JP4101020B2 - Color misregistration correction method, color misregistration correction apparatus, and image forming apparatus provided with color misregistration correction apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color misregistration correction method, a color misregistration correction apparatus, and such a color misregistration correction apparatus for eliminating a color misregistration and obtaining a good output image in a color image forming apparatus such as a tandem copying machine, a printer, and a FAX. The present invention relates to an image forming apparatus including
[0002]
[Prior art]
Conventionally, in the image forming apparatus as described above, an image read by a reading unit such as a CCD is temporarily stored in an image data storage memory, and this is read out again and printed. At this time, if the LED system is used, an image printer LED writing head for image writing on the photoconductor, and if the laser system is used, an inclination of the image is generated for each color due to the inclination of the exposure means such as a polygon mirror that writes an image on the photoconductor. To do. As long as the inclination is small, such an image tilt is not particularly problematic for monochrome images. However, in an image forming apparatus such as a tandem color copying machine, the image is captured for each color, and the captured image Since a color image is generated by superimposing images, the quality of the obtained color image will be extremely deteriorated if there is a single color or a slight shift. It is necessary to correct accurately.
[0003]
From this point of view, for example, in Patent Document 1, as a method for correcting the inclination of the image, when writing the read image data into the image data storage memory, an operation of a write address corresponding to the amount of inclination is performed. .
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-315545, column 18
[Problems to be solved by the invention]
The correction method described in Patent Document 1 has a configuration in which only the correction corresponding to the line width of the image data storage memory can be performed. Further, in order to improve such a point and cope with a larger amount of inclination, it is necessary to increase the memory amount accordingly, which may lead to a problem of increasing the cost of the image forming apparatus.
In order to solve the above-described problems of the prior art, the present invention provides a method and apparatus capable of eliminating the color shift caused by the inclination of the exposure means and outputting a good image without color shift. In particular, it is an object of the present invention to provide a color misregistration correction method that has high applicability, can cope with a large inclination, and does not cause an increase in cost, or the apparatus or an image forming apparatus including the apparatus. It is what.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides:
An image data storage step of storing image data for each color to be imaged in an image data storage memory;
A tilt detection step for detecting a tilt amount in the main scanning direction of the formed image;
In the color misregistration method including the color misregistration correction step of correcting the tilt based on the detection result of the tilt detection step,
In the color misregistration correction step, when the inclination amount detected by the inclination detection step is less than a predetermined value, the write address to the image data storage memory or the read address from the image data storage memory is manipulated. When the inclination is corrected by the above and the amount of inclination exceeds a predetermined value, both the correction of the write address to the image data storage memory and the correction of the read address from the image data storage memory are performed. The color misregistration correction method is characterized as follows.
As the predetermined value of the tilt amount, the number of lines in the sub-scanning direction of the image data storage memory can be adopted.
When this invention is regarded as a device,
An image data storage memory for storing image data for each color to be imaged;
An inclination detecting means for detecting an inclination amount of the formed image in the main scanning direction;
In the color misregistration correction apparatus provided with the color misregistration correction means for correcting the tilt based on the detection result by the tilt detection means,
The color misregistration correction means manipulates a write address to the image data storage memory or a read address from the image data storage memory when the inclination amount detected by the inclination detection means is less than a predetermined value. When the inclination is corrected by the above and the amount of inclination exceeds a predetermined value, both the correction of the write address to the image data storage memory and the correction of the read address from the image data storage memory are performed. As a color misregistration correction device characterized by
It can be understood as an image forming apparatus characterized by carrying out these methods, or as an image forming apparatus provided with the color misregistration correction device.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the accompanying drawings to help understand the present invention.
FIG. 1 is a schematic configuration diagram of a main part of the tandem type full-color image forming apparatus X according to the embodiment of the present invention.
[0008]
The configuration of a tandem full-color image forming apparatus X (hereinafter referred to as image forming apparatus X) according to an embodiment of the present invention will be described with reference to FIG.
The image forming apparatus X includes a conveyance belt 1 that also serves as a transfer belt stretched between a pair of rollers, and the recording paper 2 is conveyed on the conveyance belt 1 in the direction indicated by the arrow in the figure. It is configured. In addition, a monochrome (black) image forming area B, a cyan image forming area C, a magenta image forming area M, and a yellow image forming area Y are provided on the transport belt 1 in order from the right. A photosensitive drum 5 is disposed on each of the two, and a transfer roller 6 is disposed on the lower side of the conveying belt 1 so as to face the respective photosensitive drums. (Note that the arrangement order of the image forming areas B, C, M, and Y is not particularly limited, and this arrangement can be changed as appropriate. The photosensitive drum has a drum shape as described above. Various forms such as belt-like ones are possible in addition to those
[0009]
In each image forming area, there are a main charger 7, an optical system 8 such as an LED printer head for image exposure and a laser exposure unit, and a color corresponding to each image forming area around the photosensitive drum 5. Developers for toner are arranged in this order. That is, in the monochrome image forming area B, the monochrome developing unit 9B filled with black toner, in the cyan image forming area C, the cyan developing unit 9C filled with cyan toner, and in the magenta image forming area M, filled with magenta toner. In the magenta developing unit 9M and the yellow image forming area Y, a yellow developing unit 9Y filled with yellow toner is provided. Further, between the area where the transfer roller 6 is provided and the main charger 7, a static eliminator (not shown) and a cleaning device 10 are arranged.
The image forming apparatus X includes devices included in a general quadruple tandem image forming apparatus other than that shown in FIG. 1, but the description thereof is omitted here because it is not particularly characteristic. .
[0010]
The image forming cycle in each of the image forming areas will be described by taking the monochrome image forming area B as an example.
First, the photosensitive drum 5 is uniformly charged to a predetermined polarity by the main charger 7 including a corona charger or a contact charging roller. Next, image exposure is performed by light irradiation 8 from an optical system such as an LED (not shown) controlled by the control unit 12, and an electrostatic latent image is formed on the surface of the photosensitive drum 5. This electrostatic latent image is developed by toner transfer by the monochrome developing device 9B filled with black toner, and a toner image is formed on the surface of the photosensitive drum 5.
The toner image formed on the surface of the photosensitive drum 5 in this manner is transferred onto the transfer paper 2 that has been transported on the transport belt 1 in a region facing the transfer roller 6 (transfer region). This transfer is performed by applying a bias voltage having a polarity opposite to that of the toner image to the transfer roller 6. Further, instead of using the transfer roller 6, it is possible to transfer by using a corona charger and charging the back surface of the transfer paper 2 with a polarity opposite to that of the toner image. After the transfer is completed, the static eliminator and the cleaning device 10 (not shown) remove the static electricity on the photosensitive drum 5 and clean the toner remaining on the surface of the drum 5 to perform the next image forming cycle.
[0011]
As described above, in the monochrome image forming area B, a monochrome image made of black toner is formed on the transfer paper 2, and in the same manner, in the cyan image forming area C, cyan made of cyan toner is formed. In the color image and magenta image forming area M, a magenta color image made of magenta toner and a yellow image made of yellow toner are formed in the yellow image forming area Y. That is, when a monochrome image is formed, the above-described image formation cycle is executed only in the monochrome image formation region B, and a monochrome image is formed on the transfer paper 2. When a full-color image is formed, the above-described image forming cycle is executed in each of the image forming regions B, C, M, and Y, and the single color toner images of the respective colors are superimposed to form a full color on the transfer paper 2. An image is formed. The transfer paper 2 on which the image is formed in this manner is discharged from the transport belt 1 and introduced into the fixing device 11 where the image is fixed and discharged.
[0012]
In the present embodiment, in addition to the configuration of the color image forming apparatus X, an image reading unit 13 such as a CCD is provided upstream of the fixing device 11, and signals from these image reading units 13 are This is transmitted to the control unit 12 via the input / output interface 12a of the control unit 12 shown in FIG.
FIG. 2 is a functional block diagram of the control unit 12. The control unit 12 is mainly configured by a CPU. The CPU 12 stores a program for executing a color misregistration correction procedure described below, a ROM 12b for storing an image pattern for detecting an inclination of the image, and the image. An input / output interface 12a to which a signal from the reading means 13 is input and information on the image pattern is output is connected.
Next, the color misregistration correction process executed by the CPU will be described with reference to the accompanying drawings in FIG.
FIG. 3 is a flowchart showing the overall procedure of the color misregistration correction process, FIG. 4 is a flowchart showing the procedure of the color misregistration correction process, and FIG. 5 is a flowchart showing the procedure for determining the inclination correction method.
[0013]
First, an outline of the color misregistration correction processing procedure will be described with reference to FIG.
In the following description, S1, S2,... Indicate processing procedure numbers.
In this embodiment, the power (main switch) of the image forming apparatus X is turned on (S1) , a time until a predetermined fixing condition is satisfied, that is, a warm-up time elapses (S2) , and a predetermined correction timing is set. When it comes (YES in S3) , tilt correction is executed (S4). If correction is executed in S4 or if it is determined in S3 that the correction timing is not reached (NO in S3), the ready state is displayed indicating that preparation for copying is complete (S5) , and the copying process is performed. It is determined whether or not the instructed print key is pressed (S6) , and when the print key is pressed, the printing process is executed (S7).
Detailed processing of the inclination correction in S4 is as shown in FIG.
When the tilt correction process in S4 is started, an image pattern for tilt correction is first generated. The generation of the image pattern may be performed each time, but is performed by reading an image pattern stored in advance in the ROM 12b in the control unit 12, as shown in FIG.
In this embodiment, an image pattern as shown in FIG. As shown in FIG. 15 of Patent Document 1, this pattern has patterns arranged in the main scanning direction at the right end and the left end, respectively. These patterns are formed at predetermined intervals for each of yellow , magenta, cyan, and black colors. However, such an image pattern is not limited to that described in Patent Document 1, and may be a straight line, a broken line, or any other pattern that does not shift in the main operation direction. Since the contents of this image pattern are not directly related to the configuration of the present invention, detailed description is unnecessary.
[0014]
Next, an image corresponding to this pattern is formed as an electrostatic latent image on the photoconductor 5 for each color area, and this is developed into a toner image, then transferred to the conveyor belt 1, and this toner image as the conveyor belt 1 travels. Is detected by the image reading means 13 (S10). When the pattern is detected as described above, the CPU calculates the positions of the left and right patterns in the full width in the main scanning direction for each color (S11), and calculates the inclination amount and the direction of the pattern (S12). ). When the inclination amount and direction of the pattern are calculated, the CPU calculates an inclination correction value and determines a correction method (S13). Details of S13 are shown in FIG. When the inclination correction value and the pattern correction method are determined as described above, the correction value is stored (set) (S14). The correction process performed by the image forming apparatus X using the correction value will be described in detail later.
[0015]
The “determination process of inclination correction value and pattern correction method” in S14 is executed based on the procedure of FIG.
That is, the CPU executes a program for comparing the amount of inclination calculated in S12 of FIG. 4 with a predetermined value (S20). The predetermined value to be compared here is a deviation amount per predetermined width in the main scanning direction. Normally, the number of lines in the image data storage memory is set to a predetermined value. For example, if the number of lines in the image data storage memory is 5, the predetermined number is 5.
In S20, NO, that is, for example, if the inclination amount (deviation amount) of the read pattern is 5 or less in the number of lines in the image data storage memory, the writing method to the image data storage memory is operated as shown in S21. Then, a correction method is selected to determine whether to adopt a correction method for correcting the above-mentioned deviation or to adopt a correction method for correcting the above-mentioned deviation by operating a method of reading from the image data storage memory. This selection may be performed by the operator, or may be automatically selected by the image forming apparatus X. A correction method by operating the writing process procedure to the image data storage memory and a correction method by operating the reading procedure from the image data storage memory will be described later.
If YES in S20, that is, if the amount of inclination (deviation amount) exceeds 5, for example, as shown in S22, a correction method for correcting the deviation by manipulating the method of writing to the image data storage memory. And a correction method for performing both of the correction methods for correcting the deviation by manipulating the method of reading from the image data storage memory. The correction method for performing both the correction method by manipulating the write processing procedure to the image data storage memory and the correction method by manipulating the reading procedure from the image data storage memory will be described later.
[0016]
Next, the correction method selected in S21 or S22 will be described with reference to the attached drawings in FIG.
As the case of the correction method, in S20, the case of S21 depends on whether the amount of inclination detected in S12 is larger than the number of lines in the image data storage memory shown in FIG. 6B (5 in this example). And S22 are as described above. In the case shown in FIG. 6, since the amount of inclination detected in S12 is 5, the determination in S20 is NO and the correction method in S21 is selected. In FIG. 6, the image data storage memory is displayed in S21. The procedure for performing tilt correction at the stage of the writing operation is shown.
In this case, (a) is image data before writing to the image data storage memory. The image data of (a) is denoted by reference numerals 0 to 8 for easy understanding of the image address. The same code is assigned to addresses on the same line. The width of the main operation direction of one data group (indicated by a square frame) displayed at the same address is
Width = main operation width / tilt amount (number of tilt lines).
In the tilt correction, the data at the rightmost address (indicated by 0) is not shifted because it is the origin of the tilt, and is written at the rightmost address of the image data storage memory shown in (b). Since the data at the second address from the right has an inclination of 5 lines in the full width, it can be seen that the data is shifted by 1 line. Therefore, the data at the downstream side by 1 line in the reading direction (indicated by 1) Is the data to be output originally, the reading position is shifted by one line and written to the image data storage memory. Similarly, the data at the fifth address from the right is shifted by four lines and written to the image data storage memory. (C) shows the state of the image data storage memory in which the data whose inclination is corrected in this way is written. Therefore, the data in the front row of the image data storage memory that has been written are arranged as 0, 1, 2, 3, 4, and so on.
In this example, the inclination of the image is corrected at the stage of writing to the image data storage memory as described above. Therefore, in the actual image forming procedure, the data in the image data storage memory having the inclination corrected is simply sequentially. It is only necessary to read and form a latent image on the photosensitive member 5. Since the inclination correction as described above is executed in all the color regions of the image forming apparatus X shown in FIG. 1, the color shift of the image formed image is completely eliminated.
[0017]
FIG. 7 shows a procedure for performing tilt correction at the time of reading from the image data storage memory in S21.
In this case, (a) shows an empty image data storage memory that has not yet been written. Similar to the case of FIG. 6, the inclination is 5 lines. (B) in the drawing shows the image data storage memory after writing. The width of the data group at the same address in the image data storage memory is calculated by the main operation width / tilt amount as in the case of FIG.
Since correction is not performed at this stage, the data as it is tilted is written to each address of the image data storage memory. Then, the inclination correction is performed when the write data to the image data storage memory of (b) is read out, and the data at the corrected address is sequentially read out. (C) shows the data of the first line read with the correction process. Naturally, the corrected data are arranged like 0, 1, 2, 3, and 4. The electrostatic latent image forming process based on the read data is the same as in the case of FIG.
Next, the processing when the amount of inclination is larger than the predetermined value, that is, the number of lines of the image data storage memory in S20 (YES in S20) will be described with reference to FIG. In this case, it is assumed that the number of lines in the image data storage memory ((b) in the figure) is 5, and an inclination of 8 lines is generated. In this case, partial correction ((a) → (b)) is performed when writing to the image data storage memory, and the remaining inclination is corrected when reading from the image data storage memory ((c) → (d)). To do. In this case, the width of the data at the same address when writing to the image data storage memory = main operation width ÷ tilt amount is calculated, but width × (main operation width ÷ tilt amount) ÷ (tilt amount−memory amount + 1). At the position, the write address is not switched. As a result, the data as shown in (a) is corrected stepwise and arranged in the one-line image data storage memory of the image data storage memory as shown in (b).
Next, the data shifted with respect to the data stored in the image data storage memory at the position where switching was not performed at the time of writing to the image data storage memory is read. As a result, as shown in (d), the data after reading is arranged with addresses 0, 1, 2, 3, 4, 5, 6, and 7 on one line, and complete correction is performed. It is. The electrostatic latent image forming process related to the data after tilt correction is the same as that described with reference to FIGS.
[0018]
【The invention's effect】
As described above, the present invention
An image data storage step of storing image data for each color to be imaged in an image data storage memory;
A tilt detection step for detecting a tilt amount in the main scanning direction of the formed image;
In the color misregistration method including the color misregistration correction step of correcting the tilt based on the detection result of the tilt detection step,
In the color misregistration correction process, when the tilt amount detected by the tilt detection process is less than a predetermined value, the write address to the image data storage memory or the read address from the image data storage memory is manipulated. When the inclination is corrected by the above and the amount of inclination exceeds a predetermined value, both correction of the write address to the image data storage memory and correction of the read address from the image data storage memory are performed. Therefore, even when the generated image shift is larger than the number of lines in the image data storage memory, the correct color shift can be corrected. Further, the cost for such correction processing is almost the same as the conventional one, and does not cause an increase in cost.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating an example of an image forming apparatus.
FIG. 2 is a block diagram showing a structure of a control unit.
FIG. 3 is a flowchart showing an overall procedure of color misregistration correction processing.
FIG. 4 is a flowchart illustrating a procedure of color misregistration correction processing.
FIG. 5 is a flowchart showing a procedure for determining an inclination correction method;
FIG. 6 is a conceptual diagram showing a procedure when tilt correction is performed.
FIG. 7 is a conceptual diagram illustrating a procedure when tilt correction is performed by a reading operation from an image data storage memory.
FIG. 8 is a conceptual diagram illustrating a procedure when tilt correction is performed by a write operation to the image data storage memory and a read operation from the image data storage memory.
[Explanation of symbols]
2 ... paper 5 ... photoconductor 6 ... transfer roller 7 ... charger 13 ... image reading means

Claims (5)

An image data storage step of storing image data for each color to be imaged in an image data storage memory;
A tilt detection step for detecting a tilt amount in the main scanning direction of the formed image;
In a color misregistration method including a color misregistration correction step of correcting the tilt based on a detection result of the tilt detection step
In the color misregistration correction step, when the inclination amount detected by the inclination detection step is less than a predetermined value, the write address to the image data storage memory or the read address from the image data storage memory is manipulated. When the inclination is corrected by the above and the amount of inclination exceeds a predetermined value, both the correction of the write address to the image data storage memory and the correction of the read address from the image data storage memory are performed. Color misregistration correction method characterized by the above.   2. The color misregistration correction method according to claim 1, wherein the predetermined value of the amount of inclination is the number of lines in the sub-scanning direction of the image data storage memory. An image data storage memory for storing image data for each color to be imaged;
An inclination detecting means for detecting an inclination amount of the formed image in the main scanning direction;
In the color misregistration correction apparatus including a color misregistration correction unit that corrects the tilt based on a detection result by the tilt detection unit, the color misregistration correction unit has an inclination amount detected by the tilt detection unit equal to or less than a predetermined value. In this case, the inclination is corrected by manipulating a write address to the image data storage memory or a read address from the image data storage memory, and if the inclination amount exceeds a predetermined value, the image data storage memory A color misregistration correction apparatus for correcting both a write address to the image and a read address from the image data storage memory.   An image forming apparatus capable of executing the color misregistration correction method according to claim 1.   An image forming apparatus comprising the color misregistration correction apparatus according to claim 3.

Images