JPH06225168A - Method for correcting color slippage of color picture - Google Patents

Abstract

PURPOSE:To improve the picture quality by preventing color slippage caused at a border between a color area and a black level area. CONSTITUTION:The method is provided with a filter section 51 comprising R, G, B, ND filters, a CCD section 52, a Y, M, C buffer memory 53, a BK picture memory 54, a picture processing section 55 for expanding a BK area or the like, an output picture memory 56, and a laser output section 57. An electric signal of a BK picture passing through the R, G, B, ND filters and detected at the CCD section is stored in the memory 54 and transferred to the picture processing section 55, in which the processing of BK area expansion is executed and the result is transferred to the output memory 56 and subject to copy output processing through the laser output section 57. No area expansion processing is applied to Y, M, C data and they are transferred to the laser output section 57 from the output memory 56, then the copy output processing is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color misregistration correction method for a color image, and more specifically, in a color copying machine, a color printer or the like, the boundary between a color (Y, M, C) area and a black (BK) area. The present invention relates to a method of correcting a color shift in a copy.

[0002]

2. Description of the Related Art In a color copying machine, an image is read by an optical system such as a scanner, and at that time, a color (Y: yellow, M: magenta, C: cyan) area and a black (BK:
A color shift may occur at the boundary with the black area. However, this color misregistration is problematic in that it is difficult to discriminate and correct the color difference during reading or in the memory, and the device becomes complicated and the cost increases. Therefore, in the conventional color copying machine, the Y, M, C, and
The value of BK was read from the memory as it was, and the toner was placed thereon, and there was no function for correcting the color misregistration.

[0003]

Problems to be Solved by the Invention (a), (b) of FIG.
Are cross-sectional views of the boundary portion of the Y, M, and C color areas and the BK area in the four-color copy, and the cross-sections drawn with diagonal lines are actually read by the optical system or the like. In FIG. 10A, the cyan (C) component is displaced toward the color area from the boundary portion, and this portion causes color misregistration. Further, in FIG. 6B, magenta (M) and cyan (C) are displaced to the color side from the boundary between the color (Y, M, C) area and the black (BK) area, and this portion is misregistered. Is causing.

FIG. 9 is a diagram for explaining the cause of the color misregistration of cyan (C) in FIG. 8A, assuming a black line having a width of several pixels on an original, When this is written in a sectional view, it becomes as shown in (a). This manuscript is divided into three Cs, each with R, G, and B filters.
I read using a CD sensor, but at the time of reading,
It is assumed that only red (R) is misaligned and read. Next, when outputting these R, G, B to C, M, Y,
If you write this in a cross-sectional view, it will look like Figure (c) (BK is the inking process), and the deviation of R (red) when reading the original is C
It appears as a deviation of (cyan). In the illustrated example, R
The deviation of C is the deviation of C, but this is the B of black ink
By enlarging K, it is possible to correct the mechanical color misregistration that occurs during reading and improve the image quality.

FIG. 10 is a diagram for explaining the above-mentioned color shift when black characters are written on the self paper, and FIG. 10 shows a case where the R component is read with a shift and a color shift of the C component occurs. For example, the red (R) component is misaligned and read in the portion B of FIG. 7A and the enlarged view of FIG.

The present invention has been made for the purpose of preventing the color shift occurring at the boundary between the color area and the black area as described above and improving the image quality.

[0007]

In order to solve the above-mentioned problems, the present invention provides (1) among image signals read by a CCD, black (BK) image information is stored in a black information memory and color image information is stored. Are respectively stored in the color information memory, and when the black information is black, the area of the black information is expanded, and when the black information is white, the area is output without being expanded from the output memory together with the color information. Alternatively, (2) among the image signals read by the CCD, black (BK) image information is stored in the black information memory, and color image information is stored in the color information memory, and Y (yellow) is stored for the color information. ), M
It is characterized in that which area (magenta) or C (cyan) is to be enlarged is determined and is output from the output memory together with the black information.

[0008]

In order to prevent the deviation occurring at the boundary between the color area and the black area, when the Y, M, C, and BK toners are placed, as shown in FIG. ,
By setting only the BK toner wider than the range read by the actual optical system or the like, specifically, as shown in FIG.
The BK toner is spread by several pixels wide in the character portion (BK area) on the portion painted in the pear-like pattern (the portion where the cyan (C) component is protruding). Alternatively, FIG.
As shown in (b), when Y, M, C, and BK toners are placed, one of Y, M, and C is wider than the range actually read by the optical system or the like (see FIG. In (b), a portion that is painted out in a pear-skin pattern) is provided to prevent color misregistration and further improve image quality.

[0009]

1 is a diagram for explaining an example of a digital color copying machine to which the present invention is applied. At the upper end of the copying machine 40, an original table 41 made of hard transparent glass is provided.
Is provided. A document (not shown) placed on the document table 41 is illuminated by the lamp unit 1, and the reflected light from the document passes through the mirrors 2, 3, 4 and the lens unit 5 and is reflected by the CCD sensor 6. It is guided to the light receiving surface and taken in as an electric signal. A scanner is composed of the lamp unit 1, the mirror 2, the CCD sensor 6 and the like. The image data taken in from the CCD sensor 6 is passed through the image processing section and the laser driver unit 7
To the photosensitive drum 10 which is output as laser light and is rotatable in the direction of arrow B through the mirrors 8 and 9.
An electrostatic latent image pattern is formed on it (exposure).

Photosensitive drum 10 rotatable in the direction of arrow B
A charging charger 16 for uniformly charging the surface of the photosensitive drum 10 prior to the exposure is provided in the rotation range of, and an electrostatic latent image is formed on the exposed portion by the laser output light.
Further, on the downstream side of the charging charger 16, a developing device including a black developing tank 11, a yellow developing tank 12, a magenta developing tank 13, and a cyan developing tank 14, and a transfer belt 1.
7, the cleaning unit 21, and the static elimination lamp 15 are arranged in this order. Toners of a corresponding color are stored in the developing tanks 11 to 14 of the developing device.

In the above arrangement, a color copy (3colo
r copy) is performed by the following operation procedure. When the charger 16 uniformly charges the surface of the photoconductor drum 10, the scanner performs the first scan, and the CCD
Image data captured by the sensor 6 (R, G, B)
Generates yellow data through both image processes, and is output as laser light from the laser driver unit 7 to expose the surface of the photosensitive drum to form a yellow electrostatic latent image on the exposed portion. Then, yellow toner is supplied from the yellow developing tank 12 to the electrostatic latent image in the image area, and a toner image of the same color is formed.

Next, the toner image moves in the direction of arrow B, and a part of the toner image is transferred onto the transfer belt 17 which is pressed against the surface of the photosensitive drum 10. At this time, a part of the toner that does not contribute to the transfer remains on the surface of the photosensitive drum 10,
The cleaning unit 21 scrapes off the residual toner. Then, the static elimination lamp 15 eliminates the residual charges on the surface of the photosensitive drum. When the above steps are completed, the charger 16
Again uniformly charges the surface of the photoconductor drum, and the data from the original obtained by the second scan is exposed by the laser beam through the image processing section to form a magenta electrostatic latent image. In the same manner, magenta toner is supplied to the electrostatic latent image from the magenta developing tank 13 to form a toner image of the same color. Then, this toner image is transferred to the transfer belt 17 and the images are superimposed.

Thereafter, when the same processing as described above is performed, the charging charger 16 charges the surface of the photosensitive drum again uniformly, and then cyan toner is supplied from the cyan developing tank 14 to the photosensitive drum 10 in the same manner. Toner image is formed. Then, this toner image is transferred to the transfer belt 17, and final image superposition is performed. After that, the toner image on the transfer belt 17 on which the images are superimposed is transferred to the copy sheet, passes through the fixing unit 31, and is ejected outside the apparatus by the ejection roller 32.

Further, the above-described process is a process for three-color, and in the case of a four-color process, black processing is added to this. On the other hand, in black-and-white copying, black toner is supplied to the electrostatic latent image on the photoconductor drum 10 from the black developing tank 11, and this toner image is transferred to the transfer belt 17.
It is carried out by transferring to a copy sheet via.

FIG. 2 is a block diagram for explaining an embodiment of the invention described in claim 1, in which 51 is R, G,
A filter unit composed of B and ND (corresponding to 5 in FIG. 1), 52
Is a CCD unit (corresponding to 6 in FIG. 1), 53 is a buffer memory for Y, M and C, 54 is an image memory for BK, and 55 is B.
An image processing unit for enlarging the K area, 56 is an image memory for output, and 57 is a laser output unit (corresponding to 7 in FIG. 1). The electrical signal of the BK image detected by the CCD unit through the four filters R, G, B and ND is stored in the memory 54 and transferred to the image processing unit 55. Here, the BK area expansion processing is performed, transferred to the output memory 56, and passed through the laser output unit 57 to be copy output processing. Y, M,
With respect to C, the area expansion processing is not performed, but the area is transferred from the output memory 56 to the laser output unit 57 and the copy output processing is performed.

FIG. 3 is a flowchart for explaining the operation of the invention described in claim 1 (see FIG. 4 for m and n in the figure), and the image data is Y, M, C, BK.
Are all binary. In S (step) 1, the document is scanned, and in S2 the document size is vertical M pixel, horizontal N pixel
Image address in the memory (m,
n). Initialization is performed in S3, the address starts from 0, and m = 1 and n = 1. Here, if the value of the data in the address is 1, it represents black, and if it is 0, it represents white.

The value BK (m, n) in the memory for BK in S4
= 1, that is, if the m-th vertical pixel and the n-th horizontal pixel are stored as black, the pixel at the same address in the output image memory and eight pixels ((m ± n, n-1) around it are stored in S5.
(M ± n, n) (m ± n, n + 1) (m, n ± 1) are all blacked. If white is determined in S4,
In S6, only the process of BK (m, n) = 0 in the output image memory is performed.

Next, in S7, it is judged whether or not the pixel in the process S4 is the right end of the image. If it is not the right end, n = S in S8.
The procedure of S4 to S6 is performed for the pixel on the right as n + 1. If it is the right end, in S9, it is determined in S10 whether the pixel is at the bottom position of the image. If it is the lowest, the copy is output in S11 as it is, otherwise n = 1.
To the initial setting (second pixel from the left), m = m
The processing moves to the next row as +1 and the processing of S4 to S6 is performed.

FIG. 5 is a block diagram for explaining an embodiment of the invention described in claim 2. As in the block diagram shown in FIG. 2, 51 is a filter section composed of R, G, B and ND, 52 is a CCD unit, 53 is a buffer memory for Y, M and C, 54 is an image memory for BK, 55 is an image processing unit for enlarging the Y, M and C regions, and 56 is an output memory.
7 is a laser output unit. The electric signal of the BK image detected by the CCD unit through the four filters of R, G, B, and ND is stored in the memory 54, and the Y, M, C images are stored in the memory 53. The image processing unit 5 determines which Y, M and C areas are to be expanded from the stored BK and Y, M and C data.
5, it is transferred to the output memory 56, and the copy output process is performed via the laser output unit 57.

FIG. 6 is a flow chart for explaining the embodiment of the invention described in claim 2 (see FIG. 7 for m and n in the figure), and the image data is Y, M, C, BK.
All are assumed to be binary. In S (step) 1, the document is scanned, and in S2 the document size is stored as vertical M pixels and horizontal N pixels. The image address in memory is (m,
n). In the present embodiment, since the determination is performed with the window size of 3 × 3, m = 1 in S3.1, S3.
In step 2, n = 1 is initialized. The judgment is not performed in the window centered on the outermost pixel. Further, the address starts from 0.

FIG. 6 shows an example of Y, and S
The case of the value Y (m, n) = 0 in the memory for YMC = 0 (the value of the Y component is 0 → there is a possibility of color misregistration) in 4 will be described. When all four equations are satisfied in S5, that is, in FIG. 7, addresses □ 1, □ 2, □ in the memory for BK
If all the data of 3, □ 4 (indicated by putting numbers in □ in FIG. 7) are black, no processing is performed and S
Go to 8. Process S5 is not established, that is, address □
When one or more white data are included in 1, □ 2, □ 3, □ 4, the determinations of processing S6.1 to S6.4 are made.

If the BK data at the address □ 1 in FIG. 7 is black in S6.1, the value of Y in the output memory is set in S7.1.
Y (□ 1) = Y (□ 3) and Y (m, n) = Y (□
3). This operation means expanding the color shifted to the color side to the black side in the sectional view of FIG. 8B. Similarly, in S6.2 and S6.3, if BK (□ 2) = 1, Y (□ 2) = Y (□ 4), Y (m, n) = Y (□ 4)
And In S6.3 and S7.3, if BK (□ 3) = 1, Y (□ 3) = Y (□ 1), Y (m, n) = Y (□ 1),
In S6.4 and S7.3, if BK (□ 4) = 1, Y (□
4) = Y (□ 2), Y (m, n) = Y (□ 2).
If all of S6.1 to S6.4 are not established, the process proceeds to S8.

In S8, it is judged whether or not the current 3 × 3 window centering on Y (m, n) is the right edge of the image.
If it is not at the right end, n = n + 1 is set in S12, and in the next processing, processing S4 and subsequent steps are performed when the window is shifted by one pixel to the right. If it is the right edge, it is determined in S9 whether the window is at the bottom, and if it is not at the bottom, S1
In 1, the next process shifts the window downward by one pixel, and S3.
In step 2, n = 1 is set, the address is moved to the left end + 1, and the processing from S4 onward is performed. If the window is at the bottom, the determination for Y is completed, and similarly for M and C, the processing from S3 onward is performed, and after Y, M, and C processing, copy output processing is performed at S10.

[0024]

As is apparent from the above description, according to the present invention, it is possible to easily prevent the color shift at the boundary between the color area and the black area and to improve the image quality.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an example of a digital color copying machine to which the present invention is applied.

FIG. 2 is a block diagram for explaining an embodiment of the invention described in claim 1.

FIG. 3 is a flowchart for explaining the operation of the embodiment shown in FIG.

FIG. 4 is a diagram for assisting the description of the flowchart shown in FIG.

5 is a block diagram for explaining an embodiment of the invention described in claim 2. FIG.

FIG. 6 is a flowchart for explaining the operation of the embodiment shown in FIG.

7 is a diagram for assisting the description of the flowchart shown in FIG.

FIG. 8 is a diagram for explaining a problem of a conventional technique and a method of solving the problem.

FIG. 9 is a diagram for explaining a problem of the conventional technique.

FIG. 10 is a diagram for explaining a problem of a conventional technique and a solution method thereof.

[Explanation of symbols]

1 ... Lamp unit, 2, 3, 4 ... Mirror, 5 ... Lens unit, 6 ... CCD sensor, 7 ... Laser driver unit, 8, 9 ... Mirror, 10 ... Photosensitive drum, 11 ...
Black developing tank, 12 ... Yellow developing tank, 13 ... Magenta developing tank, 14 ... Cyan developing tank, 15 ... Static elimination lamp, 1
6 ... Charging charger, 17 ... Transfer belt, 18 ... Transfer roller, 19 ... Registration roller, 20 ... Paper feed cassette, 2
1, 24, 27 ... Cleaning section, 21a, 24a, 2
7a ... Cleaning blade, 22, 25, 28 ... Exhaust toner receiver, 23, 26, 29 ... Auger shaft, 30 ... Conveyor belt, 31 ... Fixing section, 32 ... Ejection roller, 40 ... Copier, 41 ... Original document mounting table, 51 ... Filter, 52 ... CCD
Section, 53 ... YMC memory, 54 ... BK memory, 55
... image processing unit, 56 ... output memory, 57 ... laser output unit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mihoko Okada 22-22 Nagaikecho, Abeno-ku, Osaka, Osaka Prefecture

Claims (2)

[Claims] 1. Among image signals read by a CCD,
The black (BK) image information is stored in the black information memory, and the color image information is stored in the color information memory. When the black information is black, the area of the black information is enlarged, and when it is white, A color misregistration correction method for a color image, which is output from an output memory together with the color information without being enlarged. 2. Of the image signals read by the CCD,
The black (BK) image information is stored in the black information memory, and the color image information is stored in the color information memory. Regarding the color information, Y (yellow), M (magenta), and C are stored.
A color misregistration correction method for a color image, comprising determining which area of (cyan) is to be enlarged and outputting the same together with the black information from an output memory.