JP2013195654A - Optical writing control device, image forming apparatus, and displacement correction method of optical writing control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve detection accuracy of a pattern generated during adjustment processing for adjusting a position of an image in an image forming apparatus.SOLUTION: When a difference between intensity of a detection signal of regular reflection light when a background of a conveyance belt 105 is irradiated with light and intensity of a detection signal of regular reflection light when an image formed on the conveyance belt 105 is irradiated with light is below a threshold S, and a difference between intensity of a detection signal of diffuse reflection light when the background of the conveyance belt is irradiated with light and intensity of a detection signal of diffuse reflection light when the image formed on the conveyance belt is irradiated with light is equal to or more than the threshold S, a displacement correction pattern is detected on the basis of the detection signal of the diffuse reflection light.

Description

  The present invention relates to an optical writing control apparatus, an image forming apparatus, and a positional deviation correction method for an optical writing apparatus, and more particularly to a pattern detection process in positional deviation correction of an optical writing apparatus.

  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, by aligning the timing of forming an electrostatic latent image by exposing the photosensitive member and the timing of transporting the paper, an image is formed in the correct range of 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. (For example, refer to Patent Document 1). Hereinafter, these adjustment processes are collectively referred to as misalignment correction.

  In the misregistration correction as disclosed in Patent Document 1, a timing detection pattern is formed by the same operation as a normal operation such as exposure of a photosensitive member and development of an electrostatic latent image, thereby reflecting light reflection type light. The period from the start of exposure of the photosensitive member to the reading of the timing detection image pattern is counted by the sensor. And the adjustment process is performed based on the difference between the counted period and the reference value by comparing the period thus counted with a predetermined reference value.

  Further, paying attention to the fact that there is a regular reflection light component and a diffuse reflection light component when reading a pattern with the optical sensor as described above, a method for accurately reading the pattern with one light receiving element has been proposed. (See Patent Document 2). In the method disclosed in Patent Document 2, a plurality of peak positions caused by a mixed component of a regular reflection light component and a diffuse reflection light component are discriminated, and a detection result is adjusted according to the difference between the plurality of peak positions. It is disclosed.

  In addition, even when density fluctuations occur in the pattern image to be formed due to a change in the state of the image forming mechanism such as the photosensitive drum, charger, optical writing device, etc., as described above, noise erroneous detection is eliminated. In order to enable accurate detection of a simple pattern, a method of changing a reference value for determining pattern detection has been proposed (see, for example, Patent Document 3).

  The method of changing the reference value for pattern detection as disclosed in Patent Document 3 is that the difference between the peak values of the output signal of the optical sensor when the pattern is read and the output signal of the optical sensor due to noise is If it is small, it is difficult to properly eliminate false detection.

  The present invention has been made in consideration of the above circumstances, and an object of the present invention is to improve the detection accuracy of a pattern generated in an adjustment process for adjusting the position of an image in an image forming apparatus.

  In order to solve the above problems, an aspect of the present invention is an optical writing control device that forms an electrostatic latent image by irradiating a photoconductor with a light beam, and controls a light source that irradiates the light beam. A light source controller for irradiating a light beam and an image formed by developing the electrostatic latent image and transferred and conveyed on a carrier that moves relative to the photosensitive member. An image detection unit that detects the position of the light source, and a misalignment correction pattern for adjusting the timing at which the light source control unit irradiates the light source with the light beam is formed on the transport body, and is detected at the predetermined position. A correction value for correcting a timing at which the light source is irradiated with a light beam based on a comparison result between a timing acquisition unit that acquires timing and the acquired timing and a predetermined reference value A correction value calculation unit for calculating, wherein the image detection unit detects an image on the carrier based on detection signals of the regular reflection light and the diffuse reflection light of the light irradiated on the carrier, The difference between the detection signal intensity of the specular reflection light when the background of the transport body is irradiated and the detection signal intensity of the specular reflection light when the image formed on the transport body is irradiated is a first threshold value. If it is above, the position deviation correction pattern is detected based on the detection signal of the regular reflection light, and the detection signal intensity of the regular reflection light when the background of the conveyance body is irradiated and formed on the conveyance body A difference between the detected signal intensity of the regular reflection light when the applied image is irradiated is less than a first threshold, and the detection signal intensity of the diffuse reflected light when the background of the carrier is irradiated; When the image formed on the carrier is irradiated If the difference between the detection signal intensity of the scattered reflected light is more than a second threshold value, and detecting the pattern based on a detection signal of the diffuse reflected light.

  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 correcting misalignment of an optical writing control device for forming an electrostatic latent image by irradiating a photosensitive member with a light beam, the light beam being irradiated from a light source. In this way, an electrostatic latent image is formed on the photosensitive member, the image on which the electrostatic latent image is developed and transferred by the carrier is conveyed, and based on a detection signal of the amount of reflected light on the surface of the carrier. A timing at which a positional deviation correction pattern for detecting that the image has reached a predetermined position and adjusting a timing at which the light source is irradiated with the light beam is detected at the predetermined position, and a predetermined reference value; Based on the comparison result, a correction value for correcting the timing of irradiating the light beam to the light source is calculated, and when detecting that the image has reached a predetermined position, the background of the carrier is irradiated. When the difference between the detection signal intensity of the specular reflection light in the case and the detection signal intensity of the specular reflection light when the image formed on the carrier is irradiated is equal to or greater than a first threshold, the specular reflection When the misregistration correction pattern is detected based on a light detection signal, and the detection signal intensity of the regular reflection light when the background of the carrier is irradiated and the image formed on the carrier are irradiated A difference between the detection signal intensity of the regular reflection light and the detection signal intensity of the diffuse reflection light when the background of the transport body is irradiated and less than a first threshold, and formed on the transport body The pattern is detected based on the detection signal of the diffuse reflected light when the difference from the detection signal intensity of the diffuse reflected light when the image is irradiated is equal to or greater than a second threshold value.

  According to the present invention, in the image forming apparatus, it is possible to improve the detection accuracy of the pattern generated in the adjustment process for adjusting the position of the image.

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 sectional side view which shows the structure of 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 pattern drawn in the position shift correction operation | movement which concerns on embodiment of this invention. It is a figure which shows the example of the pattern drawn in the density | concentration correction operation which concerns on embodiment of this invention. It is a figure which shows the structure of the pattern detection sensor which concerns on embodiment of this invention. It is a figure which shows the pattern drawn in the position shift correction operation | movement which concerns on embodiment of this invention, and the detection signal by a pattern detection sensor. It is a figure which shows the example of the toner adhesion amount and detection signal strength which concern on embodiment of this invention. It is a figure which shows the example of the detection signal strength which concerns on embodiment of this invention. It is a figure which shows the example of the detection signal strength which concerns on embodiment of this invention. It is a figure which shows the example of the detection signal strength which concerns on embodiment of this invention. It is a figure which shows the example of the detection signal strength which concerns on embodiment of this invention. It is a flowchart which shows the density | concentration correction | amendment operation | movement and position shift correction | amendment operation | movement which concern on embodiment of this invention. It is a flowchart which shows the determination operation | movement of the pattern detection method 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, 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 is generated in correction of an image writing position in the sub-scanning direction in an optical writing apparatus for forming an electrostatic latent image on a photoreceptor. The gist is to improve the detection accuracy of the image pattern.

  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 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. 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 40. 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 40 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 that transports the paper (recording paper) 104 separated and fed by the paper feed roller 102 and the separation roller 103 from the paper feed tray 101, the transport belt 105 is sequentially transported from the upstream side in the transport direction. A plurality of image forming units (electrophotographic process units) 106BK, 106M, 106C, and 106Y are arranged.

  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 each of the photosensitive drums 109BK, 109M, 109C, and 109Y 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. Further, the expansion and contraction of the conveyor belt due to the temperature change in the apparatus and deterioration with the passage of 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 a misregistration correction pattern transferred onto the conveyance belt 105 by the photosensitive drums 109BK, 109M, 109C, and 109Y, and is used for correction drawn on the surface of the conveyance belt 105. A light emitting element for irradiating the pattern and a light receiving element for receiving reflected light from the correction pattern are included. 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 conveyance belt 105 on the downstream side of the photosensitive drums 109BK, 109M, 109C, and 109Y. .

  Further, in the image forming apparatus 1, the density of the image transferred onto the paper 104 may vary depending on the state change of the image forming units 106 BK, 106 M, 106 C, and 106 Y and the state change of the optical writing device 111. . In order to correct such density fluctuation, a density correction pattern formed in accordance with a predetermined rule is detected, and based on the detection result, driving parameters of the image forming units 106BK, 106M, 106C, and 106Y and the optical writing device 111 are detected. Density correction for correcting the drive parameter 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.

  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 109BK, 109M, 109C, and 109Y of the respective colors is LEDA (LED Array) 130BK, 130M, 130C, and 130Y (hereinafter collectively referred to as LEDA130) as light sources. ).

  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 on / off 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 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 and functions as an optical writing control device that controls the LEDA 130 as a light source.

  The optical writing device 111 according to the present embodiment includes an information processing mechanism 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 performs calculations according to the program.

  The writing 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. In addition to driving the LEDA 130 based on the image information input from the engine control unit 31, the writing control unit 121 drives the LEDA 130 in order to draw a misregistration correction pattern in the misregistration correction process described above. . The correction value generated as a result of this misalignment correction process is stored in the correction value storage unit 126 shown in FIG. 5, and the write control unit 121 uses the LEDA 130 based on the correction value stored in the correction value storage unit 126. The timing for driving is corrected.

  In the misregistration correction process, the count unit 122 starts counting at the same time as the writing control unit 121 controls the LEDA 130 to start exposure of the photosensitive drum 109BK. The count unit 122 stops counting when the sensor control unit 123 detects the pattern based on the output signal of the pattern detection sensor 117.

  As a result, in the above-described misregistration correction process, the count unit 122 controls the LEDA 130 to start 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 detection. Hereinafter, this count value is referred to as a write start count value. 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. Hereinafter, this count value is referred to as a drum interval count value.

  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. When the sensor control unit 123 determines that the misalignment correction pattern has reached the detection position of the pattern detection sensor 117 as described above, the sensor control unit 123 inputs a detection signal to the count unit 122. That is, the sensor control unit 123 functions as an image detection unit, and the count unit 122 functions as a timing acquisition unit that acquires pattern detection timing.

  Further, the sensor control unit 123 detects the density of the density correction pattern formed on the transport belt 105 in accordance with the output signal of the pattern detection sensor 117 in the density correction, and inputs the density to the adjustment value calculation unit 124. .

  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 count unit 122 and the density detection result input from the sensor control unit 123. That is, the correction value calculation unit 124 functions as a reference value acquisition unit and a correction value calculation unit. FIG. 6 shows an example of reference values stored in the reference value storage unit 125. As shown in FIG. 6, the reference value storage unit 125 stores a writing start timing reference value, a drum interval reference value, and a pattern density 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 pattern density reference value is a density reference value of the above-described density correction pattern. That is, the correction value calculation unit 124 compares the density detection result of the density correction pattern input from the sensor control 123 with the pattern density reference value, and calculates a correction value based on the difference between the two.

  Each 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 LEDA 130 with reference to the correction value.

  The correction value generated based on the detection result of the density correction pattern described above is used as a value for correcting the density of the toner image developed on the photosensitive drum 109. Control for correcting the density of the toner image can include adjustment of the exposure amount by the LEDA 130, adjustment of the charging voltage by the charger 110, adjustment of the developing bias by the developing device 112, and the like. Therefore, the correction value calculated for density correction is used not only for the control of the LEDA 130 by the writing control unit 121 but also for the control of the charger 110 and the developing device 112, and the density of the toner image to be developed is adjusted.

  Next, the misregistration correction operation according to the present embodiment will be described with reference to FIG. FIG. 7 illustrates misalignment correction marks (hereinafter referred to as misalignment correction marks) drawn on the conveyance belt 105 by the light source device 281 controlled by the writing control unit 121 in the misalignment correction operation according to the present embodiment. FIG. As shown in FIG. 7, the misregistration correction mark 400 according to this embodiment has 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. 7, the solid line represents a 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. 7, the pattern detection sensor 117 has a plurality (three 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. Accordingly, the optical writing control device 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 the average value of each.

  As shown in FIG. 7, the misalignment correction pattern row 401 includes a start position correction pattern 411 and a drum interval correction pattern 412. Also, as shown in FIG. 7, the drum interval correction pattern 412 is drawn repeatedly. 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. 7, the start position correction pattern 411 according to the present embodiment is a line drawn by 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. That is, the writing start timing reference value stored in the reference value storage unit 125 is the black pattern drawn after the LEDA 130 starts drawing the black pattern on the photosensitive drum 109BK in the start position correction pattern 411. This is a reference value for the period from when it is read by the pattern detection sensor 117 until it is 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. 7, 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 pattern drawn after the LEDA 130 starts drawing the drum interval correction pattern 412 in accordance with the control of the writing control unit 121. Each line included in 412 is a value serving as a reference for a period from when the line is read by the pattern detection sensor 117 and detected by the sensor control unit 123.

  Next, the density correction operation according to the present embodiment will be described with reference to FIG. FIG. 8 is a diagram showing marks (hereinafter referred to as density correction marks) drawn on the transport belt 105 by the light source device 281 controlled by the writing control unit 121 in the density correction operation according to the present embodiment. . As shown in FIG. 8, the density correction mark 500 according to this embodiment includes a black gradation pattern 501, a yellow gradation pattern 502, a magenta gradation pattern 503, and a cyan gradation pattern 504.

  In the present embodiment, the gradation pattern of each color included in the density correction mark 500 is composed of four rectangular patterns with different densities, and these rectangular patterns are arranged in the sub-scanning direction in the order of density. Configured. The gradation patterns for each color are arranged in the sub-scanning direction in the order of black, yellow, magenta, and cyan. As shown in FIG. 8, the density correction mark 500 according to this embodiment is drawn at a position corresponding to the central sensor element 170 among the sensor elements 170 included in the pattern detection sensor 117. Further, in FIG. 8, the density of each pattern is shown by the number of hatches applied to each square pattern.

  In the density correction using the density correction mark 500 shown in FIG. Acquire and perform development bias correction operation. That is, the density gradation reference value stored in the reference value storage unit 125 is a value serving as a reference for the density of each of the four patterns with different densities included in the gradation pattern of each color.

  The misregistration correction mark 400 shown in FIG. 7 and the density correction mark 500 shown in FIG. 8 are continuously drawn in this embodiment. At this time, the density correction mark 500 shown in FIG. 8 is first drawn and transferred onto the transport belt 105, and then the misalignment correction mark 400 is drawn and transferred onto the transport belt 105. Therefore, the correction result of the density correction operation is not reflected at the time of drawing the misregistration correction mark 400, and the pattern density of the misregistration correction mark 400 is not appropriate and may be light or dark. .

  As described above, when the pattern density of the misregistration correction mark 400 is not appropriate, the pattern detection cannot be accurately performed by the density of the drawn pattern when detecting the pattern included in the misregistration correction mark 400. As a result, the positional deviation correction may not be performed accurately. The gist of the present embodiment is to solve such a problem.

  Next, details of the light amount confirmation of the light emitting elements included in the pattern detection sensor 117 according to the present embodiment will be described. FIG. 9 is a side sectional view schematically showing the configuration of the sensor element 170 according to the present embodiment and the state when the sensor element 170 detects a pattern. FIG. 9 is a cross-sectional view of a plane that is perpendicular to the main scanning direction and includes the sensor element 170.

  As shown in FIG. 9, the sensor element 170 according to this embodiment includes a light emitting element 171, a regular reflection light receiving element 172, and a diffuse reflection light receiving element 173. The light emitting element 171 is a light source for which the amount of irradiation light is to be confirmed in the present embodiment. The light emitting element 171 according to the present embodiment is configured by an LED light source that emits a light beam.

  The regular reflection light receiving element 172 is one of light receiving units that receives light emitted from the light emitting element 171 and reflected by the conveyor belt 105, and is irradiated from the light emitting element 171 as indicated by a broken line in FIG. Of the light reflected by the conveyor belt 105, the light is provided at a position and an angle at which regular reflection light is incident.

  The broken line in FIG. 9 shows that only the regular reflection light is incident on the regular reflection light receiving element 172, but it is difficult to cancel the influence of the diffuse reflection light. Therefore, actually, the light including the specular reflection light component and the diffuse reflection light component is incident on the specular reflection light receiving element 172. Thereby, the regular reflection light receiving element 172 outputs a signal corresponding to the amount of light including the regular reflection light component and the diffuse reflection light component.

  The diffuse reflection light receiving element 173 is one of the light receiving elements that receives the light reflected by the conveying belt 105 irradiated from the light emitting element 171, and is irradiated from the light emitting element 171 as indicated by a plurality of arcs in FIG. 9. Of the light reflected by the conveyor belt 105, the diffused reflected light is provided at a position where it can be detected. The diffuse reflection light receiving element 173 outputs a signal corresponding to the amount of diffuse reflection light received.

  With such a configuration, the pattern detection sensor 117 according to this embodiment outputs a light detection signal including a regular reflection light component and a diffuse reflection light component, and a light detection signal including only a diffuse reflection light component. Is possible. Next, the relationship between the misalignment correction pattern according to the present embodiment and the detection signal output from the pattern detection sensor 117 and the manner of confirming the amount of light will be described with reference to FIGS.

  FIG. 10A is a top view of the conveyance belt 105, and shows a state in which a black pattern 415 by the photosensitive drum 109BK and a chromatic pattern 416 by any of the photosensitive drums 109Y, 109C, and 109M are drawn. ing. Further, in FIG. 10A, the spot Q of the laser beam irradiated by the light emitting element 171 and the spot R corresponding to the position where the specular reflection light receiving element 172 receives the reflected light are shown by broken circles. ing.

  FIG. 10B shows an output signal of the diffuse reflection light receiving element 173, that is, a signal corresponding to the light quantity of the diffuse reflection light component. As shown in FIG. 10B, in the case of the black pattern 415, since the diffuse reflection does not occur as in the case of the white background, the signal remains flat. In the case of the chromatic pattern 416, diffuse reflection occurs when the pattern is conveyed and reaches the spot Q, and the signal intensity starts to increase as shown in FIG. Then, at the timing when the center of the pattern reaches the center of the spot Q, the irradiation range of the pattern becomes maximum, and the signal intensity reaches a peak, that is, a maximum value.

  FIG. 10C shows the signal intensity when only the regular reflection light component is detected. As shown in FIG. 10C, since the regular reflection light is detected while the white background is illuminated, the signal rejection is flat. When the pattern reaches the spot R, the specularly reflected light component starts to decrease, so that the signal intensity starts to drop. At the timing when the center of the pattern reaches the center of the spot R, the specularly reflected light component becomes the lowest, and the drop of the pattern reaches a peak, that is, a minimum value.

  FIG. 10D shows an output signal of the regular reflection light receiving element 172, that is, a signal corresponding to the amount of light including the regular reflection light component and the diffuse reflection light component. As shown in FIG. 10 (d), the output signal of the regular reflection light receiving element 172 is a signal obtained by synthesizing FIG. 10 (b) and FIG. 10 (c).

  As shown in FIG. 10D, the output signal of the regular reflection light receiving element 172 is provided with a threshold value S. The threshold value S is appropriately set by the sensor control unit 123 according to a parameter at the time of pattern detection. The sensor control unit 123 detects two timings when the output signal of the regular reflection light receiving element 172 becomes the threshold S when detecting the pattern in the positional deviation correction, and reaches the pattern based on the average value of the timings. Detect timing. still,

For example, when detecting the black pattern 415 in FIG. 10D, the sensor control unit 123 detects the arrival timing of the black pattern 415 based on the average value of the timings t _S1 and t _S2 . In addition to the case where the threshold value S is used, the timing at which the drop of the signal reaches a peak, such as t _P1 and t _P2 shown in FIG.

Since the chromatic pattern 416 is a combination of the regular reflection light component and the diffuse reflection light component as described above, the arrival timing of the pattern is accurately obtained from the average value of t _S3 and t _S4. It may not be possible. To detect the arrival timing of the chromatic patterns as accurately as possible, the width L ₁ in the sub-scanning direction of the pattern is set diameter equal or below it and the spot R.

This is to reduce the detection error by narrowing the arrival timing width by drawing the pattern as thin as possible. The distance L ₂ between adjacent patterns is set larger than the diameter of the spot Q. Thereby, it is possible to prevent two different patterns from being irradiated at the same time, and diffuse reflected light from the two patterns to be reflected at the same time, so that the signal intensity of the detection signal becomes an unexpected value.

  The sensor element 170 according to the present embodiment has a function of separately outputting the detection signal of the regular reflection light receiving element 172 and the detection signal of the diffuse reflection light receiving element 173. As described above, the detection signal of the regular reflection light receiving element 172 is a graph shown in FIG. 10 (d), and the detection signal of the diffuse reflection light receiving element 173 is a graph shown in FIG. 10 (b). Then, the sensor control unit 123 detects the image on the carrier based on the detection signal of the regular reflection light receiving element 172 and the detection signal of the diffuse reflection light receiving element 173.

  FIGS. 10A to 10D are examples in the case where the black pattern 415 and the chromatic color pattern 416 are toner images having a predetermined density. The signal intensity of the detection signal output from the sensor element 170 is as follows. It varies depending on the density of the toner image. 11A and 11B show the relationship between the density of the toner image and the signal intensity of the detection signal.

  FIG. 11A is a graph showing the relationship between the signal intensity of the detection signal of the black toner image, that is, the black pattern 415, and the toner density. It is strength. In the case of black toner, as the toner adhesion amount increases, the detection signal intensity of the regular reflection light receiving element 172 decreases, and the detection signal intensity of the diffuse reflection light receiving element 173 does not change much. This is because when the toner adhesion amount is increased, light is absorbed by the toner and the reflected light is reduced, so that both the regular reflection voltage and the diffuse reflection voltage are reduced. However, since the amount of toner adhesion increases and the density of the toner image becomes uniform, the amount of surface reflection increases, so the diffuse reflection voltage slightly increases according to the amount of toner adhesion.

  FIG. 11B is a graph showing a relationship between the color toner image, that is, the signal intensity of the detection signal of the chromatic pattern 416 and the toner image, where the broken line indicates the diffuse reflection light and the solid line indicates the regular reflection light. Signal strength. In the case of color toner, the intensity of the detection signal of the regular reflection light receiving element 172 decreases as the toner adhesion amount increases, but starts increasing from a certain point. The detection signal intensity of the diffuse reflection light receiving element 173 increases as the toner adhesion amount increases. This is because in color toner, as the amount of toner adhering increases, the light that is not absorbed by the toner diffuses, resulting in an increase in diffuse reflected light, and a portion of the reflected light enters the light receiving unit 24. This is because the light is added to the specular reflection light receiving element 172 due to the positive voltage.

  In both black toner and color toner, if the toner adhesion amount is small, the difference in detection signal intensity from the background of the conveyor belt 105 is small, and the pattern of the specular reflection light or diffuse reflection light can be reduced. It is difficult to detect. In the case of color toner, as the toner adhesion amount increases, the signal intensity due to detection of specular reflection light approaches the signal intensity at the time of belt background irradiation, and thus it is difficult to detect the pattern. The gist of the present embodiment is to optimize a pattern detection method according to such toner density.

  FIG. 12A is a diagram showing a detection signal of a pattern arranged as shown in FIG. 10A and a detection signal when the pattern density is low. In FIG. 12A, the threshold value S is set according to the low density of the detection signal, and is set to an intermediate value between the signal intensity at the time of belt background irradiation and the peak value by pattern detection. . Further, FIG. 12A shows a case where there is a signal corresponding to the noise N.

  In the case of FIG. 12A, the pattern can be detected by the threshold value S, but since the difference between the peak value by the pattern detection and the noise peak is small, noise is eliminated by the threshold value S and only the pattern is detected. Difficult to do. As described above, when the difference between the peak value due to pattern detection and the signal intensity at the time of belt background irradiation is so small that the difference between the peak value due to pattern detection and the peak value of noise becomes small, the sensor control unit 123 performs noise filtering. As shown in FIG. 12B, the signal is corrected so that only the pattern is detected.

The noise filter used for the signal processing from the state of FIG. 12A to the state shown in FIG. 12B is a filter that increases the band cut by the high frequency component. If the noise filter is strengthened, the misregistration correction pattern may be detected as noise. Therefore, the sensor control unit 123 determines that the difference between the peak value of the pattern detection signal and the signal intensity at the time of belt background irradiation is a predetermined value. only if less than the threshold S _1, to adapt the filter for correcting the signal to FIG 12 (b) from Fig. 12 (a).

FIG. 13 is a diagram illustrating a detection signal when the pattern density is lower than that in FIG. In the case of FIG. 13, there is almost no difference between the peak value of the pattern detection signal and the signal intensity at the time of belt background irradiation, and pattern detection is almost impossible. Accordingly, the sensor control unit 123, when the difference between the signal strength of the peak value and the belt background radiation of the detection signals of the pattern is less than the predetermined threshold value S _2, the positional deviation correcting operation to the user ended in error Notice. Thereby, it is possible to prevent erroneous misalignment correction from being executed.

  FIG. 14 is a diagram showing a detection signal when the pattern density is ideal. In the case of FIG. 14, there is a sufficient difference between the peak value of the pattern detection signal and the signal intensity at the time of belt background irradiation. Therefore, it is possible to detect a black pattern and a color pattern by setting a threshold value S at an intermediate point between the peak value obtained by pattern detection and the signal intensity at the time of belt background irradiation, and thereby detect noise N. Therefore, it is possible to appropriately perform misalignment correction.

  FIG. 15 is a diagram showing a detection signal when the pattern density is higher than that in FIG. As shown in FIG. 15, in the case of black toner, as the density increases, the difference between the peak value of the pattern detection signal and the detection signal at the time of belt background irradiation increases, so the peak value of the pattern detection signal and the belt By setting the threshold value S in the middle of the detection signal at the time of background irradiation, the pattern can be easily detected.

  On the other hand, in the case of the color toner, when the misregistration correction pattern becomes dark, as described in FIG. 11, the diffuse reflection light becomes strong, and as a result, the detection signal intensity of the regular reflection light receiving element 172 increases, and as a result, the pattern The difference between the peak value of this detection signal and the detection signal at the time of belt background irradiation becomes small, making it difficult to detect the pattern.

On the other hand, in the case of color toner, by utilizing the fact that diffuse reflected light becomes stronger as the pattern density becomes higher, by setting a threshold value S ′ for the peak value of the detection signal intensity of the diffuse reflected light receiving element 173, It is possible to detect the pattern. Therefore, if the sensor control unit 123, for example diffuse reflection light receiving element 173 of the detection signal peak value of the intensity and the belt background difference between the detection signal at the time of irradiation predetermined threshold S ₃ or more, the diffuse reflection light receiving element 173 The pattern is detected based on the output signal. Note that the threshold value S ′ can also be an intermediate point between the peak value obtained by pattern detection and the signal intensity at the time of belt background irradiation, similarly to the threshold value S.

  As described above, in the optical writing control device 120 according to the present embodiment, the sensor control unit 123 determines a detection method for detecting each pattern included in the misregistration correction mark 400 according to the pattern density. . Specifically, since the detection of the density correction mark 500 has already been completed at the time of detection of the misregistration correction mark 400, a detection method for detecting the misregistration correction mark 400 is determined using the detection result. To do. Thereby, erroneous detection of the pattern due to the density of the pattern can be avoided.

  FIG. 16 is a flowchart showing operations of density correction processing and positional deviation correction processing according to the present embodiment. As shown in FIG. 16, first, the writing control unit 121 starts pattern drawing of the density correction mark 500 and the positional deviation correction mark 400 (S1601). When the pattern transferred onto the conveyor belt 105 reaches the detection position of the pattern detection sensor 117, the sensor control unit 123 starts pattern detection based on the detection signal of the pattern detection sensor 117 (S1602).

  As described above, since the direction correction mark 500 is drawn first, when the pattern is detected by the sensor control unit 123, the adjustment value calculation unit 124 executes density correction processing (S1603). After completing the density correction processing, the adjustment value calculation unit 124 stores the density correction result in the correction value storage unit 126 (S1604).

  At this time, the adjustment value calculation unit 124 also notifies the sensor control unit 123 of the density detection result of the density correction mark 500 and the success or failure of density correction. The notified density detection result is the density detection result of each color of CMYK. The peak detection value of the detection signal intensity of the misregistration correction mark 400 drawn following the density correction mark 500 and the signal at the time of belt background irradiation It is a difference in strength.

  In the density correction process, the detection result of the density correction mark 500 as shown in FIG. 8 is acquired. Therefore, the adjustment value calculation unit 124 can predict the peak value of the detection result signal intensity of the misregistration correction mark 400 based on the detection result, the charging bias at the time of pattern drawing, and the exposure intensity.

  In this way, the adjustment value calculation unit 124, based on the detection signals of the regular reflection light receiving element 172 and the diffuse reflection light receiving element 173, the peak value by the pattern detection of the misalignment correction mark 400 and the signal at the time of belt background irradiation. The difference from the intensity is obtained and notified to the sensor control unit 123. The success or failure of the density correction is a result of determining that the density correction has failed when the density correction cannot be executed due to toner exhaustion or the like, and is normally determined to be successful.

  In addition to the predicted value calculated as described above, the density detection result input to the sensor control unit 123 by the adjustment value calculation unit 124 is formed with a stepwise density for each color as shown in FIG. Of the gradation patterns, it is also possible to use a detection result of a pattern drawn with the same density as or the closest density to which the positional deviation correction pattern is drawn.

  The sensor control unit 123 that has acquired the density detection result from the adjustment value calculation unit 124 sets the pattern detection method as described in FIGS. 12A and 12B (S1605). The process of S1605 will be described in detail later. The sensor control unit 123 detects a pattern according to the set pattern detection method and inputs a detection signal to the count unit 122. As a result, the adjustment value calculation unit 124 executes the positional deviation correction process according to the count result by the count unit 122 (S1606), stores the correction result in the correction value storage unit 126 (S1607), and ends the process.

  Next, the setting operation of the pattern detection method according to S1605 of this embodiment will be described with reference to the flowchart of FIG. As shown in FIG. 17, the sensor control unit 123 first determines whether or not the density correction is successful (S1701), and if the density correction fails (S1701 / NO), notifies the user of an error and stops the correction operation ( S1713), the process is terminated.

If the density correction is successful (S1701 / YES), the sensor control unit 123 then selects one from the density detection results of each color notified as the result of the density correction, and FIG. as described in b), the detection result of the specular reflection light receiving element 172, the difference between X ₁ of the signal strength of the peak value and the belt background irradiation by pattern detection confirms whether the threshold value S ₁ or more (S1702). The threshold S ₁ is FIG. 12 (a), the well as a threshold value for determining the applicability necessity of filter for cutting a high frequency component as described (b), the as described in FIG. 14, properly This is a threshold value for determining whether or not pattern detection is possible.

When X ₁ is was _{S 1} or more (S1702 / YES), since it is possible to correct the pattern detection as described in FIG. 14, the sensor control unit 123, based on the output signal of the specular reflection light receiving element 172 Then, it is determined to detect the pattern (S1703), and a threshold value S is set at an intermediate point between the peak value by pattern detection and the signal intensity at the time of belt background irradiation (S1704).

On the other hand, when _{X 1} is less than _{S 1} (S1702 / NO), then, the sensor control unit 123, as described in FIG. 15, the detection result of the diffuse reflection light receiving element 173, a peak by the pattern detection It is confirmed whether or not the difference Y ₁ between the value and the signal intensity at the time of belt background irradiation is equal to or greater than the threshold value S ₃ (S 1706). The threshold S _3, as described in FIG. 14 is a threshold for determining whether to use the detection result of the diffuse reflected light when the concentration of the pattern dark.

Y ₁ is, when was the threshold _{S 3} above (S1706 / YES), as described with reference to FIG. 15, since it is possible to detect by diffuse reflection light, the sensor control unit 123, the diffuse reflection light receiving element 173 It is determined to detect a pattern based on the output signal (S1707), and a threshold value S ′ is set at the midpoint between the peak value obtained by pattern detection and the signal intensity at the time of belt background irradiation (S1708).

Y ₁ is, if less than the threshold value _{S 3} (S1706 / NO), then, the sensor control unit 123, as described with reference to FIG. 13, the detection result of the specular reflection light receiving element 172, a peak by the pattern detection the difference _{X 2} between the signal strength at the value and the belt background radiation confirms whether the threshold value _{S 2} or more (S1709). The threshold S _2, as described in FIG. 13, a threshold value for determining that the pattern is thin to a degree that can not be detected in the pattern.

X ₂ is, if it was the threshold value _{S 2} or more (S1709 / YES), the sensor control unit 123, FIG. 12 (a), determines that it is possible to detect the pattern of the embodiment as described in (b) . Therefore, the sensor control unit 123 determines to detect the pattern based on the output signal of the regular reflection light receiving element 172 (S1710), and at an intermediate point between the peak value by pattern detection and the signal intensity at the time of belt background irradiation. A threshold value S is set (S1711), and a filter for cutting high frequency components as described in FIGS. 12A and 12B is set (S1712).

X ₂ is, if less than the threshold value _{S 2} (S1709 / NO), the sensor control unit 123 determines that it is impossible to pattern detection, and notifies the error to the user (S1713), and ends the process .

  Upon completion of any of S1704, S1708, and S1712, the sensor control unit 123 determines whether or not the processing for all CMYK colors has been completed (S1705). If not completed (S1705 / NO), an unselected The process from S1702 is repeated for the color. On the other hand, if all the CMYK colors have been processed (S1705 / YES), the process is terminated.

  According to the operation shown in FIG. 17, since the determination is based on the difference between the peak value by pattern detection and the detection intensity at the time of belt background irradiation, it is determined whether the pattern is a black toner pattern or a color toner pattern. Regardless, it is possible to determine whether pattern detection is possible. Since the pattern detection method is determined according to each pattern detection result, it is possible to prevent erroneous detection of the pattern and to appropriately perform the positional deviation correction.

  As described above, according to the optical writing control device 120 according to the present embodiment, it is possible to improve the detection accuracy of the pattern generated in the adjustment process for adjusting the position of the image in the image forming apparatus.

  In the above-described embodiment, as illustrated in FIG. 3, a system in which an image is directly transferred from the photosensitive drum 109 onto the sheet surface of the sheet conveyed by the conveyance belt 105 has been described as an example. That is, the case where the conveyance belt 105 as a conveyance body conveys a sheet has been described as an example.

  In addition, the above embodiment can also be applied to an intermediate transfer method in which an image formed by being transferred from the photosensitive drum 109 onto the conveying belt 105 is further transferred onto the paper surface. The same effect can be obtained. In this case, the conveyance belt 105 which is an intermediate transfer belt conveys an image as a conveyance body.

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 write controller,
122 counting part,
123 sensor control unit,
124 correction value calculation unit,
125 reference value storage unit,
126 correction value storage unit,
130, 130BK, 130C, 130M, 130Y LEDA
170 sensor element,
171 light emitting element,
172 specular reflection light receiving element,
173 diffuse reflection light receiving element,
400 Misalignment correction mark,
401 misalignment correction pattern sequence,
411 start position correction pattern,
412 Drum interval correction pattern,
413 Sub-scanning direction correction pattern,
414 Main scanning direction correction pattern 500 Density correction mark 501 Black gradation pattern 502 Yellow gradation pattern 503 Magenta gradation pattern 504 Cyan gradation pattern

JP 2008-299311 A JP 2008-180946 A JP 2003-280315 A

Claims (8)

An optical writing control device for irradiating a photoconductor with a light beam to form an electrostatic latent image,
A light source controller that controls a light source that emits the light beam to irradiate the light beam;
An image detection unit configured to detect an image formed by developing the electrostatic latent image and transferred and conveyed on a conveyance body that moves relative to the photoconductor at a predetermined position;
A timing acquisition unit for acquiring a timing detected at the predetermined position, wherein a positional deviation correction pattern for adjusting a timing at which the light source control unit irradiates the light source with a light beam is formed on the carrier;
A correction value calculation unit that calculates a correction value for correcting the timing of irradiating the light source with a light beam based on a comparison result between the acquired timing and a predetermined reference value;
The image detection unit
Detecting the image on the carrier based on the detection signals of the regular reflection light and diffuse reflection light of the light irradiated on the carrier,
The difference between the detection signal intensity of the specular reflection light when the background of the transport body is irradiated and the detection signal intensity of the specular reflection light when an image formed on the transport body is irradiated is first. When the threshold value is greater than or equal to the threshold, the misregistration correction pattern is detected based on the detection signal of the regular reflection light,
The difference between the detection signal intensity of the specular reflection light when the background of the transport body is irradiated and the detection signal intensity of the specular reflection light when an image formed on the transport body is irradiated is first. The detection signal intensity of the diffuse reflected light when it is less than the threshold and the background of the transport body is irradiated and the detection signal intensity of the diffuse reflected light when the image formed on the transport body is irradiated The optical writing control device detects the pattern based on the detection signal of the diffusely reflected light when the difference is equal to or greater than a second threshold value.   The image detection unit includes a detection signal intensity of the specular reflection light when the background of the transport body is irradiated and a detection signal intensity of the specular reflection light when an image formed on the transport body is irradiated. The diffuse reflection when the difference between the detection signal intensity of the diffuse reflected light when the background of the transport body is irradiated and the image formed on the transport body is irradiated When the difference between the light detection signal intensity is less than the second threshold and the background of the carrier is irradiated, the detection signal intensity of the regular reflection light and the image formed on the carrier are irradiated. When the difference between the detected signal intensity of the specularly reflected light and the third threshold is equal to or higher than the first threshold, the specularly reflected light detection signal to which a filter that cuts high frequency components is applied is used. Optical writing control characterized by pattern detection Location.   The image detection unit includes a detection signal intensity of the specular reflection light when the background of the transport body is irradiated and a detection signal intensity of the specular reflection light when an image formed on the transport body is irradiated. 4. The optical writing control device according to claim 3, wherein when the difference is less than a third threshold value that is lower than the first threshold value, the misregistration correction operation is stopped. 5. The light source control unit controls the light source so that the misregistration correction pattern is formed after a density correction pattern for correcting the density of an image formed by developing the electrostatic latent image;
The correction value calculation unit calculates a correction value for correcting a parameter contributing to the density of an image formed by developing the electrostatic latent image based on the detection result of the density correction pattern, and Output a value corresponding to the detection signal intensity of the regular reflection light when the density correction pattern is irradiated and the detection signal intensity of the diffuse reflection light when the density correction pattern is irradiated,
The top of the image detection unit is to determine whether to use regular reflection light or diffuse reflection light when detecting the misregistration correction pattern based on the value output from the correction value calculation unit. 4. The optical writing control device according to any one of items 1 to 3.   The correction value calculation unit irradiates the predicted value of the detection signal intensity of the regular reflection light and the positional deviation correction pattern when the positional deviation correction pattern is irradiated based on the detection result of the density correction pattern. 5. The optical writing control apparatus according to claim 4, wherein a predicted value of the detection signal intensity of the diffuse reflected light in the case of being calculated is calculated and the calculation result is output. The light source control unit controls the light source so that a plurality of patterns having different densities are formed as the density correction pattern;
The optical writing control apparatus according to claim 4, wherein the correction value calculation unit outputs a detection result of a predetermined pattern among the plurality of different patterns.   An image forming apparatus comprising the optical writing control device according to claim 1. A method of correcting misalignment of an optical writing control device for forming an electrostatic latent image by irradiating a photoconductor with a light beam,
An electrostatic latent image is formed on the photoreceptor by irradiating the light beam from a light source,
The electrostatic latent image is developed and transferred by a carrier, and the transferred image is conveyed.
Detecting that the image has reached a predetermined position based on a detection signal of the amount of reflected light on the surface of the carrier,
The light source is irradiated with the light beam based on a comparison result between a timing at which a positional deviation correction pattern for adjusting the timing at which the light source is irradiated with the light beam is detected at the predetermined position and a predetermined reference value. Calculate the correction value to correct the timing,
In detecting that the image has reached a predetermined position,
The difference between the detection signal intensity of the specular reflection light when the background of the transport body is irradiated and the detection signal intensity of the specular reflection light when an image formed on the transport body is irradiated is first. When the threshold value is greater than or equal to the threshold, the misregistration correction pattern is detected based on the detection signal of the regular reflection light,
The difference between the detection signal intensity of the specular reflection light when the background of the transport body is irradiated and the detection signal intensity of the specular reflection light when an image formed on the transport body is irradiated is first. The detection signal intensity of the diffuse reflected light when it is less than the threshold and the background of the transport body is irradiated and the detection signal intensity of the diffuse reflected light when the image formed on the transport body is irradiated If the difference is greater than or equal to a second threshold value, the pattern is detected based on the diffuse reflection light detection signal.

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