JPH10285419A - Color image-forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain reproducibility of a hue of a fluorescent color and to obtain a copy object without dirt on the background by detecting the presence of a prescribed signal value from an image signal and controlling a reference voltage by an image read means, in the case of reading an image of an original. SOLUTION: An image input section 101 uses a high reference voltage, by which a read value of a fluorescent color is not saturated for a reference voltage at a preliminary scanning. In the case that a data value of a paper white part of a color image signal is detected and is discriminated that the fluorescent color is included in the original, main scanning is executed by adopting the high reference voltage for the preliminary scanning. A fluorescent color discrimination section 103 discriminates the fluorescent color, based on RGB signals received from the image input section 101. A background density identification section 104 sets a background level of the original, based on the RGB density signals received from a gradation conversion section 102. A background elimination section 105 eliminates the background based on a background density level signal received from the background density identification section 104, and a color correction section 106 converts the RGB density signal, whose background is eliminated, into CMYK signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a color image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in an image reading section of a color image forming apparatus, a portion which is brighter than the background of the document does not generally exist on the document and need not be read. Is 255 in the case of the maximum output of the scanner, for example, 8 bits, and the background portion is set not to be reproduced.

However, when a fluorescent color is painted on a document with a fluorescent pen or the like, a value of the fluorescent color portion is read larger (brighter) than the background. This is because the color of an ordinary document is determined only by the reflected light of the irradiated light, whereas the fluorescent color is determined by the light obtained by adding the reflected light of the reflected light and the fluorescent light emitted by itself. is there.

When such a fluorescent color is read by a conventional image reading apparatus or copied by a color copying apparatus, there is a problem that the fluorescent color is read and reproduced in a color different from the original. Further, not only the colors are different, but also a plurality of colors that are recognized as different colors by the human eye are reproduced as the same color, and a major problem has occurred in that important information of the distinguishability of the highlighter pen is lost. .

As a method of reading or reproducing a fluorescent color on an original, it is determined whether or not the original contains a fluorescent color, and based on the determination result, one of a fluorescent color parameter and a general color parameter is determined. (Japanese Unexamined Patent Publication No. Hei 7-177368) and an apparatus for reproducing a fluorescent color by switching a reference voltage for shading correction using a background level adjustment key (Japanese Unexamined Patent Publication No. Hei 6-334860).

[0006] Further, at the time of shading correction, a device for determining a fluorescent region by detecting a video signal larger than a white reference value (Japanese Patent Laid-Open No. Hei 7-23210),
There has been proposed an apparatus that distinguishes whether or not the color is fluorescent by comparing an input value of G with a predetermined threshold.

However, for example, Japanese Patent Application Laid-Open No. 6-334860.
In the device of No. 2, the background level of the document is instructed, and the reference voltage of the A / D converter is controlled in accordance with the level to prevent the saturation of the fluorescent color. The problem of being reproduced black occurred.

In order to solve this problem, there has been proposed a method of removing the background by setting a value equal to or less than a predetermined threshold value to 0. In this method, information of a fluorescent color indicating a value larger than the background is proposed. Is lost, and the hue changes.

[0009]

SUMMARY OF THE INVENTION The present invention is to provide a color image forming apparatus which solves the conventional drawbacks, maintains the reproducibility of the fluorescent color hue, and can obtain a copy without background stain. The purpose is to:

[0010]

According to the present invention, there is provided a color image forming apparatus for reading an image of a document and outputting the digital image signal as a digital color image signal, and a digital color image signal output from the image reading means. Detecting means for detecting the presence or absence of a signal value; control means for controlling a reference voltage at the time of reading the original image in the image reading means based on the detection result by the detecting means; and A density conversion means for calculating a density, detecting an achromatic portion, and converting the achromatic portion into a predetermined density value.

In the color image forming apparatus of the present invention, the predetermined signal value in the detecting means is a data value of a paper white portion of the digital color image signal. This is determined by comparing the data value of the white paper with the data value of the white paper.

[0012] The color image forming apparatus of the present invention further comprises a background density detecting means for detecting the background density in the density converting means;
A background removal unit that removes an achromatic background based on the detection result of the background density detection unit; the background density detection unit calculates the maximum RGB density value from the gradation-converted data of the digital color image signal When the maximum density value of RGB is equal to or less than a predetermined value, the background removing unit converts each of the RGB data to “0”.

[0013]

FIG. 1 shows an embodiment of a color image forming apparatus according to the present invention. The color image forming apparatus according to the present embodiment mainly includes an image input unit 101 as an image reading unit, a gradation conversion unit 102, a fluorescent color determination unit 103 as a detection unit, a background density identification unit 104 as a background density detection unit, Background removal unit 10 as background removal means
5, a color correction unit 106, and an image output unit 107.

The image input unit 101 has a CCD (not shown), and outputs image signals R and R of a color original coupled to the CCD.
The G and B color signals are read as multi-values from 0 to 255, for example.

The tone conversion unit 102 corrects the difference in sensitivity of the input CCD sensor corresponding to the image signals R, G, and B color signals input from the image input unit 101, and converts the density from the linear reflectance RGB signal. Performs conversion to linear signals.

The fluorescent color determination unit 103 includes an image input unit 101
And determines the fluorescent color based on the RGB signals input from the CPU, and sends the determination result to the color corrector.

The background density discriminating unit 104 includes a gradation converting unit 10.
The background level of the document is set on the basis of the RGB density signal input from Step 2 and the background level signal is output to the background removal unit 105.

The background removal unit 105 converts the RGB density signal input from the gradation conversion unit 102 into a background density identification unit 104.
And removes the background (R = G = B = 0) based on the background density level signal input from the CPU and outputs the result to the color correction unit.

The color correction unit 106 converts the RGB density signals from which the background has been removed by the background removal unit 105 into CMYK signals.
Output to the image output unit 107.

The image output unit 107 is composed of, for example, a laser printer, and receives the CMY input from the color correction unit 106.
Outputs K signal.

In this embodiment, background removal is performed before color correction, but background removal may be performed after color correction.

FIG. 2 is a block diagram showing an example of the detailed configuration of the image input unit 101. The image input unit 101 of this example mainly includes a CCD 201 serving as an image sensor,
A / D converter 202, shading correction circuit 20
3. It comprises a CPU 204 as a control means and a D / A converter 205.

The original is irradiated with light from a light source (not shown).
The reflected light is a color CCD 201 constituting an optical system.
Is imaged. The CCD 201 photoelectrically converts the formed optical image and outputs a converted analog electric signal.

An analog electric signal photoelectrically converted by the CCD 201 is input to an A / D converter 202 and converted into a digital multi-value signal. At this time, the reference voltage Vref
The conversion is performed based on the level input from + and Vref-. A variable digital value output from the CPU 204 is converted into an analog value by a D / A converter and applied to the reference voltage Vref +. Vref- is grounded.

By increasing the reference voltage Vref +, the readable range is widened, and it is possible to read a fluorescent color having an output higher than that of the paper white portion.

The shading correction circuit 203 corrects a light amount distribution of a light source (not shown) and a variation in sensitivity of each pixel of the CCD, and outputs the data subjected to the shading correction to the gradation conversion unit 102.

R, G, and R input from the image input unit 101
The value of B is a linear value of the reflectance, with 255 being the brightest color and 0 being the darkest color. Tone converter 102
Then, as shown in FIG. 3, the RGB signal having a linear reflectance is converted into an RGB signal having a linear density using a normal lookup table.

FIG. 4 shows an example of a circuit configuration of the fluorescent color judgment unit 103. A comparator is provided for each of the R, G, and B signals, and it is determined from the image signal after the shading correction whether a fluorescent color is included in the document. For fluorescent colors,
Since the output of the CCD 201 is larger than the paper white portion of the document, the CCD output of the paper white portion is set as the threshold L, and a document having an output larger than that value is determined to be a document containing a fluorescent color.

FIG. 5 shows a flow of the determining operation of the background density identifying unit 104. Data after gradation conversion is used for background density detection. When the back side of the document pressing plate (not shown) is black, the background portion of the document not containing the fluorescent color has the minimum density and the minimum value of the data after gradation conversion.

When a fluorescent color is included, the minimum value is smaller than the background value. However, in the case of a fluorescent color, the maximum density of RGB is higher than the background, and therefore, the minimum value in a portion where the maximum density of RGB is equal to or less than a certain threshold th is set as the background density.

The flowchart of the judgment operation will be described in detail.
First, it is determined whether or not the maximum density of RGB is equal to or less than the threshold th (step 501). If it is determined that the density is equal to or less than the threshold th, then it is determined whether or not the density x is greater than the minimum density of RGB (step 502). .

In step 502, when the density x is RGB
Is determined to be greater than the minimum density of RGB, that is, if the maximum density of RGB is equal to or less than the threshold th and the density x is greater than the minimum density of RGB, the density x is set to the minimum density of RGB (step 503), and the scan is terminated. (Step 5
04).

If it is determined in step 501 that the maximum density of RGB is equal to or greater than the threshold th, or
If it is determined in step 2 that the density x is smaller than the minimum density of RGB, the process proceeds to step 504 to end the scan.

FIGS. 6 to 9 show examples of the operation of the background removing unit 105. FIG. The background removal is performed in the RGB space, but in these examples, the description will be made in the RGB space. When each of RGB is compared with the threshold th and a value equal to or smaller than the threshold th is set to 0, a pixel including both R, G, or B larger than the threshold th and R, G, or B smaller than the threshold th is processed. The hue changes.

In order to prevent this, RG is used for each pixel.
The maximum density of B is determined, and the determination is made based on whether the value is equal to or less than a predetermined threshold. If the value is equal to or smaller than the threshold value, the pixel is converted to (R, G, B) = (0, 0, 0) as a paper white portion. If not, the input data is output as it is. In the case of the fluorescent color, since the maximum density is higher than that of the paper white portion, the RGB values are output as they are.

FIG. 10 is a flowchart showing the operation of the color image forming apparatus according to the present invention. First, a pre-scan is performed to check whether or not the original contains a fluorescent color and to determine the background density (step 1001).

At the time of pre-scanning, no image is formed. The original is read to determine whether or not a fluorescent color is included (step 1002), and only the background density level is set. Also,
In order to set the background density level, a high reference voltage at which the read value of the fluorescent color is not saturated is used as the reference voltage at the time of prescan.

According to the result of the fluorescence judgment by the prescan,
It is determined whether or not the reference voltage of the A / D converter 202 is to be changed (step 1002). If it is determined that the original does not contain a fluorescent color, the reference voltage is reduced to the reference voltage for normal reading of the original. The density level is also returned to the default value of the normal document (step 1003).

If it is determined in step 1002 that the original contains a fluorescent color, the main scan in step 1004 is executed with a high reference voltage at the time of prescan.

When the setting of the reference voltage and the background density level is completed, the main scan is executed (step 100).
4). In the main scan, an image is formed while removing the achromatic color background based on the set background density level. At this time, the color correction unit 106 converts the RGB signals into CMY
Conversion to a K signal is performed.

This color correction can be performed, for example, by the following calculation. C = Arc * R + Agc * G + Abc * B + Ac (1) M = Arm * R + Agm * G + Abm * B + Am (2) Y = Ary * R + Agy * G + Aby * B + Ay (3) K = Ark * R + Agk * G + Abk * B + Ak A ** and A * are predetermined constants.

[0042]

As is apparent from the above description, according to the color image forming apparatus of the present invention, a fluorescent color determining section for determining whether a fluorescent color is included in a document to be read, and an achromatic background Since the background density discriminating unit and the background removing unit for removing the image are provided, it is possible to accurately read a document containing the fluorescent color and a document not containing the fluorescent color. In addition, it is possible to reproduce a hue of the fluorescent color without losing the hue information, and to provide a copy without background stain.

In the fluorescent color determination section, the presence or absence of a fluorescent color in the original is determined by comparing the data value of the white portion of the digital color image signal with the digital color image signal. And a document which is not included in the document.

Further, the background density discriminating section calculates the maximum RGB density value from the gradation-converted data of the digital color image signal, and the background removing section calculates the RGB maximum density value when the RGB maximum density value is not more than a predetermined value. Each data of "0"
, It is possible to reproduce without losing the information on the hue of the fluorescent color, and to provide a copy without stain on the background.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of a color image forming apparatus of the present invention.

FIG. 2 is a block diagram illustrating an example of a detailed configuration of an image input unit 101.

FIG. 3 is a diagram illustrating an example of gradation conversion.

FIG. 4 is a diagram illustrating a circuit configuration example of a fluorescent color determination unit 103;

FIG. 5 is a flowchart of a determination operation of a background density identification unit 104;

FIG. 6 is an explanatory diagram illustrating an operation example of a background removal unit 105;

FIG. 7 is an explanatory diagram illustrating an operation example of a background removal unit 105;

FIG. 8 is an explanatory diagram showing an operation example of the background removing unit 105;

FIG. 9 is an explanatory diagram illustrating an operation example of the background removal unit 105.

FIG. 10 is a flowchart illustrating the operation of the color image forming apparatus.

[Explanation of symbols]

 Reference Signs List 101 Image input unit 102 Gradation conversion unit 103 Fluorescent color determination unit 104 Background density identification unit 105 Background removal unit 106 Color correction unit 107 Image output unit 201 CCD 202 A / D converter 203 Shading correction circuit 204 CPU 205 D / A converter

Claims (3)

[Claims] An image reading unit that reads an image of a document and outputs the digital color image signal as a digital color image signal; a detection unit that detects the presence or absence of a predetermined signal value from the digital color image signal output from the image reading unit; Control means for controlling a reference voltage at the time of reading the original image by the image reading means based on the detection result by the detection means; and calculating the density of each pixel from the data after gradation conversion of the digital color image signal, and And a density conversion unit for converting the achromatic portion into a predetermined density value. 2. The method according to claim 1, wherein the predetermined signal value is a data value of a paper white portion of the digital color image signal. 2. The color image forming apparatus according to claim 1, wherein the determination is made by comparing the data value of each of the sets. 3. The image processing apparatus according to claim 1, wherein the density conversion unit includes a background density detection unit that detects a background density, and a background removal unit that removes an achromatic background based on a detection result of the background density detection unit. The detecting means calculates a maximum density value of RGB from the data after the gradation conversion of the digital color image signal, and the background removing means separates each data of RGB when the maximum density value of RGB is equal to or less than a predetermined value. The color image forming apparatus according to claim 1, wherein the color image is converted into “0”.