JP2019066678A - Image formation apparatus and image formation method - Google Patents

Abstract

To solve a problem in which the color matching control cannot be performed since detection patterns cannot be properly detected when the detection patterns overlap each other due to the color shift.SOLUTION: An image formation apparatus includes: a plurality of image formation parts which form toner images having the mutually-different colors; and a second image carrier to which the images in respective colors formed by the image formation parts are transferred in an overlapping manner with alignment, and performs image formation by transferring the transfer images of the second image carrier to a recording medium. The image formation apparatus includes: pattern formation means which forms patterns formed by a plurality of first image carriers and transferred to the second image carrier; pattern detection means which detects the patterns transferred to the second image carrier; pattern overlapping determination means which determines the overlapping of the plurality of patterns from the edges of the detected patterns that include the plurality of patterns with respect to the first image carrier; and pattern cycle change means which changes the pattern cycle of each color when there is the overlapping of the patterns.SELECTED DRAWING: Figure 9

Description

  The present invention relates to an image forming apparatus and an image forming method.

  Conventionally, an electrophotographic color image forming apparatus has a plurality of image forming units, and images of respective colors formed by the respective image forming units are sequentially superimposed on a transfer belt, and an image in a state in which each color is superimposed on the transfer belt Is transferred to a recording medium such as paper.

  As a problem of this method, there is a so-called color shift which is mutually shifted when the images of the respective colors are superimposed on the transfer belt due to the mechanical precision of a plurality of image forming units. As a technique for correcting this color shift, an image pattern of each color is formed on the transfer belt for color shift detection, a plurality of images are read by a sensor, and the amount of position shift between each color image is calculated from the read information. There are known color matching control techniques for correcting various settings of image formation.

  For example, Patent Document 1 discloses a configuration in which, in an apparatus for forming a plurality of misregistration detection patterns, an interval between detection patterns is gradually narrowed in order to shorten a color matching control execution time.

  However, in the configuration described in Patent Document 1, when the detection patterns overlap due to color shift, the detection pattern can not be appropriately detected, and color matching control can not be performed.

  In order to solve the above-mentioned problems, the invention according to claim 1 has a first image carrier surface, and develops latent images formed on the surface of the first image carrier with toners of different colors. A plurality of image forming units for forming an image of each color and an image of each of the colors formed on each of the plurality of first image carriers in the image forming unit driven at a predetermined speed are aligned. An image forming apparatus for forming an image by transferring an image of each color superimposed and transferred onto the second image carrier onto a recording medium; A pattern forming unit for forming a pattern formed by the plurality of first image carriers and transferred to the second image carrier, and detecting the pattern transferred to the second image carrier Pattern detecting means, and the pattern The image carrier includes a plurality of patterns, and the pattern overlap determination unit determines the overlap of the plurality of patterns from the edge of the pattern detected by the pattern detection unit, and the pattern overlap determination unit overlaps the patterns. And an image forming apparatus including pattern period changing means for changing the pattern period of each color.

  According to the present invention, color matching control can be performed even when pattern duplication of each color occurs.

FIG. 2 is a block diagram of an image forming unit of the image forming apparatus. It is a block diagram of a detection sensor. FIG. 2 is a hardware configuration diagram of an image forming apparatus. FIG. 2 is a functional block diagram of the image forming apparatus. It is an example of the pattern formed on the belt. It is an explanatory view of control based on a detection result of a detection sensor. It is a first explanatory example of the color shift correction amount calculated from the pattern detection result. It is a second explanatory example of the color misregistration correction amount calculated from the pattern detection result. It is a first example of the color misregistration correction flow. It is a second example of the color misregistration correction flow. It is a third example of the color misregistration correction flow.

  Hereinafter, an embodiment of the present invention will be described based on the attached drawings. In each of the drawings for describing the embodiments of the present invention, components such as members having the same function or shape and components such as components are described once by attaching the same reference numerals as much as possible. So I will omit the explanation.

  FIG. 1 is a view for explaining the arrangement of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 100 is an apparatus including, for example, a facsimile apparatus, a printing apparatus (printer), a copying machine, and a multifunction peripheral.

  The image forming apparatus 100 includes an image forming unit 102 including an optical device 101 described later, a photoreceptor, a charging device, a developing device, and the like, and a transfer unit 103 including an intermediate transfer belt and the like. The photosensitive member is in the form of a drum, for example, and may be referred to as a photosensitive drum.

  The optical device 101 deflects a light beam BM emitted from a laser light source having an LD (Laser Diode), which will be described later as an example, by the polygon mirror 110, and makes the light incident on scanning lenses 111a and 111b including an fθ lens.

  The light beams are generated in numbers corresponding to the respective color images of yellow (Y), black (K), magenta (M), and cyan (C), and reflected by the scanning lenses 111a and 111b, respectively. The light is reflected by the mirrors 112y to 112c.

  For example, the yellow light beam Y passes through the scanning lens 111a, is reflected by the reflection mirror 112y, and is incident on the WTL lens 113y. The same is true for the light beams K, M, and C of the respective colors of black, magenta, and cyan, so the description thereof will be omitted.

  The WTL lenses 113 y to 113 c shape the respective light beams Y to C incident thereon, and then deflect the respective light beams Y to C to the reflection mirrors 114 y to 114 c. Then, the respective light beams Y to C are further reflected by the reflection mirrors 115 y to 115 c, and are irradiated onto the photosensitive drums 120 y to 120 c as the light beams Y to C used for exposure, respectively.

  In the irradiation of the light beams Y to C to the photosensitive members 120y to 120c as the first image carrier, timing synchronization is performed with respect to the main scanning direction and the sub scanning direction with respect to the photosensitive members 120y to 120c.

  Hereinafter, the main scanning direction with respect to the photosensitive members 120y to 120c is defined as the scanning direction of the light beam, and the sub scanning direction is defined as a direction orthogonal to the main scanning direction, that is, the rotating direction of the photosensitive members 120y to 120c. Do.

  The photosensitive members 120y to 120c each include a photoconductive layer including at least a charge generation layer and a charge transport layer on a conductive drum such as aluminum.

  The photoconductive layers are disposed corresponding to the photosensitive members 120y to 120c, respectively, and are charged with surface charges by chargers 122y to 122c including a corotron, a scorotron, or a charging roller.

  The electrostatic charges provided on the photosensitive members 120y to 120c by the respective chargers 122y to 122c are imagewise exposed by the light beams Y to C, and electrostatic latent images are formed on the surfaces to be scanned of the respective chargers 122y to 122c. Is formed.

  The electrostatic latent images respectively formed on the scan surfaces of the photosensitive members 120y to 120c are developed by the developing devices 121y to 121c including a developing sleeve, a developer supply roller, a regulation blade, etc., and the photosensitive members 120y to 120c are formed. A developer image is formed on the surface to be scanned.

  The developers carried on the surfaces to be scanned of the photosensitive members 120y to 120c are transferred onto the intermediate transfer belt 130 moving in the direction of the arrow D by the conveyance rollers 131a to 131c. 132y to 132c are primary transfer rollers for the photosensitive members 120y to 120c, respectively.

  The intermediate transfer belt 130 is conveyed to the secondary transfer position F in a state where the Y, K, M, and C developers transferred from the surfaces to be scanned of the photosensitive members 120 y to 120 c are carried. That is, the intermediate transfer belt 130 corresponds to an intermediate transfer member.

  The secondary transfer belt 133 is stretched over the conveyance rollers 134a and 134b, and is further conveyed in the direction of arrow E by the rotation of the conveyance rollers 134a and 134b.

  At the secondary transfer position F, the sheet P, which is an image receiving material such as high quality paper and a plastic sheet, is supplied from the sheet storage unit T such as a sheet feeding cassette by the conveyance roller 135. At the secondary transfer position F, a secondary transfer bias is applied to transfer the multicolor developer image carried on the intermediate transfer belt 130 onto the paper P held by suction on the secondary transfer belt 133.

  The sheet P is supplied to the fixing device 136 along with the conveyance of the secondary transfer belt 133.

  The fixing device 136 includes a fixing member 137 such as a fixing roller containing silicone rubber, fluorine rubber, etc., and pressurizes the sheet P and the multicolor developer image, and the sheet discharge roller 138 P is discharged to the outside of the image forming apparatus 100 as a printed matter P ′.

  The intermediate transfer belt 130 after transferring the multicolor developer image is supplied to the next image forming process after the transfer residual developer is removed by the cleaning unit 139 including a cleaning blade.

  In addition, three detection sensors 5a to 5c for detecting pattern images for correcting various image forming conditions when forming a color image formed on the intermediate transfer belt 130 in the vicinity of the conveyance roller 131a. Is provided.

  Each of the detection sensors 5a to 5c may be a reflection type detection sensor including a known reflection type photo sensor, and based on the detection result by each of the detection sensors 5a to 5c, the skew (tilt) of each color with respect to the reference color The main scanning registration deviation amount, the sub scanning registration deviation amount, and the main scanning magnification error are calculated, and various deviation amounts relating to image quality adjustment are corrected based on the calculation results. The image forming conditions (misregistration correction, density correction) at the time of forming a color image are corrected, and various processes related to generation of a test pattern image at the time of image adjustment are executed.

  FIG. 2 is a view for explaining the schematic configuration of the inside of each of the detection sensors 5a to 5c shown in FIG. The internal configuration of each of the detection sensors 5a to 5c is common, and the detection sensor 5a is illustrated in FIG. 2. However, since the detection sensors 5b and 5c are the same, the description thereof is omitted. In addition, if it is not necessary to distinguish between 5a, 5b, 5c and their internal configurations, the subscripts of rich people may be omitted and described.

  The detection sensor 5a includes one light emitting unit 10a, two light receiving units 11a and 12a, and a condensing lens 13a. The light emitting unit 10 a is a light emitting element that emits light, and is, for example, an infrared light LED that generates infrared light. The light receiving unit 11a is, for example, a regular reflection type light receiving element, and the light receiving unit 12a is, for example, a diffuse reflection type light receiving element.

  The detection sensor 5a reaches the test pattern of the intermediate transfer belt 130 after the light L1 emitted from the light emitting unit 10a passes through the condenser lens 13a. Then, a part of the light is specularly reflected by the test pattern formation area or the toner layer in the test pattern formation area to become the specular reflection light L2, and the light is retransmitted through the condenser lens 13a and received by the light receiving unit 11a. Ru.

  The other part of the light is diffused and reflected by the test pattern forming area and the toner layer in the test pattern forming area to become diffuse reflected light L3 and then retransmitted through the condensing lens 13a and received by the light receiving portion 12a. Be done.

  A laser light emitting element or the like may be used as the light emitting element instead of the infrared light LED. Further, although phototransistors are used as the light receiving portions 11a and 12a (regular reflection type light receiving elements and diffuse reflection type light receiving elements), those made of photodiodes, amplification circuits, etc. may be used.

  Next, the hardware configuration of the image forming apparatus 100 will be described with reference to FIG. As shown in FIG. 3, the image forming apparatus 100 operates a central processing unit (CPU) 1, a read only memory (ROM) 2, a random access memory (RAM) 3, and a hard disc drive (HDD) 4. A panel 6, an external communication I / F 7, a sensor control unit 14, a write control unit 8, and a print controller 16 are provided. These are mutually connected by a system bus 9.

  The ROM 2 is a non-volatile semiconductor memory that can hold data even when the power is turned off. The RAM 3 is a volatile semiconductor memory that temporarily stores programs and data.

  The HDD 4 is a non-volatile memory storing programs and data. The programs and data stored in the HDD 4 include an OS (Operating System) which is basic software for controlling the entire image forming apparatus 1 and various application programs operating on the OS.

  The CPU 1 is an arithmetic device that reads programs and data from the HDD 4 and the ROM 3 onto the RAM 3 described later and executes various processes.

  The operation panel 6 is an input / output device including a touch panel for the user to input an operation and a display for displaying various processing results.

  The external communication I / F 7 is an interface for connecting the image forming apparatus 100 to a network such as a LAN (Local Area Network). The image forming apparatus 100 can receive a print (image formation) command, image data, and the like from the user terminal device via the external communication I / F 7.

  The sensor control unit 14 is further connected to the light emitting unit 10 and the light receiving units 11 and 12. The light emitting unit 10 and the light receiving units 11 and 12 of the detection sensor 5 are controlled.

  The write control unit 8 is further connected to the LD 116. The write control unit 8 includes a device capable of setting the output frequency very finely, such as a clock generator using a VCO (Voltage Controlled Oscillator), and this output is used as an image clock. The write control unit 8 is driven according to the image data sent from the print controller 16 based on the pixel clock to drive the LD 116, and a latent image is written on the charged photosensitive member surface.

  The image forming apparatus 100 further has an external interface, and reads and writes recording media such as a CD (Compact Disc), a DVD, an SD (Secure Digital) memory card, and a USB (Universal Serial Bus) memory via the external interface. May be performed.

  FIG. 4 is a functional block diagram of the image reading apparatus 100. As shown in FIG.

  Image forming apparatus 100 includes an input receiving unit 160, a control unit 170, a communication control unit 180, a read / write processing unit 190, and a storage unit 200.

  The input receiving unit 160 is realized by the processing of the operation panel 6, displays the operation status and setting information of the image forming apparatus 100 to the operator, and executes a function of receiving an operation on the image forming apparatus 100 by the operator.

  The control unit 170 is realized by the CPU 1 executing a program stored in the ROM 2 or the HDD 4 with the RAM 3 as a work area, and executes control of the entire image forming apparatus 100.

  The communication control unit 180 is realized by the CPU 1 executing a program stored in the ROM 2 or the hHDD 4 with the RAM 3 as a work area to control the external communication I / F 7, and a communication function or print job from the image forming apparatus to the outside Execute the reception function of

  The read / write processing unit 190 is realized by the CPU 1 executing the ROM 2 or the HDD 4 with the RAM 3 as a work area, and executes functions of storing various data in the storage unit 200 and reading out various stored data. Do.

  The storage unit 200 is executed by the processing of the ROM 2 or the HDD 4 and executes a function of storing a program, document data, various setting information necessary for the operation of the image forming apparatus 100, an operation log of the image forming apparatus 100, and the like. It may be executed by the process of the RAM 3.

  FIG. 5 is a conceptual view in which an image 140 to be transferred onto a sheet of paper P and a pattern image for correcting the image forming conditions are formed in parallel on both sides of the intermediate transfer belt 130. The pattern image of FIG. 5 is a misalignment detection pattern which is a pattern image particularly for detecting misalignment. In the following description, the misalignment detection pattern may be referred to as a "pattern".

  As shown in FIG. 5, the detection sensors 5a and 5c are disposed at positions detecting both ends in the main scanning direction of the intermediate transfer belt 130, and the detection sensor 5b is disposed at a position detecting a central portion. Since the image 140 is present in the row detected by the detection sensor 5b, no pattern is formed, and a pattern is formed in the row detected by the detection sensors 5a and 5c at the end.

  If color misregistration correction is performed at a timing when printing is not performed, that is, when an image to be transferred onto the sheet P is not printed, the color misregistration correction may be performed by forming a pattern also in the column corresponding to 5b.

  The intermediate transfer belt 130 advances in the direction of the arrow in FIG. After the intermediate transfer belt 130 passes the detection position by the detection sensors 5a, 5b and 5c, the image 140 is transferred from the intermediate transfer belt 130 to the sheet P. The pattern is conveyed to the position of the cleaning member 139 without being transferred to the sheet P and is cleaned.

  The direction of the arrows hereinafter is the sub-scanning direction described in FIG. Therefore, the main scanning direction is a direction orthogonal to the arrow in FIG.

  The misalignment detection pattern set 30 (hereinafter sometimes referred to as a pattern set) consists of eight patterns. In the eight patterns, yellow, black, magenta, and cyan color patterns are repeated twice from the top of FIG. The first four patterns are patterns (hereinafter, may be referred to as horizontal line patterns) long in the main scanning direction different in color. The next four patterns are patterns that are diagonally long with respect to the horizontal line pattern (hereinafter may be referred to as a diagonal line pattern).

  The color misregistration correction is performed using one or more of the pattern sets 30. Since the characteristics of the color misregistration change according to the characteristics of each image forming apparatus, the number of sets to be corrected when using a plurality of images is preset according to the configuration of the image forming apparatus and the required image quality. The number of sets used is sometimes called the number of pattern groups. Also, the n-th pattern set 30 of the pattern groups is hereinafter referred to as the n-th set.

  Control using the detection result of the detection sensor 5 will be described with reference to FIG.

  The signal obtained from the light receiving unit 11 is amplified by the amplifier 142, and only the signal component for line detection is passed by the filter 143, and analog data is converted to digital data by an A / D (Analogue / Digital) conversion unit 144. Ru. The sampling of data is controlled by the sampling control unit 145, and the sampled data is stored in a FIFO (First IN First Out) memory 146. After the detection of one set of detection marks is completed, the stored data is loaded to the CPU 1 and the RAM 3 by the data bus 9 through the I / O (Input / Output) port 15, and the CPU 1 Arithmetic processing is performed to obtain the various amounts of deviation described above.

  Then, the CPU 1 sets the writing start timing, the change of the pixel clock frequency, and the like to the writing control unit 8 based on the calculated correction amount. Further, the CPU 1 monitors the detection signal from the light receiving unit 11 at an appropriate timing, and emits light by the light emission amount control unit 141 so that even if the conveyance belt and the light emitting unit 10 are deteriorated, etc. The amount is controlled so that the level of the light reception signal from the light receiving unit 11 is always constant.

  The ROM 2 stores various programs for controlling the misregistration correction apparatus and the image forming apparatus, as well as programs for calculating the various misregistration amounts described above. As described above, when the CPU 1 executes the program of the ROM 2 with the RAM 3 as a work area, the CPU 1 functions as a control unit 170 that controls the overall operation of the image forming apparatus 100 including color matching control described below.

  A specific calculation method of various misalignment amounts when the misalignment detection pattern is detected will be described with reference to FIG. An alternate long and short dash line 31a in FIG. 7 is a line indicating the sub scanning direction, and a range 5a indicated by a circle indicates a detection range on the intermediate transfer belt 130 of the detection sensor 5a.

  Here, the case where the line of the misalignment detection pattern is detected by the detection sensor 5a will be described, but the same applies to the other detection sensors 5b and 5c.

  The detection sensor 5a detects a row of misalignment detection patterns, which is a row along 31a, at a predetermined constant sampling time interval, and notifies the CPU 1 of the same.

  When receiving notification of detection from detection sensor 5a one after another, CPU 1 between each horizontal line pattern, between each horizontal line pattern and each corresponding diagonal line pattern based on the interval of each detection notification and the sampling time interval. Calculate the distance.

  In this manner, the lengths between the horizontal line patterns of the same color and between the horizontal line patterns and the corresponding diagonal line patterns are determined, and the calculated lengths are compared to obtain various positional deviation amounts. It can be calculated.

  Here, the calculation of the main scanning registration deviation amount and the sub-scanning registration deviation amount will be described as an example on the basis of the K color pattern.

  The calculation of the sub-scanning registration deviation amount (position deviation amount in the sub-scanning direction) will be described. First, using a horizontal line pattern, a pattern of K which is a reference color and each pattern of Y, M and C of the target color The interval value (y1, m1, c1) is calculated and compared with the ideal interval value (y0, m0, c0) stored in advance. And the interval value y1-the ideal interval value y0, the interval value m1-the ideal interval value m0, the interval value c1-the ideal interval value c0 from the ideal interval value c0 for each color of Y, M, C with respect to the reference color (K) It can be calculated.

  Next, in the calculation of the main scanning registration deviation amount (position deviation amount in the main scanning direction), first, the interval value (y2, k2, m2, c2) between the horizontal line pattern of each of the colors K to C and the oblique line pattern is calculated. Do. The difference value between the reference color (K) interval value and the non-reference color interval value is calculated using the calculated interval value. The difference value corresponds to the amount of positional deviation in the main scanning direction.

  This is because the oblique line pattern is inclined at a predetermined angle (for example, 45 °) with respect to the main scanning direction, so if there is a deviation in the main scanning direction, the distance from the horizontal line pattern is different for other colors. It is to spread or narrow more than the interval.

  That is, the amounts of positional deviation in the main scanning direction of black and yellow, black and magenta, and black and cyan are determined by the interval value k2-interval value y2, interval value k2-interval value m2, and interval value k2-interval value c2. In this manner, registration deviation amounts in the sub-scanning direction and the main scanning direction can be obtained.

  Further, the skew and the main scanning magnification error can also be determined based on the detection results of different ones of the detection sensors 5a to 5c. The skew component can be calculated by calculating the difference between the sub-scanning registration deviation amounts detected by the detection sensors 5a and 5c.

  Then, based on the various positional deviation amounts acquired as described above, correction processing is performed to correct the image forming conditions when forming a color image on the intermediate transfer belt 130.

  As the correction process, for example, by adjusting the light emission timing of the light beams Y to C corresponding to the respective colors to the photosensitive members 120 y to 120 c so that the positional deviation amounts substantially match, the resist in the main scanning direction and the sub scanning direction Perform resist adjustment and main scan overall magnification adjustment. With regard to the resist adjustment in the sub scanning direction, the positional deviation amount with respect to the photosensitive member 120 k is corrected by finely adjusting the speeds of the photosensitive members 120 y to 120 c.

  The correction of the positional deviation amount is not limited to this, and it is also possible to perform the adjustment by using the inclination of the reflection mirror described in FIG. 1 as an example using a stepping motor. Further, correction can be made by changing the image data, such as adding a white line to the image data.

  FIG. 8 shows displacement detection patterns according to the present invention and output signals from the detection sensor. Here, although the case where the horizontal line pattern of the misalignment detection pattern is detected by the detection sensor 5a will be described, the same processing is performed for the case where the other detection sensors 5b and 5c and the diagonal line pattern are detected.

  As shown in FIG. 8A, the falling edge period of the horizontal line pattern of the same color of the nth set and the n + 1th set (or the n-1th set) of the pattern group is fixed by the write control unit 8. These values are y3, k3, m3 and c3, respectively. While there is no pattern overlap, color matching control is performed in the pattern cycle of y3, k3, m3 and c3 as an ideal state.

  Next, the case where the pattern period is changed will be described with reference to FIG. In the (n + 1) -th group, patterns are drawn with periods (y4, k4, m4, c4) different for each color. Here, the pattern period (y4, k4, m4, c4) can be expressed by the following equations 1 to 4 as Δy, Δm, Δc, and Δk, which are different amounts of increase in period intervals, respectively.

y4 = y3 + Δy (Equation 1)
m4 = m3 + Δm (Equation 2)
c4 = c3 + Δc (Equation 3)
k4 = k3 + Δk (Equation 4)

  At this time, the ideal interval value (y5, m5, c5) of the horizontal line pattern interval used for the calculation of the sub scanning registration deviation amount can be expressed by the following equations 5 to 7, respectively.

y5 = y0 + Δk−Δy (Equation 5)
m5 = m0 + Δm-Δk (Equation 6)
c5 = c0 + Δc−Δk (Equation 7)

  The main scanning registration deviation amount calculation is the same as before changing the pattern period. As described above, by changing the pattern period, it is possible to change the pattern interval and calculate the correction value of the misalignment detection pattern without overlapping of the patterns.

  Next, the case where there is an overlap in the pattern due to the positional deviation due to the skew will be described with reference to FIG. Consider the case where the YK pattern and the MC pattern overlap due to the skew. In the n-th set, it can be determined that there is an overlap of patterns because the number of detections of the falling edge of the output signal is smaller than that in the ideal state.

  Then, the ideal interval value (y5, m5, c5) when the pattern period is changed is compared with the horizontal line pattern interval value (y6, m6, c6) to calculate a positional deviation correction value. As described above, the pattern interval is changed by changing the pattern cycle, and the correction value of the misalignment detection pattern can be calculated without overlapping of the patterns.

  Next, FIG. 9 will be described with reference to FIG.

  For example, in the case of color matching control in which eight misalignment detection patterns 30 are combined as one set including horizontal line patterns and oblique line patterns, first, one set of patterns 30 is output (S1-1) and detection is performed by the detection sensor 5a. (S1-2). Then, the number of detected patterns is calculated from the falling edge of the output signal of the detected pattern, and it is determined whether the number of output signal patterns is smaller than eight (S1-3).

  The falling edge is a boundary between a portion with a pattern and a portion without a pattern in the output signal. The falling edge corresponds to the boundary of the pattern because the output is present where the pattern is present and the output is absent where it is absent. When different patterns overlap, no falling edge appears because there is no part where there is no output during the pattern.

  If the number of patterns is eight, it is determined that there is no pattern overlap, and the misregistration detection pattern correction value is calculated (S1-4), and the calculated correction value is stored in the storage unit 200 (ROM 2) (S1-). 5). If the number of patterns is insufficient, that is, less than eight, it is determined that there is pattern duplication, and the detection pattern period is changed for each color (S1-6). The change is appropriately set according to the detected deviation, and depending on the color, it may include the case where there is no change in the cycle.

  When not all detection patterns used in one color matching control, that is, all pattern groups are output, the above-described one set of detection pattern output to storage of correction values are repeated (S1-7), all detection When the pattern output is finished, the detection pattern cycle is changed to the initial value, and the calculation flow is finished (S1-8).

  According to this flow, even if there is an overlap in the pattern, it is possible to continue misregistration detection after judging the pattern overlap, and it is possible to execute color misregistration correction. Furthermore, in the present flow, the pattern interval is gradually changed for each set, and a new occurrence of duplication is less likely to occur due to the detection pattern change.

  FIG. 10 is a flow of positional deviation detection pattern correction value calculation for detecting a pattern for each pattern group.

  When a color misregistration detection pattern set 30 is formed by combining eight horizontal lines and oblique lines into one set, control is further performed by setting the color misregistration detection pattern set 30 as one pattern group as an example, and all in one pattern group Is output (S2-1) and detected (S2-2).

  Next, the number of detected patterns is calculated from the falling edge of the output signal of each detected set of patterns, and it is determined whether the number of patterns in each set is smaller than eight (S2-3). If there is a set in which the number of patterns is less than eight, it is determined that there is a pattern overlap, and the detection data of the set having the overlap pattern is discarded (S2-4), and the detection pattern period is changed for each color (S2) -5). The change is appropriately set according to the detected deviation, and depending on the color, it may include the case where there is no change in the cycle.

  Next, positional deviation detection pattern correction values of each set are calculated (S2-6), and the calculated correction values are stored in the storage unit 120 (ROM 2) (S2-7).

  When not all detection patterns used in one color matching control are output, the process from the detection pattern output of one pattern group to the storage of the correction value storage unit 200 (ROM 2) is repeated (S2-8), When the detection pattern output ends, the detection pattern cycle is changed to the initial value (S2-9), and the calculation flow ends.

  According to this flow, even if there is an overlap in the pattern, it is possible to continue misregistration detection after judging the pattern overlap, and it is possible to execute color misregistration correction. Furthermore, this flow is suitable for reducing the load on the CPU 1 because the number of determinations of duplication is small.

  Next, a positional deviation detection pattern correction value calculation flow in which only the first set of patterns is determined to be redundant will be described with reference to FIG.

  For example, this is a case where color misregistration detection patterns 30 in which eight horizontal lines and diagonal lines are combined into one set, and further, eight sets of color misregistration detection pattern sets 30 are controlled as one pattern group.

  First, if it is the first set of detection patterns 30 (S3-1), the pattern is output (S3-2), and the detection pattern is detected by the detection sensor 5a (S3-3). The number of detected patterns is calculated from the falling edge of the output signal of the detected pattern, and it is determined whether the number of patterns is smaller than 8 (S3-4). If the number of patterns is less than eight, it is determined that there is pattern overlap, and the detection pattern period is changed for each color (S3-5). If the number of patterns is 8, it is determined that there is no pattern overlap, and the misalignment detection pattern correction value is calculated (S3-6), and the calculated correction value is stored in the storage unit 120 (ROM 2) (S3-7) . The change of the pattern cycle is appropriately set according to the detected deviation, and depending on the color, the case where there is no change of the cycle is included.

  Next, the detection patterns of the second to eighth groups, which are the remaining sets of pattern groups, are output (S3-8), and the detection patterns of each group are detected by sensors (S3-9). Unlike the first set, overlapping determination of patterns is not performed, and the positional deviation detection pattern correction value of each set is calculated (S3-10), and the calculated correction value is stored in the storage unit 120 (ROM 2) (S3) -1).

  The above is repeated when not all detection patterns used in one color matching control are output (S3-12), and when all the detection pattern output ends, the detection pattern period is changed to the initial value (S3) -13) The calculation flow ends.

  According to this flow, even if there is an overlap in the pattern, it is possible to continue misregistration detection after judging the pattern overlap, and it is possible to execute color misregistration correction. Also, in this flow, when patterns overlap, it is possible to estimate that all patterns often overlap in the same way, and the overlap judgment is made only in the first pair, and intervals in the subsequent pattern groups Because the number of repetitions of determination is small, it is suitable to reduce the load on the CPU 1.

100 image reader 5a detection sensor 170 control unit

JP, 2010-178286, A

Claims (4)

A plurality of image forming units having a first image carrier surface and developing latent images formed on the surface of the first image carrier with toners of different colors to form images of respective colors;
And a second image carrier which is driven at a predetermined speed and in which the images of the respective colors formed on the plurality of first image carriers in the image forming unit are registered in registration and superimposed. Have
In the image forming apparatus, the image of each color is transferred onto a recording medium by transferring the image of each color superimposed and transferred onto the second image carrier.
Pattern forming means for forming a pattern formed by the plurality of first image carriers and transferred to the second image carrier;
Pattern detection means for detecting the pattern transferred to the second image carrier;
The pattern includes a plurality of patterns with respect to the first image carrier,
Pattern duplication determination means for determining duplication of the plurality of patterns from the edge of the pattern detected by the pattern detection means;
Pattern cycle changing means for changing the pattern cycle of each color when there is a pattern overlap by the pattern overlap judging means;
An image forming apparatus comprising: The pattern forming unit forms a set of patterns consisting of a plurality of sets of repetitions, with the plurality of patterns as one set;
The image forming apparatus according to claim 1, wherein the overlap determining unit determines whether there is an overlapping set of patterns in the pattern set, and when there is a pattern overlap, the image forming apparatus according to claim 1, The pattern forming unit forms a set of patterns consisting of a plurality of sets of repetitions, with the plurality of patterns as one set;
The image forming apparatus according to claim 1, wherein the overlap determining unit determines an overlap of a first pattern in the pattern set, and does not perform determination in the other sets. Pattern correction value calculation means for calculating a misalignment detection pattern correction value from the pattern detected by the pattern detection means;
2. The image forming apparatus according to claim 1, further comprising: pattern correction value storage means for storing the correction value calculated by said pattern correction value calculation means.