JPH02158276A - Color image processor - Google Patents

Abstract

PURPOSE:To reproduce an achromatic color excellently by inputting a digital color signal which is not affected by color balance adjustment to a color code processing part and performing color code processing. CONSTITUTION:A color code processing part 15 for generating a color code is applied with 6-bit data from an R standard density conversion part 7, a G standard density conversion part 9, and a B standard density conversion part 11. The levels of those data do not vary even when color balance is changed, so no matter how the color balance is changed, the color code generated by the color code processing part 15 does not change. Consequently, even when the color tone of an image is changed by changing the color balance, the achromatic color area of a read image is never colored.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a color image processing device, and more specifically,
The present invention relates to a color image processing device with excellent color reproducibility.

(Background of the invention) Red R1 Green G for color images such as character drawings and photographic images.

It is divided into blue B and optically read, and this is yellow Y.

There is a color image processing apparatus that converts the image into a recording color such as magenta M, cyan C1 and black, and records the image on a recording paper using an output device such as an electrophotographic color copying machine based on the converted recording color.

(Problem to be Solved by the Invention) By the way, when performing color balance adjustment in such a color image processing device, R, G.

Some devices are designed to adjust the density at step B.

Such density adjustment is performed by increasing or decreasing the density of each RGB color.

Perform color balance adjustment using the above equipment, and adjust the RG
When any of the colors in B is emphasized/reduced, parts that are originally points become colored, and achromatic parts such as black characters may become colored.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to realize a color image processing device in which achromatic colors are not colored even when the color balance is adjusted.

(Means for Solving the Problems) The present invention solves the above problems in a color image processing device that performs image processing by converting externally applied digital color signals into digitally recorded color signals. It has a color code generation means for generating a color code indicating the type, and a color reproduction means for performing color correction on a digital color signal and converting it into a digital recording color signal, and the digital color signal input to the color code generation means and the color reproduction means are provided. This is characterized in that the digital color signal input to the color reproduction means is configured to be different.

(Function) In the color image processing apparatus of the present invention, even if the digital color signal input to the color reproduction means is manually adjusted, the color code indicating the type of color is constant, so that good reproduction of achromatic colors is performed.

(Example) Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing the structure of an embodiment of the present invention.

In the figure, 1 reads the original image for each RGB, and
This is a scanner unit that includes an image reading section and an A/D converter in order to output each image as 8-bit digital data. 2 is an image reading section for optically reading the original image; 3 is an A/D converter for converting the red image signal read by the image reading section 2 into 8-bit digital data;
A D converter, 4 converts the green image signal read by the image reading section 2 into 8-bit digital data, and 5 converts the blue image signal read by the image reading section 2 into 8-bit digital data. This is an A/D converter that converts the data into digital data. Reference numeral 6 denotes a density conversion unit that converts the RGB 8-bit digital data from the scanner unit 1 into 6-bit data. 7 is an R standard density converter that converts red 8-bit digital data to 6-bit digital data; 8 is an R-adjusted density converter that converts red 8-bit digital data to 6-bit digital data while adjusting the density; 9 1 is a G standard density conversion unit that converts green 8-bit digital data into 6-bit digital data.
0 is a G adjustment density conversion section that converts green 8-bit digital data into 6-bit digital data while adjusting the density; 11 is a B standard density conversion section that converts blue 8-bit digital data into 6-bit digital data; 12 1 is a B-adjustment density converter which converts blue 8-bit digital data into 6-bit digital data while adjusting the density. 13 is a density adjustment circuit for adjusting color balance. This density adjustment circuit 13 is for adjusting the color balance for each color. 14 is color code processing.

This is a color reproduction table that performs color reproduction and monochrome processing.

A color code processing section 15 receives data from the R, G, and B standard density conversion sections, discriminates white/black/color, and outputs a color code. 16 is R, G, B
After receiving the RGB data from the adjustment density converter of
This is a color reproduction section that generates M, C, and K data. 17
receives data from the density adjustment circuit 13 and converts monochrome (
This is a monochrome processing unit that processes chromatic colors such as black characters.

18 is each 6-bit Y according to the color code.

This is a selector that selects one of M, C, K, and monochrome data. 19 is an EE circuit for performing automatic density adjustment (EE); 20 is a color ghost correction section for performing color ghost correction; 21 is a main scanning direction color ghost detection section for detecting color ghosts in the main scanning direction;
2 is a sub-scanning direction color ghost detection unit that detects color ghosts in the sub-scanning direction; 23 is a memory for temporarily storing data of multiple pixels for color ghost correction; and 24 is a section for removing detected color ghosts. 25 is a filter processing unit that performs filter processing on the density signal; 26 is a scaling processing unit; the shaded area is a scaling/shaded processing unit that performs processing; 27 is a pulse width modulation (PWM)
28 is Y;

This printer unit forms a color image by sequentially overlapping M, C, and M toner images.

Hereinafter, the overall general operation of this embodiment will be explained, and then the present invention will be explained in detail.

The original image is read by an image reading section 2 and converted into analog signals for each RGB, and these analog signals are converted into 8-bit digital data by an A/D converter for each pixel. The R, G, and B digital data are then supplied to the standard density converter and the adjusted density converter. The standard density converter converts 8-bit data into 6-bit data. Further, in the adjusted density conversion section, the 8-bit data is converted into 6-bit data with the color balance adjusted by the density adjustment circuit 13 for each color. That is, in each adjusted density conversion section, the density adjustment circuit 13
The output levels of each of RGB are adjusted according to instructions from the controller. The output data of the RGB standard density conversion section is applied to the color code processing section 14, and the output data of the RGB adjusted density conversion section is applied to the color reproduction section 16. The color code processing unit outputs a color code indicating which color area (white, black, or color) each pixel belongs to, as shown in Figure 2, depending on the level of each R, G, and B data. .

Figure 2 shows the RGB 3 images read by the CCD of the reading means.
FIG. 3 is an explanatory diagram showing the relationship between the density of primary colors and color code processing. In this figure, the three sides on the front side of the cube are R, G,
It represents the concentration of B. Therefore, a point where the RGB co-density is 0 is white, and a point where the RGB co-density is maximum is black. Furthermore, the area indicated by the dotted line connecting the white and black parts of this cube is an achromatic area. Areas other than white, black, and achromatic colors are determined to be color areas (chromatic colors). In this way, a color code for determining white/black/color is generated.

The color reproduction unit 16 also performs color correction (R, G, B→Y, M
, C) and undercolor removal (Y, M, C4Y, M.

C, K) are performed simultaneously using a correspondence table (lookup table) to create data of 6 bits each for YMCK.

Furthermore, the monocolor processing section 17 creates 6-bit monocolor (achromatic color) data from the output data of the A/D converter 4. The selector 18 selects and outputs YMCK or monochrome data according to a color code indicating whether the color is chromatic or achromatic. After this, remove color ghost.

After scaling, shading, and multilevel conversion are performed, printer unit 2
Image formation is performed in step 8. This printer unit 28 sequentially overlays Y, M, C, and K toner images on the photosensitive drum, and image reading is also performed multiple times.

Next, the main parts of the present invention will be mainly explained. The color code processing section 14 for creating a color code includes an R standard density conversion section 7. 6-bit data from the G standard density converter 9°B standard density converter 11 is applied, and the level of these data does not change even if the color balance is changed. Therefore, no matter how the color balance is changed, the color code created by the color code processing section 14 does not change. Therefore, even if the color balance is changed to change the tone of the image, the color code of the dot portion of the read image remains the black color code.

Therefore, if there are black characters or the like in the read document, the selector 18 selects the monochrome data from the monochrome processing section 17 and outputs the black data as is. Therefore,
The black text area (achromatic area) will not be colored.

The above explanation is for a mode (four-color full-color normal mode) in which an image including black characters is copied. On the other hand, in the photo copying mode (four-color full-color photo mode),
Only the YMCK output from the color reproduction section 16 is allowed to pass through the selector 18 without switching between YMCK and monochrome. In this case, since the density-adjusted signal is input to the color reproduction section 16, the YMCK color balance also changes. Naturally, the black parts are also colored. This is because in the case of such a photographic image, unlike the black part of characters, there is no problem even if the color changes according to color balance adjustment. For this purpose, the color code processing unit 15
Color code should not be generated in modes other than full color normal mode.

Note that since the color ghost correction unit 20 detects color ghosts based on the color code, color ghost correction is not performed in modes in which no color code is created (four-color full-color photographic mode, monochrome mode). In modes other than the four-color full-color normal mode, there is no need to perform color ghost correction, and no problem occurs in this case either.

As described above, a standard density conversion section that is not affected by color balance adjustment is provided separately from the adjusted density conversion section that is affected by color balance adjustment, so that color code processing can be performed accurately. Therefore, even if color balance adjustment is performed, the tone of black characters does not change.

Next, the configuration and operation of each part of a color copying machine to which the color image processing apparatus of the present invention is applied will be explained with reference to FIG. Note that this color copying machine uses a color dry development method. In this example, two-component non-contact development and reversal development are employed.

In other words, the transfer drum used in conventional color image formation is not used, and the images are superimposed on the electrophotographic photosensitive drum that forms the image. In addition, in the following example, in order to downsize the device, four-color images of yellow, magenta, cyan, and black are developed on an OPC photoreceptor (drum) for image formation by four rotations of the drum, and then transferred after development. The image is transferred once to recording paper such as plain paper.

By turning on the copy button of the color copying machine, the original reading section A is driven. And the manuscript table 128
An original 101 is optically scanned by an optical system.

This optical system uses a light source such as a halogen lamp at 129° and 130°.
and a carriage 132 provided with a reflective mirror 131.
It is composed of a movable mirror unit 134 provided with V mirrors 133 and 133'.

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

Optical information (image information) obtained by irradiating the original 101 with the light sources 129 and 130 is transmitted to the reflecting mirror 131 and the mirror 1.
33, 133', the optical information conversion unit 137
guided by.

There is a standard white plate 1 on the back side of the left end of the platen glass 128.
38 are provided. This is because the image signal is normalized to a white signal by optically scanning the standard white plate 138.

The optical information conversion unit 137 includes a lens 139, a prism 140, two dichroic mirrors 102 and 103, a CCD 104 for capturing a red color-separated image, a CCD 105 for capturing a green color-separated image, and a blue color-separated image. It is composed of a CCD 106 to be imaged.

The optical signal obtained by the optical system is collected by the lens 139, and separated into blue optical information and yellow optical information by the dichroic mirror 102 provided in the prism 140 described above. Furthermore, dichroic mirror 103
The yellow optical information is color-separated into red optical information and green optical information.

In this way, the color optical image is decomposed by the prism 140 into three-color optical information of red, R, green, and blue.

Each color separation image is formed on the light receiving surface of each CCD, thereby obtaining an image signal converted into an electrical signal.

After the image signal is processed by the signal processing system, each color signal is output to the writing section B.

As shown in FIG. 1, the signal processing system includes various signal processing circuits such as an A/D converter, a color reproduction table, a color ghost correction section, and a PWM multilevel conversion section.

The writing section B has a deflector 141. As this deflector 141, in addition to a galvanometer mirror, a rotating polygon mirror, etc.
A deflector consisting of an optical deflector using crystal or the like may be used. The laser beam modulated by the color signal is deflected and scanned by this deflector 141.

When deflection scanning is started, beam scanning is detected by a laser beam index sensor (not shown), and beam modulation using a first color signal (for example, a yellow signal) is started. The modulated beam is applied to an image forming member (photosensitive drum) 1 which is charged with a negative charge by a charger 154.
Here, main scanning by the laser beam and image forming body 142 are performed.
Due to the sub-scanning caused by the rotation of the image forming member 142, an electrostatic latent image corresponding to the first color signal is formed on the image forming body 142.

This electrostatic latent image is transferred to a developing device 14 containing yellow toner.
3 to form a yellow toner image.

Note that a predetermined developing bias voltage from a high voltage source is applied to this developing device.

Toner replenishment for the developing unit is done by the CPU for system control.
A toner replenishing means (not shown) is controlled based on a command signal from a toner replenishing means (not shown), so that toner is replenished when necessary. The yellow toner image described above is rotated with the cleaning blade 147a released from pressure, and an electrostatic latent image is formed based on a second color signal (for example, a magenta signal) in the same manner as in the case of the first color signal. .

Then, by using a developing device 144 containing magenta toner, this is developed to form a magenta toner image.

Needless to say, a predetermined developing bias voltage is applied to the developing unit 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 provided.
A cyan toner image is formed. Further, an electrostatic latent image is formed based on the fourth color signal (black signal), and is developed in the same manner as the previous time using the developing device 146 filled with black toner.

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

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

As described above, the development process is a so-called non-contact two-component development process in which each toner is ejected toward the image forming body 142 while AC and DC bias voltages from a high-voltage power source are applied. An example of jumping development is shown.

Toner replenishment to the developing units 143, 144, 1.45, and 146 is performed based on a command signal from the CPU as described above, and a predetermined amount of toner is replenished.

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 conveyed onto the surface of the image forming body 142 in a state in which the timing is synchronized with the rotation of the image forming body 142. Ru. Then, the multicolor toner image is transferred onto the recording paper P by the transfer pole 151 to which a high voltage is applied from the high voltage power source, and the polarized M pole 152
separated by

The separated recording paper P is conveyed to the fixing device 153, where it undergoes a fixing process and a color image is obtained.

The image forming body 142 after the transfer is transferred to a cleaning device 147
is cleaned and prepared for the next imaging process.

In the cleaning device 147, a predetermined DC voltage is applied to the metal roll 147b in order to facilitate recovery of the toner cleaned by the cleaning blade 147a. This metal roll 147b is placed on the surface of the image forming body 142 in a non-contact state. cleaning blade 1
47a is released from pressure bonding after cleaning is completed, but in order to release unnecessary toner that is left behind at the time of release, an auxiliary roller 147c is further provided, and this auxiliary roller 147c is rotated in the opposite direction to the image forming body 142 and pressed. As a result, unnecessary toner is sufficiently cleaned and removed.

Although a color copying machine has been described above, it goes without saying that the color image processing apparatus of the present invention can be used in various other devices that process color images.

(Effects of the Invention) As explained in detail above, in the present invention, a digital color signal that is not affected by color balance adjustment is input to the color code processing unit, and color code processing is accurately executed. .

Then, I switched between chromatic and achromatic colors according to this color code. Therefore, it is possible to realize a color image processing device in which achromatic colors are not colored even if the color balance is adjusted.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is an explanatory diagram showing how a color code is generated according to the present invention, and FIG. 3 is a block diagram showing the overall configuration of a color image copying machine. It is. 1... Scanner unit 2... Image reading section 3.
4.5...A/D converter 6...Density converter 7...R standard density converter 8...R adjustment density converter 9...G standard density converter 10...G Adjusted density conversion unit 11...B standard density conversion unit 12...B adjusted density conversion unit 13...Density adjustment circuit 14...Color reproduction table 15...Color code processing unit 16...Color reproduction Section 17... Monocolor processing section 18... Selector 19... EE circuit 20
...Color ghost correction section 21...Main scanning direction color ghost detection section 22...
Sub-scanning direction color ghost detection section 23...memory 24...color ghost removal section 25...filter processing section 26...magnification/shading processing section

Claims (1)

[Scope of Claims] In a color image processing device that performs image processing by converting a digital color signal provided from the outside into a digitally recorded color signal, a color code generation means for generating a color code indicating the type of color of the digital color signal. and color reproduction means for performing color correction on the digital color signal and converting it into a digitally recorded color signal, the digital color signal input to the color code generation means and the digital color signal input to the color reproduction means being different. A color image processing device characterized by being configured as follows.