Writing device and writing method

Abstract

To provide a writing device and a writing method capable of preventing an image position from being deviated with time in an image forming apparatus in which two optical scanners per color are arranged in a scanning direction.SOLUTION: The present invention provides: A plurality of optical writing means are arranged in a scanning direction, dividing a scanning area on the image carrier in a main scanning direction, and a detector that transfers an image-misregistration correction pattern visualized by a toner developing unit onto a belt and detects the image-misregistration correction pattern and a corrector that corrects an image misregistration based on a detection result of the image-misregistration correction pattern. The correction unit detects the image-misregistration correction pattern generated by each of the adjacent optical writing units by the same detection unit, and corrects the image misregistration occurring between the adjacent optical writing units based on the detection result.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In a color image forming device (an example of a writing device) that forms an image by irradiating an image carrier with light according to image data to form a latent image, visualizing the latent image using a developing means, and transferring the visualized image onto recording paper, a technology has been devised in which an image position deviation correction pattern for each color is generated on a belt, the image position deviation correction pattern is detected, the amount of image position deviation for each color relative to a reference color is calculated, and the image position is corrected according to the result.

[0003] Furthermore, in an image forming apparatus in which two optical scanning devices per color that irradiate image light according to image data onto an image carrier are arranged in the scanning direction, a technology has been devised that can increase the image width and improve printing speed by stitching images together on the image carrier. For example, Patent Document 1 discloses a configuration in which, in order to stitch together multiple writing optical systems in the main scanning direction, a detection device detects a position detection pattern formed on a photosensitive member and corrects main scanning misalignment based on the detection result in order to correct the position of the seams in the main scanning direction. Summary of the Invention [Problem to be solved by the invention]

[0004] However, while image position deviation correction control is effective in correcting deviations between colors in image forming devices that use one optical scanning device per color, in image forming devices that have two optical scanning devices per color aligned in the scanning direction, deviations in the image positions in the main scanning direction and sub-scanning direction at the boundary within the same color may occur over time.

[0005] Furthermore, in an image forming apparatus in which two optical scanning devices per color are arranged in the scanning direction, if the two optical scanning devices scan in directions away from each other, magnification deviation at the boundary can be reduced and the image connection state at the boundary can be maintained, but deviation may occur over time depending on the scanning direction.Furthermore, in the case of a color image forming apparatus, if image position deviation is detected and corrected using individual detection means for each color, multiple detection means are required.

[0006] The present invention has been made in view of the above, and aims to provide a writing device and a writing method that can prevent image positions in the main scanning direction and sub scanning direction of boundary areas within the same color from shifting over time, regardless of the scanning direction, in an image forming device in which two optical scanning devices per color are arranged in the scanning direction. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the present invention provides an optical beam scanning device in which a plurality of optical writing means are arranged in a scanning direction, each of which forms a latent image by scanning an optical beam corresponding to image data onto an image carrier using a single scanning means, the scanning area on the image carrier is divided in a main scanning direction, and a latent image is formed by irradiating each divided area with a light beam by each of the optical writing means; a toner developing means for visualizing the latent image; a generating means for generating the image data of an image misalignment correction pattern; a transfer means for transferring the image misalignment correction pattern visualized by the toner developing means onto a belt; a detecting means for detecting the image misalignment correction pattern on the belt; and a correcting means for correcting image misalignment based on the detection result of the image misalignment correction pattern, wherein the correcting means detects the image misalignment correction patterns generated by adjacent optical writing means using the same detecting means, and corrects image misalignment occurring between adjacent optical writing means based on the detection result of the image misalignment correction pattern. [Effects of the Invention]

[0008] According to the present invention, in an image forming device in which two optical scanning devices per color are arranged in the scanning direction, it is possible to prevent image positions in the main scanning direction and sub-scanning direction of boundary areas within the same color from shifting over time, regardless of the scanning direction. [Brief explanation of the drawings]

[0009] [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 for explaining an example of the front stage of the image formation control unit of 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 deviation correction function in the image forming apparatus according to the present embodiment. [Figure 12] FIG. 12 is a diagram for explaining an example of an image position deviation correction pattern in the image forming apparatus according to the present embodiment. [Figure 13] FIG. 13 is a diagram for explaining an example of an image positional deviation correction pattern in the image forming apparatus according to the present embodiment. [Figure 14] FIG. 14 is a flowchart showing an example of the flow of image positional deviation correction in the image forming apparatus according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, with reference to the accompanying drawings, an embodiment of a writing device and an image forming apparatus to which a writing method is applied will be described in detail.

[0011] 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.

[0012] 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 the paper onto which the toner image has been transferred is fed. The fixing unit 25 fuses the toner image transferred onto the paper using a heating belt 26 and a pressure roller 27, and fixes it to the paper by pressing it. Below the secondary transfer unit 22 and the fixing unit 25 is a sheet inversion unit 28 that inverts the paper immediately after an image has been formed on the front side so that an image can be recorded on the back side as well.

[0013] 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.

[0014] 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 an image, such as an image misalignment correction pattern visualized by a development unit, onto the secondary transfer belt 24 (an example of a belt). The paper with the transferred toner image is fed into the fixing unit 25, where the toner image is fixed to the paper.

[0015] The above-mentioned paper is fed by selectively rotating one of the paper feed rollers 42 of the paper feed table 200, feeding a sheet from one of the paper feed trays 44 provided in the paper feed unit 43, separating only one sheet by the separation roller 45, placing it in the transport roller unit 46, transporting it by the transport roller 47, and leading it to the transport roller unit 48 in the printer 100, where it hits and stops against the registration roller 49 of the transport roller unit 48, and then being sent to the secondary transfer unit 22 at the timing mentioned above. Paper can also be fed by inserting it into the manual feed tray 51. When the user has inserted paper into the manual feed tray 51, the printer 100 rotates the paper feed roller 50 to separate one of the sheets on the manual feed tray 51 and pull it into the manual feed path 53, where it also hits and stops against the registration roller 49.

[0016] 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.

[0017] 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).

[0018] 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 latent images by irradiating each divided area with a light beam by each of the light beam scanning devices 21-1 and 21-2.

[0019] 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.

[0020] The secondary transfer unit 22 is equipped with a sensor 408 (see FIG. 4) for detecting the image misregistration correction pattern formed on the secondary transfer belt 24. The sensor 408 is a reflective optical sensor. The printer 100 transfers the image misregistration correction pattern formed on the intermediate transfer belt 10 onto the secondary transfer belt 24, and corrects image misregistration between each color in the main scanning direction and the sub-scanning direction based on the detection result of the transferred image misregistration correction pattern by the sensor 408. A secondary transfer belt cleaning unit is provided to remove the toner image on the secondary transfer belt 24. In addition, each color is equipped with a toner bottle containing toner to replenish the developing unit.

[0021] 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.

[0022] A synchronization mirror, a synchronization lens, and a synchronization sensor are provided at the end of the writing side 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. Regarding the light beam that scans the photosensitive drum, there is an area near the center of the photosensitive drum that can be scanned by both light beam scanning device 21-1 and light beam scanning device 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 is similar except for the printer control unit 407, the storage unit 409 (correction data storage unit), and the sensor 408. 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 at the image writing end of the light beam scanning device 21-1 in the main scanning direction. The light 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 light 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 the writing start position control unit 1 (404) and the synchronous detection lighting control unit 1 (402).

[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] The sensor 408 for detecting the image positional deviation correction pattern is arranged at a position where it can detect the area that can be scanned by both the light beam scanning device 21-1 and the light beam scanning device 21-2, and sends the detected image pattern information to the printer control unit 407, which calculates the amount of positional deviation, generates correction data, sets it in the writing start position control unit 1 (404) and the pixel clock generation unit 1 (401), and stores the correction data in the memory unit 409.

[0029] 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).

[0030] 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).

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 8 is a diagram illustrating an example of the front stage of the image formation control unit of the image forming apparatus according to this embodiment. The front stage of the image formation control unit is equipped with a line memory, which outputs image data captured from a printer controller, frame memory, scanner, etc. at the timing of XFGATE and XLGATE in synchronization with PCLK, and outputs image signals for the number of beams. The output image data is sent to LD control unit 405, which turns on each LD at that timing.

[0037] 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.

[0038] A sensor 408 that detects the image position deviation correction pattern is connected to the I / O port. In addition, write start position control units 1 and 2 (404), LD control units 1 and 2 (405), synchronization 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.

[0039] 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.

[0040] Fig. 11 is a diagram for explaining an example of an image misalignment correction function in the image forming apparatus according to this embodiment. In this embodiment, the functional blocks shown in Fig. 11 are realized by printer control unit 407 executing an image misalignment correction program stored in ROM. Specifically, as shown in Fig. 11, printer control unit 407 executes the image misalignment correction program to realize the functions of correction data setting unit 407a, pattern formation control unit 407b, pattern detection unit 407c, misalignment amount calculation unit 407d, determination unit 407e, correction data calculation unit 407f, memory control unit 407g, and image formation control unit 407h.

[0041] The correction data setting unit 407a sets the correction data stored in the memory unit 409 in the write start position control unit 404 and the pixel clock generation unit 401. The pattern formation control unit 407b is an example of a generation unit that generates image data of an image misalignment correction pattern. The pattern detection unit 407c is an example of a detection unit that detects the image misalignment correction pattern formed on the secondary transfer belt 24 (an example of a belt) based on the output of the sensor 408. Here, the pattern detection unit 407c may be a detection unit common to all colors. This makes it possible to reduce image misalignment that occurs between adjacent light beam scanning devices 21-1 and 21-2 for each color at the same cost as a monochrome machine.

[0042] The deviation amount calculation unit 407d calculates the amount of deviation from a reference based on the image deviation correction pattern detected by the pattern detection unit 407c. The determination unit 407e determines whether or not to perform image deviation correction based on the calculated deviation amount from the reference. The correction data calculation unit 407f calculates correction data when image deviation correction is to be performed. The storage control unit 407g updates the correction data stored in the storage unit 409 with the calculated correction data. The image formation control unit 407h performs printing processing based on the calculated correction data.

[0043] That is, the misalignment amount calculation unit 407d, the determination unit 407e, the correction data calculation unit 407f, and the image formation control unit 407h function as an example of a correction unit that corrects image misalignment based on the detection result of the image misalignment correction pattern. Also, the misalignment amount calculation unit 407d, the determination unit 407e, the correction data calculation unit 407f, and the image formation control unit 407h detect the image misalignment correction patterns generated by the adjacent light beam scanning devices 21-1 and 21-2 using the same sensor 408, and correct the image misalignment that occurs between the adjacent light beam scanning devices 21-1 and 21-2 based on the detection result of the image misalignment correction pattern.

[0044] This makes it possible to prevent image position shifts in the main scanning direction and sub-scanning direction at boundaries within the same color over time in an image forming device in which two light beam scanning devices 21-1, 21-2 per color are arranged in the scanning direction, and in the case of a color image forming device, it is possible to prevent image shifts in the main scanning direction and sub-scanning direction at boundaries within the same color with a single sensor 408.

[0045] 12 is a diagram for explaining an example of an image misalignment correction pattern in the image forming apparatus according to the present embodiment. In this embodiment, the pattern formation control unit 407b generates (forms) image misalignment correction patterns K1 and K2 on the secondary transfer belt 24 in order to correct image misalignment in the sub-scanning direction.

[0046] Image misalignment correction pattern K1 is a pattern formed by light beam scanning device 21-1, and image misalignment correction pattern K2 is a pattern formed by light beam scanning device 21-2. Near the center of the photosensitive drum scanned by the light beam, an area detectable by sensor 408 can be image-written by both light beam scanning device 21-1 and light beam scanning device 21-2. Horizontal line images (image misalignment correction patterns K1 and K2) are formed on secondary transfer belt 24. As secondary transfer belt 24 moves in the direction of the arrow, image misalignment correction patterns K1 and K2 are detected by sensor 408, and the amount of deviation (time) of image misalignment correction pattern K2 relative to image misalignment correction pattern K1 is calculated. The detection timing of the horizontal lines (image misalignment correction patterns K1 and K2) changes depending on the image position deviation in the sub-scanning direction.

[0047] Specifically, in the sub-scanning direction, if the ideal time is T1 and the time from when the image misalignment correction pattern K1 is detected to when the image misalignment correction pattern K2 is detected is TK12, then TK12-T1 is the sub-scanning deviation of the image of the light beam scanning device 21-2 relative to the image of the light beam scanning device 21-1, and the timing of the XFGATE signal that determines the write start timing is changed by an amount equivalent to that amount.

[0048] It is possible to improve the correction accuracy by generating a plurality of pairs of the image position deviation correction patterns K1 and K2, calculating the amount of deviation for each pair, and averaging the amounts. The same applies to each color. The shape of the image position deviation correction pattern is an example and is not limited to this.

[0049] 13 is a diagram for explaining an example of an image misalignment correction pattern in the image forming apparatus according to the present embodiment. In this embodiment, the pattern formation control unit 407b generates (forms) an image misalignment correction pattern on the secondary transfer belt 24 in order to correct image misalignment in the main scanning direction.

[0050] In this embodiment, the pattern formation control unit 407b forms diagonal line images (image misalignment correction patterns K3 and K4) after correcting the misalignment in the sub-scanning direction. The image misalignment correction pattern K3 is a pattern formed by the light beam scanning device 21-1, and the image misalignment correction pattern K4 is a pattern formed by the light beam scanning device 21-2. As with the horizontal lines (image misalignment correction patterns K1 and K2), the image misalignment correction patterns K3 and K4 are detected by the sensor 408, and the amount of misalignment (time) of the image misalignment correction pattern K4 relative to the image misalignment correction pattern K3 is calculated. The detection timing of the diagonal lines (image misalignment correction patterns K3 and K4) changes depending on the image position in the main scanning direction. However, by forming the patterns immediately after correcting the misalignment in the sub-scanning direction, the misalignment in the main scanning direction can be corrected without any misalignment in the sub-scanning direction.

[0051] Specifically, in the main scanning direction, if the ideal time is T2 and the time from when image misalignment correction pattern K3 is detected to when image misalignment correction pattern K4 is detected is TK34, TK34-T2 is the main scanning misalignment of the image of light beam scanning device 21-2 relative to the image of light beam scanning device 21-1, and the timing of the XLGATE signal that determines the write start timing is changed by an amount equivalent to that amount.

[0052] That is, the correction data calculation unit 407f corrects image misalignment in the sub-scanning direction and the main scanning direction. This makes it possible to reduce image misalignment that occurs between adjacent light beam scanning devices 21-1 and 21-2. The correction data calculation unit also corrects the misalignment of the image misalignment correction pattern K2 generated by the adjacent light beam scanning device 21-2 relative to the image misalignment correction pattern K1 generated by the reference light beam scanning device 21-1. This makes it possible to reduce image misalignment that occurs between adjacent light beam scanning devices 21-1 and 21-2. The correction data calculation unit 407f also corrects the image misalignment in the main scanning direction after correcting the image misalignment in the sub-scanning direction. This makes it possible to reliably reduce image misalignment in the main scanning direction.

[0053] It is possible to improve the correction accuracy by generating a plurality of pairs of the image position deviation correction patterns K3 and K4, calculating the amount of deviation for each pair, and averaging the amounts. The same applies to each color. The shape of the image position deviation correction pattern is an example and is not limited to this.

[0054] 14 is a flowchart showing an example of the flow of image misalignment correction in the image forming apparatus according to this embodiment. Printer control unit 407 controls the execution timing of image misalignment correction, and executes it when the image forming apparatus is powered on, when printing starts, after every specified number of prints, or when the temperature is monitored and a temperature change greater than a specified value occurs.

[0055] First, printer control unit 407 sets correction data stored in memory unit 409 (step S1401). Here, the correction data to be set is the correction data set in the previous correction operation and saved in memory unit 409. Then, printer control unit 407 rotates the polygon motor (step S1402), turns on the laser (LD) (step S1403), generates pattern 1 (patterns K1 and K21 for correcting image positional deviation) (step S1404), detects it with sensor 408 (step S1405), and calculates the amount of deviation (step S1406).

[0056] Then, printer control unit 407 determines whether to perform image positional deviation correction (step S1407). This determination means that correction is performed if the amount of deviation is equal to or greater than half the correction resolution. If correction is to be performed (step S1407: Yes), printer control unit 407 calculates correction data (step S1408), stores it (step S1409), and sets the correction data (step S1410). The correction data here is the setting value of the XFGATE signal that determines the image position in the sub-scanning direction. If correction is not to be performed (step S1407: No), printer control unit 407 does not update the correction data.

[0057] Next, printer control unit 407 generates pattern 2 (patterns K3 and K4 for image misalignment correction) (step S1411), detects it with sensor 408 (step S1412), and calculates the amount of misalignment (step S1413). Printer control unit 407 then determines whether to perform image misalignment correction (step S1414). This determination indicates that correction is to be performed if the amount of misalignment is equal to or greater than half the correction resolution. If correction is to be performed (step S1414: Yes), correction data is calculated (step S1415), stored (step S1416), and set (step S1417). The correction data here is the setting value of the XLGATE signal that determines the image position in the main scanning direction. If correction is not to be performed (step S1414: No), printer control unit 407 does not update the correction data.

[0058] Then, printer control unit 407 turns off the laser (step S1418), stops the polygon motor, and ends the process (step S1419). By performing image position deviation correction for each color, it becomes possible to correct image position deviation that occurs between two light beam scanning devices 21-1 and 21-2 for all colors. This embodiment can be applied not only to color image forming apparatuses, but also to monochrome image forming apparatuses.

[0059] In this way, according to the image forming apparatus of this embodiment, in an image forming apparatus in which two optical scanning devices per color are arranged in the scanning direction, it is possible to prevent image position shifts in the main scanning direction and sub-scanning direction at boundaries within the same color from occurring over time, regardless of the scanning direction, and in the case of a color image forming apparatus, it is possible to prevent image shifts in the main scanning direction and sub-scanning direction at boundaries within the same color from occurring using a single detection means.

[0060] For example, aspects of the present invention are as follows. <1> a light beam scanning device in which a plurality of optical writing means are arranged in a scanning direction, each of which forms a latent image by scanning an image carrier with a light beam according to image data using a single scanning means, and a scanning area on the image carrier is divided in a main scanning direction, and a latent image is formed by irradiating each divided area with a light beam by each of the optical writing means; a toner developing means for developing the latent image; a generating means for generating the image data of the image position deviation correction pattern; a transfer means for transferring the image misregistration correction pattern visualized by the toner developing means onto a belt; a detection means for detecting the image position deviation correction pattern on the belt; a correction unit that corrects image position deviation based on the detection result of the image position deviation correction pattern, The correction means detects the image position shift correction patterns generated by each of the adjacent optical writing means using the same detection means, and corrects the image position shift that occurs between the adjacent optical writing means based on the detection results of the image position shift correction patterns. <2> the correction means corrects image positional deviation in the sub-scanning direction and the main scanning direction; <1> 2. A writing device according to claim 1 . <3> the correction means corrects a deviation of the image position deviation correction pattern generated by the optical writing means installed adjacent to the image position deviation correction pattern generated by the optical writing means serving as a reference. <1> or <2> 2. A writing device according to claim 1 . <4> the correcting means corrects the image positional deviation in the main scanning direction after correcting the image positional deviation in the sub-scanning direction; <2> 2. A writing device according to claim 1 . <5> the detecting means is a detecting means common to all colors; <1> from <4> 10. A writing device according to any one of the preceding items. <6> a light beam scanning device in which a plurality of optical writing means are arranged in a scanning direction, each of which forms a latent image by scanning an image carrier with a light beam corresponding to image data using one scanning means, a scanning area on the image carrier is divided in a main scanning direction, and a latent image is formed by irradiating each divided area with a light beam by each of the optical writing means; a toner developing means for visualizing the latent image; a transfer means for transferring the image visualized by the toner developing means onto a belt; and a detection means for detecting an image position deviation correction pattern on the belt, detecting the image position deviation correction patterns generated by the adjacent optical writing means by the same detecting means; correcting image positional deviation occurring between adjacent optical writing means based on the detection result of the image positional deviation correction pattern; A writing method including: [Explanation of symbols]

[0061] 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 Correction data setting section 407b Pattern formation control section 407c Pattern detection unit 407d Deviation amount calculation unit 407e Judgment section 407f Correction data calculation unit 407g Memory control unit 407h Image formation control unit 408 Sensors 409 Storage section [Prior art documents] [Patent documents]

[0062] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-148741

Claims

1. a light beam scanning device in which a plurality of optical writing means are arranged in a scanning direction, each of which forms a latent image by scanning an image carrier with a light beam corresponding to image data using a single scanning means, the scanning area on the image carrier is divided in a main scanning direction, and a latent image is formed by irradiating each divided area with a light beam by each of the optical writing means; a toner developing means for developing the latent image; a generating means for generating the image data of the image position deviation correction pattern; a transfer means for transferring the image misregistration correction pattern visualized by the toner developing means onto a belt; a detection means for detecting the image position deviation correction pattern on the belt; a correction unit that corrects image position deviation based on the detection result of the image position deviation correction pattern, The correction means detects the image position shift correction patterns generated by each of the adjacent optical writing means using the same detection means, and corrects the image position shift that occurs between the adjacent optical writing means based on the detection results of the image position shift correction patterns.

2. 2. The writing device according to claim 1, wherein said correcting means corrects image positional deviations in the sub-scanning direction and the main scanning direction.

3. 3. The writing device according to claim 1, wherein the correction means corrects a deviation of the image misalignment correction pattern generated by the optical writing means installed adjacent to the reference optical writing means relative to the image misalignment correction pattern generated by the reference optical writing means.

4. 3. The writing device according to claim 2, wherein said correcting means corrects image positional deviation in the main scanning direction after correcting image positional deviation in the sub-scanning direction.

5. 3. The writing device according to claim 1, wherein said detecting means is a detecting means common to all colors.

6. a light beam scanning device in which a plurality of optical writing means are arranged in a scanning direction, each of which forms a latent image by scanning 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 in a main scanning direction, and a latent image is formed by irradiating each divided area with a light beam by each of the optical writing means; a toner developing means for visualizing the latent image; a transfer means for transferring the image visualized by the toner developing means onto a belt; and a detection means for detecting an image position deviation correction pattern on the belt, detecting the image position deviation correction patterns generated by the adjacent optical writing means by the same detecting means; correcting image positional deviation occurring between adjacent optical writing means based on the detection result of the image positional deviation correction pattern; A writing method including:

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