JP2004264556A - Method and device for detecting the amount of misalignment and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure the influence of fluctuating factors such as oscillation or dispersion in the amount of misalignment that is detected. <P>SOLUTION: A pattern (PBk) which is formed of a standard color and at least one or more patterns which is formed by superposing the standard color and a non-standard color and varying the amount of misalignment of the non-standard color to the standard color (PA1 to PAn) are arranged as misalignment amount detecting patterns. Furthermore, many patterns (PB1 to PBn) in which the amount of misalignment of the non-standard color to the standard color is made a prescribed amount are positioned in a section for measuring the variation in the amount of misalignment, or positioned continuously over a long section (PB). A misalignment calculation means measures the values outputted by a sensor of these patterns to calculate the amount of misalignment, and determines the oscillation in the amount of misalignment, dispersion in density and the influence of noise. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a position shift amount detecting method for detecting a position shift amount between images formed by respective colors in an image forming apparatus such as a facsimile, a copying machine, a printer, and a multifunction peripheral, a position shift amount detecting apparatus, and an image forming apparatus. About.
[0002]
[Prior art]
Conventionally, in a color image forming apparatus, it is important to eliminate color misregistration in output images of magenta, cyan, yellow, and black for improving image quality.In particular, a writing optical system and an image carrier are separately provided for each color. In the case of the four-tandem tandem system having one set, color misregistration has been an important issue because images of each color are formed by different optical systems and image carriers. As a method for correcting this color shift (position shift between images of each color), a pattern for detecting a position shift is written on a transport belt or an intermediate transfer belt, and the pattern is read by a sensor to detect the amount of the position shift. Correction is performed by writing timing and optical system correction means.
[0003]
As shown in FIG. 8, one of the methods for detecting the amount of displacement is to place a cyan, magenta, or yellow line having the same width W1 at the interval W1 below a black line pattern arranged at the width W1 and the interval W1. In this case, a plurality of detection patterns in which D is sequentially changed in step S are prepared as detection patterns in which the shift amount of the color pattern with respect to the black pattern is D, and these are arranged in the reading direction of the sensor. As shown in FIG. 9, there is a method of calculating the amount of displacement from the intersection of approximate lines from the output of each detection pattern.
[0004]
Further, in the method of automatically adjusting the writing position disclosed in Japanese Patent Application Laid-Open No. HEI 6-1002 (Patent Document 1) previously filed by the present applicant, a two-color toner image is formed by an image carrier and detected by an optical sensor. By doing so, the size and shape of the formation region are made to substantially match.
Japanese Patent Application Laid-Open No. 2002-91119 (Patent Document 2) calculates a correction amount at three points from a maximum value, a minimum value, and a shifted patch.
In Japanese Patent Application Laid-Open No. 2002-40746 (Patent Document 3), the amount of displacement is measured at an approximate right and left straight line intersection.
[0005]
[Patent Document 1]
JP-A-6-1002
[Patent Document 2]
JP-A-2002-91119
[Patent Document 3]
JP-A-2002-40746
[0006]
[Problems to be solved by the invention]
However, when a pattern is arranged and the displacement is measured by the conventional displacement detection method described above with reference to FIGS. 8 and 9, when a variation factor such as vibration or variation is put on each measurement point, the calculated position is determined. There has been a problem that the shift amount is also affected by the fluctuation.
Also, the above-mentioned Patent Documents 1 to 3 do not take into account the measurement of the influence on the displacement amount caused by fluctuation factors such as vibration and variation.
[0007]
The present invention has been made in view of such a situation, and a position shift amount detection method capable of measuring an influence caused by a fluctuation factor such as vibration and variation with respect to a detected position shift amount. It is an object to provide a quantity detection device and an image forming device.
It is another object of the present invention to provide a position shift amount detection method, a position shift amount detection device, and an image forming apparatus capable of accurately obtaining an average value of a change in a position shift amount caused by the above-mentioned change factor. It is.
Another object of the present invention is to provide an image forming apparatus capable of achieving high image quality by performing correction using the average value of the above-described influence and variation on the amount of positional deviation.
[0008]
[Means for Solving the Problems]
In order to achieve such an object, the present invention has the following features.
According to the first aspect of the present invention, there is provided a position shift detecting method for reading a pattern formed on an endless moving unit by a plurality of image carriers by an optical detecting unit and detecting a position shift of writing by the plurality of image carriers. And a pattern (PBk) based on the reference color and at least one or more patterns (PA1 to PAn) obtained by superimposing the reference color and the non-reference color and changing the shift amount of the non-reference color with respect to the reference color are arranged. In addition, a large number of patterns (PB1 to PBn) or a long pattern are continuously arranged (PB1) in which the shift amount of the non-reference color with respect to the reference color is set to a predetermined fixed amount in a section where the shift amount variation is measured. By measuring the output value of these patterns by the optical detection means and calculating the amount of displacement from these measured output values, vibration of the displacement amount, density variations, and noise shadows can be obtained. Wherein the can measure.
[0009]
According to a second aspect of the present invention, the positional deviation amount is obtained from the average value of the output values from the optical detection means for the pattern of PB1 to PBn or PB and the output value of the optical detection means for the pattern of PBk, PA1 to PAn. The deviation amount can be measured as an average value of fluctuations due to vibration, density variation, and noise.
[0010]
According to a third aspect of the present invention, a plurality of patterns (PBk) formed by the reference colors are placed or lengthened, and the average value of the output values of the patterns by the optical detection means is set as the value of PBk, and the measurement of PBk is performed. It is characterized by improving accuracy.
[0011]
According to a fourth aspect of the present invention, there is provided a displacement detecting method for reading a pattern formed on an endless moving means by a plurality of image carriers by an optical detecting means and detecting a displacement amount of writing by the plurality of image carriers. A section in which the reference color and the non-reference color are formed in an overlapping manner, at least one pattern in which the shift amount of the non-reference color with respect to the reference color is changed is arranged (PA1 to PAn), and the output variation is measured. The pattern in which the reference color line is arranged on the non-reference color solid is long in the sub-scanning direction (PB), or the pattern in which the reference color line is arranged on the non-reference color solid is plural in the sub-scanning direction. It is arranged (PB1 to PBn), the output values from these patterns by the optical detection means are measured, and the amount of displacement is calculated from these measured output values, whereby fluctuation factors excluding the influence of vibration are eliminated. Is characterized in that the influence on the amount of displacement can be measured.
[0012]
The invention according to claim 5 is characterized in that the above-mentioned patterns PA1 to PAn or PB1 for measuring the sensitivity of the optical detection means to the amount of displacement are arranged close to each other so as to be less affected by fluctuations.
[0013]
According to a sixth aspect of the present invention, a plurality of patterns PA1 to PAn for measuring the sensitivity of the optical detection means to the shift amount are arranged in a plurality or continuously with the same shift amount, and the average value is obtained. It is characterized in that the measurement is hardly affected by fluctuation.
[0014]
The invention according to claim 7, wherein a pattern formed on the endless moving means by the plurality of image carriers is read by the optical detecting means, and a displacement amount of the writing by the plurality of image carriers is detected. The reference color and the non-reference color are formed so as to overlap with each other, and at least two or more patterns of a fixed amount or a pattern in which the shift amount of the non-reference color with respect to the reference color is changed (P1 to Pn). By measuring the output value of the optical detection means from the pattern and calculating the amount of deviation from the measured output values, the patch of each color in the pattern set of each color of the non-reference color is alternately measured by a method of measuring the amount of positional deviation. In order to measure the influence of vibration and fluctuation at the same distance on the image carrier, the pattern sets of the non-reference colors are arranged at the same distance. Characterized in that a shorter arrangement distance of the pattern.
[0015]
The invention according to claim 8 is characterized in that the line width of the pattern is sufficiently smaller than the spot diameter detected by the optical detection means.
[0016]
The invention according to claim 9, wherein a plurality of image carriers, an endless moving means for moving an image formed by the plurality of image carriers, and an optical detecting means for reading a pattern formed on the endless moving means A positional deviation amount detection device for detecting a positional deviation amount of an image formed by a plurality of image carriers, wherein the image carrier comprises a pattern (PBk) of a reference color, a reference color and a non-reference color. And at least one pattern (PA1 to PAn) in which the shift amount of the non-reference color with respect to the reference color is changed, and the variation of the shift amount is measured in a section where the shift amount of the non-reference color is changed. A large number of patterns (PB1 to PBn) or continuously long patterns (PB1) in which the amount of displacement is a predetermined constant amount are arranged, and output values from these patterns by the optical detection means are measured. Comprising a position deviation amount calculating means for calculating the measured positional deviation amount from the output value, the vibration of the displacement amount, and a concentration variation, the influence of noise can be measured.
[0017]
According to a tenth aspect of the present invention, the position shift amount calculating means outputs the average value of the output values from the optical detecting means for the patterns PB1 to PBn or PB and the output value of the optical detecting means for the patterns PBk and PA1 to PAn. The amount of deviation as an average value of the fluctuation due to the influence of vibration, density variation, and noise of the position deviation amount is measured from the value.
[0018]
According to an eleventh aspect of the present invention, in the image carrier, a plurality of patterns (PBk) formed by a reference color are placed or lengthened, and the position shift amount calculating means performs optical detection of the patterns. The average value of the output values by the means is set as the value of PBk, and the accuracy of measuring PBk is improved.
[0019]
The invention according to claim 12, wherein a plurality of image carriers, an endless moving means for moving an image formed by the plurality of image carriers, and an optical detecting means for reading a pattern formed on the endless moving means A displacement amount detection device that detects a displacement amount of an image formed by a plurality of image carriers, wherein the image carrier forms a reference color and a non-reference color in an overlapping manner, And at least one pattern in which the shift amount of the non-reference color is changed (PA1 to PAn), and a pattern in which the reference color line is arranged on the non-reference color solid in the section where the fluctuation of the output is measured is sub-scanned. In the sub-scanning direction (PB1 to PBn) or a plurality of patterns in which reference color lines are arranged on non-reference color solids (PB1 to PBn). And a displacement amount calculating means for calculating a displacement amount from the measured output value, and capable of measuring the influence of the fluctuation factor on the displacement amount excluding the influence of vibration. .
[0020]
A thirteenth aspect of the present invention is characterized in that the above-mentioned patterns PA1 to PAn or PB1 for measuring the sensitivity of the optical detection means to the amount of displacement are arranged close to each other so as to be less affected by fluctuations.
[0021]
According to a fourteenth aspect of the present invention, the plurality of patterns PA1 to PAn for measuring the sensitivity of the optical detection means to the shift amount are respectively arranged in a plurality or continuously with the same shift amount, and the average value is obtained. It is characterized in that the measurement is hardly affected by fluctuation.
[0022]
The invention according to claim 15, wherein a plurality of image carriers, an endless moving means for moving an image formed by the plurality of image carriers, and an optical detecting means for reading a pattern formed on the endless moving means A displacement amount detecting device for detecting a displacement amount of an image formed by a plurality of image carriers, wherein the image carrier forms a reference color and a non-reference color in an overlapping manner, and At least two or more patterns in which the shift amount of the non-reference color with respect to the color is changed or a fixed amount of patterns are arranged (P1 to Pn), the output value of the optical detection means is measured from these patterns, and the measured output value is obtained. The image carrier further includes a displacement amount calculating means for calculating a displacement amount, and the image carrier alternately arranges patches of each color in a pattern set of each color of a non-reference color, thereby obtaining a displacement amount calculating means. There order to determine the effect of vibrations and variations in the same distance on the image bearing member, characterized in that a shorter arrangement distance of the pattern than the respective color pattern set of non-reference color to the same distance arranged.
[0023]
The invention according to claim 16 is characterized in that the line width of the pattern is sufficiently smaller than the spot diameter detected by the optical detection means.
[0024]
According to a seventeenth aspect of the present invention, there is provided a position shift amount detecting device according to any one of the ninth to sixteenth aspects, and a position shift amount detected by the position shift amount detecting device is corrected at the time of image formation on recording paper. And an image forming unit that performs image formation by performing correction by the amount of displacement correcting unit when forming an image on a recording sheet.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of a position shift amount detection method, a position shift amount detection device, and an image forming apparatus according to the present invention will be described in detail with reference to the drawings.
First, a configuration related to image formation common to the embodiments will be described.
[0026]
The image forming apparatus as an embodiment of the present invention has a configuration in which image forming units of each color are arranged along a conveyor belt (endless moving means), as shown in FIG. 1, and is a so-called tandem type. It is said to be.
That is, along the transport belt 5 that transports the paper (recording paper) 4 that is separated and fed by the feed roller 2 and the separation roller 3 from the feed tray 1, in order from the upstream side in the transport direction of the transport belt 5. , A plurality of image forming units 6Y, 6M, 6C, 6BK are arranged.
The plurality of image forming units 6Y, 6M, 6C, and 6BK have the same internal configuration except for the color of the toner image to be formed. The image forming unit 6Y forms a yellow image, the image forming unit 6M forms a magenta image, the image forming unit 6C forms a cyan image, and the image forming unit 6BK forms a black image.
[0027]
Therefore, in the following description, the image forming unit 6Y will be specifically described. However, since the other image forming units 6M, 6C, and 6BK are the same as the image forming unit 6Y, the image forming units 6M, 6C, and 6BK Regarding each component, instead of Y attached to each component of the image forming apparatus 6Y, only symbols distinguished by M, C, and BK are displayed in the figure, and description thereof is omitted.
[0028]
The transport belt 5 is an endless belt wound around a driving roller 7 and a driven roller 8 that are driven to rotate. The drive roller 7 is driven to rotate by a drive motor (not shown), and the drive motor, the drive roller 7 and the driven roller 8 function as drive means for moving the transport belt 5 which is an endless moving means. .
[0029]
At the time of image formation, the papers 4 stored in the paper feed tray 1 are sent out in order from the top, and the first image forming unit 6Y is rotated by the transport belt 5 which is attracted and rotated by the transport belt 5 by the electrostatic attraction action. Where the yellow toner image is transferred.
[0030]
The image forming section 6Y includes a photoconductor drum 9Y as a photoconductor, a charger 10Y disposed around the photoconductor drum 9Y, an exposure device 11, a developing device 12Y, a photoconductor cleaner (not shown), and a static eliminator 13Y. And so on. The exposure device 11 is configured to irradiate laser beams 14Y, 14M, 14C, and 14BK, which are exposure lights corresponding to image colors formed by the image forming units 6Y, 6M, 6C, and 6BK.
[0031]
At the time of image formation, the outer peripheral surface of the photosensitive drum (image carrier) 9Y is uniformly charged by the charger 10Y in the dark, and then is exposed by the laser beam 14Y corresponding to the yellow image from the exposure device 11, An electrostatic latent image is formed. The developing unit 12Y visualizes this electrostatic latent image with yellow toner, whereby a yellow toner image is formed on the photosensitive drum 9Y.
[0032]
The toner image is transferred onto the sheet 4 by the operation of the transfer unit 15Y at a position (transfer position) where the photosensitive drum 9Y and the sheet 4 on the transport belt 5 are in contact with each other. By this transfer, an image is formed on the sheet 4 using yellow toner. After the transfer of the toner image, the photosensitive drum 9 </ b> Y is wiped of unnecessary toner remaining on the outer peripheral surface by the photosensitive member cleaner, then is discharged by the discharger 13 </ b> Y, and waits for the next image formation.
[0033]
The sheet 4 onto which the yellow toner image has been transferred by the image forming unit 6Y as described above is conveyed by the conveying belt 5 to the next image forming unit 6M. In the image forming unit 6M, a magenta toner image is formed on the photosensitive drum 9M by a process similar to the image forming process in the image forming unit 6Y, and the toner image is superimposed on the yellow image formed on the paper 4. Is transcribed.
The paper 4 is further conveyed to the next image forming units 6C and 6BK, and by the same operation, the cyan toner image formed on the photosensitive drum 9C and the black toner image formed on the photosensitive drum 9BK. Are superimposed and transferred on the sheet 4. Thus, a full-color image is formed on the sheet 4. The paper 4 on which the full-color superimposed image is formed is peeled off from the transport belt 5 and the image is fixed by the fixing device 16 and then discharged outside the image forming apparatus.
[0034]
Further, with the above-described configuration, each image forming unit forms a pattern for detecting a positional shift amount for detecting the positional shift amount according to the present invention on the transport belt 5, and the sensors 17, 18, and 19 form the pattern. The detected pattern is detected.
As shown in FIG. 1, the sensors (optical detection means) 17, 18 and 19 are disposed downstream of the image forming section 6BK so as to face the transport belt 5, and the transport belt 5 is driven by the drive roller 7. They are supported on the same substrate so as to be along a main scanning direction orthogonal to the moving direction.
Further, the displacement detection pattern formed on the conveyor belt 5 is optically detected by the sensors 17, 18, and 19, and thereafter, by the cleaning unit 20 disposed downstream of the sensors 17, 18, and 19. Removed.
[0035]
FIG. 2 shows an outline of a configuration for performing control as a displacement amount detection method according to each embodiment.
As shown in FIG. 2, the image forming apparatus as an embodiment of the present invention includes a misregistration detection pattern printing unit 101, the above-described sensors 17, 18, and 19 for detecting a printed misregistration detection pattern, and A displacement amount calculating means 102 for calculating a displacement amount between images of the respective colors formed using the detection results, and correcting the image formation based on the calculated displacement amount so as not to cause the displacement during image formation. The apparatus includes a displacement correcting unit 103 and a writing unit 104 that performs the correction to form an image on a recording sheet.
[0036]
FIG. 3 is a flowchart illustrating an outline of an operation when forming and detecting the above-described pattern for detecting a positional shift by controlling the positional shift amount detection method according to each embodiment.
First, the photosensitive drum (image carrier) 9 of the image forming apparatus prints a detection pattern on the transport belt 5 (Step S1). The sensors 17, 18, and 19 each read the printed pattern and output it as a signal (step S2), and the displacement amount calculating means 102 calculates the displacement amount between the images of each color from the read signal. (Step S3). On the basis of the calculated positional deviation amount, the positional deviation amount correcting means 103 determines a correction amount based on the exposure timing of the exposure unit 11 (step S4), and according to the correction amount, the exposure unit 11, the photosensitive drum 9, and the like. The writing means 104 forms an image on the recording paper (step S5).
[0037]
Next, a description will be given of a displacement detection method according to the first embodiment of the present invention.
In the first embodiment, a pattern (PBk) formed of a reference color, a reference color and a non-reference color are formed as a pattern for detecting a position shift, and the shift amount of the non-reference color with respect to the reference color is determined. At least one or more changed patterns are arranged (PA1 to PAn), and a large number of patterns (PB1 to PBn) in which the amount of shift of the non-reference color with respect to the reference color is fixed in the section where the change in the amount of shift is measured. Alternatively, they are continuously arranged long (PB).
The output values of these patterns detected by the sensors 17, 18, and 19 are measured by the displacement amount calculating means 102 to calculate the displacement amount, thereby measuring the influence of the vibration of the displacement amount, the density variation, and the noise. I do.
[0038]
FIG. 4 shows an example in which the position shift amount detection method according to the first embodiment is realized as one PBk, two PAn (PA1: 4 dot shift, PA2: 8 dot shift), and PB as 6 dots shifted and constant continuous. Shown in FIG.
Each patch may be arranged at intervals instead of being continuous as in the example shown in FIG. In addition, each patch may be formed by overlapping one line pattern and arranged at intervals, instead of being configured by a plurality of lines as in the example shown in FIG. In addition, the arrangement positions of the patterns PBk and PAn are arbitrary, and may be arranged between PB1 to PBn and PB.
[0039]
Here, the sensor output of the pattern PBk is VBk, the sensor output VAn of the pattern PAn, the sensor output at each sampling point of the pattern PB is VBn, and the average value of the sensor output at each sampling point of the pattern PB is VB.
When the output value corresponding to the pattern is determined, one point may be represented, or an average of a plurality of points before and after may be determined. The value after the filter processing may be used. This is the same when all output values according to the present invention are determined.
Assuming that the shift amount of the pattern PAn on the image data is DAn,
D = DA2−DA1 = 8−4 = 4dot
The sensor sensitivity to the pattern shift is
ΔV = (VA2−VA1) / D
[0040]
In this embodiment, assuming that the shift amount on the image data of the pattern PB is Z1, the displacement amount of each sampling point of the pattern PB is as follows.
Z1 = 6dot
ΔXi = (VBi−VBk) / ΔV−Z1 (i = 1 to n)
Is obtained.
If this measurement result is statistically processed, the average value of the deviation, the distribution of the variation, and the standard deviation can be obtained. Thus, according to the position shift detection method according to the present embodiment, it is possible to grasp the state of the change in the position shift.
[0041]
Here, from the average value of the output values from the sensors 17, 18, and 19 for the patterns PB1 to PBn or PB, and the output values from the sensors 17, 18, and 19 for the patterns PBk, PA1 to PAn, When measuring the deviation amount as the average value of the fluctuation due to the influence of the vibration, the density variation, and the noise, similarly, using the average value VB of the sensor output at each sampling point of the pattern PB,
ΔX = (VB−VBk) / ΔV−Z1
Thus, the average deviation amount of the fluctuation can be obtained.
[0042]
When PAn is only one of PA1, VB1 or VB may be used as VA2 when calculating the sensor sensitivity.
ΔV = (VB1−VA1) / D
In this case, D = DB1−DA1.
[0043]
In the displacement amount detection method according to the first embodiment, since the measurement accuracy of the shift amount is affected by the measurement accuracy of the pattern PBk of only the reference color, the pattern (PBk) formed by the reference color is used. Are set or lengthened, and the average value of the output values from the sensors 17, 18, and 19 is set as the value of PBk, and the measurement accuracy of PBk is improved. Arrangement position of PBk is arbitrary, and may be arranged in the middle of PA or PB.
[0044]
As described above, according to the first embodiment of the present invention, the detection pattern in which the reference color lines are arranged at the interval W1 and the shift amount of the non-reference color pattern with respect to the reference color pattern is D, A plurality of detection patterns in which D is changed in order are prepared, these are arranged in the reading direction of the sensor as shown in FIG. 4, and the displacement amount is obtained from the intersection of the approximate straight lines based on the output of the detection pattern from each sensor. Even if the calculated position deviation is affected by fluctuations due to vibrations, variations, etc. at each measurement point due to the method, the effect of the fluctuations on the position deviation is measured. can do.
In addition, since the displacement amount is not measured at the time interval of the output change of the sensor but is measured by the magnitude of the output level of the sensor, the fluctuation at the time of reading the pattern is excluded, and the displacement is grasped as the displacement amount of the pattern. be able to. Thus, it is possible to measure the variation in the amount of positional deviation at the time of pattern writing in consideration of the positional deviation of the writing means and the deviation due to time.
[0045]
Further, when the average value of the variation is obtained from the situation of the variation of the displacement amount obtained as described above, and the average value of the variation is corrected by a constant sub-scan registration adjustment, there is a variation in the displacement amount. Also, it is possible to obtain a shift amount that can minimize the shift amount after the correction.
[0046]
Further, even if the measurement accuracy of the displacement amount may be affected by the measurement accuracy of the pattern PBk of only the reference color in the above-described method of measuring the displacement amount, the measurement accuracy of the pattern PBk can be improved. .
[0047]
Next, a description will be given of a position shift amount detection method according to a second embodiment of the present invention.
In the second embodiment, a reference color and a non-reference color are formed so as to overlap each other as a pattern for detecting a position shift, and at least one or more patterns in which the shift amount of the non-reference color with respect to the reference color is changed are arranged (PA1). To PAn), a pattern in which a reference color line is arranged on a non-reference color solid in a section where output fluctuation is measured is arranged long in the sub-scanning direction (PB), or a reference color line is arranged on a non-reference color solid. Are arranged in the sub-scanning direction (PB1 to PBn).
The sensors 17, 18, and 19 measure the output value from these patterns, and the displacement amount calculating means 102 calculates the displacement amount from these measured output values. Measure the effect on the amount of deviation.
[0048]
FIG. 6 shows an example in which the second embodiment is applied to a case where PAn is two (PA1: 4 dot shift, PA2: 8 dot shift), and PB is 6 dots shifted and is constant and continuous. Each patch may be arranged at intervals instead of being continuous as in this embodiment. Further, each patch does not need to be composed of a plurality of lines as in the present embodiment, but may be formed by overlapping one line pattern or may be arranged at intervals.
The position of PAn is arbitrary, and may be located between PB1 to PBn and PB.
[0049]
Here, the sensor output of the pattern PAn is VAn, the sensor output of each sampling point of the pattern PB is VBn, the average value of the sensor output of each sampling point of the pattern PB is VB, and the shift amount of the pattern PAn on the image data is DAn. Then
D = DA2−DA1 = 8−4 = 4dot
The sensor sensitivity to the pattern shift is
ΔV = (VA2−VA1) / D
[0050]
In order to convert the variation of each sampling point of the pattern PB into the amount of positional deviation, assuming that the shift amount on the image data of the pattern PB is Z1, in this embodiment,
Z1 = 6dot
ΔXi = VBi / ΔV (i = 1 to n)
Thus, the fluctuation of the measurement method itself, excluding the fluctuation factor of the deviation, can be converted into the positional deviation amount and measured.
If this measurement result is statistically processed, it is possible to obtain the distribution of variation and the standard deviation. This makes it possible to grasp the state of the change.
[0051]
As described above, according to the second embodiment of the present invention, the position shift between the reference color and the non-reference color is caused by the fluctuation factor in the position shift amount measured in the first embodiment. The area of the non-reference color that is not covered by the reference color on the image data of the pattern is always kept constant in the fluctuation measurement section even when the pattern is generated. Its own variation can be measured.
Also, since the amount of displacement is measured not by the time interval of the sensor output change but by the level of the sensor output level, fluctuations during pattern reading are eliminated, and the measurement method itself during pattern writing is eliminated. Can be measured.
[0052]
In the displacement measurement method according to the first or second embodiment, the sensitivity of the sensors 17, 18, and 19 to the displacement detection is measured from the patterns PA1 to PAn or PB1. When affected by the factors, there is a possibility that an error occurs in the sensitivity. Therefore, the patterns PA1 to PAn and PB1 used for measuring the sensitivity may be formed so as to be close to each other.
Thereby, the influence of the fluctuation factor on the sensitivity measurement can be suppressed.
[0053]
In the displacement measurement method according to the first or second embodiment, the sensitivity of the sensors 17, 18, and 19 to the displacement detection is measured from the patterns PA1 to PAn or PB1. When affected by factors, errors may occur in the sensitivity. Therefore, the patterns PA1 to PAn used for the measurement of the sensitivity may be arranged plurally or consecutively (over a long distance) with the same shift amount, and an average value thereof may be obtained.
Thereby, the influence of the fluctuation factor on the sensitivity measurement can be suppressed. The arrangement position of PA1 to PAn is arbitrary, and may be arranged in the middle of PA or PB.
[0054]
Next, a description will be given of a displacement detection method according to a third embodiment of the present invention.
In the third embodiment, as a misregistration detection pattern, a reference color and a non-reference color are formed so as to overlap each other, and a pattern in which the displacement amount of the non-reference color with respect to the reference color is changed or a pattern of a fixed amount is at least two. By arranging one or more (P1 to Pn), the output values of the sensors 17, 18, and 19 are measured from these patterns, and the amount of positional deviation between images of each color is calculated from the measured output values, thereby obtaining the amount of positional deviation. Is measured, patches of each color of a pattern set of each non-reference color are alternately arranged.
As a result, in order to measure the influence of vibration and fluctuation at the same distance on the photosensitive drum 9, the pattern arrangement distance is shorter than that in the positional deviation detection method in which the pattern sets of the non-reference colors are arranged at the same distance. Is what you can do.
[0055]
In other words, when the pattern must be arranged at a relatively long distance in order to take into account the influence of fluctuation factors such as vibration in the sub-scanning, if this long distance is arranged for each non-reference color, the overall length of the pattern becomes very large. On the other hand, by alternately arranging the patches of each color, the measurement of each color can be performed within the same distance, and the total length of the pattern of each color can be shortened.
[0056]
An example in which the third embodiment is applied to, for example, superimposing a pattern of a reference color and one line of a non-reference color into one patch, and sequentially arranging the image data by changing the shift amount is shown in FIG. 7 (B). In this case, rather than arranging the pattern diagram 7 (A) for each color in a fixed section in order to consider the influence of fluctuation factors such as sub-scanning vibration, the pattern of each color is set within the same fixed section as shown in FIG. 7 (B). If they are arranged alternately, the total pattern length can be shortened.
In addition to the present embodiment, the present invention can be applied to a pattern in which one patch includes a plurality of lines, for example, a pattern similar to the pattern PBk, PA1 to PAn, or PB1 to PBn in the first or second embodiment described above. It is possible.
[0057]
As described above, according to the third embodiment of the present invention, a pattern in which the reference color and the non-reference color are superimposed is arranged, and the displacement amount is measured from the outputs of the sensors 17, 18, and 19. If the pattern must be arranged at a relatively long distance in order to consider the effects of fluctuation factors such as sub-scanning vibration, if this long distance is arranged for each non-reference color, the overall length of the pattern will be very long. In contrast, by arranging patches of each non-reference color and the reference color alternately for each color, each color can be measured within the distance of the pattern in one non-reference color, thereby shortening the entire pattern length. be able to.
[0058]
Further, in each of the above-described embodiments, the line width of the pattern used for detecting the amount of displacement is sufficiently smaller than the spot diameter in the detection of the sensors 17, 18, and 19.
As a result, it is possible to suppress a change in the output of the light receiving element due to the pattern width being relatively large with respect to the spot diameter.
[0059]
Further, the image forming apparatus corrects the position shift amount detected by the position shift amount detection method as each of the embodiments described above by the position shift amount correction unit 103, and then forms an image on a recording sheet. It is possible to achieve high image quality in image formation on recording paper.
[0060]
Each of the above-described embodiments is a preferred embodiment of the present invention, and can be variously modified and implemented without departing from the gist of the present invention.
For example, it has been described that the patterns used for detecting the positional deviation are formed at three places on the conveyor belt, and the sensors provided at the three places detect the patterns. Depending on the detection item), it may be optimal, for example, at two places at both ends of the conveyor belt or at one place at the center.
[0061]
Further, the configuration in which the pattern used for detecting the positional deviation is formed on the transport belt and detected is described, but the present invention is not limited to this as long as it is an endless moving unit that moves the image transferred from the image carrier. For example, the present invention is similarly applicable to a configuration using an intermediate transfer belt.
[0062]
【The invention's effect】
As described above, according to the displacement amount detection method of the present invention, it is possible to measure the influence on the displacement amount caused by fluctuation factors such as vibration and variation, and to accurately calculate the average value of the variation.
For this reason, if the correction is performed using the positional deviation amount calculated by this method, it is possible to correct the error due to the variation in correcting the positional deviation by the constant registration adjustment so as to minimize the error.
In addition, since the displacement amount is not measured at the time interval of the output change of the sensor but is measured by the magnitude of the output level of the sensor, the fluctuation at the time of reading the pattern is excluded, and the displacement amount of the pattern is grasped. be able to. For this reason, it is possible to measure the variation in the amount of displacement during pattern writing in consideration of the displacement due to the arrangement interval of the writing means and time.
[0063]
In addition, by alternately arranging the patterns used for position shift detection for each color, each color can be measured within substantially the same distance as one non-reference color pattern, so that the entire pattern length can be reduced and the amount of position shift can be reduced. Detection time can be shortened.
[0064]
In addition, the same effect as the above-described method of detecting each position shift amount of the present invention can also be obtained by each position shift amount detection device of the present invention.
[0065]
Further, according to the image forming apparatus of the present invention, it is possible to achieve high image quality in image formation on recording paper by correcting the position shift detected by each of the position shift amount detecting devices of the present invention. it can.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an outline of a configuration related to image formation common to respective embodiments of the present invention.
FIG. 2 is a block diagram illustrating an outline of a configuration for performing control as a displacement amount detection method according to each embodiment.
FIG. 3 is a flowchart illustrating an outline of an operation when forming and detecting a pattern for detecting a position shift by control as a position shift amount detection method according to each embodiment;
FIG. 4 is a view exemplifying a sub-scanning fluctuation influence measurement pattern which is a misregistration detection pattern in the first embodiment.
FIG. 5 is a diagram exemplifying a method of calculating an influence of a sub-scanning positional deviation amount variation in the positional deviation amount detection method as the first embodiment.
FIG. 6 is a diagram exemplifying an influence measurement pattern of detection fluctuation, which is a misregistration detection pattern in the second embodiment.
FIG. 7 is a diagram exemplifying a misregistration detection pattern according to a third embodiment.
FIG. 8 is a diagram showing a conventional misregistration amount detection pattern.
FIG. 9 is a diagram illustrating a conventional method for calculating a displacement amount.
[Explanation of symbols]
5 Conveyor belt (endless moving means)
6 (6Y, 6M, 6C, 6BK) Image forming unit
9 (9Y, 9M, 9C, 9BK) Photoconductor drum (image carrier)
11 Exposure unit
17, 18, 19 sensors (optical detection means)
20 Cleaning means
102 Position shift amount calculating means
103 Position shift amount correction means

Claims (17)

A displacement detection method for reading a pattern formed on the endless moving means by a plurality of image carriers by an optical detection means and detecting a displacement amount of writing by the plurality of image carriers,
A pattern (PBk) based on the reference color and at least one or more patterns (PA1 to PAn) in which the reference color and the non-reference color are overlapped and the shift amount of the non-reference color with respect to the reference color is changed,
Also, a large number of patterns (PB1 to PBn) or continuously long patterns (PB1) in which the shift amount of the non-reference color with respect to the reference color is set to a predetermined constant amount in the section for measuring the shift amount of the shift amount,
By measuring the output value of the optical detection means from these patterns and calculating the displacement amount from these measured output values, it is possible to measure the vibration of the displacement amount, the density variation, and the influence of noise. To detect the amount of displacement. From the average value of the output values of the PB1 to PBn or the pattern of the PB from the optical detection means and the output value of the PBk and the pattern of the PA1 to PAn by the optical detection means, the vibration of the displacement amount, the density variation, 2. The method according to claim 1, wherein the amount of deviation as an average value of fluctuation due to the influence of noise can be measured. It is desirable to place or lengthen a plurality of patterns (PBk) formed by the reference color and to use the average value of the output values of the patterns by the optical detection means as the PBk value to improve the measurement accuracy of the PBk. 3. The method according to claim 1, wherein the amount of misalignment is detected. A displacement detection method for reading a pattern formed on the endless moving means by a plurality of image carriers by an optical detection means and detecting a displacement amount of writing by the plurality of image carriers,
The reference color and the non-reference color are formed so as to overlap with each other, and at least one or more patterns in which the shift amount of the non-reference color with respect to the reference color is changed are arranged (PA1 to PAn).
Either a pattern in which a reference color line is arranged on a non-reference color solid in a section where output fluctuation is measured is arranged long in the sub-scanning direction (PB), or a pattern in which a reference color line is arranged on a non-reference color solid Are arranged in the sub-scanning direction (PB1 to PBn),
By measuring output values from the patterns by the optical detection means and calculating the displacement amount from the measured output values, it is possible to measure the influence of the variation factor on the displacement amount excluding the influence of vibration. A method for detecting the amount of positional deviation. 5. The pattern according to claim 1, wherein the patterns PA1 to PAn or PB1 for measuring the sensitivity of the optical detection means to the displacement amount are arranged close to each other so as to be less affected by fluctuations. The described method of detecting the amount of displacement. By arranging a plurality of patterns PA1 to PAn for measuring the sensitivity to the shift amount of the optical detection means with the same shift amount or continuously, and taking the average value, the sensitivity measurement is less affected by fluctuation. 5. The method according to claim 1, wherein the positional deviation amount is detected. A displacement detection method for reading a pattern formed on the endless moving means by a plurality of image carriers by an optical detection means and detecting a displacement amount of writing by the plurality of image carriers,
A reference color and a non-reference color are formed so as to overlap with each other, and at least two or more patterns in which the shift amount of the non-reference color with respect to the reference color is changed or a fixed amount are arranged (P1 to Pn), and optical detection is performed from these patterns. By measuring the output value by the means and calculating the shift amount from these measured output values, a method of measuring the position shift amount,
By alternately arranging the patches of each color in the pattern set of each color of the non-reference color, the pattern set of each color of the non-reference color is set at the same distance when measuring the influence of vibration and fluctuation at the same distance on the image carrier. A method for detecting a displacement amount, characterized in that the arrangement distance of a pattern can be made shorter than the arrangement distance. 8. The method according to claim 1, wherein a line width of the pattern is sufficiently smaller than a spot diameter detected by the optical detection unit. A plurality of image carriers, endless moving means for moving an image formed by the plurality of image carriers, and optical detecting means for reading a pattern formed on the endless moving means; A position shift amount detection device that detects a position shift amount of an image formed by the carrier,
The image carrier,
A pattern (PBk) based on the reference color and at least one or more patterns (PA1 to PAn) in which the reference color and the non-reference color are overlapped and the shift amount of the non-reference color with respect to the reference color is changed,
Also, a large number of patterns (PB1 to PBn) or continuously long patterns (PB1) in which the shift amount of the non-reference color with respect to the reference color is set to a predetermined constant amount in the section for measuring the shift amount of the shift amount,
An output value from the optical detection unit from these patterns is measured, and a displacement amount calculating unit that calculates a displacement amount from these measured output values is provided,
A displacement detecting device capable of measuring the influence of vibration, density variation and noise of the displacement. The position shift amount calculating means calculates a position based on an average value of output values from the optical detecting means for the PB1 to PBn or the pattern of the PB and an output value of the optical detecting means for the PBk and the patterns of PA1 to PAn. 10. The displacement amount detecting apparatus according to claim 9, wherein the displacement amount is measured as an average value of the variation due to the influence of vibration, density variation, and noise of the displacement amount. The image carrier is provided with a plurality of patterns (PBk) formed by the reference colors or by lengthening the patterns,
11. The position shift amount according to claim 9, wherein the position shift amount calculating unit sets an average value of output values of the pattern by the optical detection unit as the value of the PBk to improve the measurement accuracy of the PBk. Detection device. A plurality of image carriers, endless moving means for moving an image formed by the plurality of image carriers, and optical detecting means for reading a pattern formed on the endless moving means; A position shift amount detection device that detects a position shift amount of an image formed by the carrier,
The image carrier,
A reference color and a non-reference color are formed so as to overlap each other, and at least one or more patterns in which the shift amount of the non-reference color with respect to the reference color is changed are arranged (PA1 to PAn).
Either a pattern in which a reference color line is arranged on a non-reference color solid in a section where output fluctuation is measured is arranged long in the sub-scanning direction (PB), or a pattern in which a reference color line is arranged on a non-reference color solid Are arranged in the sub-scanning direction (PB1 to PBn),
A position shift amount calculating unit that measures an output value of the optical detection unit from these patterns and calculates a position shift amount from the measured output value;
An apparatus for detecting a displacement amount, characterized in that it is possible to measure the influence of a variation factor on the displacement amount excluding the influence of vibration. 13. The pattern according to claim 9, wherein patterns PA1 to PAn or PB1 for measuring the sensitivity of the optical detection means to the amount of displacement are arranged close to each other so as to be less affected by fluctuations. The positional deviation amount detecting device as described in the above. By arranging a plurality of patterns PA1 to PAn for measuring the sensitivity to the shift amount of the optical detection means with the same shift amount or continuously, and taking the average value, the sensitivity measurement is less affected by fluctuation. 13. The positional deviation amount detecting device according to claim 9, wherein: A plurality of image carriers, endless moving means for moving an image formed by the plurality of image carriers, and optical detecting means for reading a pattern formed on the endless moving means; A position shift amount detection device that detects a position shift amount of an image formed by the carrier,
The image carrier,
A reference color and a non-reference color are formed so as to overlap with each other, and at least two or more patterns of a fixed amount or a pattern in which the shift amount of the non-reference color with respect to the reference color is changed (P1 to Pn),
A position shift amount calculating unit that measures an output value by the optical detection unit from these patterns and calculates a shift amount from the measured output value,
The image carrier,
By alternately arranging patches of each color in the pattern set of each color of the non-reference color, when the position shift amount calculating means measures the influence of vibration and fluctuation at the same distance on the image carrier, each color of the non-reference color Wherein the pattern arrangement distance can be made shorter than the case where the pattern sets are arranged at the same distance. 16. The apparatus according to claim 9, wherein a line width of the pattern is sufficiently smaller than a spot diameter detected by the optical detection unit. A position shift amount detection device according to any one of claims 9 to 16,
Position shift amount correction means for correcting the position shift amount detected by the position shift amount detection device at the time of image formation on recording paper,
An image forming apparatus, wherein when forming an image on a recording sheet, the image is formed by performing correction by the displacement amount correcting means.

Images