JP6160342B2 - Optical writing control apparatus, image forming apparatus, and optical writing apparatus control method - Google Patents

Description

  The present invention relates to an optical writing control apparatus, an image forming apparatus, and an optical writing apparatus control method, and more particularly, to a configuration of a pattern drawn for image drawing position correction.

  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 such an electrophotographic image forming apparatus, the image is formed in the correct range of the paper by aligning the timing of drawing the electrostatic latent image by exposing the photosensitive member and the timing of transporting the paper. Adjustments are made. 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. Is done. Hereinafter, these adjustment processes are collectively referred to as misalignment correction.

  As a specific method for realizing the above-described misregistration correction, a mechanical adjustment method for adjusting the positional relationship between the light source for exposing the photoconductor and the photoconductor, and an image to be output in the misalignment. There is a method by image processing in which an image is finally formed at a suitable position by adjusting accordingly. In the case of this image processing method, a correction pattern is drawn and read so that correction is performed based on the difference between the timing determined by design and the timing at which the pattern is actually read. An image is formed.

  Further, in the above-described image processing method, a technique for improving reading accuracy by a sensor that reads a correction pattern has been proposed (for example, see Patent Document 1). In Patent Document 1, a correction pattern drawn with a margin with respect to a reading range by a reading sensor, that is, a correction pattern drawn large so as not to interfere with reading even if a positional deviation occurs. After performing the correction based on the above, a correction pattern drawn in a size corresponding to the reading range by the reading sensor is drawn and the correction process is performed again. Thereby, in the correction process performed again, the influence of the diffuse reflected light from the extra drawn part can be eliminated, and a highly accurate correction process can be performed.

  As disclosed in Patent Document 1, when the correction pattern is drawn with a size corresponding to the reading range by the reading sensor, the size of the drawn pattern is simply reduced, which means that toner consumption is reduced. An effect can also be obtained. In order to increase this effect, it is required to reduce the correction pattern drawn with a margin with respect to the reading range by the reading sensor as much as possible.

  On the other hand, when there is no margin for the correction pattern drawing range relative to the reading range of the reading sensor, there is a high possibility that the correction pattern is not normally detected. When the correction pattern is not normally detected, the parameter to be corrected by the correction pattern is not normally corrected, and there is a demerit that normal device operation is hindered. In other words, there is a trade-off between the reduction in toner consumption described above and the accuracy of apparatus operation by normal detection of the correction pattern.

  In the technique disclosed in Patent Document 1, a specific procedure in a case where reading of a correction pattern (hereinafter referred to as “narrow pattern”) drawn in a size corresponding to a reading range by a reading sensor fails. Is not disclosed. If a narrow-width pattern reading fails and a pattern with sufficient margin is drawn each time, the time required for misregistration correction and the amount of toner consumed will increase excessively.

  The present invention has been made in consideration of the above circumstances, and reduces the amount of toner consumed for the correction pattern drawing and the time required for the correction operation while maintaining the accuracy of the image drawing position in the image forming apparatus. The purpose is to realize shortening.

In order to solve the above-described problems, one embodiment of the present invention is an optical writing control device that controls a light source that exposes a photoconductor to form an electrostatic latent image on the photoconductor, and is provided for each different color. A plurality of light sources, each of which controls light emission based on information of pixels constituting an image to be imaged and output, and exposes a plurality of the photoconductors provided for different colors, and on the photoconductor A detection signal acquisition unit that acquires a detection signal of a sensor that detects the image in a conveyance path in which an image in which the electrostatic latent image formed on the image is developed and transferred is formed on each of the plurality of photoconductors; Based on the detection signal detected by the sensor, a correction pattern for correcting the overlapping position where the developer images of different colors developed from the developed electrostatic latent image are superimposed is used to determine the overlapping position. to correct Anda correction value calculation unit for calculating a correction value of order, the correction pattern is a parallel pattern in the main scanning direction in the main scanning direction of the width in the main scanning direction of the detection range of the sensor width A horizontal pattern having a width corresponding thereto and a diagonal pattern having a width inclined in the main scanning direction and having a width corresponding to the width in the main scanning direction of the detection range of the sensor. A plurality of patterns are included at different positions in the sub-scanning direction in the correction pattern, the positions of the plurality of horizontal patterns in the main scanning direction are different from each other, and the oblique line pattern is in the sub-scanning direction in the correction pattern. and contains multiple different positions, different main scanning direction positions of the plurality of the diagonal pattern to each other, the correction value calculating unit, the plurality of horizontal patterns of positions in the main scanning direction are different from each other Each of them determines a positional deviation of the horizontal pattern in the main scanning direction based on the signal intensity of the detection signal detected by the sensor, and out of a plurality of the oblique line patterns, the positional deviation of the oblique line pattern in the main scanning direction is determined. The oblique line pattern used for the determination is determined based on the determination result of the positional deviation of the horizontal pattern in the main scanning direction .

  Another aspect of the present invention is an image forming apparatus including the optical writing control device.

According to still another aspect of the present invention, there is provided a method for controlling an optical writing apparatus that controls an optical source for exposing a photosensitive member to form an electrostatic latent image on the photosensitive member, and includes a plurality of different colors provided for different colors. The light sources are controlled to emit light on the basis of the information of the pixels constituting the image to be imaged and output, and the plurality of photoconductors provided for different colors are exposed to form an electrostatic image formed on the photoconductor. A detection signal of a sensor that detects the image is acquired in a conveyance path on which the image in which the latent image is developed is transferred and conveyed, and the electrostatic latent images formed on the plurality of photosensitive members are developed differently. Based on the detection signal detected by the sensor, the correction pattern for correcting the overlay position where the color developer images are superimposed is calculated a correction value for correcting the overlay position, The correction pattern is The width in the main scanning direction of a pattern parallel to the main scanning direction detection range of a tilted pattern horizontal pattern and the main scanning direction in the main scanning direction is a width corresponding to the main scanning width of the sensor An oblique line pattern whose width corresponds to the width of the detection range of the sensor in the main scanning direction, and a plurality of the horizontal patterns are included at different positions in the sub-scanning direction in the correction pattern. The horizontal patterns of the horizontal pattern are different from each other in the main scanning direction, and a plurality of the oblique line patterns are included in the correction pattern at different positions in the sub-scanning direction, and the positions of the plurality of oblique line patterns in the main scanning direction are mutually different. Unlikely, each of the plurality of horizontal patterns whose positions in the main scanning direction are different from each other is based on the signal intensity of the detection signal detected by the sensor. Judgment of misalignment in the scanning direction, and among the plurality of hatched patterns, the hatched pattern used for judging the misalignment of the hatched pattern in the main scanning direction is the determination result of the misalignment of the horizontal pattern in the main scanning direction. It determines based on .

  According to the present invention, it is possible to reduce the amount of toner consumed for the correction pattern drawing and the time required for the correction operation while maintaining the accuracy of the image drawing position in the image forming apparatus.

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 figure which shows the structure of the optical writing apparatus which concerns on embodiment of this invention. It is a block diagram which shows the structure of the optical writing control part and LEDA which concern on embodiment of this invention. It is a figure which shows the example of the pattern for a correction | amendment based on a prior art. It is a figure which shows the example of the detection timing of the pattern for position shift correction which concerns on embodiment of this invention. It is a figure which shows the example of the correction pattern of the width | variety according to the detection range of a sensor element. It is a figure which shows the change of the detection signal by the position shift of the main scanning direction of the correction pattern which concerns on embodiment of this invention. It is a figure which shows the correction error by the position shift of the main scanning direction of the pattern for a correction | amendment which concerns on embodiment of this invention. It is a figure which shows the example of the pattern for a correction | amendment which concerns on embodiment of this invention. It is a figure which shows the example of the correction pattern and detection signal which concern on embodiment of this invention. It is a figure which shows the example of the correction pattern and detection signal which concern on embodiment of this invention. It is a flowchart which shows the position shift correction operation | movement which concerns on embodiment of this invention. It is a figure which shows the information of the detection result of the correction pattern which concerns on embodiment of this invention. It is a figure which shows the judgment principle of the main scanning position shift amount based on the horizontal pattern which concerns on embodiment of this invention. It is a figure which shows the convergence of the error after correction | amendment by the error of the main scanning direction of the pattern for position shift correction.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, an image forming apparatus as an MFP (Multi Function Peripheral) will be described as an example. The image forming apparatus according to the present embodiment is an electrophotographic image forming apparatus, and performs a correction operation based on a configuration of a pattern drawn in a misalignment correction operation for correcting the exposure timing of a photoconductor and a detection result thereof. Has characteristics.

  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 the CPU 10 performs calculations according to those programs, thereby configuring a software control unit. The 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) 110, 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 ROM 12, nonvolatile memory, and a nonvolatile recording medium such as the HDD 14 or an optical disk is loaded into a volatile memory (hereinafter referred to as memory) such as the RAM 11, and these programs are loaded. The controller 20 is configured by a software control unit configured by calculation of the CPU 10 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 controls the print engine 26 based on the generated drawing information, and executes image formation on the paper conveyed from the paper supply table 25. To do. That is, the print engine 26 functions as an image forming unit. A document on which an image has been formed by the print engine 26 is discharged to a discharge tray 27.

  When the image forming apparatus 1 operates as a scanner, the operation display control unit 34 or the input / output unit is operated in accordance with a user operation on the display panel 24 or a scan execution instruction input from an external PC or the like via the network I / F 28. The control unit 32 transfers a scan execution signal to the main control unit 30. The main control unit 30 controls the engine control unit 31 based on the received scan execution signal.

  The engine control unit 31 drives the ADF 21 and conveys the document to be imaged set on the ADF 21 to the scanner unit 22. Further, the engine control unit 31 drives the scanner unit 22 and images a document conveyed from the ADF 21. If no original is set on the ADF 21 and the original is directly set on the scanner unit 22, the scanner unit 22 takes an image of the set original under the control of the engine control unit 31. That is, the scanner unit 22 operates as an imaging unit.

  In the imaging operation, an imaging element such as a CCD included in the scanner unit 22 optically scans the document, and imaging information generated based on the optical information is generated. The engine control unit 31 transfers the imaging information generated by the scanner unit 22 to the image processing unit 33. The image processing unit 33 generates image information based on the imaging information received from the engine control unit 31 according to the control of the main control unit 30. Image information generated by the image processing unit 33 is stored in a storage medium attached to the image forming apparatus 1 such as the HDD 14. That is, the scanner unit 22, the engine control unit 31, and the image processing unit 33 work together to function as a document reading unit.

  The image information generated by the image processing unit 33 is stored in the HDD 14 or the like as it is according to a user instruction or transmitted to an external device via the input / output control unit 32 and the network I / F 28. That is, the ADF 21 and the engine control unit 31 function as an image input unit.

  Further, when the image forming apparatus 1 operates as a copying machine, the image processing unit 33 generates drawing information 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. To do. 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 transport belt 105, which is an intermediate transfer belt on which an intermediate transfer image for transfer onto a sheet (an example of a recording medium) 104 that is separated and fed from the sheet feed tray 101 by the sheet feed roller 102 is formed. A plurality of image forming units (electrophotographic process units) 106Y, 106M, 106C, and 106K (hereinafter collectively referred to as image forming units 106) are arranged in order from the upstream side in the transport direction of the transport belt 105.

  Further, the sheet 104 fed from the sheet feeding tray 101 is stopped once by the registration roller 103 and is sent out to the image transfer position from the conveying belt 105 according to the image forming timing in the image forming unit 106.

  The plurality of image forming units 106Y, 106M, 106C, and 106K have the same internal configuration except that the colors of the toner images to be formed, that is, the developer images are different. The image forming unit 106K 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 106Y will be described in detail. However, since the other image forming units 106M, 106C, and 106K are the same as the image forming unit 106Y, the image forming units 106M, 106C, and 106K. For each of these components, instead of Y added to each component of the image forming unit 106Y, only the symbols distinguished by M, C, and K are displayed in the figure, and the description 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. .

  During image formation, the first image forming unit 106Y transfers a black toner image to the conveyance belt 105 that is driven to rotate. The image forming unit 106Y includes a photoconductor drum 109Y as a photoconductor, a charger 110Y disposed around the photoconductor drum 109Y, an optical writing device 111, a developing device 112Y, a photoconductor cleaner (not shown), and a static eliminator. 113Y and the like. The optical writing device 111 is configured to irradiate light to each of the photosensitive drums 109Y, 109M, 109C, and 109K (hereinafter collectively referred to as “photosensitive drum 109”).

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

  This toner image is transferred onto the conveyance belt 105 by the action of the transfer unit 115Y at a position (transfer position) where the photosensitive drum 109Y and the conveyance belt 105 come into contact or closest to each other. By this transfer, an image of yellow toner is formed on the conveyance belt 105. After the transfer of the toner image is completed, the photosensitive drum 109Y is wiped away with unnecessary toner remaining on the outer peripheral surface by the photosensitive cleaner, and then is neutralized by the static eliminator 113Y and waits for the next image formation.

  As described above, the yellow toner image transferred onto the conveying belt 105 by the image forming unit 106Y is conveyed to the next image forming unit 106M by driving the rollers of the conveying belt 105. In the image forming unit 106M, a magenta toner image is formed on the photosensitive drum 109M by the same process as the image forming process in the image forming unit 106Y, and the toner image is superimposed and transferred onto the already formed yellow image. Is done.

  The yellow and magenta toner images transferred onto the conveying belt 105 are further conveyed to the next image forming units 106C and 106K, and the cyan toner image formed on the photosensitive drum 109C and the photosensitive member are subjected to the same operation. The black toner image formed on the body drum 109K is superimposed and transferred on the already transferred image. Thus, a full-color intermediate transfer image is formed on the conveyance belt 105.

  The sheets 104 stored in the sheet feed tray 101 are sent out in order from the top, and the intermediate transfer image formed on the conveyance belt 105 is transferred at a position where the conveyance path is in contact with or closest to the conveyance belt 105. It is transferred onto the paper. As a result, an image is formed on the surface of the sheet 104. The sheet 104 on which the image is formed on the sheet surface is further conveyed, the image is fixed by the fixing device 116, and then discharged to the outside of the image forming apparatus.

  Further, in such an image forming apparatus 1, the error in the interaxial distances of the photosensitive drums 109 Y, 109 M, 109 C, and 109 K, the parallelism error in the photosensitive drums 109 Y, 109 M, 109 C, and 109 K, and the optical writing device 111 Due to the installation error of the LEDA 130 and the writing timing error of the electrostatic latent images on the photosensitive drums 109Y, 109M, 109C and 109K, the toner images of the respective colors do not overlap at positions that should originally overlap, Deviation 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, registration deviation in the sub-scanning direction, and the like are mainly known. In addition, the expansion and contraction of the conveyor belt due to the temperature change in the apparatus and deterioration with time are known.

  A pattern detection sensor 117 is provided to correct such positional deviation. The pattern detection sensor 117 is an optical sensor for reading the misalignment correction pattern and the density correction pattern transferred onto the conveyance belt 105 by the photosensitive drums 109Y, 109M, 109C, and 109K. 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 conveying direction of the conveying belt 105 on the downstream side of the photosensitive drums 109Y, 109M, 109C, and 109K. .

Further, in the image forming apparatus 1, the image forming unit 106Y, 106M, 106C, state changes or 106K, the state change of the optical specification-out write device 111, a possibility that the density of the image transferred onto the paper 104 varies There is. To correct such a density variation, and detects the density correction pattern formed according to a predetermined rule, the detection result Based on the image forming unit 106Y, 106M, 106C, 106K drive parameter and the optical specification-out write device Density correction for correcting 111 drive parameters is executed.

  The pattern detection sensor 117 is used to detect a density correction pattern in addition to the above-described position shift correction operation by detecting the position shift correction pattern. Details of the pattern detection sensor 117 and the mode of positional deviation correction and density correction will be described in detail later.

  A belt cleaner 118 is provided in order to remove the toner of the correction pattern drawn on the conveyance belt 105 in such drawing parameter correction and prevent the paper conveyed by the conveyance belt 105 from being stained. As shown in FIG. 3, the belt cleaner 118 is a cleaning blade pressed against the conveyance belt 105 on the downstream side of the driving roller 107 and on the upstream side of the photosensitive drum 109. It is a developer removing unit that scrapes off the adhered toner.

  Next, the optical writing device 111 according to the present embodiment will be described. FIG. 4 is a diagram showing an arrangement relationship between the optical writing device 111 and the photosensitive drum 109 according to the present embodiment. As shown in FIG. 4, the irradiation light irradiated to the photosensitive drums 109Y, 109M, 109C, and 109K of the respective colors is LEDA (Light-emitting diode Array) 130Y, 130M, 130C, and 130K (hereinafter, generally referred to as “light source”). LEDA130).

  The LEDA 130 is configured by arranging LEDs, which are light emitting elements, in the main scanning direction of the photosensitive drum 109. The control unit included in the optical writing device 111 controls the lighting / extinguishing states of the LEDs arranged in the main scanning direction for each main scanning line based on the drawing information input from the controller 20. The surface of the photosensitive drum 109 is selectively exposed to form an electrostatic latent image.

  Next, a control block of the optical writing device 111 according to the present embodiment will be described with reference to FIG. FIG. 5 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 connection relationship between the LEDA 130 and the pattern detection sensor 117.

  As shown in FIG. 5, the optical writing device control unit 120 according to the present embodiment includes a light emission control unit 121, a count 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 control unit 120 functions as an optical writing control device that controls the LEDA 130 that is a light source to form an electrostatic latent image on the photosensitive member.

  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 is operated under the control of the CPU 10.

  The light emission control unit 121 is a light source control unit that controls the LEDA 130 based on image information input from the engine control unit 31 of the controller 20. That is, the light emission control unit 121 also functions as a pixel information acquisition unit. The light emission control unit 121 realizes optical writing on the photosensitive drum 109 by causing the LEDA 130 to emit light at a predetermined line cycle.

  The line cycle in which the light emission control unit 121 controls the light emission of the LEDA 130 is determined by the output resolution of the image forming apparatus 1. However, as described above, the light emission control is performed when scaling is performed in the sub-scanning direction in accordance with the ratio with the paper conveyance speed. The unit 121 performs scaling in the sub-scanning direction by adjusting the line period.

  In addition to driving the LEDA 130 based on the drawing information input from the engine control unit 31, the light emission control unit 121 controls the light emission of the LEDA 130 in order to draw a correction pattern in the drawing parameter correction process described above. .

  As described with reference to FIG. 4, a plurality of LEDAs 130 are provided corresponding to the respective colors. Therefore, as shown in FIG. 5, a plurality of light emission control units 121 are also provided so as to correspond to the plurality of LEDAs 130, respectively. The correction value generated as a result of the positional deviation correction process in the drawing parameter correction process is stored as a positional deviation correction value in the correction value storage unit 126 shown in FIG. The light emission control unit 121 corrects the timing for driving the LEDA 130 based on the positional deviation correction value stored in the correction value storage unit 126.

  Specifically, the correction of the drive timing of the LEDA 130 by the light emission control unit 121 is to delay the timing for driving the LEDA 130 to emit light on a line cycle basis based on the drawing information input from the engine control unit 31, that is, to shift the line. It is realized by. On the other hand, since the drawing information is sequentially input from the engine control unit 31 according to a predetermined cycle, in order to delay the light emission timing by shifting the line, the input drawing information is held, It is necessary to delay the read timing.

  Therefore, the light emission control unit 121 has a line memory that is a storage medium for holding drawing information input for each main scanning line, and stores the drawing information input from the engine control unit 31 in the line memory. Hold by. In addition, as a correction | amendment of the drive timing of LEDA130, the fine adjustment of the light emission timing for every line period is also performed other than the adjustment per line period.

  In the positional deviation correction process, the count unit 122 starts counting at the same time as the light emission control unit 121 controls the LEDA 130 to start exposure of the photosensitive drum 109K. The count unit 122 acquires a detection signal output when the sensor control unit 123 detects a misalignment correction pattern based on the output signal of the pattern detection sensor 117. Further, the count unit 122 inputs the count value at the timing when the detection signal is acquired to the correction value calculation unit 124. That is, the count unit 122 functions as a detection timing acquisition unit that acquires pattern detection timing.

  The sensor control unit 123 is a control unit that controls the pattern detection sensor 117. As described above, the misregistration correction pattern formed on the conveyance belt 105 is subjected to pattern detection based on the output signal of the pattern detection sensor 117. It is determined that the position of the sensor 117 has been reached, and a detection signal is output. That is, the sensor control unit 123 functions as a detection signal acquisition unit that acquires a pattern detection signal from the pattern detection sensor 117.

  In addition, the sensor control unit 123 acquires the signal intensity of the output signal of the pattern detection sensor 117 and inputs it to the correction value calculation unit 124 when performing density correction using the density correction pattern. Further, the sensor control unit 123 adjusts the detection timing of the density correction pattern according to the detection result of the position deviation correction pattern.

  The correction value calculation unit 124 is based on the count value acquired from the count unit 122 and the signal intensity of the detection result of the density correction pattern acquired from the sensor control unit 123. The correction value is calculated based on the reference value for density correction. That is, the correction value calculation unit 124 functions as a reference value acquisition unit and a correction value calculation unit. The reference value storage unit 125 stores a reference value for use in such calculation.

  Next, a misregistration correction operation using the misregistration correction pattern will be described. First, as a premise of the misalignment correction operation according to the present embodiment, the misalignment correction operation according to the related art will be described. FIG. 6 is a diagram showing marks (hereinafter referred to as misalignment correction marks) drawn on the transport belt 105 by the LEDA 130 controlled by the light emission control unit 121 in the misalignment correction operation according to the prior art.

  As shown in FIG. 6, the misregistration correction mark 400 according to the prior art has a plurality of misregistration correction pattern rows 401 in which various patterns are arranged in the sub-scanning direction (in the present embodiment). 2) are arranged side by side. In FIG. 6, the solid line represents a pattern drawn by the photosensitive drum 109K, 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 a pattern drawn by the photosensitive drum 109M.

  As shown in FIG. 6, the pattern detection sensor 117 has a plurality (two in the present embodiment) of sensor elements 170 in the main scanning direction, and each misalignment correction pattern row 401 includes each sensor element. It is drawn at a position corresponding to 170. As a result, the optical writing device control unit 120 can detect patterns at a plurality of positions in the main scanning direction, and can correct skew of a drawn image. Further, by averaging the detection results based on the plurality of sensor elements 170, the correction accuracy can be improved.

  As shown in FIG. 6, the misalignment correction pattern row 401 includes an overall position correction pattern 411 and a drum interval correction pattern 412. As shown in FIG. 6, the drum interval correction pattern 412 is repeatedly drawn.

  The overall position correction pattern 411 according to the prior art is a line drawn by the photosensitive drum 109Y and parallel to the main scanning direction, as shown in FIG. The overall position correction pattern 411 is a pattern drawn to obtain a count value for correcting the shift of the entire image in the sub-scanning direction, that is, the transfer position of the image with respect to the paper. The overall position correction pattern 411 is also used by the sensor control unit 123 to correct the detection timing when the drum interval correction pattern 412 and a density correction pattern described later are detected.

  In the overall position correction using the overall 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 overall position correction pattern 411 by the pattern detection sensor 117.

  The drum interval correction pattern 412 is a pattern drawn to obtain a count value for correcting a shift in drawing timing on the photosensitive drum 109 of each color, that is, an overlapping position where images of each color are overlaid. As shown in FIG. 6, the drum interval correction pattern 412 includes a sub-scanning direction correction pattern 413 and a main scanning direction correction pattern 414. As shown in FIG. 6, the drum interval correction pattern 412 is configured by repeating a sub-scanning direction correction pattern 413 and a main scanning direction correction pattern 414 that are a set of CMYK color patterns. The

  The optical writing device control unit 120 corrects the positional deviation in the sub-scanning direction of each of the photosensitive drums 109K, 109M, 109C, and 109Y based on the reading signal of the sub-scanning direction correction pattern 413 by the pattern detection sensor 117, and performs main correction. 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.

  The sub-scanning direction correction pattern 413 is a horizontal pattern parallel to the main scanning direction. Also, as shown in FIG. 6, the drum interval correction pattern 412 is repeatedly drawn in the sub-scanning direction, so that a plurality of sub-scanning direction correction patterns 413 are located at different positions in the sub-scanning direction in the misalignment correction marks. Will be included.

  The main scanning direction correction pattern 414 is a diagonal pattern inclined with respect to the main scanning direction. Also, as shown in FIG. 6, the drum interval correction pattern 412 is repeatedly drawn in the sub-scanning direction, whereby a plurality of main scanning direction correction patterns 414 are located at different positions in the sub-scanning direction in the misalignment correction mark. Will be included.

Here, each color timing reference value stored in the reference value storage unit 125 will be described with reference to FIG. FIG. 7 is a diagram illustrating detection timings of the overall position correction pattern 411 and the drum interval correction pattern 412. As shown in FIG. 7, the detection period t _Y0 of the overall position correction pattern 411 is the detection period from the detection start timing t ₀ is before the timing has been each of the line drawn by the photosensitive drum 109Y is read .

Further, the detection periods t _1Y , t _1K , t _1M , t _{1C of the} sub-scanning direction correction pattern 413 included in the drum interval correction pattern 412 and the detection periods t _2Y , t _2K , t of the main scanning direction correction pattern 414 are included. _{2M, t 2C} is a detection period from the detection start timing _t 1, _{t 2} is a front timing a set of patterns is read.

A reference value storage unit 125, the detection period _t 1Y detection period _{t Y0} and the sub-scanning direction correction pattern 413 and the main scanning direction correction pattern 414 of the overall position correction pattern 411 shown in FIG. _{7, t} 1K, t Reference values for _1M , t _1C , t _2Y , t _2K , t _2M , t _2C . In other words, the reference value storage unit 125 includes the detection period _tY0 of the overall position correction pattern 411 when the detailed configuration of each part of the image forming apparatus is as designed, the sub-scanning direction correction pattern 413, and the main scanning direction. The theoretical values of the detection periods t _Y , t _K , t _M , and t _C of the correction pattern 414 are stored as reference values.

That is, the correction value calculation unit 124 calculates the difference between each reference value stored in the reference value storage unit 125 and the detection periods t _Y0 , t _Y , t _K , t _M , and t _C shown in FIG. Thus, a deviation from the design value of the image forming apparatus on which the image forming apparatus is mounted is obtained, and a correction value for correcting the light emission timing of the LEDA 130 is calculated based on the deviation.

Further, the reference value for the detection period _tY0 of the overall position correction pattern 411 is also used to correct the detection start timings t ₁ and t ₂ shown in FIG. That is, the correction value calculation unit 124 corrects the detection start timings t ₁ and t ₂ shown in FIG. 7 based on the difference between the detection period t _Y0 of the overall position correction pattern 411 and the reference value corresponding thereto. The correction value is calculated. Thereby, the accuracy of the detection period of the drum interval correction pattern 412 can be improved.

  Since the misregistration correction mark 400 is drawn every time in a misregistration correction operation that is repeatedly executed at a predetermined timing, it is required to reduce the toner consumption by reducing the drawing range as much as possible. Therefore, as shown in FIG. 8, it is ideal to set the width of each pattern in the main scanning direction to a width corresponding to the detection range of the sensor element 170. In other words, each pattern constituting the misregistration correction mark 400 is ideally a narrow pattern drawn with a width corresponding to the reading range of the sensor element 170. In FIG. 8, “′” is added to the reference numerals of the patterns corresponding to the respective patterns shown in FIG.

  However, the drawn pattern may actually shift in the main scanning direction. Therefore, when a narrow pattern with a small margin in the main scanning direction is drawn with respect to the detection range of the sensor element 170 as shown in FIG. 8, when the pattern is shifted in the main scanning direction, In some cases, the S / N ratio of the sensor output decreases, resulting in a detection error.

  Here, an adverse effect when the drawing positions in the main scanning direction of the sub-scanning direction correction pattern 413 ′ and the main scanning direction correction pattern 414 ′ included in the drum interval correction pattern 412 ′ are shifted will be described. FIGS. 9A and 9B are diagrams showing the relationship between the position of the sub-scanning direction correction pattern 413 ′ with respect to the detection range 170 ′, which is the pattern detection position by the sensor element 170, and the detection signal. In the figure, the vertical direction is the main scanning direction, and the horizontal direction is the sub-scanning direction.

  FIG. 9A is a diagram illustrating a case where the sub-scanning direction correction pattern 413 ′ is drawn at a normal position with respect to the detection range 170 ′ of the sensor element 170. As shown in FIG. 9A, when the sub-scanning direction correction pattern 413 ′ is drawn at a normal position with respect to the detection range 170 ′, the range of the range that falls within the detection range 170 ′ among the respective patterns. A signal having a peak at the timing when the center in the transport direction reaches the center of the detection range 170 ′ is detected.

  FIG. 9B is a diagram illustrating a case where the sub-scanning direction correction pattern 413 ′ is drawn with a shift in the main scanning direction with respect to the detection range 170 ′ of the sensor element 170. As shown in FIG. 9B, when the sub-scanning direction correction pattern 413 ′, which is a narrow pattern with respect to the detection range 170 ′, is drawn with a shift in the main scanning direction, detection is performed from among the drawn patterns. Since the range that falls within the range 170 ′ is reduced, the peak of the detection signal is weakened accordingly.

  As shown in FIGS. 9A and 9B, only the peak intensity of the detection signal is affected when the sub-scanning direction correction pattern 413 ′ is drawn shifted in the main scanning direction. Since only the detection timing is required for detection of the sub-scanning direction correction pattern 413 ′, even if the peak intensity becomes weak, it is not a big problem as long as the detection timing can be determined.

  FIGS. 10A to 10C are diagrams showing the relationship between the position of the main scanning direction correction pattern 414 ′ with respect to the detection range 170 ′ of the sensor element 170 and the detection signal. As in FIGS. 9A and 9B, in the drawing, the vertical direction is the main scanning direction, and the horizontal direction is the sub-scanning direction.

  FIG. 10A is a diagram illustrating a case where the main scanning direction correction pattern 414 ′ is drawn at a normal position with respect to the detection range 170 ′ of the sensor element 170. As shown in FIG. 10A, when the main scanning direction correction pattern 414 ′ is drawn at a normal position with respect to the detection range 170 ′, the range of the range that falls within the detection range 170 ′ of each pattern. A signal having a peak at the timing when the center in the transport direction reaches the center of the detection range 170 ′ is detected.

  FIG. 10B is a diagram showing a case where the main scanning direction correction pattern 414 ′ is drawn with a shift in the main scanning direction with respect to the detection range 170 ′ of the sensor element 170. As shown in FIG. 10B, when the main scanning direction correction pattern 414 ′, which is a narrow-width pattern, is drawn with a deviation from the detection range 170 ′, the detection range 170 ′ is drawn out of the drawn patterns. Since the range that falls in is reduced, the peak of the detection signal is weakened accordingly.

  Further, in the case of FIG. 10B, the detection timing of the signal is shifted in accordance with the inclination of the main scanning direction correction pattern 414 ′ by the amount that the main scanning direction correction pattern 414 ′ that is a narrow width pattern is shifted in the main scanning direction. It will be. The signal peak is the timing at which the center in the sub-scanning direction of the portion entering the detection range 170 ′ of the main scanning direction correction pattern 414 ′ reaches the center of the detection range 170 ′ in the sub-scanning direction.

  As a result, the timing is shifted by “g1” shown in the drawing from the timing of FIG. The gist of the correction by the main scanning direction correction pattern 414 ′ is to adjust the position of the pattern to be drawn in the main scanning direction according to the timing shift. In FIGS. 10A to 10C, the positions in the main scanning direction of the patterns included in the main scanning direction correction pattern 414 ′ are all shown in the same position. Since the installation of the photosensitive drum 109 and the installation of the LEDA 130 are different for each color, there is a different shift for each color.

  On the other hand, in FIG. 10C, the main scanning direction correction pattern 414 is drawn with a margin in the main scanning direction with respect to the detection range 170 ′ of the sensor element 170 as described in FIG. It is a case, Comprising: It is a figure which shows the case where the shift | offset | difference of the main scanning direction similar to FIG.10 (b) generate | occur | produced. In FIG. 10C, the main scanning direction correction pattern 414 not shown in FIG. 10B is indicated by a dotted line.

  In the case of FIG. 10C, the peak of the signal is such that the center in the sub-scanning direction of the detection range 170 ′ in the main scanning direction correction pattern 414 ′ is the center in the sub-scanning direction of the detection range 170 ′. The arrival timing is the same.

  However, in the case of FIG. 10C, since the width of each pattern in the main scanning direction is drawn with a margin with respect to the detection range 170 ′, the main scanning direction correction pattern 414 includes the detection range 170 ′. The center position in the sub-scanning direction of the entering range is different. As a result, the peak timing is shifted by “g2” shown in the figure. That is, originally, the deviation in the main scanning direction has to be corrected based on the sum of “g1” and “g2”, but in the case of FIG. 10B, the correction is based on “g1”. It will be done.

  In other words, if the diagonal pattern drawn for correcting the positional deviation in the main scanning direction with respect to the width in the main scanning direction of the detection range 170 ′ is a narrow width pattern and the width margin in the main scanning direction is reduced as much as possible, the detection range 170. The main scanning direction of the oblique line pattern is interrupted with respect to ′, and as a result, the detection timing is shifted. Solving such an adverse effect is one of the gist according to the present embodiment.

  FIG. 11 is a diagram showing details of the drum interval correction pattern 412 ′ included in the misregistration correction mark 400 ′ according to the present embodiment described in FIG. As described above, the drum interval correction pattern 412 ′ is repeatedly drawn in the sub-scanning direction. Then, in the misregistration correction mark 400 ′ according to the present embodiment, as shown in FIG. 11, each drum interval correction pattern 412 ′ that is repeatedly drawn is drawn while being shifted in the main scanning direction. That is, the positions in the main scanning direction of the plurality of horizontal patterns and oblique line patterns are different from each other.

  In FIG. 11, three drawn drum interval correction patterns 412 ′ are denoted as “A”, “B”, and “C”, respectively. The drum interval correction pattern 412 ′ of A is drawn so that the center in the main scanning direction coincides with the center of the detection range 170 ′. The B drum interval correction pattern 412 ′ is drawn with the center in the main scanning direction shifted from the center of the detection range 170 ′ by the width g 3 on the left side in the drawing.

  The C drum interval correction pattern 412 ′ is drawn with the center in the main scanning direction shifted from the center of the detection range 170 ′ on the right side in the drawing by a width g 3. In other words, the B and C patterns are offset patterns drawn by offsetting the position in the main scanning direction with respect to the detection range 170 ′, and the offset amount is g3. Note that the arrangement shown in FIG. 11 is an ideal state, and when a positional shift occurs due to the above-described various factors, the respective patterns are also shifted in accordance with the shift amount.

  FIG. 12 is a diagram illustrating an example of a detection signal when the pattern detection sensor 117 detects the drum interval correction pattern 412 ′ illustrated in FIG. 11. As shown in FIG. 12, the center in the main scanning direction extends from the center of the detection range 170 ′ to the main scanning direction as compared to the pattern A in which the center in the main scanning direction coincides with the center of the detection range 170 ′. In the case of the shifted B and C patterns, the peak of the detection signal becomes small. In the case of the B and C patterns, as described with reference to FIGS. 10A to 10C, errors in detection timing also occur.

  FIG. 13 is a diagram illustrating an example in the case where a position shift in the main scanning direction due to the various factors described above occurs. As can be seen from the sub-scanning direction correction pattern 413 'in FIG. The yellow pattern has no misalignment in the main scanning direction. The black and cyan patterns have a misalignment shifted to the left in the figure in the main scanning direction, but the black misalignment is larger than the cyan misalignment. The magenta pattern has a positional shift that is shifted to the right in the drawing in the main scanning direction.

  For the yellow pattern in which no positional deviation has occurred, the pattern A is accurately read by the sensor element 170. Therefore, when correcting the positional deviation of the photosensitive drum 109Y corresponding to yellow, it is possible to perform an accurate positional deviation correction based on at least the timing of the detection signal of the pattern A.

  Further, as described in FIGS. 9A and 9B, even if a positional deviation occurs in the main scanning direction, the influence on the detection result of the sub-scanning direction correction pattern 413 ′ is the peak level of the detection signal, that is, Only signal strength. Therefore, even if the peak level of the detection signal is lowered, the timing of the detection signal of the B and C pattern may be referred to as long as the peak level can be accurately detected. Thereby, it is possible to suppress an error due to a period variation of the photosensitive drum 109 in the sub-scanning direction.

  In the black and cyan patterns in which the position shift occurs on the left side in the figure, the peak of the detection signal of the pattern A is slightly lower, and the peak of the detection signal of the pattern B that was originally shifted to the left side is further Lower. On the other hand, since the pattern of C was originally shifted to the right side, the position in the main scanning direction of the pattern approaches the center of the detection range 170 ′ in the main scanning direction due to the occurrence of the position shift to the left side. The peak of approaches the maximum value.

  Therefore, when correcting the misregistration for the photosensitive drums 109B and 109C corresponding to black and cyan, respectively, it is possible to correct the misregistration accurately based on at least the detection signal timing of the C pattern.

  Here, the correction value generated based on the detection result of the sub-scanning direction correction pattern 413 ′ is a value for correcting the positional deviation in the sub-scanning direction. For this reason, even when the detection result of the C pattern in which the pattern is previously shifted in the main scanning direction is used, the correction value in the sub scanning direction is not affected.

  On the other hand, the main scanning direction correction pattern 414 ′ is for detecting a shift in the main scanning direction of the pattern by a detection timing shift corresponding to the inclination of the oblique line. Therefore, when using a pattern that is shifted in the main scanning direction in advance, it is necessary to subtract the amount of shift to obtain a correction value. This deviation amount is the width g3 described in FIG.

  As for the magenta pattern in which the positional deviation is generated on the right side in the figure, the peak of the detection signal of the A pattern is slightly lower and the B pattern that was originally shifted to the left side is the same as the black and cyan patterns. When the rightward misalignment occurs, the center of the pattern in the main scanning direction approaches the center of the detection range 170 'in the main scanning direction, and the peak of the detection signal approaches the maximum value. On the other hand, the peak of the detection signal of the C pattern that was originally shifted to the right side is further lowered.

  Therefore, when correcting the misregistration for the photosensitive drum 109M corresponding to magenta, it is possible to correct the misregistration accurately based on at least the timing of the detection signal of the B pattern. In this case, when calculating the correction value in the main scanning direction using the main scanning direction correction pattern 414 ′, the correction value needs to be obtained by subtracting the width g3, as in the above-described black and cyan.

Thus, in the optical specification-out write device 111 according to this embodiment, when the drawing of the positional deviation correction mark 400 ', as described in FIG. 8, the width in the main scanning direction of the pattern, the sensor element 170 By setting the margin as small as possible in accordance with the width of the detection range 170 ′, the amount of toner consumed for correcting misalignment is reduced.

  When the margin in the main scanning direction of the pattern is reduced, when a position shift in the main scanning direction occurs, the position in the main scanning direction where the pattern is formed is shifted from the detection range 170 ′ of the sensor element 170. May not be detected accurately. In order to solve such a problem, the drum interval correction pattern 412 ′ repeatedly drawn in the misregistration correction mark 400 ′ according to the present embodiment has a main scanning direction for each repetition as shown in FIG. 11. It is drawn by being shifted.

  In the present embodiment, the center of the pattern in the main scanning direction is shifted to one direction opposite to the main scanning direction in addition to the A pattern in which the center of the detection range 170 ′ coincides with the center of the main scanning direction. B and C patterns are drawn. Accordingly, as described with reference to FIG. 13, when a positional deviation in the main scanning direction occurs in the drawn pattern, the center in the main scanning direction of the pattern drawn in a state shifted in the main scanning direction in advance is set. Since it approaches the center of the detection range 170 ′ in the main scanning direction, the pattern can be detected accurately.

  With such a configuration of the misregistration correction mark 400 ′, in the misregistration correction processing according to the present embodiment, as described in FIG. 8, the main scanning direction width of each pattern is the main of the detection range 170 ′. Even if a position shift in the main scanning direction occurs even though the drawing is performed with a small margin with respect to the width in the scanning direction, a pattern shifted in the main scanning direction is detected in advance and the detection is not performed. There is no such thing as failure. Accordingly, it is possible to avoid a retry of the misalignment correction operation, and it is possible to reduce the amount of toner used for pattern drawing and shorten the time required for the correction operation.

  Next, the misregistration correction operation according to the present embodiment will be described with reference to the flowchart of FIG. As shown in FIG. 14, in the misregistration correction operation, the optical writing device control unit 120 starts pattern drawing (S1401), and starts pattern detection based on the detection signal of the pattern detection sensor 117 (S1402). Accordingly, the correction value calculation unit 124 sequentially acquires information as illustrated in FIG. 15 according to the pattern detection.

t _1Y , t _1K , t _1M , and t _1C are detection results of the sub-scanning direction correction pattern 413 ′ as described with reference to FIG. 7, and are detection periods from the detection start timing t ₁ . t _2Y , t _2K , t _2M , and t _2C are detection results of the main scanning direction correction pattern 414 ′ as described with reference to FIG. 7, and are detection periods from the detection start timing t ₂ .

On the other hand, P _t1Y , P _t1K , P _t1M , P _t1C and P _t2Y , P _t2K , P _t2M , P _t2C are t _1Y , t _1K , t _1M , t _1C and t _2Y , t _2K , t, respectively. It is a value indicating the peak level of the detection signal corresponding to _2M and _t2C . The peak level according to the present embodiment is the amount of signal fall in the diagram shown in FIG. The detection signal of the pattern detection sensor 117 is originally an analog signal, but is processed as digital information by determining the signal intensity of the peak value of the analog signal based on a plurality of threshold values.

Note that the additions “−A”, “−B”, and “−C” correspond to the A pattern, the B pattern, and the C pattern described in FIG. 11, respectively. That is, t _1Y -A indicates the yellow detection period of the A-pattern sub-scanning direction correction pattern 413 ′. Further, P _t1Y -A indicates the peak level of the yellow detection signal of the pattern A for sub-scanning direction correction 413 ′.

When the correction value calculation unit 124 sequentially obtains the detection results as shown in FIG. 15 in accordance with the detection of the pattern, based on the detection results, first, a sub-scanning direction correction pattern for correcting the positional deviation in the sub-scanning direction. The detection result of 413 ′ (hereinafter referred to as “horizontal pattern”) is acquired (S1403). That is, t _1Y -A, t _1K -A,..., T _1Y -B, t _1K -B,..., T _1Y -C, t _1K -C, and the horizontal pattern detection period, P _t1Y − , P _t1K -A,..., P _t1Y -B, P _t1K -B,..., P _t1Y -C, and P _t1K -C are acquired.

Then, the correction value calculation unit 124 calculates a correction value for correcting misalignment in the sub-scanning direction based on the acquired detection results (S1404). In S1404, the correction value calculation unit 124 performs horizontal patterns such as _t1Y- A, _t1K- A, ..., _t1Y- B, _t1K- B, ..., _t1Y- C, _t1K- C. The correction value is calculated based on the difference value between the detection period and the reference value for each detection period stored in the reference value storage unit 125.

  Here, as described in FIG. 11, the drum interval correction pattern 412 ′ according to the present embodiment is drawn by shifting each pattern that is repeatedly drawn in the main scanning direction. Therefore, as described with reference to FIG. 13, the peak level of the detection signal when the pattern is detected by the pattern detection sensor 117 is significantly reduced depending on the original amount of deviation and the amount of positional deviation that has occurred. Is impossible. In such a case, each detection result shown in FIG. 15 becomes a Null value. In S1404, the correction value calculation unit 124 calculates the correction value based only on the value that has been successfully detected, and ignores the null value.

  Further, the correction value calculation unit 124 determines the amount of deviation in the main scanning direction based on the acquired peak levels (S1405). FIGS. 16A to 16C are diagrams illustrating the principle of the shift amount determination process in S1405. 16A to 16C, a horizontal pattern of a predetermined color is extracted and illustrated one by one from each of the patterns A, B, and C, and the peak level of the detection signal is shown.

  FIG. 16A is a diagram illustrating a case where there is no displacement in the main scanning direction. In this case, as described with reference to FIG. 11, the peak level of the detection signal of the A pattern whose center in the main scanning direction coincides with the detection range 170 ′ is the highest, and the peak levels of the B and C patterns are substantially the same. It is.

  FIG. 16B is a diagram illustrating a case where a positional deviation has occurred such that the center of the C pattern in the main scanning direction approaches the center of the detection range 170 ′ in the main scanning direction. In this case, the peak level of the detection signal of the C pattern is the highest, the peak level of the detection signal of the A pattern is next high, and the peak level of the detection signal of the B pattern is the lowest.

  FIG. 16C is a diagram showing a case where a positional deviation has occurred so that the center of the B pattern in the main scanning direction approaches the center of the detection range 170 ′ in the main scanning direction. In this case, the peak level of the detection signal of the B pattern is the highest, the peak level of the detection signal of the A pattern is next high, and the peak level of the detection signal of the C pattern is the lowest.

  As described above, the correction value calculation unit 124 compares the peak levels of the A, B, and C patterns with respect to the horizontal pattern of the same color, and thereby the image drawn by the photosensitive drum 109 of that color. However, it is possible to determine which direction of the main scanning direction is shifted.

  As shown in FIG. 16A, the pattern A has the highest peak level when there is no position shift in the main scanning direction, and the peak level decreases according to the position shift. Accordingly, it is possible to determine the main scanning positional deviation direction based on the magnitude relationship between the peak levels of the A, B, and C patterns, and to determine the positional deviation amount based on the peak level of the A pattern.

  As described with reference to FIG. 6, if the horizontal pattern has a sufficient margin in the main scanning direction with respect to the width of the detection range 170 ′ in the main scanning direction, it is assumed that a positional deviation has occurred in the main scanning direction. However, it is absorbed by the margin and the peak level of the detection signal of the horizontal pattern does not change. Accordingly, as shown in FIGS. 16A to 16C, the determination of the displacement direction and the amount of displacement in the main scanning direction based on the peak level of the detection signal of the horizontal pattern is performed as described in FIG. This is possible because the width in the main scanning direction is formed with a width corresponding to the width in the main scanning direction of the detection range 170 ′, that is, a width with a small margin.

When the determination of the main scanning deviation amount based on the horizontal pattern is completed, the correction value calculation unit 124 then performs a main scanning direction correction pattern 414 ′ (hereinafter referred to as a “hatched pattern”) for correcting the positional deviation in the main scanning direction. ) Is acquired (S1406). That is, t _2Y −A, t _2K −A,..., T _2Y −B, t _2K −B,..., T _2Y −C, t _2K −C, the horizontal pattern detection period, and P _t2Y − , _Pt2K- A,..., _Pt2Y- B, _Pt2K- B,..., _Pt2Y- C, and _Pt2K- C are obtained.

The correction value calculation unit 124 that has acquired the detection result of the oblique line pattern includes P _t2Y -A, P _t2K -A, ..., P _t2Y -B, P _t2K -B, ..., P _t2Y -C, P _t2K. The peak level of the oblique line pattern such as −C is referred to for each color of CMYK, and the pattern having the highest peak level among the patterns of A, B, and C is used for calculation of the misregistration correction value in the main scanning direction. Is selected as a pattern (S1407).

  When the pattern selected in this way is a B or C pattern, that is, an offset pattern (S1408 / YES), the correction value calculation unit 124 corrects the correction value in the main scanning direction based on the detection period of the selected pattern. And the calculation result is corrected by subtracting g3 which is the offset amount described in FIG. 11 (S1409). On the other hand, when the selected pattern is the pattern A (S1408 / NO), the correction value calculation unit 124 calculates the correction value in the main scanning direction based on the detection period of the selected pattern (S1410).

  When the correction value is calculated by the processing of S1409 and S1410, the correction value calculation unit 124 checks whether or not the shift direction in the main scanning direction indicated by the calculated correction value matches the shift direction determined in S1405 (S1411). . As a result, if the deviation directions do not match (S1411 / NO), it is determined that some error has occurred and error processing is performed (S1412). By such processing, the reliability of the calculated correction value can be improved.

  On the other hand, if the shift directions match (S1411 / YES), the correction value calculation unit 124 repeats the process from S1407 for each CMYK color (S1413 / NO), and completes the process from S1407 for all the CMYK colors (S1413 / NO). S1413 / YES), the process ends. With such processing, the misregistration correction operation according to the present embodiment is completed.

  As described above, in the optical writing device 111 according to the present embodiment, while maintaining the accuracy of the image drawing position in the image forming device, the amount of time required for the toner consumption reduction and the correction operation related to the correction pattern drawing can be reduced. Shortening can be realized.

  In the above-described embodiment, an example is described in which it is determined in S1407 in FIG. 14 whether the correction value is calculated based on any of the A, B, and C patterns based on the peak level of the detection signal of the oblique line pattern. did. However, this is an example. As another aspect, for example, the determination result in S1405 may be used.

  Based on the determination in S1405, the correction value calculation unit 124 determines how much the pattern of each color is shifted in which direction of the main scanning direction. Therefore, in S1407, it may be determined which pattern A, B, or C is used by using the determination result in S1405.

  For example, if it is determined in S1405 that there is no or slight displacement in the main scanning direction as in the state of FIG. 16A, the correction value calculation unit 124 determines to use the pattern A in S1407. To do. On the other hand, if the center of the C pattern in the main scanning direction is close to the detection range 170 ′ as in the state of FIG. 16B, the correction value calculation unit 124 uses the C pattern in S1407. Decide that. If the center of the B pattern in the main scanning direction is close to the detection range 170 ′ as in the state of FIG. 16C, the correction value calculation unit 124 uses the B pattern in S1407. Decide that.

  In the above-described embodiment, as described with reference to FIG. 14, the case where the misregistration correction value in the main scanning direction is calculated using one of the patterns A, B, and C selected in S1407 has been described as an example. In addition, all patterns for which peaks have been detected may be referred to.

  When referring to all the patterns in which the peak can be detected, the detection timing at which an error occurs due to the discontinuity of the pattern with respect to the detection range 170 ′ as described in FIGS. 10A to 10C is also referred to. . Therefore, it is necessary to correct the error.

  FIG. 17 is a graph in which the horizontal axis indicates the positional deviation in the main scanning direction and the vertical axis indicates the correction error when the correction value calculation process based on the oblique line pattern detection result is performed. As described above, if the error of the correction value caused by the positional deviation in the main scanning direction is known in advance, the calculated correction value is corrected based on the positional deviation amount calculated in S1405, so that FIG. The problem of the error of the correction value described in (a) to (c) can be solved. Then, by using the average value of the correction values calculated based on the plurality of patterns A, B, and C, it is possible to suppress errors due to periodic fluctuations of the photosensitive drum 109 in the sub-scanning direction.

  Further, in S1409, the case of calculating the misregistration correction value in the main scanning direction based only on the detection result of the oblique line pattern has been described as an example. However, in S1405, the correction value calculation unit 124 calculates the horizontal pattern detection result. The main scanning deviation amount is determined based on the peak level. You may make it consider this determination result in S1409.

  In the above embodiment, as described in FIG. 8, the drum interval correction pattern 412 including the sub-scanning direction correction pattern 413 ′ and the main scanning direction correction pattern 414 ′ is set as one set, and the drum interval correction pattern is used. The case where the pattern 412 is repeatedly drawn in the sub-scanning direction has been described as an example.

  However, this is merely an example. For example, after the sub-scanning direction correction pattern 413 ′ is repeatedly drawn while being shifted in the main scanning direction, the main scanning direction correction pattern 414 ′ is repeatedly drawn while being shifted in the main scanning direction. good. Such a difference is in the order of the detection timing described in FIG. 7, and there is no significant difference from the above embodiment.

  In the above embodiment, as shown in FIG. 8, the positional deviation correction mark 400 includes a horizontal pattern for correcting positional deviation in the sub-scanning direction and a diagonal pattern for correcting positional deviation in the main scanning direction. The case has been described as an example. However, as described with reference to FIGS. 16A to 16C, the position in the main scanning direction is reduced by reducing the margin of the width of the horizontal pattern in the main scanning direction with respect to the width of the detection range 170 ′ in the main scanning direction as much as possible. The shift appears due to the peak level of the detection signal of the horizontal pattern. Therefore, it is possible to perform misalignment correction in the main scanning direction using only the horizontal pattern without using the oblique line pattern.

1 Image forming apparatus 10 CPU
11 RAM
12 ROM
13 Engine 14 HDD
15 I / F
16 LCD
17 Operation unit 18 Bus 20 Controller 21 ADF
22 Scanner unit 23 Paper discharge tray 24 Display panel 25 Paper feed table 26 Print engine 27 Paper discharge 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 Registration roller 104 Paper 105 Conveying belts 106K, 106C, 106M, 106Y Image forming unit 107 Drive Roller 108 Driven roller 109K, 109C, 109M, 109Y Photoconductor drum 110K Charger 111 Optical writing device 112K, 112C, 112M, 112Y Developer 113K, 113C, 113M, 113Y Charger 115K, 115C, 115M, 115Y Transfer device 116 Fixing Device 117 Pattern detection sensor 120 Optical writing device control unit 121 Light emission control unit 122 Count unit 123 Sensor control unit 124 Correction value calculation unit 125 Reference value storage unit 126 Correction value storage units 130, 130K, 130C, 1 0M, 130Y LEDA
170 Sensor element

JP 2009-069767 A

Claims (5)

An optical writing control device for controlling a light source for exposing a photoconductor to form an electrostatic latent image on the photoconductor,
A light emission control unit that controls light emission of a plurality of light sources provided for different colors based on information of pixels constituting an image to be imaged and output, and exposes the plurality of photoconductors provided for different colors. When,
A detection signal acquisition unit that acquires a detection signal of a sensor that detects the image in a conveyance path in which an image obtained by developing the electrostatic latent image formed on the photosensitive member is transferred and conveyed;
Detection by which the sensor detects a correction pattern for correcting a superposition position where developer images of different colors developed from electrostatic latent images respectively formed on the plurality of photosensitive members are superposed. based on the signal, wherein the correction value calculation unit for calculating a correction value for correcting the superimposed position,
The correction pattern is a pattern parallel to the main scanning direction, and a horizontal pattern whose width in the main scanning direction is a width corresponding to the width of the detection range of the sensor in the main scanning direction and a pattern inclined in the main scanning direction. A diagonal pattern in which the width in the main scanning direction is a width corresponding to the width in the main scanning direction of the detection range of the sensor ,
A plurality of the horizontal patterns are included at different positions in the sub-scanning direction in the correction pattern, and the positions of the plurality of horizontal patterns in the main scanning direction are different from each other,
A plurality of the oblique line patterns are included at different positions in the sub-scanning direction in the correction pattern, and the positions of the plurality of oblique line patterns in the main scanning direction are different from each other,
The correction value calculation unit determines a positional deviation of the horizontal pattern in the main scanning direction based on a signal intensity of a detection signal in which each of the plurality of horizontal patterns having different positions in the main scanning direction is detected by the sensor; Of the plurality of oblique line patterns, an oblique line pattern used for determining positional deviation of the oblique line pattern in the main scanning direction is determined based on a determination result of positional deviation of the horizontal pattern in the main scanning direction. Optical writing control device. The correction value calculation unit
Based on the detection timing of the plurality of oblique line patterns, the positional deviation in the main scanning direction of the oblique line pattern is determined, the correction value is calculated
Based on the information indicating the error of the correction value according to the positional deviation between the position detected by the sensor and the main scanning direction of the diagonal pattern, the diagonal pattern shifted from the detection position by the sensor among the plurality of diagonal patterns. modifying said correction value calculated based on the optical specification-out write control apparatus according to claim 1, wherein. The correction value calculation unit
Based on the signal strength of the detection signal detected by the sensor, each of the plurality of horizontal patterns whose positions in the main scanning direction are different from each other, determines the positional deviation of the horizontal pattern in the main scanning direction,
The correction value is confirmed by comparing the calculated correction value and a positional deviation in the main scanning direction of the horizontal pattern determined based on a signal intensity of a detection signal of the horizontal pattern. light manual-out write control apparatus to claim 1 or 2, wherein. An image forming apparatus comprising the optical writing control device according to any one of claims 1 to 3. A method of controlling an optical writing device that controls a light source that exposes a photoconductor to form an electrostatic latent image on the photoconductor,
A plurality of light sources provided for different colors are controlled to emit light based on information of pixels constituting an image to be imaged and output, and the plurality of photoconductors provided for different colors are exposed,
Obtaining a detection signal of a sensor for detecting the image in a transport path in which an image obtained by developing the electrostatic latent image formed on the photoreceptor is transferred and transported;
Detection by which the sensor detects a correction pattern for correcting a superposition position where developer images of different colors developed from electrostatic latent images respectively formed on the plurality of photosensitive members are superposed. Based on the signal, a correction value for correcting the overlapping position is calculated,
The correction pattern is a pattern parallel to the main scanning direction, and a horizontal pattern whose width in the main scanning direction is a width corresponding to the width of the detection range of the sensor in the main scanning direction and a pattern inclined in the main scanning direction. A diagonal pattern in which the width in the main scanning direction is a width corresponding to the width in the main scanning direction of the detection range of the sensor ,
A plurality of the horizontal patterns are included at different positions in the sub-scanning direction in the correction pattern, and the positions of the plurality of horizontal patterns in the main scanning direction are different from each other,
A plurality of the oblique line patterns are included at different positions in the sub-scanning direction in the correction pattern, and the positions of the plurality of oblique line patterns in the main scanning direction are different from each other,
Based on the signal strength of the detection signal detected by the sensor, each of the plurality of horizontal patterns whose positions in the main scanning direction are different from each other, determines the positional deviation of the horizontal pattern in the main scanning direction,
Of the plurality of oblique line patterns, an oblique line pattern used for determining positional deviation of the oblique line pattern in the main scanning direction is determined based on a determination result of positional deviation of the horizontal pattern in the main scanning direction. Control method for optical writing device.