JPH0332263B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a color printer that records a color image by forming pixels by a collection of color dots produced by inkjet or electrophotography.

<Prior art> Generally, when color reproduction is performed using a color printer using inkjet or electrophotography, a minimum of three color dots, namely cyan (C), magenta (M), and yellow (Y) color dots, are used. It is necessary to use
Also, when reproducing intermediate colors for those colors,
In order to reliably reproduce these intermediate colors, the dot configuration is determined by determining the number of dots recorded in a unit area as a pixel, as shown sequentially in Figures 1 to 12. Many methods are used to reproduce intermediate colors. However, even in such intermediate color reproduction methods, the actual color tones vary depending on the relative positional relationship of dots of each color on the recording paper. For example, as shown in Figures 2 a to c, the relative positional relationship of magenta (M) and cyan (C) dots is different, and when the ratio of the overlapping portion changes, a difference occurs in the tone of the intermediate color. . Therefore, it is necessary to record the square color dots so that the relative positions on the recording paper of the square color dots that make up the pixels are almost the same, but the recording positions of the dots must be adjusted to such an extent that the difference in tone between intermediate colors is not noticeable. In order to control the recording position, it is necessary to determine the recording position with an accuracy of within several microns, which is difficult to implement in reality. In order to overcome this difficulty, the overlapping of each color dot is changed periodically by angularizing each dot configuration, and by averaging the periodic changes, it is visually possible to visually distinguish the same configuration. Conventionally, a so-called screen processing method has been adopted in which color dots are combined to produce intermediate colors of the same tone.

<Problems to be Solved by the Invention> The conventional method used in general plate making machines to control the screen angle is to use a film called lithium film and expose the film at an angle to achieve optical control. However, such optical screen angle control is not applicable to color printers that require electronic screen angle generation; This method could not be used in color printers that perform screen angle control and reproduce color images.

Also, devices are known that generate dots in accordance with color image signals applied to plate-making machines, but such devices have complex structures and are not simple enough to be used in color printers. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a color printer which eliminates the above-mentioned drawbacks of the conventional printer and which allows screen angle control of yellow, magenta and cyan dots with an extremely simple configuration.

<Means for Solving the Problems> In order to achieve the above-mentioned object, the color printer of the present invention includes a color image forming section that forms a color image by superimposing dots of at least cyan, magenta, and yellow colors; synchronization signal generating means for generating a synchronization signal synchronized with the image forming operation of the color image forming section;
A counting means for counting dots of each color of yellow according to the synchronization signal, the counting means having a different counting state for at least one of the cyan, magenta, and yellow, and a counting result of the counting means. dot data generation for generating dot data with a screen angle different from the others for at least one of the cyan, magenta, and yellow according to the given cyan, magenta, and yellow image data, and applying the dot data to the color image forming section; means.

<Example> First, FIG. 3 shows an example of the configuration of an image processing apparatus that implements the method of the present invention. In the illustrated configuration, 1 is an output device using inkjet, electrophotography, etc., which generates _a pulse signal and generates a pulse signal Y ₁ every time it moves by a distance of one dot in the Y direction, and further generates a pulse signal C ₃ ,
It is assumed that when M ₃ , Y ₃ , and K are supplied, dots of each color of cyan, magenta, yellow, and black are recorded at the recording position at that time. 2
is an input device using an image sensor or the like, and each time pulse signals X ₂ and Y ₂ are supplied, signals C ₁ , M ₁ , and Y ₁ of density data to be recorded that have undergone color correction are output. shall be taken as a thing. Next, 3 is a counter that uses, for example, a 4-ary system, and when four pulse signals X ₁ are supplied, it generates _a pulse _signal It is assumed that a pulse signal Y ₂ is generated when four are supplied. Further, both 5 and 6 and 7 and 8 are counters in hexadecimal format, for example, and when 17 pulse signals X ₁ and Y ₁ are supplied, respectively, the data signal XC is output as a count output.
and generate YC as well as XM and YM.
Furthermore, both 9 and 10 are counters in, for example, four digits, and when four pulse signals X ₁ and Y ₁ are supplied, respectively, they generate data signals XY and YY as count outputs. 11,
12 and 13 are both read-only memories (ROM), of which ROM 11 receives the data signal C ₁ from the input device 2 and the counters 5 and 6.
The ROM 12 uses _the data signals XC and YC from the input device 2 as addresses to output a signal _C2 indicating whether to record cyan dots at the current recording position. The ROM 12 outputs a signal _M2 indicating whether or not to record a magenta dot at the current recording position using the signals XM and YM as addresses.
Using the data signal _Y1 from the input device 2 and the data signals XY, YY from the counters 9 and 10 as addresses, a signal _Y2 is output indicating whether or not to record a yellow dot at the current recording position. 14 is a black processing circuit, which outputs output signals C 3 and C ₃ according to input signals C ₂ , M ₂ and Y ₂ from ROMs 11, 12 and 13;
M ₃ , Y ₃ and K are supplied to the output device 1 .

Next, FIGS. 4 and 5 show examples of the data storage mode within the ROM 11 in which control data for recording of the digital dots is stored. Here, FIG. 4 shows the mode of data storage when the cyan density data signal C ₁ from the input device 2 is 4.
Further, FIG. 5 shows the mode of data storage when C ₁ =8. In such a storage state, the counters 5,
When address/data signals XC and YC are supplied from 6, if the address is in the shaded area in FIGS. 4 and 5, the signal C ₂ =1 is output, and If it is not the area where the image has been applied, a signal C ₂ =0 is output to instruct control to record 4 or 8 cyan dots in the form of the hatched area, or not to record them. Note that the ROM 12 and ROM 13 are also instructed to control the recording of magenta and yellow dots, respectively, using patterns that are somewhat different from those shown.

In this example, cyan, magenta,
Among the yellows, cyan and magenta are processed to obtain diagonal screen angles, and yellow is processed so that dots are arranged in a grid pattern.

Therefore, for cyan and magenta, unlike for yellow, the count value of the counter is set to a large value, and as shown in Figures 4 and 5, one pixel of the printer is 17 pixels in the vertical direction. There are 17 dots lined up horizontally, and the dots line up at angles other than 90° to form the screen angle.

For yellow, it is enough to arrange the dots in a grid pattern, so one pixel of the printer is arranged vertically, four times horizontally, and the dots are arranged at a 90° angle to form the screen angle. .

An example of a pattern when the recording control data signal of each color dot pattern as described above is output and each color dot pattern overlaps on the recording paper is shown as each color density data signal C ₁ = 4, M ₁ = 4, Y ₁ = FIG. 6 shows the case of 4. Here, △ indicates cyan dot C, × indicates magenta dot M, and ○ indicates yellow dot Y.

Next, control data signals C ₂ ,
An example of the configuration of the black processing circuit 14 that supplies M ₂ and Y ₂ is shown in FIG. In the illustrated configuration, each input control data signal C ₂ , M ₂ , Y ₂ is connected to an AND circuit 1.
5, 16, and 17, and is also commonly supplied to the other AND circuit 18 to make the output of the AND circuit 18 a black K, that is, a black dot recording signal, and the black dot recording signal K. through the inverter 19 to each AND circuit 15, 16,
It is commonly supplied to the other input terminal of 17. Therefore, as shown in FIG. 8, each input control data signal C ₂ , M ₂ ,
Only when Y ₂ is all 1, that is, when recording is to be performed, the black dot recording signal K becomes 1, and at the same time, each color dot recording signal C ₃ , M ₃ , Y ₃ all becomes 0, and a black dot appears on the recording paper. Only the dot is recorded, and all other color dots are not recorded. In other cases, each input control data signal C ₂ , M ₂ ,
When only one or two of Y ₂ are 1, these input control data signals are used as they are as dot recording signals C ₃ , M ₃ , and Y ₃ of each color, and at the same time, the black dot recording signal K is set to 0. FIG. 9 shows an example of a pattern resulting from processing by the black processing circuit 14 having such a configuration. Here, C ₁ =4, M ₁ =4, Y ₁ =4
, cyan dot C is △, magenta dot M
The yellow dots Y are indicated by ×, and the yellow dots Y by ○. Blocks a, b, and c shown as diagonal lines in the illustrated pattern indicate areas where dots C, M, and Y of each color are all recorded in an overlapping manner, and black should be produced by subtractive color mixing. does not record black by subtractive color mixture, but records black dots with true black ink, and each color dot C, M, Y
will not be recorded at all.

In the embodiments described above, at least cyan,
A color image forming section that forms a color image by superimposing dots of each color of magenta and yellow corresponds to the output device 1, and a synchronization signal generating means that generates a synchronization signal synchronized with the image forming operation of the color image forming section is Similarly, the head position signal is output from output device 1.
It corresponds to a means for outputting X ₁ and Y ₁ , and the cyan,
Counters 5, 6, and 7 are means for counting dots of each color of magenta and yellow according to the synchronization signal, and the counting means has a different counting state for at least one of cyan, magenta, and yellow. ,8,9,10,
According to the counting result of the counting means and the given image data of cyan, magenta, and yellow, dot data of a different screen angle for at least one of the cyan, magenta, and yellow is generated and applied to the color image forming section. The dot data generating means corresponding to the ROMs 11, 12, and 13 also correspond to the ROMs 11, 12, and 13, respectively.

<Effects of the Invention> As is clear from the above description, according to the present invention, screen corner processing that can prevent the occurrence of color unevenness due to differences in the degree of superimposition of dots of each color can be performed much more easily than in the past. This can be realized by the circuit configuration.

[Brief explanation of the drawing]

1 to 16 are diagrams showing examples of halftone reproduction using a dot configuration, FIGS. 2 a to c are diagrams sequentially showing examples of differences in the degree of superimposition of two-color dots, and FIG. FIGS. 4 and 5 are block diagrams showing an example of the configuration of an image processing apparatus according to a method according to an embodiment of the present invention, and FIGS. FIG. 6 is a diagram showing an example of a pattern obtained by superimposing patterns of data stored in each ROM in the same configuration example, and FIG. 7 is a block diagram showing an example of the configuration of the black processing circuit in the same configuration example. FIG. 8 is a diagram showing an example of the correspondence between input and output in the black processing circuit, and FIG. 9 is a diagram showing an example of the image recording mode of the processing result by the black processing circuit. 1...Output device, 2...Input device, 3-10...
...Counter, 11-13...ROM, 14...Black processing circuit, 15-18...AND circuit, 19...
inverter.

Claims (1)

[Scope of Claims] 1. A color image forming section that forms a color image by superimposing dots of at least cyan, magenta, and yellow colors, and a synchronization device that generates a synchronization signal in synchronization with the image forming operation of the color image forming section. signal generating means; and means for counting each of the cyan, magenta, and yellow color dots according to the synchronization signal, the counting state of at least one of the cyan, magenta, and yellow being different from the others; a counting means; and according to the counting result of the counting means and the given image data of cyan, magenta, and yellow, dot data of a screen angle different from the others for at least one of the cyan, magenta, and yellow is generated. 1. A color printer comprising: dot data generation means for applying to a color image forming section.