JPS59201863A - Reproduction of halftone - Google Patents

Abstract

PURPOSE:To obtain more gradations by selecting a method of enabling a greater number of cells for forming dots when there are two or more kinds of methods of controlling the number of cells for reproducing virtually the same concentration. CONSTITUTION:A head unit 51 has ink jet nozzles 52 in two kinds of density, dark and light, each for black, yellow, magenta and cyan to compose one 3X3 matrix pixel to make the reflectively optical density equal between when four light does are formed for each pixel and when one dense dot is formed for each pixel. Here, for example, the gradation 4 can be expressed by four light dots or one dense dot. But in this manner, when there are more than one methods of controlling the number of cells for reducing virtually the same density, the one of enabling more cells for forming dots, namely, four light dots is selected to drive a printing head. This enables the reproduction of more gradations without increasing the number of cells while eliminating rough looking thereby producing an image of a high quality.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an intermediate station reproduction method that reproduces intermediate tones using a so-called density modulation method that controls the number of dots existing in one pixel. ffK This relates to a method for reproducing halftones using dots having multiple types of densities.

(Prior Art) Conventionally, in a method of reproducing halftones by controlling the number of dots present in a pixel, dots of a single density have been used.

For example, one pixel is made up of a total of nine cells (6 x 5), and one dot is formed in each cell, so it is possible to reproduce a total of 10 gradations, including cases where no dot is formed. be. However, it is difficult to reproduce a high-quality image with 10 gradations. Therefore, increasing the number of cells can be considered, but as the number of cells increases, one pixel becomes larger, resulting in a decrease in resolution.

Also, a method has been proposed to reproduce multiple gradations using a systematic dithering method without increasing the number of cells, but when fc is used using a systematic dithering method, pseudo-patterns are fundamentally generated. Alternatively, there are drawbacks such as a rough surface density in the illite portion, making it impossible to obtain a high-quality image.

(Objective of the Invention) In view of the above-mentioned drawbacks of the prior art, the present invention - makes it possible to obtain a larger number of gradations without increasing the number of cells constituting a pixel, and achieves high quality, especially in highlight areas. The purpose of this invention is to provide a method for reproducing halftones by which images can be obtained.

(Explanation of Example) In this example, in order to achieve the above object, two dots of shading and lightness were used to form a 6×6 matrix-pixel. The sizes of the bright and light dots are equal, and the reflected light-year density obtained by forming four light dots in one pixel is equal to the reflected light-year density obtained by forming one dark dot in one pixel. shall be.

If it is 1-, it becomes possible to reproduce the gradation like the construction method.

In the above table, in order to express the same dark or the same gradation among the gradations from 0 to 6, all combinations where there is a plurality of control methods are highlighted.

Among these, those used for image reproduction in this actual hm example are shown in FIG. In Figure 1, ○ is a light dot, ■
indicates a dark dot.

Here, for example, floor L+,'! 14 can be expressed with four light dots or one dark dot, but in this example, it is expressed with four light dots. In this way, we have selected a control method that maximizes the number of occupied cells within a pixel, so there will be fewer white areas, and especially in highlight areas, light dots will always be selected. ;) Dots will no longer be scattered. That is, the conventional problems such as roughness in image quality are eliminated, and both 17 girls with a soft texture can be obtained.

In this example, for the gradations 31, 34, and 35, the gradations are impossible to reproduce or are in high εA degrees, so there is little shadow change on the image quality, and there is no large impact on the image quality. '1
Images with sufficient linearity can be obtained for low-density areas that give .

The present invention is applicable to a variety of recording methods such as inkjet recording, thermal transfer recording, and electrostatic recording.

Here, an example of use in inkjet recording will be described.

FIG. 2 is a perspective view of the periphery of a head of an inkjet recording apparatus using heating elements.

In the figure, 51 is a head unit having a total of eight nozzles/l 152. That is, the head unit 51 has a high-density black ink discharge nozzle /l152BK, a low-density black ink discharge nozzle 52 BA, and a high-density yellow ink discharge nozzle 52 y.
Two nozzles are provided for each color such as K, black, yellow, macenta, and cyan. 56 is an ink supply tube, 54 is a main tank, and eight main tanks are provided corresponding to each nozzle.

The configuration of the nozzle 52 will be explained using the cross-sectional view of FIG.

55 is a top plate, 56 is a bottom plate, 57 is a heating element, 58 is an orifice portion, and 59 is ink.

When a voltage is applied to the heating element 57, heat is generated, a bubble is formed around the element 570, and when the voltage application ends, the bubble contracts. As the bubbles are formed and contracted, the ink near the -C orifice portion 58 is ejected from the orifice 58.

Next, the following operation will be explained with reference to a block diagram of a 1IILJ blotter using the inkjet head shown in FIG.

A video signal vS including R, G, and B color numbers and a synchronizing signal is inputted to the f-face 61.

The interface 61 performs gamma conversion two-color correction of each color signal as necessary, and then performs sample and hold using an internal sample and hold circuit using a synchronizing signal. Each sample bold color signal is converted into a digital signal by an AD transition circuit 62, and the digital color signal is sent to a line memory 6.
At 6, the appropriate number of inputs is memorized.

Next, the data in line memory 6 is processed by the image processing circuit for each pixel, including color conversion, γ conversion, masking processing, undercolor removal, etc. Generally, the recorded colors are cyan, magenta, yellow, and black. converted into a signal. The recorded color signal is a digital signal of several bits representing gradation, and the recorded color signal is input to a pattern generator 72 that generates a pattern as shown in FIG. 1, and a pattern corresponding to the input digital value is input. A signal is output. The pattern signal is input to the head driver 66, and the driver 66 operates the head 69 corresponding to the heating element 57 shown in FIG.

On the other hand, the system controller 65, which controls the sequence of the 7' link, generates a head driver No. 8 and a carriage morph drive signal 2 paper feed signal at a timing corresponding to the input video signal VS, and the head driver 66 and carriage morph drive signal 2 are generated at a timing corresponding to the input video signal VS. motor driver 67,
The paper is supplied to the paper feed motor driver 68, and the inkjet head 69 and carriage motor 7 are
The 0° paper feed motor 11 is controlled to print the reproduced image of the input video signal on the recording medium.

In this embodiment, an inkjet recording device using bubbles has been described as an example, but an inkjet recording device using electromechanical conversion means such as a piezo element is also applicable.

(Explanation of Effects) As explained above, according to the present invention, it is possible not only to reproduce multiple gradations without increasing the number of cells constituting one pixel, but also to make it possible to reproduce large dots in highlighted areas. Since no grains are formed, it is possible to obtain images that have no rough texture and are of much higher quality.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the dot pattern at each gradation.
1's2 is a perspective view of the vicinity of the head of the inkjet recording apparatus, FIG. 3 is a sectional view of the nozzle 52, and FIG. 4 is a control block diagram of the inkjet recording apparatus. Applicant Canon Co., Ltd.

Claims (1)

[Claims] ``eJ, dots with several types of densities are formed.One pixel consisting of a plurality of cells is set, and halftones are reproduced by controlling the number of cells in which each dot of different densities is formed in the one pixel. In the intermediate station reproduction method,
When there are two or more ways to control the number of cells to reproduce the same concentration,