JP2000253231A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate difference in level caused in the inclination correction of an image owing to skew in a color image forming device. SOLUTION: This color image forming device for correcting the inclination of an image by shifting image data is provided with an image data accumulation means 21 for accumulating image data of plural lines, a shift flag accumulation means 22 for accumulating a shift flag showing the position of an image element shifting image data, a correction pattern generation means 23 for generating a correction pattern by information on a noticed image element and peripheral image elements and the shift flag and a smoothing processing means 24 for executing the smoothing processing of a step generated by the inclination correction of an image on image data based on the correction pattern and the shift flag.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus, and more particularly to a technique for correcting the inclination of an image of each color in an electrophotographic color image forming apparatus having a plurality of photosensitive members.

[0002]

2. Description of the Related Art Conventionally, in a color image forming apparatus employing an electrophotographic technique, a photoreceptor as an image carrier is charged by a charging means, and light is applied to the charged photoreceptor in accordance with image information. A latent image is formed, the latent image is developed by a developing unit, and the developed toner image is transferred to a sheet material or the like to form an image.

On the other hand, a plurality of image stations in which such a series of image forming processes are developed in accordance with colorization of an image are provided, and each color image of a cyan image, a magenta image, a yellow image, and preferably a black image is formed. A tandem-type color image forming apparatus that forms a full-color image by forming the image on each image carrier and superimposing and transferring each color image on a sheet material at a transfer position of each image carrier has also been proposed. Such a tandem-type color image forming apparatus has an image forming unit for each color, and is therefore advantageous for speeding up.

[0004] However, such a color image forming apparatus has a problem in how to properly perform registration (registration) of each image formed in a different image forming unit.

[0005] That is, an angular displacement (hereinafter, referred to as "skew") in an oblique direction occurs due to the angular displacement of the rotation axis of the photosensitive drum and the mounting angle of the scanning optical system in the image forming station, and the sheet material or the like. This is because the image formation positions of the four colors transferred in a superimposed manner shift, and finally appear as a position shift or a change in color tone.

FIG. 19 is an explanatory diagram showing an example of an image due to skew. FIG. 19A shows an image rising rightward, and FIG. 19B shows an image falling rightward.

Hereinafter, a skew correction in a conventional image forming apparatus will be described.

FIG. 20 is a block diagram showing the configuration of image data generating means in a conventional color image forming apparatus.

As shown in the figure, multi-value data input from an external device 66 is developed on a memory 67 as bitmap data. The expanded bitmap data is
The binarization processing means 68 performs binarization using halftone, dither, or the like. The image data binarized in this way is corrected for misalignment by the skew correction unit 69.

FIG. 21 is a block diagram showing the skew correction means of FIG.

As shown in FIG. 21, the skew correction means includes a shift amount setting means 70 for setting a shift amount due to skew in advance, a direction setting means 71 for indicating a direction in which skew is generated, and a binarized signal. A data storage unit 72 for storing image data in line units; and a data correction unit 73 for reading data from the data storage unit 72 in accordance with a correction amount.
And smoothing processing means 74 for correcting a level difference in data
It consists of.

FIG. 22 shows data of 600 pixels per line and 5
FIG. 9 is an explanatory diagram illustrating a case where a line shift occurs.

The skew of the image data is measured from the image data printed in advance (in this case, the image in FIG. 22), and the maximum number of lines 5 is set in the shift amount setting means 70. In the illustrated image, since the skew occurs to the lower right, 1 indicating the lower right is set in the direction setting means 71. This allows
In the data correction means 73, the data shift amount (the number of lines)
Divides one line into several blocks, and shifts the divided blocks by one line to correct the entire displacement.

Next, the data correction means 73 will be described. Here, FIG. 23 is a block diagram showing the data correction means of FIG.

In the data correction means 73, the number of data of one line and the number of data of one block are set. In FIG. 22, the number of data in one line is set to 600, and the number of data in one block is set to 100, which is the value of (the number of data in one line) / (shift amount + 1).

FIG. 24 is an explanatory diagram showing the memory configuration of the data storage means of FIG.

As shown, data is written in each block in units of 100 pixels. When looking at the data written on the fifth line, the data to be printed is shifted by five lines as shown in FIG. 22, so that block 6 is the data 84 on the sixth line and block 5 is the data 84 on the fifth line. By shifting the data 85 and the line to be read for each block line by line, an image having no apparent inclination is output.

FIG. 25 is a timing chart of the data correction means of FIG.

The input data is sequentially written to the memory at a write address generated by a counter which counts up by a clock synchronized with the data while HSZ indicating one line period is 0 (not shown).

Next, the read address will be described.

In FIGS. 23 and 25, the counter 7
5 and 76 are enabled when HSZ is 0, and are counted by the clock CK of one pixel unit. In the decoder 77, when the value of the counter 75 reaches 600, the reset 78 becomes 1, and the counter 75 is reset. In the decoder 79, when the value of the counter 76 reaches 100, the EQ signal 80 is set to 1 and the counter 76 is reset. The adder 81 outputs the EQ signal 8
The data of the adder 81 is held at 0 and the output of the latch 82 reset at the reset 78 and the number of data of one line 60
0, and the number of data in one line is 60 per block.
Add 0. The adder 83 adds the output of the counter 75 and the output of the latch 82 and outputs the result as a memory read address. The data read from the memory is input to the smoothing processing means 74 shown in FIG.

FIG. 26 is a block diagram showing the smoothing processing means of FIG.

As shown in the figure, the smoothing processing means comprises a pattern detection means 86 which forms a window and detects a predetermined pattern, and a data conversion means 87 which adds and deletes dots.

FIG. 27 is a block diagram showing the structure of the pattern detecting means of FIG.

When the EQ signal 80 is 1, the data is shifted by one line, and if there is a pixel before and after that, a level difference of one line occurs. The clock 3 of the pattern detecting means 86 has twice the frequency of the input data clock. The input data is stored in a memory 8 for storing one line of data.
8,89. Then, registers 90, 91, 92, and 9 latched at the clocks 3 with the memories 88 and 89.
Are shifted by half pixels by 3, 94, 95, and 3
A × 3 window is configured. After the EQ signal 80 is delayed by one line in the memory 3 that delays by one line, the register generates EQ1, EQ2, and EQ3.

FIG. 28 is an explanatory diagram showing a window constituted by the pattern detecting means of FIG. Here, the conversion target data is DD22.

FIG. 29 is a block diagram showing the structure of the pattern detecting means of FIG.

In the pattern detecting means, the window data (DD11 to DD33) and EQ1, EQ2, EQ3 are
A comparator 97 compares the discrimination table 96 previously written in a ROM (read only memory) with a pattern to detect a pattern, and according to the result, additional data 98 and deletion data 99.
Is output.

FIG. 30 is a block diagram showing the structure of the data conversion means of FIG.

The data conversion means adds or deletes data to the input data based on the additional data and the deletion data output from the pattern detection means.

FIG. 31 is a timing chart showing the timing of input data, additional data, deleted data, and output data of the data conversion means. As shown in the figure, the steps are corrected by adding and deleting small dots, and smoothing is performed.

[0032]

However, in the above-described conventional technique, the image quality is deteriorated by shifting the binarized data.

That is, for example, in the case of a natural image, when binarization is performed, gradation processing such as dither processing, error diffusion processing, and halftone processing is performed so that data can be arranged in a regular pattern arrangement. Become.

FIG. 32A shows the halftone-processed data, and FIG. 32B shows the result of shifting the data.

As shown in the drawing, the image pattern becomes irregular before and after the point where the image is shifted, and the image quality cannot be improved even if dots are added or deleted at the shifted position.

Accordingly, it is an object of the present invention to provide a color image forming apparatus capable of obtaining an image of high print quality by eliminating a level difference caused by image skew correction due to skew.

[0037]

In order to solve this problem, a color image forming apparatus according to the present invention is a color image forming apparatus which corrects the inclination of an image by shifting image data. Image data storage means for storing image data; shift flag storage means for storing a shift flag indicating a position of a pixel shifted from the image data; and a correction pattern is generated by information of a target pixel and surrounding pixels and a shift flag. The configuration includes a correction pattern generation unit and a smoothing processing unit that performs smoothing processing of a step generated due to image inclination correction on image data based on the correction pattern and the shift flag.

As a result, a smoothing process is performed on a step generated in the image skew correction due to the skew.
It is possible to obtain an image with a high printing quality without a step.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is a color image forming apparatus for correcting image inclination by shifting image data, wherein image data for storing a plurality of lines of image data is provided. An accumulating unit, a shift flag accumulating unit for accumulating a shift flag indicating a position of a pixel which has shifted the image data, a correction pattern generating unit for generating a correction pattern based on information of the target pixel and surrounding pixels and a shift flag, A color image forming apparatus having smoothing processing means for performing smoothing processing of a step generated by image inclination correction on image data based on a pattern and a shift flag, and a step generated by image inclination correction by skew. Smoothing processing is performed, and it is possible to obtain an image with high print quality without steps. It has the effect of.

According to a second aspect of the present invention, in the first aspect of the present invention, the correction pattern generated by the correction pattern generating means is obtained from a binary data pattern and a gradation data pattern constituted by a table. The color image forming apparatus has an effect that the correction pattern can be easily added and changed, and the data can be easily searched.

According to a third aspect of the present invention, in the first or the second aspect of the present invention, the correction pattern generating means is arranged so that the target pixel is located at the center and the correction pattern generating means is arranged in the main scanning direction.
A color for forming a correction pattern from 54 pieces of pixel information in which five lines constituting one line are arranged in the sub-scanning direction, and a total of 10 pieces of shift flag information of 5 pieces each on both sides of the target pixel in the sub-scanning direction An image forming apparatus;
Since the correction corresponding to the binary data and the gradation data can be performed with the same pattern configuration, there is an effect that it is not necessary to provide a circuit for distinguishing between the binary data and the gradation data.

According to a fourth aspect of the present invention, in the first, second or third aspect of the present invention, the correction pattern generating means is arranged such that the number of binary data patterns is smaller than the number of gradation data patterns. The correction pattern generated by the correction pattern generating means is
Since the number of binary data patterns can be made smaller than the number of gradation data patterns, the number of correction pattern data can be reduced, and the circuit scale can be reduced. .

According to a fifth aspect of the present invention, in the first, second, third or fourth aspect of the present invention, the correction pattern for the gradation data in the correction pattern generating means is provided when the inclination is corrected. This is a color image forming apparatus that includes a level difference caused by a data shift, and the data need only be corrected before and after the position where the data is shifted. Has the effect that it becomes possible.

According to a sixth aspect of the present invention, in the first, second, third, fourth or fifth aspect, the correction pattern for the binary data in the correction pattern generating means is:
This is a color image forming apparatus in which print data of 5 pixels or more is continuous. Since print data of 5 pixels continuous can be corrected as binary data, there is no need to provide a circuit for distinguishing between binary data and gradation data. This has the effect that correction according to each of the value data and the gradation data can be performed.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In these drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted.

FIG. 1 is a schematic diagram showing the configuration of a color image forming apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram showing image data generating means in the color image forming apparatus of FIG. 1, and FIG. FIG. 4 is a time chart of the memory of FIG. 3, FIG. 5 is a block diagram showing a circuit configuration of the data selector of FIG. 3, and FIG. 6 is a circuit configuration of the data register of FIG. 7, FIG. 7 is an explanatory diagram showing a matrix composed of the data registers of FIG. 3, FIG. 8 is a block diagram showing a configuration of the shift flag storage means of FIG. 2, and FIG. 9 is a correction pattern generation means of FIG. FIG. 10 is a block diagram showing a circuit configuration for generating a binary data pattern of FIG. 10, FIG. 10 is a block diagram showing a circuit configuration for generating a gradation data pattern by the correction pattern generation means of FIG. 2, 11 is a time chart showing the setting timing of the correction pattern data, FIG. 12 is an explanatory diagram showing a configuration example of the correction pattern, FIG. 13 is a block diagram showing the configuration of the smoothing processing means in FIG. 2, and FIG. 14 is the pattern matching in FIG. FIG. 15 is a block diagram showing a circuit configuration.
13 is an explanatory diagram showing correction information generated by the correction information generating circuit in FIG. 13, FIG. 16 is an explanatory diagram showing a specific example of the correction information in FIG. 15, and FIG. 17 is a description showing a circuit configuration of the correction information generating circuit in FIG. FIG. 18 is an explanatory diagram showing an example of a correction result output from the correction information generating circuit of FIG.

First, a process of obtaining a color image will be described with reference to FIG.
This will be described with reference to FIG.

In FIG. 1, the color image forming apparatus
One image station 1a, 1b, 1c, 1d is arranged, and each image station 1a, 1b, 1c, 1d is a photosensitive drum (photosensitive member) 2a, 2b, 2 as an image carrier.
c, 2d, around which charging means 3a, 3b, 3c, 3d for uniformly charging the surfaces of the photosensitive drums 2a, 2b, 2c, 2d, and visualizing the electrostatic latent image Developing means 4a, 4b, 4c, 4d, cleaning means 5a, 5b, 5c, 5d for removing residual toner, and light corresponding to image information to the respective photosensitive drums 2a, 2b, 2c, 2
exposure means 6a, 6b, 6c,
6d, intermediate transfer belt (transfer material) constituting transfer means 7
Transfer means 8a, 8b, 8c for transferring the toner image to
8d are arranged respectively.

Here, the image stations 1a, 1b, 1
In c and 1d, a yellow image, a magenta image, a cyan image, and a black image are formed, respectively.
From b, 6c and 6d, a yellow image, a magenta image,
Exposure lights 9a, 9b, 9c and 9d, which are scanning lights corresponding to the cyan image and the black image, are output.

The exposure means 6a, 6b, 6c and 6d are controlled by the image data generating means 13 whose displacement has been corrected by the displacement setting means 14 in which the displacement due to skew has been set.

Each image station 1a, 1b, 1c, 1
d, the photosensitive drums 2a, 2b, 2c,
An endless belt-shaped intermediate transfer belt 12 supported by rollers 10 and 11 is disposed below 2d, and rotates in the direction of arrow A. These operations are controlled by control means.

The sheet material 16 stored in the sheet cassette 15 is fed by a sheet feed roller 17 and is discharged to a sheet discharge tray (not shown) via a sheet material transfer roller 18 and a fixing unit 19. You.

In the color image forming apparatus having the above configuration, first, in the image station 1d, the charging means 3d
A latent image of black component color, which is image information, is formed on the photosensitive drum 2d by a known electrophotographic process means using the exposure means 6d and the like. Thereafter, the image is visualized as a black toner image by a developing material having a black toner by a developing unit 4d, and the intermediate transfer belt 1 is formed by a transfer unit 8d.
2, a black toner image is transferred.

On the other hand, while the black toner image is being transferred to the intermediate transfer belt 12, a latent image of the cyan component color is formed at the image station 1c, and the cyan toner image of the cyan toner is visualized by the developing means 4c. Then, this is transferred by the transfer means 8 c and is superimposed on the black toner image previously transferred on the intermediate transfer belt 12.

Thereafter, image formation is performed in the same manner for the magenta toner image and the yellow toner image. When the superposition of the four color toner images on the intermediate transfer belt 12 is completed, the paper feed cassette 15 is fed by the paper feed roller 17. The toner images of four colors are collectively transferred and conveyed by a sheet material transfer roller 18 onto a sheet material 16 such as paper fed from the fixing unit 1.
At 9, the image is heated and fixed, and a full-color image is obtained on the sheet material 16.

Each of the photosensitive drums 2a, 2b, 2c, and 2d, to which the transfer has been completed, is connected to a cleaning unit 5a,
At 5b, 5c, and 5d, the residual toner is removed, and the printing operation is completed in preparation for the subsequent image formation.

As described above, a color image can be obtained, but each image station 1a, 1b, 1c, 1d
And the exposure means 6a, 6b, 6c, and 6d, which are scanning optical systems, cause skew of each color. Since the skew differs between the devices, the skew is measured from the output image at the time of assembling and adjusting the devices, and the amount of deviation is previously written in a ROM or the like in the skew correction circuit 20 (FIG. 2). The shift amount may be automatically detected. In this case, the automatically detected shift amount is written to the skew correction circuit 20.

As shown in FIG. 2, the image data generating means includes a skew correction circuit 20, an image data storage means 21,
Shift flag storage means 22, correction pattern generation means 23
And smoothing processing means 24. With such image data generating means, data input from an external device is corrected by the skew correction circuit 20 according to the inclination of the image. The image data corrected by the skew correction circuit 20 is stored in the image data storage unit 2.
1 is stored. FIG. 3 shows the configuration of the image data storage means 21.

The image data 25 is input to the data selector 26. In the data selector 26, write data to the memory 33 is generated and output to the data bus 29. Here, a memory having an 8-bit data bus will be described as an example. Address 30 of memory 33, write enable (WE) 31, read enable (RE) 3
2 is generated by the timing circuit 28. When the correction is performed with five lines, the input data becomes n lines, and the n-1 line, the n-2 line, the n-3 line, and the n-4 line are stored in the memory. The address 31 switches to the addresses of the n-1, n-2, n-3, and n-4 lines in units of two clocks. FIG. 5 shows the data selector 2 of FIG.
6 is a block diagram showing a detailed circuit configuration of FIG. The counter 38 is a 2-bit counter that counts up at the RE 32, and the select signal 40, which is an output, takes a value from 0 to 3 synchronized with the RE 32. The data read from the memory 33 is input to flip-flop circuits 34, 35, 36. Flip-flop circuits 34, 35, 36,
37 clk1, clk2, clk3, and clk4 are generated by the decoder circuit 39. The decoder circuit 39 is composed of a combination of the select signal 40 and RE 32, and each of clk 1 and clk is selected according to the value of the select signal 40.
2, clk3 and clk4 become 1. Therefore, the data of the address n-1 is stored in the flip-flop circuit 34, the data of the address n-2 is stored in the flip-flop circuit 35,
The flip-flop circuit 36 holds the data at the address n-3, and the flip-flop circuit 37 holds the data at the address n-4. The selector 42 receives the outputs of the flip-flop circuits 34, 35, and 36 and the data obtained by converting the input data into 8-bit data by a parallel-serial (parallel-serial) conversion circuit 41. Is done. The output signal of the selector 42 is WE3
When 1 is 0, it is output to the data bus 29 and written to the memory 33.

The flip-flop circuits 34, 35, 36,
37, the output of the parallel-serial conversion circuit 41 is input to the data register 27. Here, FIG. 6 shows a circuit configuration of the data register 27 of FIG. The n-line data, n-1 line data, n-2 line data, n-3 line data, and n-4 line data of the input 8-bit data are converted into 1 by the parallel-serial conversion circuits 43, 44, 45, 46, and 47. Converted to bits. The converted data is stored in the shift register 4
8, 49, 50, and 51 are input to Q0 to Q1 respectively.
It is output as 11 consecutive data shifted to 0 in clock units.

In the data register 27, a matrix is composed of data of 5 pixels in the sub-scanning direction and 11 pixels in the main scanning direction.
The line Q5 data is the target pixel to be corrected. FIG.
Shows the configuration of the matrix. As shown in the figure, five lines in which 11 pieces of pixel information are arranged in the main scanning direction are provided in the sub-scanning direction, and the target pixel is located at the center. Then, 54 pieces of pixel information are located around the target pixel. Therefore, from the point of view of the pixel of interest,
This means that a total of 11 lines each including 5 pieces of pixel information on both sides in the main scanning direction and two lines on each side in the sub-scanning direction, for a total of 5 lines.

Next, the shift flag storage means will be described.

Since the correction data is two lines before, the shift flag also needs to be delayed by two lines. Since the shift flag refers to data on both sides of the target pixel in the main scanning direction, the input shift flag information is input to the shift register 54 after being delayed by two lines by the two-line delay memory 53, and , And data for a total of 11 pixels, each of which is five in both sides in the main scanning direction.

By forming a correction pattern from the pixel information of two lines in the sub-scanning direction and 10 pieces of pixel information in the main scanning direction for the target pixel in this manner, for example, continuous image data such as a straight line of a binary image is obtained. And patterns corresponding to dispersed image data such as gradation data can be separately set. As a result, corrections corresponding to binary data and grayscale data can be performed with the same pattern configuration, and it is not necessary to provide a circuit for determining binary data and grayscale data.

Next, the correction pattern generating means 23 will be described. The correction pattern generating means 23 is composed of a binary data pattern and a gradation data pattern.

Since the grayscale data is discrete data and the binary data is continuous data, the data of one pixel before and after the target pixel and the data of five pixels on the left and right are referred to, By using the data correction pattern, it is possible to correct binary data. Therefore, the binary pattern is composed of the target pixel and its surrounding 33 pixels. The CPU 54 takes a 16-bit data bus as an example. The CPU 54 sets 11-bit data in each of the register 56, the register 57, and the register 58. The outputs of the registers 56, 57, and 58 are input to the buffer 59, and the buffer 59 outputs 33-bit data.

In FIG. 10, the gradation data is discrete data, and the continuity of pixels is lower than that of the binary pattern.
The pixels constitute a gradation data correction pattern.
16 bits from CPU 54 to register 61, register 6
Set 9 bits to 2. Register 61, Register 62
Is input to the buffer 63, and 2
5-bit data is output.

In FIG. 11, a decoder 55 has a CPU
The 54 addresses are decoded, and a chip select signal (CS) corresponding to each address is generated. Register 56
Is CS1, register 57 is CS2, register 58 is CS
At the rising edge of No. 3, the data of the CPU 54 is held. Since one binary data pattern and one grayscale data pattern can be formed with the circuit configurations shown in FIGS. 9 and 10, a plurality of correction patterns can be generated by configuring each pattern with a plurality of tables. .

As a result, it is possible to easily add or change the correction pattern and to easily search for data.

In the correction pattern generated by the correction pattern generating means 23, the number of binary data patterns can be made smaller than the number of gradation data patterns. That is, since the pixel data of the gradation data is relatively dispersed, it is necessary to compare all the correction patterns with the input data, and it is necessary to have a large number of correction pattern data. For example, in the case of a correction pattern composed of 54 unit pixels, it is desirable to have all 54 data. On the other hand, since the image data is continuous for the binary data, the correction pattern can be composed of a relatively small number of data.

Therefore, by reducing the number of binary data patterns, the number of correction pattern data can be reduced, and the circuit scale of the comparison circuit and the like can be reduced.

In FIG. 12, (a) and (b) show a gradation data pattern, and (c) shows a binary data pattern.

Next, the smoothing processing means 24 will be described.

In FIG. 13, the smoothing processing means is output from the pattern matching circuit 63 and the pattern matching circuit 63 for comparing the input data stored in the image data storage means 21 with the correction pattern generated by the correction pattern generation means 23. And a data conversion circuit 65 that corrects the input data based on the data output from the correction information generating circuit 64 and outputs the corrected data.
Then, the pattern matching circuit 63 compares the input data with the correction pattern generated by the correction pattern generator 23. In FIG. 14, the pattern matching circuit 63
Is input to the correction information generating circuit 64. The correction information generation circuit 64 generates correction information for correcting a pixel from the output of the pattern matching circuit 63 and the output of the shift flag storage unit 22.

FIG. 15 shows the correction information. Here, a case where 1/4 pixel of the unit pixel is added or deleted will be described.

The correction information generating circuit 64 outputs 14 types of correction signals. For example, del1 is a correction for deleting one pixel, and add4 is a correction for adding 1/4 pixel to the left.

In FIG. 16, is a correction for deleting one pixel, and del1 becomes 1. Is a correction for adding one pixel, and add1 becomes 1. Is a correction to add 1/2 pixel to the right, and add3 is 1. Is a correction to add 1/4 pixel to the right, and add5 becomes 1.

In FIG. 17, the correction information generation circuit 64 classifies the result of ANDing the output of the pattern matching circuit 63 and the data of the shift information into 14 types of correction information.
The result of the OR for each classification is output as final correction information. The 14 types of correction information are stored in the data conversion circuit 6.
5 is input. The data conversion circuit 65 is composed of a table for selecting the pixels shown in FIG. 15 based on the correction information, and the pixels of the correction information that have become 1 are output as print data. When all the outputs of the correction information are 0, the correction is not performed and the input data is output as it is. FIG. 18 shows an example of the correction result.

In the gradation data shown in FIG. 18, the pattern in which the pixels approach each other due to the skew and the density changes is made uniform by moving the pixels. In the binary data shown in FIG. 18, the level difference is corrected by adding a pixel having a small level difference caused by the skew, and smoothing is performed.

If the correction pattern generated by the correction pattern generating means 23 includes a step due to a data shift generated when the inclination is corrected, the data is corrected only before and after the position where the data is shifted. Since it is sufficient to perform the process, the image data stored in the image data storage unit 21 can be reduced.

In the correction pattern generated by the correction pattern generating means 23, particularly, the correction pattern for binary data is such that the print data is made continuous by 5 pixels or more.
Since print data of five consecutive pixels can be corrected as binary data, there is no need to provide a circuit for determining binary data and gradation data, and correction according to binary data and gradation data can be performed.

[0082]

As described above, according to the present invention, a smoothing process is performed on a step generated by correcting the inclination of an image due to skew, and it is possible to obtain an image with no step and high print quality. That is, an effective effect is obtained.

If the correction pattern generated by the correction pattern generation means is obtained from the binary data pattern and the gradation data pattern constituted by a table, it is possible to easily add and change the correction pattern, and to change the data. An effective effect that search can be easily performed is obtained.

If a correction pattern is created from 54 pieces of pixel information centering on the target pixel and 10 pieces of shift flag information, corrections corresponding to binary data and gradation data can be made with the same pattern configuration. Therefore, it is possible to obtain an effective effect that it is not necessary to provide a circuit for determining binary data and gradation data.

By making the number of binary data patterns smaller than the number of gradation data patterns, it is possible to reduce the number of correction pattern data and to reduce the circuit scale. Effects can be obtained.

The correction pattern for the gradation data in the correction pattern generation means includes a step generated by shifting the data when the inclination is corrected, so that the data can be corrected before and after the position where the data is shifted. Since only this need be performed, it is possible to obtain an effective effect that it is possible to reduce the amount of image data stored in the image data storage unit.

By making the print data continuous for five or more pixels with respect to the correction pattern for the binary data by the correction pattern generating means, the print data for five consecutive pixels can be corrected as binary data. It is no longer necessary to provide a circuit for determining whether the data is binary or gray scale data.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a color image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing image data generating means in the color image forming apparatus of FIG.

FIG. 3 is a block diagram illustrating a configuration of an image data storage unit in FIG. 2;

FIG. 4 is a time chart of the memory of FIG. 3;

FIG. 5 is a block diagram showing a circuit configuration of the data selector of FIG. 3;

FIG. 6 is a block diagram showing a circuit configuration of the data register of FIG. 3;

FIG. 7 is an explanatory diagram showing a matrix composed of the data registers of FIG. 3;

FIG. 8 is a block diagram showing a configuration of a shift flag storage unit of FIG. 2;

9 is a block diagram showing a circuit configuration for generating a binary data pattern of the correction pattern generation means of FIG.

FIG. 10 is a block diagram showing a circuit configuration for generating a gradation data pattern by the correction pattern generation means of FIG. 2;

FIG. 11 is a time chart showing setting timing of correction pattern data;

FIG. 12 is an explanatory diagram showing a configuration example of a correction pattern.

FIG. 13 is a block diagram showing a configuration of a smoothing processing unit in FIG. 2;

FIG. 14 is a block diagram showing the configuration of the pattern matching circuit of FIG.

FIG. 15 is an explanatory diagram showing correction information generated by the correction information generation circuit of FIG.

16 is an explanatory diagram showing a specific example of the correction information in FIG.

FIG. 17 is an explanatory diagram showing a circuit configuration of the correction information generation circuit of FIG.

18 is an explanatory diagram illustrating an example of a correction result output from the correction information generation circuit in FIG.

FIG. 19 is an explanatory diagram illustrating an example of an image due to skew;

FIG. 20 is a block diagram showing a configuration of image data generating means in a conventional color image forming apparatus.

FIG. 21 is a block diagram showing a skew correction unit of FIG. 20;

FIG. 22 is an explanatory diagram showing a case where a shift of five lines occurs in data of 600 pixels per line.

FIG. 23 is a block diagram showing the data correction means of FIG. 20;

FIG. 24 is an explanatory diagram showing a memory configuration of the data storage means of FIG. 21;

FIG. 25 is a timing chart of the data correction unit of FIG. 21;

FIG. 26 is a block diagram showing the smoothing processing means of FIG. 21;

FIG. 27 is a block diagram showing a configuration of a pattern detection unit in FIG. 26;

FIG. 28 is an explanatory diagram showing a window configured by the pattern detection means in FIG. 26;

FIG. 29 is a block diagram showing the configuration of the pattern detection means of FIG. 26;

FIG. 30 is a block diagram showing the configuration of the data conversion means of FIG. 26;

FIG. 31 is a timing chart showing timings of input data, additional data, deleted data, and output data of a data conversion unit.

FIG. 32 is an explanatory diagram showing halftone-processed data and a result of shifting the data;

[Explanation of symbols]

 21 image data storage means 22 shift flag storage means 23 correction pattern generation means 24 smoothing processing means

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C087 AA15 AA16 AC08 BC02 BD24 BD53 5C076 AA24 AA27 BA05 BA06 5C077 LL01 LL19 MP06 MP08 PP02 PP55 PP59 PP61 PP62 PP65 PP68 PQ08 PQ17 PQ20 PQ21 PQ22 PQ23 9A001HH24H

Claims (6)

[Claims] 1. A color image forming apparatus for correcting image inclination by shifting image data, comprising: image data storage means for storing a plurality of lines of the image data; and a position of a pixel having shifted the image data. Shift flag accumulating means for accumulating a shift flag indicating: a correction pattern generating means for generating a correction pattern based on information of a target pixel and surrounding pixels and a shift flag; and a tilt of an image based on the correction pattern and the shift flag. A color image forming apparatus comprising: a smoothing processing unit that performs a smoothing process of a step generated by the correction on the image data. 2. A color image forming apparatus according to claim 1, wherein the correction pattern generated by said correction pattern generating means is obtained from a binary data pattern and a gradation data pattern constituted by a table. 3. The correction pattern generating means is arranged so that 11 lines in the main scanning direction constitute one line in the sub-scanning direction so that the pixel of interest is centered.
3. The color image forming apparatus according to claim 1, wherein a correction pattern is created from a total of ten pieces of shift flag information for each pixel information and five pieces of shift flag information on both sides of the target pixel in the sub-scanning direction. 4. A color image forming apparatus according to claim 1, wherein said correction pattern generating means has a pattern number of binary data smaller than a pattern number of gradation data. 5. A method according to claim 1, wherein the correction pattern for the gradation data in the correction pattern generating means includes a step generated by a data shift when the inclination is corrected. 5. The color image forming apparatus according to 3 or 4. 6. A color image according to claim 1, wherein the correction pattern for the binary data by said correction pattern generating means is such that print data is continuous for 5 pixels or more. Forming equipment.