JPH02170673A - Digital color copying machine - Google Patents

Abstract

PURPOSE:To obtain a copy faithful to an original by providing first and second color correcting devices, a saturation discriminator, and a print signal selector and selecting print signals outputted from both color correcting devices by the print signal selector in response to a saturation color deciding signal and outputting the selected print signal. CONSTITUTION:A first color correcting device 3 inputs three-primary color picture signals 8 and three-primary color read state signals 7 and outputs a first print signal 10. A second color correcting device 4 outputs a second print signal 11 to the unsaturated color of three-primary color picture signals 8. Based on a saturation discriminator signal 9 outputted from a saturation discriminator 2, a print signal selector 5 outputs the first printing signal 10 as a print signal when at least one of three-primary color picture signals 8 is saturated, but the selector 5 outputs the second print signal 11 as the signal 12 when any three-primary color signal is not saturated. Color correction is performed in the second color correcting device 4 by a conventional technique and the first color correcting device 3 is used for saturated color in this manner. Consequently, the color reproducibility of saturated color is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a digital color copying machine capable of copying color originals.

BACKGROUND OF THE INVENTION FIG. 3 shows an example of the configuration of a conventional digital color copying machine.

In FIG. 3, 41 is a scanner, 42 is a color correction device,
43 is a printer, 44 is a three primary color image signal, and 45 is a print signal.

The operation of the digital color copying machine configured as described above will be explained below.

In FIG. 3, a scanner 41 is equipped with a sensor composed of an element that generates an electric charge depending on the intensity of light. The scanner 41 uses a sensor to optically read a document, obtain an output as an electrical signal, A/D convert the signal, and then output it sequentially for each pixel as three primary color image signals 44. When the scanner converts the electric signal output from the sensor into A/D, it does not judge whether it exceeds the range that can be converted into A/D. Outputs the maximum possible value of the signal. For example, for a sensor that outputs 0.0 volts when reading a document with a reflectance of 0%, and outputs io and o volts when reading a document with a reflectance of 80%,
When there was a conventional scanner that used a blts A/D converter to output 00us+ to FF161 for an input of 0.0 to 10.0 volts, it was possible to scan a document with a reflectance of 90% using that scanner. When read, the sensor is ■, 2
It outputs 5 volts, but as a result of A/D conversion, it outputs FF1116+ as a three primary color image signal. From now on, when the electrical signal output from the sensor is A/D converted, when the electrical signal exceeds the range that can be A/D converted, the maximum value is output as the three primary color image signal. This is expressed as "saturation." The color correction device 42 inputs the three primary color image signals 44 and adjusts the color correction device 45 so that the color difference between corresponding pixels between the original input from the scanner 41 and the copy output from the printer 43 is reduced. Output print signal. The printer 43 attaches the coloring material to the paper in response to the print signal 45.

Here, the color correction device 42 determines that the value of the three primary color image signals 44 is F.
When F++a+, the reflectance of the input document is
It is not possible to distinguish at all whether it was 80% or 90%, and no consideration has been given to the inability to distinguish.

Problems to be Solved by the Invention However, in a digital color copying machine configured as described above, when the scanner reads an original of a color with a high reflectance that saturates the three primary color image signals, the three primary color image signals output from the scanner is the maximum value. At this time, the color correction device performs color correction on the assumption that a document with a reflectance corresponding to the maximum value of the input three primary color image signals has been read by the scanner, and outputs a print signal. However, the actual color of the original is a color with a higher reflectance. If the ratio between the three primary color image signals changes due to saturation of some of the three primary color image signals, the expressed hue will change, so there is a problem that the colors of the original and the reproduction do not match. there were.

It is also possible to solve the above-mentioned problems by widening the range of A/D conversion when converting the electrical signal output from the sensor. However, when trying to reproduce good color even for special colors such as fluorescent colors, which modulate short wavelength light into long wavelength light and reflect it, it becomes difficult to reproduce normal colors that are not fluorescent colors.
Since it is not possible to obtain good color reproduction of fluorescent colors using the same color correction means, there has been a problem in that it is impossible to simply widen the range of reflectance that can be read by the sensor.

In view of the above-mentioned problem, the invention as claimed in claim 1 provides good color reproduction even when there are pixels in the document with a reflectance that exceeds the range of reflectance that can be read by a scanner. The purpose of this invention is to provide a digital color copying machine that can perform the following functions.

In addition, in view of the above-mentioned problems, the invention of claim 2 is also suitable for special colors such as fluorescent colors in manuscripts that modulate and reflect short wavelength light into long wavelength light. To provide a digital color copying machine capable of color reproduction.

Means for Solving the Problems In order to solve the above problems, a digital color copying machine according to the invention according to claim 1 is provided with a first color correction device, a second color correction device, a saturation determination device, and a print signal selection device. The first
A first print signal output from the color correction device and a second print signal output from the second color correction device are selected by a print signal selector in response to a saturated color determination signal output from a saturation determination device. It is equipped with a configuration for outputting.

In order to solve the above problem, a digital color copying machine according to the invention according to claim 2 includes a first color correction device, a second color correction device, a fluorescent color determiner, and a print signal selector, A print signal selector selects a first print signal output from the first color correction device and a second print signal output from the second color correction device in response to a fluorescent color judgment signal output from the fluorescent color judgment device. It has a configuration that allows it to be output.

The invention according to claim 1 has the above configuration, so that even if the pixel of interest has a color that has a reflectance higher than the reflectance that can be read by the scanner, the first color correction device can change the color that can be expressed by the printer. By expressing the image in colors that are close to those of the original, it is possible to make copies that are faithful to the original.

The present invention according to claim 2 has the above-described configuration, and in addition to the above-mentioned effects, it can also be used for special colors such as fluorescent colors in which the pixel of interest modulates short wavelength light into long wavelength light and reflects the same. By performing color correction for fluorescent colors with the first color correction device and expressing colors that are close to those of the original among the colors that can be expressed by the printer, it is possible to make a copy that is faithful to the original.

Embodiment Below, a digital color copying machine according to an embodiment of the invention as claimed in claim 1 will be described with reference to the drawings.

FIG. 1 is a schematic diagram of this digital color copying machine. In FIG. 1, 1 is a scanner, 2 is a saturation determiner, 3 is a first color correction device, 4 is a second color correction device, 5 is a print signal selector, 6 is a printer, and 7 is a state of reading three primary colors. signal, 8 is the three primary color image signal, 9 is the saturation determination signal, 10
is a first print signal, 11 is a second print signal, and 12 is a print signal.

The operation of the digital color copying machine configured as described above will be explained below with reference to FIGS. 1 and 4.

In FIG. 1, a scanner 1 optically reads a document. The scanner 1 is equipped with a sensor composed of an element that generates a charge depending on the intensity of light, and the reflectance of the document can be observed as an electrical signal using this sensor. Scanner 1 has three types of filters: red (R), green (G), and blue (B), and each pixel is passed through these three types of filters separately, and the reflectance is observed using a sensor. .

Information on the color of the pixel of interest can be read from the magnitudes of the three types of sensor outputs obtained through these filters and the ratio between the outputs. The scanner 1 performs 8-bit A/D conversion on the electrical signal output from this sensor and outputs it as a three primary color image signal 8 from the scanner. Hereinafter, each of the three primary color image signals 8 will be referred to as an R signal, a G signal, and a B signal, depending on the type of filter. Also, when A/D converting the electrical signal output from the sensor, it is determined for each of the three primary color image signals 8 whether it exceeds the range that can be A/D converted, and if it exceeds the range. If so, +11 is output as the three primary color reading status signal 7, and if not, °0' is output. Among the three primary color image signals 8, those that exceed the range that can be A/D converted when A/D converted become the maximum value (FF1161) of the possible values of the three primary color image signals. . From now on, in this way, the electrical signal output from the sensor will be converted to A/
When performing D conversion, outputting the maximum value as a three primary color image signal when the electrical signal exceeds the range that can be A/D converted is expressed as "saturating".

The first color correction device 3 inputs the three primary color image signal 8 and the three primary color reading status signal 7, and outputs a first print signal 10. The first color correction device 3 is realized by a look-up table (hereinafter referred to as LUT) which is a table of numerical values of seven types. FIG. 4 is a diagram for explaining these seven types of LUTs and their operations. Figure 4(a) shows the L U used when the 'B signal' of the three primary color image signals is saturated.
Figure 4(b) shows the LUT used when the 'R' signal of the three primary color image signals is saturated, and Figure 4(C) shows the LUT used when the 'G' signal of the three primary color image signals is saturated. Figure 4(d) shows the LUT used when the ``G signal'' and ``B signal'' among the three primary color image signals are saturated.Figure 4(e) shows the LU used when the ``B signal'' is saturated among the three primary color image signals. The LUT used when the 'R signal color' and the 'B signal' of the image signals are saturated. Figure 4(f) shows the 'R color of the three primary color image signals
L U used when the signal color "G signal" is saturated
T1 Figure 4 (g) shows the LU used when both the R multiplied signal, G signal, and 11B signal among the three primary color image signals are saturated.
It is T.

In the three primary color reading state signal 7, one signal has two states (O' and l'), and there are 8 (=23) combinations of the states of the three signals. If none of the three primary color image signals 7 are saturated, the second color correction device 4 is selected by the print signal selector 5, so if this is excluded, the 7
In some cases, seven types of LUTs are required. First 3
Based on the primary color reading status signal 7, information is obtained as to which of the three primary color image signals 8 is saturated, and it is determined which of the seven types of LUTs to use according to the information.

LU selected by the three primary color reading status signal 7
Using T, the first print signal 10 to be output is determined by searching the LUT with the remaining unsaturated signals among the three primary color image signals 7. For example, when the R signal of the three primary color image signals 8 is saturated,
) is selected.

At that time, the LUT is searched using the values of the G signal and B signal, which are the remaining unsaturated three primary color image signals 7. The set of values stored there is output as a first print signal.

Here, this LUT contains the three primary color image signals 8 for colors that are saturated when actually read by a scanner.
and the three primary color reading status signals 7, and at the location of the LUT determined by these values, print signal values that will visually approximate the saturated colors read by the scanner and expressed by the printer. It was constructed by searching for and storing this.

The second color correction device 4 reduces the color difference between corresponding pixels between the original input from the scanner 1 and the copy output from the printer 6 for colors in which the three primary color image signals 8 are not saturated. The second print signal 11 is output as shown in FIG. Specifically, this is achieved by calculating the second print signal 11 by performing a 3×3 matrix operation on the three primary color image signals 8.

The saturation determiner 2 inputs the three primary color reading status signals 7 output from the scanner 1, and if even one of them is +11, it will be '1', and if all the three primary color reading status signals 7 are O', it will be 101. is output as the saturation determination signal 9.

The print signal selector 5 selects the first print signal 10 as O when the saturation judgment signal 9 output from the saturation judgment unit 2 is 'I'.
', selects the second print signal 11 and prints the print signal 1.
Output as 2.

Therefore, if even one of the three primary color image signals 8 is saturated, the first print signal 1o is output, and if none is saturated, the second print signal 11 is output as the print signal 12. .

The printer 6 attaches the coloring material to the paper according to the print signal 12.

According to this embodiment, as described in "2" below, the first color correction device 3
and a second color correction device 4, the second color correction device 4 performs color correction using the conventional technology, and for saturated colors, the first color correction device 3 is used to correct the color of the pixel of interest. It is possible to output to the printer 6 a print signal that visually approximates the color when expressed by the printer 6, and it is possible to improve color reproducibility for saturated colors.

A digital color copying machine according to an embodiment of the invention as claimed in claim 2 will be described below with reference to the drawings.

FIG. 2 shows a digital color copying machine according to an embodiment of the second aspect of the present invention. In FIG. 2, 21 is a scanner, 22 is a fluorescent color determiner, 23 is a first color correction device, 24 is a second color correction device, 25 is a print signal selector,
26 is a printer, 27 is a three-primary color image (T-bow), 28 is a fluorescent color determination signal, 29 is a first print signal, 30 is a second print signal, and 31 is a print signal.

The operation of the digital color copying machine configured as described above will be explained below with reference to FIGS. 2 and 4.

In FIG. 2, a scanner 21 optically reads a document. The scanner 21 is equipped with a sensor composed of an element that generates an electric charge depending on the intensity of light, and the reflectance of the document can be observed as an electrical signal using the sensor. Scanner 21 uses red (
Three types of filters are prepared: R), green (G), and blue (B), and each pixel is passed through these three types of filters separately, and the reflectance is observed using a sensor. Information on the color of the pixel of interest can be read from the magnitudes of the three types of sensor outputs obtained through these filters and the ratio between the outputs. scanner 2
1, the electric signal output from this sensor is subjected to 8 blts A/D conversion and outputted from the scanner as a three primary color image signal 27. Here, when the electrical signal obtained as the output of the sensor is A/D converted, it is not determined whether it exceeds the range that can be A/D converted. However, if it exceeds the range that can be A/D converted, the maximum value (FF++e
+) is output.

The first color correction device 23 inputs the three primary color image signals 27 and first compares the three primary color image signals 27 with a threshold value. The threshold value is stored in the first color correction device 23 as a predetermined value. 3 primary color image signal 27
information on which of the signals exceeds the threshold,
A first print signal 29 is determined and output from among the three primary color image signals 27 that do not exceed the threshold value. in particular,
Seven types of LUTs are used as in the embodiment of item 1 of the present invention.
This is realized using

The second color correction device 24 uses the scanner 21 for normal colors in which all three primary color image signals 27 do not exceed the threshold values.
The second print signal 30 is output so that the color difference between corresponding pixels between the original input from the printer 6 and the copy output from the printer 6 is reduced. Specifically, this is achieved by calculating the second print signal 30 by performing a 3×3 matrix operation on the three primary color image signals 28.

The fluorescent color determiner 22 inputs the three primary color image signals 27,
A threshold value is used to determine whether the pixel of interest is a fluorescent color. The threshold value has the same value as the value held in the first color correction device 23.

If even one of the input three primary color image signals 27 exceeds the threshold value, the first print signal 29 is used, and if all of the three primary color image signals 27 exceed the threshold value, the second print signal 29 is used. A fluorescent color determination signal 28 for selecting the print signal 30 by the print signal selector 25 is output.

The print signal selector 25 responds to the fluorescent color determination signal 29 output by the fluorescent color determiner 22 and selects the first print signal 29 or the second print signal 29.
One of the print signals 30 is selected and outputted as a print signal 31.

The printer 26 attaches the coloring material to the paper according to the print signal 31.

As described above, according to this embodiment, even when the pixel of interest in the document is a special color such as fluorescent color, which modulates short wavelength light into long wavelength light and reflects it, the fluorescent color Judgment device 22
By determining the fluorescent color with the first color correction device and performing color correction for the fluorescent color with the first color correction device, copies with good color reproducibility can be made.

In addition, in the first embodiment and the second embodiment, the second color correction device 4 is realized by matrix calculation, but it may be realized by LUT.

Effects of the Invention As described above, the present invention provides a first color correction device, a second color correction device, a saturation determination device, and a print signal selector, so that the target pixel has a reflectance that can be read by a scanner. Even if the color has the above reflectance, it is possible to make a faithful copy of the original by expressing it in a color that is closest to the original color among the colors that can be expressed by the printer.

In addition, by providing the first color correction device, the second color correction device, the fluorescent color determiner, and the print signal selector, it is possible to convert short wavelength light into long wavelength light such that the pixel of interest is a fluorescent color. When the color is a special color that is modulated and reflected, the first color correction device performs color correction for the fluorescent color and expresses it with the closest color to the original among the colors that can be expressed by the printer. , it is possible to make faithful copies of originals.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a digital color copying machine according to an embodiment of the invention set forth in claim 1, FIG. 2 is a block diagram of a digital color copying machine according to an embodiment of the invention set forth in claim 2, and FIG. 3 is a block diagram of a conventional color copying machine. FIG. 4, a block diagram of a digital color copying machine, is an explanatory diagram of seven types of LUTs in the first color correction device in the embodiment of the present invention. 1.21.41...Scanner, 2...Saturation determiner,
3.23...First color correction device, 4.24...Second color correction device, 5.25...Print signal selector, 6, 26, 43...Printer, 7...・Three primary color reading status signal, 8.27.44... Three primary color image signal, 9... Saturation judgment signal, 10.29... First printing signal, 11.30... Second printing Signal, 12.31.45...Print signal. 22...Fluorescent color determination device, 28...Fluorescent color determination signal, 42...Color correction device. Name of agent: Patent attorney Shigetaka Awano (1 person) Figure 1

Claims (2)

[Claims] (1) The original is read optically, the signal obtained as an electrical signal is A/D converted, and the signal is output as a three primary color image signal, and when the electrical signal is A/D converted, the electrical signal is A scanner that outputs as a three primary color reading status signal whether or not the range that can be A/D converted is exceeded, and when the three primary color reading status signals are input and the electric signal is A/D converted by the scanner. Then, the electric signal determines whether there are any or one or more of the three primary color image signals that exceed the range that can be A/D converted, and outputs the determination result as a saturation determination signal. A saturation determination device inputs the three primary color image signals and the three primary color reading status signals, and determines which signals of the three primary color image signals in the input document exceed the range in which the electrical signals are A/D converted. a first color correction device that outputs a first printing signal that reduces a color difference between one or more pixels and a corresponding pixel of a copy; Outputting a second print signal that reduces the color difference between the pixel and the corresponding pixel of the copy for a pixel that does not have any signal that exceeds the range in which the electric signal is A/D converted. a second color correction device, which inputs the second print signal and the first print signal, and selects either the second print signal or the first print signal in response to the saturated color determination signal; 1. A digital color copying machine comprising: a print signal selector that selects only one of the print signals and outputs the selected print signal as a print signal; and a printer that inputs the print signal and prints the print signal. (2) A scanner that optically reads a document, A/D converts the signal obtained as an electrical signal, and outputs it as a three primary color image signal; A fluorescent color judger outputs as a fluorescent color judgment signal whether there is one or more signals whose value exceeds a certain threshold value or there are no signals; a first color correction device that outputs a first print signal that reduces the color difference between that pixel and the corresponding pixel of the copy for a pixel in which the value of the primary color image signal exceeds a certain threshold; , input the three primary color image signals, and calculate the color difference between that pixel and the corresponding pixel of the copy for pixels in the input document that do not have any signal whose value of the three primary color image signals exceeds a certain threshold value. a second color correction device that outputs a second print signal that becomes smaller, inputs the second print signal and the first print signal, and outputs the second print signal in response to the fluorescent color determination signal; and the first print signal, and a print signal selector that selects only one of the first print signals and outputs the selected print signal as a print signal, and a printer that inputs the print signal and prints.