JPH04317247A - Digital color copying machine - Google Patents

Abstract

PURPOSE:To correct the positional deviation even when the deviation occurs due to a lapse of time by detecting the amount of the positional deviation of an output image with an original reading means and correcting an image forming position for each color corresponding to the amount of the positional deviation. CONSTITUTION:A pattern image for positional deviation detection is formed on a sheet of copy paper and the pattern image is read with an original reading means 10 in the same manner as a normal original reading process. The positional deviation among the images in each color is detected and the deviation is corrected. At this time, each kind of deviation pattern is corrected independently from each other. The sheet of copy paper on which the pattern image is copied, that is, the original, is automatically carried to an original mount 109 by means of a branching claw 141 and carrying rollers 142 and 143 used as a carrying means to permit the original to be read with the original reading means 10.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital color copying machine which obtains a color image by superimposing toner images of each color onto a transfer paper.

0002

2. Description of the Related Art FIG. 17 shows the configuration of a general digital color copying machine. Main body 100 of this digital color copying machine
is based on the scanner unit 101 for reading a document, the image processing unit 102 that electrically processes the image signal output as a digital signal by the scanner unit 101, and the image recording information of each color from the image processing unit 102. It is comprised of a printer section 103 that copies images onto transfer paper. As shown in FIG. 1, the document reading device of a digital color copying machine uses a document 1 placed on a contact glass 109.
10 is read by a reading device mounted on a carriage 104 that moves parallel to the lower surface of the contact glass 109 along a guide rod 111. As shown in the figure, the carriage 104 includes two fluorescent lamps 105 placed on both sides of the document illumination position, and a positioning roller 106 that rolls against a contact glass 109.
, lens array 107, CC provided at its imaging position
A CCD linear image sensor (color equal magnification) 108 is mounted, and while the carriage 104 moves at a constant speed along the guide rod 111, the reflected light from the document illuminated by the fluorescent lamp 105 is transferred to the CCD 108 by the lens array 107. It is imaged and read. Note that an ADF 131 is provided on the contact glass 109 to automatically transport the original 110 onto the contact glass 109. That is, the original 110 set on the original table 132 is transferred to the calling roller 133 and the separation conveying roller 1.
34 and conveyor rollers 135, and further conveyed by a conveyor belt 136. When the copying operation is completed, the original 110 is ejected onto the original tray 138 by the conveyor belt 136 and the ejecting roller 137.

[0003] In the image processing section 102, each CCD 10
The digital signal inputted from 8 is converted into a signal for forming a record of each color. Further, the printer section 103 includes a plurality of laser beam scanning devices 112 corresponding to each color, which receive signals from the image processing section 102 and oscillate laser beams.
C, 112M, 112Y, 112BK, and a plurality of photoreceptors 114C, 114 whose surfaces undergo exposure processing by receiving laser beams from the respective laser beam scanning devices.
M, 114Y, 114BK, and chargers 115C, 115M, 115Y, 11 corresponding to the number of photoreceptors 114, which apply charging processing to the surface of the photoreceptor 114 before performing exposure processing.
5BK and a photoconductor 11 that performs a development process on the electrostatic latent image formed on the photoconductor 114 by charging and exposure processing.
4 and a plurality of developing rollers 124C, 124
Developer storage units 125C, 125M, 1 store M, 124Y, 124BK, cyan developer C, magenta developer M, yellow developer Y, and black developer BK, respectively.
Developing devices 116C and 11 consisting of 25Y and 125BK
6M, 116Y, 116BK, and the image on the photoreceptor 114 that has been developed by the developing device 116 is transferred from the paper feeding unit 119 to the paper feeding roller 118, registration roller 120,
Transfer devices 117C, 117M, 117Y, 117 corresponding to the number of photoreceptors 114 perform transfer processing at predetermined positions on the transfer paper conveyed by the transfer belt 121.
BK, a fixing roller 122 that performs fixing processing on the transferred image after processing the transfer paper, and a fixing roller 122 that performs fixing processing on the transferred image after processing the transfer paper, and a main body 100 that transfers the transfer paper after the fixing processing.
It has a discharge roller 123 for discharging the paper to the outside.

Next, the laser beam scanning device 112C,
In order to explain 112M, 112Y, and 112BK in more detail, 112Y will be taken as an example and explained using FIGS. 18 and 19. FIG. 18 is a perspective view of the laser beam scanning device 112Y, which includes a laser unit 225Y that includes a semiconductor laser for generating a laser beam and a condensing lens (not shown) and emits a collimated beam 224Y, and a laser unit 225Y that emits a collimated beam 224Y. Cylindrical lens 2 that focuses the beam
28Y and the focused laser beam to the motor 226Y.
a polygon mirror 227Y that is interlocked with the rotational drive and deflects toward the photoreceptor 114Y, and the polygon mirror 22
an fθ lens 229Y that images the light deflected by the polygon mirror 227Y onto the photoreceptor 114Y, and two mirrors 230Y that reflect the light deflected by the polygon mirror 227Y and guide it to a predetermined position on the photoreceptor 114Y. and 231Y, and the mirrors 230Y and 231Y outside the scanning area of the photoreceptor 114Y.
A mirror 235Y further reflects the reflected light from the mirror 235Y, and in order to receive the reflected light from the mirror 235Y and make the recording start position constant for each main scanning direction, a laser beam heading toward the optical scanning area is detected for each scanning. generates a synchronization detection signal,
For example, the beam detection means 236Y includes a PIN photodiode.

Further, as shown in FIG. 19, which is a cross-sectional view of the laser beam scanning device 112Y, a cylindrical lens 228Y, an fθ lens 229Y, and a polygon mirror 227
Y, mirrors 230Y, and 231Y are each housed in an optical housing 233Y, and a dustproof glass 232Y is installed at the beam exit portion. Further, a cover 234Y is attached to the optical housing 233Y, and the inside thereof has a sealed structure. This optical housing 233Y is connected to the digital color copying machine main body 100.
It is fixed to the front and rear side plates (not shown).

[0006] In such a digital color copying machine having a plurality of photoreceptors, since images of each color are successively superimposed on the same transfer paper, highly accurate positioning of the images of each color is required. If the position of each color image on the transfer paper deviates from the predetermined position, color misregistration will occur in the color print that is formed, which will appear as a change in the tone of the image or color blurring, resulting in a poor quality color print.

The types of misalignment of transferred images will be explained using FIGS. 20 to 25. In the figure, the X direction is the transfer paper conveyance direction (sub-scanning direction), and the Y direction is the laser beam scanning direction (main scanning direction). Moreover, solid lines indicate normal images, and broken lines indicate images that are off-center. The broken line in FIG. 20 is the sub-scanning parallel shift. The causes of this sub-scanning parallel deviation include a parallel deviation of the laser beam scanning line on the photoreceptor 114, a deviation in the distance between the photoreceptors, and a deviation in the writing timing. The broken line in FIG. 21 is the sub-scanning tilt shift. The causes of this sub-scanning tilt shift include tilt shift of the laser beam scanning line on the photoconductor 114 and mounting shift of the photoconductor 114 to the main body 100 (
diagonal mounting), etc. The broken line in FIG. 22 is the sub-scanning distortion deviation. The cause of this sub-scanning distortion shift is that the photoreceptor 11
There is a distortion of the laser beam scanning line on 4. The broken line in FIG. 23 is the main scanning parallel shift. The causes of this main scanning parallel deviation include a deviation in the modulation start timing of the laser beam and a deviation in the transfer paper conveyance direction. The broken line in FIG. 24 is the main scanning magnification shift. The causes of this main scanning magnification shift include a shift in the laser beam modulation clock, a shape error and mounting error of the lens in the scanning optical system, and a shift in the optical path alignment of the scanning optical system. The broken line in FIG. 25 is the main scanning distortion deviation. The causes of this main scanning distortion include errors in the partial shape and mounting of the lenses in the scanning optical system, and inclination of the optical path adjustment of the scanning optical system. The transferred image on the transfer paper is a combination of the above-mentioned deviations. Therefore, in such devices, alignment adjustment work has been performed when assembling the device or installing the device.

[0008]

[Problem to be Solved by the Invention] However, even once adjustments are made, the positional relationships between the various parts and units within the device may be delicate due to movement of the device or repair/maintenance of the device (for example, replacement of the photoreceptor). This will cause a positional shift in the image. Further, thermal expansion of the device due to changes in the surrounding environmental temperature also causes image positional displacement. As described above, the positional deviation of images due to changes over time deteriorates the quality of the color prints that are formed, and has become a major problem.

Therefore, in order to solve the above problem, the present invention reads the output image with a scanner section, detects the positional deviation, corrects the image forming position of each color according to the amount of positional deviation, and adjusts the position. It is an object of the present invention to provide a digital color copying machine that forms color prints of good quality without deviation.

0010

[Means for Solving the Problems] The above object is to provide an original reading means for reading an original on an original platen, an image processing section for processing a signal from the original reading means into image recording signals of a plurality of different colors, and an image processing unit for processing a signal from the original reading means into image recording signals of a plurality of different colors. In a digital color copying machine equipped with a color image forming means that forms and superimposes a plurality of images of different colors on the same transfer paper based on a recording signal to obtain a single color image, the positional deviation between each color image is corrected. In order to detect and correct this positional deviation, this is achieved by a first means that performs control to form a pattern image for positional deviation detection on the transfer paper, which is read by the document reading means. In addition, the above object is achieved by providing a second means that includes a conveying means for conveying the transfer paper on which the pattern image is formed to the document table in the first means.
This is accomplished by the following means.

[0011]

In the present invention, a pattern image for detecting positional deviation is formed on a transfer paper, this pattern image is read by the document reading means, positional deviation between each color image is detected, and this positional deviation is corrected. In this case, the various deviation patterns shown in FIGS. 20 to 25 described above are corrected independently. Further, the transfer paper on which the pattern image has been transferred, that is, the document, is automatically sent to a document table (contact glass) by a conveying device for reading by a document reading device.

0012

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. Note that the same parts as in the conventional example are given the same reference numerals, and redundant explanations will be omitted. FIG. 1 is a block diagram of a digital color copying machine according to an embodiment of the present invention. In the present invention, as will be described later, a pattern image for detecting positional deviation is formed on transfer paper, this pattern image is read by the scanner unit 101, positional deviation between each color image is detected, and this positional deviation is corrected. However, for this reading, it is necessary to set the transfer paper on which the pattern image is formed, that is, the original, on the contact glass 109. Therefore, a branch claw 141 and transport rollers 142 and 14 are used to switch from the normal paper ejection path and transport the original to the scanner section 101.
It has 3. As will be explained later, the positional shift of the image is
Since this occurs when the device is moved or when the surrounding environmental temperature changes, it is not necessary to always correct the positional shift. Therefore, the document may be manually set in the scanner section 101 by an operator or a service person.

Next, a description will be given of means for forming a pattern for detecting positional deviation on a transfer paper, reading the transfer paper on which this pattern is formed by the scanner section 101, and detecting a positional deviation. First, each laser beam is modulated by the signal from the pattern image signal generating means, and the above-mentioned image formation and
A pattern image of each color is formed on the transfer paper by the transfer means. This pattern for detecting positional deviation is, for example, shown in FIG.
An image like this can be used. As shown in the figure, pattern images of each color are formed on the left end, center, and right end of the leading edge of the transfer paper. Here, D(B K ~C) is an image for detecting the main scanning position shift amount at the left end, and E(BK ~
C) is an image for detecting the amount of main-scanning positional deviation at the center, F(BK ~ C) is an image for detecting the amount of main-scanning positional deviation at the right end, and G( BK ~C
) is an image for detecting the amount of sub-scanning positional deviation at the left end, H(BK ~ C) is an image for detecting the amount of sub-scanning positional deviation at the center, and I(B K ~C) is an image for detecting the amount of sub-scanning positional deviation at the center. This is an image for detecting the amount of sub-scanning positional deviation at the right end. Note that the subscripts BK, M, Y, and C indicate the colors of each image. Here, we will focus on the positional deviation of each color image with respect to the BK image. d(c ~ y), e(c ~ y), f(
c to y) is the main scanning interval of each color image with respect to the Bk image at each position. Also, g(c ~ y),
h(c~y) and i(c~y) are the sub-scanning intervals of each color image with respect to the Bk image at each position. Further, it is assumed that J2 = 2 x J1 and L2 = 2 x L1. Next, the transfer paper on which the pattern image for positional deviation detection is formed is set on the contact glass 109 of the scanner section 101. The direction in which the transfer paper is set may be such that, for example, the leading edge of the transfer paper is on the movement start side of the carriage 104 (the right side in FIG. 1). Then, in the same manner as a normal document reading process, the positional deviation detection pattern image on the transfer paper is read, and the interval between each color pattern image at each position (left end, center, right end) is measured.

[0014] Here, an example of a method for measuring the interval between each image will be described. First, regarding the method of measuring the main scanning interval,
The left end image D' (BK to C) will be explained using FIG. 3 as an example. Figure 3 shows the pattern image D'( B
FIG. 3 is a diagram showing the relationship between CCD 108 and K to C (in which a deviation has occurred from the ideal position). This pattern image is read by the CCD 108 of the scanner section 101. Then, each color image D' ( B K ~ C
) corresponds to which pixel of the CCD 108 is determined. When the position of each color image D'(BK~C) corresponds to the nth (BK~C) pixel of the CCD 108, and if the pixel pitch of the CCD 108 is P, the interval between each color image d'Y, d'M and d'C are determined by the following formula. d'Y = (nY - nB K ) x P, d'M
= (nM - nB K ) x P, d'C = (nC
-nB K )×P Similarly, the central image E′( B
K ~ C), right end image F' (B K ~ C
) can measure the main scanning interval.

Next, a method for measuring the sub-scanning interval will be explained using FIG. 4, taking the image G' (B K -C) at the left end as an example. Figure 4 shows the pattern image G'( B
FIG. 3 is a diagram showing the relationship between CCD 108 and K to C (in which a deviation has occurred from the ideal position). This pattern image is read by the CCD 108 of the scanner section 101. Then, each color image G'(BK ~C
) to measure the reading timing. Image G′(
The measurement timing of BK ~ C) is T(
BK to C), when the moving speed of the carriage 104 is v, the intervals between the images of each color are g'Y, g'M, g
'C is determined by the following formula. g'Y = (TY - TB K ) x v, g'M
= (TM - TB K ) x v, g'C = (TC
−TB K )×v Similarly, the central image H′( B
K ~ C), right end image I' (B K ~ C
) can be used to measure the sub-scanning interval. The distance d' between each image measured by the method described above (Y ~ C)
~i′(Y ~C) and the ideal spacing d(Y
~C) From ~i(Y~C), the positional deviation amount Δd(Y
〜C)〜Δi(Y〜C) is determined. Left end main scanning position deviation; ΔdY = d'Y - dY
ΔdM = d'M - dM
ΔdC = d'C
-dC Left end sub-scanning position deviation; ΔgY = g'
Y −gY ΔgM =g′M −gM
Δ
gC = g'C - gC Center main scanning position deviation;
ΔeY = e'Y -eY ΔeM = e'M
-eM
ΔeC = e'C - eC Central sub-scanning position deviation; ΔhY = h'Y - hY Δ
hM = h'M - hM
ΔhC = h'C - hC
Right edge main scanning position deviation; ΔfY = f'Y - f
Y ΔfM = f'M - fM
ΔfC=
f′C −fC Right end sub-scanning position deviation; ΔiY
=i'Y -iY ΔiM =i'M -iM

ΔiC = i′C −iC From the amount of positional deviation at each position, the form of positional deviation of each color image (positional deviation shown in FIGS. 20 to 25) is determined.

Next, a method for correcting the positional deviation shown in FIGS. 20 to 25 will be explained. Methods for correcting this positional shift include adjusting the mirror angle and adjusting the angle of the photoreceptor 11.
There are two types of methods: mechanical (optical) methods, such as position adjustment (4), and electrical methods, such as adjusting each timing and correcting image data. Here, as a method for correcting each positional deviation, an example of electrical correction will be described. Further, to simplify the explanation, correction of the positional shift of the Y image with respect to the Bk image will be explained.

(1) Method for correcting sub-scanning parallel deviation (deviation shown in FIG. 20) Assume that the Bk image and the Y image have the relationship shown in FIG. At this time, if the conveyance speed of the transfer paper is vB, by advancing the writing timing of the Y image by l/vB, the position of the Y image will be shifted by l1 toward the leading edge of the transfer paper, and this positional shift will be corrected. Can be corrected.

(2) Method for correcting sub-scanning tilt deviation (deviation shown in FIG. 21) As shown in FIG. 6, the line of the Y image with respect to the line of the Bk image is composed of dots indicated by diagonal lines in the figure. Suppose that it is done. Here, this scanning line is referred to as the nth line. The amount of deviation of the line of the Y image with respect to the line of the Bk image is 1 dot at both ends (the direction of deviation is opposite between the ends) (the slope is 2 dots). In order to correct the above condition, first, scan areas A, B, C in the main scanning direction as shown in FIG.
It is virtually divided into three blocks. In the A block, the n-1st scanning line is close to the line of the Bk image,
In the B block, the nth scanning line is close to the line of the Bk image, and in the C block, the n+1 scanning line is close to the line of the Bk image. Therefore, A
In the block, the recording data of the original nth line is used during the recording scan of the n-1th line, in the B block, the recording data of the nth line is used as it is during the recording scan of the nth line, and in the C block, the recording data of the n+1th line is used as is. During line recording scanning, the laser beam is modulated using the original recording data of the n-th line. That is, the recorded data shown in FIG. 8 is rearranged as shown in FIG. 9, and the laser beam is modulated using the rearranged recorded data. The lines of the Y image obtained by correction in this manner are a series of dots marked with diagonal lines in FIG. This recording line (a series of diagonal dots)
The amount of deviation with respect to the Bk image becomes 1/2 dot from the original 1 dot. In the above, we have explained the correction when the slope is two dots, but even if the slope is even larger, the number of blocks to be divided, the division pattern, and the amount of shift in the sub-scanning direction of the recorded data for each block can be changed depending on the slope. By appropriately determining , the amount of deviation of the Bk image from the line can be suppressed to 1/2 dot or less.

(3) Sub-scanning distortion deviation (deviation shown in FIG. 22)
Correction Method As shown in FIG. 10, it is assumed that the lines of the Y image are composed of dots indicated by diagonal lines in the figure, in contrast to the lines of the Bk image. Here, this scanning line is referred to as the nth line. The amount of deviation of the Y image from the line of the Bk image is 1 dot at the center, and 1 dot at both ends in the opposite direction from the center, and the amount of image distortion is 2 dots. In order to correct the above condition, first, the scanning area is virtually divided into five blocks A, B, C, D, and E in the main scanning direction as shown in FIG. In blocks A and E, the n+1st scanning line is close to the line of the Bk image, in blocks B and D, the nth scanning line is close to the line of the Bk image, and in block C, the line of the Bk image is close to the nth scanning line. n-1
The scan lines are close together. Therefore, in the A and E blocks, the original nth line print data is used during the n+1th line print scan, and in the B and D blocks, the nth line print data is used as it is when the nth line print scan is performed, and the C In the block, the laser beam is modulated using the original recording data of the n-th line during recording scanning of the (n-1)th line. In other words, in the n-th line, in the A and E blocks, the original recording data of the n-1th line is used, and the B,
In the D block, the original nth line recording data is
In the C block, the laser beam is modulated using the original recording data of the (n+1)th line. That is, the recorded data shown in FIG. 12 is rearranged as shown in FIG. 13, and the laser beam is modulated by the rearranged recorded data. The lines of the Y image obtained by correction in this manner are a series of dots marked with diagonal lines in FIG. The amount of deviation of this recording line (a series of diagonal dots) from the Bk image becomes 1/2 dot from the original 1 dot. In the above, we have explained the correction when the amount of distortion is 2 dots, but depending on the amount of distortion and the shape of the distortion, the number of blocks to be divided, the dividing pattern, and the amount of shift in the sub-scanning direction of the recorded data for each block should be adjusted appropriately. By determining this, the amount of deviation of the Bk image from the line can be suppressed to 1/2 dot or less.

(4) Correction method for main scanning parallel deviation (deviation shown in FIG. 23) Assume that the Bk image and the Y image have the relationship shown in FIG. 14. At this time, if the scanning speed of the Y laser beam is vL, then
The modulation start timing of the Y laser beam is l2 /vL
This positional shift can be corrected by shifting the position of the Y image by l2 toward the leading edge of the transfer paper.

(5) Correction method for main scanning magnification deviation (deviation shown in FIG. 24) Assume that the Y image is in a state where the magnification is extended as shown in FIG. 15 with respect to the Bk image (l4 = 2× l3, l6 =
2×l5). Then, the frequency of the pixel clock (laser beam modulation clock) when this image is formed is f0
Suppose it was. The Y image is {
(l4+l6)/l4} times, the frequency of this pixel clock should be increased. Therefore, the frequency f1 of the Y pixel clock is f1 = f0
By increasing × {(l4 + l6 )/l4 }, the Y image can be reduced by {l4 / (l4 + l6 )} times, so the magnification of the Y image matches the magnification of the Bk image, and this Positional deviation can be corrected.

(6) Main scanning distortion deviation (deviation shown in FIG. 25)
Correction method Assume that the Y image matches the Bk image at both ends and is shifted by l9 at the center, as shown in FIG.
l8 = 2 x l7). Assume that the frequency of the pixel clock when this image was formed was f0. The Y image is compared to the Bk image, and the left side is {(l7 +l9
)/l7 }, the right side is {(l7 −l
9)/l7} It is in a state where it has shrunk twice. Therefore, the frequency f2 of the Y pixel clock on the left side is set as f2 = f0
×{(l7+l9)/l7}, and the frequency f3 of the Y pixel clock on the right side is set to f3 = f
By lowering the value to 0 × {(l7 - l9 )/l7 }, the Y image on the left becomes {l7 / (l7
+l9)}, and on the right side it becomes {l7/(l
7 - l9 )}, the Y pixels match the Bk image, and this positional shift can be corrected. In the above, the case where the number of divisions in the main scanning direction and the pixel clock frequency are two has been described, but the number of divisions and the number of pixel clock frequencies may be set depending on the state of positional deviation. Furthermore, the frequency of the pixel clock may be continuously changed depending on the position in the main scanning direction.

As described above, each positional shift of the image is
This can be corrected by using the methods (1) to (6) above. Therefore, even if various positional deviations occur in the image, the deviations in the entire image can be corrected by appropriately combining the methods (1) to (6) above depending on the state of the positional deviation. be able to.

According to the invention described in claims 1 to 8, the amount of positional deviation of the output image is detected by the original reading means, and the image forming position of each color is corrected according to the amount of positional deviation. Therefore, even if an image positional shift occurs due to changes over time, this positional shift can be corrected, and high-quality color prints can always be obtained. Further, according to the ninth aspect of the present invention, the document on which the pattern image is formed can be automatically set on the contact glass, resulting in excellent operability.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a digital color copying machine according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a pattern for positional deviation detection.

FIG. 3 is an explanatory diagram of a method for measuring main scanning intervals.

FIG. 4 is an explanatory diagram of a method for measuring sub-scanning intervals.

FIG. 5 is an explanatory diagram showing sub-scanning parallel deviation.

FIG. 6 is an explanatory diagram of the content of correction of sub-scanning tilt deviation.

FIG. 7 is an explanatory diagram of the content of correction of sub-scanning tilt deviation.

FIG. 8 is an explanatory diagram of the content of correction of sub-scanning tilt shift.

FIG. 9 is an explanatory diagram of the content of correction of sub-scanning tilt deviation.

FIG. 10 is an explanatory diagram of the content of correction of sub-scanning distortion deviation.

FIG. 11 is an explanatory diagram of the content of correction of sub-scanning distortion deviation.

FIG. 12 is an explanatory diagram of the content of correction of sub-scanning distortion deviation.

FIG. 13 is an explanatory diagram of the content of correction of sub-scanning distortion deviation.

FIG. 14 is an explanatory diagram showing main scanning parallel deviation.

FIG. 15 is an explanatory diagram showing main scanning magnification deviation.

FIG. 16 is an explanatory diagram showing main scanning distortion deviation.

FIG. 17 is a configuration diagram of a conventional digital color copying machine.

FIG. 18 is a perspective view of a laser beam scanning device.

FIG. 19 is a longitudinal cross-sectional view of the laser beam scanning device.

FIG. 20 is a simplified diagram showing sub-scanning parallel deviation.

FIG. 21 is a simplified diagram showing sub-scanning tilt deviation.

FIG. 22 is a simplified diagram showing sub-scanning distortion deviation.

FIG. 23 is a simplified diagram showing main scanning parallel deviation.

FIG. 24 is a simplified diagram showing main scanning magnification deviation.

FIG. 25 is a simplified diagram showing main scanning distortion deviation.

[Explanation of symbols]

101 Scanner section (original reading means) 102 Image processing section 103 Printer section (color image forming means) 141
Switching claws 142, 143 Conveyance roller

Claims (9)

[Claims] Claim 1: A document reading unit that reads a document on a document table; an image processing unit that processes a signal from the document reading device into a plurality of different color image recording signals; and a plurality of different color image recording signals based on the image recording signal. In a digital color copying machine equipped with a color image forming means that forms and superimposes color images on the same transfer paper to obtain a single color image, positional deviation between each color image is detected and this positional deviation is corrected. 1. A digital color copying machine characterized by controlling the formation of a pattern image for positional deviation detection on a transfer sheet, which is read by a document reading means. 2. A digital color copying machine according to claim 1, wherein the positional deviation is corrected independently for each of the various deviation patterns of the pattern image. 3. The digital color copying machine according to claim 1, wherein the digital color copying machine corrects sub-scanning parallel deviation of the pattern image. 4. The digital color copying machine according to claim 1, wherein the digital color copying machine corrects sub-scanning tilt deviation of the pattern image. 5. The digital color copying machine according to claim 1, wherein sub-scanning distortion deviation of the pattern image is corrected. 6. The digital color copying machine according to claim 1, wherein the digital color copying machine corrects main scanning parallel deviation of the pattern image. 7. The digital color copying machine according to claim 1, wherein a main scanning magnification deviation of the pattern image is corrected. 8. The digital color copying machine according to claim 1, wherein main scanning distortion deviation of the pattern image is corrected. 9. The digital color copying machine according to claim 1, further comprising a conveyance means for conveying the transfer paper on which the pattern image is formed to the document table.