JP2001352445A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color image forming device that corrects a curved image and can obtain the image with high print quality. SOLUTION: The color image forming device has a means that stores image data of a plurality of lines, a maximum point setting means 22 that sets a point at which number of tilted lines is maximum with respect to a start point of the image data, a maximum value setting means 21 that sets the obtained number of lines providing a maximum gradient, a division means 23 that divides a range from the start point of the image up to the maximum point by the number of gradient lines, and an address control means 24 that controls write and read addresses to/from the storage means by each block divided by the division means 23, depending on the vertical direction of the gradient.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates 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 an image forming apparatus employing an electrophotographic system, a photosensitive member as an image carrier is charged by a charger, and the charged photosensitive member is irradiated with light in accordance with image information to form a latent image. An image is formed, the latent image is developed by a developing device, and the developed toner image is transferred to a sheet material or the like to form an image.

On the other hand, in accordance with colorization of an image, a plurality of image forming stations for performing the respective image forming processes are provided, and a cyan image, a magenta image, a yellow image,
Preferably, a tandem-type color image forming apparatus for forming a full-color image by forming each color image of a black 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, which is advantageous for speeding up.

However, there is a problem in how well the registration (registration) of each image formed by different image forming units is performed. An angular displacement (hereinafter, referred to as skew) in an oblique direction occurs due to an angular displacement of the rotation axis of the photosensitive drum in the image forming station and a mounting angular displacement of the scanning optical system. This is because the shift of the image forming position of the four colors transferred to the sheet material or the like finally appears as a position shift or a change in color tone. FIG. 15 shows an example of an image due to skew. FIG. 15A shows an image rising to the right and FIG. 15B shows an image falling to the right.

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

FIG. 16 is a block diagram of a conventional skew correction circuit.

A shift amount setting means 33 for setting a shift amount due to skew in advance, a direction setting means 34 for indicating a direction in which skew occurs, and a data storage means 35 for storing binarized image data in line units. Data correction means 3 for reading data from the data storage means according to the correction amount.
6.

FIG. 17 is a diagram for explaining line deviation due to skew. The skew of the image data is measured from the image data printed in advance, and the maximum number of lines is 5
Set. In the image of FIG. 17, the skew occurs to the lower right, so 1 indicating the lower right is set in the direction setting means. FIG. 18 shows a configuration diagram of a conventional data correction unit.
In the data correction means, the data shift amount (the number of lines)
One line is divided into several blocks, and the whole block is corrected by shifting the divided blocks for each line. The data correction means will be described with reference to FIG.
In the data correction means, the number of data in one line and the number of data in one block are set. In the example of FIG. 17, the number of data in one line is 600, and the number of data in one block is set to a value of (the number of data in one line) / (displacement amount + 1). 5
Looking at the data written on the line, the data to be printed is shifted by 5 lines as shown in FIG.
Block 6 shifts the data after 5 lines, and block 5 shifts the data to be read out for each block and the lines to be read for each block, one line at a time, so that an image having no apparent inclination is output. FIG. 19 shows a timing chart of the conventional data correction means. The input data is sequentially written to the memory at the write address generated by the address counter 37 which counts up by a clock synchronized with the data during which the HSZ indicating one line period is 0. The address counters 37 and 38 are enabled by HSZ, and count by a clock CK of one pixel unit.
In the decoder 39, the reset signal becomes 1 when the value of the address count 37 becomes 600 in the number of data in one line,
The address counter 37 is reset. Decoder 40
In this case, when the value of the address counter 38 reaches 100, the EQ signal is set to 1 and the address counter 38 is reset. The adder 41 holds the data of the adder 41 by the EQ signal, adds the output of the latch 42 reset by the reset signal and the number of data 600 of one line, and calculates the number of data 600 of one line for each block. to add. The adder 43 outputs the output of the address counter 37,
The outputs of the latches 42 are added and output as a memory read address. Thus, the data whose inclination has been corrected is read from the memory.

[0009]

However, in the above-mentioned conventional configuration, the inclination is corrected by shifting the data in one of the upper and lower directions, so that, for example, a curvature caused by a laser scanning optical unit (LSU) occurs. Figure 2
The data is scanned as shown by 0. If the deviation is corrected by, for example, the inclination detected at the point A, the deviation at the point A disappears, but the deviation at the end point becomes larger and the image quality deteriorates.

The present invention has been made in order to solve these problems, and an object of the present invention is to provide a color image forming apparatus capable of correcting an image due to curvature and obtaining an image with high print quality.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a plurality of image stations having a photoreceptor and developing means for developing a latent image formed on the photoreceptor as a toner image. And a plurality of exposure means for irradiating each photoconductor in the plurality of image stations with light to form a latent image, and a transfer means for transferring and conveying a toner image formed in the plurality of image stations to a transfer material A color image forming apparatus for forming a composite image by sequentially superimposing toner images visualized in the plurality of image stations on a transfer material, wherein a means for storing a plurality of lines of image data; A maximum point setting means for setting a point at which the number of lines of inclination with respect to the start point is maximum; a maximum value setting means for setting the number of lines with the obtained maximum inclination; From the storage unit to the maximum point by dividing the number of lines by the number of slope lines, and address control means for controlling addresses to be written and read from the storage means for each block divided by the division means according to the vertical direction of the slope. .

With the above configuration, the inclination due to the curvature is corrected by detecting the maximum value of the inclination, and an image with high print quality can be obtained.

[0013]

According to the first aspect of the present invention, there are provided means for storing image data of a plurality of lines, and a maximum for setting a point at which the number of lines inclined with respect to the starting point of the image data is maximum. Point setting means, maximum value setting means for setting the number of lines of the obtained maximum inclination,
Dividing means for dividing the image from the starting point to the maximum point by the number of inclined lines; and address controlling means for controlling addresses to be written and read from the accumulating means for each block divided by the dividing means according to the vertical direction of the inclination. Has,
An image forming apparatus characterized by preventing image quality deterioration due to color misregistration caused by different image data inclinations at the center and the end point, and by detecting the maximum value of the inclination and correcting the inclination due to the curvature, An output image with high printing quality can be obtained.

According to a second aspect of the present invention, there is provided the color image forming apparatus according to the first aspect, wherein the maximum point setting means and the maximum value setting means can be externally set. A color image forming apparatus according to claim 1. With this configuration, it is possible to easily set the inclination and the like.

According to a third aspect of the present invention, there is provided the color image forming apparatus according to the first aspect, wherein the number of blocks divided by the dividing means is the number of inclined lines + 1. Color image forming apparatus. With this configuration, correction according to the number of inclinations can be accurately performed, and an output image with high print quality can be obtained.

According to a fourth aspect of the present invention, there is provided a color image forming apparatus according to the third aspect, wherein the storage means includes an SR.
A color image forming apparatus comprising an AM. With this configuration, data can be written and read at high speed, and processing can be speeded up.

(Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram of a color image forming apparatus according to Embodiment 1 of the present invention.
FIG. 3 is a configuration diagram of an image data generating unit according to the first embodiment of the present invention, FIG. 3 is a diagram illustrating an example of a curved image according to the first embodiment of the present invention, and FIG. FIG. 5 is a diagram showing the relationship between addresses and data according to the first embodiment of the present invention. FIG. 6 is a diagram showing the configuration of address control means according to the first embodiment of the present invention. 8 is a flowchart at the time of writing in Embodiment 1, FIG. 8 is a flowchart of column address generation in Embodiment 1 of the present invention, FIG. 9 is a flowchart of a comparison counter in Embodiment 1 of the present invention, and FIG.
0 is a flowchart of row address generation in the first embodiment of the present invention, FIG. 11 is a timing chart of RE and WE in the first embodiment of the present invention, and FIG. 12 is a data array on a memory in the first embodiment of the present invention. 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 has a photoreceptor 2a, 2b, 2c, 2d as an image carrier, and a dedicated area around it. Charging means 3a, 3b, 3
c, 3d, developing means 4a, 4b, 4c, 4d, cleaning means 5a, 5b, 5c, 5d, and exposure means 6a, 6b of a scanning optical system for irradiating each photosensitive drum with light corresponding to image information. , 6c, 6d, and transfer units 8a, 8b, 8c, 8d in the transfer means 7 are arranged, respectively.

Here, the image stations 1a, 1b, 1
c and 1d are for forming a yellow image, a magenta image, a cyan image and a black image, respectively. The exposure means 6a, 6b, 6c and 6d output light 9a corresponding to the yellow image, magenta image, cyan image and black image, respectively.
9b, 9c and 9d are output. Each image station 1
a, 1b, 1c, 1d.
An unsupported belt-shaped intermediate transfer belt 12 supported by support rollers 10 and 11 is disposed below 2b, 2c and 2d, and moves in the direction of arrow A. These operations are controlled by the control means.

The sheet material 16 stored in the sheet cassette 15 is fed by a sheet feeding 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 above configuration, the image data output from the pattern detecting means 14 is subjected to various data processing by the resist pattern generating means 13, and the known electronic means such as the charging means 3d of the image station 1d and the exposure means 6d. After forming a latent image of the black component color of the image information on the photoreceptor 2d by the photographic process means, it is visualized as a black toner image by a developing material having a black toner by the developing means 4d, and is intermediately transferred by the transfer unit 8d. The black toner image is transferred to the belt 12.

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

Hereinafter, the magenta toner image and the yellow toner image are formed in the same manner, and when the superposition of the four color toner images on the intermediate transfer belt 12 is completed, the paper feed roller 17 feeds the paper cassette. 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. In addition, each photoconductor 2 after the transfer is completed.
a, 2b, 2c, 2d are cleaning means 5a, 5b,
At 5c and 5d, the residual toner is removed, and the printing operation is completed in preparation for the subsequent image formation.

Although a color image can be obtained as described above, skew and curvature of each color occur due to misalignment between each image forming station and the scanning optical system and curvature of the scanning optical system.

FIG. 2 shows the structure of the resist pattern generating means 13. The resist pattern generating means 13 includes an image data accumulating means 20, a maximum value setting means 21, a maximum point setting means 22, a dividing means 23, and an address control means 24.

FIG. 3 shows an example of a curved image. in this case,
There is a shift of up to three lines. This maximum deviation amount 3 is set in the maximum value setting means. The maximum point value is determined by the distance d from the start point of the center point c between the start point a and the end point b where the shift amount is the maximum, for example, a resolution of 600
In the case of dpi, it is set in the maximum point setting means as an integer value of a value obtained by d × 25.4 mm ÷ 600 (Equation 1).

According to the value set by the maximum value setting means,
Divide from the starting point to the maximum point value. Here, an example of four divisions is shown. In the dividing means, the number of data of one block obtained by dividing the range from the starting point to the maximum point value into four is set.
One line is divided into eight.

The resist pattern generating means 13 includes HS
Valid image data is input during the period when Z is 0, and is stored in the image data storage unit 20. FIG. 4 shows the configuration of the image data storage means 20. The memory 25 has 8 bits, and the input image data has 1 pixel per 4 bits. That is, two pixels of data are written in the memory 25 per byte. FIG. 5 shows the relationship between addresses and data. It is assumed that one line of image data is written per row address. Here, for simplicity, the number of input image data is 32 pixels, and the memory has an 8-bit configuration. 1
Since the image data is 2 pixels per byte, 32
The column address required to store pixel data is Fh
(F hexa). When the data of 32 pixels is divided into eight, that is, the column address Fh is divided into eight, one block is configured as two addresses. This equation 2 is set in the dividing means. FIG. 6 shows the configuration of the address control means 24. FIG. 7 shows a flowchart at the time of writing. In the column address generation circuit 26, at the time of initializing, the count = 0,
Start address 0h (a). When HSZ becomes 0 and write enable (WE) becomes 0, one is added from address 0 (b), and when the address becomes Fh, the address is set to 0 and the process returns to (a) (c). In the row address generation circuit 27,
One is added each time the column address becomes Fh. In this way, the image data is sequentially written into the image data storage means 20.

Next, the reading operation will be described. FIG. 8 shows a flowchart of the column address generation. In the column address generation circuit 26, at the time of initializing, the count is 0, and the start address is 0h (d). HSZ is 0, read enable (R
When E) becomes 0, the address is incremented by 1 from address 0 (e). When the address becomes Fh, the address is set to 0 and the process returns to (d) (f). FIG. 9 shows a flowchart of the comparison counter 28. The comparison counter 28 is incremented by the number (here, 2) set in the dividing means (g). When the counter value becomes equal to the column address, the EQ flag is set to 1 (h), the number set by the dividing means is added, the EQ flag is set to 0, and the process returns to (g) (i). FIG. 10 shows a flow of row address generation. In the row address generating circuit 27, at the time of initializing, the count is 0, and the start address is 0h (j). E
When Q becomes 1 (k), the counter is counted one by EQ, and the row address is incremented by one (l). When the count number becomes の of the division number (4 in this case) (m), the addition of the row address is stopped. Next, when the EQ becomes 1 (n), the row address is decremented by one, and when the count number becomes the division number-1, the row address is decremented by one (j).
Return to (o).

FIG. 11 is a timing chart of RE and WE. When HSZ becomes 0, WE becomes 0 first, and writing is performed. Next, RE is set to 0 and reading is performed.
Thereafter, the write and read are sequentially switched to 0.

As described above, the image data storage means 20
The data sequentially written in the data is read one line below the block for each block up to the point of the maximum deviation, and the data on one line is read after the point of the maximum deviation. FIG. 12 shows an array of data to be read on the memory.
The column address is divided into eight from a1 to a8. As shown in FIG. 3, in order to correct the data curved upward, the data below one line is read out from a1 to a point a4 where the displacement is the largest, and the data above one line is read out from a5 to a8 thereafter. Thus, the apparent curvature is corrected.

(Embodiment 2) Hereinafter, Embodiment 2 of the present invention will be described. FIG. 13 shows Embodiment 2 of the present invention.
FIG. 4 is a configuration diagram of maximum point setting means and maximum value setting means in FIG. The maximum point setting means and the maximum value setting means include a CPU 29, a decoder 30, and registers 31 and 32. A specific address is assigned as a maximum point value (register 31) and a maximum value (register 32), respectively, and the decoder 30 decodes the address and generates a select signal. Select signal and CPU2
The data of the CPU 29 is held in the register by the write signal WR of No. 9. This allows any maximum points,
The maximum value can be set, and settings can be easily made for each device, for example.

(Embodiment 3) Hereinafter, Embodiment 3 of the present invention will be described. FIG. 14 shows Embodiment 3 of the present invention.
FIG. 4 is a diagram illustrating a dividing unit in FIG. The number of blocks to be divided by the dividing means is (the number of lines of the maximum value + 1) × 2 of the detected inclination, so that the correction can be efficiently performed with the minimum configuration. FIG. 14 illustrates the dividing means. If the maximum number of lines is 3, the number of blocks is 8. When the block is divided into eight equal parts, three lines can be corrected by shifting each block by one line. Thereby, the configuration is easy and efficient correction can be performed.

Embodiment 4 Hereinafter, Embodiment 4 of the present invention will be described. By using an SRAM as the memory of the storage means, high-speed access becomes possible and write / read switching can be performed at high speed, so that it is possible to easily cope with high-speed data transfer.

[0036]

As described above, according to the present invention, the direction of the line to be read can be switched to the point where the deviation is maximum when the curvature occurs, and thereafter, the direction can be changed in one direction. It is possible to correct the curvature that could not be corrected by the conventional configuration in which only the correction was possible, and it is possible to obtain a color image forming apparatus with high print quality.

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram of an image data generation unit according to the first embodiment of the present invention.

FIG. 3 is a diagram showing an example of a curved image according to the first embodiment of the present invention;

FIG. 4 is a configuration diagram of an image data storage unit according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a relationship between an address and data according to the first embodiment of the present invention.

FIG. 6 is a configuration diagram of an address control unit according to the first embodiment of the present invention.

FIG. 7 is a flowchart at the time of writing according to the first embodiment of the present invention;

FIG. 8 is a flowchart of column address generation according to the first embodiment of the present invention.

FIG. 9 is a flowchart of a comparison counter according to the first embodiment of the present invention.

FIG. 10 is a flowchart of row address generation according to the first embodiment of the present invention.

FIG. 11 is a timing chart of RE and WE in Embodiment 1 of the present invention.

FIG. 12 is a diagram illustrating a data array on a memory according to the first embodiment of the present invention.

FIG. 13 is a configuration diagram of a maximum point setting unit and a maximum value setting unit according to the second embodiment of the present invention.

FIG. 14 is a diagram illustrating a dividing unit according to the third embodiment of the present invention.

FIG. 15 is a diagram illustrating an example of an image due to skew;

FIG. 16 is a block diagram of a conventional skew correction circuit.

FIG. 17 is a diagram illustrating a line shift due to a skew;

FIG. 18 is a configuration diagram of a conventional data correction unit.

FIG. 19 is a timing chart of a conventional data correction unit.

FIG. 20 is a diagram showing an example of an image after a conventional data correction

[Explanation of symbols]

 1a, 1b, 1c, 1d Image station 2a, 2b, 2c, 2d Photoconductor 3a, 3b, 3c, 3d Charging means 4a, 4b, 4c, 4d Developing means 5a, 5b, 5c, 5d Cleaning means 6a, 6b, 6c , 6d Exposure unit 7 Transfer unit 8a, 8b, 8c, 8d Transfer unit 9a, 9b, 9c, 9d Light 10, 11 Support roller 12 Intermediate transfer belt 13 Resist pattern generation unit 14 Pattern detection unit 15 Sheet cassette 16 Sheet material 17 Paper feed roller 18 Sheet material transfer roller 19 Fixing means

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H04N 1/46 H04N 1/46 Z F term (reference) 2H030 AA01 AB02 AD13 AD17 BB02 BB16 BB23 BB42 5C074 AA02 AA10 BB03 CC26 DD15 DD17 DD24 EE11 FF15 GG14 HH02 5C076 AA23 AA36 BA03 BA04 BA06 BA08 5C077 LL01 LL19 MP08 NP05 PP21 PP33 PP39 PP59 PP62 PQ22 SS05 TT03 TT06 5C079 HB03 LA24 LA39 MA02 NA02 NA11

Claims (4)

[Claims] 1. A means for accumulating image data of a plurality of lines, a maximum point setting means for setting a point at which the number of lines of inclination is maximum with respect to a starting point of the image data, and a line number of the obtained maximum inclination A maximum value setting unit for the inclination, a division unit for dividing the image from the starting point to the maximum point by the number of lines of the inclination, and a storage unit for each block divided by the division unit according to the vertical direction of the inclination. A color image forming apparatus having address control means for controlling addresses for writing and reading from an image, and preventing image quality deterioration due to color misregistration caused by different image data inclinations at the center and the end point. 2. The color image forming apparatus according to claim 1, wherein the maximum point setting means and the maximum value setting means can be set externally. 3. The color image forming apparatus according to claim 1, wherein the number of blocks divided by said dividing means is the number of inclined lines + 1. 4. The color image forming apparatus according to claim 1, wherein said storage means comprises an SRAM.