinder lens) and enters a polygon mirror. The polygon mirror rotates to deflect the light beam, passes through an fθ lens, and scans the photosensitive drum with a folding mirror.

[0021] A synchronization mirror, a synchronization lens, and a synchronization sensor are provided at the writing start end in the main scanning direction, and the light beam that passes through the fθ lens is reflected by the synchronization mirror, concentrated by the synchronization lens, and incident on the synchronization sensor, which serves as a synchronization sensor for detecting a synchronization detection signal that determines the writing timing of the main scanning. In this embodiment, the image forming apparatus divides image data into multiple (for example, two) pieces of image data, sends each of the divided pieces of image data (divided image data) to light beam scanning device 21-1 and light beam scanning device 21-2, and scans (irradiates) the light beam so that the latent images formed by each of the light beam scanning devices 21-1 and 21-2 are joined together on the photosensitive drum.

[0022] Furthermore, in this embodiment, the image forming apparatus has an area (overlapping area) A near the center of the photosensitive drum that can be scanned by both the light beam scanning device 21-1 and the light beam scanning device 21-2. That is, in this embodiment, the image forming apparatus has an overlapping area (an example of area width) A where the boundary between the two divided areas can be irradiated with light beams by the two adjacent light beam scanning devices 21-1 and 21-2. In other words, a portion of the divided image data can be irradiated with light beams from both the two adjacent light beam scanning devices 21-1 and 21-2.

[0023] Fig. 4 is a diagram for explaining an example of an image formation control unit and a light beam scanning device included in an image forming apparatus according to this embodiment. Fig. 4 shows the control unit of the light beam scanning device 21-1, but the light beam scanning device 21-2 has the same configuration except for the printer control unit 407 and the storage unit 409 (correction data storage unit). The light beam scanning devices 21 for each color also have the same configuration.

[0024] A synchronous sensor for detecting a light beam is provided on the image writing end of the optical beam scanning device 21-1 in the main scanning direction. The optical beam that passes through the fθ lens is reflected by a synchronous mirror and focused by a synchronous lens before entering the synchronous sensor. When the optical beam passes over the synchronous sensor, a synchronous detection signal XDETP is output from the synchronous sensor and sent to a pixel clock generation unit 1 (401), a synchronous detection lighting control unit 1 (402), and a writing start position control unit 1 (404). The pixel clock generation unit 1 (401) generates a pixel clock PCLK synchronized with the synchronous detection signal XDETP and sends it to a writing start position control unit 1 (404), a synchronous detection lighting control unit 1 (402), and a LD control unit 1 (405).

[0025] The synchronous detection lighting control unit 1 (402) first turns on the LD forced lighting signal BD to forcibly light the LD in order to detect the synchronous detection signal XDETP, but after detecting the synchronous detection signal XDETP, it uses the synchronous detection signal XDETP and the pixel clock PCLK to light the LD at a timing that ensures that the synchronous detection signal XDETP is detected without generating flare light, and generates an LD forced lighting signal BD that turns off the LD when the synchronous detection signal XDETP is detected, and sends this to the LD control unit 1 (405). It also generates a light intensity control timing signal APC for each LD using the synchronous detection signal XDETP and the pixel clock PCLK, and sends this to the LD control unit 1 (405). This signal must be executed outside the image writing area, and the light intensity is controlled to a target light intensity at that timing.

[0026] The LD control unit 1 (405) controls the lighting of the LD in accordance with the synchronous detection forced lighting signal BD, the light amount control timing signal APC, and image data synchronized with the pixel clock PCLK. Then, a laser beam is emitted from the LD, deflected by the polygon mirror, passes through the fθ lens, and is scanned onto the photosensitive drum by the folding mirror.

[0027] The polygon motor control unit 1 (406) controls the polygon motor to rotate at a specified number of revolutions based on a control signal from the printer control unit 407. The writing start position control unit 1 (404) generates a main scanning control signal XLGATE and a sub scanning control signal XFGATE that determine the image writing start timing and image width based on the synchronization detection signal XDETP, the pixel clock PCLK, and control signals from the printer control unit 407.

[0028] When performing an image forming operation, the correction data stored in the memory unit 409 is read out by instruction from the printer control unit 407, and the correction data is set in the write start position control unit 1 (404) and the pixel clock generation unit 1 (401).

[0029] 5 is a diagram illustrating an example of a write start position control unit included in the image forming apparatus according to this embodiment. The write start position control unit 1 (404) is divided into a main-scan line synchronization signal generating unit 501, a main-scan gate signal generating unit 502, and a sub-scan gate signal generating unit 503. The main-scan line synchronization signal generating unit 501 generates a signal XLSYNC for operating a main-scan counter 502a in the main-scan gate signal generating unit 502 and a sub-scan counter 503a in the sub-scan gate signal generating unit 503. The main-scan gate signal generating unit 502 generates a signal XLGATE that determines the timing of image signal capture (image write start timing in the main-scan direction). The sub-scan gate signal generating unit 503 generates a signal XFGATE that determines the timing of image signal capture (image write start timing in the sub-scan direction).

[0030] The main scanning gate signal generating unit 502 has a main scanning counter 502a that operates on XLSYNC and PCLK, a comparator 502b that compares the counter value of the main scanning counter 502a with a setting value 1 (correction data) from the printer control unit 407 and outputs the result, and a gate signal generating unit 502c that generates XLGATE from the comparison result from the comparator 502b.

[0031] The sub-scanning gate signal generating unit 503 has a sub-scanning counter 503a that operates with a print start signal from the printer control unit 407, XLSYNC, and PCLK, a comparator 503b that compares the counter value of the sub-scanning counter 503a with a setting value 2 (correction data) from the printer control unit 407 and outputs the result, and a gate signal generating unit 503c that generates XFGATE from the comparison result from the comparator 503b.

[0032] The write start position control unit 1 (404) can correct the write start position in units of one cycle of the clock PCLK for main scanning, i.e., in units of one dot, and in units of one cycle of the XLSYNC for sub-scanning, i.e., in units of one line. Correction data for both main scanning and sub-scanning is stored in a storage unit 409.

[0033] 6 is a diagram illustrating an example of a timing chart of the write start position control unit in the main scanning direction in the image forming apparatus according to this embodiment. In the write start position control unit 1 (404), the main scanning counter 502a is reset by XLSYNC, and the main scanning counter 502a counts up by PCLK. When the counter value of the main scanning counter 502a reaches the set value 1 (X in this case) set by the printer control unit 407, the comparator 502b outputs the comparison result, and the main scanning gate signal generation unit 502 sets XLGATE to low level (enabled). XLGATE is a signal that remains low for the width of the image in the main scanning direction.

[0034] 7 is a diagram illustrating an example of a timing chart of the writing start position control unit in the sub-scanning direction in the image forming apparatus according to this embodiment. The writing start position control unit 1 (404) resets the sub-scanning counter 503a in response to a print start signal from the printer control unit 407, and counts up the sub-scanning counter 503a with XLSYNC. When the counter value reaches the set value 2 (Y in this case) set by the printer control unit 407, the comparator 503b outputs the comparison result, and the sub-scanning gate signal generation unit 503 sets XFGATE to low level (enabled). XFGATE is a signal that remains low for the length of the image in the sub-scanning direction.

[0035] FIG. 8 is a diagram illustrating an example of an image data dividing unit included in the image forming apparatus according to this embodiment. As shown in FIG. 8, the printer control unit 407 of the image forming apparatus according to this embodiment includes a dividing unit 407a, an image writing control unit 1 (407b), and an image writing control unit 2 (407c). Image data is input to the dividing unit 407a from a printer controller, a frame memory, a scanner, etc. The dividing unit 407a divides the input image data into two lines and sends them to the image writing control unit 1 (407b) and the image writing control unit 2 (407c). In other words, the dividing unit 407a is an example of a dividing means for dividing image data for each of the optical beam scanning devices 21-1 and 21-2. The dividing unit 407a, the image writing control unit 1 (407b), and the image writing control unit 2 (407c) function as line memories.

[0036] For example, if the number of image data near the boundary between the area (divided area) irradiated with the light beam by the light beam scanning device 21-1 and the area (divided area) irradiated with the light beam by the light beam scanning device 21-2 in the main scanning direction is 100, the number of image data for one line is 2000, and the image data is D1 to D2000, the dividing unit 407a divides the input one-line image data D1 to D2000 for each of the light beam scanning devices 21-1 and 21-2. In other words, the dividing unit 407a functions as an example of a dividing means that divides image data for each of the light beam scanning devices 21-1 and 21-2. Next, the dividing unit 407a sends the image data D1 to D1050 to the image writing control unit 1 (407b) and sends the divided image data D950 to D2000 to the image writing control unit 2 (407c).

[0037] As a result, image data D950 to D1050 near the boundary between the areas irradiated by the light beams of the light beam scanning device 21-1 and the light beam scanning device 21-2 is sent to both image writing control units 1 and 2 (407b and 407c). That is, the dividing unit 407a ensures that either of the divided image data (divided image data) included in both of the two adjacent light beam scanning devices 21-1 and 21-2 has an amount equal to or greater than the amount of image position adjustment in the main scanning direction. In this case, the image writing control units 1 and 2 (407b and 407c) may store the divided image data in memory and adjust the image data read from the memory. Alternatively, the image forming apparatus ensures that an overlapping area A, where the photosensitive drum can be irradiated with the light beams of both adjacent light beam scanning devices 21-1 and 21-2, has an amount equal to or greater than the amount of image position adjustment in the main scanning direction.

[0038] That is, at least one of the overlapping area A where the two adjacent light beam scanning devices 21-1, 21-2 can irradiate the light beam onto the boundary of the multiple divided areas, and the amount of data contained in the two adjacent light beam scanning devices 21-1, 21-2 of the divided image data is ensured to be equal to or greater than the adjustment amount of the image position in the main scanning direction.

[0039] Image writing control unit 1 (407b) and image writing control unit 2 (407c) send the divided image data taken in from the printer controller, frame memory, scanner, etc. to LD control unit 1 (405) and LD control unit 2 (405) in synchronization with PCLK at the timing of XFGATE and XLGATE, and at that timing each LD turns on, irradiates a light beam onto the photosensitive drum, and writes the divided image data onto the photosensitive drum. In this way, by determining the timing and address to read from the line memory in which the image data is stored, the required image data can be sent to LD control units 1 and 2 (405) at the required timing.

[0040] 9 is a diagram illustrating an example of a printer control unit of an image forming apparatus according to this embodiment. The printer control unit 407 includes a CPU, RAM, ROM, and I / O ports, and each piece of hardware is connected via a bus. The CPU is a device that executes programs that control the operation of the image forming apparatus and performs predetermined processing. The RAM is a volatile storage device that provides an execution space for the programs executed by the CPU, and is used for storing and expanding programs and data. The ROM is a non-volatile storage device that stores programs executed by the CPU, firmware, etc. The I / O ports are devices that process output information to motors controlled by the CPU, input information from various sensors, etc.

[0041] The writing start position control units 1 and 2 (404), LD control units 1 and 2 (405), synchronous detection lighting control units 1 and 2 (402), pixel clock generation units 1 and 2 (401), polygon motor control units 1 and 2 (406), and HDD (storage unit 409) are also connected via the bus, and various data settings, ON / OFF control, data saving and reading, etc. are performed according to instructions from the CPU.

[0042] 10 is a diagram illustrating an example of the flow of control processing during printing by the image forming apparatus according to this embodiment. When the start key on the operation panel is pressed, printer control unit 407 first rotates the polygon motor at a specified rotation speed (step S1001). Then, printer control unit 407 sets correction data (setting values ​​for the write start positions in the main scanning direction and sub-scanning direction and the magnification) in each control unit (step S1002), turns on the LDs to output a synchronization detection signal, and performs APC operation to light each LD at a specified light intensity (step S1003). Thereafter, printer control unit 407 starts image formation (step S1004). If there is no next image (step S1005: No), it turns off each LD (step S1006) and stops the polygon motor (step S1007), and then ends the operation.

[0043] FIG. 11 is a diagram illustrating an example of image position correction processing in the image forming apparatus according to the present embodiment. FIG. 11(a) illustrates a state in which the center of the image in the main scanning direction (the center of the photosensitive drum) is the boundary between two light beam scanning devices 21-1 and 21-2, and image data D1 to D2000 are joined together on the photosensitive drum. FIG. 11(b) illustrates a method for shifting the image in the main scanning direction by two dots relative to FIG. 11(a). The write start position control units 1 and 2 (404) delay the timing of XLGATE1 and XLGATE2, which determine the image write start timing and image width in the main scanning direction, by two dots, thereby shifting the entire image by two dots in the main scanning direction while maintaining the joined state of image data D1 to D2000 on the photosensitive drum. In other words, the write start position control units 1 and 2 (404) function as an example of a change unit for changing the image write start timing (an example of a write start timing) when adjusting the image position in the main scanning direction. This makes it possible to reliably change the image position in the main scanning direction.

[0044] 11(a) and 11(b), in the vicinity of the boundary of the divided areas irradiated with light beams by each of the two light beam scanning devices 21-1 and 21-2, it is necessary to be able to scan at least an area corresponding to the adjustment amount of shift in the main scanning direction, like the overlapping area A shown in Fig. 3. It can be seen that the area scanned by the light beam scanning device 21-2 in Fig. 11(a) is scanned by the light beam scanning device 21-1 in Fig. 11(b).

[0045] FIG. 11(c) shows a method for shifting the image by two dots in the main scanning direction compared to the method shown in FIG. 11(a), but differs from the method shown in FIG. 11(b). The write start position control unit 1 (404) delays XLGATE1, a signal that determines the image write start timing and image width in the main scanning direction, by two dots and also shortens the image width by two dots. Then, the write start position control unit 2 (404) does not change the image write start timing for XLGATE2, but shifts the output image data forward by two dots to lengthen the image width by two dots. This allows the entire image to be shifted by two dots in the main scanning direction while maintaining the connection of image data D1 to D2000 on the photosensitive drum. In other words, the write start position control units 1 and 2 (404) may change the image write start timing and image width when adjusting the image position in the main scanning direction. This ensures that the image position in the main scanning direction can be reliably changed.

[0046] In the method shown in Fig. 11(c), when dividing image data near the boundary between the two light beam scanning devices 21-1 and 21-2, it is necessary to overlap the divided image data for at least the number of dots corresponding to the amount of shift in the main scanning direction, as shown in Fig. 8. It can be seen that the image data written by the light beam scanning device 21-1 in Fig. 11(a) is written by the light beam scanning device 21-2 in Fig. 11(c). This embodiment can be applied not only to color image forming devices but also to single-color monochrome image forming devices.

[0047] As described above, according to the image forming apparatus of this embodiment, in an image forming apparatus in which two light beam scanning devices 21-1, 21-2 per color are arranged in the scanning direction, when the divided image data is spliced ​​on the photosensitive drum to adjust the image position, by providing a sufficient overlap width of the light beams near the boundary between the two light beam scanning devices 21-1, 21-2, or by providing sufficient overlapping data for each of the divided image data, it is possible to shift the image position in the main scanning direction while aligning the image position in the main scanning direction at the boundary between the areas irradiated with the light beams by each of the two light beam scanning devices 21-1, 21-2. [Explanation of symbols]

[0048] 21, 21-1, 21-2 Optical beam scanning device 24 Secondary transfer belt 401 Pixel clock generation unit 1, 2 402 Synchronous detection lighting control section 1, 2 404 Writing start position control section 1, 2 405 LD control section 1, 2 406 Polygon motor control unit 1, 2 407 Printer control unit 407a Split section 407b, 407c Image writing control unit 1, 2 409 Storage section [Prior art documents] [Patent documents]

[0049] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-40098

Claims

1. an optical writing device in which a plurality of optical writing means are arranged in a scanning direction, each of which forms a latent image by irradiating an image carrier with a light beam corresponding to image data using a single scanning means, a scanning area on the image carrier is divided into a plurality of areas in a main scanning direction, and a latent image is formed by irradiating a light beam to each of the plurality of areas using each of the optical writing means; a toner developing means for developing the latent image; a transfer means for transferring the visualized toner image onto a recording sheet; a dividing unit that divides the image data for each of the optical writing units, A writing device in which at least one of the area width in which both of the two adjacent optical writing means can irradiate a light beam onto the boundary portion of the multiple areas, and the data amount contained in both of the two adjacent optical writing means of the image data after division is ensured to be equal to or greater than the adjustment amount of the image position in the main scanning direction.

2. 2. The writing device according to claim 1, further comprising: a change unit that changes a writing start timing when adjusting the image position in the main scanning direction.

3. 3. The writing device according to claim 2, wherein said changing means changes a writing start timing and a writing image width when adjusting the image position in the main scanning direction.

4. 4. The writing device according to claim 2, wherein said changing means stores the divided image data in a memory and adjusts the image data to be read.

5. a writing method executed by a writing device comprising: a plurality of optical writing means arranged in a scanning direction, each of which forms a latent image by irradiating an image carrier with a light beam corresponding to image data using a single scanning means; an optical writing device in which a scanning area on the image carrier is divided into a plurality of areas in a main scanning direction, and a latent image is formed by irradiating each of the plurality of areas with a light beam using each of the optical writing means; a toner developing means for visualizing the latent image; and a transfer means for transferring the visualized toner image onto a recording sheet, dividing the image data for each of the optical writing means; a step of ensuring that at least one of an area width in which the light beam can be irradiated onto the boundary portions of the plurality of areas by both of the two adjacent optical writing means and an amount of data included in both of the two adjacent optical writing means among the divided image data is equal to or greater than an adjustment amount of the image position in the main scanning direction; A writing method including:

Images