JPH01218838A - Color printer - Google Patents

Abstract

PURPOSE:To improve color reproducibility and to enhance image quality, by mounting a memory storing the relation between several kinds of three-color overlapping ratios capable of being changed over corresponding to a monochromatic color or the overlap of a plurality of colors. CONSTITUTION:NTSC 1 data is inputted to an A/D converter 4 through a decoder 3 while analogue RGB 2 signal is directly inputted to the A/D converter 4 and both data subsequently enter a color converting medium contrast circuit 7 through an RAM 5 and an address control circuit 6. In a gamma-ROM 8, data showing the overlapping ratio of three colors of yellow, cyan and magenta for obtaining a full color print with good color reproducibility is stored and printing is performed according to the content of said ROM 8. Therefore, in the color converting medium contrast circuit 7, it is judged that a monochromatic color used or plural colors are used in an overlapped state or, in the case of plural colors, the combination of plural colors is judged and the gamma-ROM 8 is selected corresponding to the judgement to perform medium contrast color conversion. This data is printed through a head driving apparatus 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color printer, and particularly to a color printer suitable for high-quality recording.

[Conventional technology]

Generally, in order to obtain density gradations with a printer, the power supply time is controlled at a constant voltage, and the relationship between this density and time is known as gamma characteristics.
(Japanese Patent Publication No. 59-17954), conventional color printers have only one type of gamma characteristic for each of the three colors yellow, cyan, and magenta. In other words, the overlapping ratio of the three colors was constant.

Further, as described in Japanese Patent Application Laid-open No. 59-67059, there are some that use different gamma characteristics for full-color printing and color-specific printing. However, this still uses one type of gamma characteristic in one color print, and does not change the overlapping ratio of the three colors.

[Problem to be solved by the invention]

The conventional technique described above has a problem in that when a plurality of colors are superimposed, the density of the color in the lower layer decreases.

In addition, to solve the above problem, if you lower the density of the overlapping color, it will be too light when printing only that color, or if you make the underlying color darker, only that color will be printed. The problem was that it was sometimes too dark.

In this way, if the ratio of overlapping three colors is the same, there is a problem that the balance of color reproducibility is lost between when multiple colors are overlaid and when a single color is used, and the print image quality deteriorates. - An object of the present invention is to provide a color planter that has good one-color reproducibility and can achieve high image quality.

[Means to solve the problem]

The above object is achieved by providing a plurality of memories storing the relationship between one current application time and color density, and selecting one of the memories according to an input signal.

[Effect]

When printing a plurality of colors in an overlapping manner, printing is performed using the overlapping ratio of each color stored in the memory of the color printer according to the color combination. Similarly, when printing in a single color, printing is performed accordingly.

In this way, a single color printer is equipped with a memory that stores the relationship between several types of three-color overlay ratios that can be switched depending on whether printing is performed in a single color or in a combination of multiple colors. As a result, high-quality color prints with good color reproducibility can be obtained.

〔Example〕

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

FIG. 1 shows a block diagram of a sublimation type thermal transfer full color printer employing an embodiment of the present invention.

NTSC (Nation) is the standard television signal in Japan.
alTelevision System Com+m
1ttaa) 1 data via the decoder 3, or analog RGB 2 signals directly to the A/D converter 4. R
AM5. After passing through the address control 6 sequentially, the color conversion halftone circuit 7 is entered. In γ-ROM8, yellow,
cyan.

Information is stored in memory about the ratio of the three colors of magenta to be superimposed to obtain a full-color print with good color reproducibility, and printing is performed according to this information. Therefore, in the color conversion halftone circuit 7, it is determined whether it is a single color, multiple colors are superimposed, or if there are multiple colors, what kind of color combination is used, and γ-R is determined accordingly.
Select OM8 and perform halftone color conversion. This information will be printed via the head drive device 9.

Next, consider the case of a color printer that prints hard copies by overlapping three colors, for example, yellow, cyan, and magenta in that order. As shown in Figure 2, compared to the case of yellow single color A, when magenta or cyan (yellow + magenta B or yellow + cyan C) is layered, both cyan and magenta (yellow + cyan + magenta D) If they are overlapped, the yellow density will be lower.

Therefore, yellow and cyan have the same density gradation level.

If we decide the overlapping ratio of the three colors so that when three colors of magenta are overlaid, it becomes the ideal black, when printing only yellow, it becomes pale and the color reproducibility deteriorates.
It is not possible to obtain good full-color prints.

According to this embodiment, when three colors are superimposed.

When two colors are superimposed or printed in a single color, the density of each color is changed and the relationship is memorized, making it possible to obtain full-color prints with good color reproducibility.

〔Effect of the invention〕

According to the present invention, even if one color is overlapped, the underlying color does not become lighter, and when printed in a single color, it does not become too light or too dark.

It has good color reproducibility and is effective in obtaining color prints with good print quality.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a dye sublimation thermal transfer printer according to an embodiment of the present invention, and FIG. 2 is a graph of yellow color density characteristics. A: Yellow color density characteristics when printing with a single color of yellow, B: Yellow color density characteristics when yellow is layered with magenta, C: Yellow color development when yellow is layered with cyan. Density characteristics, D...Figure 1 when cyan and magenta are layered on yellow.

Claims (1)

[Claims] 1. In a color printer that makes a hard copy of a full-color image on a copying object by superimposing the three colors yellow, cyan, and magenta, when all three colors yellow, cyan, and magenta are superimposed, and when two colors are superimposed,
A color printer characterized in that the density of each color is changed in each case of a single color, and the relationship is stored in memory.