JP4745522B2 - Color image forming apparatus and color misregistration correction method used therefor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tandem color image forming apparatus.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as color image forming apparatuses such as copying machines and printers, a photosensitive unit including a photosensitive member is provided for each color, and a toner pattern is formed in this unit and transferred in multiple stages onto a transfer sheet on a transfer belt. A device that employs a tandem method for acquiring an image is known. In a color image forming apparatus employing this tandem method, there is a risk of deviation between the color patterns when the toner patterns formed by the photoconductor units are superimposed. To ensure a certain quality, the toner pattern Must be superimposed with high accuracy.
[0003]
In order to cope with this, conventionally, the toner pattern formed on the intermediate transfer belt is detected, the amount of deviation between the detected reference color pattern and the pattern of the other color is calculated, and the calculated amount of deviation is obtained. Based on this, a method for correcting the printing position of an image is known.
[0004]
[Problems to be solved by the invention]
By the way, in the conventional color image forming apparatus, when the specific pattern is matched with the reference color, the shape is greatly deformed, so that the position is not corrected and printing is performed. However, since the printing position of the specific pattern is not corrected, the printing position may be different from the position where printing should be originally performed.
Conventionally, as another method for correcting the print position of an image, a method of performing position correction after overlaying a specific pattern on the image to be printed is also known. Therefore, there is a possibility that the print shape of the specific pattern changes.
[0005]
The present invention has been made in view of the above technical problem, and a color image forming apparatus capable of correcting a printing position of a specific pattern and printing it at an accurate position on a print medium, and a color misregistration correction method used therefor The purpose is to provide.
[0006]
[Means for Solving the Problems]
The invention according to claim 1 of the present application includes a photoconductor that forms a toner pattern for each color constituting a color image, superimposes each toner pattern, and superimposes a specific pattern as a predetermined pattern on the printed image. In the color image forming apparatus for forming a color image, a sensor for detecting each color toner pattern transferred to the transfer body is disposed opposite to the transfer body to which the toner pattern formed by the photoconductor is transferred. A first correction unit that calculates a deviation amount of a toner pattern of another color with respect to a reference color toner pattern from each color toner pattern detected by the sensor and corrects a printed image based on the deviation amount; The color toner patterns detected by the sensor are superimposed on the image to be printed and printed on the print medium. Based on the color of the toner pattern corresponding to the constituent colors of the specific pattern is a predetermined pattern, determined at least one of the bow and skew between a plurality of pattern elements constituting the color toner pattern corresponding to the constituent colors, Based on at least one of the obtained bow and skew, a relative positional deviation amount between a plurality of pattern elements constituting a toner pattern of a color corresponding to the constituent color is calculated , and based on the relative positional deviation amount. Then, the second correction unit that corrects the specific pattern and the specific pattern after the relative positional shift amount is corrected by the second correction unit, the shift amount is corrected by the first correction unit. and superposition to the image to be the print after is obtained is characterized in that a, superimposing means for forming the color image.
[0008]
Furthermore, the invention according to claim 2 of the present application includes a photoconductor that forms a toner pattern for each color constituting a color image, and superimposes each toner pattern to print a specific pattern that is a predetermined pattern. In a color misregistration correction method used in a color image forming apparatus that forms a color image superimposed on a sensor, a sensor disposed opposite to a transfer body to which a toner pattern formed by the photoconductor is transferred is attached to the transfer body. The step of detecting each color toner pattern transferred, and the first correction means calculate the amount of deviation of the toner pattern of the other color with respect to the toner pattern of the reference color from each color toner pattern detected by the sensor. And a step of correcting the image to be printed, and the second correcting means prints an image to be printed out of the toner patterns detected by the sensor. Based on the color of the toner pattern corresponding to the constituent colors of the specific pattern is a predetermined pattern that is color printing and are aligned with each other on the printing medium, a plurality of constituting a color toner pattern corresponding to the constituent colors And determining a relative position between the plurality of pattern elements constituting the toner pattern of the color corresponding to the constituent color based on at least one of the calculated bow and skew. A step of calculating a deviation amount and correcting the specific pattern based on the relative positional deviation amount and a superimposing unit after the relative positional deviation amount is corrected by the second correction unit. the specific pattern, the scan for forming the color image by superposition on the image to be the print after the shift amount is corrected by said first correction means It is obtained by said to have Tsu and up, the.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In this embodiment, an example in which the present invention is applied to a copying machine will be described. However, the present invention is not limited to this and may be applied to a printer. FIG. 1 is a block diagram showing a basic configuration of a copying machine according to an embodiment of the present invention. The copying machine 1 basically includes an image scanning unit 4 that reads an original using an optical system and acquires image data, and an image data processing unit that performs various processes including character recognition processing on the image data. 5 and a printing unit 6 that executes printing based on the image data. These components include a CPU 11 that controls various components incorporated in the copying machine 1 via a data bus 15, a ROM 12 that stores a control program for the CPU 11, and the CPU 11 for controlling each component. Are connected to a RAM 13 for temporarily storing programs to be executed and data.
[0010]
In the copying machine 1, first, in the image scanning unit 4, a document on a document table is optically read by a CCD (not shown) and subjected to photoelectric conversion. As the CCD, a three-line linear CCD corresponding to each color component of R (red), G (green), and B (blue) is used. When irradiating light on a document on a document table, this linear CCD can acquire R, G, and B color light from the reflected light in one scan, and each color light is converted into an electrical signal (analog image data). ). Analog image data acquired by the image scanning unit 4 is input to the image data processing unit 5 and processed so as to have an output format suitable for the printing unit 6. The printing unit 6 creates a print print by forming an image on a print medium such as paper based on the image data output from the image data processing unit 5. The operation of each component during this time is executed by the program recorded in the ROM 12 being stored in the RAM 13 and then sequentially read out by the CPU 12.
[0011]
FIG. 2 is a diagram schematically showing the structure of the printing unit 6 in the copying machine 1. The printing unit 6 includes photoreceptor units 7C, 7M, 7Y, and 7K for each color of C (cyan), M (magenta), Y (yellow), and K (black). Each of the photosensitive units 7C, 7M, 7Y, and 7K uniformly charges the photosensitive drums 16C, 16M, 16Y, and 16K that form and hold the toner pattern, and the surfaces of the photosensitive drums 16C, 16M, 16Y, and 16K. Charging units 17C, 17M, 17Y, and 17K to be exposed, exposure LEDs 18C, 18M, 18Y, and 18K that are exposed by irradiating the charged drum surface with light based on job data to be printed to neutralize the charged portions, and developing Units 19C, 19M, 19Y, and 19K, and cleaners 20C, 20M, 20Y, and 20K. The photosensitive units 7C, 7M, 7Y, and 7K have the photosensitive drums 16C, 16M, 16Y, and 16K in one direction. They are arranged in parallel so as to constitute a transfer belt conveyance line.
[0012]
Facing the photosensitive units 7C, 7M, 7Y, and 7K, more strictly, facing the upper ends of the photosensitive drums 16C, 16M, 16Y, and 16K, transfer portions 21C, 21M, 21Y, and 21K are disposed, respectively. Has been. A space through which the transfer belt 23 can pass is defined between the photosensitive drums 16C, 16M, 16Y, and 16K and the transfer portions 21C, 21M, 21Y, and 21K. It is held by the roller members 24A, 24B, 24C, and 24D so as to be driven between them (in the direction of the arrow in FIG. 2). Here, the transfer belt 23 is held by roller members 24A, 24B, 24C, and 24D so as to form a substantially triangular driving path in a side view.
[0013]
While the transfer belt 23 passes between each photosensitive drum and the transfer portion, the surface of the transfer belt 23 facing the photosensitive drums 16C, 16M, 16Y, and 16K is formed and held on the photosensitive drums 16C, 16M, 16Y, and 16K. Each color pattern is sequentially transferred. Then, the pattern formed by combining these color patterns is subsequently transferred and fixed to a printing medium such as paper.
[0014]
In this embodiment, a pattern detection sensor (detecting a color misregistration detection toner pattern on the transfer belt 23 facing the drive path of the transfer belt 23 after passing between the photosensitive drum and the transfer belt ( (Hereinafter referred to as a resist sensor) 25 is provided. Here, three registration sensors S1, S2, and S3 are provided along the width direction (main scanning direction) of the transfer belt 23.
[0015]
FIG. 3 is a diagram conceptually showing a color misregistration detection toner pattern detected by the registration sensors S1, S2, and S3. The registration sensors S1, S2, and S3 detect toner patterns formed on the transfer belt 23, respectively. Then, the detection values for the predetermined points (R1, R2, and R3 in the figure) of the toner pattern by the registration sensors S1, S2, and S3 are evaluated, and based on the detection values, cyan for black (K) that is the reference color. The deviation amounts of (C), magenta (M), and yellow (Y) are calculated and corrected by quadratic curve approximation. In this correction method, correction coefficient data is stored in the RAM 13, and drawing timing control is performed in accordance with the stored data.
[0016]
In FIGS. 4A and 4B, the manner in which the toner pattern is detected by each of the registration sensors S1, S2, and S3 is a concept for detecting a color toner pattern and detecting a black toner pattern, respectively. Indicated. The registration sensors S1, S2, and S3 basically include an infrared LED 31 that generates infrared rays applied to the color and black toner patterns T1 and T2 formed on the transfer belt 23, and the infrared LED 31 and the toner pattern T. A polarizing filter 32, a polarization separating prism 33 for polarizing and separating reflected light from the toner patterns T1 and T2, a black photodiode 34 disposed on an extension of the optical axis of the reflected light, and reflected light The color photodiode 35 is disposed so as to be orthogonal to the optical axis of the color.
[0017]
First, as shown in FIG. 4A, when the color toner pattern T1 is detected using the registration sensors S1, S2, and S3 having such a configuration, the infrared light is almost entirely in the toner pattern T1. Reflected. Since the reflected light has a light amplitude that is different from that of the irradiated light, the polarization separation prism 33 separates light having an amplitude different from that of the irradiated light. This light is detected by the color photodiode 35, and the adhesion amount of the color toner on the transfer belt 23 can be calculated based on the detected light amount. There is a relationship as shown in FIG. 5A between the amount of light detected by the color photodiode 35 and the amount of color toner deposited on the transfer belt 23.
[0018]
On the other hand, when the black toner pattern T2 is detected using the registration sensors S1, S2, and S3 as shown in FIG. 4B, the infrared light from the infrared LED 31 is almost in the black toner pattern T2. Absorbed. Therefore, the reflection of infrared light from the black toner pattern T2 is very small. Since the light reflected from the transfer belt 23 has the same amplitude as the irradiation light, the polarization separation prism 33 separates the light having the same amplitude as the irradiation light. This light is detected by the black photodiode 34, and the adhesion amount of the black toner on the transfer belt 23 can be calculated based on the detected light amount. There is a relationship as shown in FIG. 5B between the amount of light detected by the black photodiode 34 and the amount of black toner deposited on the transfer belt 23.
[0019]
In this embodiment, the shift amount of each color with respect to black is calculated in order to match the print position with black, which is the reference color, and the print position shift amount (for example, bow and skew) for each color is calculated using the same toner pattern. Detected and calculated as a specific pattern color misregistration amount. In order to perform such processing, a specific pattern is printed in the image data processing unit 5 (see FIG. 1) based on the results detected by the registration sensors S1, S2, and S3 during the printing process in the printing unit 6. Correction means for correcting the position is incorporated. FIG. 6 is a block diagram showing a configuration of the image data processing unit 5 in which the correction unit is incorporated.
[0020]
The image data processing unit 5 uses a data compression unit 41 that compresses input data, a RAM controller 42 that controls writing / reading of the RAM 11, and a detection value acquired by the registration sensor 23 to generate a reference color. On the other hand, the color misregistration correction unit 43 that corrects the color misregistration amount of each color, the data decompression unit 44 that decompresses the compressed data, and the image data so that the gradation is expressed by the size of a point or the thickness of a line. A screen generation unit 45 to be processed, an analog / digital conversion unit (indicated as A / D in the figure) 46 for analog / digital conversion of the detection value acquired by the registration sensor 23, and a deviation in print position for each color A specific pattern position correcting unit 47 that corrects the amount and a specific pattern superimposing unit 48 that superimposes the specific patterns of the respective colors are provided.
The color misregistration correction unit 43 and the specific pattern position correction unit 47 correspond to the “first correction unit” and the “second correction unit” in the claims, respectively.
[0021]
In the image data processing unit 5 having such a configuration, the color misregistration correction unit 43 calculates the misregistration amount of each color with respect to black as the reference color, and based on the misregistration amount, corrects the print position to match black. It is. In parallel with this, the specific pattern position correction unit 47 calculates a deviation amount of the toner color used in the specific pattern, and corrects the printing position of the specific pattern based on the deviation amount. In this embodiment, the size of the bow (bow-shaped distortion) and skew (tilt) of the image is calculated as the amount of deviation of the toner color used in the specific pattern.
[0022]
As a result, even when the reference color black is misaligned with respect to the print medium such as paper, the position is corrected based on the amount of misalignment of the specific pattern color. Thus, it is possible to accurately print the specific pattern without the occurrence of.
[0023]
With reference to FIGS. 7A to 7C, the normal image on the paper (K, C, M, Y color) after the print position correction according to the prior art and the present invention and the specific pattern on the paper (here, the Y color are taken up). ). First, FIG. 7A shows a normal image (K, C, M, Y color) on the paper before the printing position correction and a specific pattern (Y color) on the paper. For a normal image, the other colors individually have a shift amount with respect to the reference color. On the other hand, for the specific pattern, the toner color has a deviation amount. The black points R1, R2, and R3 in the figure correspond to the predetermined points R1, R2, and R3 of the toner pattern detected by the registration sensors S1, S2, and S3 shown in FIG. In this case, the points R1, R2, and R3 are not aligned on the same straight line because the toner color has a deviation amount.
[0024]
FIG. 7B shows a normal image (K, C, M, Y color) on the paper after the printing position correction according to the prior art and a specific pattern (Y color) on the paper. For a normal image, the print position is corrected in accordance with the reference color black. On the other hand, for the specific pattern, the toner color has a deviation amount as before the print position correction.
[0025]
Further, FIG. 7C shows a normal image (K, C, M, Y color) on the paper after the printing position correction according to the present invention and a specific pattern (Y color) on the paper. For a normal image, the print position is corrected in accordance with the reference color black. On the other hand, for the specific pattern, the toner color is corrected for the printing position. In this case, the points R1, R2, and R3 are arranged on a horizontal straight line.
[0026]
In this way, by performing position correction also for the printing process of the specific pattern, even when the reference color is deformed with respect to the print medium, the specific pattern is printed at an accurate position on the print medium. Can do.
[0027]
Note that the present invention is not limited to the illustrated embodiments, and it goes without saying that various improvements and design changes are possible without departing from the scope of the present invention.
[0028]
【The invention's effect】
As is apparent from the above description, according to the invention of claim 1 of the present application, a photoconductor that forms a toner pattern for each color constituting a color image is provided, and the toner patterns are superposed to form a predetermined pattern. In a color image forming apparatus that forms a color image by superimposing a specific pattern on an image to be printed, the toner pattern formed by the photoconductor is disposed to face a transfer body to which the toner pattern is transferred, and is placed on the transfer body. The amount of deviation of the toner pattern of the other color with respect to the toner pattern of the reference color is calculated from the sensor for detecting the transferred toner pattern of each color and the color toner pattern detected by the sensor, and printing is performed based on the amount of deviation. A first correction unit that corrects an image to be printed, and a color toner pattern detected by the sensor that is superimposed on the image to be printed. Based on the color of the toner pattern corresponding to the constituent colors of the specific pattern is a predetermined pattern to be printed in color on a print medium is a plurality of pattern elements constituting the color toner pattern corresponding to the constituent colors Determining at least one of the bow and skew between them, and calculating a relative positional shift amount between the plurality of pattern elements constituting the toner pattern of the color corresponding to the constituent color based on at least one of the calculated bow and skew. A second correction unit that calculates and corrects the specific pattern based on the relative displacement amount, and the specific pattern after the relative displacement amount is corrected by the second correction unit. and a, superimposing means for forming the color image by superposition on the image shift amount is the printing corrected by said first correction means Therefore, even when the reference color is misaligned with respect to the print medium such as paper, position correction is performed on the specific pattern based on the relative misalignment amount of the specific pattern color. On the other hand, it is possible to accurately print a specific pattern without causing a positional shift.
[0030]
Further, according to the invention of claim 2 of the present application, a photoconductor that forms a toner pattern for each color constituting a color image is provided, and each toner pattern is overlaid , and a specific pattern that is a predetermined pattern is printed. In a color misregistration correction method used in a color image forming apparatus that forms a color image superimposed on an image to be transferred, a sensor disposed facing a transfer body to which a toner pattern formed by the photoconductor is transferred includes The step of detecting each color toner pattern transferred to the body, and the first correction means calculate a deviation amount of the toner pattern of the other color with respect to the reference color toner pattern from each color toner pattern detected by the sensor, and the deviation A step of correcting an image to be printed based on the amount; and a second correction unit that prints out of the toner patterns detected by the sensor. That on the basis of superimposed on image color toner pattern corresponding to the constituent colors of the specific pattern is a predetermined pattern to be printed in color on a print medium, constituting a color toner pattern corresponding to the constituent colors Determining at least one of a bow and a skew between the plurality of pattern elements , and based on at least one of the calculated bow and the skew, a relative relationship between the plurality of pattern elements constituting a toner pattern of a color corresponding to the constituent color A step of correcting the specific pattern based on the relative amount of misalignment, and a superimposing unit correcting the relative amount of misregistration by the second correcting unit. the specific pattern after, and superposition on the image shift amount by the first correction means is the printing after correction form said color image Therefore, even when the reference color is misaligned with respect to the print medium such as paper, the position of the specific pattern is corrected based on the relative misalignment amount of the specific pattern color. Thus, the specific pattern can be accurately printed without causing a positional shift with respect to the print medium.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a basic configuration of a color image forming apparatus according to an embodiment of the present invention.
FIG. 2 is an enlarged view illustrating a printing unit in the color image forming apparatus.
FIG. 3 is a diagram conceptually showing a color misregistration detection toner pattern detected by a registration sensor.
FIG. 4A is a diagram illustrating a state in which a toner pattern is detected by each registration sensor in a case where a color toner pattern is detected.
FIG. 6B is a diagram illustrating how a toner pattern is detected by each registration sensor in a case where a black toner pattern is detected.
FIG. 5A is a diagram showing the relationship between the amount of light detected by a color photodiode and the amount of color toner deposited on a transfer belt.
FIG. 6B is a diagram illustrating a relationship between the amount of light detected by the black photodiode and the amount of black toner attached on the transfer belt.
FIG. 6 is a block diagram showing a configuration of an image data processing unit in which correction means for correcting a printing position is incorporated based on a toner pattern detection result in the printing unit.
7A is a diagram showing a normal image (K, C, M, Y color) on a sheet before printing position correction and a specific pattern (Y color) on the sheet. FIG.
(B) It is a figure showing the normal pattern (K, C, M, Y color) on the paper after print position correction by a prior art, and the specific pattern (Y color) on a paper.
(C) is a diagram showing a normal image (K, C, M, Y color) on the paper after the printing position correction according to the present invention and a specific pattern (Y color) on the paper.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Copy machine 4 ... Image scanning part 5 ... Image data processing part 6 ... Printing part 7C, 7M, 7Y, 7K ... Photosensitive unit 16C, 16M, 16Y, 16K ... Photosensitive drum 17C, 17M, 17Y, 17K ... Charging part 18C , 18M, 18Y, 18K ... Exposure LED
19C, 19M, 19Y, 19K ... developing sections 20C, 20M, 20Y, 20K ... cleaners 21C, 21M, 21Y, 21K ... transfer section 23 ... transfer belt 31 ... infrared LED
32 ... Polarizing filter 33 ... Polarization separation prism 34 ... Black photodiode 35 ... Color photodiode 43 ... Color color misregistration correction unit 47 ... Specific pattern position correction unit 48 ... Specific pattern superimposition unit S1, S2, S3 ... Registration sensor

Claims (2)

Color image formation that includes a photoreceptor that forms a toner pattern for each color constituting a color image, superimposes each toner pattern, and superimposes a specific pattern, which is a predetermined pattern, on the printed image. In the device
A sensor that is arranged to face a transfer body to which a toner pattern formed by the photoconductor is transferred, and that detects each color toner pattern transferred to the transfer body;
A first correction unit that calculates a deviation amount of a toner pattern of another color with respect to a toner pattern of a reference color from each color toner pattern detected by the sensor, and corrects an image to be printed based on the deviation amount;
Among the respective color toner pattern detected by the sensor, the color of the toner pattern corresponding to the constituent colors of the specific pattern is a predetermined pattern are superimposed on the image to be printed is printed in color on the printing medium Based on at least one of a bow and a skew between a plurality of pattern elements constituting a toner pattern of a color corresponding to the constituent color, and corresponding to the constituent color based on at least one of the obtained bow and the skew. A second correction unit that calculates a relative positional deviation amount between a plurality of pattern elements constituting the color toner pattern and corrects the specific pattern based on the relative positional deviation amount;
The specific pattern after the relative positional deviation amount is corrected by the second correction means, by superposition on the image shift amount by the first correction means is the printing after correction A color image forming apparatus comprising: a superimposing unit that forms the color image. Color image formation that includes a photoreceptor that forms a toner pattern for each color constituting a color image, superimposes each toner pattern, and superimposes a specific pattern, which is a predetermined pattern, on the printed image. In the color misregistration correction method used in the apparatus,
A step of detecting a toner pattern of each color transferred to the transfer body by a sensor disposed opposite to the transfer body to which the toner pattern formed by the photoconductor is transferred;
A first correction unit calculating a deviation amount of a toner pattern of another color with respect to a toner pattern of a reference color from each color toner pattern detected by the sensor, and correcting a printed image based on the deviation amount; ,
Color second correction means, corresponding to one of the toner pattern in which the sensor detects, component color of the specific pattern is a predetermined pattern are superimposed on the image to be printed is printed in color on the printing medium Based on the toner pattern, at least one of a bow and a skew between a plurality of pattern elements constituting a toner pattern of a color corresponding to the constituent color is obtained, and based on at least one of the obtained bow and the skew, the configuration Calculating a relative positional deviation amount between a plurality of pattern elements constituting a toner pattern of a color corresponding to the color, and correcting the specific pattern based on the relative positional deviation amount;
Superimposing means, the specific pattern after the relative positional deviation amount is corrected by the second correction means, the image shift amount by the first correction means is the printing after correction color shift correction method by superposition, characterized in that it has the steps of: forming the color image.

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