JPH01255543A - Color compensator for color printer - Google Patents

Abstract

PURPOSE:To enable color reproduction accurate to an input signal by providing a color printer device obtaining a hard copy while using a video signal as an input with a means compensating the color purity of ink and a means previously compensating density change after superposition photographic printing. CONSTITUTION:The still picture R, G, B each signal of inputs is changed into digital data by A/Ds 111, 112, 113, and complementary color converted by complementary-color conversion means 121, 122, 123 and turned into each density data of yellow (Ye), magenta (Mg) and cyan (Cy), and input to a masking means 1. The density data of Ye, Mg and Cy simultaneously input are superposed to image sensing paper and photographically printed at that time. Density reduction by re-sublimation is compensated by a re-sublimation compensation means 2 in density data, the purity of ink of which is compensated by the masking means, and the density data are transmitted over a changeover switch 3. Compensated density data are selected by the switch 3, converted into conduction pulses corresponding to ink discriminated by input data, an output from a temperature detecting means 8 and an ink discriminating means 9 by a middle tone control means 4, and transferred to a heatsensitive head 5 and photographically printed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color printer device that receives a video signal as an input and produces a hard copy, and particularly relates to a color correction device for a color printer that enables faithful color reproduction.

[Conventional technology]

In recent years, video printers that obtain television signals and other video signals as hard copies, ie, printed matter such as paper, have been put into practical use. Then, the color video signal is
Efforts are being made to print with good color reproducibility.

Conventional devices of this type convert video signals into digital signals and control the current pulses of the thermal head, as described in Journal of the Institute of Image Electronics Engineers, Vol. 12, No. 1 (1983), pages 18 to 23. Color print output is obtained by sequentially switching colors and performing overlapping printing.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, there is a problem that color purity is lowered due to imperfections in the printing ink, and color density changes after overprinting due to the order of printing colors, resulting in insufficient color reproducibility.

Here, correction of color purity means that, for example, when a print made with yellow ink alone on receiver paper is measured with a printing densitometer, the density of other unnecessary components such as magenta and cyan is included in addition to the density of yellow. Therefore, I would like to correct this.

In addition, density changes after overprinting mean that in devices that use sublimation ink, for example, if the first color of yellow ink is printed at a certain value and then the second color of magenta ink is printed, the yellow ink that was printed first decreases. say what you do A similar thing occurs when printing with the third color, cyan ink, and the amount of yellow and magenta ink decreases, resulting in a decrease in density. This density change is caused by the ink sublimating from the ink sheet and adsorbed onto the receiver paper during printing, sublimated again from the receiver paper due to the heat generated during printing of the next color, reducing the amount of ink remaining on the receiver paper. It is for the sake of
Hereinafter, this phenomenon of sublimable ink will be referred to as density reduction due to re-sublimation or simply re-sublimation.

SUMMARY OF THE INVENTION An object of the present invention is to provide a color correction device for a color printer that follows a signal processing method that takes into account the characteristics of printing ink, in order to realize a video printer with good color reproducibility.

[Means to solve the problem]

The above object is achieved by newly providing the color printer with means for correcting the color purity of ink and means for pre-correcting density changes after overprinting.

[Effect]

The ink color purity correction means performs color correction so that the sum of each component of all the inks printed overlappingly on a certain pixel substantially corresponds to the input signal.

Further, the correction means for density changes due to overprinting performs density correction by predicting density changes in advance and printing with higher or lower density.

These corrections can significantly improve the color reproducibility of color printers using sublimation inks, other wax inks, and the like.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a first embodiment of the present invention.
03, 102, 101 are red (R:Re
d), Green (G: GreenL Blue (B:
Blue) still image video input terminal, 111.112
, 113 is analog-to-digital conversion means (hereinafter referred to as A/
121 is a complementary color conversion means for converting a B signal into a yellow density signal, 122 is a complementary color conversion means for converting a G signal into a magenta density signal, and 123 is a complementary color conversion means for converting an R signal into a cyan density signal. , 1 is a masking means for correcting the purity of the ink, 2 is a re-sublimation correction means for correcting a decrease in density due to re-sublimation, 3 is a changeover switch for printing sequentially in color planes, and 4 is a halftone. 5 is a thermal head;
6 is a system controller, 7 is a print mechanism,
8 is a temperature detection means, and 9 is an ink type identification means.

Next, the operation will be explained.

The input still image R, G, and B signals are A/Dll.

112 and 113, it is converted into digital data by complementary color conversion means 121, 122, and 123, and is converted into yellow (Ye), magenta (Mg), and cyan (Cy).
are each density data, and are input to the masking means 1. Since normal R, G, and B video signals are subjected to cathode ray tube gamma correction, the complementary color conversion means also performs the inverse correction. At this time, Ye, Mg, C) input at the same time
The density data ' is printed in an overlapping manner at the same location on the image-receiving paper.

The density data for the three colors, on which the ink purity has been corrected by the masking means, is corrected for density reduction due to re-sublimation by the re-sublimation correction means 2, and then enters the changeover switch 3.

The system controller 6 outputs a color selection signal in synchronization with the control signal given to the print mechanism 7. The corrected density data is selected by the switch 3, converted into the input data by the halftone control means 4, the output of the temperature detection means 8, and an energization pulse suitable for the ink identified by the ink identification means 9, and transferred to the thermal head 5. and printed.

The color printing method includes three color ink methods (yellow,
There are four-color ink methods (magenta, cyan), four-color ink methods (three-color ink black), etc., and below, an example will be described in which the three-color ink method is used to print yellow first, then magenta, and finally cyan. However, the ink identifying means 9 allows switching between three-color and four-color ink systems, switching the printing color order, and dealing with different inks such as sensitivity and one hue.

Next, the masking means, which is the ink purity correction means, will be explained.

FIG. 3 is a schematic diagram for explaining re-sublimation correction,
The same figure (al is a schematic representation of each of the three colors of ink, and the same figure (bl is an overlapping print. Generally, when measuring a single-color print sample of yellow ink, there is a certain percentage of magenta in addition to the yellow density. .

Cyan density can be measured. The same thing can be said for magenta ink and cyan ink, and the original component of the ink is called the main component concentration, and the other two components are called the unnecessary component concentration. here,
For the purpose of explanation, the symbol conventions are determined as follows.

Main component density of yellow ink (=yellow density) is YY
, colors are shown in uppercase letters, and ink names are shown in lowercase letters, such as MY for magenta density and CV for cyan density among unnecessary component concentrations. Using this, the three colors of ink can be expressed as follows.

The yellow component density after three-color printing is yellow component YY of yellow ink + yellow component Y9 of magenta ink
．． Yellow component Yc of cyan ink.

It is thought that it is the sum of The same thing can be said about magenta component density and cyan component density.

Yall +yxc+ yellow component density after 3-color printing
MalLys % magenta component concentration. , if the cyan component concentration is Ca1l (YMCI).

By using this inverse matrix N-1, each density component (Yall tvsc+
+Mall (YMC) l Ca1l (vsc
+) The amount of each ink that achieves this can be expressed in terms of the respective principal component concentrations (YvlMN, CC) as follows.

Next, an example of the ink characteristic N and its inverse matrix N −1 is shown below.

Next, an example of the masking means shown in FIG. 1 will be explained.

FIG. 2 is a block diagram illustrating an example of a masking means, in which Y input to input terminals 10, 11, and 12, respectively.
e, M g+Cy concentration value and inverter 13.1
4. Apply each inverted value created in step 15 to coefficient units 16 to 24.
In addition to the coefficient multiplication adders 25 to 27, the masked Y
Connect the concentration value of e, M g+ C3' to terminal 28.2
Get it at 9.30. Here, the coefficients i, to n33 correspond to each term of the matrix N-1 explained in FIG. Further, by setting coefficients corresponding to the ink to be used in the coefficient units 16 to 24 using an ink identification signal applied to the input terminal 31, it is possible to deal with inks having different characteristics and improving the performance of the ink.

Next, the density change (re-sublimation) and its correction during overlapping printing of sublimable ink will be explained using FIGS. 3, 4, and 5 again.

3, 4, and 5 are schematic diagrams for explaining resublimation correction, and FIG. 3 shows the output of the masking means in yellow,
This is a schematic diagram of an ideal print for each magenta and cyan ink, including the main components and unnecessary components, and the density measurement value when printed in a single color without overlapping each is expressed as an area ( It can be considered as a). When these are overlapped, ideally it will look like the figure (bl), and the sum of the same color components of each ink will be the density after the overprinting.However, when actually overlapping printing is performed, the third It is not as shown in the figure, but as shown in the schematic diagram of an actual print shown in Figure 4, the yellow ink that was initially printed decreases both the main components and unnecessary components at the same rate, and the same is true for the magenta ink. A decrease in concentration is observed. That is, in reality, the purity correction using equation (4) alone is insufficient.

As mentioned earlier, this can be expressed as the concentration change due to re-sublimation (f
However, re-sublimation naturally does not occur in the ink (cyan ink in this case) that is printed in an overlapping manner at the end.

Re-sublimation occurs because the ink that has been adsorbed to the image receiving paper is sublimated from the image receiving paper to the ink film or even into the air due to the heat energy applied when printing the next color. Conceivable. Therefore, the amount of density reduction due to re-sublimation changes depending on the amount of ink that is later printed over the same pixel. Furthermore, the ratio of the main component to the unnecessary component in the ink remains constant even after resublimation, so if the relational expression of the density change due to resublimation is expressed using the concentration of the main component, it will be as shown in the following equation.

Cc <vsc> = CC(C)
−(8) M□vxc+ = MM (MC)
-(9)=f(Ms+.>-a's YY(YMC)=g'CYv<v>+MF4(M)
+ Cc<c)")-・αυ Here, the subscript in parentheses indicates how many colors (how many types) of ink were printed in layers. For example, Yy (y, 4c+ means 3 colors were printed in layers) CC (C1 is the CvfM degree when only cyan ink is printed).

That is, resublimation relates to inks that are printed after that ink, and not to inks that have already been printed. Therefore, re-sublimation does not occur with cyan ink,
With magenta ink, only resublimation occurs due to cyan ink printing.

Moreover, FIG. 5 is a schematic diagram showing the state of re-sublimation correction. When printing yellow ink, the amount of re-sublimation of yellow ink is predicted from the printing density of magenta ink and cyan ink that will be printed later. Printing is performed by correcting the amount of yellow ink so that it is larger than in the ideal case without re-sublimation (FIG. 3). Similarly, magenta ink is printed in an amount equal to the amount of cyan ink printed to allow for re-sublimation. When these three colors are printed in a superimposed manner, the same density as the ideal superimposed print is recorded in the printed print due to the density reduction due to re-sublimation.

An approximate expression of the relational expression for concentration change obtained through experiments is shown below.

CC(YMC) = CC(c)
...-@YY(Y) Y v (Y+ Y y (v+aa) According to experiments, for sublimation ink, 0≦α<2.0.0≦β<2.0.0≦r<2.0 , α=β=γ−〇, it is an ideal ink without re-sublimation.

The correction can be made by inverse calculation of α(0 to 0), and in the above example, it is as follows.

CC (C) = CC (C to Y)
'--'Α -turning YV (V, the first color of the tm η η η η η η （（（（て
Mo on top of that. If you overlap and print CC (C), then Yall (vHc+ = Yv <vI4c+ +
YN (vnc+ + Y c <v14c+Mail
+v, 4c> = Mv (v, 4c+ + MM
(vsc> + Mc (vsc+Ca1l (YMC
) ” CY(YMCI + CM(YMC) + C
C(YMC)-111~--α remains as a printing result with a density of odor.

In addition, Yall (yMC), Mall (
YMC), Ca1l, vMc+ are (2) to (4)
The value in the formula differs by the amount due to resublimation.

FIG. 6 is a block diagram showing an example of the re-sublimation correction means in FIG. 1, in which yellow and magenta whose purity has been corrected are input from the connection terminals 2B and 29.30.

Each density signal of cyan is generated by an address generation circuit 304゜30.
5. ROM table 309 configured with read-only memory (ROM) becomes an address corresponding to the density at 306.
is input. At this time, the data of the ink characteristics identified by the ink identifying means 9 (FIG. 1) is sent to the address generating circuit 308.
Since the data are added to the ROM table 309 via the ROM table 309, the density values of yellow, magenta, and cyan corrected for changes in obstinacy due to re-sublimation are output to the output terminals 310, 311, and 312. This ROM table 309 stores in advance the data explained using the above-mentioned sub-αη formulas for the types of ink having different characteristics. In this method, all data is stored in the ROM table 309, so the operation is fast, and the designer can modify the data to perform re-sublimation correction with higher fidelity. Characteristic color reproduction is also possible by rewriting the data.

Further, if the contents of the ROM table of this embodiment are as shown in FIG. 1 and include purity correction by the masking means 1, the masking means 1 can be omitted.

FIG. 7 is a block diagram showing a second embodiment of the present invention, and shows a configuration diagram of a video printer in which purity correction and re-sublimation correction by masking are performed using a ROM table. In this figure, the same parts as in FIG. 1 are given the same reference numerals.

In the configuration shown in Figure 7 described above, the purity correction and re-sublimation correction are as follows.
Since this configuration uses data stored in the ROM table 309, it is possible to obtain the same effects as in FIG. 1 with a simple configuration.

FIG. 8 is a block diagram showing a third embodiment of the present invention, in which three colors (
R, G, B) still image video signals are processed by an A/D converter,
112 and 113, the data is digitally converted into density data by complementary color conversion means 121, 122, and 123, and is input to the density control means 10. The density control means 10 performs purity correction by masking using equation (4) described above, re-sublimation correction using equation (8) to alpha processing, color switching corresponding to printing color order,
Halftone control is performed to convert density data into energization time, and energization pulse control to the thermal head 5 is performed. Since these are all performed by calculating digital values, the concentration control means 10
can be constructed using a microcomputer, a digital signal processor (DSP), etc., which have been developed in recent years. When a microcomputer is used, it is possible to incorporate the functions of the system controller 6, which has the advantage of simplifying the system configuration.

FIG. 9 is a block diagram showing a fourth embodiment of the present invention, and shows an example of a configuration based on analog signal processing.

In the same figure, the R, G, and B signals input to input terminals 101, 102, and 103 are normally subjected to γ correction to the power of 0.45 in order to correct the γ characteristics of the cathode ray tube. Inverse γ correction circuit 901, 9 with inverse characteristic 2.2 power
02.903, the signal is corrected to be proportional to the amount of light emitted from the cathode ray tube. Also, since the amount of light is proportional to the reflectance, the relationship between density and reflectance is density = log(1/reflectance> ----
--- One piece is density = log (1/R, G, B light amount > ---
---(It will be 2m.

Therefore, logarithmic conversion means (log conversion means) 904゜90
The R, G, and B signals supplied to 5.906 are converted into cyan, magenta, and yellow signals, and then sent to amplifiers 907 and 908.
, 909, an inverting amplifier 910, 911, 912, and a coefficient multiplier 913, 914, 915. Ink purity correction is performed by a matrix circuit having the characteristics shown in equation (5) above, and an analog calculator 916, 917 performs the ink purity correction. In the re-sublimation correction circuit configured, re-sublimation correction as shown in the equations (transformation) to θD is performed, and the result is input to the switch 919. The system controller 6 sequentially switches the switch 919 while controlling the print mechanism 7 . The switched density signal is converted into digital data by the A/D converter 920, and is sent by the halftone control section 4 to the thermal head 5 as an energization pulse appropriate for the ink and temperature used, and is printed.

Further, by using the output of the ink identifying means 9, the coefficients of the coefficient units 913, 914 and 915 which provide ink purity correction coefficients and the characteristics of the re-sublimation correction can be changed to accommodate various types of ink.

FIG. 10 is a block diagram showing a fifth embodiment of the present invention, and shows an embodiment with a simplified configuration focusing on gray balance.

In the same figure, R, G, and B signals applied to input terminals 101, 102, and 103 are transmitted to amplifiers 801, 802, and 80.
3. Inverting amplifiers 804, 805, 806, coefficient unit 8
07, 809, 810, and buffer amplifier 811,
A matrix circuit consisting of 812 and 813 corrects the purity of the ink, and a selector 814 selects one color according to the printing order and inputs it to an A/D converter 815 to become digital data. This digital data is converted into complementary color data by the complementary color converting means 816, converted into an energizing pulse by the halftone control means 817, and inputted to the thermal head. Halftone control means 81
In 7, the input data is yellow data, magenta data,
The energizing time is controlled so that the printing result is achromatic when all three cyan data are equal. This is possible by adding the results obtained by solving equations (8) to αa only for the achromatic color input to the halftone control means as the gray balance table 818. For a gray balance table, in the case of a 3-color print with 64 gradations for each color,
It is sufficient to have 64×3=192 data, and if this table is configured with corresponding energization times, it can be used as it is as a lookup table for halftone control.

In this embodiment, ink purity correction can be performed correctly, but re-sublimation correction can be performed correctly only for achromatic color input. Therefore, there is no improvement in color reproducibility in areas with high color saturation, but if the reproducibility of achromatic colors is good, color reproduction will be improved in areas with light colors.

Although this embodiment has less correction effect than the first to fourth embodiments described above, it is suitable for a simple system because the color correction intended by the present invention can be achieved with a very simple configuration.

Since the present invention is a color correction device for a color printer using three or four color inks, in addition to video signal input as in each of the above embodiments, digital data such as computer graphic output is input. It can also be used as a color correction device for printers.

In addition, although sublimation ink has been explained above, when a heat-melting wax ink is used, unlike the above-mentioned sublimation ink, when the same ink is used for the first color, and when the second color is used,
When a color is used, the density becomes lower, and the density of the first color ink does not change.

However, the correction can be performed with the same configuration as when using sublimation ink by simply changing the correction coefficient and sign.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to correct the color purity of the ink used and density changes due to overlapping printing, and to enable color reproduction that is faithful to the input signal, resulting in always high fidelity. You can get prints with color reproduction,
It is possible to provide a color correction device for a color printer that has excellent functions except for the problems of the prior art.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing a first embodiment of the present invention, Fig. 2 is a block diagram showing an example of a masking means, and Figs. 3, 4, and 5 are resublimation. A schematic diagram for explaining the correction, FIG. 6 is a configuration diagram showing an example of a re-sublimation correction means, FIG. 7 is a block diagram showing a second embodiment of the present invention, and FIG. 8 is a third embodiment of the present invention. FIG. 9 is a block diagram showing a fourth embodiment of the present invention, and FIG. 10 is a block diagram showing a fifth embodiment of the present invention. 1 ------- Masking means, 2 -------...
Re-sublimation correction means, 4--halftone control means, 5-...
・-Thermal head, 7...-1 Print mechanism, 8-
-------Temperature detection means, 9---Ink identification means, 10---Concentration control means, 309--
---ROM table, 901 to 903----
Inverse T correction means, 904 to 906 --- logarithmic conversion means, 818 --- gray balance table. Agent Patent Attorney 2 Sequential Department (1 other person) Rat, So
P Fig. 2 RI Σ r Fig. 6 N l'J () Q 0

Claims (1)

[Claims] 1. Analog/digital conversion means, and complementary color conversion means for converting the primary colors red, green, and blue into three colors, yellow, magenta, and cyan, or four colors, yellow, magenta, cyan, and black. , a color correction device for a color printer having a halftone control means for controlling the color density of ink, and a masking means for correcting the component ratio of the complementary color signal, and a density correction means for increasing/decreasing the complementary color signal; A color correction device for a color printer, characterized in that it is configured to enable color reproduction. 2. The color correction device for a color printer according to claim 1, wherein a table using a read-only memory is provided as the masking means and the density correction means. 3. The color correction device for a color printer according to claim 1, wherein the masking means and the density correction means are microcomputers. 4. The color correction device for a color printer according to claim 1, wherein the masking means and the density correction means are used on the input side of the analog/digital conversion means. 5. The color correction device for a color printer according to claim 1, wherein the masking means is provided on the input side of the analog/digital converter, and the density correction means is provided on the output side of the analog/digital converter. Color correction device for color printers. 6. The color correction device for a color printer according to claim 1, wherein the density correction means is configured to adjust the density of the first color and the second color when printing three colors.
A color for a color printer, characterized by having a configuration that controls color so that when printing four colors, each of the first, second, and third colors has a higher density than when printing a single color. correction device. 7. In the color correction device for a color printer according to claim 1, the density correction means controls the second color and the third color when printing three colors, and the second color, third color, and third color when printing four colors. A color correction device for a color printer, characterized in that the color correction device for a color printer is configured to control the fourth color so that the density thereof is lower than when printing a single color.