JP3463594B2 - Color image forming equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus adopting an electrophotographic system, a photoconductor as an image bearing member is charged by a charger, and the charged photoconductor is irradiated with light according to image information. 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 the image.

On the other hand, with the colorization of images, a plurality of image forming stations for performing the above-mentioned 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 transferring each color image on a sheet material at the transfer position of each image carrier Is also proposed. Since such a tandem type color image forming apparatus has an image forming section for each color, it is advantageous for speeding up.

However, there is a problem in how to perform the registration (registration) of the images formed by different image forming units. A positional deviation in an oblique direction (hereinafter referred to as a skew) occurs due to an angular deviation of the rotation axis of the photosensitive drum in the image forming station and a mounting angular deviation of the scanning optical system. This is because the displacement of the image forming positions of the four colors transferred to the sheet material or the like finally appears as a displacement or a change in color tone.

FIG. 20 shows an example of an image due to skew.
FIG. 20 (a) is an image that rises to the right, and FIG. 20 (b) is an image that descends to the right. The skew correction in the conventional color image forming apparatus will be described below.

FIG. 21 shows a block diagram of an image data generating means in a conventional color image forming apparatus. The multi-valued data input from the external device 62 is expanded on the memory 63 as bitmap data. The developed bitmap data is binarized by halftoning, dithering, etc. by the binarization processing means 64. The skew correction unit 65 corrects the deviation of the binarized image data.

FIG. 22 is a block diagram of the skew correction means shown in FIG. The skew correction means 65 includes a deviation amount setting means 66, a direction setting means 67, a data storage means 68, a data correction means 69, and a smoothing processing means 70.

A shift amount due to skew is set in advance in the shift amount setting means 66. The direction in which the skew is generated is set in the direction setting means 67. The data storage unit 68 stores the binarized image data in line units. The data correction unit 69 reads out image data corresponding to the correction amount from the data storage unit 68 based on the shift amount set by the shift amount setting unit 66 and the direction set by the direction setting unit 67. The smoothing processing means 70 is
The step difference of the image data read from the data storage means 68 is corrected.

FIG. 23 is a diagram showing an example of an image shifted by 5 lines. FIG. 23 shows an image based on the skew shown in FIG.

The skew of the image data is measured from the image data printed in advance, and the maximum line number 5 is set in the deviation amount setting means 66. In the image of FIG. 23, the skew occurs in the downward rightward direction, so the direction setting means 67 is set to 1 indicating downward rightward.

The data correction means 69 corrects the entire shift by dividing one line into several blocks according to the amount of data shift (the number of lines) and shifting the divided blocks line by line.

The number of data of one line and the number of data of one block are set in the data correcting means 69. FIG. 23
In the example, 600 is set as the number of data of one line, and (the number of data of one line) / (deviation amount + 1) = 100 is set as the number of data of one block.

FIG. 24 is a diagram showing a memory configuration of the data correction means of FIG. Data is written in each block in units of 100 pixels. When looking at the data written in the fifth line, the data to be printed is shifted by five lines as shown in FIG. 23. Therefore, in block 6, the sixth line data 70 and in block 5, the fifth line data 71 are printed. By shifting the line to be read for each block for each line, an image having no apparent inclination is output.

FIG. 25 is a block diagram of the data correction means of FIG. FIG. 26 is a timing chart showing the operation of the data correction means shown in FIG.

As shown in FIG. 25, the data correction means is
Counters 72, 73, decoders 74, 76, adder 7
8, 80 and latch 79.

The counter 72 is supplied with a clock signal CK for each pixel in synchronization with data, a signal HSZ indicating a period of one line, and a reset signal RS. The counter 72 counts up the clock signal CK while the signal HSZ indicating the period of one line is 0. The output of the counter 72 is given to the memory of the data storage means 68 of FIG. 22 as a write address. As a result, the input data is sequentially written in the memory of the data storage means 68.

The read address will be described below. The counter 73 has a signal HS indicating the period of one line.
Z, a clock signal CK and a signal EQ described later are applied. The counters 72 and 73 are enabled (activated) when the signal HSZ indicating the period of one line is 0, and count up the clock signal CK for each pixel. The decoder 74 sets the reset signal RS to 1 when the count value of the counter 72 reaches the data number 600 of one line. As a result, the counter 72 is reset. Decoder 7
6 sets the signal EQ to 1 when the count value of the counter 73 reaches 100, which is the number of data in one block. Thereby,
The counter 73 is reset.

The adder 78 holds the data output from the adder 78 in response to the signal EQ, and resets the reset signal RS.
The output of the latch 79 which is reset by and the number of data of one line are added. As a result, the data number 600 is sequentially added to the line data number 600 for each line.

The adder 80 adds the count value of the counter 72 and the output of the latch 79, and the data storage means 68.
It is output as the read address of the memory.

When the signal EQ is 1, the data is shifted by one line, so that when there is a pixel before and after that, a step difference of one line occurs. Therefore, in order to correct the step, the data output from the data storage means 68 is given to the smoothing processing means 70 of FIG.

FIG. 27 is a block diagram of the smoothing processing means shown in FIG.

The smoothing processing means 70 includes a pattern detecting means 81 and a data converting means 82. The pattern detection means 81 forms a window and detects a predetermined pattern. The data conversion means 82 adds and deletes dots.

FIG. 28 is a block diagram of the pattern detecting means shown in FIG. As shown in FIG. 28, the pattern detecting means 81 includes memories 83, 84, 93 and registers 85-85.
Including 90, 94, 95.

The clock signal CK3 supplied to the pattern detecting means 81 is set to a frequency twice that of the clock signal CK synchronized with the input data. The input data is sequentially stored in the memories 83 and 84 that store data for one line. The registers 85 to 90 latch the input data in response to the clock signal CK3. The data input by the memories 83 and 84 and the registers 85 to 90 is shifted for each half pixel, and 3 × 3 data D
A window including 11 to D33 is configured. Also,
The signal EQ is delayed by one line by the memory 93 and then applied to the registers 94 and 95 in order. Thereby, the signals EQ1, EQ2, EQ3 are sequentially generated.

FIG. 29 is a block diagram of a window formed by the pattern detecting means shown in FIG. In the example of FIG. 29, the conversion target data and the conversion target signal are DD22 and EQ.

FIG. 30 is a block diagram of the pattern detecting section of the pattern detecting means shown in FIG. As shown in FIG. 30,
The pattern detection unit 81a includes a discrimination table 91 and a comparator 92.

The discrimination table 91 is written in advance in a ROM (Read Only Memory). The comparator 92 is shown in FIG.
A pattern is detected by comparing the window data DD11 to DD33 and the signals EQ1, EQ2 and EQ3 shown in FIG. 9 with the discrimination table 91, and the memory 93 and the register 94 are output according to the detection result.

FIG. 31 is a block diagram of the data converting means of FIG. 32 is a timing chart showing the operation of the data conversion means of FIG.

The data converting means of FIG. 31 is the AND circuit 9
8 and an OR circuit 99. The AND circuit 98 calculates the logical product of the input data and the deleted data output from the pattern detection unit 81a of FIG. The OR circuit 99 is A
The logical sum of the output of the ND circuit 98 and the additional data output from the pattern detection unit 81a is calculated.

As a result, as shown in FIG. 32, small dots are added to and deleted from the input data to correct the step, and smoothed output data can be obtained.

[0031]

However, in the conventional color image forming apparatus described above, the image quality is deteriorated by shifting the binarized data. For example, in the case of a natural image, dither processing, error diffusion processing,
By performing gradation processing such as halftone processing, the data becomes an array of patterns having regularity.

FIG. 33 (a) is a diagram showing half-tone processed data, and FIG. 33 (b) is a diagram showing a result of shifting the data of FIG. 33 (a).

As shown in FIG. 33, the image pattern becomes irregular before and after the point where the image is shifted,
Image quality cannot be improved even if dots are added or deleted at the shifted positions.

The present invention has been made to solve these problems, and it is an object of the present invention to provide a color image forming apparatus capable of correcting the inclination of an image due to skew and obtaining an image of high print quality. To aim.

[0035]

An image forming apparatus according to the present invention includes a rotation processing means for performing rotation processing of image data in accordance with an inclination of an image for each color, and rotation for image data obtained by the rotation processing means. Position information generating means for generating position information indicating the position of the step of the image generated by the processing, and binarizing processing means for binarizing the image data obtained by the rotation processing means to obtain binary data. And a correction unit for performing a smoothing process on the binary data obtained by the binarization processing unit based on the position information generated by the position information generation unit to correct the step of the image.

In the color image forming apparatus according to the present invention, the image data rotation processing is performed according to the inclination of the image for each color, and the position of the step of the image generated by the rotation processing in the obtained image data is shown. Location information is generated. Further, the image data obtained by the rotation process is binarized to obtain binary data. Then, smoothing processing is performed on the binary data based on the position information,
The step in the image is corrected.

As described above, since the image data is binarized after the inclination due to the image skew is corrected by the rotation processing, the image pattern does not become irregular, and an image of high print quality can be obtained. You can

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A color image forming apparatus according to the invention of claim 1 is a rotation processing means for performing rotation processing of image data according to an inclination of an image for each color, and image data obtained by the rotation processing means. Position information generating means for generating position information indicating the position of the step of the image generated by the rotation processing, and binarization processing for binarizing the image data obtained by the rotation processing means to obtain binary data. And 2 based on the position information generated by the position information generating means.
And a correction unit for performing a smoothing process on the binary data obtained by the binarization processing unit to correct the step of the image.

In the color image forming apparatus according to the present invention, the image data is rotated according to the inclination of the image for each color, and the position of the step of the image generated by the rotation processing in the obtained image data is shown. Location information is generated. Further, the image data obtained by the rotation process is subjected to the binarization process to obtain the binary data. Then, smoothing processing is performed on the binary data based on the position information,
The step in the image is corrected.

In this way, the image data is binarized after the inclination due to the image skew is corrected by the rotation process, so that the image pattern is not irregular and an image of high print quality is obtained. You can

A color image forming apparatus according to a second aspect of the present invention is the color image forming apparatus according to the first aspect of the invention, in which the correction means is obtained by the binarization processing means.
Storage means for storing the value data, window forming means for forming a window from the binary data stored in the storing means, binary data in the window formed by the window forming means and position information generating means It includes pattern detection means for detecting a specific pattern from position information, and correction means for correcting binary data based on the detection result of the pattern detection means.

In this case, the correction means accumulates binary data, and a window is formed from the accumulated binary data. Then, a specific pattern is detected from the binary data in the window and the position information, and the binary data is corrected based on the detection result.

A color image forming apparatus according to a third aspect of the present invention is the color image forming apparatus according to the first or second aspect of the present invention, in which the pattern detection means specifies a pattern specified from outside as a specific pattern. It includes a storage means for storing as.

In this case, it is possible to easily change and add a specific pattern detected by the pattern detecting means, and it is possible to detect with high accuracy.

A color image forming apparatus according to a fourth aspect of the present invention is the color image forming apparatus according to the first aspect, the second aspect or the third aspect of the invention, wherein the correction means is obtained by the binarization processing means. The smoothing process is performed in an area designated externally in the obtained binary data.

In this case, when a defect occurs due to a detection error or the like, it is possible not to correct the defective region.

A color image forming apparatus according to a fifth aspect of the present invention is the color image forming apparatus according to any one of the first to fourth aspects, further comprising character detecting means for detecting a character portion of the image data. Further, the binarization processing means is
Of the image data obtained by the rotation processing means, the area detected by the character detection means as a character portion is binarized by threshold processing, and the correction means performs smoothing processing based on the detection result of the character detection means. It is a thing.

In this case, the character portion of the image data can be optimally corrected, and the image quality of the character portion can be improved.

(Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS. 1 is a configuration diagram of a color image forming apparatus according to Embodiment 1 of the present invention.

First, the process of obtaining a color image is shown in FIG.
Will be explained.

In FIG. 1, the color image forming apparatus has four
One image station 1a, 1b, 1c, 1d is arranged, and each image station 1a, 1b, 1c, 1d has a photoconductor 2a, 2b, 2c, 2d as an image carrier, and its surroundings are dedicated. Charging means 3a, 3b, 3
c, 3d, developing means 4a, 4b, 4c, 4d, cleaning means 5a, 5b, 5c, 5d, a scanning optical system for irradiating each photoconductor 2a, 2b, 2c, 2d with light according to image information. The exposing means 6a, 6b, 6c and 6d, and the transfer devices 8a, 8b, 8c and 8d in the transfer means 7 are arranged.

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, and light 9a, which corresponds to the yellow image, the magenta image, the cyan image and the black image from the exposing means 6a, 6b, 6c and 6d, respectively. 9b, 9c and 9d are output. Below the photoconductors 2a, 2b, 2c, 2d, the support rollers 10,
Belt-shaped intermediate transfer belt 1 supported by 11
2 is arranged and moves in the direction of arrow A. These operations are controlled by the control means.

Further, the sheet material 16 stored in the paper feed cassette 15 is fed by the paper feed roller 17 and is ejected to a paper ejection tray (not shown) via the sheet material transfer roller 18 and the fixing means 19. It

In the above-described structure, the image information (image data) of each color is given from the image data generating means 13 to the exposing means 6a, 6b, 6c, 6d.

First, after a latent image of a black component color of image information is formed on the photoconductor 2d by a known electrophotographic process means such as the charging means 3d and the exposing means 6d of the image forming station 1d, it is black by the developing means 4d. The black toner image is visualized as a black toner image by the developer having toner, and the black toner image is transferred to the intermediate transfer belt 12 by the transfer device 8d.

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

Thereafter, the magenta toner image and the yellow toner image are formed by the same method, and when the superimposing of the four color toner images on the intermediate transfer belt 12 is completed, the paper feed roller 17 feeds the paper feed cassette. A sheet material transfer roller 1 is provided on a sheet material 16 such as paper fed from 15.
The toner images of four colors are collectively transferred and conveyed by 8 and heat-fixed by the fixing means 19 to obtain a full-color image on the sheet material 16.

It should be noted that each of the photoconductors 2 after the transfer is completed.
a, 2b, 2c, 2d are cleaning means 5a, 5b,
The residual toner is removed at 5c and 5d, and the printing operation is completed in preparation for the next image formation to be performed subsequently.

A color image can be obtained as described above, but each image forming station 1a, 1b, 1c,
A misalignment between 1d and the scanning optical system occurs, and a skew occurs for each color. Since the skew differs between devices, measure the skew from the output image when assembling and adjusting the device,
The deviation amount is written in advance in the deviation amount setting means 14 configured by a ROM (Read Only Memory) or the like. Similarly, it is also possible to automatically detect the deviation amount, and the detected deviation amount is written in the deviation amount setting means 14.

FIG. 2 is a block diagram of the image data generating means of FIG. The image data generating means 13 includes a memory 10
1, a rotation processing means 20, a binarization processing means 21, a position flag generating means 22, a pattern detecting means 23, a data converting means 24 and an output means 25.

In the present embodiment, the position flag generating means 2
2 corresponds to the position information generating means, and the pattern detecting means 23
The data conversion means 24 corresponds to the correction means. The data conversion means 24 corresponds to the correction means.

The multivalued data input from the external device is rotated by the rotation processing means 20 based on the deviation amount set in the deviation amount setting means 14 of FIG.

FIG. 3 is a flow chart showing the processing of the rotation processing means of FIG.

The rotation processing means 20 comprises a deviation amount setting means 14
Based on the shift amount n set to, the m pieces of data of one line are divided into n blocks of the data number b (S1).
Here, the data number b of one block is as follows.

B = m / n (1) By shifting each of the n blocks for each line, the first pixel and the last pixel are shifted by n lines.

Next, the final point (final pixel) of each block is calculated as the shift point SPi (S2).
The shift point SPi is given by the following equation.

SPi = b × i (i = 1, 2, ..., N) (2) As an example, when the number of data on one line is m = 1000 and the shift amount is n = 5, the number of data on one block Is b = 20
0, each shift point is SP1 = 200, SP2
= 400, SP3 = 600, SP4 = 800, and S
P5 = 1000.

Next, the write address to the memory 101 is calculated from this shift point SPi (S3).

FIG. 4 is a flow chart showing the write address calculation process.

First, after resetting, the pointers P1 and P2 are set to 0 (S4). Next, add 1 to the address (S
5). When the pointer P1 is different from the shift point SP1 (S6), 1 is added to the pointer P1 (S7),
Return to S5. When the pointer P1 is equal to the shift point SP1 (S6), 1 is added to the pointer P2 (S8).

Next, the pointer P is set to the data number m of one line.
A value obtained by multiplying by 2 is added to the address (S9). At the same time, the pointer P1 is set to 0 (S10), and the process returns to S5.

As a result, the address is set to 1 for each block.
The line is shifted, and the address is shifted by n lines in the final block. Data is written in the memory 101 by the address thus generated. Memory 10
The data written in 1 is sequentially read and binarized by the binarization processing means 21 of FIG.

FIG. 5 is a diagram showing the binarization processing by the binarization processing means of FIG. Data for determining the binary level is written in the table TB in advance. Below, table T
The data of B is called table data.

The binarization processing means 21 compares the table data prepared in advance with the input data. If the input data is larger than the table data, the binary data is set to 1, and the input data is the table data. The binary data is set to 0 in the following cases. The size of the table TB can be set to any size such as 3 × 3 and 8 × 8.

FIG. 6 is a block diagram of the position flag generating means of FIG. The position flag generating means 22 includes a counter 26.
And a comparator 27. The counter 26 is the memory 10
Clock signal CK synchronized with the data read from 1
To count. The comparator 27 compares the count value of the counter 26 with the shift point SPi obtained by the rotation processing means 20, and the count value and the shift point SP.
When i is equal to i, a flag signal FL which becomes 1 is generated.

At the shift point SPi, a step difference of one pixel is generated depending on the data.
The pattern detecting means 23 detects the data and smoothes the data.

FIG. 7 is a block diagram of the pattern detecting means shown in FIG. As shown in FIG. 7, the pattern detection means 23
Are memories M1, M2, M3 and registers R1 to R8.
including.

The clock signal CK2 supplied to the pattern detecting means 23 is set to a frequency twice that of the clock signal CK synchronized with the input data. The input data D33 is the memory M1, which stores data for one line.
It is accumulated in M2 in order. The registers R1 to R6 latch the data input in response to the clock signal CK2. The data input by the memories M1 and M2 and the registers R1 to R6 is shifted for each half pixel to form a window composed of 3 × 3 matrisk data D11 to D33. The flag signal FL is delayed by one line by the memory M3 and then applied to the registers R7 and R8 in order. Thereby, the flag signals FL1, FL2,
FL3 is sequentially generated.

FIG. 8 is a block diagram of a window formed by the pattern detecting means shown in FIG. In the example of FIG. 8, the conversion target data and the conversion target flag signal are D22 and F.
It becomes L2.

FIG. 9 is a block diagram of the pattern detecting section of the pattern detecting means shown in FIG. As shown in FIG. 9, the pattern detection unit 23a includes a discrimination table 29 and a comparator 30.
including.

The discrimination table 29 is written in advance in a ROM (Read Only Memory). The comparator 30 uses the window matrisk data DD11 to DD33 shown in FIG.
A pattern is detected by comparing the flag signals FL1, FL2, FL3 with the discrimination table 29, and additional data and deleted data are output according to the detection result.

FIG. 10A shows an example of a data pattern in which a step difference of one pixel is generated in the sub-scanning direction, and FIG.
Shows an example of a data pattern after one clock time has elapsed.

The discrimination table 29 has a flag signal FL1.
To FL3 and matrisk data D11 to D33, several types of table data are written, each of which includes 12 flag signals FL1 'to FL3' and matrisk data D11 'to D33'.

In FIG. 10A, the table 1 is F
L1 '= 0, FL2' = 0, FL'3 = 1, D11 '=
1, D12 '= 1, D13' = 1, D21 '= 0, D2
2 '= 0, D23' = 1, D31 '= 1, D32' =
1, D33 '= 0 is written. The input flag signals FL1 to FL3 and the matrisk data D11 to
When D33 is equal to the flag signals FL1 ′ to FL3 ′ and the data D11 ′ to D33 ′ in Table 1, the comparator 30 outputs 1 as the deleted data.

In FIG. 10B, the table 2 is F
L1 '= 0, FL2' = 1, FL3 '= 0, D11' =
1, D12 '= 1, D13' = 1, D21 '= 0, D2
2 '= 1, D23' = 1, D31 '= 1, D32' =
0 and D33 '= 0 are written. The input flag signals FL1 to FL3 and the matrisk data D11 to
When D33 is equal to the flag signals FL1 ′ to FL3 ′ and the matrices data D11 ′ to D33 ′ in Table 2, the comparator 30 outputs 0 as additional data.

FIG. 11 is a block diagram of the data conversion means shown in FIG. FIG. 12 is a timing chart showing the operation of the data conversion means shown in FIG.

The data converting means 24 of FIG. 11 includes an AND circuit 31 and an OR circuit 32. The AND circuit 31
The logical product of the input data and the deleted data output from the pattern detection unit 23a in FIG. 9 is calculated. The OR circuit 32 is
The logical sum of the output of the AND circuit 31 and the additional data output from the pattern detection unit 23a is calculated. As shown in FIG. 12, by adding and deleting small dots to the input data, the step difference is corrected, and smoothed output data is obtained.

As described above, according to the color image forming apparatus of the present embodiment, the image data is binarized after the inclination due to the skew of the image is corrected by the rotation processing, so that the image pattern is irregular. And an image with high print quality can be obtained.

(Second Embodiment) Next, a second embodiment of the present invention will be described. FIG. 13 shows the second embodiment of the present invention.
FIG. 3 is a block diagram of a part of pattern detection means of the color image forming apparatus in FIG.

In the second embodiment, the pattern detecting means 23
31 to register a plurality of discrimination tables in
46 is provided. In FIG. 13, the register 3
The illustration of 3-45 is omitted.

The data of the discrimination table transferred from the outside by the data of the external interface and the clock signal is held in the registers 31 to 46 for each clock signal. It is possible to have a plurality of discrimination tables by increasing the number of registers. This allows the determination table to be set from the outside. The configuration of the other parts of the color image forming apparatus in the second embodiment is similar to that of the color image forming apparatus in the first embodiment.

(Third Embodiment) Next, a third embodiment of the present invention will be described. FIG. 14 shows a third embodiment of the present invention.
3 is a block diagram of a data conversion unit of the color image forming apparatus in FIG.

As shown in FIG. 14, the data conversion means 24
Includes an AND circuit 47 and OR circuits 48, 49 and 50. An OFF signal that can be set from the outside is input to one input terminal of each of the OR circuits 48 and 49. OR
The circuit 48 calculates the logical sum of the additional data and the off signal. The OR circuit 49 calculates the logical sum of the deleted data and the off signal. The AND circuit 47 calculates the logical product of the input data and the output of the OR circuit 48. The OR circuit 50 is A
The logical sum of the output of the ND circuit 47 and the output of the OR circuit 49 is calculated.

When the off signal is 0, dots are added and deleted by the data conversion process. When the off signal is 1, the input data is output as it is. The configuration of the other parts of the color image forming apparatus in the third embodiment is similar to that of the color image forming apparatus in the first embodiment.

In the color image forming apparatus of this embodiment, when a defect occurs due to a detection error or the like, it is possible not to smooth the area of the defective data.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described. FIG. 15 shows a fourth embodiment of the present invention.
2 is a block diagram of the color image forming apparatus in FIG.

The image data generating means 13a of FIG. 15 is provided with a character detecting means 51 for detecting a character portion from input data. The configuration of the other part of the image data generating means 13a of FIG. 15 is the same as the configuration of the image data generating means 13 of FIG.

FIG. 16 is a block diagram of the character detecting means in the fourth embodiment of the present invention. As shown in FIG. 16, the character detection means 51 includes a data storage means 52 and a determination means 53.

The data accumulating means 52 accumulates the data rotated by the rotation processing means 20 shown in FIG. The determination means 53 determines whether or not the input data is a character portion based on the data stored in the data storage means 52, and outputs the determination signal DT as 1 when it is a character portion.

FIG. 17 is a block diagram of the data storage means of the color image forming apparatus according to the fourth embodiment of the present invention. As shown in FIG. 17, the data storage means 52 includes line memories LM1 and LM2 and registers R11 to R16.
including.

The input data DL33 is sequentially stored in the line memories LM1 and LM2 holding one line of data. The registers R11 to R16 latch data for each pixel. The data input by the line memories LM1 and LM2 and the registers R11 to R16 is 1
3 × 3 data DL11 to DL that are shifted for each pixel
A window consisting of 33 is constructed.

FIG. 18 is a block diagram of a window formed by the data storage means of FIG. In the example of FIG. 18,
The processing target data is DL22. As shown in FIG. 18, a 3 × 3 window composed of data DL11 to DL33 is configured.

The determination means 53 in FIG. 16 is the data storage means 5
Data DL of a total of 9 windows formed by 2
In 11 to DL 33, when there are continuous dots of 3 pixels in any of the vertical, horizontal, and diagonal directions, it is determined to be a character portion, and the determination signal DT is set to 1.

FIG. 19 is a block diagram of the binarization processing means of FIG. As shown in FIG. 19, the binarization processing means 21
Includes a threshold processing unit 54, a halftone / dither processing unit 55, and a selector 56.

Threshold processing unit 54 and halftone /
The data processed by the rotation processing means 20 is input to the dither processing unit 55. The threshold processing unit 54 performs threshold processing on the input data and outputs binarized data. The halftone / dither processing unit 55 performs binarization processing such as halftone processing other than threshold value processing and dither processing on the input data, and outputs the binarized data.

Based on the determination signal DT, the selector 56 selectively outputs the data output from the threshold value processing unit 54 when the input data is the character portion, and the input data is the character portion. If not, the data processed by the halftone / dither processing unit 55 is selectively output.

That is, when the determination signal DT is 1,
Thresholding is performed on the input data. In the threshold processing, 1 is output when the input data is larger than 50% of the maximum value of the input data, and 0 is output when the input data is small. When the determination signal DT is 0, the binarization processing means 21 performs the operation described in the first embodiment.

Further, in the data conversion means 24 of FIG. 15, when the decision signal DT is 0, the input data is output as it is. As a result, it is possible to perform processing limited to the character portion in particular, and it is possible to achieve higher image quality when outputting only characters or when character output is frequently used.

[0109]

As described above, according to the present invention, by performing the binarization processing and the smoothing processing on the image data after the rotation processing, the image pattern does not become irregular, The inclination of the image can be corrected more smoothly, and a color image forming apparatus with high print quality can be obtained.

[Brief description of 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 block diagram of the image data generating means of FIG.

FIG. 3 is a flowchart showing the processing of the rotation processing means in FIG.

FIG. 4 is a flowchart showing write address calculation processing.

5 is a diagram showing the binarization processing by the binarization processing means of FIG.

FIG. 6 is a block diagram of the position flag generating means of FIG.

FIG. 7 is a block diagram of the pattern detection means in FIG.

8 is a configuration diagram of a window formed by the pattern detection means of FIG.

9 is a block diagram of a pattern detection unit of the pattern detection means of FIG.

FIG. 10 is a diagram showing an example of a pattern in a pattern detection unit of the pattern detection means in FIG.

11 is a block diagram of the data conversion means of FIG.

FIG. 12 is a timing chart showing the operation of the data conversion means shown in FIG.

FIG. 13 is a block diagram of a part of pattern detection means of the color image forming apparatus according to the second embodiment of the present invention.

FIG. 14 is a block diagram of data conversion means of a color image forming apparatus according to a third embodiment of the present invention.

FIG. 15 is a block diagram of a color image forming apparatus according to a fourth embodiment of the present invention.

FIG. 16 is a block diagram of character detection means according to the fourth embodiment of the present invention.

FIG. 17 is a block diagram of data storage means of a color image forming apparatus according to a fourth embodiment of the present invention.

18 is a configuration diagram of a window formed by the data storage means of FIG.

19 is a block diagram of the binarization processing means of FIG.

FIG. 20 is a diagram showing an example of an image due to skew.

FIG. 21 is a configuration diagram of an image data generating unit in a conventional color image forming apparatus.

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

FIG. 23 is a diagram showing an example of an image with a shift of 5 lines.

24 is a diagram showing a memory configuration of the data correction means in FIG. 22.

FIG. 25 is a block diagram of the data correction means in FIG. 22.

FIG. 26 is a timing chart showing the operation of the data correction means in FIG. 25.

FIG. 27 is a block diagram of the smoothing processing means shown in FIG.

28 is a block diagram of the pattern detection means shown in FIG. 27.

29 is a configuration diagram of a window formed by the pattern detection means in FIG. 28.

FIG. 30 is a block diagram of a pattern detection unit of the pattern detection means in FIG.

FIG. 31 is a block diagram of the data conversion means of FIG. 27.

32 is a timing chart showing the operation of the data conversion means of FIG. 31.

FIG. 33 (a) is a diagram showing halftone-processed data, and FIG. 33 (b) is a diagram showing a result of shifting data.

[Explanation of symbols]

1a, 1b, 1c, 1d image stations 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 means 7 Transfer means 8a, 8b, 8c, 8d transfer device 9a, 9b, 9c, 9d light 10, 11 Support roller 12 Intermediate transfer belt 13 Image data generation means 14 Deviation amount setting means 15 paper cassettes 16 sheet materials 17 Paper feed roller 18 Sheet material transfer roller 19 Fixing means 20 rotation processing means 21 Binarization processing means 22 Position flag generating means 23 pattern detection means 24 Data conversion means 29 discrimination table 30 comparator 101 memory

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H04N 1/409 H04N 1/40 103A (58) Fields investigated (Int.Cl. ⁷ , DB name) H04N 1/38-1 / 409 G06T 3/60 G03G 15/01

Claims (5)

(57) [Claims] 1. A rotation processing means for rotating the image data according to the inclination of the image for each color, and a position indicating the position of the step of the image generated by the rotation processing in the image data obtained by the rotation processing means. Position information generating means for generating information, binarizing processing means for performing binary processing on the image data obtained by the rotation processing means to obtain binary data, and position generated by the position information generating means. A color image forming apparatus comprising: a correction unit that performs a smoothing process on the binary data obtained by the binarization processing unit based on information to correct a step of an image. 2. The correction means includes storage means for storing the binary data obtained by the binarization processing means, and window forming means for forming a window from the binary data stored in the storage means. Pattern detecting means for detecting a specific pattern from the binary data in the window formed by the window forming means and the position information generated by the position information generating means, and the pattern detecting means based on the detection result of the pattern detecting means. The color image forming apparatus according to claim 1, further comprising a correction unit that corrects the value data. 3. The color image forming apparatus according to claim 2, wherein the pattern detection unit includes a storage unit that stores a pattern designated from the outside as the specific pattern. 4. The correcting means performs the smoothing processing in an area designated from the outside in the binary data obtained by the binarizing processing means. Color image forming apparatus. 5. A character detecting means for detecting a character portion of the image data is further provided, and the binarization processing means detects the character portion of the image data obtained by the rotation processing means by the character detecting means. 2 by thresholding the open area
5. The color image forming apparatus according to claim 1, wherein the correction unit performs binarization, and the correction unit performs smoothing processing based on a detection result of the character detection unit.