JP2002200786A - Color imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a color imaging apparatus producing a good image even if the fixing state of an LED print head is shifted without correcting that shift mechanically when the shift is small. SOLUTION: In order to correct shift in the fixing state of an LED print head, input signals to the LED print head is divided into a plurality of blocks in units of line. Signals of each divided block are fed to the LED print head at timings shifted sequentially line by line. In a line otherwise formed obliquely by an oblique LED print head, images divided into a plurality of blocks are joined while being shifted line by line to obtain a synthesized line of a plurality of blocks of image extending straight. Consequently, oblique fixing state of the LED print head is corrected electrically and a good image can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a color copying machine,
The present invention relates to a color image forming apparatus such as a color printer and a color facsimile, and more particularly, to a full-color image forming apparatus for forming an image by an electrophotographic method, the image forming apparatus having a plurality of so-called tandem type photosensitive drums. It is about.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus,
2. Description of the Related Art A color image forming apparatus called a tandem type, which has a photosensitive drum for each color of yellow, magenta, cyan and black and forms a full-color image by sequentially transferring toner images of each color onto transfer paper, is known.

[0003]

In this type of color image forming apparatus, an image of a different color is formed for each photosensitive drum, and the images are superimposed on paper. For this,
If an image misalignment occurs, a color misregistration occurs in the formed image, and a good image cannot be formed. Meanwhile, one of the causes of the image displacement is that there is a variation in the mounting state of a plurality of LED print heads provided in association with the respective photosensitive drums.

More specifically, it is assumed that four photosensitive drums are arranged in parallel in order to form four color images of yellow, magenta, cyan and black. Each of the photosensitive drums is provided with an LED print head for exposing the photosensitive drums. now,
For black photosensitive drum, black LED
It is assumed that the print head is mounted parallel to the rotation axis of the photosensitive drum. For the remaining yellow, magenta and cyan photoconductor drums, respectively,
Although the print heads are mounted in association with each other, these three LED print heads must also be mounted completely parallel to the rotation axis of the photosensitive drum.

However, no matter how precisely the LED printhead is mounted, mounting errors and assembly errors cannot be completely eliminated. That is, even if the LED print head is mounted with high accuracy, the LED print head is often displaced by about 200 μm between the front and rear sides with respect to the rotation axis of the photosensitive drum. If such a slight displacement is dealt with by correcting the mounting state of the LED print head, the assembling efficiency of the device is poor, and improvement in productivity cannot be expected.

Accordingly, the present invention provides a method for controlling an electric signal so that a slight displacement of about 200 μm or less does not affect an image to be formed when a mounting state of an LED print head to a photosensitive drum is displaced. An object of the present invention is to provide a color image forming apparatus for correcting a shift amount by signal processing.

[0007]

The invention according to claim 1 has a plurality of photosensitive drums, and a plurality of LED print heads provided in correspondence with the respective photosensitive drums. In a color image forming apparatus in which images of different colors are formed for each photosensitive drum and the images are transferred so as to be superimposed on paper, a predetermined position L
On the basis of the mounting state of the ED print head, a storage unit in which the displacement amount of the remaining LED print heads is stored, and based on the deviation amount stored in the storage unit, for each of the remaining LED print heads,
Means for dividing a signal input to the LED print head into a plurality of blocks in units of one line in order to correct a shift amount, and a method of sequentially shifting a signal of each divided block by one line at a time. And a means for applying to a head.

According to a second aspect of the present invention, there is provided processing means for performing a level difference correction on a signal at at least one end of each block in order to make a seam of an image of each divided block inconspicuous. 2. The color image forming apparatus according to claim 1, wherein: According to the first aspect of the present invention, the signal output from the LED print head is divided into a plurality of blocks based on the shift amount of the mounting state of the LED print head, and the signals are sequentially shifted by one line for each block. Is output. Accordingly, even if the LED print head is attached not obliquely to the rotation axis of the photosensitive drum but obliquely shifted,
One line in the main scanning direction exposed on the surface of the photoconductor drum by the ED print head is corrected not to be oblique to the rotation axis of the photoconductor drum but to be exactly parallel to the rotation axis.

[0009] Such correction is performed based on the mounting state of a specific LED print head. For example, if there are four photoconductor drums corresponding to four colors of yellow, magenta, cyan, and black, and each photoconductor drum is provided with an LED print head, for example, a black LED The print head is referenced. The reference LED print head is
The color is not limited to black, but may be other colors.

When the reference LED print head is mounted not slightly in parallel with the rotation axis of the photosensitive drum but slightly obliquely, the oblique state is used as a reference. LE to be a reference
The correction is performed in accordance with the reference LED print head mounting state so that a line overlapping the line formed by the D print head can be formed. Claim 2
In the configuration described above, the seam of the image for each divided block is not noticeable due to the step correction, and a straight and smooth line image can be formed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings. FIG.
1 is a diagram showing a schematic configuration of a tandem-type color copying machine according to an embodiment of the present invention. In the color copier 1,
An image reading unit 2 for reading an image of a document or the like, an image forming unit 3 for forming an image based on the read image, and a control unit 4 for controlling them are provided.

The image reading section 2 includes a platen glass 5 for placing a document, a light source 6 for illuminating the document placed on the platen glass 5, and a reflected light from the document illuminated by the light source 6. , A lens 8 for converging the guided light, and a CCD 9. The optical image signal reflected by the original is converted into an electric signal by the CCD 9 and supplied to the control unit 4. The image forming unit 3 includes four photosensitive drums 10Y, 10M,
10C, 10K and four developing rollers 11Y, 11M, 11C, 11K provided in association with the respective photosensitive drums.
And four LED print heads 12Y, 12M, 1
2C and 12K are provided. These four photosensitive drums 10 are arranged so as to be parallel to each other in the length direction of the paper transport belt 13.

Each of the photosensitive drums 10 has a cylindrical shape that is long in the direction perpendicular to the plane of the drawing, and the developing rollers 11 and the LED print heads 12 also have shapes that are long in the direction perpendicular to the plane of the drawing. . When the paper is transported from right to left in FIG. 1 along the transport belt 13, the paper is sequentially transferred to the photosensitive drums 10Y, 10M, 10C, and 10K.
, And yellow, magenta, cyan, and black toners are sequentially transferred, and the colors are superimposed to form a full-color image.

In the color copying machine 1, the control section 4 controls the LED print heads 12Y, 12M, 12C,
By controlling the output timing of the image forming signal for each color given to 12K (the lighting timing of the LED print head), the positional deviation of the image for each color can be adjusted. Hereinafter, a method of adjusting the image misregistration in the color copying machine 1 will be specifically described.

FIG. 2 shows an LED print head 12 for the photosensitive drum 10 in the color copying machine 1 shown in FIG.
FIG. 4 is an illustrative plan view showing a shift in a mounting state of the first embodiment. The LED print head 12K is attached to the photosensitive drum 10K for black without shifting. That is, the LED print head 12K is mounted in parallel with the rotation axis of the photosensitive drum 10K. On the other hand, the LED print heads 12 attached to the photoreceptor drums 10Y, 10M, and 10C respectively are attached.
None of Y, 12M, and 12C is mounted in a direction parallel to the rotation axis of the associated photoconductor drum, and slightly deviates from the rotation axis (indicated by a dashed line).

In such a case, the formed image is shifted. That is, as shown in FIG. 3, for example, when one line of black is compared with one line of cyan, the two lines do not completely overlap from one end to the other. Slightly shifted. Therefore, in this embodiment, as shown in FIG. 4, for each line of the cyan image formed by the LED print head 12C, one line of image data is written in the main scanning direction (the length direction of the LED print head 12C). By dividing the image data into a plurality of blocks (seven blocks in FIG. 4) and shifting the timing at which the image data of each block is applied to the LED print head 12C, a straight image not obliquely distorted as shown by a broken line can be obtained. It is to be. As a result, one line of cyan can be completely overlapped with one line of black, and image shift (color shift) can be corrected.

FIG. 5 shows an outline of the diagonal correction processing viewed from a different viewpoint from FIG. Since the oblique correction processing is performed based on the black image, the target is the LED print heads 12Y, 1Y for forming yellow, magenta, and cyan.
2M and 12C. The oblique correction processing is performed for each LED print head. Depending on how many lines the diagonal mounting of the LED print head for the correction extends over, one line depends on (the number of lines m + 1 required for diagonal mounting)
) Blocks. Then, the data of each block is sequentially shifted by one line and output. This allows
LED installed diagonally over m lines
The image to be formed diagonally by the print head is shifted line by line in block units, so m +
One straight, non-diagonal line consisting of one block is formed.

The "0th block" ahead in the main scanning direction
, The image data is output by shifting one line at a time, or the block data is output by shifting the line sequentially from the “m-th block” at the rear in the main scanning direction depending on which direction the LED print head is shifted. Can be switched. In this embodiment, the description is given on the assumption that the black LED print head 12K is mounted in parallel with the rotation axis of the black photosensitive drum 10K.
Is mounted slightly obliquely with respect to the photosensitive drum 10K, the obliquely mounted state is a reference. That is, the black LED print head 12K
Similarly to one line formed by the oblique mounting state of the LED print heads 12 of other colors,
An oblique correction process is performed so that Y, 12M, and 12C are also formed. As a result, the line images of the four colors are completely overlapped.

In the color copying machine 1 according to this embodiment, one line has 7168 dots. And L
The mounting position shift of the ED print head 12 is 200
If it is less than μm, the deviation is corrected by electrical processing. 200 μm, the resolution of the color copying machine 1 is 600d
If it is pi, it corresponds to 10 lines. Therefore, in this embodiment, the oblique correction for a maximum of 10 lines is performed. As a result, the number of correction lines, the number of divided blocks, and the number of pixels (dots) of the divided blocks have the relationship shown in FIG.

FIG. 7 shows an example of input data input to the control unit 4 and image data output from the control unit 4 to, for example, the yellow LED print head 12Y. FIG. 7 shows input data and output data when performing 10-line correction. Since data for each line is provided to the control unit 4, the input data is
The data is divided into 11 block data for 0-line correction (FIG. 7A). Then, the control unit 4 outputs, to the LED print head 12Y, the block data obtained by dividing the 11 lines of each line from the leading dot side to the last dot side, for example, while shifting one line at a time (FIG. 7B).

Alternatively, image data of 11 blocks is output while shifting one line at a time from the last dot side to the first dot side (FIG. 7C). Thereby, LE
As a result of the D print head 12Y being installed obliquely with respect to the rotation axis of the photosensitive drum 10Y, one line that should be oblique is corrected to form a straight line. By the way, one line obtained by performing the diagonal correction processing is configured by connecting a plurality of divided blocks, and a slight shift (step) occurs at the connection. Therefore, this step is made inconspicuous by the following step correction processing.

As shown in FIG. 8, each of the divided blocks is subdivided into eight filter blocks and unfiltered blocks. From the head dot side of the subdivided block, filter 0, filter 1,.
One filter block is composed of 64 pixels. Regardless of the number of lines to be corrected, it is a fixed value that the number of filter blocks and that one filter block is 64 pixels.

It should be noted that only the number of pixels of the filter 0 block may be made variable. In each filter block, FIG.
As shown in (1), each pixel of the target pixel line is corrected with reference to the previous line and the next line in the sub-scanning direction. The arithmetic expression of the filtering performed in this filter is as follows. Attention pixel data: Xn (m) (n: 0 to 63; 64 pixels) Reference pixel data: Xn (m-1), Xn (m + 1) Filter coefficients: a, b, c Attention pixel data after arithmetic processing = ( a * Xn (m-1) + b * Xn (m) + c * Xn (m + 1) +8) / 16 The filter coefficients a, b, and c are as shown in Table 1, and the upper eight values are In the case of sequentially outputting while shifting the line to the last dot side, the lower eight indicate coefficients when sequentially outputting while shifting the line to the first dot side.

[0024]

[Table 1]

By such a filtering process, the seam between the block data becomes inconspicuous, and a smooth and straight one-line image can be obtained. The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the claims.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a tandem-type color copying machine according to an embodiment of the present invention.

FIG. 2 illustrates a relationship between L and a photosensitive drum in a color copying machine.
FIG. 4 is an illustrative plan view for explaining a displacement of an attached state of the ED print head.

FIG. 3 is a diagram illustrating a shift between one black line and one cyan line.

FIG. 4 is a diagram illustrating an outline of a diagonal correction process.

FIG. 5 is a diagram illustrating an outline of a diagonal correction process viewed from a different viewpoint from FIG. 4;

FIG. 6 is a diagram illustrating a relationship among the number of correction lines, the number of divided blocks, and the number of pixels of a divided block.

FIG. 7 is a diagram illustrating an example of input data input to a control unit and image data output from the control unit.

FIG. 8 is a diagram schematically illustrating a divided block that is subdivided for step correction.

FIG. 9 is a diagram for explaining step correction.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Color copier 2 Image reading part 3 Image forming part 4 Control part 10Y, 10M, 10C, 10K Photoconductor drum 12Y, 12M, 12C, 12K LED print head

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/01 112 B41J 3/21 L 15/04 H04N 1/29 (72) Inventor Ryuichi Okumura Osaka, Osaka 1-2-28 Tamazo, Chuo-ku, Kyocera Mita Corporation F-term (reference) 2C162 AE12 AE47 AF13 AF24 AF60 AF62 AF73 FA04 FA17 2H027 DA23 EB06 EC06 ED04 EE07 EE08 FD08 ZA07 2H030 AA01 AB02 AD13 BB02 BB16 2H076 AB42 5C074 AA10 BB02 BB04 BB26 CC26 DD11 DD15 DD16 DD24 EE11 FF15 GG09 GG12 HH02

Claims (2)

[Claims] An image forming apparatus includes: a plurality of photosensitive drums; and a plurality of LED print heads provided in correspondence with the respective photosensitive drums, and forms images of different colors for each of the photosensitive drums. In the color image forming apparatus in which the LED print head is transferred so as to be superimposed on a sheet, a storage means for storing a shift amount of the remaining LED print head mounting state based on the mounting state of the LED print head at a predetermined position; Based on the amount of deviation stored in the storage means, the remaining LEDs
In order to correct the shift amount for each print head, the signal input to the LED print head is set to 1
A color image forming apparatus, comprising: means for dividing into a plurality of blocks in line units; and means for applying a signal of each divided block to an LED print head at a timing shifted sequentially by one line. 2. The image processing apparatus according to claim 1, further comprising processing means for performing a level difference correction on a signal of at least one end of each of the divided blocks so as to make a seam of an image in each divided block inconspicuous. Item 2. A color image forming apparatus according to Item 1.