JPH0810902B2 - Multicolor recorder - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor recording device such as a printer, a facsimile, a copying machine or the like for recording a color image having gradation.

2. Description of the Related Art In a general multicolor recording apparatus, a color image having a gradation is recorded by recording four color images including a black plate in an overlapping manner.

FIG. 3 is a circuit diagram of a conventional multicolor recording apparatus. Reference numeral 1 is a comparator for comparing the magnitudes of yellow, magenta, and cyan input signals obtained from terminals Y, M, and C, and 2 is an output from the comparator 1. A multiplexer 3 which outputs the smallest color input signal, a black ink data memory 3 which converts the input signal output from the multiplexer 2 into a black plate recording signal, and stores the black plate recording signal 4, a lower color removal signal 4 Under color removal data memory for conversion and storage into 5,
Reference numerals 6 and 7 denote subtractors which perform arithmetic operations from the input signals obtained from the terminals Y, M and C and the data of the lower color removal data memory 4 and output the recording signals of three colors.

The operation of the conventional multicolor recording apparatus configured as described above will be described below.

Now, the density of the yellow, magenta, and cyan input signals obtained from the terminals Y, M, and C are respectively set to YD, MD, and CD.
And The output of black plate data memory 3 has a coefficient for its input.
The output of the undercolor removal data memory 4 is obtained by multiplying its input by a coefficient K2.

Generally, if undercolor removal is done over 100%,
The coefficient K2 is set to a value smaller than 1 because it is difficult to match the other three colors and the saturation is reduced in the low density portion. In addition, the black plate amount is a coefficient of the black plate amount from the coefficient K2 of the undercolor removal because the additive rule and the synergistic rule of density do not hold.
K1 has a large value. Therefore, in general, coefficient K1, coefficient
The relationship between K2 and the density of the input signal is as shown in the graph of FIG.

Assuming now that the density relationship of the input signal is YD>MD> CD, the output of the multiplexer 2 is CD, the black plate recording signal is CD × K1, and the yellow recording signal is YD.
The recording signal of −CD × K2 and magenta is MD-CD × K2, and the recording signal of cyan is MD-CD × K2.

As an example, as shown in FIG. 5A, the density of the input signal is YD = 1.60, MD = 1.55, CD = 1.50, and the coefficient value is K1 =
Assuming that 0.6 and K2 = 0.5, the black printing signal has a density of 0.90 and the yellow printing signal has a density of 0, as shown in FIG.
85, the density of the recording signal for magenta is 0.80, and the density of the recording signal for cyan is 0.75.

Problems to be Solved by the Invention However, in the above-described conventional configuration, when the input signal is close to black with high density, as described in the example, 4
Each color recording signal is recorded as a medium density signal. Here, generally, in a color multicolor recording apparatus, recording of four colors is not performed at the same time, so a deviation of four colors is inevitable. In the case of recording pictures, photographs, etc., this deviation is not noticeable and often does not pose a problem, but in the case of an image with many lines such as characters, the image quality is significantly deteriorated as shown in FIG. 5 (c). Will give rise to points.

MEANS FOR SOLVING THE PROBLEMS The present invention provides a comparing means for comparing the density indicated by a black plate recording signal with a set density, and a recording signal for a black plate when the density indicated by the black plate recording signal is larger than a set value. It is provided with a conversion means for converting the signal into only a signal.

Operation With the above configuration, when the input signal is close to black, recording is performed only with the black plate recording signal, and there is no deviation in the four colors.

Example 1 FIG. 1 is a circuit diagram of a multicolor recording apparatus according to an example of the present invention, in which 1 is a comparator, 2 is a multiplexer,
3 is a black plate data memory, 4 is an undercolor removal data memory,
Reference numerals 5, 6, and 7 are subtractors, which are the same as those in the conventional example. Reference numeral 8 is a comparator for comparing the black plate recording signal with the set value s, and 9 to 12 are 4 color recording signals when the black plate recording signal output from the comparator 8 is larger than the set value. The preset recording signal a-
2 is output, and conversely, when the output of the comparator 8 indicates that the black plate recording signal is smaller than the set value, it is a multiplexer that directly outputs the black plate recording signal and the three-color recording signal. Since ~ d is set to 0, when the black plate recording signal is larger than the set value, the black plate alone is used for recording.

As an example, the density of the input signal is YD = 1.60, MD = 1.55, CD = 1.5 as in the conventional example, as shown in FIG.
0, coefficient values K1 = 0.6, K2 = 0.5, and set values s = 0.85, a = 1.70, the output of the black plate data memory 3 is 0.80, subtracted as shown in Fig. 2 (b). The output of vessel 5 is
0.85, the output of the subtractor 6 is 0.80, and the output of the subtractor 7 is 0.75.

Since the output of the black ink data memory 3 is larger than the set value s, the black ink recording signal has a density of 1.70 and the yellow, magenta, and cyan recording signals all have a density of 0, as shown in FIG. Therefore, recording is performed with one color of black plate, and there is no deviation of the four colors during recording.
Even images with many lines such as characters can be recorded clearly.

In addition, in the case where the density of the three colors is set to 0 and the recording is performed only with the black plate as described above, the original image is visually close to black and it is difficult to distinguish the components of the three colors. There is no real harm, and black characters and line drawings can be recorded clearly.

EFFECTS OF THE INVENTION The present invention is a comparison means for comparing the density indicated by a black plate recording signal with a set density, and when the density indicated by a black plate recording signal is larger than a set value, the recording signal is converted into a signal of black plate only. When the input signal is close to true black, recording is performed only with the black plate recording signal, so that the four colors are not displaced and clear recording can be performed.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a multicolor recording apparatus in one embodiment of the present invention, FIG. 2 (a) is a graph showing the state of the same input signal, and FIG. 2 (b) is a graph showing the state of the same recording signal. 2 (c) is a graph showing the state of the recording signal after the correction, FIG.
FIG. 4 is a circuit diagram of a conventional multi-color recording device, FIG. 4 is a graph showing the relationship between the same input signal and each coefficient, FIG. 5 (a) is a graph showing the state of the same input signal, and FIG. 5 (b). Is a graph showing the state of the same recording signal, and FIG. 5 (c) is a plan view showing the same recording state. 1 ... Comparator 2 ... Multiplexer 3 ... Black plate data memory 4 ... Undercolor removal data memory 5-7 ... Subtractor 8 ... Comparator 9-12 ... Multiplexer

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Claims (1)

[Claims] 1. A black plate recording signal generating means for obtaining a black plate recording signal from input signals of three primary colors, and three colors for generating a three color recording signal by removing the undercolor from the input signal and removing the undercolor. A recording signal generating means, a comparing means for comparing the density indicated by the black plate recording signal with a set density, and a case where the density indicated by the black plate recording signal is smaller than a set value. A color recording signal is output as it is, and when the density indicated by the black plate recording signal is larger than a set value, the recording signal is converted into a black plate-only signal and output, and recording is performed according to the output of the converting unit. A multicolor recording device characterized by.