JPS5972869A - Masking processing method of color picture producing device - Google Patents

Abstract

PURPOSE:To perform the masking processing without using a large capacity memory, by adding and subtracting a digital signal deciding the quantity of another color material to a digital signal deciding the color of the 1st color material with a shift of a prescribed number of bits. CONSTITUTION:The signals S2 and S3 of those Y (yellow), M (magenta) and C (cyan) signals S1-S3 of 8 bits respectively which are fed to registers 1-3 are shifted by shift signals S10 and S11 in accordance with masking coefficients Ym and Yc. The output signal S4 of the signal S1 of the register 1 which has no shift is applied to a subtractor together with signal outputs S5 and S6 and then supplied to a register 5 in the form of a subtraction signal S7. The output of the register 5 is turned into an yellow signal which underwent a masking correction. Thus it is possible to perform the masking processing without using a large capacity memory.

Description

TECHNICAL FIELD The present invention relates to a masking processing method in a color image forming apparatus, and more particularly to a masking processing method for removing intermediate tones during subtractive color mixing based on deviations in spectral characteristics of complementary color materials. It is something.

BACKGROUND TECHNOLOGY Conventionally, in a color image forming apparatus 1 that uses an electrophotographic process, one image is
The colors are separated into colors (B (blue), G (green), R (red)), a latent image is formed for each color, and a complementary color developer (Y (
Yellow) 0M (magenta) and C (cyan)) were developed and multicolor superimposition was performed to reproduce a color image.

Since each of the Y, M, and C toners used as the developer has color turbidity, a shift in intermediate tone may occur during mixing.

In an apparatus that performs image signal processing using digital signals, it is possible to correct this color shift by performing masking electrically.

Mu Here, a description will be given of masking for correcting the shift in intermediate tone when mixing elm colors based on the spectral characteristics of complementary color materials.

In a color image output device using an electrophotographic process, J
Three complementary color signals C, M, and Y are obtained by performing complementary color conversion on the three primary color image signals of red), G (green), and B (blue), and three corrected complementary color signals co are obtained by correcting deviations in the spectral characteristics of each complementary color toner.
9MO1Yo and the masking coefficients between each complementary color are Cm, Cy, rny, rnC, respectively.
, Yrn, and Yc, there is a 5th order function.

Therefore.

Yo=y+YmM+YcC Mo=my Y 1M+me Cco=CyY
10 CmM 10 In actual masking processing, the gradations of each corrected complementary color signal corresponding to 1, for example, 256 gradations to be represented by each complementary color signal are created in advance in a table and stored in a random access memory. A method is known in which three corrected complementary color signals are created by accessing the gradations of each of the complementary color signals Y, M, and C to be recorded and reading out the color tones of the corresponding corrected complementary color signals co1MO1Yo.

However, if such a method is adopted, the size of the table will be 16777216 for each complementary color, for example, if the number of gradations that each complementary color can take is 256, which will require a large capacity memory and require a large device. However, it has the disadvantage of increasing costs.

Purpose The present invention was made in order to eliminate the above-mentioned drawbacks of the conventional art, and an object of the present invention is to provide a masking processing method configured to perform masking without requiring a large capacity memory. There is.

Embodiments Hereinafter, one embodiment of the present invention will be explained in detail based on embodiments shown in the drawings.

FIG. 1 shows an example of a color image forming apparatus using an electrophotographic process to which the method of the present invention can be applied.

The example shown in FIG. 1 is a color laser beam printer including four sets of electrophotographic processes, numbered 10a to 10 in the figure.
d is a scanning optical system that includes a laser oscillator as a light source, a rotating polygon mirror, and an imaging lens.

Process units 11a-lld are provided facing these.

Process units) IZa to Ild are the primary charger 12, the transfer charger 13. It has a cleaner 14 and development units 15a to 15d in order from the right. The developing device 15a is a Y developing device having yellow toner.

15b is an M developer with magenta toner, 15c is a C developer with cyan toner, and 15d is a B developer with black toner. A photosensitive drum 21 is provided surrounded by each of these parts.

Reference numeral 16 denotes a paper feeding roller, 17 a gripper for conveying the paper, 18 a driving chain sprocket, 19 a driven chain sprocket, and 20 a chain for conveying the gripper 17. Reference numeral 22 indicates a fixing device.

Based on the structure described above, the paper is first transferred to paper feed roller 1.
6, the paper is fed toward the gripper 17.

It is gripped and conveyed by chain 20.

When the paper begins to be conveyed, the photosensitive drum 21 is rotating in the process unit la, and each part of the drum surface is charged by the primary charger 12 and exposed by the scanning optical system 10a to form an electrostatic latent image. The toner is developed with yellow toner by the developing device 15a.

Similarly, a similar image forming operation is performed on the process units )llb to 1ldO, and as described above, they are developed with magenta, cyan, and black toners, respectively.

On the other hand, the paper gripped by the gripper 17 is transferred to the drum 2, which has been made into a developed image by the above-mentioned electrophotographic process.
The developed image on the drum 21 is transferred to the paper by the action of the transfer charger 13.

In this way, a color image is formed on the paper.

The paper on which the color image has been formed is released from the gripper 17 near the top of the drive sprocket 18, fixed by the fixing device 22, and then discharged.

FIG. 2 and subsequent drawings explain an embodiment of the control circuit according to the present invention, and show an example in which a modified complementary color signal YO is obtained and the number of gradations is 256.

FIRST EMBODIMENT FIG. 2 is a schematic diagram illustrating the first embodiment of the present invention. In the figure, the number 1 indicates an 8-bit register into which the complementary color signal of yellow is input, and the number 2.3 indicates the register. What is shown is an 8-bit register into which magenta and cyan complementary color signals are input.

4 is an 8-bit subtracter, and 5 is an 8-bit register into which the corrected complementary color signal YO is input.

Further, the symbols 81 to S3 are respectively an 8-bit Y signal, 9 open signal, and a C signal, S4 is a Y signal, and s5.
S6 indicates the M signal and C signal whose bits have been shifted, s7, , S8 are the obtained Yo signals, S9 is the synchronization signal, and 810 and 811 are the shift signals of the shift register 2.3, respectively.

In Fig. 2, Y, M, and C signals s1 are input to registers 1 to 3.
．． 82. When s3 is input, the contents of register 2.3 are shifted to shift signal 810 according to masking coefficient Ym*yc.
, 811.

and unshifted register 1 signal S4.

Signal S5. of shifted register 2.3. S6 is.

The signal is applied to the subtracter 4, and the result is applied to the register 5 as a signal S7.

FIG. 3 shows the contents of the registers in FIG. 2.

In FIG. 3, registers 1 to 3 each have a Y value.

When the M and C signals are input, ym and y are obtained in the above-mentioned formula for determining Y. is 4n (n = O-1.

2...7), y□0M and YcC are M.

The value is the same as the value obtained by shifting the C signal to the L8B side by n bits.

Therefore, after the M and C signals are input to registers 2 and 3, registers 2 and 3 are input according to the value of Ym e Yc.
Shift to the LSB side.

At this time, "0" is assigned to the 1M5B side in the case of positive logic.

For example, ym=44. When yc=148, it is sufficient to shift register 2 by 6 bits and register 3 by 7 bits.

By the way, the masking coefficient generally has a negative sign. When shifting the registers 2 and 3 mentioned above, the process is done based only on the size without considering the sign, so the Y
The formula for determining o must be rewritten as Yo=Y-IymIM 1yclc.

Therefore, by subtracting the contents lym I M and lyc l C of registers 2 and 3 from the contents Y of register l, the value of Yo can be obtained.

Therefore, using subtracter 4 and register 5 (register 5
) = (Register 1) - (Register 2) - (Register 3)
By executing, Yo can be found.

By the way, in the above-mentioned embodiment.

Other values may also be used to approximate boiling.

Further, register 5 may be shared with register 1.

Also, in the process of calculation, YO becomes Y1=Y-1ym l M or Y1=Yl y
c l CYo=Y1- lyc l C or Y
It may be calculated twice by setting O=Y11ym1M1.

Furthermore, 5 to 1. Instead of using the subtracter 4, it is possible to use an adder and add it to the register l using a 2.3's complement to obtain Yo.

In this way, masking can be performed without requiring a large capacity memory.Second EmbodimentFurthermore, FIG. 4 explains the second embodiment of the present invention.
In the figure, numeral 1 is a register into which the complementary color signal Y is input;
Reference numeral 6 indicates a register to which the complementary color signal M is input.

The same value can be used for the masking coefficient as long as there is no change in the staining of each complementary color caused by toners of other complementary colors, that is, as long as the same toner is used.

Therefore, in the embodiment described above, each time Ym is calculated, Ym
, Cm, but instead, register 1 and register 2 can be combined with a value shifted by a predetermined amount to obtain Yo through a subtractor or an adder.

Incidentally, in the above-mentioned embodiment, a color image output device using an electrophotographic process was described, but the present invention can also be applied to other color image output devices such as an inkjet printer and a thermal transfer printer. Of course.

Effect As is clear from the above explanation, according to the present invention, the masking coefficient is set to 6.

This can be done by adding and subtracting with a shift of n bits, and has the excellent effect of being able to perform masking without requiring a large capacity memory.

[Brief explanation of the drawing]

Fig. 1 is a side view of a laser beam printer to which the present invention is applied, Fig. 2 is a block diagram of a control circuit explaining an embodiment of the present invention, and Fig. 3 shows the contents of the register shown in Ki 2 Minami. Explanatory diagram, FIG. 4 is an explanatory diagram showing the contents of a register to explain another embodiment of the present invention. 1~Death...Register 10a~10d...Scanning optical system 11a~lld Middle process unit 12...-Next phase electric device 13...Transfer charger 14
...Cleaner 15a-15d Upper developer 1
6...Paper feed roller 17Gripper 22...Fuser Fig. 2 Fig. 3 Fig. 4

Claims (1)

[Claims] In a color image output device that prints color materials of a plurality of different tones, the amount of other color materials is calculated from a first digital signal that determines the color of the first color material. Masking treatment method for charcoal.