JP2637522B2 - Color image processing equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a color image processing apparatus, and more particularly, to a color image processing apparatus having excellent color reproducibility.

(Background of the Invention) A color image such as a character image or a photographic image is optically read by being divided into red R, green G, and blue B, and converted into recording colors such as yellow Y, magenta M, cyan C, and black K. (Color reproduction or color correction)
On the basis of this, there is a color image processing apparatus that records on a recording sheet using an output device such as an electrophotographic color copying machine.

(Problems to be solved by the invention) By the way, in such a color image processing apparatus,
In the case of performing color balance adjustment, there is a type in which density adjustment is performed at the R, G, and B stages. In such density adjustment, adjustment is performed by increasing or decreasing the density of each RGB color.

Adjust the color balance with the device as described above,
If any of the colors B is emphasized / reduced, the originally black portion becomes colored and achromatic portions such as black characters may be colored.

The present invention has been made in view of the above-described problems, and its purpose is to adjust the color balance,
An object of the present invention is to realize a color image processing apparatus which does not give achromatic colors.

(Means for Solving the Problems) According to the present invention for solving the above problems, there are provided a color code processing procedure for generating a color code indicating a color type of each pixel from a plurality of externally supplied digital color signals; A color reproducing means for converting a color signal into a plurality of digital recording color signals corresponding to recording colors by performing color correction, and converting each digital recording color signal output from the color reproducing means into a color from the color code processing procedure; Selector means for selectively passing according to a code.

(Operation) In the color image processing apparatus of the present invention, the color code processing procedure generates a color code based on the digital color signal, and the digital recording color signal of each color is selectively output by the selector means based on the color code. , And stable achromatic color reproduction is performed.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram showing the configuration of one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a scanner unit having an image reading unit and an A / D converter for reading a document image for each RGB and outputting the data as digital data of 8 bits for each RGB. Reference numeral 2 denotes an image reading unit for optically reading a document image; 3, an A / D converter for converting a red image signal read by the image reading unit 2 into 8-bit digital data; A / D converter for converting the green image signal read by the above into 8-bit digital data,
Reference numeral 5 denotes an A / D converter for converting a blue image signal read by the image reading unit 2 into 8-bit digital data.
Reference numeral 6 denotes a density conversion unit that converts RGB 8-bit digital data from the scanner unit 1 into 6-bit data. Reference numeral 7 denotes an R adjustment density conversion unit for converting red 8-bit digital data to 6-bit digital data while adjusting density, and reference numeral 8 denotes G adjustment for converting green 8-bit digital data to 6-bit digital data while adjusting density. A density conversion unit 9 is a B-adjustment density conversion unit that converts blue 8-bit digital data into 6-bit digital data while adjusting the density. Reference numeral 10 denotes a density adjustment circuit for adjusting the color balance. This density adjustment circuit 10
Is for adjusting the color balance for each color. Reference numeral 11 denotes a color reproduction table for performing color code processing, color reproduction, and mono-color processing. Reference numeral 12 denotes a color code processing unit that receives data from the R, G, B standard density conversion unit, determines white / black / color, and outputs a color code. Reference numeral 13 denotes a color reproduction unit that receives RGB data from the R, G, B adjustment density conversion unit and generates Y, M, C, K data. Reference numeral 14 denotes a mono-color processing unit that receives data from the density adjustment circuit 10 and performs a mono-color process (a chromatic color such as a black character).
Reference numeral 15 denotes a selector for selecting one of 6-bit Y, M, C, K, and monocolor data according to the color code. 16
Is an EE circuit for performing automatic and density adjustment (EE), 17 is a color ghost correction unit for performing color ghost correction, 18
Is a main scanning direction color ghost detection unit that detects a color ghost in the main scanning direction, 19 is a sub scanning direction color ghost detection unit that detects a sub scanning direction color ghost, and 20 is data of a plurality of pixels for color ghost correction. A memory for temporarily storing, 21 is a color ghost removing unit for removing a detected color ghost, 22 is a filter processing unit for performing a filtering process on a density signal, and 23 is a scaling process and a shading process. A scaling / shading processing unit, 24 is a PWM multi-value unit that multi-values a 6-bit density signal by pulse width modulation (PWM), and 25 is a toner image of each color of Y, M, C, and K sequentially superimposed. This is a printer unit that forms a color image by combining them.

In the following, after describing the overall schematic operation of the present embodiment, the main part of the present invention will be described.

The original image is read by the image reading unit 2 and is converted into an analog signal for each RGB. The analog signal is converted into 8-bit digital data by an A / D converter for each pixel. Then, the digital data of each of the RGB is supplied to the density conversion unit. In the density converter, 8-bit data is converted into 6-bit data while the color balance is adjusted by the density adjustment circuit 10 for each color. That is, in each density conversion unit, the output level of each RGB is adjusted according to the instruction from the density adjustment circuit 10.
The output data of the RGB density conversion unit is applied to the color code processing unit 11 and the color reproduction unit 13. The color code processing section outputs a color code indicating whether each pixel belongs to a color area of white / black / color, as shown in FIG. 2, according to the level of each data of R, G, B. I do.

FIG. 2 is an explanatory diagram showing the relationship between the density of the three primary colors of RGB read by the CCD of the reading means and the color code processing.
In this figure, the three sides on the near side of the cube are R, G,
It represents the concentration of B. Therefore, the point where the RGB co-density is 0 is white, and the point where the RGB co-density is maximum is black. The dotted area connecting white and black of the cube is an achromatic (monocolor) area. The area other than the white, black, and achromatic colors is determined to be a color area (chromatic color). In this way, a color code for determining white / black / color is generated.

Further, the color reproduction section 13 performs a color correction (R, G, B → Y, M, C) and an under color removal (Y, M, C → Y, M, C, K) in a correspondence table (lookup table). At the same time to create 6-bit data for each of YMCK. Further, the mono-color processing unit 14 creates 6-bit mono-color (achromatic) data from the output data of the A / D converter 4. The selector 15 selects and outputs YMCK or monocolor data in accordance with a color code indicating whether the color is chromatic or achromatic. Thereafter, color ghost removal, scaling, shading, and multi-value conversion are performed, and an image is formed in the printer unit 25. This printer unit 25
Is a method in which the toner images of Y, M, C, and K are sequentially superimposed on the photosensitive drum, and the image is read a plurality of times.

Next, the main part of the present invention will be mainly described. Selector means
Reference numeral 15 is configured to select a YMCK and a mono-color signal by a color code. At this time, even if the color balance of the image is changed by changing the color balance, a black (monocolor) color code is created in the black portion of the read image. Therefore, if there are black characters in the scanned original,
The selector 15 selects the mono-color data from the mono-color processing unit 14 and outputs the data as black data. At this time, the color reproduction unit 13 has created a colored black by color balance adjustment, but this signal cannot pass through the selector 15. Therefore, no color is applied to the black character portion (achromatic region).

The above description is based on the mode (4) for copying an image including black characters.
(Color full color normal mode). On the other hand, in the photo copying mode (four-color full-color photo mode), switching between YMCK and monocolor is not performed, and only the YMCK output from the color reproduction section 13 passes through the selector 15. In this case, since the signal whose density has been adjusted is input to the color reproduction unit 13, the color balance of YMCK also changes.
Naturally, the black parts are also colored. In the case of such a photographic image, unlike the black portion of the character, there is no problem even if the color changes according to the color balance adjustment. For this reason, the color code processing unit 12 does not generate a color code in a mode other than the four-color full-color normal mode.

As described above, a color code indicating the type of color (chromatic / achromatic) is created, and the color code is used to switch between YMCK / monocolor. Therefore, even if the color balance is adjusted, the color tone of the black characters does not change.

Next, the configuration and operation of each section of a color copying machine to which the color image processing apparatus of the present invention is applied will be described with reference to FIG. The color copier is developed using a color dry developing system. In this example, two-component non-contact development and reversal development are employed. That is, the transfer drum used in the conventional color image format is not used, and the superposition is performed on the electrophotographic photosensitive drum on which an image is formed. In the following example, in order to reduce the size of the apparatus, an OP for image formation is used.
A four-color image of yellow, magenta, cyan, and black is developed on the C photoconductor (drum) by four rotations of the drum, and transfer is performed once after development, so that the image is transferred to recording paper such as plain paper. .

The document reading unit A is driven by turning on the copy button of the color copier. Then, the platen 128
Is optically scanned by the optical system.

This optical system includes a carriage 132 provided with light sources 129 and 130 such as halogen lamps and a reflection mirror 131, and a V mirror 133.
And 133 'are provided.

The carriage 132 and the movable unit 134 are caused to travel on a slide rail 136 at predetermined speeds and directions by a stepping motor 135, respectively.

Optical information (image information) obtained by irradiating the original 101 with the light sources 129 and 130 is guided to the optical information conversion unit 137 via the reflection mirror 131 and the mirrors 133 and 133 '.

Standard white plate 138 on the back side of the left end of platen glass 128
Is provided. This is for normalizing an image signal to a white signal by optically scanning the standard white plate 138.

The optical information conversion unit 137 has a lens 139 and a prism 14.
0, two dichroic mirrors 102 and 103, a CCD 104 for capturing a red color separation image, and a green color separation image
It comprises a CCD 105 and a CCD 106 for capturing a blue color separation image.

Optical signals obtained by the optical system are collected by the lens 139, and color-separated into blue optical information and yellow optical information by the dichroic mirror 102 provided in the prism 140 described above. Further, the dichroic mirror 103 separates the yellow optical information into red optical information and green optical information. Thus, the color optical image is decomposed by the prism 140 into three-color optical information of red R, green G, and blue B.

Each color separation image is formed on the light receiving surface of each CCD, so that an image signal converted into an electric signal is obtained.
After the image signal is processed by the signal processing system, each color signal is output to the writing unit B.

As shown in FIG. 1, the signal processing system includes various signal processing circuits such as a color reproduction table, a color ghost correction unit, and a PWM multi-value conversion unit, in addition to the A / D converter.

The writing section B has a deflector 141. This deflector 1
As 41, a deflector made of an optical deflector using quartz or the like may be used in addition to a galvanometer mirror, a rotating polygon mirror, or the like. The laser beam modulated by the color signal
Deflection scanning is performed by 141.

When deflection scanning is started, beam scanning is detected by a laser beam index sensor (not shown),
Beam modulation by the first color signal (for example, a yellow signal) is started. The modulated beam is charged uniformly by the charger 154 to the image forming body (photosensitive drum)
It is made to scan over 142.

Here, the main scanning by the laser beam and the image forming body 142 are performed.
Due to the sub-scanning due to the rotation of
An electrostatic latent image corresponding to the color signal is formed.

This electrostatic latent image is developed by a developing device 14 containing yellow toner.
3 to form a yellow toner image.
Incidentally, a predetermined developing bias voltage from a high voltage source is applied to this developing device.

CPU for system control for toner supply to the developing unit
The toner replenishing means (not shown) is controlled based on a command signal from (not shown) so that toner is replenished when necessary. The above-described yellow toner image is rotated in a state where the pressure of the cleaning blade 147a is released, and a second color signal (for example, an electrostatic latent image is formed based on a magenta signal) in the same manner as in the case of the first color signal. .
Then, by using the developing device 144 that stores the magenta toner, the developing device 144 is developed to form a magenta toner image.

It goes without saying that a predetermined developing bias voltage is applied to the developing device 144 from a high-voltage power supply.

Similarly, an electrostatic latent image is formed based on the third color signal (cyan signal), and a developing device 145 containing cyan toner is formed.
As a result, a cyan toner image is formed. Further, an electrostatic latent image is formed based on the fourth color signal (black signal), and is developed by the developing device 146 filled with black toner in the same manner as the previous time.

Therefore, a multicolor toner image is formed on the image forming body 142 in an overlapping manner.

Here, the formation of a multicolor toner image of four colors has been described, but it goes without saying that a two-color or single-color toner image can be formed.

As described above, in the state where the AC and DC bias voltages are applied from the high-voltage power supply,
An example of so-called non-contact two-component jumping development in which each toner is caused to fly toward the image forming body 142 for development has been described.

The toner is supplied to the developing units 143, 144, 145, and 146 in the same manner as described above, and a predetermined amount of toner is supplied based on a command signal from the CPU.

On the other hand, the recording paper P fed from the paper feeding device 148 via the feed roll 149 and the timing roll 150 is the image forming body 1
The image forming body is synchronized with the rotation of 42.
Conveyed over 142 surfaces. Then, the multicolor toner image is transferred onto the recording paper P by the transfer pole 151 to which the high voltage is applied from the high voltage power supply, and is separated by the separation pole 152.

The separated recording paper P is conveyed to the fixing device 153, where a fixing process is performed to obtain a color image.

The image forming body 142 after the transfer is cleaned by the cleaning device 147, and is prepared for the next image forming process.

In the cleaning device 147, a predetermined DC voltage is applied to the metal roll 147b in order to easily collect the toner cleaned by the cleaning blade 147a.
The metal roll 147b is arranged on the surface of the image forming body 142 in a non-contact state. After the cleaning is completed, the cleaning blade 147a is released from the pressure contact.However, at the time of release, an auxiliary roller 147c is further provided to release unnecessary toner that is left, and the auxiliary roller 147c is rotated in a direction opposite to the image forming body 142, By pressing, unnecessary toner is sufficiently cleaned,
Removed.

(Effects of the Invention) As described above in detail, in the present invention, a color code indicating a color type is created, and the YMCK /
Changed to mono color. For this reason, it is possible to realize a color image processing apparatus in which an achromatic color is not formed even when the color balance is adjusted.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention, FIG. 2 is an explanatory diagram for explaining a state of color code generation, and FIG.
FIG. 1 is a configuration diagram showing the overall configuration of a color copying machine. DESCRIPTION OF SYMBOLS 1 ... Scanner unit, 2 ... Image reading part 3,4,5 ... A / D converter 6 ... Density conversion part, 7 ... R density conversion part 8 ... G density conversion part, 9 ... B Density conversion unit 10 Density adjustment circuit 11, Color reproduction table 12 Color code processing unit 13 Color reproduction unit 14, Mono color processing unit 15 Selector 16, FF circuit 17 Color ghost correction section 18 Color ghost detection section in the main scanning direction 19 Color ghost detection section in the sub-scanning direction 20 Memory 21 Color ghost removal section 22 Filter processing section 23 Zooming / shading processing Unit 24: PWM multi-level unit, 25: Printer unit

Claims (1)

(57) [Claims] 1. A color code processing means for generating a color code indicating the type of color of each pixel from a plurality of externally supplied digital color signals, and performing color correction on the plurality of digital color signals in accordance with a recording color. And a selector for selectively passing each digital recording color signal output from the color reproducing unit in accordance with a color code from the color code processing unit. A color image processing device characterized by the above-mentioned.