Color image forming device

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

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 the inclination of an image of each color.

【0002】

[Conventional technology]

Conventionally, in an image forming apparatus adopting an electrophotographic method, a photoconductor as an image carrier is charged by a charger, and the charged photoconductor is irradiated with light according to image information to form a latent image. This latent image is developed by a developer, and the developed toner image is transferred to a sheet material or the like to form an image.

【0003】

On the other hand, with the colorization of the image, a plurality of image forming stations in which the above-mentioned image forming processes are performed are provided, and each color image of a cyan image, a magenta image, a yellow image, preferably a black image is used as an image carrier. A tandem color image forming apparatus has also been proposed in which a full-color image is formed by forming and transferring each color image on a sheet material at a transfer position of each image carrier. Since such a tandem type color image forming apparatus has its own image forming unit for each color, it is advantageous for speeding up.

【0004】

However, there is a problem in how well the alignment (registration) of each image formed by different image forming portions is performed. An oblique position shift (hereinafter referred to as skew) occurs due to an angle shift of the rotation axis of the photoconductor drum in the image forming station and a mounting angle shift of the scanning optical system. This is because the deviation of the image formation positions of the four colors transferred to the sheet material or the like finally appears as a displacement or a change in color tone.

【0005】

Figure 20 shows an example of a skewed image. FIG. 20 (a) is an image rising to the right, and FIG. 20 (b) is an image falling to the right. The skew correction in the conventional color image forming apparatus will be described below.

【0006】

FIG. 21 shows a configuration 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 as bitmap data on the memory 63. The expanded bitmap data is binarized by halftone, dither, etc. by the binarization processing means 64. The skew correction means 65 corrects the deviation of the binarized image data.

【0007】

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

【0008】

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

【0009】

FIG. 23 is a diagram showing an example of an image shifted by 5 lines. FIG. 23 shows the skewed image of FIG. 20 (b).

【0010】

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

【0011】

The data correction means 69 divides one line into several blocks according to the amount of data deviation (number of lines), and corrects the entire deviation by shifting the divided blocks for each line.

【0012】

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

【0013】

FIG. 24 is a diagram showing a memory configuration of the data correction means of FIG. 22. Data is written in each block in units of 100 pixels. When looking at the data written on the 5th line, the printed data is off by 5 lines as shown in Fig. 23, so the data 70 on the 6th line in block 6 and the data 71 on the 5th line in block 5 By shifting the lines read out for each block for each line, an image with no apparent tilt is output.

【0014】

FIG. 25 is a block diagram of the data correction means of FIG. 22. Further, FIG. 26 is a timing chart showing the operation of the data correction means of FIG. 25.

【0015】

As shown in FIG. 25, the data correction means include a counter 72,73, a decoder 74,76, an adder 78,80 and a latch 79.

【0016】

The counter 72 is given a clock signal CK for each pixel synchronized with the data, a signal HSZ indicating the 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 to the memory of the data storage means 68.

【0017】

The read address will be described below. The counter 73 is given a signal HSZ indicating the period of one line, a clock signal CK, and a signal EQ described later. 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 in units of one pixel. The decoder 74 sets the reset signal RS to 1 when the count value of the counter 72 reaches 600 data in one line. As a result, the counter 72 is reset. The decoder 76 sets the signal EQ to 1 when the count value of the counter 73 reaches 100 data in one block. As a result, the counter 73 is reset.

【0018】

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

【0019】

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

【0020】

When the signal EQ is 1, the data shifts by 1 line, so if there are pixels before and after that, a step of 1 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. 22.

【0021】

FIG. 27 is a block diagram of the smoothing processing means of FIG. 22.

【0022】

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

【0023】

FIG. 28 is a block diagram of the pattern detecting means of FIG. 27. As shown in FIG. 28, the pattern detecting means 81 includes memory 83,84,93 and registers 85-90,94,95.

【0024】

The clock signal CK3 given 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 one line of data. Registers 85 to 90 latch the input data in response to the clock signal CK3. The data input by the memories 83, 84 and the registers 85 to 90 are shifted every half pixel, and a window consisting of 3 × 3 data D11 to D33 is formed. Further, the signal EQ is delayed by one line by the memory 93 and then given to the registers 94 and 95 in order. As a result, signals EQ1, EQ2, and EQ3 are generated in order.

【0025】

FIG. 29 is a configuration diagram of a window formed by the pattern detecting means of FIG. 28. In the example of FIG. 29, the conversion target data and the conversion target signal are DD22 and EQ.

【0026】

FIG. 30 is a block diagram of the pattern detection unit of the pattern detection means of FIG. 22. As shown in FIG. 30, the pattern detection unit 81a includes a discrimination table 91 and a comparator 92.

【0027】

The determination table 91 is written in advance in the ROM (read-only memory). The comparator 92 detects a pattern by comparing the data DD11 to DD33 and the signals EQ1, EQ2, and EQ3 of the window shown in FIG. 29 with the discrimination table 91, and outputs the memory 93 and the register 94 according to the detection result. To do.

【0028】

FIG. 31 is a block diagram of the data conversion means of FIG. 27. Further, FIG. 32 is a timing chart showing the operation of the data conversion means of FIG. 31.

【0029】

The data conversion means of FIG. 31 includes an AND circuit 98 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 calculates the logical sum of the output of the AND circuit 98 and the additional data output from the pattern detection unit 81a.

【0030】

As a result, as shown in FIG. 32, the step is corrected by adding and deleting small dots to the input data, and smoothed output data can be obtained.

【0031】

[Problems to be Solved by the Invention]

However, in the above-mentioned conventional color image forming apparatus, image quality deterioration occurs due to shifting the binarized data. For example, in the case of a natural image, the data becomes an array of regular patterns by performing gradation processing such as dither processing, error diffusion processing, and halftone processing at the time of binarization.

【0032】

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

【0033】

As shown in FIG. 33, 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 portion.

【0034】

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

【0035】

[Means for solving problems]

The image forming apparatus according to the present invention includes a rotation processing means that performs rotation processing of image data according to the inclination of an image for each color, and a position of a step in an image generated by the rotation processing in the image data obtained by the rotation processing means. It was generated by the position information generating means that generates the position information indicating the above, the binarizing processing means that obtains the binar data by performing the binarization processing on the image data obtained by the rotation processing means, and the position information generating means. It is provided with a correction means for correcting a step difference in an image by performing a smoothing process on the binary data obtained by the binarization processing means based on the position information.

【0036】

In the color image forming apparatus according to the present invention, image data is rotated according to the inclination of the image for each color, and in the obtained image data, position information indicating the position of a step in the image generated by the rotation is obtained. Occurs. In addition, the image data obtained by the rotation process is binarized, and the binar data is obtained. Then, smoothing processing is performed on the binary data based on the position information, and the step difference of the image is corrected.

【0037】

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

【0038】

BEST MODE FOR CARRYING OUT THE INVENTION

The color image forming apparatus according to the invention of claim 1 has a rotation processing means that performs rotation processing of image data according to the inclination of an image for each color, and an image generated by rotation processing in the image data obtained by the rotation processing means. A position information generating means that generates position information indicating the position of a step, a binarizing processing means that obtains binary data by performing a binarizing process on the image data obtained by the rotation processing means, and a position information generating means. It is provided with a correction means for correcting a step difference in an image by performing a smoothing process on the binary data obtained by the binarization processing means based on the position information generated by the above.

【0039】

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 in the obtained image data, the position information indicating the position of the step of the image generated by the rotation processing is obtained. Occurs. Further, the image data obtained by the rotation process is subjected to the binarization process, and the binar data is obtained. Then, smoothing processing is performed on the binary data based on the position information, and the step difference of the image is corrected.

【0040】

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

【0041】

In the configuration of the color image forming apparatus according to the invention of claim 1, the correction means is an accumulating means for accumulating binary data obtained by the binarizing processing means. , A specific pattern is detected from the window forming means that forms a window from the binary data accumulated in the storage means, the binary data in the window formed by the window forming means, and the position information generated by the position information generating means. It includes a pattern detecting means for modifying and a modifying means for modifying binary data based on the detection result of the pattern detecting means.

【0042】

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

【0043】

In the configuration of the color image forming apparatus according to the invention of claim 1 or 2, the pattern detecting means stores a pattern designated from the outside as a specific pattern in the configuration of the color image forming apparatus according to the invention of claim 3. It includes storage means.

【0044】

In this case, a specific pattern to be detected by the pattern detecting means can be easily changed and added, and highly accurate detection becomes possible.

【0045】

The color image forming apparatus according to the invention of claim 4 is the configuration of the color image forming apparatus according to the invention of claim 1, claim 2 or claim 3, and the correction means is obtained by the binarization processing means 2 Smoothing processing is performed in the area specified from the outside in the value data.

【0046】

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

【0047】

The color image forming apparatus according to the invention of claim 5 further includes a character detecting means for detecting a character portion of image data in the configuration of the color image forming apparatus according to any one of claims 1 to 4. The binarization processing means binarizes the image data obtained by the rotation processing means into the character portion and the area detected by the character detection means by the character detection means, and the correction means digitizes the detection result of the character detection means. The smoothing process is performed based on the above.

【0048】

In this case, it is possible to perform optimum correction on the character portion of the image data, and it is possible to improve the image quality of the character portion.

【0049】

(Embodiment 1) Hereinafter, the first embodiment of the present invention will be described with reference to FIGS. 1 to 12. FIG. 1 is a configuration diagram of a color image forming apparatus according to the first embodiment of the present invention.

【0050】

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

【0051】

In FIG. 1, four image stations 1a, 1b, 1c, 1d are arranged in the color image forming apparatus, and each image station 1a, 1b, 1c, 1d is a photoconductor 2a, 2b, 2c, 2d as an image carrier. Each has its own charging means 3a, 3b, 3c, 3d, developing means 4a, 4b, 4c, 4d, cleaning means 5a, 5b, 5c, 5d, and light according to the image information. The exposure means 6a, 6b, 6c, 6d of the scanning optical system for irradiating the photoconductors 2a, 2b, 2c, 2d of the above, and the transfer devices 8a, 8b, 8c, 8d in the transfer means 7, respectively, are arranged. ..

【0052】

Here, the image stations 1a, 1b, 1c, and 1d form a yellow image, a magenta image, a cyan image, and a black image, respectively, and the exposure means 6a, 6b, 6c, and 6d form a yellow image, a magenta image, and a cyan image, respectively. And light 9a, 9b, 9c, 9d corresponding to the black image is output. An unsupported belt-shaped intermediate transfer belt 12 supported by support rollers 10 and 11 is arranged below the photoconductors 2a, 2b, 2c, and 2d in a manner of passing through each image station 1a, 1b, 1c, 1d. , Move in the direction of arrow A. These operations are controlled by the control means.

【0053】

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

【0054】

In the above configuration, the image data generating means 13 gives the exposure means 6a, 6b, 6c, 6d the image information (image data) of each color.

【0055】

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

【0056】

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 forming station 1c, a cyan toner image with cyan toner is obtained by the developing means 4c, and the transfer device 8c is used. Is transferred and superposed on the black toner image previously transferred onto the intermediate transfer belt 12.

【0057】

Hereinafter, the magenta toner image and the yellow toner image are also image-formed in the same manner, and when the superposition of the four-color toner images on the intermediate transfer belt 12 is completed, the image is supplied from the paper cassette 15 by the paper feed roller 17. Toner images of four colors are collectively transferred and conveyed onto the sheet material 16 such as paper by the sheet material transfer roller 18, heated and fixed by the fixing means 19, and a full-color image is obtained on the sheet material 16.

【0058】

Residual toner is removed from the photoconductors 2a, 2b, 2c, and 2d that have been transferred by the cleaning means 5a, 5b, 5c, and 5d, and the printing operation is completed in preparation for the next image formation to be continued. ..

【0059】

A color image can be obtained as described above, but the mounting misalignment between each image forming station 1a, 1b, 1c, 1d and the scanning optical system occurs, and skew of each color occurs. Since the skew differs between the devices, the skew is measured from the output image when the devices are assembled and adjusted, and the deviation amount is written in advance in the deviation amount setting means 14 composed of ROM (read-only memory) or the like. Similarly, the deviation amount can be automatically detected, and the detected deviation amount is written in the deviation amount setting means 14.

【0060】

FIG. 2 is a block diagram of the image data generating means of FIG. The image data generating means 13 includes a memory 101, a rotation processing means 20, a binarization processing means 21, a position flag generating means 22, a pattern detecting means 23, a data conversion means 24, and an output means 25.

【0061】

In the present embodiment, the position flag generating means 22 corresponds to the position information generating means, and the pattern detecting means 23 and the data conversion means 24 correspond to the correction means. Further, the data conversion means 24 corresponds to the correction means.

【0062】

The multi-valued 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.

【0063】

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

【0064】

The rotation processing means 20 divides m data of one line into n blocks of the number of data b based on the shift amount n set in the shift amount setting means 14 (S1). Here, the number of data b in one block is as follows.

【0065】

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.

【0066】

Next, the final point (final pixel) of each block is calculated as the shift point SPi (S2). The shift point SPi is as follows.

【0067】

SPi = b × i (i = 1,2, ..., n) ... (2) As an example, if the number of data in one line is m = 1000 and the amount of deviation is n = 5, the number of data in one block is b = 200, and each shift point is SP1 = 200, SP2 = 400, SP3 = 600, SP4. = 800 and SP5 = 1000.

【0068】

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

【0069】

FIG. 4 is a flowchart showing the write address calculation process.

【0070】

First, after resetting, the pointers P1 and P2 are set to 0 (S4). Then add 1 to the address (S5). If the pointer P1 is different from the shift point SP1 (S6), 1 is added to the pointer P1 (S7), and the process returns to S5. If the pointer P1 is equal to the shift point SP1 (S6), add 1 to the pointer P2 (S8).

【0071】

Next, the value obtained by multiplying the number of data m in one line by the pointer P2 is added to the address (S9). At the same time, set the pointer P1 to 0 (S10) and return to S5.

【0072】

As a result, the address is shifted by one line for each block, and the address is shifted by n lines in the final block. Data is written to the memory 101 by the address generated in this way. The data written in the memory 101 are sequentially read out and binarized by the binarizing processing means 21 of FIG.

【0073】

FIG. 5 is a diagram showing binarization processing by the binarization processing means of FIG. The data for determining the binary level is written in the table TB in advance. Hereinafter, the data in the table TB will be referred to as table data.

【0074】

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

【0075】

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 counts the clock signal CK synchronized with the data read from the memory 101. The comparator 27 compares the count value of the counter 26 with the shift point SPi obtained by the rotation processing means 20, and generates a flag signal FL which becomes 1 when the count value and the shift point SPi are equal.

【0076】

At the shift point SPi, a step of one pixel is generated depending on the data, so the generated step is detected by the pattern detecting means 23 in FIG. 2 to smooth the data.

【0077】

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

【0078】

The clock signal CK2 given 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 sequentially stored in the memories M1 and M2 that store one line of data. Registers R1 to R6 latch the input data in response to the clock signal CK2. The data input by the memories M1 and M2 and the registers R1 to R6 are shifted every half pixel, and a window consisting of 3 × 3 matrisk data D11 to D33 is formed. Further, the flag signal FL is given to the registers R7 and R8 in order after being delayed by one line by the memory M3. As a result, the flag signals FL1, FL2, and FL3 are generated in order.

【0079】

FIG. 8 is a configuration diagram of a window formed by the pattern detecting means of FIG. 7. In the example of FIG. 8, the conversion target data and the conversion target flag signal are D22 and FL2.

【0080】

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

【0081】

The determination table 29 is written in advance in the ROM (read-only memory). The comparator 30 detects a pattern by comparing the window matrisk data DD11 to DD33 and the flag signals FL1, FL2, FL3 shown in FIG. 8 with the discrimination table 29, and adds and deletes additional data according to the detection result. Output data.

【0082】

FIG. 10 (a) shows an example of a data pattern in which a step of one pixel occurs in the sub-scanning direction, and FIG. 10 (b) shows an example of a data pattern after one clock time has elapsed.

【0083】

The discrimination table 29 contains several types of table data in which 12 flag signals FL1'to FL3'and matrisk data D11'to D33' corresponding to the flag signals FL1 to FL3 and the matrisk data D11 to D33 are set. Has been written.

【0084】

In FIG. 10 (a), as Table 1, FL1'= 0, FL2' = 0, FL'3 = 1, D11'= 1, D12'= 1, D13'= 1, D21' = 0, D22'= 0, D23'= 1, D31'= 1, D32'= 1, D33'= 0 are written. If the input flag signals FL1 to FL3 and matrisk data D11 to D33 are equal to the flag signals FL1'~ FL3' and data D11'~ D33' in Table 1, 1 is output as deletion data from the comparator 30. To.

【0085】

In FIG. 10 (b), as Table 2, FL1'= 0, FL2'= 1, FL3'= 0, D11'= 1, D12'= 1, D13'= 1, D21' = 0, D22'= 1 , D23'= 1, D31'= 1, D32'= 0, D33'= 0 are written. If the input flag signals FL1 to FL3 and matrisk data D11 to D33 are equal to the flag signals FL1'~ FL3' and matrisk data D11'~ D33' in Table 2, 0 is added as additional data from the comparator 30. It is output.

【0086】

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

【0087】

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

【0088】

As described above, according to the color image forming apparatus of the present embodiment, the image data is binarized after the tilt due to the skew of the image is corrected by the rotation process, so that the image pattern may be irregular. It is possible to obtain an image with high print quality.

【0089】

(Embodiment 2) Next, Embodiment 2 of the present invention will be described. FIG. 13 is a block diagram of a part of the pattern detecting means of the color image forming apparatus according to the second embodiment of the present invention.

【0090】

In the second embodiment, the pattern detecting means 23 is provided with registers 31 to 46 for setting a plurality of discrimination tables. Note that in FIG. 13, the registers 33 to 45 are not shown.

【0091】

The data of the discrimination table transferred from the outside is held in the registers 31 to 46 for each clock signal by the data of the external interface and the clock signal. By increasing the number of registers, it is possible to have a plurality of discrimination tables. This makes it possible to set the discrimination table from the outside. The configuration of other parts of the color image forming apparatus according to the second embodiment is the same as the configuration of the color image forming apparatus according to the first embodiment.

【0092】

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

【0093】

As shown in FIG. 14, the data conversion means 24 includes an AND circuit 47 and an OR circuit 48,49,50. An off signal that can be set from the outside is input to each of the input terminals of the OR circuits 48 and 49. The OR circuit 48 calculates the OR of the additional data and the off signal. The OR circuit 49 calculates the OR 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 calculates the OR of the output of the AND circuit 47 and the output of the OR circuit 49.

【0094】

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 other parts of the color image forming apparatus according to the third embodiment is the same as the configuration of the color image forming apparatus according to the first embodiment.

【0095】

In the color image forming apparatus of the present embodiment, when a defect occurs due to a detection error or the like, it is possible not to smooth the area of the data in which the defect has occurred.

【0096】

(Embodiment 4) Next, Embodiment 4 of the present invention will be described. FIG. 15 is a block diagram of the color image forming apparatus according to the fourth embodiment of the present invention.

【0097】

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

【0098】

FIG. 16 is a block diagram of the character detecting means according to the fourth embodiment of the present invention. As shown in FIG. 16, the character detecting means 51 includes a data storing means 52 and a determining means 53.

【0099】

The data storage means 52 stores the data rotated by the rotation processing means 20 of FIG. The determination means 53 determines whether or not the data input based on the data accumulated in the data storage means 52 is a character portion, and outputs the determination signal DT as 1 in the case of the character portion.

【0100】

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.

【0101】

The input data DL33 is sequentially stored in the line memories LM1 and LM2 that hold the data for one line. 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 are shifted for each pixel to form a window consisting of 3 × 3 data DL11 to DL33.

【0102】

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

【0103】

The determination means 53 in FIG. 16 determines that the data DL11 to DL33 of a total of nine windows formed by the data storage means 52 are character parts when three consecutive pixels are present in any of the vertical, horizontal, and diagonal directions. And set the judgment signal DT to 1.

【0104】

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.

【0105】

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

【0106】

The selector 56 selectively outputs the data output from the threshold processing unit 54 when the input data is the character part based on the determination signal DT, and when the input data is not the character part. Selectively outputs the data processed by the halftone / dither processing unit 55.

【0107】

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

【0108】

Further, in the data conversion means 24 of FIG. 15, when the determination signal DT is 0, the input data is output as it is. As a result, processing limited to the character part becomes possible, and higher image quality can be achieved when only characters are output or when character output is frequently used.

【0109】

[Effect of the invention]

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 and the inclination of the image is further increased. The correction can be performed smoothly, and a color image forming apparatus having high print quality can be obtained.

[Simple explanation of drawings]

[Figure 1]

Configuration diagram of the color image forming apparatus according to the first embodiment of the present invention. [Figure 2]

Block diagram of the image data generating means of FIG. [Fig. 3]

A flowchart showing the processing of the rotation processing means of FIG. [Fig. 4]

Flowchart showing write address calculation process [Fig. 5]

The figure which shows the binarization processing by the binarization processing means of FIG. [Fig. 6]

Block diagram of the position flag generating means in FIG. [Fig. 7]

Block diagram of the pattern detection means in FIG. [Fig. 8]

The block diagram of the window formed by the pattern detection means of FIG. [Fig. 9]

The block diagram of the pattern detection unit of the pattern detection means of FIG. [Fig. 10]

The figure which shows the pattern example in the pattern detection part of the pattern detection means of FIG. [Fig. 11]

Block diagram of the data conversion means in Fig. 2. [Fig. 12]

Timing chart showing the operation of the data conversion means of FIG. [Fig. 13]

A block diagram of a part of the pattern detecting means of the color image forming apparatus according to the second embodiment of the present invention. [Fig. 14]

Block diagram of the data conversion means of the color image forming apparatus according to the third embodiment of the present invention. [Fig. 15]

Block diagram of the color image forming apparatus according to the fourth embodiment of the present invention [Fig. 16]

Block diagram of the character detecting means according to the fourth embodiment of the present invention [Fig. 17]

Block diagram of the data storage means of the color image forming apparatus according to the fourth embodiment of the present invention. [Fig. 18]

Configuration diagram of the window formed by the data storage means of FIG. [Fig. 19]

Block diagram of the binarization processing means of FIG. [Fig. 20]

Diagram showing an example of a skewed image [Fig. 21]

Configuration diagram of image data generation means in a conventional color image forming apparatus [Fig. 22]

The block diagram of the skew correction means of FIG. 21 [Fig. 23]

Diagram showing an example of an image with a 5-line shift [Fig. 24]

The figure which shows the memory structure of the data correction means of FIG. 22 [Fig. 25]

Block diagram of the data correction means of FIG. 22 [Fig. 26]

Timing chart showing the operation of the data correction means of FIG. 25 [Fig. 27]

The block diagram of the smoothing processing means of FIG. 22 [Fig. 28]

Block diagram of the pattern detecting means of FIG. 27 [Fig. 29]

The block diagram of the window formed by the pattern detection means of FIG. 28 [Fig. 30]

The block diagram of the pattern detection unit of the pattern detection means of FIG. 22 [Fig. 31]

Block diagram of the data conversion means of FIG. 27 [Fig. 32]

Timing chart showing the operation of the data conversion means of FIG. 31 [Fig. 33]

(a) Diagram showing halftone processed data (b) Diagram showing the result of data shift [Explanation of symbols]

1a, 1b, 1c, 1d image station 2a, 2b, 2c, 2d Photoreceptor 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 transcript 9a, 9b, 9c, 9d light 10,11 Support roller 12 Intermediate transfer belt 13 Image data generation means 14 Misalignment amount setting means 15 Paper cassette 16 Sheet material 17 Paper feed roller 18 Sheet material transfer roller 19 Fixing means 20 Rotation processing means 21 2 Valuation processing means 22 Position flag generating means 23 Pattern detection means 24 Data conversion means 29 Discrimination table 30 Comparator 101 memory