JPH086345A - Correcting method for color registration deviation of multiple image forming device - Google Patents

Abstract

PURPOSE:To correct the color registration of the actually obtained image with high accuracy regardless of the number of sheets and invariably obtain the optimum image by adding the drift quantity of the color registration deviation factor caused by the actual image discharge action to the color registration deviation quantity measured and calculated on a transfer belt. CONSTITUTION:A controller 1 controls the image output and image sampling. For the control of image sampling correction, the sample start point and sample width of a sampling controller 2 are set, a registration deviation measuring pattern is repeatedly generated, and sampling data or arithmetic processing data are integrated to obtain the pattern position. The registration deviation is detected, an image controller 7 and an image output section 8 are controlled, and skew drift correction, magnifying power correction, main scanning direction drift correction, and auxiliary scanning direction drift correction are made.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiple image forming apparatus for obtaining a color image by successively superposing and transferring images formed by a plurality of image output means onto one recording medium. The present invention relates to a method for correcting a color registration deviation in which registrations between means are matched.

[0002]

2. Description of the Related Art In recent years, colorization of copiers, printers, fax machines, etc., which handle documents has progressed rapidly, and documents in offices have been colorized. Devices that handle these color documents tend to be further speeded up in the future. As a device for handling a color document, for example, four ROS (Ras) are provided for each color of black (K), yellow (Y), magenta (M), and cyan (C).
There is a so-called tandem color printer that has a ter output scanner. However, since this tandem color printer is a method in which a plurality of separate ROSs form one image, a paper jam or other abnormal operation may cause a user or a service person to make a part of the image forming apparatus. Temporarily move from the original image forming position, return to the original position after exchanging those parts, and further, if there is a change in temperature, a change over time, or an impact, transfer them with the ROS. There is a big problem that a slight error occurs in the positional relationship of the belts, and a shift in the transfer position of each color, that is, a registration shift occurs.

The cause of the registration shift is a shift component in the main scanning direction of scanning by the ROS, a shift component in the conveying direction of the transfer belt, that is, a shift component in the sub-scanning direction, expansion / contraction of an image in the scanning direction of the ROS, that is, a scan magnification of the ROS Deviation component, ROS
Deviation in the scan direction, that is, a skew deviation component of ROS and the like. Therefore, the image position recognition pattern predetermined by each ROS is output from the pattern generator according to a certain rule, the image position recognition pattern is transferred to the transfer belt, and the CC arranged downstream of the ROS is arranged.
According to D, sampling is performed at a predetermined timing. The positional relationship expected to be obtained when it is assumed that there is no predetermined color shift in the image position recognition pattern of each color in the positional relationship of the sampling data of the image position recognition pattern of each color actually sampled by the CCD. And the amount of difference between them are detected, and the registration deviation amount of each color is calculated from the detected data. There is known a method of providing a high-quality image with less registration deviation by correcting the write timing of ROS based on the result (for example, Japanese Patent Laid-Open No. 1-142680).
Issue).

[0004]

However, although the conventional method described above can minimize the color registration deviation amount in the registration deviation measurement and correction cycle, it differs from the actual image formation cycle in the image formation cycle. However, there is a problem in that it is not possible to detect and calculate even the color registration shift factor, and as a result, an optimum color registration image cannot be obtained.

To explain this problem concretely, the color image formed by each image forming apparatus in the actual image forming cycle is different from that formed on the transfer belt in the registration deviation measurement and correction cycle. , Copy paper and OHP
It is formed on a recording medium such as a sheet. Further, when forming an image on a plurality of recording media, the transfer belt is dragged to the recording medium (hereinafter referred to as sidewalk of the belt) when the leading edge of the first recording medium bites into the fixing device. This is a factor that causes a color registration shift for the first and subsequent images.

The present invention solves the above-mentioned conventional problems, and in addition to the result of the registration deviation measurement on the transfer belt and the correction cycle, the color registration deviation factor associated with the actual image forming operation is corrected. It is an object of the present invention to provide a method for correcting a color registration deviation in a multiple image forming apparatus that can obtain an image with an optimum color registration by adding the value to the value and performing correction.

[0007]

To this end, according to the present invention, in a multiple image forming apparatus for forming multiple images by arranging a plurality of image output means along a transfer belt, color registration between the image output means is performed. A method for correcting a color registration deviation, which comprises adjusting an image control means for supplying image data to each image output means to control image formation, and a registration deviation measuring pattern for each image output means in the main scanning direction and the sub-scanning direction. A pattern generator that is repeatedly generated, a sampling unit that samples the image formed by each image output unit on both sides of the transfer belt in the main scanning direction, and an arithmetic process that takes in the data sampled by the sampling unit and performs an arithmetic process of the registration shift amount. Means and control means for controlling image output and image sampling, and the image sampling correction value Characterized by adding the actual recording medium color shift amount generated during discharge.

[0008]

In the present invention, in addition to the color registration shift amount measured and calculated on the transfer belt, the shift amount of the color registration shift factor associated with the actual image discharging operation is taken into consideration. The color registration can be corrected with high accuracy regardless of the number of sheets, and as a result, an optimum image can always be obtained.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram showing an embodiment of the present invention. The transfer belt 9 is a belt-shaped transfer member that transfers the image formed by the image output unit 8, and the image output unit 8 is
A plurality of image output means are arranged along the transfer belt 9 to form a multiple image. The image control unit 7 supplies image data to the image output unit 8 to control image formation, and is for repeatedly generating registration displacement measurement patterns in the main scanning direction and the sub scanning direction of the image output unit 8. Is.

The sampling section 3 is composed of, for example, a CCD sensor for sampling the image formed on the transfer belt 9 by the image output section 8 on both sides in the main scanning direction. The sampling start point and the sample width of the sampling section 3 are sampled. Is controlled by the sampling control unit 2. The arithmetic processing unit 5 takes in the image data sampled by the sampling unit 3 and performs arithmetic processing for calculating the registration shift, and the data storage unit 4 stores sampling data or arithmetic processing data.
The control unit 1 controls the image output and the image sampling. When performing the image sampling correction control, the sampling start point and the sample width of the sampling control unit 2 are set and the pattern for repeated registration deviation measurement is set. Is generated, the sampling data or the arithmetic processing data is integrated, and the pattern position is obtained. Then, the registration shift is detected, and the image control unit 7 and the image output unit 8 are controlled to perform corrections such as skew shift correction, magnification correction, main scanning direction shift correction, and sub-scanning direction shift correction.

FIG. 2 shows an example of a registration deviation measuring pattern. An image having a fixed length in the main scanning direction X-DIR and an image in the sub-scanning direction Y-DIR on both sides of the belt in the sub-scanning direction Y-DIR.
It consists of a combination of DIR and images of a certain length. A line having a predetermined width from the center of the CCD sensor to one side and having a predetermined length in the main scanning direction X-DIR is K, Y, M,
Lines having a predetermined length in the sub-scanning direction Y-DIR are arranged on the side (opposite side) in the sub-scanning direction Y-DIR in the order of C at predetermined intervals, and the sub-scanning direction is repeated each time the set is repeated. The Y-DIR line is expanded in the order of K, Y, M, and C.

FIG. 3 is a diagram for explaining an algorithm for correcting the registration shift. Registration misalignment correction is performed, for example, in FIG.
When there is a displacement such as the image Y with respect to the image K as shown in (a), the skew is corrected by first correcting the mirror angle other than the image K with the image K as the reference (b). After adjusting the angle as shown in (3), the magnification is corrected by controlling the clock frequency, the magnification in the main scanning direction is adjusted as shown in (C), and the correction is made in the main scanning direction by adjusting the write clock timing and phase. ), The main scanning direction X-DIR is aligned, and the sub-scanning direction Y-DIR is corrected as shown in (e) by the writing timing of the Line Sync signal (line feed signal) and the polygon phase correction, and finally. Correct within the allowable error.

FIG. 4 is a diagram showing a configuration example of a color registration deviation correction device, and FIG. 5 is a block diagram showing a configuration example of a registration deviation correction substrate. The CCD sensor 11 is the image forming apparatus 13
The image of the registration deviation measuring pattern (FIG. 2) formed on the transfer belt 7 by K, 13Y, 13M, and 13C is read, and one image is arranged at each end of the image area, and two images are arranged in total. The light source 12 is a light source for producing the background light necessary for the CCD sensor 11 to detect the image on the transfer belt 17, and is a CCD such as an LED or a halogen lamp.
Any material may be used as long as it can secure a sufficient amount of light as the light source of the sensor 11. In addition, the light source 12 deteriorates the light amount of itself, the transmittance of the transfer belt 17 deteriorates, and the CCD sensor 11
It is possible to freely change the light amount in order to secure an optimum image receiving state against the sensitivity deterioration of (1), the transmittance deterioration due to the dirt of the optical system, and the environmental change represented by the temperature.
The image forming apparatuses 13K, 13Y, 13M, and 13C are, for example, a combination of a photoconductor and a laser beam ROS or LED ROS, and are arranged at substantially equal intervals to form a black image and a yellow image, respectively. These are a device, a device that forms a magenta image, and a device that forms a cyan image.

The transfer belt 17 includes an image forming device 13K,
It has a transparent belt structure for transferring an image formed by 13Y, 13M and 13C, and is supported by a driving roller 19a and a driven roller 19b facing the driving roller 19a. Further, the transfer belt 17 has a function of conveying the recording medium, and the recording medium is conveyed from right to left in the drawing in the same manner as the belt rotating direction. At that time, in order to adsorb the recording medium to the belt member, a corotron for adsorption (not shown) is provided. The drive roller 19a is driven by a dedicated drive motor (not shown) having excellent constant speed,
The driven roller 19b rotates when its driving force is propagated by the transfer belt 17. Assay body 20
Is mounted with a CCD sensor 11, a drive circuit thereof, an optical system such as a SELFOC lens, and the mounting relationship between them is designed so that highly accurate positioning can be easily realized.

The interface board 14 sends an image signal to each ROS, and the registration deviation correction board 15 is provided.
Is a board that houses modules for the registration shift correction system, control board 16 is a board that houses modules that manage the operation of each board and the entire apparatus, and image processing board 21 is a memory and modules related to image processing. The substrate.

Next, the normal image forming mode will be described. When the front end of the recording medium conveyed by the transfer belt 17 reaches the transfer point directly below the image forming apparatus 13K, the front end of the image formed by the image forming apparatus 13K reaches the transfer point directly below the image forming apparatus 13K. The paper feeding timing and the image writing timing are determined so that there is no deviation in the sub-scanning direction (recording medium conveyance direction) between the image formed by the image forming apparatus 13K and the recording medium. When the recording medium reaches the transfer point,
Although not shown, the image formed by the image forming apparatus 13K is transferred by a transfer corotron or the like, and further reaches a transfer point directly below the image forming apparatus 13Y. The recording medium reaches the transfer point directly below the image forming apparatus 13Y, and the recording medium is transferred in the same manner as the transfer by the image forming apparatus 13K. Hereinafter, the image forming apparatuses 13M and 13C are also transferred in the same manner. The recording medium on which all the transfer is completed is further conveyed by a belt, and when it reaches the vicinity of the driven roller 19b, it is peeled from the transfer belt 17 by a corotron, a stripper or the like for peeling the recording medium from the transfer belt 17 although not shown. . After that, it is fixed by a fixing device or the like, and discharged outside the machine.

Next, the color registration deviation correction system will be described. The color registration shift correction is executed by entering a dedicated correction cycle preset in the apparatus. When a command is issued from the control board 16 to each board, this correction cycle starts. The registration error correction substrate 15 prepares for sampling the registration error measurement pattern,
When the correction cycle begins, the interface board 14
It plays the role of a pattern generator that outputs a registration deviation measurement pattern, and the registration deviation measurement pattern is transmitted from each interface board 14 to the image forming apparatuses 13K, 13Y, and 1.
Sent to 3M, 13C, patterns 18K, 18Y, 1
8M and 18C are transferred onto the transfer belt 17.

As shown in the figure, the registration shift measuring pattern is C
It is set to transfer to a position on the transfer belt 17 which passes directly under the CD sensor 11. Then, the CCD sensor 11
In the registration deviation correction board 15 for sampling the image data from, the sampling start timing and the sample end necessary and sufficient for sampling the registration deviation measurement pattern from the transfer timing in each interface board 14 and the pitch to the CCD sensor 11 The timing is calculated and the image data is captured.

In the registration error correction substrate 15, first, at the sample start timing, the image data from the CCD sensor 11 starts to be taken into the high speed memory, and at the sample end timing, the image data fetch is stopped. Then, at the same time as the end of the acquisition, by the time the sampling of the next registration deviation measuring pattern is completed, the image position is determined from the acquired image data by, for example, the center of gravity method, and used as the image position address, for example. Store in main memory. By repeating this operation several times, several fixed image position addresses are obtained for each image forming apparatus. Here, in order to improve the accuracy of the fixed image position address, these several fixed image position addresses may be averaged for each image forming apparatus.

Further, in the registration deviation correction substrate 15, a correction value for correcting the registration deviation between the image forming apparatuses is corrected according to a predetermined algorithm from the image position address determined for each image forming apparatus. It is calculated for each image forming apparatus. The calculated correction values are directly or indirectly set on the image forming apparatus, the interface board, or the like from the registration deviation correction board 15 to perform the correction.

The registration shift correcting board 15 is constructed as shown in FIG. 4, for example. In the registration shift correction substrate 15, CC
The driver 32 drives the CCD sensor in accordance with the clock generated by the D drive clock generation circuit 38, and sequentially reads the read image data of, for example, 8 bits and 256 gradations in the receiver 31 in pixel units. Then, the image data regarding the main scanning is stored in the high-speed image memory for main scanning 35 through the bus control system 34, and the image data regarding the sub-scanning is averaged by the image arithmetic circuit for sub-scanning 33, and then the bus control system. High-speed image memory 3 for sub-scanning through 34
6 is stored. The sample timing control circuit 39
The timing of fetching image data into the sub-scanning image arithmetic circuit 33, the main scanning high-speed image memory 35, and the sub-scanning high-speed image memory 36 is controlled according to the sampling start timing, sampling period, etc. set by the CPU 44. The main RAM 42 is used as a work area for the CPU 44, and the ROM 43 is used for the CPU 44.
The control program is stored. The serial communication IC 40 and the serial communication driver 41 include various correction systems 4
The CPU 44 sends control data such as setting parameters to the I / O interface 45.
Is for outputting an on / off signal to the various correction systems 47, inputting an on / off signal from the sensor, and transmitting / receiving an on / off signal to / from the system controller 48, which is provided between the CPU and the CPU. Serial communication driver 4
Data 6 is transmitted and received between the CPU 44 and the system controller 48.

The CPU 44 controls the CCD drive clock generation circuit 38, the sample timing control circuit 39, and the bus control systems 34 and 37 to take in the image data of the registration deviation measuring pattern outputted on the transfer belt and set the image position address. After confirming and calculating the registration shift amount, the serial communication IC4
0, through serial communication driver 41, or I /
The various correction systems 47 are controlled through the O interface 45 and the serial communication 46.

FIG. 6 is a flow chart for explaining the process of correcting the color registration deviation in the present invention. First, in step S1, the registration deviation measuring pattern is sampled, and in step S2, the deviation amount of each of the image forming apparatuses Y, M, and C is calculated with respect to the image forming apparatus K based on the result of each sampling. The known deviation amount in the copy cycle is added to the result of the deviation amount calculated in S3. And
In step S4, the amount of shift to each of the image forming apparatuses K, Y, M, and C is corrected.

Next, the known deviation amount in the copy cycle in step S3 of FIG. 6 will be described. FIG. 7 shows the color registration deviation amount generated in one direction depending on the type of recording medium (plain paper, OHP sheet) and thickness. The recording medium A is plotted against the curve of the color registration deviation amount on the transfer belt shown by the dotted line. , B, the misregistration amount increases by the difference between Z1 and Z2, respectively. FIG. 8 shows the amount of color registration deviation that always occurs in one direction in an image forming apparatus due to the influence of the sidewalk of the belt by the fixing device.
In the figure, when the leading edge of the recording medium enters the fixing device at point F, the recording medium is bitten by the fixing device, the transfer belt is dragged to the recording medium, and the trailing edge of the recording medium separates at point G. ing. In this case, with respect to the color registration deviation amount on the transfer belt shown by the dotted line, the registration deviation amount increases by the difference of Z3. In addition, the same state occurs when the recording medium is fed from the recording medium feeding device as well as the fixing device.

The amount of color registration deviation caused by the presence / absence of the recording medium may not be the same depending on the type of the recording medium, but it is possible to determine almost unambiguously by an experiment. Then, the known shift amount is stored in the data storage unit in advance, and the user designates the type of the recording medium, or a sensor for detecting the type and thickness of the recording medium is provided to automatically perform the correction process. . In addition, the amount of occurrence of color registration deviation due to the influence of the sidewalk of the belt can be almost uniquely determined after being assembled once due to mechanical attachment. Then, this known shift amount is stored in the data storage unit in advance, and the correction value is corrected again when the sidewalk of the belt occurs.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various modifications can be made. For example, in the above-described embodiment, the known deviation amount in the image forming cycle is described depending on the type of the recording medium and the sidewalk of the belt, but the influence of humidity may be added to the correction process.

[0027]

As is apparent from the above description, according to the present invention, in addition to the result of the registration deviation measurement on the transfer belt and the correction cycle, the color registration deviation factor associated with the actual image forming operation is corrected. By adding to the value and performing correction,
An image with an optimal color registration can be obtained.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a registration deviation measuring pattern according to the present invention.

FIG. 3 is a diagram for explaining an algorithm for registration shift correction in the present invention.

FIG. 4 is a diagram showing a configuration example of a color registration deviation correction device according to the present invention.

5 is a block diagram showing a configuration example of a registration deviation correction substrate of FIG.

FIG. 6 is a flowchart illustrating a process of correcting color registration deviation according to the present invention.

FIG. 7 is a diagram showing a color registration deviation amount that occurs in one direction depending on the type of recording medium.

FIG. 8 shows the influence of a belt walk by the fixing device.
FIG. 6 is a diagram showing a color registration deviation amount that occurs in one direction in an image forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Control part, 2 ... Sampling control part, 3 ... Sampling part 4 ... Data storage part, 5 ... Arithmetic processing part, 6 ... Pattern generator 7 ... Image control part, 8 ... Image output part, 9 ... Transfer belt

Claims (4)

[Claims] 1. A method of correcting a color registration deviation, in which a plurality of image output means are arranged along a transfer belt to form a multiple image, in which color registration between the image output means is adjusted. An image control means for supplying image data to each image output means to control image formation; a pattern generator for repeatedly generating a registration shift measuring pattern in the main scanning direction and sub-scanning direction of each image output means; Sampling means for sampling the image formed by the means on both sides of the transfer belt in the main scanning direction, arithmetic processing means for taking in the data sampled by the sampling means and calculating the registration deviation amount, and controlling image output and image sampling And a control means for controlling the image sampling correction value generated when the recording medium is actually discharged. Method of correcting color shift in the multiple image forming apparatus characterized by adding the Rareji shift amount. 2. The color registration deviation of the multiple image forming apparatus according to claim 1, wherein the amount of color registration deviation that occurs when the recording medium is actually discharged depends on the type or thickness of the recording medium. Correction method. 3. The color of a multi-image forming apparatus according to claim 1, wherein the color registration deviation amount generated when the recording medium is actually discharged is due to an influence of a side walk of a belt by a fixing device. How to correct misregistration. 4. A method of correcting a color registration deviation of a multiple image forming apparatus according to claim 1, wherein the amount of color registration deviation that occurs when the recording medium is actually discharged is due to the influence of humidity.