JP2010145626A - Image forming apparatus, color slippage correcting method, program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and method capable of appropriately correcting color slippage even when a color order of toner patterns is reversed. <P>SOLUTION: The apparatus includes: a detection part 500 detecting toner patterns; a measuring part 510 measuring time from a detected reference to each color toner pattern; a storage part 520 storing measurement values measured for all colors in ascending order; a color order detection part 530 detecting the color order of the toner patterns by specifying one color, judging which order of the measurement values stored in the storage part 520 the measurement values of the other colors measured for the toner patterns excluding the color correspond to, and detecting the order of the specified color; a judgement part 540 judging whether or not the detected color order is the same as a regular color order; a color order correcting part 550 executing a correction of exchanging the order of the measurement values measured based on the regular color order when the color order is different; and a color slippage correcting part 560 calculating a correction amount so as to be each target value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides an image forming apparatus, a color misregistration correction method, and a color misregistration correction method that can reliably perform color misregistration even when a large color misregistration occurs and the toner patterns on the transfer belt are formed in an order different from the correct order. The present invention relates to a computer-readable program for realizing the method and a recording medium on which the program is recorded.

  An electrophotographic color image forming apparatus irradiates a plurality of photoconductors charged by a charging unit with laser light corresponding to each color from an exposure device to form a latent image on each photoconductor. A device that prints and outputs a color image on paper by applying it to a transfer belt, transferring it to a transfer belt, transferring it to paper, and then applying heat and pressure to the paper to fix it on the paper. It is.

  In this color image forming apparatus, since color shift occurs due to environmental conditions such as temperature and humidity and deterioration with time, a predetermined toner pattern is appropriately formed on each transfer belt with toner of each color, and this toner pattern is optically converted. By detecting using a sensor of the formula, the amount of deviation in each section is calculated by factors such as registration deviation in the main scanning direction and sub-scanning direction, magnification deviation, skew (distortion), and bending, and each deviation is fed back. By performing the correction, color misregistration can be reduced (see, for example, Patent Document 1).

In the image forming apparatus described in Patent Document 1, the photosensitive member is charged, the photosensitive member is exposed in accordance with a signal of the mark image to form an electrostatic latent image, developed by a developing device, and then marked on the transfer belt. Transfer the image, read it with a photo sensor, detect position shift and density error from the signal output from the photo sensor, control the writing timing to correct the position, control the laser power to correct the image density To do.
JP-A-2005-352291

  Even when the above-described color misregistration correction is performed, an unexpected large color misregistration due to a large distortion or the like of the transfer belt may occur.

  For example, a cyan toner pattern is originally formed between a black toner pattern and a magenta toner pattern. If a large color shift occurs in cyan for some reason, a yellow toner pattern and a black toner pattern are formed. In some cases, the toner pattern is formed between the toner patterns. In this way, when the color order of the toner pattern is reversed and formed in an order different from the correct order, if the reflective sensor is a sensor capable of color detection, it can be detected that the order is abnormal. .

  However, since a normal sensor provided for correction of the image forming apparatus cannot perform color detection, it is impossible to detect that the color order is reversed. In such a case, cyan in the toner pattern is erroneously recognized as black, and correction is performed based on this erroneous recognition, resulting in an adverse effect on the output image. That is, in the conventional technique, when such a large color shift occurs, the toner patterns formed on the transfer belt cannot be recognized in the correct order, and the color shift correction cannot be performed correctly. .

  In view of the above problems, the present invention detects a count value between patterns for one cycle of a toner pattern formed on a transfer belt during a color misregistration correction process, and a pattern when the nth color is erased in color order. The control for calculating the count value between the patterns is carried out for all the orders, and then the toner pattern is formed on the transfer belt in a state where any one of the colors is actually erased, and the count value between the patterns is detected. The detected count value is compared with the previously calculated count value to determine what order the erased color is in color order, and this is performed until the color order of all the toner patterns to be formed can be determined This makes it possible to determine whether the color order is reversed.

  When the color order is reversed, the color order correction is performed to change the order of the count values so that the regular color order is defined in advance, and the toner pattern is set to form a constant interval. A difference between the target count value and the color order corrected count value is obtained as a correction amount, and color misregistration correction is performed based on the correction amount. In this way, even when the color order of the toner pattern formed on the transfer belt is reversed due to a large color shift, the color shift correction can be performed appropriately.

  Therefore, the above problem can be solved by providing the image forming apparatus of the present invention.

  An image forming apparatus according to the present invention includes an image forming unit that forms an image, a reference pattern, and a toner pattern of each color, a detection unit that sequentially detects the reference pattern and the toner pattern of each color, and a time from the reference pattern to the toner pattern of each color. Alternatively, the image forming apparatus includes a measurement unit that measures a distance and performs color misregistration correction. The image forming apparatus includes a storage unit that stores measurement values measured for all colors in order from the smallest one, designates one color, and sets the reference pattern to each of the other colors excluding the color. An instruction for sequentially forming toner patterns is given to the image forming unit, and it is determined which measurement value for each of the other colors measured by the measurement unit matches or is closest to the measurement value stored in the storage unit. The color order detection unit that detects the color order of the toner pattern to be formed by detecting the order of the specified color, and whether the detected color order is the same as the regular color order defined in advance. If it is determined that the determination unit is different from the determination unit, the color order correction unit that performs correction to change the order of measurement values measured based on the normal color order, and the determination unit Normal color order after correction by the color order correction unit The difference between the target value in the same order and the measured measurement value is calculated as a correction amount so that each measurement value formed and measured for each color becomes each target value, and color misregistration correction is performed based on the correction amount And a color misregistration correction unit.

  Further, the storage unit can store a set of measurement values remaining when the n-th (n is a natural number) measurement value is deleted as a correspondence table in association with the order n. In this case, the color order detection unit detects the order of the designated colors based on the measurement values and the correspondence table for each color other than the nth color.

  By creating and storing the correspondence table, it is possible to easily detect the order of the designated colors in the color order detection unit.

  When determining which order of measurement values stored in the storage unit is the closest to the measurement value for each of the other colors detected by the detection unit and measured by the measurement unit, the color order detection unit The absolute value of the difference between the measured value and each of the set of measured values corresponding to each order in the correspondence table is added to obtain a total value, and the total value obtained for each order is compared to the smallest order Can be detected as the order in the color order of the toner pattern to be formed.

  The color order detection unit designates one color, gives an instruction to sequentially form toner patterns of other colors excluding the color following the reference pattern, and the measurement values for the other colors are stored in the storage unit. It is possible to execute a process for determining the order of the designated color by determining which stored measurement value matches or is closest to each other.

  When a pattern of four colors is formed in total, the processing for detecting the order of the specified colors described above can be performed for all three colors, but the order of all the colors can be known. It becomes possible to grasp.

  In the present invention, in addition to the image forming apparatus, a color misregistration correction method including each processing step performed by the image forming apparatus can also be provided. Also, a computer-readable program for realizing the color misregistration correction method can be provided, and the program can be provided as a recording medium on which the program is recorded.

  FIG. 1 is a diagram illustrating a hardware configuration of an image forming unit constituting the image forming apparatus according to the present embodiment. This hardware configuration is the same as that of a conventional electrophotographic color image forming apparatus.

  The image forming unit 100 irradiates the charged surfaces with laser light by irradiating the charged surfaces of the four photosensitive drums 110, the charging units 120 for charging the photosensitive drums 110, and the charged surfaces of the charged photosensitive drums 110. Primary transfer in a state in which an exposure device 130 that forms an image, a developing unit 140 that develops a latent image formed on each photosensitive drum 110 into toner images of different colors, and toner images of different colors are superimposed on each other An intermediate transfer belt 150, a primary transfer roller 160 for transferring a toner image to the intermediate transfer belt 150, and a cleaning unit 170 for removing toner remaining on the photosensitive drum 110 after transfer. .

  In addition, the image forming unit 100 includes a driving roller 180 that moves the intermediate transfer belt 150 in a predetermined direction (here, a direction indicated by an arrow A), a subordinate roller 190 that rotates as the intermediate transfer belt 150 moves, The image forming apparatus includes a fixing unit 210 that transfers the toner image transferred onto the transfer belt 150 to the sheet 200 and applies heat and pressure to fix the toner image on the sheet.

  In this image forming apparatus, in addition to the image forming unit 100, a paper feed tray 220 that accommodates paper 200, a paper feed roller 230 that takes out the paper 200 one by one and supplies it to the intermediate transfer belt 150, and a toner image are fixed. And a paper discharge roller (not shown) for discharging the paper 200.

  The image forming apparatus has four photosensitive elements for black (K), cyan (C), magenta (M), and yellow (Y) on the intermediate transfer belt 150 along the moving direction of the intermediate transfer belt 150. Body drums 110 are arranged in parallel. The intermediate transfer belt 150 is supported by two axes of a driving roller 180 and a slave roller 190. This may be stretched by a plurality of rollers, but is preferably stretched by two axes in order to reduce the size as much as possible.

  As the intermediate transfer belt 150 moves, the photosensitive drums 110 and the primary transfer rollers 160 rotate, and the black toner image, the cyan toner image, the magenta toner image, and the yellow toner image are sequentially transferred onto the intermediate transfer belt 150. The image is transferred and transferred on the intermediate transfer belt 150 in a state where the images are sequentially and accurately superimposed, thereby forming a full-color image.

  The full color image formed on the intermediate transfer belt 150 is transferred by the secondary transfer roller 240 to the paper fed by the paper feed roller 230. The full color image transferred onto the paper is heated and pressed by the fixing unit 210, fixed on the paper, and discharged by a paper discharge roller. Transfer residual toner adhering to the surface of the intermediate transfer belt 150 after the secondary transfer is removed by the cleaning unit 250.

  An electrophotographic color image forming apparatus is required to appropriately stabilize the image density of each color in order to obtain a high-quality full-color image. For this reason, a toner pattern serving as a density reference is formed on an image carrier such as the photosensitive drum 110, the intermediate transfer belt 150, and the conveyance belt, and the density of the toner pattern is detected by the optical reflective sensor 260. Based on the detected density, values adjusted with respect to image forming conditions that affect the toner density, such as charging potential, exposure intensity, developing bias voltage, transfer voltage, and toner replenishment amount, are fed back to the image forming unit 100.

  In addition, this electrophotographic color image forming apparatus has an attachment error of each of the image forming units 100, an exposure apparatus adjustment error, distortion, changes in environment and time, uneven rotation of the photosensitive drum, uneven conveyance of the image carrier, A color shift occurs in the formed image due to fluctuations caused by disturbance of the paper 200 or the like. Therefore, the position of each color of the toner pattern to be a mark of each color on the image carrier is detected by the optical reflective sensor 260, and the color misregistration of each color is calculated from the detection result to adjust the exposure timing and the like. The value is fed back to the image forming unit 100.

  FIG. 2 is a diagram showing an example of the configuration of the reflective sensor 260. The reflective sensor 260 is disposed to face the image carrier 300 and detects the density of the toner pattern 310 formed on the surface of the image carrier 300 and the position of each color. The reflective sensor 260 includes a light-emitting element 270 such as an infrared light-emitting diode, light-receiving elements 280a and 280b such as phototransistors or photodiodes, and a holder 290 that accommodates these elements. The light emitting element 270 makes light incident on the surface of the image carrier 300 at a predetermined angle, and the light receiving elements 280a and 280b are arranged to receive light reflected at the predetermined angle.

  Light emitted from the light emitting element 270 is reflected by the toner pattern and detected by the light receiving elements 280a and 280b. The light receiving elements 280a and 280b detect regular reflection light from the toner pattern 310 and diffuse reflection light. As described above, the light receiving elements 280a and 280b detect the two reflected lights, so that it is possible to detect black and color from low density to high density. On the other hand, the position detection of each color is performed only by the light receiving element 280a that detects regular reflection light. Note that the detection value of the specularly reflected light greatly fluctuates due to the deformation of the image carrier 300.

  With reference to FIG. 3, a hardware configuration of a control unit configuring the image forming apparatus will be described. The control unit includes a CPU 400, a ROM 410, a RAM 420, an I / F unit 430, a writing unit 440, an I / O unit 450, and a counter 460 as hardware.

  The CPU 400 controls the entire apparatus according to the ROM 410 in which various control programs are recorded. The RAM 420 includes various necessary parameters and a work area area for the entire apparatus. The I / F unit 430 is connected to an external device via a wired LAN, wireless LAN, USB, or the like. When image data is sent from the external device, the writing unit 440 separates the image signals of the respective colors into an image digital signal. Are sent to the exposure apparatus 130 in accordance with the toner density and color misregistration parameters stored in the RAM 420.

  When performing toner density control and color misregistration control, first, a toner pattern for detecting toner density and color misregistration via the writing unit 440 and the exposure device 130 is placed on the intermediate transfer belt 150 moved at a constant speed. It is formed at the timing stored in the RAM 420. The toner pattern formed on the intermediate transfer belt 150 is detected as reflected light by the reflective sensor 260, toner density and color misregistration information is obtained from the reflected light, and the obtained toner density and color misregistration information is used as the I / O unit. 450, and the CPU 400 performs a calculation based on the information. The calculation performed by the CPU 400 is a correction amount calculation, and the calculated correction amount is stored in the RAM 420 and used in the next image forming operation.

  The counter 460 is a counter for counting the toner density, the number of color misregistration detection toner patterns formed on the intermediate transfer belt 150, and the time interval between the color misregistration detection toner patterns. Although the time interval is used here, it may be a distance between patterns.

  Here, with reference to FIG. 4, an example of formation of a toner pattern formed on the intermediate transfer belt 150 and a positional relationship between the toner pattern and the reflective sensor 260 will be described. The density control toner patterns representing the gradations of the respective colors such as yellow, black, cyan, and magenta formed on the intermediate transfer belt 150 are formed so as to be arranged. Those with predetermined conditions of 20,..., 100% are used.

  When these patterns are detected by the reflective sensor 260, the CPU 400 converts the detected value into an image density based on the relationship with the image density, and controls process conditions based on the result.

  On the other hand, the color misregistration control pattern is formed at the center and near both ends of the intermediate transfer belt 150, and is detected by the regular reflection light of the reflective sensor 260. The toner pattern indicated by the yellow, black, cyan, and magenta line segments is formed in parallel and inclined with respect to the main scanning direction. With black as a reference color, the positional relationship of each color is the sub-scanning direction that is the transport direction between the patterns. In addition, the amount of color misregistration in both the main scanning direction (the direction indicated by the arrow B) is detected between the line segments arranged in parallel and inclined.

  The positional relationship can be detected by counting the passage timing of these patterns with a counter. CPU 400 controls the writing timing in writing unit 440 based on the color misregistration amount from the count value. The toner patterns of the respective colors formed on the intermediate transfer belt 150 are conveyed in the conveyance direction of the intermediate transfer belt 150 (the direction indicated by the arrow C) and are provided at three locations when passing just below the reflective sensor 260. The reflected sensor 260 sequentially detects each gradation and each shift toner pattern in parallel.

  FIG. 5 is a diagram showing an output waveform of regular reflection light when the toner pattern shown in FIG. The output voltage of the toner pattern decreases according to the gradation. When detecting the toner density, the amplitude value of this waveform is detected. In the color misregistration detection pattern, the reflectivity of black is deteriorated, so that the output voltage is lowered, and the color shows a substantially constant output voltage value. When color misregistration is detected, an intersection of the threshold and the falling of the output voltage and an intersection of the threshold and the rising of the output voltage are obtained on the basis of a predetermined threshold, and these are added and divided by 2, and the center Find the value. This central value is used as the time when each toner pattern is detected, and is used when obtaining the count value.

  FIG. 6 is a diagram showing an output waveform by regular reflection light when the toner pattern within one cycle of the toner pattern is detected by the reflection type sensor 260. One cycle of the toner pattern represents the period from when the output waveform value of the reference pattern is detected until the output waveform value of the last color used (here, magenta indicated by M20) is detected. The reference pattern may be provided separately from the toner pattern of each color. When the toner pattern is formed as shown in FIG. 4, one of the toner patterns detected in the cycle immediately before that cycle is used as a reference. It can also be used as a pattern. The reference pattern is not limited to one of the toner patterns detected in the immediately preceding cycle, and may be one of the toner patterns detected in the previous cycle.

  In FIG. 7, a large deviation occurs in the cyan toner pattern indicated by C20 in one cycle of the toner pattern shown in FIG. 6, and C20 is originally formed between K20 (black) and M20 (magenta). What should be shown is a diagram showing a case where it is formed between Y20 (yellow) and K20.

  When the color order of the toner pattern is reversed as shown in FIG. 7 due to some cause, the CPU 400 detects the color order unless the reflective sensor 260 can detect the color. I can't. For this reason, the reflective sensor 260 cannot correct the color misregistration, and depending on the control, C20 may be erroneously corrected to the normal position of K20, and K20 may be erroneously corrected to the normal position of C20. It had an adverse effect.

  Accordingly, control that does not adversely affect the output image even when the color order of the toner pattern is reversed will be described in detail below. In the embodiment shown in FIG. 7, C20 is displaced from the normal position. Here, the regular position is a correct position defined in advance.

  The configuration of the image forming apparatus that performs color misregistration correction and the color misregistration correction method of the present invention will be described in detail with reference to FIGS. FIG. 8 is a functional block diagram of an image forming apparatus that performs color misregistration correction. Although this image forming apparatus includes the hardware shown in FIGS. 1 to 3, in order to perform color misregistration correction, a detection unit 500, a measurement unit 510, a storage unit 520, a color order detection unit 530, a determination unit 540, A color order correction unit 550 and a color misregistration correction unit 560 are provided.

  The detection unit 500 detects the reference pattern and each color toner pattern in order. The detection unit 500 can be the reflective sensor 260 described above. The measurement unit 510 measures the time from the detection of the reference pattern to the detection of each color toner pattern as a counter value. The measuring unit 510 can be the counter described above.

  The storage unit 520 stores the counter values measured for all colors in order from the smallest. The storage unit 520 can be the RAM 420 described above.

  The color order detection unit 530 designates a certain color, and gives an instruction to the image forming unit 100 to sequentially form toner patterns of other colors excluding the color after the reference pattern. The image forming unit 100 forms those patterns, the detection unit 500 detects the patterns in order, and the measurement unit 510 measures the count value. The color order detection unit 530 determines the order of the counter values stored in the storage unit 520 to match or closest to the count value measured in this way, and detects the order of the specified color. To do. In this way, the color order detection unit 530 detects the color order of the toner patterns formed on the intermediate transfer belt 150 by the image forming unit 100.

  The determination unit 540 determines whether or not the detected color order is the same as the regular color order defined in advance. When the determination unit 540 determines that the color order is different, the color order correction unit 550 performs correction to change the order of the measured counter values based on the normal color order. Thereby, it becomes the same order as a regular color order.

  The color misregistration correction unit 560 has a target counter in the same order so that each color has a target counter value formed in a normal color order after the determination unit 540 determines that they are the same or after correction by the color order correction unit 550. The difference between the value and the measured counter value is calculated as a correction amount, and color misregistration correction is performed based on the correction amount. The target counter value is a predetermined target value.

  The color order detection unit 530, the determination unit 540, the color order correction unit 550, and the color misregistration correction unit 560 all function as these units when the CPU 400 reads and executes a program from the ROM 410 or the like.

  FIG. 9 is a flowchart showing an outline of the color misregistration correction process. First, the process is started from step 900. In step 905, a toner pattern is formed on the intermediate transfer belt 150, and a color misregistration correction process is started. As the toner pattern, a toner pattern as shown in FIGS. 4 and 5 is formed.

  Next, in step 910, the time from the detection of the reference pattern to the detection of the toner pattern of each color within one cycle of the toner pattern is measured, and the measured value is stored in the storage unit 520.

  FIG. 10 shows the detection of the toner pattern of each color from the detection of the reference pattern based on the output waveform by the regular reflection light when the toner pattern of each color in one cycle of the toner pattern is detected by the reflection type sensor 260 as the detection unit 500. It is a figure showing the count value until.

  The intersection between the falling edge of the output waveform of the reference pattern and the threshold value and the intersection of the rising edge of the output waveform and the threshold value are obtained, and the value obtained by adding them and dividing by 2 becomes the center value, and the center value of the reference pattern Counting is started, and the count value up to the central value obtained in the same manner for each color toner pattern is stored in the storage unit 520. The count value is a value counted by a counter that is the measurement unit 510. In FIG. 10, the count value from the reference pattern to Y20 is 100, and the count values from K20, C20, and M20 are 150, 140, and 220, respectively.

  Referring to FIG. 9 again, in step 915, a set of count values remaining when the nth toner pattern is deleted is stored in the storage unit 520 as a correspondence table in association with the order n. A correspondence table is created for all colors used and stored in the storage unit 520.

  Specifically, the count value from the reference pattern to the toner pattern of each color in one cycle of the toner pattern when one color from the first color to the fourth color is deleted is acquired from the storage unit 520 and corresponds to the order. In addition, it is stored in the storage unit 520 as a correspondence table. When the first Y20 toner pattern is deleted, there is no first count value 100. Therefore, as the count values, values of C20 140, K20 150, and M20 220 are obtained. It is stored in association with the order of No. 4.

  When the second C20 toner pattern is deleted, since there is no second count value 140, the values of 100 for Y20, 150 for K20, and 220 for M20 are acquired. It is stored in association with the order of No. 4.

  When the third K20 toner pattern is deleted, since there is no third count value 150, Y20 100, C20 140, and M20 220 are obtained. It is stored in association with the order of No. 4.

  When the fourth M20 toner pattern is deleted, since there is no fourth count value 220, Y20 100, C20 140, and K20 150 are acquired, and the first, second, The number 3 is stored in association with the order.

  The counter values stored in the storage unit 520 can be stored as a correspondence table as shown in FIG.

  Referring again to FIG. 9, in step 920, the color order detection unit 530 instructs the image forming unit 100, and the image forming unit 100 displays the toner patterns of each color other than the use color m on the intermediate transfer belt 150. To form. The used color m here is a color designated by the color order detection unit 530. Next, in step 925, the measurement unit 510 measures the count value from the reference pattern to each toner pattern within one toner pattern cycle. Next, in step 930, the color order detection unit 530 determines whether the count value is the same as the count value corresponding to the deleted color. This is performed until the count values match or the closest count value is detected.

  In step 935, the color order detection unit 530 determines whether the order has been detected for all colors. If the order detection has not been completed for all colors, the process returns to step 920. The process proceeds to step 940.

  The processing from step 920 to step 935 will be described in detail with reference to FIG. Since the regular color order is the order of yellow, black, cyan, and magenta, it is preferable to judge in that order. FIG. 12 is a diagram showing an output waveform and a count value by regular reflection light when the detection unit 500 detects the toner pattern when the yellow toner pattern is deleted.

  The color order detection unit 530 compares the count value counted by the measurement unit 510 with the count value stored in the storage unit 520, searches for a value that matches or is closest, and deletes the deleted yellow It is determined what number the toner pattern is located from the side closer to the reference pattern. In the embodiment shown in FIG. 12, the measurement unit 510 counts each toner pattern to obtain values 140, 150, and 220, respectively. The color order detection unit 530 compares these values with the counter values stored in the storage unit 520, detects that the values are the same as the second, third, and fourth values. It is determined that it is the first other than that.

  FIG. 13 is a diagram illustrating an output waveform and a counter value by specularly reflected light when the detection unit 500 detects a toner pattern when the black toner pattern set next to yellow is deleted.

  Similarly to the above, the color order detection unit 530 compares the count value counted by the measurement unit 510 with the count value stored in the storage unit 520, and searches for a value that matches or is closest. Then, it is determined what position the deleted black toner pattern is positioned from the side closer to the reference pattern. In the embodiment illustrated in FIG. 13, the measurement unit 510 counts each toner pattern to obtain values of 100, 140, and 220, respectively. The color order detection unit 530 compares these values with the counter values stored in the storage unit 520, detects that the values are the same as the first, second, and fourth values. It is judged that it is the third other than that.

  FIG. 14 is a diagram showing an output waveform and a counter value by specular reflection light when the detection unit 500 detects a toner pattern when the cyan toner pattern set next to black is deleted.

  Similarly, the color order detection unit 530 compares the count value counted by the measurement unit 510 with the count value stored in the storage unit 520, and searches for a value that matches or is closest. Then, it is determined what position the deleted cyan toner pattern is positioned from the side closer to the reference pattern. In the embodiment shown in FIG. 14, the measurement unit 510 counts each toner pattern to obtain values of 100, 150, and 220, respectively. The color order detection unit 530 compares these values with the counter values stored in the storage unit 520, detects that the values are the same as the first, third, and fourth values. It is determined that it is the second other than that.

  FIG. 15 is a diagram showing an output waveform and a counter value by specularly reflected light when the detection unit 500 detects a toner pattern when the magenta toner pattern set next to cyan is deleted.

  Similarly, the color order detection unit 530 compares the count value counted by the measurement unit 510 with the count value stored in the storage unit 520, and searches for a value that matches or is closest. Then, it is determined what position the deleted magenta toner pattern is positioned from the side closer to the reference pattern. In the embodiment shown in FIG. 15, the measurement unit 510 counts each toner pattern to obtain values of 100, 140, and 150, respectively. The color order detection unit 530 compares these values with the counter values stored in the storage unit 520, detects that the values are the same as the first, second, and third values. It is judged that it is the 4th other than that.

  Referring to FIG. 9 again, when these processes are completed, in step 940, determination unit 540 determines whether all the color orders are the same as the regular color order in which the toner is set. If the color order is the same as the normal color order, the process proceeds to step 945 to perform color misregistration correction. On the other hand, if the color order is different from the normal color order, the process proceeds to step 950, where color order correction is first performed, and then color misregistration correction is performed. When these correction processes are completed, the process ends in step 955.

  In the embodiment shown in FIGS. 12 to 15, the cyan and black toner patterns formed on the intermediate transfer belt 150 are formed in reverse, and it is detected in the above determination that they are not the same as the normal color order. . For this reason, the process proceeds to step 950 and color order correction is performed.

  In the color order correction, based on the detected color order, here the color order of yellow, cyan, black, magenta, and the counter value from the reference pattern to the toner pattern of each color, here the values 100, 140, 150, 220. After calculating the correction amount when performing the color misregistration correction process, the correction amount is fed back, and the correction amount is used for the color misregistration correction processing when the image forming unit 100 forms the color misalignment corrected image or the like. .

  Specifically, since the normal color order is yellow, black, cyan, and magenta, the counter values are changed in the order of 100, 150, 140, and 220. When the target count value of each color in the normal color order is set to 100, 150, 200, 250, the counter values for the first yellow and the second black are the same at 100, 150. The correction amount is set to zero. For the third cyan, the counter value must be 200, but since the actually counted value is 140, it is necessary to move about +60. Therefore, the correction amount is +60. For the fourth magenta, the counter value must be 250, but since the actually counted value is 220, it is necessary to move about +30. Therefore, the correction amount is +30. These correction amounts 0, 0, +60, and +30 are fed back and used for color misregistration correction processing.

  A toner pattern of each color other than the toner pattern of the used color m is formed, a counter value of the toner pattern of each color other than the toner pattern of the used color m is measured, and compared with the counter value stored in the storage unit 520 In this case, the measured counter value does not necessarily match any of the counter values stored in the storage unit 520. In this case, the counter value stored in the storage unit 520 closest to the measured counter value is detected. The process will be described below.

  FIG. 16 is a diagram illustrating counter values measured when the yellow toner pattern is deleted and counter values stored in the storage unit 520. The absolute value of the difference from the count value when each of the toner patterns stored in the storage unit 520 is deleted in order to detect the order from which the yellow toner pattern is formed closer to the reference pattern. Are added, and the smallest counter value is determined as the closest counter value.

  More specifically, FIG. 16B shows the counter values obtained when the storage unit 520 stores the table shown in FIG. 16A and the yellow toner pattern is deleted. Suppose it was a value. As shown in FIG. 16B, when the detected counter value is 138, 146, 223, it is assumed that the deleted toner pattern is the first, second, third, or fourth. Calculate as shown in ~ 4.

  As a result of the calculation as described above, since the total value calculated by Expression 1 is the smallest, it can be determined that the erased toner pattern is the first toner pattern. Here, the calculation example for obtaining the counter value stored in the storage unit 520 closest to the measured counter value is shown. However, this calculation example is an example, and if the closest counter value can be obtained, other calculation values can be obtained. Any calculation formula can be used.

  Although the present invention has been described with the embodiments, the present invention is not limited to the above-described embodiments, and other embodiments, additions, changes, deletions, and the like may occur to those skilled in the art. It can be changed within the range that can be done, and any embodiment is included in the scope of the present invention as long as the effects of the present invention are exhibited. Therefore, the present invention can be provided as an image forming apparatus and a color misregistration correction method executed by the image forming apparatus, as well as a computer-readable program for realizing the method. The program can be provided by being stored in a recording medium such as an FD, MD, SD card, CD-ROM, or DVD-ROM.

FIG. 2 is a diagram illustrating a hardware configuration of an image forming unit that configures the image forming apparatus according to the embodiment. The figure which showed an example of the structure of a reflection type sensor. FIG. 3 is a diagram illustrating a hardware configuration of a control unit that configures the image forming apparatus according to the embodiment. FIG. 4 is a diagram illustrating an example of a toner pattern formed on an intermediate transfer belt and a positional relationship between the toner pattern and a reflective sensor. FIG. 5 is a diagram showing an output waveform by regular reflection light when the toner pattern shown in FIG. 4 is detected by a reflection type sensor. The figure showing the output waveform by regular reflection light at the time of detecting the toner pattern in 1 cycle of toner patterns with a reflective sensor. The figure which showed the place which the color order of the toner pattern reversed. 1 is a functional block diagram of an image forming apparatus that performs color misregistration correction. The flowchart figure which shows the outline of a color shift correction process. FIG. 6 is a diagram illustrating count values from a reference pattern to a toner pattern of each color based on an output waveform of regular reflection light when a toner pattern of each color in one cycle of toner pattern is detected by a reflective sensor. The figure which illustrated the correspondence table. FIG. 10 is a diagram illustrating an output waveform and a count value by regular reflection light when a toner pattern is detected by a detection unit when a yellow toner pattern is deleted. The figure showing the output waveform and count value by regular reflection light when a toner pattern when a black toner pattern is deleted is detected by a detection unit. FIG. 6 is a diagram illustrating an output waveform and a count value by regular reflection light when a toner pattern is detected by a detection unit when a cyan toner pattern is deleted. FIG. 6 is a diagram showing an output waveform and a count value by regular reflection light when a detection unit detects a toner pattern when a magenta toner pattern is deleted. The figure which illustrated the counter value measured when the yellow toner pattern was deleted, and the counter value memorize | stored in the memory | storage part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Image forming part 110 ... Photoconductor drum 120 ... Charging unit 130 ... Exposure device 140 ... Development unit 150 ... Intermediate transfer belt 160 ... Primary transfer roller 170 ... Cleaning unit 180 ... Drive roller 190 ...... Subordinate roller, 200 ... paper, 210 ... fixing unit, 220 ... feed tray, 230 ... feed roller, 240 ... secondary transfer roller, 250 ... cleaning unit, 260 ... reflection sensor, 270 ... light emitting element, 280a, 280b ... light receiving element, 290 ... holder, 300 ... image carrier, 310 ... toner pattern, 400 ... CPU, 410 ... ROM, 420 ... RAM, 430 ... I / F unit, 440 ... writing unit, 450 ... I / O Unit, 460 ... counter, 500 ... detection unit, 510 ... measurement unit, 520 ... storage unit, 530 ... color order detection unit, 40 ... determining unit, 550 ... color order correction unit, 560 ... color shift correction unit

Claims (10)

An image forming unit that forms an image, a reference pattern, and a toner pattern of each color; a detection unit that sequentially detects the reference pattern and the toner pattern of each color; and a time from the detected reference pattern to the toner pattern of each color or An image forming apparatus including a measurement unit that measures a distance and performing color misregistration correction,
A storage unit for storing measurement values measured for all colors in order from the smallest;
An instruction for designating one color and sequentially forming a toner pattern of each of the other colors excluding the color following the reference pattern is given to the image forming unit, and the measurement for each of the other colors measured by the measuring unit The color order of the toner pattern to be formed is detected by determining in which order the measured value stored in the storage unit matches or closest to the value, and detecting the specified color order. A color order detection unit;
A determination unit that determines whether or not the detected color order is the same as a regular color order defined in advance;
When it is determined that the determination unit is different, a color order correction unit that performs correction to change the order of the measured values based on the regular color order;
The target in the same order so that each measured value formed in the regular color order and measured for each color becomes each target value when it is determined by the determination unit to be the same or after correction by the color order correction unit An image forming apparatus including a color misregistration correction unit that calculates a difference between the measured value and the measured value as a correction amount, and performs color misregistration correction based on the correction amount.   The storage unit further stores a set of measurement values remaining when the n-th (n is a natural number) measurement value is deleted as a correspondence table in association with the n, and the color order detection unit includes the other The image forming apparatus according to claim 1, wherein the order of the designated color is detected based on the measured value for each color and the correspondence table.   The color order detection unit obtains a total value by adding an absolute value of a difference between the measurement value for each of the other colors and each of the set of measurement values corresponding to each order of the correspondence table, The image forming apparatus according to claim 2, wherein the order that is the smallest by comparing the total values obtained for each order is detected as an order in the color order of the formed toner pattern.   The color order detection unit designates the one color, gives an instruction to sequentially form toner patterns of other colors excluding the color following the reference pattern, and measured values for the other colors are The image according to claim 1, wherein it is determined for each color that the order of measurement values stored in the storage unit matches or is the closest and the order of the specified color is detected. Forming equipment. An image forming unit that forms an image, a reference pattern, and a toner pattern of each color; a detection unit that sequentially detects the reference pattern and the toner pattern of each color; and a time from the detected reference pattern to the toner pattern of each color or A color misregistration correction method executed by an image forming apparatus including a measurement unit that measures a distance,
Storing the measured values for all colors measured by the measuring unit in the storage unit in order of increasing order; and
Designating one color and sequentially forming a toner pattern of each of the other colors excluding the color following the reference pattern;
The order of the specified color is detected by determining which order of measurement values stored in the storage unit the measurement values for the other colors measured by the measurement unit match or closest to each other. Detecting the color order of the toner pattern to be formed;
Determining whether the detected color order is the same as a regular color order defined in advance;
If it is determined that the step is different, the step of changing the order of the measured values based on the regular color order; and
When it is determined that the same in the determining step or after the replacing step, the target values in the same order are set so that each measured value formed in the regular color order and measured for each color becomes each target value. Calculating a difference from the measured value as a correction amount, and performing color misregistration correction based on the correction amount.   The method further includes a step of storing a set of measurement values remaining when the n-th (n is a natural number) -th measurement value is associated with the n as a correspondence table, and in the detecting step, each of the other colors is stored. The color misregistration correction method according to claim 5, wherein the order of the designated colors is detected based on a measurement value and the correspondence table.   In the detecting step, the absolute value of the difference between the measurement value for each of the other colors and each of the one set of measurement values corresponding to each order of the correspondence table is added to obtain a total value, The color misregistration correction method according to claim 6, wherein an order that minimizes the total value obtained for each order is detected as an order in the color order of the formed toner pattern.   The color misregistration correction method according to claim 5, wherein the forming step and the detecting step are executed for all colors.   A computer-readable program for executing the color misregistration correction method according to any one of claims 5 to 8.   A recording medium on which the computer-readable program according to claim 9 is recorded.

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