JP5672865B2 - Image forming apparatus and control program for image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus and a control program for the image forming apparatus, and more particularly to correction of phase shift information for correcting unevenness in scanning speed.

  In recent years, there has been a tendency to digitize information, and image processing apparatuses such as printers and facsimiles used for outputting digitized information and scanners used for digitizing documents have become indispensable devices. Such an image processing apparatus is often configured as a multifunction machine that can be used as a printer, a facsimile, a scanner, or a copier by providing an imaging function, an image forming function, a communication function, and the like.

  Among such image processing apparatuses, electrophotographic image forming apparatuses are widely used in image forming apparatuses used for outputting digitized documents. In an electrophotographic image forming apparatus, an electrostatic latent image is formed by exposing a photoreceptor, and the electrostatic latent image is developed using a developer such as toner to form a toner image. Paper output is performed by transferring the toner image onto paper.

  In an electrophotographic image forming apparatus, an optical writing device for exposing a photosensitive member includes a light source for irradiating a beam for exposing the photosensitive member and a polygon scanner for deflecting the irradiated beam to scan the entire surface of the photosensitive member. Including deflectors. In such an optical writing device, variations in the distance between the reflecting surface of the deflector and the rotation axis cause unevenness in the scanning speed of the light spot, which is the position of the beam irradiated onto the surface to be scanned.

  This uneven scanning speed will be described in more detail. In a general optical writing apparatus, writing of an electrostatic latent image by exposing a photosensitive member with a light beam is performed according to a pixel clock. That is, the presence or absence of light beam irradiation based on whether each pixel is colored or colorless is switched according to the pixel clock. Since the pixel clock has a constant frequency in principle, the scanning speed of the light spot is required to be constant on the main scanning line.

  However, as long as the polygon scanner is used, variations in the distance between the reflecting surface of the deflector and the rotation axis naturally occur, and thus the above-described uneven speed is inevitable. That is, on one main scanning line, the movement of the light spot is fast in a certain portion, and the movement of the light spot is slow in a certain portion. If the scanning speed unevenness is not properly corrected, dot position deviation in the main scanning direction occurs, resulting in image fluctuation and image quality deterioration.

  In order to correct the scanning speed unevenness, the dot position in the main scanning direction is corrected by modulating the pixel clock on the scanning line in accordance with the generated scanning speed unevenness (for example, Patent Documents). 1 or Patent Document 2).

  On the other hand, in an electrophotographic image forming apparatus, by adjusting the timing of forming an electrostatic latent image by exposing a photoconductor to the timing of transporting the paper, adjustment is made so that an image is formed in the correct range of the paper. Is done. In addition, in a tandem image forming apparatus that forms a color image using a plurality of photoconductors, the exposure timing of each color photoconductor is adjusted so that the images developed on the photoconductors of each color are accurately superimposed. (For example, refer to Patent Document 3). Hereinafter, these adjustment processes are collectively referred to as misalignment correction.

  The correction of the dot position deviation due to the scanning speed unevenness described above is performed based on the modulation information of the pixel clock corresponding to the speed unevenness measured in advance. When generating the modulation information of the pixel clock, the scanning speed unevenness is measured by using a dedicated jig for measuring the scanning speed unevenness in a state where the optical writing device is incorporated in the image forming apparatus. Therefore, when the image forming apparatus actually starts operation, modulation information of the pixel clock corresponding to the individual difference of each apparatus is generated and stored, and an image in which the dot position deviation is corrected is formed. .

  Here, in consideration of the secular change of the apparatus, it is preferable not to use the permanently stored pixel clock modulation information, but to periodically measure the scanning speed unevenness and update the pixel clock modulation information. . However, in order to generate pixel clock modulation information, it is necessary to measure the scanning speed unevenness using a dedicated jig as described above. There are problems such as equipment operating costs and downtime of equipment being measured.

  Further, when the optical writing device is replaced as a result of using the image forming apparatus for many years, the scanning speed unevenness different from the scanning speed unevenness in the optical writing device used so far occurs. Therefore, it is necessary to update the modulation information of the pixel clock, which causes the same problem as described above.

  On the other hand, in the above-described misregistration correction, the image position in the main scanning direction is also detected. Therefore, by using the misregistration amounts of the images detected at a plurality of points in the main scanning direction, uneven scanning speed is obtained. It is possible to measure. If this measurement method is used, the above-mentioned problems of operation cost and downtime can be solved, but the detection accuracy of the sensor generally used in the positional deviation correction is lower than the measurement accuracy by the jig described above, This is not preferable in dot position deviation correction in the main scanning direction, which requires finer adjustment.

  Further, when the modulation information of the pixel clock is updated by measuring the unevenness of the scanning speed using a jig, it is necessary to provide an interface for storing information from the outside to the controller of the optical writing device. This also leads to an increase in the cost of the writing device.

  The present invention has been made in consideration of the above-described circumstances, and an object thereof is to realize an update of a correction value for correcting uneven scanning speed in an optical writing device at a low cost.

In order to solve the above problems, one embodiment of the present invention is an image forming apparatus including an optical writing device that forms an electrostatic latent image on a photosensitive member by irradiating a light beam, and includes light irradiated from a light source. A scanning unit that guides a beam onto the photosensitive member and scans the photosensitive member, and a scanning speed that is a change on a scanning line at a speed at which the light beam guided by the scanning unit scans the photosensitive member. Based on phase shift reference information storage unit storing phase shift reference information serving as a reference for correcting unevenness, and image information that is information of an image to be formed as the electrostatic latent image, the phase shift reference information And developing the electrostatic latent image formed by the irradiation light beam according to the control by the writing control unit and controlling the light source while correcting the scanning speed unevenness according to An image detecting unit configured to detect that an image for detecting unevenness in scanning speed formed by the transfer is transported by a transport body that moves relative to the photosensitive body and reaches a predetermined position; and the scanning speed Based on the detection result of the unevenness detection image, a scanning speed unevenness calculation unit that calculates the scanning speed unevenness, and a detection tolerance storage that stores the calculated scanning speed unevenness as information indicating a detection tolerance of the image detection unit. When the scanning section is replaced with the scanning section , the stored detection tolerance is applied to the scanning speed unevenness calculated by forming and detecting the image for detecting the unevenness in scanning speed. And a correction value calculation unit that generates phase shift correction information for correcting the phase shift information.

  According to the present invention, update of a correction value for correcting uneven scanning speed in an optical writing device can be realized at low cost.

1 is a block diagram illustrating a hardware configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a functional configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a configuration of a print engine according to an embodiment of the present invention. It is a top view which shows the structure of the optical writing apparatus which concerns on embodiment of this invention. It is a sectional side view which shows the structure of the optical writing apparatus which concerns on embodiment of this invention. It is a figure which shows the phase shift characteristic in the optical writing apparatus which concerns on embodiment of this invention. It is a block diagram which shows the control part of the optical writing apparatus which concerns on embodiment of this invention. It is a figure which shows the example of the information memorize | stored in the reference value memory | storage part which concerns on embodiment of this invention. It is a figure which shows the example of the mark for position shift correction which concerns on embodiment of this invention. It is a figure which shows the detection aspect of the scanning speed nonuniformity which concerns on embodiment of this invention. It is a figure which shows the information format of the phase soft information which concerns on embodiment of this invention. It is a figure which shows the example of the information memorize | stored in the correction value memory | storage part which concerns on embodiment of this invention. It is a figure which shows the production | generation aspect of the phase shift sensor tolerance information which concerns on embodiment of this invention. It is a figure which shows the production | generation aspect of the phase shift correction value information which concerns on embodiment of this invention. It is a figure which shows the production | generation timing of the phase shift correction value information which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, a multi function peripheral (MFP) as an image forming apparatus will be described as an example. The image forming apparatus according to the present embodiment is an electrophotographic multifunction machine, and its gist is management of phase shift information in an optical writing apparatus for forming an electrostatic latent image on a photoreceptor. Note that the image forming apparatus need not be a multifunction machine, and may be, for example, a copying machine, a printer, a facsimile machine, or the like.

  FIG. 1 is a block diagram illustrating a hardware configuration of an image forming apparatus 1 according to the present embodiment. As shown in FIG. 1, the image forming apparatus 1 according to the present embodiment includes an engine that executes image formation in addition to the same configuration as an information processing terminal such as a general server or a PC (Personal Computer). That is, the image forming apparatus 1 according to the present embodiment includes a CPU (Central Processing Unit) 10, a RAM (Random Access Memory) 11, a ROM (Read Only Memory) 12, an engine 13, an HDD (Hard Disk Drive) 14, and an I / O. F15 is connected via the bus 18. Further, an LCD (Liquid Crystal Display) 16 and an operation unit 17 are connected to the I / F 15.

  The CPU 10 is a calculation unit and controls the operation of the entire image forming apparatus 1. The RAM 11 is a volatile storage medium capable of reading and writing information at high speed, and is used as a work area when the CPU 10 processes information. The ROM 12 is a read-only nonvolatile storage medium, and stores programs such as firmware. The engine 13 is a mechanism that actually executes image formation in the image forming apparatus 1.

  The HDD 14 is a nonvolatile storage medium capable of reading and writing information, and stores an OS (Operating System), various control programs, application programs, and the like. The I / F 15 connects and controls the bus 18 and various hardware and networks. The LCD 16 is a visual user interface for the user to check the state of the image forming apparatus 1. The operation unit 17 is a user interface such as a keyboard and a mouse for the user to input information to the image forming apparatus 1.

  In such a hardware configuration, a program stored in a recording medium such as the ROM 12, the HDD 14, or an optical disk (not shown) is read into the RAM 11 and operates according to the control of the CPU 10, thereby configuring a software control unit. A functional block that realizes the functions of the image forming apparatus 1 according to the present embodiment is configured by a combination of the software control unit configured as described above and hardware.

  Next, the functional configuration of the image forming apparatus 1 according to the present embodiment will be described with reference to FIG. FIG. 2 is a block diagram illustrating a functional configuration of the image forming apparatus 1 according to the present embodiment. As shown in FIG. 2, the image forming apparatus 1 according to the present embodiment includes a controller 20, an ADF (Auto Document Feeder) 21, a scanner unit 22, a paper discharge tray 23, a display panel 24, and a paper feed table. 25, a print engine 26, a paper discharge tray 27, and a network I / F 28.

  The controller 20 includes a main control unit 30, an engine control unit 31, an input / output control unit 32, an image processing unit 33, and an operation display control unit 34. As shown in FIG. 2, the image forming apparatus 1 according to the present embodiment is configured as a multifunction machine having a scanner unit 22 and a print engine 26. In FIG. 2, the electrical connection is indicated by solid arrows, and the flow of paper is indicated by broken arrows.

  The display panel 24 is an output interface that visually displays the state of the image forming apparatus 1 and is an input when the user directly operates the image forming apparatus 1 or inputs information to the image forming apparatus 1 as a touch panel. It is also an interface (operation unit). The network I / F 28 is an interface for the image forming apparatus 1 to communicate with other devices via the network, and uses an Ethernet (registered trademark) or a USB (Universal Serial Bus) interface.

  The controller 20 is configured by a combination of software and hardware. Specifically, a control program such as firmware stored in a nonvolatile recording medium such as the ROM 12 and the nonvolatile memory and the HDD 14 and the optical disk is loaded into a volatile memory (hereinafter referred to as a memory) such as the RAM 11 to control the CPU 10. The controller 20 is configured by a software control unit configured according to the above and hardware such as an integrated circuit. The controller 20 functions as a control unit that controls the entire image forming apparatus 1.

  The main control unit 30 plays a role of controlling each unit included in the controller 20 and gives a command to each unit of the controller 20. The engine control unit 31 serves as a drive unit that controls or drives the print engine 26, the scanner unit 22, and the like. The input / output control unit 32 inputs a signal or a command input via the network I / F 28 to the main control unit 30. The main control unit 30 controls the input / output control unit 32 and accesses other devices via the network I / F 28.

  The image processing unit 33 generates drawing information based on the print information included in the input print job under the control of the main control unit 30. The drawing information is information for drawing an image to be formed in the image forming operation by the print engine 26 as an image forming unit. The print information included in the print job is image information converted into a format that can be recognized by the image forming apparatus 1 by a printer driver installed in an information processing apparatus such as a PC. The operation display control unit 34 displays information on the display panel 24 or notifies the main control unit 30 of information input via the display panel 24.

  When the image forming apparatus 1 operates as a printer, first, the input / output control unit 32 receives a print job via the network I / F 28. The input / output control unit 32 transfers the received print job to the main control unit 30. When receiving the print job, the main control unit 30 controls the image processing unit 33 to generate drawing information based on the print information included in the print job.

  When drawing information is generated by the image processing unit 33, the engine control unit 31 performs image formation on the paper conveyed from the paper feed table 25 based on the generated drawing information. That is, the print engine 26 functions as an image forming unit. The paper on which image formation has been performed by the print engine 26 is discharged to a paper discharge tray 27.

  When the image forming apparatus 1 operates as a copying machine, the image processing unit 33 is based on the imaging information received by the engine control unit 31 from the scanner unit 22 or the image information generated by the image processing unit 33 based on the imaging information. Generates drawing information. Based on the drawing information, the engine control unit 31 drives the print engine 26 as in the case of the printer operation.

  Next, the configuration of the print engine 26 according to the present embodiment will be described with reference to FIG. As shown in FIG. 3, the print engine 26 according to the present embodiment includes a configuration in which image forming units 106 of respective colors are arranged along a conveyor belt 105 that is an endless moving unit, which is a so-called tandem type. It is what is said. That is, along the conveying belt 105 that conveys a sheet (an example of a recording medium) 104 that is separated and fed from the sheet feeding tray 101 by the sheet feeding roller 102 and the separation roller 103, the upstream side in the conveying direction of the conveying belt 105. A plurality of image forming units (electrophotographic process units) 106BK, 106M, 106C, and 106Y are arranged in this order.

  The plurality of image forming units 106BK, 106M, 106C, and 106Y have the same internal configuration except that the colors of the toner images to be formed are different. The image forming unit 106BK forms a black image, the image forming unit 106M forms a magenta image, the image forming unit 106C forms a cyan image, and the image forming unit 106Y forms a yellow image. In the following description, the image forming unit 106BK will be described in detail. However, since the other image forming units 106M, 106C, and 106Y are the same as the image forming unit 106BK, the image forming units 106M, 106C, and 106Y are similar to the image forming unit 106BK. As for each of the components, only the symbols distinguished by M, C, and Y are displayed in the drawing in place of the BK attached to each component of the image forming unit 106BK, and the description thereof is omitted.

  The conveying belt 105 is an endless belt, that is, an endless belt that is stretched between a driving roller 107 and a driven roller 108 that are rotationally driven. The drive roller 107 is driven to rotate by a drive motor (not shown), and the drive motor, the drive roller 107, and the driven roller 108 function as a drive unit that moves the conveyance belt 105 that is an endless moving unit. .

  At the time of image formation, the paper 104 stored in the paper feed tray 101 is sent out in order from the top, and the first image forming unit 106BK is conveyed by the conveyance belt 105 that is attracted to and rotated by the conveyance belt 105 by electrostatic adsorption action. Where the black toner image is transferred. That is, the conveyance belt 105 functions as a conveyance body that conveys a sheet that is an image transfer target.

  The image forming unit 106BK includes a photoconductor drum 109BK as a photoconductor, a charger 110BK arranged around the photoconductor drum 109BK, an optical writing device 111, a developing device 112BK, a photoconductor cleaner (not shown), and a static eliminator. 113BK and the like. The optical writing device 111 is configured to irradiate the respective photosensitive drums 109BK, 109M, 109C, and 109Y (hereinafter collectively referred to as “photosensitive drum 109”) with a laser beam.

  At the time of image formation, the outer peripheral surface of the photosensitive drum 109BK is uniformly charged by the charger 110BK in the dark, and then writing is performed by a laser beam corresponding to the black image from the optical writing device 111. An image is formed. The developing device 112BK visualizes the electrostatic latent image with black toner, thereby forming a black toner image on the photosensitive drum 109BK.

  This toner image is transferred onto the sheet 104 by the action of the transfer unit 115BK at a position (transfer position) where the photosensitive drum 109BK and the sheet 104 on the conveying belt 105 contact each other. By this transfer, an image of black toner is formed on the paper 104. After the transfer of the toner image is completed, unnecessary toner remaining on the outer peripheral surface of the photosensitive drum 109BK is wiped off by the photosensitive cleaner, and then the charge is removed by the charge eliminator 113BK, and waits for the next image formation.

  As described above, the sheet 104 on which the black toner image is transferred by the image forming unit 106BK is transported to the next image forming unit 106M by the transport belt 105. In the image forming unit 106M, a magenta toner image is formed on the photosensitive drum 109M by a process similar to the image forming process in the image forming unit 106BK, and the toner image is superimposed on the black image formed on the paper 104. And is transcribed.

  The sheet 104 is further conveyed to the next image forming units 106C and 106Y, and a cyan toner image formed on the photoconductive drum 109C and a yellow toner image formed on the photoconductive drum 109Y by the same operation. Are superimposed on the sheet 104 and transferred. In this way, a full color image is formed on the sheet 104. The sheet 104 on which the full-color superimposed image is formed is peeled off from the conveying belt 105 and the image is fixed by the fixing device 116, and then discharged to the outside of the image forming apparatus.

  In such an image forming apparatus 1, errors in the interaxial distances of the photosensitive drums 109 BK, 109 M, 109 C, and 109 Y, parallelism errors in the photosensitive drums 109 BK, 109 M, 109 C, and 109 Y, and deflection in the optical writing device 111. The toner images of each color do not overlap at positions that should originally overlap due to errors in the installation of mirrors, writing timing errors of electrostatic latent images on the photosensitive drums 109BK, 109M, 109C, and 109Y. May occur.

  For the same reason, the image may be transferred to a range that is outside the range where the image is originally transferred on the paper to be transferred. As such misregistration components, skew, sub-scan registration error, magnification error in the main scanning direction, registration error in the main scanning direction, and the like are mainly known. Also known are errors in the rotational speed of the conveyance rollers that convey the paper, errors in the conveyance amount due to wear, and the like.

  A pattern detection sensor 117 is provided to correct such positional deviation. The pattern detection sensor 117 is an optical sensor for reading the misregistration correction pattern transferred onto the paper 104 by the photosensitive drums 109BK, 109M, 109C, and 109Y. The pattern detection sensor 117 reads the correction pattern drawn on the surface of the paper 104. It includes a light emitting element for irradiating and a light receiving element for receiving reflected light from the correction pattern. As shown in FIG. 3, the pattern detection sensor 117 is supported on the same substrate along the direction orthogonal to the conveyance direction of the sheet 104 on the downstream side of the photosensitive drums 109BK, 109M, 109C, and 109Y. The details of the pattern detection sensor 117 and the mode of positional deviation correction will be described in detail later.

  Next, the optical writing device 111 according to the present embodiment will be described. FIG. 4 is a view of the optical writing device 111 according to the present embodiment as viewed from above. FIG. 5 is a cross-sectional view of the optical writing device according to the present embodiment as viewed from the side. As shown in FIGS. 4 and 5, the laser beams for writing on the photosensitive drums 109BK, 109M, 109C, and 109Y of the respective colors are light source devices 281BK, 281M, 281C, and 281Y as light sources (hereinafter collectively referred to as “light source device 281”). ). Note that the light source device 281 according to the present embodiment includes a semiconductor laser, a collimator lens, a slit, a prism, a cylinder lens, and the like.

  The laser beam emitted from the light source device 281 is reflected by the reflecting mirror 280. Each laser beam is guided to mirrors 282BK, 282M, 282C, and 282Y (hereinafter collectively referred to as “mirror 282”) by an optical system such as an fθ lens (not shown), and further, the photosensitive drums 109BK and 109M are further guided by an optical system ahead of the mirrors. , 109C, 109Y. That is, the reflecting mirror 280 and the mirror 282 function as a scanning unit.

  The reflecting mirror 280 is a hexahedral polygon mirror, and by rotating, the laser beam for one line in the main scanning direction can be scanned per polygon mirror surface. The optical writing device 111 according to this embodiment divides the four light source devices into light source devices of two colors of 281BK, 281M, and 281C, 281Y, and performs scanning using different reflecting surfaces of the reflecting mirror 280. It is possible to write on four different photosensitive drums at the same time with a more compact configuration than the scanning method using only one reflecting surface.

  In addition, a horizontal synchronization detection sensor 283 is provided in the vicinity of the scanning start position in the range where the laser beam is scanned by the reflecting mirror 280. When the laser beam emitted from the light source device 281 enters the horizontal synchronization detection sensor 283, the timing of the scanning start position of the main scanning line is detected, and the control device that controls the light source device 281 and the reflecting mirror 280 are synchronized. Be taken.

  In such an optical writing device, as described above, the laser beam is scanned in the entire main scanning direction by the rotation of the reflecting mirror 280. Since the reflecting mirror 280 is a hexahedron, the reflecting surface that reflects the laser beam is a flat surface, the distance from each part of the plane to the rotation axis is different, and the laser beam is scanned from one end to the other end of the main scanning line. During this time, the moving speed of the light spot that is the arrival point of the laser beam on the scanning surface (hereinafter referred to as “scanning speed”) changes. This change in scanning speed on the main scanning line, that is, correction of uneven scanning speed is the gist of the present embodiment. Note that the change in scanning speed may be caused not only by the difference in the optical path length of the light beam but also by the installation error of the mirror 282 and manufacturing tolerances.

  A problem caused by the above-described change in scanning speed will be described with reference to FIG. If the scanning speed is constant on the main scanning line, the interval between pixels is constant on the main scanning line as long as writing is performed with a constant pixel clock. However, when the scanning speed changes, if writing is performed with a constant pixel clock, the interval between pixels is wide in a range where the scanning speed is high, and the interval between pixels is narrow in a range where the scanning speed is slow. Therefore, it is necessary to correct the interval between pixels in accordance with the change in scanning speed.

  FIG. 6 is a diagram illustrating an example of the necessary correction amount according to the position of the main scanning line. In other words, information as shown in FIG. 6 is used as phase shift information for correcting the scanning speed to be substantially constant in the optical writing device 111. As shown in FIG. 6, when the scanning speed changes, the necessary correction amount changes according to the position of the main scanning line. The range of “a large amount of correction in the minus direction” shown in FIG. 6 is a range that needs to be corrected so that the interval between pixels is narrow, and is a range in which the scanning speed is faster than the reference speed. Further, since the correction amount is large, the difference between the scanning speed and the reference speed is large.

  On the other hand, the range of “a small amount of correction in the positive direction” is a range in which correction is necessary so that the interval between pixels is wide, and the scanning speed is a range slower than the reference speed. Further, since the correction amount is small, the difference between the scanning speed and the reference speed is small. In the present embodiment, the pixel interval is corrected to an appropriate interval by shifting the phase of the pixel clock, that is, changing the clock frequency based on the characteristics of the correction amount. The required correction amount characteristic as shown in FIG. 6 differs depending on the configuration of the optical system in the optical writing device 111.

  Next, a control block of the optical writing device 111 according to the present embodiment will be described with reference to FIG. FIG. 7 is a diagram illustrating a functional configuration of the optical writing device control unit 120 that controls the optical writing device 111 according to the present embodiment, and a relationship among the light source device 281, the horizontal synchronization detection sensor 283, and the pattern detection sensor 117.

  As shown in FIG. 7, the optical writing device control unit 120 according to the present embodiment includes a writing control unit 121, a counting unit 122, a sensor control unit 123, a correction value calculation unit 124, a reference value storage unit 125, and a correction value storage unit. 126. The optical writing device 111 according to the present embodiment includes information processing mechanisms such as the CPU 10, RAM 11, ROM 12, and HDD 14 as described in FIG. 1, and the optical writing device control unit 120 as shown in FIG. Similar to the controller 20 of the forming apparatus 1, a control program stored in the ROM 12 or the HDD 14 is loaded into the RAM 11, and the CPU 10 operates according to the control program.

  The writing control unit 121 controls the light source device 281 that is a writing light source in accordance with the synchronization detection signal from the horizontal synchronization detection sensor 283 based on the image information input from the engine control unit 31 of the controller 20. In addition to driving the light source device 281 based on the image information input from the engine control unit 31, the write control unit 121 also draws a pattern for correcting misalignment in the misalignment correction process described above. 281 is driven.

  The correction value generated as a result of this misalignment correction processing is stored in the correction value storage unit 126 shown in FIG. 7, and the write control unit 121 uses the light source based on the correction value stored in the correction value storage unit 126. The timing for driving the device 281 is corrected. Furthermore, the writing control unit 121 according to the present embodiment includes a function of correcting the scanning speed unevenness based on the phase shift information described in FIG.

  In the misregistration correction process, the count unit 122 starts counting at the same time when the writing control unit 121 controls the light source device 281 to start exposure of the photosensitive drum 109BK. The count unit 122 outputs a count value each time the sensor control unit 123 detects a pattern based on the output signal of the pattern detection sensor 117.

  As a result, in the above-described misregistration correction processing, the count unit 122 controls the light source device 281 to start the exposure of the photosensitive drum 109BK in the above-described misregistration correction process. It functions as a detection period counting unit that counts the detection period until a pattern is detected. Further, the count unit 122 counts the detection timings of the continuously drawn patterns in the positional deviation correction process for correcting the deviation of the toner images of the respective colors.

  The sensor control unit 123 is a control unit that controls the pattern detection sensor 117, and as described above, based on the output signal of the pattern detection sensor 117, the misalignment correction pattern formed on the transport belt 105 is a pattern. It is determined that the position of the detection sensor 117 has been reached. That is, the pattern detection sensor 117 and the sensor control unit 123 function as an image detection unit. When the sensor control unit 123 determines that the position deviation correction pattern has reached the position of the pattern detection sensor 117 as described above, the sensor control unit 123 inputs a detection signal to the count unit 122.

  The correction value calculation unit 124 calculates a correction value based on the reference value stored in the reference value storage unit 125 based on the count result by the counting unit 122. That is, the correction value calculation unit 124 functions as a reference value acquisition unit and a correction value calculation unit. FIG. 8 shows an example of reference values stored in the reference value storage unit 125. As shown in FIG. 8, the reference value storage unit 125 stores a writing start timing reference value and a drum interval reference value.

  The write start timing reference value is a period from when the write control unit 121 controls the light source device 281 to start exposure of the photosensitive drum 109BK to when the pattern detection sensor 117 detects a pattern for correcting misalignment. Is the reference value. That is, the correction value calculation unit 124 compares the write start count value with the write start timing reference value among the count values by the count unit 122, and calculates a correction value based on the difference between the two.

  The drum interval reference value is a reference value of the detection timing for each of the continuously drawn patterns as described above. That is, the correction value calculation unit 124 compares the drum interval count value with the drum interval reference value among the count values of the counting unit 122, and calculates a correction value based on the difference between the two.

  The correction value calculated in this way is stored in the correction value storage unit 126 as described above. Thus, by storing the correction value in the correction value storage unit 126, the writing control unit 121 can drive the light source device 281 with reference to the correction value.

  Further, the correction value storage unit 126 also stores phase shift information according to the gist of the present embodiment described above. Accordingly, the writing control unit 121 performs phase shift based on the phase shift information stored in the correction value storage unit 126, and corrects the scanning speed unevenness in the main scanning direction.

  Further, the correction value calculation unit 124 detects a detection error by the pattern detection sensor 117 with respect to the phase shift information in accordance with the detection result of the pattern for detecting the position in the main scanning direction among the patterns included in the pattern for correcting misalignment. Information to be displayed and information for correcting the phase shift information are generated. This is one of the gist according to the present embodiment.

  Next, the misregistration correction operation according to the present embodiment will be described with reference to FIG. FIG. 9 is a diagram showing marks (hereinafter referred to as “positional deviation correction marks”) drawn on the paper 104 by the light source device 281 controlled by the writing control unit 121 in the positional deviation correction operation according to the present embodiment. It is. As shown in FIG. 9, the misregistration correction mark 400 according to this embodiment includes a plurality of misregistration correction pattern rows 401 in which various patterns are arranged in the sub-scanning direction (this embodiment). 3) are arranged side by side. In FIG. 9, the solid line represents the pattern drawn by the photosensitive drum 109BK, the dotted line represents the photosensitive drum 109Y, the broken line represents the photosensitive drum 109C, and the alternate long and short dash line represents the pattern drawn by the photosensitive drum 109M.

  As shown in FIG. 9, the pattern detection sensor 117 has a plurality (three in the present embodiment) of sensor elements 170L, 170C, and 170R (hereinafter collectively referred to as “sensor elements 170”) in the main scanning direction. Each misalignment correction pattern row 401 is drawn at a position corresponding to each sensor element 170. Accordingly, the optical writing device control unit 120 can detect a pattern at a plurality of positions in the main scanning direction, and can improve the accuracy of the misregistration correction operation by calculating each average value. .

  As shown in FIG. 9, the positional deviation correction pattern row 401 includes a start position correction pattern 411 and a drum interval correction pattern 412. Further, as shown in FIG. 9, the drum interval correction pattern 412 is repeatedly drawn. The start position correction pattern 411 is a pattern drawn in order to count the write start count value described above. The start position correction pattern 411 is also used for correcting the detection timing when the sensor control unit 123 detects the drum interval correction pattern 412.

  As shown in FIG. 9, the start position correction pattern 411 according to the present embodiment is a line transferred from the photosensitive drum 109BK and parallel to the main scanning direction. In the start position correction using the start position correction pattern 411, the optical writing device control unit 120 performs a write start timing correction operation based on the read signal of the start position correction pattern 411 by the pattern detection sensor 117. In other words, the writing start timing reference value stored in the reference value storage unit 125 is the same as the drawn black after the light source device 281 starts drawing the black pattern on the photosensitive drum 109BK in the start position correction pattern 411. This value is a reference value for the period until the pattern is read by the pattern detection sensor 117 and detected by the sensor control unit 123.

  As the name suggests, the drum interval correction pattern 412 is a pattern drawn to count the drum interval count value described above. As shown in FIG. 9, the drum interval correction pattern 412 includes a sub-scanning direction correction pattern 413 and a main scanning direction correction pattern 414. The optical writing device control unit 120 corrects the positional deviation in the sub-scanning direction of each of the photosensitive drums 109BK, 109M, 109C, and 109Y based on the reading signal of the sub-scanning direction correction pattern 413 by the pattern detection sensor 117. Based on the read signal of the scanning direction correction pattern 414, the positional deviation correction of each photosensitive drum in the main scanning direction is performed.

  That is, the drum interval reference value stored in the reference value storage unit 125 is the drum interval correction value that is drawn after the light source device 281 starts drawing the drum interval correction pattern 412 under the control of the writing control unit 121. Each line included in the pattern 412 for use is a value serving as a reference for a period until the line is read by the pattern detection sensor 117 and detected by the sensor control unit 123.

  Further, the drum interval correction pattern 412 is also used as a pattern for detecting uneven scanning speed in the main scanning direction. The principle of detection of uneven scanning speed according to the present embodiment will be described with reference to FIGS. FIG. 10A is a diagram illustrating a state of the drum interval correction pattern 412 in a state where the speed unevenness does not occur.

  Since black has no detection error due to diffused light and can be detected with higher accuracy, in the detection of uneven speed according to the present embodiment, the photosensitive drum 109BK, the photosensitive drum 109Y, the photosensitive drum 109C, Of the patterns drawn by each of the photosensitive drums 109M, a pattern drawn by the photosensitive drum 109BK, that is, a black pattern is used.

  In the detection of the speed unevenness according to the present embodiment, as shown in FIG. 10A, the correction value calculation unit 124 detects the sub-scanning direction correction pattern 413 in each sensor element 170 and then performs the main scanning direction. The period until the correction pattern 414 is detected is measured. When the speed unevenness does not occur, as shown in FIG. 10A, the detection periods P1, P2, and P3 in each sensor element 170 are the same.

  FIG. 10B is a diagram illustrating a state of the drum interval correction pattern 412 when the scanning speed is generally high. When the scanning speed is fast, as shown in FIG. 10B, the pattern corresponding to each sensor element 170 is further advanced in the main scanning direction than the state of FIG. 10A (on the right side in the drawing). Will be drawn. On the other hand, since the position of each sensor element 170 does not change, the detection period P2 detected by the sensor element 170C is longer than the detection period P1 detected by the sensor element 170L, and the detection detected by the sensor element 170R. The period P3 is longer than the detection period P2 detected by the sensor element 170C. The correction value calculation unit 124 measures the scanning speed unevenness based on the difference between the detection periods P1, P2, and P3. That is, the correction value calculation unit 124 functions as a scanning speed unevenness calculation unit.

  FIG. 10C is a diagram showing the state of the drum interval correction pattern 412 when the necessary correction amount is in the state shown in FIG. As shown in FIG. 6, on the left side of the range in the main scanning direction, since the correction amount is large in the minus direction, the scanning speed is larger than the standard scanning speed. Accordingly, as shown in FIG. 10C, the drum interval correction pattern 412 corresponding to the sensor element 170C is drawn on the start position side (left side in the drawing) in the main scanning direction from the standard position, and the sensor element The detection period P2 in 170C is shorter than the detection period P1 in the sensor element 170L.

  On the other hand, as shown in FIG. 6, on the right side of the range in the main scanning direction, the correction amount is small in the plus direction. However, the correction amount in the left side of the main scanning range is negated as the entire main scanning range. It is not a correction amount. Accordingly, as shown in FIG. 10C, the detection period P3 in the sensor element 170R is longer than the detection period P2 in the sensor element 170C, but is shorter than the detection period P1 in the sensor element 170L and corresponds to the sensor element 170C. The drum interval correction pattern 412 is still drawn on the start position side (left side in the drawing) in the main scanning direction from the standard position.

  As described above, the correction value calculation unit 124 according to the present embodiment measures the scanning speed unevenness based on the difference between the detection periods P1, P2, and P3 in each sensor element 170, and the scanning speed unevenness is corrected. A correction value, that is, phase shift information is generated.

  Next, the information format of the phase shift information according to the present embodiment will be described with reference to FIG. FIG. 11 is a diagram showing the positional relationship in the main scanning direction with the sensor element 170 included in the graph of the necessary correction amount in FIG. 6 and the pattern detection sensor 117 in addition to the phase shift information according to the present embodiment. As shown in FIG. 11, in the present embodiment, the entire range in the main scanning direction is divided into eight areas, and a correction amount is set for each area.

  Here, as shown in FIG. 11, the sensor element 170L is located between the area 1 and the area 2, the sensor element 170C is located between the area 4 and the area 5, and the sensor element 170R is the area 7 and area 8. Therefore, the difference between the detection period P2 and the detection period P1 described above indicates the scanning speed between the area 2 and the area 4. For example, if the scanning speed between the area 2 and the area 4 is slower than the standard, the detection period P2 becomes longer than the detection period P1. As a result, a correction value in the minus direction is set from area 2 to area 4.

  The uneven scanning speed by the optical writing device 111 is a variation in the speed at which the laser beam reflected by the reflecting mirror 280 scans on the photosensitive drum 109, and thus cannot be measured by the optical writing device 111 alone. Measurement is possible only after being incorporated into the image forming apparatus 1. When the image forming apparatus 1 is shipped, after the optical writing device 111 is incorporated, the scanning speed unevenness is measured by a dedicated jig in each image forming apparatus 1, and the phase shift as shown in FIG. 11 is performed. A correction amount setting value is generated and stored in the correction value storage unit 126. Therefore, immediately after the image forming apparatus 1 is shipped and the operation is started at the delivery destination, the scanning speed unevenness is preferable by performing the phase shift based on the preset value of the phase shift correction amount. An image having no distortion corrected in the above is formed.

  However, when the image forming apparatus 1 is operated at the delivery destination, the optical system changes with time, the knitting core of the reflecting mirror, etc., and the scanning speed unevenness may change from the pre-shipment mode. In this case, the changed scanning speed unevenness cannot be suitably corrected with the preset value of the phase shift amount.

  Therefore, it is preferable to update the set value of the phase shift amount for correcting the scanning speed unevenness according to the change with time of the image forming apparatus 1, but the phase shift amount is updated by connecting a dedicated jig each time. However, there are problems such as an increase in apparatus management cost, downtime while the jig is connected, and an increase in apparatus cost due to an interface for updating and storing phase shift information.

  In order to solve this problem, it is conceivable to update the phase shift information in accordance with the detection result of the position shift correction pattern by the pattern detection sensor 117 provided for detecting the position shift correction pattern. However, since the measurement result by the pattern detection sensor 117 includes a tolerance at the time of assembling the pattern detection sensor 117 to the image forming apparatus 1, high-precision scanning speed unevenness such as the dedicated jig described above is included. It is difficult to make a measurement.

  Therefore, the optical writing device 111 according to the present embodiment forms an image without distortion by using the phase shift amount generated based on the measurement result by a dedicated jig, such as immediately after the start of operation of the device. In a state in which is guaranteed, a pattern as shown in FIG. 9 is drawn. Then, the phase shift amount generated based on the detection result of the pattern is stored as the detection tolerance of the pattern detection sensor 117. Thereafter, when the set value of the phase shift amount is corrected based on the detection result of the pattern detection sensor 117, the correction is performed after subtracting the stored detection tolerance.

  This is because, immediately after the start of operation of the apparatus, etc., the phase shift amount is generated based on the measurement result by the dedicated jig, so a suitable pattern without uneven scanning speed should be formed, When the unevenness in the scanning speed is confirmed based on the result of detecting the pattern by the pattern detection sensor 117, the unevenness in the scanning speed is based on the idea that the detection tolerance of the pattern detection sensor 117 is equivalent. Accordingly, it is possible to correct the phase shift amount with high accuracy by using a sensor provided for detecting the misregistration correction pattern. Hereinafter, details of the correction of the phase shift amount according to the present embodiment will be described.

  FIG. 12 is a diagram showing information included in the phase shift information according to the present embodiment. As shown in FIG. 12, the phase shift information according to the present embodiment includes “phase shift reference information”, “phase shift sensor tolerance information”, and “phase shift correction value information”. As described above, the “phase shift reference information” is generated based on the measurement result obtained by measuring the unevenness of the scanning speed with a dedicated jig while the optical writing device 111 is incorporated in the image forming apparatus 1. This is information on the amount of phase shift. That is, the correction value storage unit 126 also functions as a phase shift reference information storage unit.

  The phase shift sensor tolerance information has the same information format as the information of the phase shift correction amount described in FIG. 11 and is information indicating the detection tolerance by the pattern detection sensor 117. Storing this phase shift sensor tolerance information is one of the gist according to the present embodiment. With reference to FIG. 13, the generation | occurrence | production aspect of the phase shift sensor tolerance information which concerns on this embodiment is demonstrated.

  When generating the phase shift sensor tolerance information according to the present embodiment, first, as described with reference to FIGS. 10A to 10C, the positional deviation correction pattern including the drum interval correction pattern 412 is drawn. Measurement of the detection periods P1, P2, and P3 is performed. At this time, when the pattern is drawn, the phase shift using the above-described phase shift reference information is executed. For this reason, the actually drawn image is a distortion-free image in which the scanning speed unevenness is suitably corrected.

  In this case, the detection periods P1, P2, and P3 should all be the same value. However, as described above, since the pattern detection sensor 117 has a detection tolerance, the detection periods P1, P2, A difference occurs in the value of P3. That is, the difference in the values of the detection periods P1, P2, and P3 measured in the pattern drawn by applying the phase shift reference information is a value indicating the detection tolerance of the pattern detection sensor 117.

  As described above, the difference between the detection period P1 and the detection period P2 corresponds to the scanning speed between the area 2 and the area 4, and the difference between the detection period P2 and the detection period P3 is between the area 5 and the area 7. This corresponds to the scanning speed of. Therefore, by calculating the difference between the detection period P1 and the detection period P2 and the difference between the detection period P2 and the detection period P3, as shown as “sensor measurement value” in FIG. And the total correction value of area 5 to area 7 are calculated. This calculation is performed by the correction value calculation unit 124.

  When this “sensor measurement value” is calculated, the correction value calculation unit 124 equally divides each sensor measurement value for each area, thereby calculating correction values in the areas 2 to 4 and the areas 5 to 7. . In the example of FIG. 13, since the total correction value in areas 2 to 4 is “+40”, the correction values in area 2 to area 4 are calculated to be “+13” by rounding off the decimals. Further, since the total correction value in areas 5 to 7 is “−10”, the correction values in area 5 to area 7 are calculated to be “−3” by rounding off the decimals.

  Further, for area 1 and area 8, the absolute value of the correction values calculated for areas 2 to 4 and the absolute value of the correction values calculated for areas 5 to 7 are ½ and adjacent. A correction value having the same sign as the area to be set is set. By such a calculation method, it is possible to adjust the magnification in the entire main scanning direction. In the present embodiment, “+8” is set in area 1, and “−8” is set in area 8. By such processing, a “sensor tolerance value” is calculated as shown in FIG. In addition, you may set the same correction value as the correction value calculated about area 2-4 and area 5-7, respectively. This “sensor tolerance value” is stored as phase shift sensor tolerance information. That is, the correction value calculation unit 124 and the correction value storage unit 126 function as a detection tolerance storage unit. In the example of FIG. 13, the “sensor measurement value” and the “sensor tolerance value” are values for canceling the tolerance of the pattern detection sensor 117. That is, the sign of the tolerance value of the pattern detection sensor 117 is positive or negative.

  Thus, the phase shift sensor tolerance information is information indicating the detection tolerance by the pattern detection sensor 117. Therefore, it is not used at the time when the image is suitably drawn by the phase shift based on the phase shift reference information, such as immediately after shipment of the image forming apparatus 1. However, in order to calculate the phase shift sensor tolerance information, it is necessary that at least the scanning speed is suitably corrected and the image is suitably formed. Therefore, scanning is performed using only the phase shift reference information before shipment or immediately after shipment. It is necessary to calculate phase shift tolerance information at a timing at which the speed unevenness is suitably corrected.

  The phase shift correction value information is used at the delivery destination after the image forming apparatus 1 is shipped, and the phase shift reference information is used when the phase shift reference information cannot suitably correct the scanning speed unevenness due to the above-described change over time. This is a value for preferably correcting unevenness in scanning speed by correcting. The phase shift correction value information is also in the same information format as the phase shift correction amount information described in FIG. With reference to FIG. 14, the generation | occurrence | production aspect of the phase shift correction value information which concerns on this embodiment is demonstrated.

  When generating the phase shift correction value information according to the present embodiment, similarly to the generation of the phase shift sensor tolerance information, after the phase shift using the above-described phase shift reference information is executed, the drum interval correction pattern 412 is displayed. The detection periods P1, P2, and P3 are measured by drawing a pattern for correcting misregistration. Accordingly, as shown as “sensor measurement value” in FIG. 14, the correction value calculation unit 124 converts the total correction value of area 2 to area 4 and the total correction value of area 5 to area 7 into the correction value calculation unit 124. Is calculated by Further, the correction value calculation unit 124 calculates a correction value for each area indicated as “sensor measurement difference value” in FIG. 14 by the same method as the “sensor tolerance value” calculation method described in FIG.

  In principle, this “sensor measurement difference value” is a value for correcting the phase shift reference value, but the “sensor measurement difference value” is a detection period P1, P2, which is detected by the pattern detection sensor 117, Since the value is calculated based on P3, the detection tolerance of the pattern detection sensor 117 is included. Accordingly, the correction value calculation unit 124 obtains a correction value excluding the detection tolerance of the pattern detection sensor 117 by applying the “sensor tolerance value” to the “sensor measurement difference value”.

  After calculating the “sensor measurement difference value”, the correction value calculation unit 124 applies the already calculated and stored “sensor tolerance value”, that is, the phase shift sensor error information to FIG. The “correction difference value” shown is obtained. The “correction difference value” is a value obtained by subtracting the “sensor tolerance value” from the “sensor measurement difference value”. In this case, whether to perform addition or subtraction differs depending on the setting of the sign of “sensor tolerance value” and “sensor measurement difference value”. In this embodiment, the “sensor tolerance value” is a value for canceling the tolerance of the pattern detection sensor 117, and the “sensor measurement difference value” is a value for correcting the scanning speed unevenness. Used.

  In this way, the “correction difference value” is calculated and stored as “phase shift correction value information” shown in FIG. After the “phase shift correction value information” is generated, when image formation is executed in the image forming apparatus 1, based on the “phase shift reference information” and the “phase shift correction value information”, FIG. As a “phase shift update value”, a value that is actually used as a phase shift amount is calculated.

  As described above, in the optical writing device mounted on the image forming apparatus 1 according to the present embodiment, an image without distortion in which unevenness in scanning speed is suitably corrected immediately after completion of adjustment before shipment or immediately after shipment. In the drawn state, the scanning speed unevenness is measured based on the detection result by the pattern detection sensor 117, and the measured scanning speed unevenness is stored as the detection tolerance of the pattern detection sensor 117. Then, after the image forming apparatus 1 is started to operate, when the scanning speed unevenness is measured by the pattern detection sensor 117, the stored detection tolerance is subtracted from the measured scanning speed unevenness. As a result, in the operating state of the image forming apparatus 1, it is possible to realize the update of the phase shift information, which is information for modulating the pixel clock in order to correct the scanning speed unevenness in the optical writing device, with high accuracy and at low cost. It becomes.

  Such generation of phase shift correction value information can be used, for example, when the optical writing device 111 is replaced. As described above, the scanning speed unevenness by the optical writing device 111 cannot be measured by the optical writing device 111 alone, but can be measured only after the optical writing device 111 is incorporated in the image forming apparatus 1. That is, when the optical writing device 111 is replaced, the generated scanning speed unevenness is also different, so it is necessary to update the phase shift information.

  However, if the phase shift reference information is updated by connecting a dedicated jig for exchanging the optical writing device 111, problems of operation cost and downtime occur as described above. Here, by using the “phase shift sensor error information” according to the present embodiment, even when the optical writing device 111 is replaced, it is possible to cope with uneven scanning speed in the optical writing device 111 after replacement. The phase shift correction amount can be calculated with high accuracy using the pattern detection sensor 117.

  The replacement of the optical writing device 111 according to the present embodiment indicates that the part constituted by the optical system shown in FIGS. 4 and 5 is replaced, and the optical writing device control unit 120 shown in FIG. 7 is not replaced. . Therefore, the information shown in FIG. 8 and the information shown in FIG. 12 remain after the optical writing device 111 is replaced, and can be used in the optical writing device 111 after replacement.

  An update mode of the phase shift information when the optical writing device 111 is replaced will be described with reference to FIG. “Phase shift reference value” and “sensor tolerance value” shown in FIG. 14 are values used in the optical writing device 111 before replacement. Even when the optical writing device 111 is replaced, detection periods P1 and P2 are generated by drawing a pattern for correcting misregistration including a drum interval correcting pattern 412 after performing phase shift using phase shift reference information. , P3 is measured.

  Here, as described above, the “phase shift reference information” is a correction value corresponding to the scanning speed unevenness measured by the dedicated jig for the optical writing device 111 before replacement, and is stored in the optical writing device 111 after replacement. It is not the corresponding value. However, if the same type of optical writing device 111 is used before and after replacement, the configuration as described in FIGS. 4 and 5 is the same, and the resulting tendency of uneven scanning speed, that is, as described in FIG. The curve tendency of the curve is similar.

  In the present embodiment, as illustrated in FIGS. 10A to 10C and the like, the entire range in the main scanning direction is corrected using the three sensor elements 170, and thus as described with reference to FIGS. In addition, detailed values cannot be measured for each of the eight areas. On the other hand, as described above, by using the phase shift reference value, which is a correction value measured in detail in the same type of optical writing apparatus, first, a rough match with the tendency of uneven scanning speed in the entire main scanning direction is provided. Correction can be performed. Then, the adjustment required when the optical writing device 111 is replaced is performed based on the detection result by the pattern detection sensor 117, thereby increasing the sensor element 170, that is, increasing the device cost and increasing the sensor output. The phase shift correction amount can be suitably updated while avoiding the complication of the sensor control unit 123 due to this.

  After the replacement, the correction value calculation unit 124 performs “sensor measurement value” shown in FIG. 14 by drawing the pattern by the optical writing device 111 after replacement and measuring the detection periods P1, P2, and P3 based on the detection result by the pattern detection sensor 117. A “sensor measurement difference value” is calculated. Since this “sensor measurement difference value” includes the detection tolerance of the pattern detection sensor 117 in addition to the unevenness of the scanning speed due to the replacement of the optical writing device 111, the correction value calculation unit 124 performs the process shown in FIG. In the same manner as described above, “correction difference value” is obtained by applying “sensor tolerance value”.

  This “correction difference value” is used as “phase shift correction value information”, which is a value for correcting the “phase shift reference value” in order to cope with uneven scanning speed by the optical writing device 111 after replacement. Therefore, when drawing is performed by the optical writing device 111 after replacement, the value obtained by subtracting “phase shift correction value information” from “phase shift reference information” as shown as “phase shift update value” in FIG. Based on this, a phase shift is performed.

  Next, the timing for generating or updating the phase shift correction value information shown in FIG. 12, that is, the timing for adjusting the scanning speed unevenness in the image forming apparatus 1 according to the present embodiment will be described. As described with reference to FIG. 14, the generation of the phase shift correction value information according to the present embodiment is executed by drawing the misregistration correction mark 400 as described with reference to FIG. It is also possible to execute the correction simultaneously with the positional deviation correction.

  However, the frequency at which the scanning speed unevenness needs to be adjusted is lower than the frequency at which the positional deviation correction is required. This is because the variation in the characteristics of the scanning speed unevenness due to the change of the reflecting mirror 280 included in the optical writing device 111 with time is compared to the positional deviation of the image forming position and the color deviation of the photosensitive drum 109 of each color. This is because it is moderate. Therefore, the optical writing device control unit 120 according to the present embodiment generates or updates phase shift correction value information only when a predetermined condition is met, and adjusts the scanning speed unevenness.

  FIG. 15 is a diagram illustrating timing at which the optical writing device control unit 120 according to the present embodiment executes adjustment of scanning speed unevenness. As shown in FIG. 15, when the optical system described in FIGS. 4 and 5 is replaced, the optical writing device control unit 120 according to the present embodiment performs image processing every time the number of image forming outputs reaches a predetermined number. Each time the operation period of the forming apparatus 1 reaches a predetermined period, every time the travel distance of the conveyor belt 105 reaches a predetermined distance, the amount of change in environmental temperature exceeds a threshold value, and the offset values of the detection periods P1, P2, and P3 Is executed when the threshold is exceeded.

  The information shown in FIG. 15 is stored in the correction value calculation unit 124, and the correction value calculation unit 124 performs the positional deviation correction by drawing the positional deviation correction mark 400 shown in FIG. If any one of the conditions shown in FIG. 15 is satisfied, the phase shift correction value information is generated or updated. Here, among the conditions shown in FIG. 15, the case where the difference between the offset values exceeds the threshold will be described below.

  Since the positional deviation correction in the main scanning direction is also performed in the normal positional deviation correction by drawing the positional deviation correction mark 400, the detection periods P1 and P2 as described with reference to FIGS. , P3 is measured even when the phase shift correction value information is not updated. Accordingly, the “sensor measurement value” and “sensor measurement difference value” shown in FIG. 14 can be calculated regardless of whether or not the phase shift correction value information is updated.

  The correction value calculation unit 124 acquires the “sensor measurement difference value” shown in FIG. 14 in the normal positional deviation correction process, and applies the stored sensor tolerance value. That is, the offset value is calculated by subtracting the “sensor measurement tolerance value” from the “sensor measurement difference value”. If the offset value calculated as a result exceeds a predetermined threshold value, the current scanning speed unevenness correction value means that the scanning speed unevenness is not suitably corrected. The calculated offset value is directly used as the “correction difference value” and stored as phase shift correction value information.

  In the above embodiment, as described with reference to FIGS. 10A to 10C, the period from when the sub-scanning direction correction pattern 413 is detected to when the main scanning direction correction pattern 414 is detected. The case where “sensor measurement values” are obtained by measuring the detection periods P1, P2, and P3 and calculating the difference between them is described as an example. In addition, even if the difference in timing at which the main scanning direction correction pattern 414 is detected in each of the sensor elements 170L, 170C, and 170R, the same value as the “sensor measurement value” can be obtained.

  Further, in the above embodiment, “correction difference value” shown in FIG. 14 is stored as “phase shift correction value information”, and “phase shift reference value” is set to “correction difference” at the time of image formation output. The case where correction is performed using the “value” has been described as an example. In addition, the “phase shift update value” shown in FIG. 14 may be stored as “phase shift correction value information”, and the “phase shift update value” may be used as it is at the time of image formation output.

  Further, the pattern detection sensor 117 may be replaced by operating the image forming apparatus 1. In such a case, the detection tolerance by the pattern detection sensor 117 after replacement is different from the value before replacement. Therefore, it is necessary to regenerate already stored phase shift sensor tolerance information.

  In this case, the correction value calculation unit 124 calculates the sensor tolerance value by the same processing as the processing described in FIG. 13, thereby generating phase shift sensor tolerance information. At this time, since the image forming apparatus 1 is operated to such an extent that the pattern detection sensor 117 needs to be replaced, the characteristics of uneven scanning speed by the optical writing device 111 change immediately after shipment, and phase shift correction value information is generated. It is thought that it is done.

  As described above, when generating the phase shift sensor tolerance information according to the present embodiment, it is premised that the misregistration correction mark 400 is formed as a distortion-free image in which the scanning speed unevenness is corrected. Therefore, when exchanging the pattern detection sensor 117 and exchanging the phase shift sensor tolerance information, the phase shift correction value information used until immediately before is applied to the phase shift reference information, and the misalignment correction mark 400 is used. Is drawn. Thereby, a detection tolerance can be suitably measured about the pattern detection sensor 117 after replacement | exchange by the process similar to the above.

  Moreover, in the said embodiment, as demonstrated in FIG. 13, FIG. 14, about the area 1 and the area 8 which are the area | regions outside the sensor element 170L and the sensor element 170R, the correction value calculated about the areas 2-4 As an example, a case where a correction value having the same sign as that of an adjacent area, which is ½ of the sum of the absolute value of the above and the absolute value of the correction values calculated for the areas 5 to 7 is used has been described. In addition, it is possible to use the same value as the values set for the adjacent areas 2 and 7, or use the difference between the areas 2 to 4 and the areas 5 to 8.

  Further, in the above embodiment, as described with reference to FIG. 10, the scanning speed in the region between the respective sensors is determined by obtaining the difference between the detection periods P1, P2, and P3 detected by the respective sensor elements 170. The case of determination has been described as an example. In addition, instead of comparing the detection periods with each other, the scanning speed at the position where each sensor element 170 is provided may be determined by comparing the detection period with a predetermined reference value. Here, the reference value is a reference value from when the pattern detection sensor 117 detects the sub-scanning direction correction pattern 413 to the main scanning direction correction pattern 414, and the scanning speed is a pixel. It is equal to the value of the detection period when the speed is accurate corresponding to the clock.

  For example, if the detection period P1 is shorter than the reference value, it is determined that the scanning speed is higher than the standard at the point of the sensor element 170L. In other words, in the area 1, it is determined that the scanning speed is faster than the standard. As a result, a finer correction amount can be set also in areas outside the sensor element 170 such as area 1 and area 8.

1 image forming apparatus,
10 CPU,
11 RAM,
12 ROM,
13 engine,
14 HDD,
15 I / F,
16 LCD,
17 Operation part,
18 Bus,
20 controller,
21 ADF,
22 Scanner unit,
23 Output tray,
24 display panels,
25 Paper feed table,
26 print engine,
27 Output tray,
28 Network I / F,
30 Main control unit,
31 engine control unit,
32 Input / output control unit,
33 Image processing unit,
34 Operation display control unit,
101 paper feed tray,
102 paper feed roller,
103 separation roller,
104 paper,
105 Conveyor belt,
106BK, 106C, 106M, 106Y Image forming unit,
107 driving roller,
108 driven roller,
109BK, 109C, 109M, 109Y photosensitive drum,
110BK charger,
111 optical writing device,
112BK, 112C, 112M, 112Y Developer,
113BK, 113C, 113M, 113Y
115BK, 115C, 115M, 115Y transfer device,
116 fixing device,
117 pattern detection sensor,
120 optical writing device controller,
121 light emission control unit,
122 counting part,
123 sensor control unit,
124 correction value calculation unit,
125 reference value storage unit,
126 correction value storage unit,
280 reflector,
281,281BK, 281Y, 281M, 281C Light source device,
282, 282BK, 282Y, 282M, 282C Mirror 283 Horizontal synchronization detection sensor

JP 2007-203739 A JP 2003- 211723 A JP 2008-299311 A

Claims (9)

An image forming apparatus including an optical writing device that irradiates a light beam to form an electrostatic latent image on a photoreceptor,
A scanning unit that guides a light beam emitted from a light source onto the photosensitive member and scans the photosensitive member;
A phase shift that stores phase shift reference information that serves as a reference for correcting unevenness in scanning speed, which is a change on the scanning line of the scanning speed of the light beam guided by the scanning unit. A reference information storage unit;
A writing control unit that controls the light source while irradiating the light beam while correcting the scanning speed unevenness according to the phase shift reference information based on image information that is information of an image to be formed as the electrostatic latent image;
Conveyance in which an image for detecting unevenness in scanning speed formed by developing the electrostatic latent image formed by the light beam irradiated in accordance with control by the writing control unit moves relative to the photoreceptor. An image detector that is conveyed by the body and detects that it has reached a predetermined position;
A scanning speed unevenness calculating unit that calculates the scanning speed unevenness based on the detection result of the image for detecting the unevenness of the scanning speed;
A detection tolerance storage unit that stores the calculated scanning speed unevenness as information indicating a detection tolerance of the image detection unit;
When the scanning unit is replaced , the phase shift is applied by applying the stored detection tolerance to the scanning speed unevenness calculated by forming and detecting the image for detecting the unevenness in scanning speed. An image forming apparatus comprising: a correction value calculation unit that generates phase shift correction information for correcting information. The image for detecting uneven scanning speed is an image including a line inclined with respect to the sub-scanning direction,
The image detection unit detects that the image for detecting unevenness in scanning speed has reached a predetermined position at a plurality of points in the main scanning direction,
The scanning speed unevenness calculation unit calculates the scanning speed unevenness based on a difference in timing when the image for detecting the unevenness in scanning speed is detected at a plurality of points in the main scanning direction. Image forming apparatus. The phase shift information is information in which a scanning range in the main scanning direction is divided into a plurality of regions, and a phase shift amount is set for each region,
The calculated scanning speed unevenness is information in which the amount of change in scanning speed is set for each of the plurality of regions,
The scanning speed unevenness calculation unit calculates an amount of change in scanning speed between the two points based on a difference in timing at which the image for detecting unevenness in scanning speed is detected at two points in the main scanning direction. The scanning speed unevenness is calculated by allocating the calculated amount of change in the scanning speed to the plurality of regions included between the two points to obtain the amount of change in the scanning speed for each region. The image forming apparatus according to claim 2 . The scanning speed unevenness calculation unit equally divides the calculated amount of change in the scanning speed between the two points by the number of the plurality of areas included between the two points, to each of the plurality of areas. The image forming apparatus according to claim 3, wherein the image forming apparatus is assigned . The scanning speed unevenness calculation unit includes a point of the end portion in a region outside the end point in the main scanning direction at the point where the image for detecting the unevenness of scanning speed is detected among the plurality of regions. 5. The image forming apparatus according to claim 3, wherein the unevenness of the scanning speed is calculated by setting a value calculated based on a change amount of the scanning speed calculated for the inner region . The unevenness calculation unit for scanning speed is assigned to an adjacent region in the region outside the end point in the main scanning direction at the point where the image for detecting unevenness in scanning velocity is detected among the plurality of regions. 6. The image forming apparatus according to claim 5 , wherein the unevenness of the scanning speed is calculated by setting the change amount of the scanning speed. Image for detecting the scan velocity unevenness any claims 1 to 6, characterized in that by the optical writing device is an image for correcting the position of the electrostatic latent image formed on said photosensitive member The image forming apparatus described in 1. The scanning speed unevenness detection image is used to correct a positional deviation when the electrostatic latent images formed on the plurality of photosensitive members are developed and transferred to the same transfer object by the optical writing device. The image forming apparatus according to claim 7 , wherein the image forming apparatus is an image. A control program for an image forming apparatus including an optical writing device that irradiates a light beam to form an electrostatic latent image on a photoreceptor,
Scanning in which a light beam guided by a scanning unit that guides a light beam emitted from a light source onto the photosensitive member and scans the photosensitive member is a change on a scanning line at a speed of scanning the photosensitive member. Obtaining phase shift information serving as a reference for correcting the speed unevenness;
Irradiating a light beam by controlling a light source based on image information which is information of an image to be formed as the electrostatic latent image while correcting the scanning speed unevenness according to the phase shift information;
An image for detecting unevenness in scanning speed formed by developing the electrostatic latent image formed by the light beam irradiated according to the control is transported by a transport body that moves relative to the photoconductor. Detecting that a predetermined position has been reached;
Calculating the scanning speed unevenness based on a detection result of the image for detecting the scanning speed unevenness;
Storing the calculated scanning speed unevenness as information indicating a detection tolerance of the image detection unit;
When the scanning unit is replaced , the phase shift is applied by applying the stored detection tolerance to the scanning speed unevenness calculated by forming and detecting the image for detecting the unevenness in scanning speed. A control program for an image forming apparatus, characterized by causing the image forming apparatus to execute a step of generating phase shift correction information for correcting information.

Images