JP2837418B2 - 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. 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 is provided a color image processing apparatus for converting an externally supplied digital color signal into a digital recording color signal and performing image processing. Density adjusting means for performing adjustment, color code generating means for generating a color code indicating the type of color of the digital color signal, and color reproducing means for correcting the digital color signal and converting it to a digital recording color signal. A digital color signal which is not adjusted in density by the density adjusting means is input to the color code generating means;
A digital color signal whose color balance has been adjusted by the density adjusting means is input to the color reproducing means.

(Operation) In the color image processing apparatus of the present invention, even if the digital color signal input to the color reproducing means is adjusted, the color code indicating the type of color is constant, so that good 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 standard density converter for converting red 8-bit digital data to 6-bit digital data; reference numeral 8 denotes an R adjustment density converter for converting red 8-bit digital data to 6-bit digital data while adjusting the density;
Is a G standard density converter for converting green 8-bit digital data to 6-bit digital data; 10 is a G adjustment density converter for converting green 8-bit digital data to 6-bit digital data while adjusting density; A B standard density converter 12 converts blue 8-bit digital data into 6-bit digital data, and a B adjustment density converter 12 converts blue 8-bit digital data into 6-bit digital data while adjusting density. Reference numeral 13 denotes a density adjustment circuit for adjusting the color balance. This density adjustment circuit 13 is for adjusting the color balance for each color. Reference numeral 14 denotes a color reproduction table for performing color code processing, color reproduction, and mono-color processing. Reference numeral 15 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 16 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. 1
Reference numeral 7 denotes a mono-color processing unit that receives data from the density adjustment circuit 13 and performs a mono-color process (a chromatic color such as a black character). 18 is a 6-bit Y, M,
A selector for selecting one of C, K, and mono-color data. 19 is an EE circuit for performing automatic density adjustment (EE),
Reference numeral 20 denotes a color ghost correction unit for performing color ghost correction, 21 denotes a main scanning direction color ghost detection unit that detects a color ghost in the main scanning direction, and 22 denotes a sub scanning direction color ghost detection that detects a color ghost in the sub scanning direction. Department,
23 is a memory for temporarily storing data of a plurality of pixels for color ghost correction, 24 is a color ghost removing unit for removing a detected color ghost, and 25 is a filtering process for performing a filtering process on a density signal. Unit, 26 is a scaling / shading processing unit that performs scaling processing and shading processing, 27 is a PWM multi-level conversion unit that converts a 6-bit density signal to multi-level by pulse width modulation (PWM), and 28 is Y, The printer unit forms a color image by sequentially superimposing toner images of respective colors of M, C, and K.

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 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 standard density converter and the adjusted density converter. The standard density converter converts 8-bit data into 6-bit data. In the adjustment density conversion unit, the color balance is adjusted by the density adjustment circuit 13 for each color,
The 8-bit data is converted to 6-bit data. That is, each adjustment density conversion unit adjusts the output level of each RGB according to the instruction from the density adjustment circuit 13. The output data of the RGB standard density conversion unit is applied to the color code processing unit 15, and the output data of the RGB adjustment density conversion unit is applied to the color reproduction unit 16. In the color code processing section, R, G,
As shown in FIG. 2, a color code indicating whether each pixel belongs to a color area of white / black / color is output according to the level of each data of B.

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 represent the concentrations of R, G, and 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. Further, the dotted area connecting white and black of the cube is an achromatic area. The area other than the white, black, and achromatic colors is determined to be a color area (chromatic color). Thus, white / black /
Generate a color code for determining the color.

Further, the color reproduction section 16 performs a color correction (R, G, B → Y, M, C) and an undercolor 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 monocolor processing section 17 creates 6-bit monocolor (achromatic) data from the output data of the A / D converter 4. The selector 18 selects and outputs YMCK or monocolor data in accordance with a color code indicating chromatic or achromatic color. Thereafter, color ghost removal, scaling, shading, and multi-value processing are performed, and image formation is performed by the printer unit 28. This printer unit 28
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. The 6-bit data from the R standard density conversion unit 7, the G standard density conversion unit 9, and the B standard density conversion unit 11 are applied to the color code processing unit 14 for creating a color code. The data level 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 unit 14 does not change. For this reason, even if the color tone of the image is changed by changing the color balance, the color code of the black portion of the read image remains the black color code. Therefore, when there are black characters or the like in the read original, the selector 18 selects the monocolor data from the monocolor processing unit 17 and outputs the data as black data. 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), the YMCK and the mono color are not switched, and only the YMCK output from the color reproducing section 16 passes through the selector 18. In this case, since the signal whose density has been adjusted is input to the color reproduction unit 16, 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 15 is configured not to generate a color code in a mode other than the four-color full-color normal mode.

Since the color ghost correction unit 20 detects the color ghost based on the color code, the color ghost correction is not performed in the mode in which no color code is created (four-color full-color photograph mode, mono-color mode). It is not necessary to perform color ghost correction in modes other than the four-color full-color normal mode, and in this case, no problem occurs.

As described above, the standard density conversion unit which is not affected by the color balance adjustment is provided separately from the adjustment density conversion unit which is affected by the color balance adjustment, so that the color code processing can be performed accurately. 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 formation is not used, and the superposition is performed on the electrophotographic photosensitive drum on which the 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 mirror 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 (not shown), a CCD 104 for capturing a red color separation image, a CCD 105 for capturing a green color separation image, and a CC for capturing a blue color separation image.
D106.

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. In this manner, 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.

Although the color copier has been described above, it goes without saying that the color image processing apparatus of the present invention can be used in other apparatuses for processing various color images.

(Effects of the Invention) As described above in detail, in the present invention, a digital color signal which is not affected by color balance adjustment is input to a color code processing unit, and color code processing is executed accurately. . Then, chromatic / achromatic colors are switched according to the color code. 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 showing a state of generating a color code of the present invention, and FIG. 3 is a configuration diagram showing an entire configuration of a color copying machine. is there. Reference Signs List 1 scanner unit 2 image reading unit 3,4,5 A / D converter 6 density conversion unit 7 standard R density conversion unit 8 R density adjustment unit 9 … G standard density converter 10… G adjustment density converter 11… B standard density converter 12… B adjustment density converter 13… Density adjustment circuit 14… Color reproduction table 15… Color code processor 16: Color reproduction unit, 17: Mono color processing unit 18: Selector, 19: EE circuit 20: Color ghost correction unit 21: Main scanning direction color ghost detection unit 22: Sub scanning direction color ghost detection Unit 23 Memory 24 Color ghost removal unit 25 Filter processing unit 26 Zooming / shading processing unit 27 PWM multi-value conversion unit 28 Printer unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 1/40-1/409 H04N 1/46-1/62 G03G 15/01

Claims (1)

(57) [Claims] 1. A color image processing apparatus for converting an externally supplied digital color signal into a digital recording color signal and performing image processing, comprising: density adjusting means for adjusting the color balance of the digital color signal; Color code generation means for generating a color code indicating the type of the color code; and color reproduction means for correcting the color of the digital color signal and converting the color signal into a digital recording color signal. A color image processing apparatus characterized in that a digital color signal whose density is not adjusted by means is inputted, and a digital color signal whose color balance is adjusted by said density adjusting means is inputted to said color reproducing means.